Evaluation of the effects of interfacial tension forces in homogenous equilibrium mixture modeling of a cavitation flow of liquefied natural gas inside a Laval nozzle

Abstract

Achieving the robust performance in turbomachinery equipments including the modern liquefied natural gas (LNG) fuel pumps, is highly dependent on prediction of cavitating patterns and control of consequent cavitation damages. In most studies to date of cryogenic cavitation, effects of vapor-liquid interfacial tension on the onset and development of transient cryogenic cavitation have not been addressed sufficiently. This is of more interest when it comes to numerical homogenous equilibrium mixture (HEM) modeling of cavitation where vapor fraction field is calculated through appropriate weighting functions, as opposed to that in transport-equation –based modeling, known as TEM approach, where separate transport equation is introduced for calculation of vapor phase fraction. In the present work, a HEM-based cryogenic cavitation solver is employed to examine the interfacial tension effects on the phase-change behavior of LNG inside a Laval nozzle. Based on the theoretical considerations and comparison of the results with available literature data, it is concluded that the presence of interfacial tension forces in the in-nozzle cavitation LNG flow can potentially stabilize cavitating patterns through modifying the local phase-change incidents. The net LNG vapor production in the nozzle is however observed not to be largely affected by the interfacial tensions, suggesting the pre-dominance of temperature-dependent inertia and advective forces in modulating LNG phase-change processes. Counting the calculations of interfacial tension forces in the cavitation solver is also found to improve accuracy of the modeling against the experimental data.