Experimental Investigation of Secondary Flow and Mixing Downstream of Straight Turbine Cascades

Abstract

The purpose of this paper is to investigate the flow field downstream of turbine cascades of low aspect ratio, often used in vehicles and small turbomachines. Experimental investigation was carried out to study the flow downstream of three sets of turbine cascades having the same blade turning angle of about 83 deg but different profiles. The total energy losses were measured at several planes downstream of the cascade of blades in order to determine the changes in gross secondary flow loss coefficient and the growth of the mixing loss with distance downstream. Influence of inlet boundary layer thickness, aspect ratio, and exit Mach number on the nature of the flow at the exit plane of the cascade and total energy loss were studied. The tests were performed with four values of aspect ratio: 1.16, 0.8, 0.5, and 0.25. Some new correlations were deduced that predict energy loss coefficients as a function of distance downstream, aspect ratio, and exit Mach number as well as the upstream boundary layer thickness. The test results compare well with other published correlations.