电动膨胀循环液氧甲烷变推力发动机动态特性研究

Dynamic Characteristics of Electric Expander Cycle System for LOX/LCH4 Liquid Variable Thrust Liquid Rocket Engine

电动泵压式液体火箭发动机受到了广泛的关注,然而电池有限的输出功率和过于沉重的质量成为限制电动泵压式发动机发展的重要因素。为此,提出了一种电机驱动燃料泵和涡轮驱动氧泵的电动膨胀循环变推力液体火箭发动机方案,并着重研究了该型发动机的动态响应特性。首先给出了20kN级电动膨胀循环发动机的技术指标和部组件参数,基于AMESim平台建立了全系统动力学模型,验证了方案的可行性和部组件动力学模型的准确性,并深入研究了启动工况和调节工况的动态响应特性。结果表明,针对启动过程而言,涡轮泵调整时间较电动泵长,这降低了系统响应速度,但工况越高,系统响应速度越快;高工况启动时,甲烷在冷却通道内的剧烈相变和跨临界状态的不连续物性相互耦合易引发系统振荡;就调节过程而言,推力调节时普遍存在超调或凹坑现象,且系统在两相同工况之间调节时,正调响应速度快于负调,这也导致阶跃幅值相等条件下的系统调整时间随目标工况升高而缩短。

Liquid rocket engine using motor pumps has received widely attention. However,the limited output power and heavy mass of battery still restrict the development of motor-pump variable thrust engine. Therefore,an electric expander cycle system for variable thrust liquid rocket engine is originally proposed. The electric expander cycle system is characterized by that the fuel pump is driven by motor,while oxidizer pump driven by turbine. The dynamic response characteristics of the system scheme are emphatically studied in this research.Firstly,the technical metrics and component parameters of the 20 kN class electric expander cycle system are given. Then,the whole system dynamic model of the engine is established based on AMESim,and the feasibility of new system and accuracy of dynamic model of component is verified. Finally,the dynamic response characteristics of start-up process and throttling conditions are deeply studied. The results show that:for the start-up process,the response time of turbopump is longer than that of motor pump,which prolongs the system adjustment time. But the response time decreases with the operating condition. Moreover,the coupling of phase change and discontinuous physical properties of trans-critical methane will result in thrust oscillation under high operating condition. For the throttling process,overshoot or pit phenomenon is common in thrust regulation,and the response speed of positive regulation is faster than that of negative regulation when the system throttles between the two same conditions. Further,when the step amplitude is the same,the response time of the system decreases with the increase of the operating condition.