Cavitation modeling and start⁃up under⁃rated pressure simulation of liquid rocket engine
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摘要:
针对液体火箭发动机氧化剂泵的汽蚀过程,使用入口NPSH(net positive suction head)代替入口压力作为汽蚀发生的判据和入口质量流量的计算方法,并通过模型与试验结果的对比发现以扬程下降1.25%作为断裂汽蚀发生点的模型具有良好的精度。后续开展发动机低于额定入口压力的起动仿真,结果表明:62%及以上额定压力能够正常起动;45%及以下额定压力起动失败,原因是燃气发生器温度过高。主要存在0.4~0.6 s,0.4~0.85 s和0.4~1.2 s三个时间段的严重汽蚀,分别对应氧主阀打开、主涡轮转速的快速爬升和燃气发生器参数波动。氧化剂主泵汽蚀主要影响燃气发生器和推力室,次要影响燃料供应路组件,轻微影响主涡轮。
Abstract:The NPSH (net positive suction head) was used instead of the inlet pressure as the criterion of cavitation condition for liquid rocket engine cavitation process,and the model with the head drop of 1.25% as occurrence point of fracture cavitation had good prediction accuracy by comparing the simulation with the test results.Subsequently,the engine start⁃up simulation was performed.The results showed that the rated pressure of 62% and above can start normally;the rated pressure of 45% and below failed because the gas generator temperature was too high.There were three periods of severe cavitation in 0.4-0.6 s,0.4-0.85 s and 0.4-1.2 s,respectively,correspondingly to the opening of the main oxidant valve,the rapid climb of the main turbine speed and the fluctuation of the gas generator parameters.The cavitation of the oxygen main pump mainly affected the gas generator and the thrust chamber,secondly affected the fuel supply path assembly,and slightly affected the main turbine.
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Key words:
- cavitation model /
- gas generator /
- start⁃up procedure /
- system simulation /
- liquid rocket engine
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表 符号表
A/m2 等效流通面积 ps/Pa 液体蒸汽压 g/(m/s2) 质量场加速度 qm,pin/(kg/s) 泵入口质量流量 H* 无量纲扬程跌落系数 qm,pout/(kg/s) 泵出口质量流量 Cp/(1/m) 流体平动系数 Tf/K 流体温度 ml*/kg 泵内充满时的流体质量 Vc 无量纲空泡体积 n/(r/min) 转速 Δpp/Pa 泵正常工况扬程 N* 无量纲汽蚀余量 Δppc/Pa 泵汽蚀工况扬程 Nc/m 汽蚀余量 η 泵实际效率 Nc,cr/m 临界汽蚀余量 ηh 泵额定工况效率 pp.in/Pa 泵入口压力 ρ/(kg/m3) 液体密度 pp.out/Pa 泵出口压力 ξ/(1/m4) 流阻系数 p/Pa 额定起动压力 表 1 试验工况表
Table 1. Test working condition list
泵型号 试验转速/(r/min) 工质温度/K 工质密度/(g/cm3) Type1 6 459 302.85 1 Type2 5 991 304.05 1 Type3 12 997 301.25 1 -
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