Tip-Clearance Effects on Hot-Streak Migration in Low-Pressure Stage of Vaneless Counter-Rotating Turbine

Abstract

Three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed to reveal the effects of rotor tip clearance on the inlet hot-streak migration characteristics in the low-pressure stage of a vaneless counter-rotating turbine. The numerical results indicate that most of the hotter fluid migrates toward the rotor pressure surface and that only a small amount of hotter fluid migrates to the rotor suction surface when it convects into the low-pressure turbine rotor. The hotter fluid that migrated to the tip region of the high-pressure turbine rotor impinges on the leading edge of the low-pressure turbine rotor after it goes through the high-pressure turbine rotor. The migration of the hotter fluid directly results in a very high heat load at the leading edge of the low-pressure turbine rotor. The leakage flow in the rotor tip clearance tends to increase the low-pressure turbine rotor outlet temperature at the tip region.