Simulation Study on Outflow Characteristics of Cryogenic Propellant during Rocket Ascent

Abstract

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.

Keywords

• rocket launch
• cryogenic propellant
• outflow device
• surface collapse
• CFD simulation