Research On Mode Transition Control Of Tandem Turbine Based Combined Cycle Engine

Turbine based combined cycle(TBCC)engine combines the advantages of turbofan engine and ramjet engine.It has a wide flight envelope,and can be used repeatedly.TBCC can take off and land vertically,so it is one of the power devices for hypersonic vehicles.A lot of researches were carried out by domestic and foreign scholars.Based on the mathematical model of TBCC engine,the mode transition control method of TBCC engine is studied in this dissertation.Firstly,the mathematical model of TBCC engine is studied.Based on the mathematical model of turbofan engine,the mathematical model of adjustable inlet is established,and the co-working equations of engine components in different modes are analyzed.The low-speed characteristics of components were expanded based on the exponential extrapolation method.The component-level starting model of combined engine and the starting model of windmill based on neural network are established,and the accuracy of the starting model of windmill is verified.Secondly,the component-level mathematical models in starting mode is adapted to the test data.An improved teaching and learning algorithm is proposed to enhance the accuracy of the starting model.The test data of idle state are adopted to modify the component characteristics of the model of at and above idle state,the accuracy of the model after starting is enhanced.a The starting model is adapted to the test data based on the power difference between turbine and compressor,and the optimization is carried out according to the time segenment,and the accuracy of the starting model is enhanced.Thirdly,the mode transition process of the combined engine is analyzed.The thrust and fuel consumption of the combined engine at different altitudes and Mach numbers are compared,and the working point of the mode transition process of the combined engine is determined.Based on the principle of the minimum thrust fluctuation,the model predictive control method and the improved teaching and learning algorithm are adopted to optimize the mode transition control plan off-line for turbofan to ramjet and ramjet to turbofan transition,and the control target of the mode transition process is determined.Finally,the design of the mode transition controller for the combined engine is studied.Based on the augmented linear quadratic controller,the double-variable control of the afterburning turbofan mode is studied.Based on the optimized control plan,a proportional integral controller is used to control the ramjet mode and the mode transition process.The simulation results show that the controller can meet the performance requirements of the mode transition process.