The film cooling effectiveness provided by two rows of holes separated by a range of distances has been studied experimentally using a mass transfer technique. The blowing rates at the two rows were varied independently. The results are presented in forms suitable for design purposes. Spanwise and area averaged effectivenesses are given for a range of blowing rates. Thus optimum blowing rates for a given row spacing and total coolant flow can be established. Comparisons with a simple superposition theory show that this can be used with safety for design purposes if the holes in the two rows are staggered, but restrictions apply if they are in-line.

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