https://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&feed=atom&action=historyBuild a cheap turbofan - Revision history2024-03-29T13:25:14ZRevision history for this page on the wikiMediaWiki 1.40.0https://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=566&oldid=prevVincent: /* Sensors */ GN&C webcast link2015-01-20T01:44:42Z<p><span dir="auto"><span class="autocomment">Sensors: </span> GN&C webcast link</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Sensors===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Sensors===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Engine must be designed with sensors, at least to determine if the engine is running properly or if it's under failure, and to control its rotation speed <del style="font-weight: bold; text-decoration: none;">to ensure it's running at an efficient enough value</del>, <del style="font-weight: bold; text-decoration: none;">with regard to altitude </del>(pressure and temperature). <del style="font-weight: bold; text-decoration: none;">That can be done with a </del>rotation sensor, measuring the magnetic field disturbances created by the blades or the rotor. Engine temperature should be controlled and recorded too. Pressure at different stages would be very useful for engine development, <del style="font-weight: bold; text-decoration: none;">then </del>for <del style="font-weight: bold; text-decoration: none;">behavior indications when running at high altitude</del>. The rotor speed information and altimeter may be redundant with some of the pressure information.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Engine must be designed with sensors, at least to determine if the engine is running properly or if it's under failure, and to control its <ins style="font-weight: bold; text-decoration: none;">fuel flow rate based on </ins>rotation speed, <ins style="font-weight: bold; text-decoration: none;">environmental conditions </ins>(pressure and temperature) <ins style="font-weight: bold; text-decoration: none;">and others</ins>. <ins style="font-weight: bold; text-decoration: none;">A </ins>rotation sensor <ins style="font-weight: bold; text-decoration: none;">could a good start</ins>, measuring the magnetic field disturbances created by the blades or the rotor. Engine temperature should be controlled and recorded too<ins style="font-weight: bold; text-decoration: none;">, probably using a thermocouple</ins>. Pressure at different stages would be very useful for engine development <ins style="font-weight: bold; text-decoration: none;">and operating</ins>, <ins style="font-weight: bold; text-decoration: none;">but is also a quality source </ins>for <ins style="font-weight: bold; text-decoration: none;">failure detection</ins>. The rotor speed information and altimeter may be redundant with some of the pressure information<ins style="font-weight: bold; text-decoration: none;">.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">A [http://nescacademy.nasa.gov/video_catalog.php?catid=3&subcatid=1 NASA GN&C webcast] on the Fundamentals of Aircraft Engine Control presents control design, sensors used, and operational safety for turbofan engines ([http://mediaex-server.larc.nasa.gov/Academy/Viewer/?peid=135553bc3b7b4171b7c54ee0578489211d direct link])</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to rotor===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to rotor===</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=565&oldid=prevVincent: /* Startup and ignition */ more details2015-01-20T01:08:58Z<p><span dir="auto"><span class="autocomment">Startup and ignition: </span> more details</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Several cooling ways are used in a turbofan/turbojet engine: in the combustion chambers, only a small amount of the actual air flow is used for the combustion, around 20%. The rest is injected on the walls of the chamber and in the end of the combustion to dilute the hot gas, and to prevent the walls from melting (film cooling). Then, the first object struck by this hot gas is the vanes the turbine, which are, on actual engines, made of a ceramic-coated high-temperature alloy, but more importantly, hollow. Blades are welded on the stator ring, around which air from the compressor discharge or bleed circulates, enters the blades, and evacuates through small holes in the blades (convective cooling and film cooling). For the rotor blades, the same principle is used, but with compressor air passing inside the rotor.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Several cooling ways are used in a turbofan/turbojet engine: in the combustion chambers, only a small amount of the actual air flow is used for the combustion, around 20%. The rest is injected on the walls of the chamber and in the end of the combustion to dilute the hot gas, and to prevent the walls from melting (film cooling). Then, the first object struck by this hot gas is the vanes the turbine, which are, on actual engines, made of a ceramic-coated high-temperature alloy, but more importantly, hollow. Blades are welded on the stator ring, around which air from the compressor discharge or bleed circulates, enters the blades, and evacuates through small holes in the blades (convective cooling and film cooling). For the rotor blades, the same principle is used, but with compressor air passing inside the rotor.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>===<del style="font-weight: bold; text-decoration: none;">Startup </del>and ignition===</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>===<ins style="font-weight: bold; text-decoration: none;">Start-up </ins>and ignition===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">Startup </del>can be done at ground manually, with compressed air or a high speed electric engine for example, which will allow <del style="font-weight: bold; text-decoration: none;">to reduce the </del>weight and complexity of the engine. On the other side, a turbine engine is a nice way of having power on-board, using reducing gears and an alternator. That would also reduce the weight required for batteries, <del style="font-weight: bold; text-decoration: none;">and </del>the alternator would be used reversely as a <del style="font-weight: bold; text-decoration: none;">startup </del>DC motor. Also, the accessories attached to the reduced shaft would allow hydraulic or pneumatic power to be considered.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Start-up </ins>can be done at ground manually, with compressed air or a high speed electric engine for example, which will allow weight and complexity of the engine <ins style="font-weight: bold; text-decoration: none;">to be reduced</ins>. On the other side, a turbine engine is a nice way of having power on-board, using reducing gears and an alternator. That would also reduce the weight required for batteries, <ins style="font-weight: bold; text-decoration: none;">since </ins>the alternator would be used reversely as a <ins style="font-weight: bold; text-decoration: none;">start-up </ins>DC motor. Also, the accessories attached to the reduced shaft would allow hydraulic or pneumatic power to be considered<ins style="font-weight: bold; text-decoration: none;">. Our main issue for such turbine accessories with a very small engine would be to find the actual space in it where they could fit, especially with a cheap and efficient approach</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Igniter mechanisms must be integrated to the engine, possibly a self-maintaining igniter like a thread of tungsten, as used in miniature R/C engines. The combustion should be self-maintaining, but if pump or <del style="font-weight: bold; text-decoration: none;">throttling malfunction</del>, or <del style="font-weight: bold; text-decoration: none;">more generally </del>if a <del style="font-weight: bold; text-decoration: none;">turbulence </del>in the intake <del style="font-weight: bold; text-decoration: none;">happen, </del>leading to <del style="font-weight: bold; text-decoration: none;">a discontinuous flow of fuel or air and </del>compressor stall, re-ignition would have to be made during the flight.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Igniter mechanisms must be integrated to the engine, possibly a self-maintaining igniter like a thread of tungsten, as used in miniature R/C engines. The combustion should be self-maintaining <ins style="font-weight: bold; text-decoration: none;">under normal circumstances</ins>, but if pump or <ins style="font-weight: bold; text-decoration: none;">throttle malfunctions</ins>, or if <ins style="font-weight: bold; text-decoration: none;">there is </ins>a <ins style="font-weight: bold; text-decoration: none;">disruption </ins>in the intake <ins style="font-weight: bold; text-decoration: none;">airflow </ins>leading to <ins style="font-weight: bold; text-decoration: none;">[https://en.wikipedia.org/wiki/Compressor_stall </ins>compressor stall<ins style="font-weight: bold; text-decoration: none;">]</ins>, re-ignition would have to be made during the flight<ins style="font-weight: bold; text-decoration: none;">. Free restart of a turbofan is possible if the airspeed is sufficient to make it rotate at the start-up angular velocity, but in other cases that would require an embedded start-up motor or compressed air input. On airliners, bleed air from another engine can be used, but with such tightly constrained motors, we would have a hard time enabling that</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Sensors===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Sensors===</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=562&oldid=prevVincent: /* Shaped core or shaped shaft? */ hollow shaft for cooling air2015-01-12T00:29:59Z<p><span dir="auto"><span class="autocomment">Shaped core or shaped shaft?: </span> hollow shaft for cooling air</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [https://en.wikipedia.org/wiki/Lathe lathe] ([https://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [https://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines. These also do not scale down very well.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [https://en.wikipedia.org/wiki/Lathe lathe] ([https://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [https://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines. These also do not scale down very well.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator with such a small scale and how to fix the rotor on the stator with little gap?</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage<ins style="font-weight: bold; text-decoration: none;">. A big advantage of that is that the shaft can pass compressor bleed air to the turbines to use it as coolant</ins>. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator with such a small scale and how to fix the rotor on the stator with little gap?</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_craftedshaft.svg.png]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_craftedshaft.svg.png]]</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=561&oldid=prevVincent: /* Design versus manufacturing */ minor text updates2015-01-12T00:11:32Z<p><span dir="auto"><span class="autocomment">Design versus manufacturing: </span> minor text updates</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design versus manufacturing==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design versus manufacturing==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Design configurations and properties taken into concern on real engines <del style="font-weight: bold; text-decoration: none;">tend </del>to increase efficiency, <del style="font-weight: bold; text-decoration: none;">i.e. higher thrusts for lower fuel consumption, but also try to </del>reduce <del style="font-weight: bold; text-decoration: none;">the exhaust </del>noise. Cost is of course a concern, and an efficiency by itself, but <del style="font-weight: bold; text-decoration: none;">maybe </del>not <del style="font-weight: bold; text-decoration: none;">a hard-</del>constraint as it is for us. Safety of operation is their primary concern, whereas cost and ease of maintenance are our primary concerns -- and maintenance will be an important part of the job if the quality goes down with the cost.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Design configurations and properties taken into concern on real engines <ins style="font-weight: bold; text-decoration: none;">aim </ins>to increase efficiency, reduce noise<ins style="font-weight: bold; text-decoration: none;">, life time</ins>. Cost is of course a concern, and an efficiency by itself, but not <ins style="font-weight: bold; text-decoration: none;">the primary </ins>constraint as it is for us. Safety of operation is their primary concern, whereas cost and ease of maintenance are our primary concerns -- and maintenance will be an important part of the job if the quality goes down with the cost.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Shaped core or shaped shaft?===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Shaped core or shaped shaft?===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [https://en.wikipedia.org/wiki/Lathe lathe] ([https://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [https://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [https://en.wikipedia.org/wiki/Lathe lathe] ([https://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [https://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines<ins style="font-weight: bold; text-decoration: none;">. These also do not scale down very well</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator<del style="font-weight: bold; text-decoration: none;">, </del>how to fix the rotor on the stator with little gap<del style="font-weight: bold; text-decoration: none;">, and how to balance it/them</del>?</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator <ins style="font-weight: bold; text-decoration: none;">with such a small scale and </ins>how to fix the rotor on the stator with little gap?</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_craftedshaft.svg.png]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_craftedshaft.svg.png]]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Compressor and turbine blades===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Compressor and turbine blades===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The most complicated parts to build in a turbofan or turbojet engine are the turbine and compressor blades. The high-pressure turbine <del style="font-weight: bold; text-decoration: none;">specially </del>have to face very high temperature and pressure. On real engines, they are made of nickel-based [https://en.wikipedia.org/wiki/Superalloys superalloys] <del style="font-weight: bold; text-decoration: none;">or are ceramic-coated</del>. It's the inability of blades to withstand heat and work that limit the power of the engine. Indeed, around 70% of the gas provided by the compressor is used only for chamber and turbine cooling, instead of using it to burn more fuel and <del style="font-weight: bold; text-decoration: none;">create </del>more thrust.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The most complicated parts to build in a turbofan or turbojet engine are the turbine and compressor blades. The high-pressure turbine <ins style="font-weight: bold; text-decoration: none;">specifically </ins>have to face very high temperature and pressure. On real engines, they are made of <ins style="font-weight: bold; text-decoration: none;">ceramic-coated </ins>nickel-based [https://en.wikipedia.org/wiki/Superalloys superalloys]. It's the inability of blades to withstand heat and work that limit the power of the engine. Indeed, around 70% of the gas provided by the compressor is used only for chamber and turbine cooling, instead of using it to burn more fuel and <ins style="font-weight: bold; text-decoration: none;">creating </ins>more thrust.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The compressor and the turbine are not only made of blades on the rotor, but also blades on the stator. They prevent a rotating air flow driven by the action of rotor blades to form inside the engine, which would <del style="font-weight: bold; text-decoration: none;">decrease the energy of </del>the gas. Stator blades or vanes redirect the airflow on the next stage in the more efficient direction.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The compressor and the turbine are not only made of blades on the rotor, but also blades on the stator<ins style="font-weight: bold; text-decoration: none;">, also called vanes</ins>. They prevent a rotating air flow driven by the action of rotor blades to form inside the engine, which would <ins style="font-weight: bold; text-decoration: none;">not allow pressure to be built on </ins>the gas <ins style="font-weight: bold; text-decoration: none;">at each stage</ins>. Stator blades or vanes redirect the airflow on the next stage in the more efficient direction <ins style="font-weight: bold; text-decoration: none;">(see [https://en.wikipedia.org/wiki/Velocity_triangle velocity triangle])</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Highest efficiencies are reached in turbofans when gaps are reduced between rotor blades' tip and the stator, as well as between the stator blades' tip and the rotor. As always, good efficiency means high precision and higher cost. Anyway, the precision of blades will have to be very good if we don't want it to dislocate when it reaches the high rotations-per-minute achieved by such engines. The shape of the <del style="font-weight: bold; text-decoration: none;">blade </del>and the parameters of their cascade also affects the efficiency. A small 5 stage supersonic compressor providing the same pressure rise than a 15 stage subsonic compressor is less efficient, but it may be compensated by the higher thrust-to-weight ratio.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Highest efficiencies are reached in turbofans when gaps are reduced between rotor blades' tip and the stator, as well as between the stator blades' tip and the rotor. As always, good efficiency means high precision and higher cost. Anyway, the precision of blades will have to be very good if we don't want it to dislocate when it reaches the high rotations-per-minute achieved by such engines. The shape of the <ins style="font-weight: bold; text-decoration: none;">blades </ins>and the parameters of their cascade also affects the efficiency<ins style="font-weight: bold; text-decoration: none;">, and in particular the pressure ratios</ins>. A small 5 stage supersonic compressor providing the same pressure rise than a 15 stage subsonic compressor is less efficient, but it <ins style="font-weight: bold; text-decoration: none;">''</ins>may<ins style="font-weight: bold; text-decoration: none;">'' </ins>be compensated by the higher thrust-to-weight ratio.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Blade geometric design is also very complicated. First turbine engines had flat blades. At the time, the efficiency of the engine was so terrible that it was believed that turbojets would never beat reciprocating engines. Then, in 1926, [https://en.wikipedia.org/wiki/Alan_Arnold_Griffith#Turbine_engines Alan A. Griffith] proved that if blades were designed as airfoils, the engine would behave way better, and would even be efficient enough to deserve being built. Airfoils for blade designs allow compressor stages to better increase the static pressure since they create an expander, an increasing area for the air flow to pass through.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Blade geometric design is also very complicated. First turbine engines had flat blades. At the time, the efficiency of the engine was so terrible that it was believed that turbojets would never beat reciprocating engines. Then, in 1926, [https://en.wikipedia.org/wiki/Alan_Arnold_Griffith#Turbine_engines Alan A. Griffith] proved that if blades were designed as <ins style="font-weight: bold; text-decoration: none;">aerofoils (</ins>airfoils <ins style="font-weight: bold; text-decoration: none;">in US English)</ins>, the engine would behave way better, and would even be efficient enough to deserve being built. Airfoils for blade designs allow compressor stages to better increase the static pressure since they create an expander, an increasing area for the air flow to pass through.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design considerations==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design considerations==</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=560&oldid=prevVincent: /* General principles */ updating section2015-01-11T21:28:12Z<p><span dir="auto"><span class="autocomment">General principles: </span> updating section</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==General principles==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==General principles==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">Lots </del>of information <del style="font-weight: bold; text-decoration: none;">are </del>available on [https://en.wikipedia.org/wiki/Turbofan <del style="font-weight: bold; text-decoration: none;">Wikipedia's </del>page]. General principle is that there is a combustion that puts energy into a gas, this energy is extracted by a turbine, and the turbine drives both the fan that provides thrust and the compression stage that feeds the combustion with oxygen. As air is compressed from the intake, more air becomes available for combustion, and thus create more work on the turbine, and more intake, and so on. The fan provides thrust by creating a massive air flow, and the engine's core also creates thrust by evacuating the high-speed hot combustion gas. In commercial turbofan engines, the fan is generally responsible for 90% of the overall thrust.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">A lot </ins>of information <ins style="font-weight: bold; text-decoration: none;">is </ins>available on <ins style="font-weight: bold; text-decoration: none;">Wikipedia's </ins>[https://en.wikipedia.org/wiki/Turbofan <ins style="font-weight: bold; text-decoration: none;">turbofan </ins>page]. General principle is that there is a combustion that puts energy into a gas, this energy is extracted by a turbine, and the turbine drives both the fan that provides thrust and the compression stage that feeds the combustion with oxygen. As air is compressed from the intake, more air becomes available for combustion, and thus create more work on the turbine, and more intake, and so on. The fan provides thrust by creating a massive air flow, and the engine's core also creates thrust by evacuating the high-speed hot combustion gas. In commercial turbofan engines, the fan is generally responsible for 90% of the overall thrust.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_operation.svg.png]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_operation.svg.png]]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some design properties and configurations have to be properly calculated depending on the use of the engine, mainly for the intended aircraft speed:</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some design properties and configurations have to be properly calculated depending on the use of the engine, mainly for the intended aircraft speed:</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* The [https://en.wikipedia.org/wiki/Bypass_ratio Bypass ratio] (BPR) is a ratio between the mass flow rate of air drawn in by the fan but bypassing the engine core to the mass flow rate passing through the engine core. <del style="font-weight: bold; text-decoration: none;">A </del>BPR = 0 would be a turbojet engine. The higher BPR, the more efficient the engine, but also the slower exhaust speed.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* The [https://en.wikipedia.org/wiki/Bypass_ratio Bypass ratio] (BPR) is a ratio between the mass flow rate of air drawn in by the fan but bypassing the engine core to the mass flow rate passing through the engine core. <ins style="font-weight: bold; text-decoration: none;">An engine with a </ins>BPR = 0 would be a turbojet engine. The higher BPR, the more efficient the engine, but also the slower exhaust speed.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* The number of spools: modern engines embed a second and sometimes a third concentric shaft for high pressure operations. The low pressure shaft, the innermost, has the fan mounted on it. One stage engines exist and are less complicated and expensive to build, but are much less efficient. Indeed, higher rotation speeds in the internal spools allow to provide a more efficient compression. A gearbox may be needed to drive the fan if the shaft has a too important rotation speed in the case of a single-spooled turbofan, but this is not an easy task due to <del style="font-weight: bold; text-decoration: none;">this </del>very speed. Commercial engines featuring a gearbox for the turbofan's fan <del style="font-weight: bold; text-decoration: none;">are expected to reach </del>market in <del style="font-weight: bold; text-decoration: none;">2012</del>. Multi-spooled engines <del style="font-weight: bold; text-decoration: none;">prevent </del>this issue, by keeping the low-pressure stages at relatively low speeds, suited for the fan, <del style="font-weight: bold; text-decoration: none;">but are not yet optimal</del>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* The number of spools: modern engines embed a second and sometimes a third concentric shaft for high pressure operations. The low pressure shaft, the innermost, has the fan mounted on it. One<ins style="font-weight: bold; text-decoration: none;">-</ins>stage engines exist and are less complicated and expensive to build, but are much less efficient. Indeed, higher rotation speeds in the internal spools allow to provide a more efficient compression. A gearbox may be needed to drive the fan if the shaft has a too important rotation speed in the case of a single-spooled turbofan, but this is not an easy task due to <ins style="font-weight: bold; text-decoration: none;">its </ins>very speed. Commercial engines featuring a gearbox for the turbofan's fan <ins style="font-weight: bold; text-decoration: none;">([https://en.wikipedia.org/wiki/Geared_turbofan geared turbofans]) have reached </ins>market in <ins style="font-weight: bold; text-decoration: none;">the past few years</ins>. Multi-spooled engines <ins style="font-weight: bold; text-decoration: none;">lessen </ins>this issue, by keeping the low-pressure stages at relatively low speeds, suited for the fan<ins style="font-weight: bold; text-decoration: none;">. High-speed fans are complicated to understand and design, and undergo higher losses due to transonic regime</ins>, <ins style="font-weight: bold; text-decoration: none;">and having a gearbox on a twin-spool engine is even better, to get a high efficiency turbine and a slowly rotating fan</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* The compression ratio is the ratio of the pressure of intake air on compressor discharge air. It is closely determined by the number of stages in the compressor and their efficiency. More compression means more air to blend with fuel and to cool the engine, and even more pressure at output, increasing the speed and mass of output gas and thus the work that can be extracted by the turbines and <del style="font-weight: bold; text-decoration: none;">overall engine efficiency</del>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* The compression ratio is the ratio of the pressure of intake air on compressor discharge air. It is closely determined by the number of stages in the compressor and their efficiency. More compression means more air to blend with fuel and to cool the engine, and even more pressure at output, increasing the speed and mass of output gas and thus the work that can be extracted by the turbines<ins style="font-weight: bold; text-decoration: none;">.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">* The turbine inlet temperature is the key parameter for turbine engine. Attaining higher temperatures after combustion, in the turbine inlet, makes an engine more efficient, as explained by the [https://en.wikipedia.org/wiki/Brayton_cycle Brayton thermodynamic cycle]. The obvious issue is the temperature that materials can withstand, in particular the first turbine guide vane and the first high-pressure turbine blades. [https://en.wikipedia.org/wiki/High_temperature_metal High-temperature alloys] </ins>and <ins style="font-weight: bold; text-decoration: none;">special cooling techniques, like [https://en.wikipedia.org/wiki/Turbine_blade#Film_cooling film cooling] using some compressor [https://en.wikipedia.org/wiki/Bleed_air bleed air], have to be employed</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Turbojet/turbofan engine simulation software from NASA: [http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html EngineSim]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Turbojet/turbofan engine simulation software from NASA: [http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html EngineSim]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A must-read book by Klaus Hünecke: [http://books.google.com/books?id=VpJEm7cFVE4C Jet engines: fundamentals of theory, design, and operation].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A must-read book by Klaus Hünecke: [http://books.google.com/books?id=VpJEm7cFVE4C Jet engines: fundamentals of theory, design, and operation].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Video documentaries from a turbine renovator in Canada, probably the best resource on the Web for seeing what's inside real engines: [<del style="font-weight: bold; text-decoration: none;">http</del>://www.youtube.com/user/AgentJayZ<del style="font-weight: bold; text-decoration: none;">#p/u/16/giRA01IHexk </del>on youtube]. <del style="font-weight: bold; text-decoration: none;">Thanks AgentJayZ</del>!</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Video documentaries from a turbine renovator in Canada, probably the best resource on the Web for seeing what's inside real engines: [<ins style="font-weight: bold; text-decoration: none;">https</ins>://www.youtube.com/user/AgentJayZ <ins style="font-weight: bold; text-decoration: none;">AgentJayZ </ins>on youtube]. <ins style="font-weight: bold; text-decoration: none;">Huge thanks to you</ins>!</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design versus manufacturing==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design versus manufacturing==</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=535&oldid=prevVincent: /* Fixing blades to rotor */ price induction and bladon link2013-10-01T00:14:56Z<p><span dir="auto"><span class="autocomment">Fixing blades to rotor: </span> price induction and bladon link</span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 00:14, 1 October 2013</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l63">Line 63:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to rotor===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to rotor===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>In real engines, blades are fixed like [http://www.shutterstock.com/pic-9557743/stock-photo-jet-engine.html this], with a dovetail or fir-tree shape that allow them to be mounted and removed axially but not orthogonally. The main problem appearing with this kind of mount is related to the size of the engines we aim. As the diameter of the fan shaft gets smaller, the available space for the blade roots gets smaller, and require a higher precision for their manufacturing. The strength applying to the fixation is luckily reduced due to the small weight of the blades. A simpler design in blade root would be nice for manufacturing ease, a simple square-section root is probably enough.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>In real engines, blades are fixed like [http://www.shutterstock.com/pic-9557743/stock-photo-jet-engine.html this], with a dovetail or fir-tree shape that allow them to be mounted and removed axially but not orthogonally. The main problem appearing with this kind of mount is related to the size of the engines we aim. As the diameter of the fan shaft gets smaller, the available space for the blade roots gets smaller, and require a higher precision for their manufacturing<ins style="font-weight: bold; text-decoration: none;">. See this example of small fan, from [http://www.price-induction.com/site_media/images/dgen-net/technologies/optimisation_de_masse_grand.jpg Price Induction]</ins>. The strength applying to the fixation is luckily reduced due to the small weight of the blades. A simpler design in blade root would be nice for manufacturing ease, a simple square-section root is probably enough<ins style="font-weight: bold; text-decoration: none;">.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Another lead is to create the blade disk and the blades in a single piece. This can be done with modern manufacturing process like electric discharge machining, 5-dof machining or even laser-based 3D printing. Here is an example from Bladon Jets, [http://www.bladonjets.com/technology/blisk/ the BLISK]</ins>.</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to stator===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Fixing blades to stator===</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=338&oldid=prevVincent: https for wikipedia2012-10-15T02:20:55Z<p>https for wikipedia</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 02:20, 15 October 2012</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==General principles==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==General principles==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Lots of information are available on [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Turbofan Wikipedia's page]. General principle is that there is a combustion that puts energy into a gas, this energy is extracted by a turbine, and the turbine drives both the fan that provides thrust and the compression stage that feeds the combustion with oxygen. As air is compressed from the intake, more air becomes available for combustion, and thus create more work on the turbine, and more intake, and so on. The fan provides thrust by creating a massive air flow, and the engine's core also creates thrust by evacuating the high-speed hot combustion gas. In commercial turbofan engines, the fan is generally responsible for 90% of the overall thrust.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Lots of information are available on [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Turbofan Wikipedia's page]. General principle is that there is a combustion that puts energy into a gas, this energy is extracted by a turbine, and the turbine drives both the fan that provides thrust and the compression stage that feeds the combustion with oxygen. As air is compressed from the intake, more air becomes available for combustion, and thus create more work on the turbine, and more intake, and so on. The fan provides thrust by creating a massive air flow, and the engine's core also creates thrust by evacuating the high-speed hot combustion gas. In commercial turbofan engines, the fan is generally responsible for 90% of the overall thrust.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_operation.svg.png]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:500px-Turbofan_operation.svg.png]]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some design properties and configurations have to be properly calculated depending on the use of the engine, mainly for the intended aircraft speed:</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Some design properties and configurations have to be properly calculated depending on the use of the engine, mainly for the intended aircraft speed:</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* The [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Bypass_ratio Bypass ratio] (BPR) is a ratio between the mass flow rate of air drawn in by the fan but bypassing the engine core to the mass flow rate passing through the engine core. A BPR = 0 would be a turbojet engine. The higher BPR, the more efficient the engine, but also the slower exhaust speed.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* The [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Bypass_ratio Bypass ratio] (BPR) is a ratio between the mass flow rate of air drawn in by the fan but bypassing the engine core to the mass flow rate passing through the engine core. A BPR = 0 would be a turbojet engine. The higher BPR, the more efficient the engine, but also the slower exhaust speed.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* The number of spools: modern engines embed a second and sometimes a third concentric shaft for high pressure operations. The low pressure shaft, the innermost, has the fan mounted on it. One stage engines exist and are less complicated and expensive to build, but are much less efficient. Indeed, higher rotation speeds in the internal spools allow to provide a more efficient compression. A gearbox may be needed to drive the fan if the shaft has a too important rotation speed in the case of a single-spooled turbofan, but this is not an easy task due to this very speed. Commercial engines featuring a gearbox for the turbofan's fan are expected to reach market in 2012. Multi-spooled engines prevent this issue, by keeping the low-pressure stages at relatively low speeds, suited for the fan, but are not yet optimal.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* The number of spools: modern engines embed a second and sometimes a third concentric shaft for high pressure operations. The low pressure shaft, the innermost, has the fan mounted on it. One stage engines exist and are less complicated and expensive to build, but are much less efficient. Indeed, higher rotation speeds in the internal spools allow to provide a more efficient compression. A gearbox may be needed to drive the fan if the shaft has a too important rotation speed in the case of a single-spooled turbofan, but this is not an easy task due to this very speed. Commercial engines featuring a gearbox for the turbofan's fan are expected to reach market in 2012. Multi-spooled engines prevent this issue, by keeping the low-pressure stages at relatively low speeds, suited for the fan, but are not yet optimal.</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l31">Line 31:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Shaped core or shaped shaft?===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Shaped core or shaped shaft?===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Lathe lathe] ([<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>An obvious but important optimization to reduce cost and complexity of manufacturing is to have a simpler design of the parts creating the gas volume of the engine's core, i.e. the rotor(s) and the stator. In the above schema, we see that the shaft is straight and that the core envelope is curved suit required volume on each stage, although in real life, both are curved. If we take the required volumes on each stage and that we fix the core's envelope shape to a cylinder, the shaft will have a bumped profile (small-large-small diameter). This is much less expensive to design and produce, with a simple [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Lathe lathe] ([<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Turning turning]). Earlier engines, like the [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/J79 J79], have a cylindrical envelope. A curved envelope is complicated to build, requiring welding, pressing, stage bolting, the same techniques used in stator-construction in modern engines.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator, how to fix the rotor on the stator with little gap, and how to balance it/them?</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Real-world engines don't have a massive turned shaft because of the weight. They consist of plates, for each compressor and turbine stage, that are linked together to the next stage using a cylindrical bolted joint. So basically, the shaft has no core, it's hollow, except for the plates on each stage. Our small engine design allows us to have a more simple design, since having a shaft turned in raw metal won't change much on its final mass. Moreover, we may use a turbine-level mechanism embedded in the stator to try to cool it, which would make it hollow. The main mechanical issues are probably how to properly fix the blades on rotor and stator, how to fix the rotor on the stator with little gap, and how to balance it/them?</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l39">Line 39:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Compressor and turbine blades===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Compressor and turbine blades===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The most complicated parts to build in a turbofan or turbojet engine are the turbine and compressor blades. The high-pressure turbine specially have to face very high temperature and pressure. On real engines, they are made of nickel-based [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Superalloys superalloys] or are ceramic-coated. It's the inability of blades to withstand heat and work that limit the power of the engine. Indeed, around 70% of the gas provided by the compressor is used only for chamber and turbine cooling, instead of using it to burn more fuel and create more thrust.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The most complicated parts to build in a turbofan or turbojet engine are the turbine and compressor blades. The high-pressure turbine specially have to face very high temperature and pressure. On real engines, they are made of nickel-based [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Superalloys superalloys] or are ceramic-coated. It's the inability of blades to withstand heat and work that limit the power of the engine. Indeed, around 70% of the gas provided by the compressor is used only for chamber and turbine cooling, instead of using it to burn more fuel and create more thrust.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The compressor and the turbine are not only made of blades on the rotor, but also blades on the stator. They prevent a rotating air flow driven by the action of rotor blades to form inside the engine, which would decrease the energy of the gas. Stator blades or vanes redirect the airflow on the next stage in the more efficient direction.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The compressor and the turbine are not only made of blades on the rotor, but also blades on the stator. They prevent a rotating air flow driven by the action of rotor blades to form inside the engine, which would decrease the energy of the gas. Stator blades or vanes redirect the airflow on the next stage in the more efficient direction.</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l45">Line 45:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Highest efficiencies are reached in turbofans when gaps are reduced between rotor blades' tip and the stator, as well as between the stator blades' tip and the rotor. As always, good efficiency means high precision and higher cost. Anyway, the precision of blades will have to be very good if we don't want it to dislocate when it reaches the high rotations-per-minute achieved by such engines. The shape of the blade and the parameters of their cascade also affects the efficiency. A small 5 stage supersonic compressor providing the same pressure rise than a 15 stage subsonic compressor is less efficient, but it may be compensated by the higher thrust-to-weight ratio.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Highest efficiencies are reached in turbofans when gaps are reduced between rotor blades' tip and the stator, as well as between the stator blades' tip and the rotor. As always, good efficiency means high precision and higher cost. Anyway, the precision of blades will have to be very good if we don't want it to dislocate when it reaches the high rotations-per-minute achieved by such engines. The shape of the blade and the parameters of their cascade also affects the efficiency. A small 5 stage supersonic compressor providing the same pressure rise than a 15 stage subsonic compressor is less efficient, but it may be compensated by the higher thrust-to-weight ratio.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Blade geometric design is also very complicated. First turbine engines had flat blades. At the time, the efficiency of the engine was so terrible that it was believed that turbojets would never beat reciprocating engines. Then, in 1926, [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Alan_Arnold_Griffith#Turbine_engines Alan A. Griffith] proved that if blades were designed as airfoils, the engine would behave way better, and would even be efficient enough to deserve being built. Airfoils for blade designs allow compressor stages to better increase the static pressure since they create an expander, an increasing area for the air flow to pass through.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Blade geometric design is also very complicated. First turbine engines had flat blades. At the time, the efficiency of the engine was so terrible that it was believed that turbojets would never beat reciprocating engines. Then, in 1926, [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Alan_Arnold_Griffith#Turbine_engines Alan A. Griffith] proved that if blades were designed as airfoils, the engine would behave way better, and would even be efficient enough to deserve being built. Airfoils for blade designs allow compressor stages to better increase the static pressure since they create an expander, an increasing area for the air flow to pass through.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design considerations==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Design considerations==</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l89">Line 89:</td>
<td colspan="2" class="diff-lineno">Line 89:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># evaluate required thrust (from aircraft mass and lift, but also [[Flight_at_high_altitude|flight characteristics]])</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># evaluate required thrust (from aircraft mass and lift, but also [[Flight_at_high_altitude|flight characteristics]])</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># calculate required mass flow rate for the fan (thust is [<del style="font-weight: bold; text-decoration: none;">http</del>://en.wikipedia.org/wiki/Thrust calculated] from MFR and flow speed)</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># calculate required mass flow rate for the fan (thust is [<ins style="font-weight: bold; text-decoration: none;">https</ins>://en.wikipedia.org/wiki/Thrust calculated] from MFR and flow speed)</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># fix bypass ratio and fan diameter and rpm, thus giving core diameter (BPR may be [[Turbofan:Alternative_Designs#Full_transonic_engine_design_in_a_single_spool_with_2.1_BPR|fixed by design]])</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># fix bypass ratio and fan diameter and rpm, thus giving core diameter (BPR may be [[Turbofan:Alternative_Designs#Full_transonic_engine_design_in_a_single_spool_with_2.1_BPR|fixed by design]])</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># calculate required power to drive the fan alone</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># calculate required power to drive the fan alone</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=265&oldid=prevVincent: /* Turbofan design procedure */ links to work on the three first design steps2011-12-09T01:00:06Z<p><span dir="auto"><span class="autocomment">Turbofan design procedure: </span> links to work on the three first design steps</span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en-GB">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 01:00, 9 December 2011</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l88">Line 88:</td>
<td colspan="2" class="diff-lineno">Line 88:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Turbofan design procedure===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Turbofan design procedure===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># evaluate required thrust (from aircraft mass and lift)</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># evaluate required thrust (from aircraft mass and lift<ins style="font-weight: bold; text-decoration: none;">, but also [[Flight_at_high_altitude|flight characteristics]]</ins>)</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># calculate required mass flow rate for the fan</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># calculate required mass flow rate for the fan <ins style="font-weight: bold; text-decoration: none;">(thust is [http://en.wikipedia.org/wiki/Thrust calculated] from MFR and flow speed)</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># fix bypass ratio and fan diameter and rpm, thus giving core diameter</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># fix bypass ratio and fan diameter and rpm, thus giving core diameter <ins style="font-weight: bold; text-decoration: none;">(BPR may be [[Turbofan:Alternative_Designs#Full_transonic_engine_design_in_a_single_spool_with_2.1_BPR|fixed by design]])</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># calculate required power to drive the fan alone</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># calculate required power to drive the fan alone</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># evaluate a gross compressor driving power (refined later)<br />&nbsp;</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># evaluate a gross compressor driving power (refined later)<br />&nbsp;</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=232&oldid=prevVincent: /* Our design propositions */ design procedure2011-10-23T23:06:56Z<p><span dir="auto"><span class="autocomment">Our design propositions: </span> design procedure</span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en-GB">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:06, 23 October 2011</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l85">Line 85:</td>
<td colspan="2" class="diff-lineno">Line 85:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Turbofan:Combustors|Combustors]]: Combustors are the power input of the engine, and need not to melt while sustaining the combustion.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Turbofan:Combustors|Combustors]]: Combustors are the power input of the engine, and need not to melt while sustaining the combustion.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Turbofan:Bearings|Bearings and cooling]]: high speed rotations require adapted bearings and cooling, which may be reused for rotor and even turbine cooling.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Turbofan:Bearings|Bearings and cooling]]: high speed rotations require adapted bearings and cooling, which may be reused for rotor and even turbine cooling.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">===Turbofan design procedure===</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># evaluate required thrust (from aircraft mass and lift)</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate required mass flow rate for the fan</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># fix bypass ratio and fan diameter and rpm, thus giving core diameter</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate required power to drive the fan alone</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># evaluate a gross compressor driving power (refined later)<br />&nbsp;</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate total power that has to be drawn from the turbine (fan + compressor + losses)</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate mass flow rate for the combustion alone</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate mass flow rate for cooling chamber and turbine</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">## calculate mass flow rate for cooling chamber</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">## evaluate mass flow rate for cooling turbine to add to the latter</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">## calculate entropy and fluid parameters at combustor discharge (speed, temperature)</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">## calculate temperature of turbine vanes and blade and check if it is acceptable</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">## iterate on item 8.1 until temperature is unacceptable</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate the number of turbine blades and stages required for this power</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate compressor discharge pressure and pressure ratio</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate how many compressor stages are required depending on sonic or supersonic blade design and fix design</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># calculate compressor driving power</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># iterate on item 6 until total power varies</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"># design blades for all calculated parameters and re-run at item 6, total power may have changed</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Category:Turbofan]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Category:Turbofan]]</div></td></tr>
</table>Vincenthttps://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=229&oldid=prevVincent: Text corrections2011-10-21T00:20:32Z<p>Text corrections</p>
<a href="https://lcas.otaski.org/index.php?title=Build_a_cheap_turbofan&diff=229&oldid=210">Show changes</a>Vincent