Experimental Investigation on the Layout of Tip Clearance for an Axial-Flow Compressor Rotor

Abstract

The effects of clearance levels, stepped tip gaps and non-axisymmetric tip gaps on the performance of a subsonic axial flow compressor rotor were experimentally investigated at two different speeds. Twelve casing geometries were examined consisting of different clearance level and step profile, as well as the circumferential non-uniform clearance variation. For the small clearance level, both forward and aft stepped tip gaps were found to improve rotor pressure ratio, efficiency and stall margin at two speeds. For the medium and large clearance levels, by comparing with the baseline the benefits of stepped tip gaps were not noticed for all rotor operating conditions. Furthermore, non-axisymmetric clearance distribution on the basis of effective stepped tip gaps still leads to the degradation of rotor performance. Decreasing the wavelength of the clearance non-uniformity deduces the influence of clearance asymmetry on rotor performance.