Impact of population balance modeling on the prediction of cryogenic cavitation in aerospace propulsion systems

摘要

The present work aims to investigate the influence of bubble size distribution and nucleation on the modeling of cryogenic cavitating nitrogen flow on hydrofoils. The Eulerian homogeneous mixture approach has been used, consisting in a mass transfer model which is based on the combination of a two-phase incompressible unsteady solver with a Volume of Fluid (VOF) interface tracking method. The interfacial mass transfer rates have been computed by means of an extended Schnerr-Sauer model based on the Rayleigh-Plesset equation. Thermal effects have been introduced by means the activation of the energy equation and the latent heat source terms plus an optional convective heat source term. The dependency of the saturation conditions to the temperature has been defined by means of Antoine-like equations. Based on the Classical Nucleation Theory (CNT), the homogeneous nucleation has been introduced in combination with the transport, the coalescence and the breakup of the nuclei, by coupling the Population Balance Equation/Extended Quadrature-Based Method of Moments (PBE-EQBMM) with the CFD model. The PBE model provided the prediction of the fields of the nuclei density and the nuclei diameter, which affect directly the vapor production/destruction rates predicted by the CFD model. Results showed that the nucleation model alone produced a reduction of the temperature drop inside the vapor cavity, and a warming of the wake downstream the vapor cavity. By implementing the models of the coalescence and the breakup of the nuclei, the vapor cavity and the nucleation region extended consistently, due to the increased number of nuclei both in the wake and inside the vapor cavity, where a reduction of the nuclei diameter was also estimated.