Visualization of Flow Field in Circular Cascade Having Rotating Stall Suppressed by Tip Injection with PIV

Abstract

Tip injection, fluid injection upstream from a compressor airfoil tip, to a low-speed centrifugal compressor was investigated experimentally to visualize flow fields using PIV. PIV measurements reveal flow fields at the tip and mid-span of circular cascade channel with and without tip injection. With or without tip injection, tip injection does not affect the flow field at mid-span region under both design point and near-stall point of compressor operation condition. With tip injection, the jet controls the flow around the tip region by changing the flow direction from circumferential to radial as an airfoil passes the injector, and rotating stall is suppressed completely for the entire flow passage of the compressor.