Abstract: To study the flow characteristics of gas replacement process in the cryogenic propellant loading system for novel spacecraft propulsion systems， numerical modeling method was adopted to simulate the flowing process of replacement gas. The effects of the operating pressure of self-pressurized liquid tank and the opening of gas control valve on the flow status， flowing rate and pressure adjustment were analyzed. The flow characteristics of the system with replacement medium GH2 and GN2 were then calculated to analyze the similarity between them of gas replacement process. The results show that the influencing factors and trends for the pressure control of nitrogen system are similar to those for hydrogen system. However， the maximum velocity in the hydrogen system can be 5 times higher than that in the nitrogen system under the operating conditions with the same pressure of liquid tank and the same opening of control valve. Thus， for safe operation of the hydrogen system， the accurate adjustment strategy of hydrogen system should be supported by further measurement work on the gas replacement with hydrogen.

Key words: Cryogenic propellant；Loading system；Gas replacement；Similarity analysis

摘要： 为了研究新一代航天推进系统低温推进剂加注系统的气体置换流程特性，采用数值模拟的方法，对置换介质的流动过程进行了模拟和分析，重点考察低温液体增压罐的工作压力、气路调节阀开度对于系统中流动状态和流量及压力调节的影响，并分别以氢、氮作为介质对系统内的流动特性进行计算，分析置换过程中流量调节的氮氢相似性。结果显示，氮气置换系统所得的流量压力调节规律与氢气置换系统在影响因素和变化趋势方面是相似的；但是，在相同的液体储罐增压工作压力和调节阀开度下，氢气系统内的最大流速可达氮气系统内最大流速的5倍，考虑到氢气系统的安全性要求，精确的流量调节策略还需要根据实际氢的置换测试结果来进行确定。

关键词: 低温推进剂；加注系统；气体置换；相似性分析