Abstract: In order to understand the working performance in the hot water rocket motor better，a numerical model of the flow field of hot water rocket motor was established and then the unsteady working process was simulated.And the numerical model was validated via comparing with the experimental data. According to the study of the working process of the motor，it is found out that in the working process，phase change process is slow in the main body while it is severe in the nozzle，so the gradient of vapor volume fraction in the nozzle is larger.The closer to the nozzle exit，the greater the vapor volume fraction，vapor volume fraction at the exit is above 90%，and the lower the temperature.The pressure in the motor firstly drops to the saturated pressure corresponding to the initial temperature and then decreases slowly.And the working process are divided into three stages，which are initial segment，middle segment，and a trailing segment.Total?impulse of the motor is mainly concentrated in the middle segment，which is about 70% above of total?impulse.

Key words: Hot water rocket motor；Two-phase flow；Flash evaporation；Numerical simulation

摘要： 为了更好地了解热水火箭发动机的工作特性，建立了热水火箭发动机内流场的数值计算模型，对发动机非稳态的工作过程进行模拟，并与实验数据对比进行验证。通过对发动机工作过程的研究，发现在发动机工作过程中，喷管之前相变较缓慢，而在喷管中相变比较剧烈，从而使得喷管部分的气体体积分数梯度较大，越靠近出口，气体体积分数越大，出口气体体积分数高达90%以上，其温度越低。发动机内部压力首先急剧降到初始温度对应的饱和压强，然后缓慢降低。把热水火箭发动机的工作过程分为三个阶段:初始段、中间段和拖尾段。发动机的总冲主要集中在中间段，约占总比冲的70%以上。

关键词: 热水火箭发动机；两相流；闪蒸；数值模拟