Design of thrust augmentation control schedule during mode transition for turbo-ramjet engine

Abstract

A thrust augmentation control schedule was designed for turbo-ramjet engine during mode transition process to achieve high thrust performance. First, a mathematical model of turbo-ramjet engine was established, analyzing the reason for the existence of an insufficient thrust working range under conventional mode transition control schedule. On this basis, a thrust augmentation control schedule was devised for the thrust insufficient range considering the matching between the air inlet available airflow and the engine demand airflow. The control schedule could increase the flow capacity of the engine and reduce the overflow drag of air inlet by opening the ramjet bypass while keeping the turbofan components working at the maximum state, which could improve the maximum installation thrust performance of the engine and achieve a better air inlet/engine matching. By further designing the optimal regulation rule for the rear variable area bypass injector (RVABI), the installed thrust of the engine could be increased by more than 37.93% at most, while simultaneously reducing the fuel consumption by 0.16%. Finally, the turbo-ramjet engine was simulated along the isobaric flight path. The simulation results revealed that under conventional mode transition control schedule, the thrust insufficient occurred when Mach number is above 2.7. The designed thrust augmentation control schedule could effectively improve the maximum thrust of the thrust drop zone and provide sufficient thrust margin for engine during the whole working process. At the same time, considering the smooth thrust and thrust augmentation requirements, a compromise mode transition control schedule between the thrust augmentation control schedule and the conventional mode transition schedule is proposed. This control schedule could address the problem of insufficient thrust at high Mach numbers while the smoothness transition of engine total thrust could be guaranteed.