Fundamental study on the innovative film cooling technologies to suppress the mixing process with adding swirling motion to the coolant

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This study has been conducted to investigate a new film cooling method that utilizes swirling coolant flow through circular and shaped film cooling holes. The mixing phenomena with a film cooling air and a mainstream was measured by a instantaneous and simultaneous LIF and PIV methods, and the film cooling effectiveness on the wall was measured by PSP.It appeared from the results that, in the case of a circular film-cooling hole, the penetration of the coolant jet into the mainstream was suppressed by the strong swirling motion of the coolant and attained 100% heigher film cooling effectiveness. As a result, the film cooling effectiveness on the wall maintained a higher value behind the cooling hole over a long range. Additionally, the kidney vortex structure disappeared. For the shaped film cooling hole, the coolant jet spreads wider in the span-wise direction. Thus, the pitch-averaged film cooling effectiveness downstream was 50% higher than that in the non-swirling case.