Numerical Simulation of Oxygen Jet Condensation in Cryogenic Liquid Rocket

Low frequency pressure fluctuation is an important topic on the stable and safe working of the system. As the excitation source of the pressure fluctuation, oxygen injection condensation is the indispensable process in the pipeline system of liquid fuel aircraft. Due to the intense mass transfer and flow instability, it is difficult to capture the accurate pressure characteristic of oxygen jet condensation, especially in the first main frequency of pressure oscillation. Aiming at the mechanism and excitation process of pressure oscillation, a numerical simulation is carried out using a modified mass transfer model. The height function method is implemented to calculate the curvature of gas–liquid interface. It can update the mass transfer rate in real-time, which is the core technology to evaluate the pressure fluctuation. The modified model is verified by a water steam jet condensation simulation and the numerical result agrees well with the experimental data. The low-frequency pressure fluctuation characteristic is obtained successfully. The first main frequency is 9.5 Hz with the apparent amplitude of approximately 80 kPa. The research shows that the periodic mass transfer rate and the swing of the continuous oxygen gas plume are the key factor causing the low frequency pressure oscillation. There is an oxygen suck-back flow phenomenon in the oxygen chamber of condenser pipe. In addition, it is also found that decreasing the injection area can restrain the pressure oscillation effectively. These conclusions provide a theoretical guidance for overcoming the low-frequency pressure oscillation eventually.