| Summary: | Rotor tip film cooling is investigated at the Large Scale Turbine Rig, which is a 1.5-stage axial turbine rig operating at low speeds. Using pressure sensitive paint, the film cooling effectiveness <inline-formula> <math display="inline"> <semantics> <mi>η</mi> </semantics> </math> </inline-formula> at a squealer-type blade tip with cylindrical pressure-side film cooling holes is obtained. The effect of turbine inlet swirl on <inline-formula> <math display="inline"> <semantics> <mi>η</mi> </semantics> </math> </inline-formula> is examined in comparison to an axial inflow baseline case. Coolant-to-mainstream injection ratios are varied between 0.45% and 1.74% for an engine-realistic coolant-to-mainstream density ratio of 1.5. It is shown that inlet swirl causes a reduction in <inline-formula> <math display="inline"> <semantics> <mi>η</mi> </semantics> </math> </inline-formula> for low injection ratios by up to 26%, with the trailing edge being especially susceptible to swirl. For injection ratios greater than 0.93%, however, <inline-formula> <math display="inline"> <semantics> <mi>η</mi> </semantics> </math> </inline-formula> is increased by up to 11% for swirling inflow, while for axial inflow a further increase in coolant injection does not transfer into a gain in <inline-formula> <math display="inline"> <semantics> <mi>η</mi> </semantics> </math> </inline-formula>.
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