Investigation on the impact of variable geometry components on the matching characteristics of a three bypass adaptive cycle compression system

The three bypass adaptive cycle engine enables the successful execution of missions encompassing a wider flight envelope by appropriately adjusting the variable geometry components. This study investigates the impact of adjusting variable geometry components on the matching characteristic and internal flow patterns of the compression system. Numerical simulations demonstrate that the reduction in the opening of the core fan guide vane significantly decreases the pressure ratio and flow rate of the core fan, leading to a shift in the operating point of both the rear fan and high-pressure compressor towards stall boundary. Additionally, decreasing the opening of the variable area bypass injector (VABI) moves the operating point of upstream components closer to stall boundary while pushing downstream components towards blockage boundary. To enhance stall margin during core fan guide vane closure, it is recommended to appropriately close the third and second VABIs. By closing the core fan guide vane by 30° and simultaneously opening inter-stage turbine burner, total bypass ratio changes from 3.05 to 3.41 at subsonic flight to 0.32–0.56 at supersonic flight. In turbojet mode, enhancing throughflow capacity and efficiency of fans can be achieved by opening the front fan outlet stator as it eliminates blockage caused by second-stage stator.