CFD modeling of multiphase flows in the gas turbine engines oil cavities

Abstract

The choice of the structure of the mathematical model of thermal-hydraulic processes in the oil cavities of the GTE rotor supports has been substantiated. A three-dimensional CFD model has been built to calculate multiphase currents involving information on the flow distribution and heat exchange given in the scientific literature. We have considered the approaches and individual models used for these purposes. The resulting solutions are consistent with the results of the experiment on a model support and generally accepted ideas about the processes in a given class of devices. The distribution of oil in the chamber, the phase current lines, the temperature and velocity fields have been given, as well as the velocity vectors for various CFD models (VOF, Euler, Inhomogeneous) and solver types (steady and non-steady). Based on the analysis of the results obtained, it has been found that the Euler model involving a non-steady solver yields the smallest difference with the experimental values for a heat transfer coefficient. In all cases, when gravity is considered, there is an asymmetrical distribution of the oil film. The result is a change in the thermal resistance of the boundary layer and, consequently, in the heat transfer coefficient along the bearing chamber circumference. This largely determines the heat flow through the chamber wall. The proposed method of modeling workflow in the support's oil cavity is based on a mathematical notation of the heterogeneous monodisperse oil-air flow with an algorithm of inversion of the structure of two-phase flow in the near-wall region from the drip into the bubble. That makes it possible to more accurately calculate the temperature states of the GTE rotor support elements and the system that ensures the proper operation of the bearing by correctly determining the heat transfer coefficient on the part of the oil-air mixture. The constructed model makes it possible to numerically investigate the applicability of those known and to derive the new correlation dependences for the mean value of aheat transfer coefficientin the oil cavity of rotor support that is used in engineering calculations. The model also makes it possible to numerically investigate the impact of the geometry, the rotor rotation frequency, and the phases flow rates on heat output in the oil cavity.