In the present study the effect of approach boundary layer conditions on film cooling effectiveness superposition for pressure side fan shaped holes on a first stage vane is investigated. More particularly, the effect of showerhead cooling on the film effectiveness of downstream pressure side rows is addressed. The experimental test facility used is a continuously running , two passage, linear cascade wind tunnel equipped with a central vane and contoured side walls. Main stream stagnation conditions and pressure measurements on the vane external surface were taken to determine the isentropic Mach number distribution. The turbulence level generated with a bar grid is around 15%. Film cooling effectiveness has been determined with the narrow banded thermochromic liquid crystal steady state technique. Mainstream as well as coolant flow could be heated to shift the iso-temperature contours across the vane. Carbon dioxide was used as coolant gas to better match the density ratio in the experimental facility to engine conditions. The test model is a research vane equipped with four rows of cylindrical holes showerhead and three rows of fan shaped holes along the pressure side at typical inclination angles to the surface. The study incorporates single row blowing with the following row approach conditions: 1) no showerhead injection, 2) boundary layer trip, 3) isothermal showerhead blowing, and multi-row blowing with and without showerhead blowing. The results are used to investigate the applicability of the single row results superposition approach for multiple-row injection. Simulating the appropriate aerodynamic conditions during individual row measurements improves the superposition prediction in comparison to the multi-row results.

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