Research on Optimization Technology of Minimum Specific Fuel Consumption for Triple-Bypass Variable Cycle Engine

This paper investigates the best control method of the lowest specific fuel consumption (SFC) to reduce the specific fuel consumption of the triple-bypass variable cycle engine. Specific fuel consumption is the ratio of fuel flow to thrust. First, the Kriging model of the engine near the supersonic cruise and subsonic cruise state points was extracted using the component-level model of the triple-bypass variable cycle engine, and the PSM was obtained close to the steady-state point. The contribution of each control variable to the engine’s specific fuel consumption was computed using the PSM and, at the same time, due to the linear characteristics of the PSM, it was easy to deal with various constrained linear optimization problems, and the steady-state points with the smallest specific fuel consumption under the constraints could be obtained through the linear optimization algorithm; however, the surge margin and pre-turbine temperature of the optimized point were limited in the optimization process, the method of direct switching inevitably brought the problem of overshoot of the controlled quantity, and the actual controlled quantity could still exceed the safe operation boundary of the engine in the process of change. Moreover, the performance optimization control itself is premised on sacrificing the surge margin of the engine, and its operating boundary is closer to the surge line, so the limitation protection problem in the transition state cannot be ignored in the process of performance optimization control. In this paper, a multivariable steady-state controller was designed based on Model Predictive Control (MPC) to meet the needs of engine optimization control mode switching. The simulation results of the supersonic cruise mode show that the minimum fuel consumption control can reduce the fuel consumption of the engine by 2.6% while the thrust remains constant.