Abstract:

To know the internal flows and the leakage flow in turbine cascade with tip clearance, detailed measurements were carried out in both the passage and the tip clearance using a five hole Pitot tube. Flow visualization was also carried out on the blade surface and the endwall. In a detailed analysis, a topological method was adopted to describe the visualization, to investigate the mechanism of how various vortices came into being inside the cascade passage. The experimental results show that: (a) Complex vortices such as leakage vortex were found to occur due to the existence of the tip clearance, and losses near the tip of the blade were increased notably because of the interaction of those vortices; (b) Reverse flows were seen near the blade trailing edge.

Key words: cascadeflow, clearancs, topology, vortices