火箭升空低温推进剂出流特性仿真研究

Simulation Study on Outflow Characteristics of Cryogenic Propellant during Rocket Ascent

运载火箭升空期间,确保主发动机工作时不夹气的液体推进剂足量供应至关重要。本文针对升空过载下火箭燃料箱出流装置的工作特性与设计要求,建立CFD模型,就不同工况下输送管出现气体时对应的剩余液体量进行数值仿真与对比研究,研究因素包括:出流口是否采用锥角过渡、出流口上方是否布置隔板及隔板几何结构、出流口设置过滤器等。结果表明:采用锥角过渡,可显著降低不可用液体推进剂,最佳锥角约为30°;布置隔板有利于低温推进剂纯液相供给,且存在最优的隔板高度和长度;球壳型隔板可使不可用推进剂进一步减少约0.25%;出流口设置过滤器可拦截固体杂质及大气泡进入输送管;相较于液氧,液氢表面张力维持气液界面稳定性的能力更差,对出流结构的优化设计要求更高。

At the rocket launching stage,it is very important to supply sufficient and vapor-free liquid propellant to maintain the functioning of the main engine.Considering the working characteristics and design requirements of the outflow device of the cryogenic propellant tank,a computational fluid dynamics model is developed to simulate the outflow features and to compare and analyze the residual liquid quantities during the appearance of gases in the pipe in different conditions.The major factors include whether the outlet adopts a conical angle transition,whether the baffle is arranged above the outlet,whether the outlet is equipped with a filter,and the influence of the geometric structure of the baffle.Results show that the quantity of unusable liquid propellants can be significantly reduced by using cone transition,and the optimum cone angle is approximately 30°.The optimal arrangement of the baffle including its height and length is beneficial for adequately supplying the pure liquid cryogenic propellants.The spherical shell baffle can further reduce the quantity of unusable propellants by approximately 0.25%.The outlet filter can intercept solid impurities and large bubbles into the conveyor pipe.Compared with liquid oxygen,the surface tension of liquid hydrogen is inferior with respect to maintaining the stability of the gas-liquid interface,and the optimal design of the outlet structure has more rigorous requirements.