Effect of Rotor Solidity on Stall Inception and Growth in Axial Flow Fan

Considering the consequences of aerodynamic instabilities in the compressor on performance of gas turbine engines, serious study of these phenomena, like rotating stall and surge, is very important. Full numerical modeling of these complex phenomena is very difficult and experimental validation and tuning is necessary to build confidence in the numerical tools. Considering the fact that a lot depends upon the specific details of the compression system (design philosophy, blade to blade variations, tip clearance, axial gaps, solidity etc) it has been difficult to draw generic conclusions. Nonetheless, in order to use the advances in active control technology for effective compressor control there is a need to enrich the knowledge base in this field. Effect of one of the important design parameter i.e. rotor solidity on compressor instability is done in the present study. A single stage axial flow fan was used for the same with 18 bladed and 9 bladed rotors. Simple instrumentation, in the form of a dynamic pressure span wise rake with one per rev and one per blade proximity sensors, was employed keeping practical installation on aero-engine in mind. Results are presented for both the rotors and comparison is made in order to study the effect of solidity on stall inception and growth process, which in the present case, is very significant. Results obtained clearly show the usefulness of simple instrumentations employed on the complex phenomena such as rotating stall.