Effects of Clearance on Leakage Flow Characteristics of Labyrinth Brush Seal

Abstract

To analysis the effects of clearance on labyrinth brush seal in a gas turbine, the leakage flow characteristics and distribution on rotor surface, bristle pack free height and fence height were numerically analyzed using Reynolds-averaged Navier-Stokes (RANS) solutions coupling with a non-Darcian porous medium model. The reliability of the present numerical method was proved, which were in agreement with the experimental and numerical results from literatures. Five sizes of bristle pack tip clearances (0, 0.1, 0.2, 0.3, and 0.4 mm) under different pressure ratios, and other operating conditions were utilized to investigate the clearance modification on the labyrinth brush seal dynamic behaviors which were compared with the corresponding labyrinth seal. The results indicate that at the same pressure ratio the increase of clearance size between the bristle pack and rotor surface will lead to leakage rate rise. More over, at the same clearance and pressure ratio the flow fields in labyrinth brush seal are more complex than labyrinth seal, and the leakage rate of labyrinth brush seal is significantly less than labyrinth seal. The leakage flow pattern, static pressure, and velocity in the labyrinth brush seal and labyrinth seal was also illustrated.