Study on the optimization design of a civil turbofan engine

This work presents an optimization design process for a high bypass unmixed turbofan engine. The optimization design process contains a constraint analysis model, a mission analysis model, an engine cycle parameter optimization model, an engine performance model and an emission prediction model. The constraint analysis model is provided to establish the relationship between thrust to weight ratio and wing loading at takeoff. The mission analysis model is adopted to calculate the aircraft takeoff weight, the maximum thrust at takeoff and the required thrust in cruise. The engine cycle parameter optimization model is based on the self-adaptive three times variation differential evolution (STTVDE) which is developed from the differential evolution algorithm to find the engine cycle parameters minimizing the specific fuel consumption in cruise. The high compressor exit temperature limit, combustor exit temperature limit, engnine size, engnine weight and turbine expansion ratio as well as required thrust in cruise and takeoff which calculated from the constraint analysis and the mission analysis are used as constraint parameters in the engine cycle parameter optimization model. The emission prediction model is used to calculate the landing takeoff (LTO) emission cycle for NO_x, CO and UHC based on Boeing fuel flow methodology and T₃-P₃ methodology. The engine performance model and the mission analysis model are employed to calculate the fuel consumption in the flight mission when engine cycle parameters are determined. Finally, five optimization cases are to be optimized, and their fuel consumptions are compared with each other in the mission analysis model.