PIV Investigation of the Flow Field in a Transonic Compressor Cascade with a Moving Shock Wave

Abstract

The unsteady flow field produced during the interaction of a shock wave with stator blades is investigated in a linear cascade using particle image velocimetry (PIV). The study investigates the interaction that occurs when shock waves traveling with the rotor blades in axial transonic compressors interact with upstream stator blades. This interaction produces unsteady phenomena such as vortices and separation that induce blockage and losses. Flow visualization and PIV data, synchronized with shock-wave-passage locations provide details of the flow field in various areas of the cascade passage. The experiments are conducted in a transonic blow-down wind tunnel with a nominal inlet Mach number of 0.65. A single moving normal shock is generated using a shock tube external to the wind tunnel, and this shock is introduced at the exit of the stator cascade to simulate the bow shock from a downstream rotor. PIV instantaneous measurements are made for three different shock strengths at various regions of interest and are synchronized with various instants of the shock passage. In each case, the passing shock induces a vortex of varying size and strength around the trailing edge of the stator. The flow pattern includes the disruption and recovery of the transonic free stream, shock waves, vortex flow, vortex blockage, suction-side separation, spiraling arms, secondary vortices, and endwall clearance flows.