Control law synthetizing for an innovative indirect precooled airbreathing engine under off-design operation conditions

Abstract

Indirect precooled engine (IPE) is a promising power for single-stage-to-orbit (SSTO) and the booster stage of a two-stage-to-orbit (TSTO) vehicles. Thrust of IPE is realized the most decisive factor that affects vehicle mission performance; therefore it is particularly critical to ensure that the engine can fully exert its thrust performance through active control since the flight parameters will change substantially alongside the trajectory. On account of this, control law of maximizing thrust for a single branch IPE is developed in current study. To this end, a high-fidelity off-design model of IPE is constructed to evaluate how engine performance is regulated by the various changeable parameters. The results indicate that engine thrust and specific impulse are functions of total fuel mass flow, nozzle throat area and the temperatures of preburner and main combustor, which can be conveniently controlled in real engines by actuators or changing the related fuel mass flow through fuel valves. Based on the influence characteristics revealed, the maximum thrust control law of the engine is synthetized, with the range of engine thrust can be regulated along a representative flying trajectory is evaluated. The results may provide some useful guidance about performance control of IPE with complex multi-branch intermediate cycles.