ABSTRACT
One of the main challenges for the aeroengine designer is to develop new power systems that fulfill the requirements of both civil and military aircraft. The main issues now are the reduction of fuel burn, emissions, and noise while maintaining very high power/thrust levels and high propulsive and thermal efficiencies. Such engines, characterized by great power/thrust and low fuel consumption, directly affect an aircraft’s payload, maneuverability, and maximum range. Perhaps the obvious way to reduce emission is to reduce the fuel burnt. Increasing the bypass ratio (BPR) of turbofan engines minimizes the kinetic energy of the exhaust gas and thus increases the propulsive efficiency. Then the value of the BPR is near its limit, and it is difficult to think of ways to continue this trend indefinitely [1]. However, the ultra-bypass ratio (UBPR) is a feasible proposal. With compressor and turbine efficiencies near plateauing, and turbine inlet temperatures paced by materials and blade cooling technologies, improvements in thrust specific fuel (SFC), specific power, and weight for conventional engines (including turboprop and turboshaft engines and larger turbofans) will likely be incremental compared with the past [2].
