Numerical investigation of two-phase fluid-transient induced cavitation in the cryogenic propellant feedlines

Abstract

Rapid changes in fluid-flow conditions, whether purposeful or accidental, may result in generation of a pressure surge in the fluid handling equipment followed by oscillations of pressure, which is known as the fluid transient (or fluid hammer). Fluid transient occurs very often during the filling of the dry liquid lines as well as during the valving operation in the cryogenic propellant feed systems. The maximum amplitude of fluid transient induced pressure oscillations may exceed the strength of the material, which results in the rupture of the flow components. Sometimes, due to its oscillatory nature, when the pressure wave amplitude falls below the vapour pressure of the fluid it may lead to cavity generation resulting in two-phase fluid transients. The pressure generated due to the collapse of the cavity will be higher than the pressure in the single-phase fluid transients that may lead to the structural failure of the fluid handling equipment.In this study, a one–dimensional numerical model has been proposed using the Method of Characteristics (MOC) scheme to investigate the fluid transient induced cavitation due to sudden closure of the valve in the propellant feedlines. Different two-phase models namely Discrete Vapour Cavity Model (DVCM) and Discrete Gas Cavity Model (DGCM) have been used to predict the vapour volume in the pipe. The applicability of the developed model has been evaluated by validating its predictions with the results available in the literature. It has been observed that both the models are in good agreement with experiments, but DGCM can be preferred due to its ability to handle larger void fractions as compared to DVCM.