Experimental Investigation of Rotor Tip Film Cooling at an Axial Turbine with Swirling Inflow Using Pressure Sensitive Paint

• Main Authors: Manuel Wilhelm, Heinz-Peter Schiffer
• Format: Article
• Language: English
• Published: MDPI AG 2019-08-01
• Series: International Journal of Turbomachinery, Propulsion and Power
• Subjects: combustor–turbine interaction; rotor blade tip; swirl; film cooling; pressure sensitive paint
• Online Access: https://www.mdpi.com/2504-186X/4/3/23

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>&#951;</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>&#951;</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>&#951;</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>&#951;</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>&#951;</mi> </semantics> </math> </inline-formula>.