Numerical Analysis of Compressible Flow in Labyrinth Seal

Abstract

Numerical simulation code for compressible flow based on OpenFOAM-1.6 was developed to compute a high Mach number flow. Total enthalpy transport equation was solved to calculate temperature and a flow around a rotor was solved in whirling rotating frame to predict a hydraulic force on an eccentric whirling rotor. Straight and high-low labyrinth seals were simulated by the developed code and numerical results regarding hydraulic force were compared with experimental ones to validate the prediction accuracy. The non-diagonal component of spring constant was predicted well, but the diagonal component of damping constant was largely under-predicted. The maximum and minimum pressures were observed at the circumferential positions of 270° and 90° respectively in inlet region of the straight labyrinth seal. Therefore large hydraulic force in the whirling direction was generated. On the other hand, the maximum and minimum pressures were observed at 180° and 0° respectively in the high-low labyrinth seal. Therefore the hydraulic force in the whirling direction was lower than that of the straight labyrinth seal. Pressure distribution in the circumferential direction was uniform in a large clearance region surrounded by two fins in the straight labyrinth seal, where the hydraulic force in whirling direction was largely decreased.