The Establish Of Stall Model And Active Stability Control Of Turbofan Engine

The main forms of compressor's aerodynamic instability are rotating stall and surge,which seriously affect the stable operation of the engine.With the increasing requirement of the modern aircraft performance and the demand for the ability of super-maneuvering flight,the conditions of the air inlet and the flight environment of aircraft will get worse and worse.In this case,it may lead to a higher probability of rotating stall and even surge,which seriously affects the stability and reliability of the engine.In this thesis,aerodynamic instability phenomenon was studied,a post surge compressor model was designed and the stall prediction algorithm was devised based on experimental data.The establishment of the stall model of turbo-fan engine and the design of active controller of stability were realized in this paper.First of all,this paper analyzed the total pressure distortion effect on the surge margin.Based on the experimental data of a low speed axial flow compressor,the fluctuating law of the pressure signal of the blade tip was fitted by Fourier analysis,and the stall model of compressor was built.With the correlation analysis and BP neural network algorithm,the compressor's working state could be predicted.Secondly,based on the component level model of a certain turbo-fan engine,the post-stall engine model was built.It considered all the factors including combustion's extinction characteristics,fan and compressor's stall area characteristics and distorted model of inlet flow field.Based on the volume kinetics effect and the rotor dynamics,six differential equations were established.The first-order Runge-Kutta method was used to solve the differential equations,and the simulation was carried out.Finally,with the demand for the high stability of the engine's control in the super-maneuver flight,the stability of active control was studied in this paper.The prediction algorithm of BP network was proposed to estimate the surge margin and then the high stability control was realized with the method of augmented LQR.