Thermodynamic effects on the cavitation flow of a liquid oxygen turbopump

摘要

Cavitation is a severe problem in rocket turbopumps. As for turbopumps with liquid oxygen, it exhibits notable thermodynamic effects during cavitation, leading to complex flow characteristic. In this study, to assess the influence of thermodynamic effects on the cavitation flow in a liquid oxygen turbopump, the entire flow passage was numerically simulated using the shear stress transport k-omega turbulence model and a thermodynamic model based on the Zwart-Gerber-Belamri cavitation model to couple the physical parameters with temperature. The numerical schemes were validated using available experimental data. Numerical results show that cavitation primarily occurs at the leading edge of the suction surface of the inducer inlet and at the head of the central blades of the impeller inlet. The thermodynamic effects notably decrease the vapor-phase volume fraction of the cavitation zone at the low cavitation number of sigma = 0.07, but increases it at high cavitation numbers. Moreover, the hydraulic loss in the turbopump was mainly distributed in the impeller-inducer and diffuser. A novel entropy analysis reveals that the thermodynamic effects reduced the dissipation losses generated by the velocity gradient and increased the hydraulic losses induced by the temperature gradient in the wall region. The present study can provide a theoretical reference for improving the hydraulic-instability induced cavitation flow in liquid oxygen rocket turbopumps.