Secondary Flow Measurements in a Compressor Cascade Using 3D LDA/PDA: Part A — Flow Topology and its Numerical Representation

Abstract

A three-dimensional flow in a high speed (Main = 0.7) linear compressor cascade’s end wall region is presented in this paper. The attached blade geometry is of medium curvature with a deflection angle Δβ = 15°. To intensify the secondary flow structure the profiles were stalled deliberately and oil flow visualization was used to prove the presence of that hub-corner stall. Together with streamlines derived from velocities, measured by a three-channel laser Doppler anemometer (LDA), that allowed the identification of the secondary flow region’s key features and their extents into the flow field. A therefrom-derived topology is then compared to existing concepts. Moreover, an associated URANS simulation is set up using the k–ε model to verify its capabilities to reproduce the measured flow field. To confirm the previous observations the stall indicator is computed from the simulation results. It is further shown that the hub-corner stall dissolves when removing the side wall boundary layer. In summary, this paper combines elaborate laser Doppler measurements at both high Reynolds and Mach numbers combined with verified simulations allowing a detailed description of the end wall behavior within the cascade and further introduces a new flow topology concept.