Research On Air Turbo Ramjet Expander Engine Component Matching And Performance Optimization

Air Turbo Ramjet of Expander(ATREX)engine can take off from sea level static(SLS)up to Mach 5 at 30km altitude without model transition,and the ATREX offers high specific impulse and thrust along the flight path,it is one of the most preferable candidates for the hypersonic propulsion systems.The primary work of this thesis is to establish the engine thermal cycle and off-design performance calculation and analysis method,and to lay the foundation for the study of engine regulation laws and components matching mechanism.The establishment of precooled combined cycle engine working fluid model,components model and the engine cycle model are discussed in the beginning of the thesis.The engine working fluid model is built based on the equation of state explicit in Helmholtz energy,and the variable specific heat capacity is considered.The dissociation and combustion reaction in the engine combustor is assumed chemical equilibrium.The precooled air turbo gas generator(ATR-GG)engine,the precooled turbojet engine(PCTJ),the synergetic air breathing rocket engine(SABRE),and the ATREX engine cycle model are established with the consideration of engine components matching constraints.Based on the precooled combined cycle engine numerical model,the effects of combustion product components on engine overall performance at SLS and Ma 5 conditions are analyzed.The performance of the precooled ATR-GG cycle,PCTJ cycle,SABRE cycle and ATREX cycle are compared and analyzed.Parametric analysis of the effects of the compressor pressure ratio,fuel-air ratio and turbine inlet temperature on the engine overall performance.The ATREX key cycle parameters selection rules are obtained,and the engine cycle characteristics are clarified.The adaptabilities of the ATREX to hypersonic propulsion systems are illustrated.The precooler off-design model is built based on the heat transfer effectiveness-NTU(Number of Transfer Units)method,and the precooler's effectiveness varies with the engine operation conditions.The compressor and the turbine off-design performance are obtained by interpolating characteristic maps,and the ATREX off-design model is established based on the components matching constraints.The ATREX engine components design parameters are selected according to the engine parameters selection rules.Based on the ATREX off-design model,the engine regulation rules of increasing the fuel pump pressure ratio and the fuel mass flow,reducing the nozzle throat to increase the compressor pressure ratio along the engine constant rotational speed line is explained.The multi-object genetic algorithm is used to optimize the engine thrust and specific impulse along the flight path.First,aiming at the defects of the NSGA ?(Improved Non-dominated Sorting Genetic Algorithm)algorithm in crowding distance function,the filter function based on the linear distance between the optimize target of each individuals is added to improve the distribution of optimization results.And then,the ATREX multi-object optimization model is built based on the improved NSGA ? algorithm,the engine thrust and specific impulse are selected as the objectives,and the engine rotational speed,turbine inlet temperature and the compressor operation point are selected as the variables.Finally,at given flight conditions the pareto optimal solution is achieved,and at given flight conditions the engine maximum thrust and maximum specific impulse is increased effectively.