Influence of Moving End-wall on Tip Clearance Flow in Axial Compressor Cascades

Abstract

A three-dimensional state-of–the-art block structured Navier-Stokes solver has been developed to investigate the complex flow phenomena in the tip gap of axial flow compressor cascades. First, Numerical investigations into a linear compressor cascade have been conducted to analyze the tip leakage flow fields both in stationary and moving end-wall condition. The good agreements between the calculated results and the available experimental data demonstrate the validity of the computations. Both experimental and numerical results indicate that the moving boundary layer entrain and diffuse the tip leakage vortex from the suction surface of one blade across the blade pitch to the pressure surface of the adjacent blade, and the tip leakage vortex with its smaller and tighter core moves closer to the pressure surface of the adjacent blade with a reduction in tip clearance size. Then, numerical analysis is carried out to investigate the moving end-wall effects on tip clearance flow in the stator of a subsonic one-stage axial flow compressor. It is found that the corner separation region on the blade suction surface diminishes remarkably under moving endwall condition. The high loss region, which is located at the corner of the inner wall and blade suction surface under stationary endwall condition, contracts and extends toward the pressure side of the adjacent blade, and the loss level associated with the leakage vortex core decreases under moving endwall condition. These changes will result in a reduction in passage losses with a corresponding reduction in overall blockage in the passage, which is favorable not only to raise the efficiency, but also to improve the stall margin of the compressor.