The Instability Control Of Aeroengine Based On Backstepping

As an important part of aeroengine,axial flow compressor is able to provide high pressure air for combustor.In recent years,axial flow compressor is constantly developing towards high pressure ratio,high efficiency.However,the phenomenon of aeroengines instability which is rotating stall and surge has been limiting the improving of compressor performance.When rotating stall occurs,the engine's thrust will be greatly reduced and the rotating air may fracture the blades within the compressor channel;when the surge occurs,the substantial oscillations of the flow can cause the engine to explode in a short time.It can be said that the instability of aeroengine brings great risks to the safety flight of aircraft,thus more and more attention has been paid in rotating stall and surge control.Chapter 1 briefly introduces the structure and operating principle of axial flow compressor,and describes the progress of the compression system the model,as well as some control methods of rotating stall and surge.In chapter 2,compression system model has been deduced when the speed of compressor rotor is variable.If the speed of the rotor is constant,the model will degenerate into the MG model.when a closed control valve(CCV)is introduced in the outlet of the compressor,a MG model with CCV can be got.Since MG model is the basis of this thesis,it has been simulated in this chapter.Nonlinear dynamics has been done on MG model in chapter 3.We explain the mechanism of surge and rotating stall phenomena and summarize the situation when the compressor systems are stable or unstable through bifurcation of MG model.The bifurcation results allows us a more intuitive understanding of MG model which will provide ideas for rotating stall and surge control.Backstepping has been used to control the instability of aeroengine in Chapter 4.First,surge and rotating stall controller are designed using the CCV as actuator.Then,surge controller is designed using the throttle valve as actuator.Finally,the controllers are simulated in Matlab.Finally,the results of the dissertation are summarized and further research topics are pointed out.