TIP LEAKAGE/MAIN FLOW INTERACTIONS IN MULTI-STAGE HP TURBINES WITH SHORT-HEIGHT BLADING

摘要

Interaction of the main flow with tip leakage over shrouded rotor blades in a multi-stage turbine is studied numerically. The flow in blade-to-blade channels is computed with the aid of a 3D Navier-Stokes solver FlowER with the Menter SST turbulence model. In this paper, the labyrinth seals are not computed but the numerical scheme is modified to include the source/sink-type boundary conditions at places at the endwalls referring to design locations of injection of leakage flows into, or their extraction from, the blade-to-blade passage. Without considering complete labyrinth seal geometries, the tip leakage jet is represented by its flow rate and direction at re-entry to the blade-to-blade passage, as if referring to the performance of a range of different labyrinth seal arrangements. The effect of direction of tip leakage re-entry on the downstream flow and efficiency of the turbine stage (stage group) is studied. The calculation method is validated on a model air stator/rotor turbine.