An investigation of effectiveness and heat transfer on a cylinder model with showerhead cooling has been conducted in a free jet test facility, using the transient liquid crystal technique. A three- and a four-row configuration, covering a region of ±21°, were chosen to study the cooling behaviour for zero and off-design incidences. Typical engine airfoil leading edge conditions were maintained for the freestream Reynolds and Mach numbers to 1.55e5 and 0.26 for the three-row, and 1.84e5 and 0.30 for the four-row configuration, at a turbulence intensity of 7%. The blowing and momentum rates ware varied from 0.4 to 1.8 and 0.1 to 1.9, at a density ratio of 1.65. At zero incidence it could be observed for both configurations that the highest effectiveness of about 0.3 was achieved at a blowing rate of 0.4. Negative incidence for the four-row configuration resulted in much higher effectiveness, being as high as 0.5 at a blowing rate of 0.9, with an associated high heat transfer. Much lower effectiveness was achieved at positive incidence, where the blowing rate of 0.9 showed the best cooling behaviour. Higher effectiveness — but also increased heat transfer — was in general observed for the four-row configuration, with a 60% higher massflow.

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