Research on high fidelity modelling and optimum designing of an adaptive cycle engine's starting process

An adaptive cycle engine is an evolutional aero-engine that can achieve low fuel consumption and high efficiency by adjusting the thermodynamic cycle; however, few studies have been conducted on adaptive cycle engine performance at low speeds. A high-fidelity ground starting model of an adaptive cycle engine is established by correcting the low speed characteristics of the components, while considering the effects of rotor inertia, volume, combustion efficiency, and the thermal inertia of the combustor and turbine. By employing a physically enhanced prediction method, three operating states of the compressor at low speeds are obtained: compressor, stirrer, and turbine state. The matching mechanism of the adaptive cycle engine and the detailed influence of the variable geometries on the engine's performance during the starting process are explored. The study shows that the third bypass duct has little effect on the engine starting time, and opening the mode select valve can reduce the starting time. Compared with the initial settings, the starting time decreases by 3.98 s after optimization with the variable geometries. The detailed impact of the variable geometries on the engine's starting performance provides an engineering reference value for the control strategies. •A high-fidelity ground starting model of an adaptive cycle engine is established by correcting the low speed characteristics of the components, while considering the effects of rotor inertia, volume, combustion efficiency, and the thermal inertia of the combustor and turbine.•A physically enhanced prediction method based on PSO-SVR for extrapolating the low-speed characteristics of compressors is proposed to solve the problems of low accuracy and discontinuous isentropic efficiency at low-speeds.•The detailed impact of the variable geometries on the adaptive cycle engine's starting performance provides engineering reference value for the optimum designing of adaptive cycle engine start control strategies.