Simulations of Cavitating Flows in Turbopumps

Abstract

Simulations of a cavitating inducer at design flow conditions are reported in this paper. The ability of a Navier-Stokes based, multiphase formulation in modeling the effects of large-scale extensive cavitation on the performance of inducers is demonstrated. The simulations were performed on the Simplex inducer geometry that has been extensively tested at NASA Marshall Space Flight Center. An acoustically accurate, compressible multiphase model that has been previously validated is utilized. The model is implemented within a multi-element unstructured framework that permits efficient grids with locally high resolution near the cavitating zones and in the tip gap region. The simulations were performed at a fixed flow rate with different inflow pressures or net suction specific speeds (Nss). The computational analysis indicates a strong correlation between performance loss and the extent of cavitation blockage and accurately identifies the critical N S S number where breakdown occurs. Predictions of head loss compare well with experimental data. Key insights are provided through a sequence of relevant simulations into the growth of cavitation zones, blockage in blade passages, and change in blade loading as a result of cavitation.