Methods of Desensitizing Tip Clearance Effects in Turbines

摘要

This study is an attempt to reduce the effect of the leakage vortex in axial flow turbines. A 3D Navier-Stokes CFD solver with two equation turbulence modeling was used to compute the flow through an axial flow turbine with modified blade tip designs. The three modified blade tip designs each involved adding a chamfer to the tip of the blade, in an attempt to diffuse the leakage flow through the gap and obstruct the leakage flow with the outer casing's shear layer. A baseline flat tip case and three modified tip cases were simulated and the leakage flow and vortex for each was analyzed in detail. By chamfering the blade tip near the trailing edge of the gap, the leakage flow inside the gap was turned toward the direction of the blade's camber. This turning resulted in a decrease in the size and strength of the leakage vortex and its subsequent losses, while at the same time, did not reduce the blade loading by an appreciable amount.