火箭发动机液氢预冷回路非稳态传热特性研究

Study on Unsteady Heat Transfer Characteristic of Liquid Hydrogen Precooling Loop of Rocket Engine

针对液氢预冷火箭发动机自然循环回路的流动与传热过程,建立了一维非稳态均相模型来研究预冷过程中管路的温降特性.在膜态沸腾阶段引入过渡膜态沸腾,保证了弥散流膜态沸腾向反环状流膜态沸腾的合理过渡.一般流体的膜态沸腾起始壁温TL大于核态沸腾最高壁温TCHF,而氢的TL小于TCHF,使得氢的沸腾曲线不同于其他流体,造成计算时传热与流型转换的不连续,因此考虑以TCHF作为膜态沸腾起始壁温,以TL作为核态沸腾最高壁温,通过增加过渡沸腾区来确保计算顺利进行.计算发现:预冷过程中,回路管壁温沿流动方向表现出从高到低的逆向分布规律,最高壁温点位于反环状流向弥散流过渡区间处,最高壁温点位置随时间逐渐向下游推进.

A set of one-dimensional unsteady homogenous models for flow and heat transfer process of a natural circulation precooling loop of a rocket engine is established to study the cool-down characteristic of the pipeline when liquid hydrogen flows in the pipeline.A transition filming boiling model is adopted to ensure the reasonable transition from dispersed filming boiling to inverted filming boiling.TCHF and TL are viewed as the onset temperature of film boiling and the temperature of critical heat flux,respectively,to achieve the continuity of heat transfer and flow regime transition in the calculation.The computing results show that the inverse temperature distribution exists at the loop along the flow direction during the precooling process.The maximum wall temperature is located at the transition from inverted flow to dispersed flow.In addition,the location of the maximum wall temperature moves downstream with time gradually.