Numerical Simulation Of The Fan / Compressor Aerodynamic Stability

The design and evaluation of the aerodynamic stability is one of important contents during the development of aircraft gas-turbine engine. The fan and compressor is the most sensitive part to the engine inlet airflow. The pressure and the temperature distortion of inflow can cause the compressor to lose the stability and enter the surge. When the engine loses aerodynamic stability, it can endanger the flight safety directly. The mathematic model and numerical simulation method were developed in this paper to predict and analyze the aerodynamic stability of fan and compressor with and without inflow distortion.A quasi one-dimensional, stage-by-stage, nonlinear mathematical model for the axial fan and compression system aerodynamic stability has been constructed in the paper based on compressor stage characteristics. The model uses a finite difference numerical technique to simultaneously solve the nonlinear mass, momentum, and energy equations with turbo-machinery source terms (mass bleed, blade forces, and shaft work). These source terms in the control equations are determined from a complete set of stage characteristics. This nonlinear mathematical model can not only predict the stability limit but also indicate which stage initiates the instability. Combined with the parallel compressor theory, the model can be used to predict the effect of inflow distortion on the aerodynamic stability.The detailed numerical simulations describe the mechanism of the stability margin loss with inlet combined distortion of pressure and temperature. It is shown that total pressure and total temperature distortion themselves change in the flowage, further more the inflow distortion induce to the loss of compressor stability margin. The static pressure alteration at each stage entrance with different inlet total temperature ramp was also calculated. The quantities relationship between temperature ramp and time to surge is obtained as well. Post-stall behavior is simulated in the paper to estimate whether surge or rotating stall initiate with engine design parameters.