An experimental study of reverse compound lean in a linear turbine cascade

Abstract

This paper describes a detailed experimental investigation into the effects of reverse compound lean (RCL) in a highly loaded axial turbine cascade. The geometry was designed using fully three-dimensional viscous CFD calculations to achieve a reduction in secondary flow. Traverses were made upstream and downstream with three-hole and five-hole probes to quantify the effects on the flow and losses produced by the leaned blade compared with a prismatic blade. These measurements were supplemented with blade static pressure measurements and surface flow visualization. It was found that the RCL blade produced higher overturning at the end-wall accompanied by higher secondary loss but this was constrained closer to the end-wall. Near mid-span, the turning was reduced slightly but the overall turning for the row was unaltered. The mid-span showed much less loss, so that overall the loss was reduced by 11 per cent. An understanding of these effects may be gained by consideration of the three-dimensional effects produced by the RCL.