Influence of clearance leakage on turbine heat transfer at and near blade tips - Summary of recent results

In gas turbine engines, the unshrouded blades of axial turbine stages rotate in close proximity to the stationary outer wall, or seal, of the turbine housing. The pressure difference between pressure and suction sides of the blade drives a leakage flow through the gap between the rotating blade tip and adjacent wall. Flow and heat transfer at the blade tips have long been subjects of interest to gas turbine engine designers because of effects on aerodynamic performance and because material failures are frequently observed in that region. However, until quite recently only a very incomplete and largely qualitative understanding existed of the clearance gap flowfield, and virtually no information was available on the heat transfer effects. In this paper, an overview is given of recent published efforts to elucidate more features of the leakage-related flowfield and convection heat transfer on and near unshrouded turbine blade tips. 20 references.

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