Effect of Axially Non-Uniform Rotor Tip Clearance on the Performance of a High Speed Axial Flow Compressor Stage

An axially non-uniform type of rotor tip clearance was conceived and tried on a single stage compressor. This concept is based on the advantages of a smaller tip clearance in the front portion of the blade and a larger clearance in the rear portion which allows a higher tip leakage flow to interact with the passage secondary flow, casing wall boundary layer, separated flow on the blade suction surface and the scraping vortex, which are more prominent at the rear portion of the blade. Experimental results indicated that an axially non-uniform clearance can provide improved performance of a compressor stage. Providing the tip clearance in the compressor casing instead of at the blade tip indicated certain advantages. An ‘optimum’ value of rotor tip clearance was noticed for this compressor stage, both for axially uniform and axially non-uniform clearance.