Improved tip leakage flows for reduced losses

A combination of experiments and CFD looking at the details of the flow in the tip clearance region. By studying the flow in the tip gap region it is hoped to produce improved blade profiles for reduced losses and extended stall margin. 

The tip clearance regions of both rotor and stator (canterlevered) blades in an axial compressor are region of high loss.  Furthermore, the rotor tip clearance region is thought to have a controlling influence over the stability of the compressor.  Detailed experimental studies have been carried out in a four-stage low-speed compressor looking primarily at loss profiles and double leakage in the region of the tip gap of the neighbouring blade.  Hot-wire measurements and five-hole probe data have been used to assess the flow characteristics in the tip region of various blade profiles.

The ultimate goal of this work is to develop blade tip profiles, for rotors and stators, which will routinely give better loss management, and improves stall margin.

The performance improvements expected from this work are statistically very small, but small improvements in loss reduction in each blade row in a multi-stage compressor are worth having – particularly in cases where compressor efficiency is already high and the power transmitted through the compressor is large.