Numerical simulation of flow field in nozzle of hot water rocket motor

In order to deeply understand the working performance in the hot water rocket motor, a numerical model of the flow field in the nozzle of hot water rocket motor is established. And the numerical model is validated via a sample case. According to the study of the flow field in the nozzle of the motor, it is found out that the pressure firstly drops to the saturated pressure corresponding to the initial temperature in the convergent section and then continuously decreases along the axial direction. Besides, the phase change occurs at the nozzle throat, where the main flow would change into a two-phase flow, and vapor volume fraction at the exit is over 99%. Then, the two-phase flow is transferred from a subsonic condition into supersonic flow after the throat because of the changing of sound speed. The flow process in the nozzle can be divided into three steps, which are single-phase flow step, flash evaporation step due to pressure derease and expand-accelerating step, respectively. Though it was similar to the conventional chemical rocket motor, it had a certain complexity because of the phase change.