液氧甲烷膨胀循环变推力发动机系统方案对比研究

当前对液氧甲烷膨胀循环变推力火箭发动机的研制难点和关键技术认识不够清楚,尤其是在大变比推力调节方案方面。基于整个发动机系统,采用理论计算方法,探讨甲烷膨胀做功能力以及变推力调节方案可行性。分别给出了单涡轮系统方案和双涡轮系统方案,首次给出了不同工况下详细的系统状态参数分布,进行了对比分析,并探讨了甲烷做功能力随室压的变化规律。研究结果表明,甲烷做功能力随着室压的减小呈现先减小后增大的趋势,单涡轮和双涡轮系统方案均能够实现大范围推力调节;相比单涡轮方案,双涡轮方案能够更好地保证混合比,且甲烷气体做功能力利用效率更高,氧涡轮和燃料涡轮功率变化范围较窄,涡轮所处环境较为缓和,因此双涡轮系统方案具备一定优势。

A comparative study of system schemes for LOX/LCH4 expander cycle liquid rocket engine

The researches about the LOX/LCH₄ expander cycle throttling liquid rocket engine are rare and its recognition of it is not distinct, especially at the system level. Based on the whole engine system, the theoretical method was adopted to investigate the work capacity of CH₄ and the feasibility of throttling schemes. The single-turbine and double-turbine throttling schemes were given, and the detailed comparison between them was analyzed. The results reveal that CH₄ work capacity decreases at first and then increases with the decrease of chamber pressure. And the proposed throttling schemes are feasible. Moreover, compared with the single-turbine scheme, the oxidizer and fuel mass flows can be adjusted respectively for double-turbine scheme and the mixture ratio can keep constant better. Meanwhile, the work capacity of CH₄ for double-turbine scheme is much higher, the powers of the oxygen and fuel turbines vary in a narrow range, and the turbines work in a more relaxed environment. Therefore, considering the system reliability, the double-turbine scheme is advantageous to a certain extent.