System scheme design of electric expander cycle for LOX/LCH4 variable thrust liquid rocket engine

Abstract

With the development of both cryogenic and motor pump technologies, the cryogenic variable thrust liquid rocket engines that using motor pumps have gained considerable attention. However, the heavy battery limits its performance if engine operates for high thrust. To address this challenge, the electric expander cycle system scheme for variable thrust liquid rocket engines is creatively proposed and designed. Subsequently, the system parameters are calculated based on mass and energy conservation with chamber heat transfer considered. As well, the distribution of this novel system state parameters is investigated. Further, a comparison is conducted between the electric expander cycle system, electric pump, and expander cycle systems. The comparison results demonstrate that this innovative system scheme has advantages of simple structure, low battery mass, convenient throttling, and high reusability. The system state parameters distribution indicates that the feed system can achieve the propellants' pressurization requirements throughout the designed 5:1 throttle range, which suggests the feasibility of this system scheme. Moreover, although the proposed system requires more battery power than does the turbine, the turbine power proportion in the entire system increases with thrust. However, the turbine efficiency drops steeply with a decrease in thrust, whereas the double pump efficiency presents a narrow variation range.