Research On Modeling And Aerodynamic Performance For Variable Cycle Engine

With the change of operational mode of military aircraft,traditional aero engines are more and more difficult to meet the performance requirements of the fifth generation fighter for high specific thrust and low cruise fuel consumption,and the variable cycle engine shows great potential in this field.This paper established a variable cycle engine simulink model,and the overall performance of variable cycle engine is simulated.Then the performance of various mode and conventional turbofan engine is compared,meanwhile the simulink model of bypass injector is verified and modified by CFD numerical simulation.The main contents are as follows:(1)The real-time simulation model of mixed exhaust turbofan engine is established based on the method of cavity,considering the volume of the engine assembly and the connecting section.The combustion chamber and the outer culvert are regarded as cavity,another cavity joined between HP and LP turbine,so that the pressure difference between the inlet and outlet is ignored and the iterative calculation caused by flow balance is avoided.Through two designed typical bypassratio turbofan engine models turbofan engine parameters of various flight conditions are obtained.(2)Starting from the theory of turbulent jet,the physical model of bypass injectors is seen as the stream in tube.Based on the theory of turbulent jet,bypass injector model is built by simulink,with comparison expression of bypass injector modified according to the CFD simulation data.The designed parameters of variable cycle engine under different working conditions are compared including single and double working mode.(3)The overall performance of variable cycle engine is analyzed by the variable cycle engine simulink model,found that:(1)Compared to the conventional turbofan engine,the fuel consumption rate of two bypasses variable cycle engine(0.6 bypass radio)is reduced by 13.3% during the subsonic cruise point.Compared to the conventional turbofan engine,the specific thrust of single bypass variable cycle engine(0.05 bypass radio)is 10% higher during the supersonic cruise point(2)At the same level of thrust,the air flow of double bypass mode(0.6 bypass radio)is 8% higher than of the conventional turbofan engine.This result shows that variable cycle engine of double bypass mode can inhale more air flow,decrease the overflow inlet resistance,improve the installation level of engine thrust and the advantages in low speed condition is more obvious(3)The increase of bypass ratio has great influence on the stability of fan、CDFS and the compressor,so the characteristic match among fan、CDFS and the compressor in actual engine work should be paid attention to.(4)Bypass injectors are simulated by CFD to verify the reliability of Simulink model based on turbulent jet,and the simulink model of bypass injector is verified and modified by CFD numerical simulation.