Turbofan:Alternative Designs

Alternative design for turbofans

All recent engines have the same basic architecture: a fan at the front, the turbine engine below it, and the two flows mix at the exhaust. Early designs of turbofans were actually created by putting a ducted fan on the aft part of a turbojet engine, since turbojet engines were already existing. They were not so bad in terms of efficiency compared to front-mounting engines, but the main issue was that the fan was evolving in a quite hot gas flow, which would eventually corrode or fatigue it more than at normal temperature.

A second fact is that high-efficiency engines, or modern engines, all use axial-type compressor and axial-type turbine. Some early or low power design include a centrifugal-type compressor, and only one engine to our knowledge had a centrifugal turbine, long ago.

From these two facts, we propose a novel design for turbofans, at least as long as research or people won't have proven it was wrong: an axial-compressor, hybrid-turbine, aft-mounted ducted fan. The so-called hybrid turbine would be a mix of axial and centrifugal designs, in which the hot gas flow would be slightly diverted from its course, while using (a part of) the energy required to divert it. The aft-fan would intake the mixed flow of the fresh intake and the turbine discharge, providing higher energy to the fan flow. Properly mixing the two flows would allow the fan to be build with low enough temperature metals, like aluminum alloys. The result will inevitably be a slightly longer engine.

Drawings (schematics or 3D CAD models) are coming soon.