Investigation of the Shear Flow Effect on Secondary Flow and Losses in a Low Speed Axial Flow Compressor Cascade

Abstract

This paper explores the effect of a prescribed intense shear flow on the flow structures in an axial flow compressor cascade. An approximate shear flow is generated in the test section of an open circuit cascade wind tunnel by using a planar grid of parallel rods with varying solidity. To study only the effect of shear, a compressor cascade based on NACA65 series with a relatively low camber was chosen. The cascade was analysed experimentally as well as computationally (using ANSYS Fluent). The computational results of the cascade were compared with the available measured data. The results agreed well with the experimental data. Detailed analysis of the numerical results was then carried out to explore the complex flow features caused by the shear flow in a cascade. With uniform flow, the secondary flow was found to be negligible from experiments as well as from the computations. Therefore, in an attempt to amplify secondary flow, a shear flow generator was placed upstream of the cascade. Experiments showed quite contrasting results with shear flow, as compared to the uniform flow, in terms of the wake loss. Numerical analysis revealed the formation of vortices in the wake of the cascade due to secondary flows caused by the incoming shear flow and other interesting flow features.