Adaptive jet engines, advantages and application opportunities

The paper has been intended to shortly describe the design of an adaptive jet engine, commonly termed 'the bypass engine'. Examples have been presented of how the bleeding of air affects the most essential engine performance characteristics, i.e. thrust, specific fuel consumption, and efficiency. Pointed out are economic advantages (only slight) of the application of this design as compared to the one-pass turbojet engine with no bleed. Furthermore, considered are capabilities to adapt an engine design of the bypass type for a one-pass turbojet engine K-15 as one of several upgrade opportunities. Simulation-based computations have proved, however, that there are some limitations on the bleed air amount and initial engine operational range for the accomplishment of the idea from the standpoint of capabilities to maintain conditions for the compressor-turbine matching. Also, the effect of this type of air bleeding upon the engine running-up process and the change in the running-up time for this type of the upgraded engine has been shown. In the Recapitulation and Conclusions section a mention has been made on the amount of bleed air to be passed through external channels from behind the compressor to behind the turbine: the bleed air amount increases as the total rate of the air flow along the engine flow path increases. It means that better effects of applying this type of air bleeding processes are gained in large engines. Presented are also capabilities of further developments and applications.