Mathematic Model And Performance Optimization In The Transition Section Fro Turbine Based Combined Cycle Engine

Because of the excellent performance， Turbine-Based-Combined-Cycle (TBCC)is usually considered as one of the most suitable engine for the first stage oftwo-stage-to-orbit (TSTO) reusable launch vehicle (RLV). It is important to buildengine model， analysis engine characteristic and optimizes engine performance.The advantages and disadvantages between the engine combined in parallel and theengine combined in series is analyzed. According to the application background， theengine combined in parallel is chosen the research object.The thermodynamic model for turbofan engine is set up and the control law isselected. On this basis， the steady performance model of turbofan engine is built inaccordance with the thermodynamic equilibrium equations when the engine is stabilizedand the engine performance curve is given. Compared with the performance of turbofanengine without afterburner，the turbofan engine with afterburner is chosen. Meanwhile，the model and performance curve of ramjet is given by the same method.The flight path and the Mach number changing mode is given to ensure the flightcondition in transition phase. Then the performance model of engine in transition phaseis built according to the model of each engine and the working condition in transitionphase and the thrust curve and the specific fuel consumption curve are draw.To avoid the thrust decreasing suddenly to affect the flight performance and tap thepotential of engine， the performance of engine is optimized by sequential quadraticprogramming (SQP)， and maximum thrust of ramjet is chosen as the optimizing index.The optimize result is great and the problem is solved.