Stratified Two-Phase Flow in Annular Seals

Abstract

The present study concerns the leakage predictions in pressure annular centered seals operating in a two-phase (gas–liquid) smooth stratified flow pattern. In such systems, the liquid experiences centrifugal forces typically 3–4 orders of magnitude larger than the standard earth gravity. Consequently, it is reasonable to assume the liquid is centrifuged toward the stator, leaving the rotor in contact only with the gas. This specific flow configuration is difficult to investigate experimentally, being the rotor–stator clearance of the order of 100 μm. For this reason, a new bulk model based on a two-phase smooth-stratified flow is proposed for leakage predictions. The (external) liquid flow and the (internal) gas one are assumed in laminar and turbulent regime, respectively. The results show that for convenient values of the inlet and outlet pressure loss coefficients, the stratified model predicts mass flow rates in better agreement with experimental data than a standard homogeneous multiphase bulk model.