A Two-Phase Flow CFD Model for Predicting Rotordynamic Performance of Annular Seals During Laminar-to-Turbulent Transition

Abstract

This work uses a computational fluid dynamics (CFD) model to predict the leakage and rotor-dynamic coefficients of a smooth annular turbomachinery seal operating with bubbly two-phase flows for gas volume fractions up to 10%. An experiment was first performed to determine the critical Reynolds number for bubbly two-phase pipe flows. It was found that small gas volume fractions (below 1%) caused the critical Reynolds number to drop as low as 1000. A liquid CFD model was then developed to model liquid flows, and implemented in a 2D Euler equation solver. A quasi-steady CFD method was then used to predict the rotordynamic force coefficients of the seal, making it possible to compute the reaction forces on the rotor using steady CFD simulations. The homogeneous mixture model and the Eulerian model were used to model the two-phase flow. Overall, the CFD leakage and rotordynamic coefficients better matched the experimental data than the bulk-flow model, but with greater computational cost.