基于液氮冷源的液态甲烷过冷加注工艺

Liquid methane subcooling and filling process using liquid nitrogen as cold source

针对商业火箭公司对于液态甲烷过冷加注的需求,开展了基于液氮冷源的甲烷过冷加注系统方案设计,并计算得到了不同甲烷流量和液氮压力参数下的过冷器换热面积。为了防止液氮温度过低造成液态甲烷凝结,参考现有液氧和煤油工艺流程,提出2种不同控制策略的甲烷过冷加注系统,并详细对比分析了这2种系统所能实现的6个不同工艺流程。结果表明:基于背压控制的加注系统相比于基于液位控制的系统具有更高可靠性,同时前者能够实现在线实时加注工艺,原因在于其通过控制换热器中液氮压力来保证液氮温度始终高于甲烷冰点。甲烷过冷器换热面积与甲烷加注流量、液氮背压均成正比,在具体工程实施中应当根据加注需要选取合适的加注流量和液氮背压,以减小过冷器尺寸和降低设备制造成本。

In response to the demand of commercial rocket companies for liquid methane subcooling,methane filling systems were designed with liquid nitrogen used as the cold source.Corresponding theoretical calculations under different methane filling flow rates and different liquid nitrogen pressures were also carried out.Referring to the existing liquid oxygen and kerosene filling system,two different control strategies for methane subcooling and filling system were proposed to prevent liquid methane from condensing due to liquid nitrogen.Comparisons between the two systems were made.Six different processes realized by the two systems were introduced and analyzed.Resut showed that,the filling system based on back pressure control was more reliable than that based on liquid level control.At the same time,the former could realize online real-time filling process,because it could ensure that the liquid nitrogen temperature was always higher than the methane freezing point by controlling the liquid nitrogen pressure in the heat exchanger.The heat exchange area of the methane subcooler was proportional to the methane flow rate and the nitrogen pressure.In the specific engineer implementation,the appropriate flow rate and liquid nitrogen pressure should be selected in order to reduce the subcooler size and equipment manufacturing costs.