<p>To study the effect of blockage on the film cooling performance, three kinds of film cooling plate models with cylindrical hole, compound hole and fan-shaped hole were established respectively. The effects of blockage ratio(B) and blowing ratio(M) on the film cooling characteristics under the conditions of all-round blockage, leading-edge blockage and trailing-edge blockage were studied by numerical simulation, and the anti-blockage performance was also compared. Results show that before blockage, due to the short length of the cooling hole, the average cooling effectiveness of the cylindrical hole decreases with the increase of the blowing ratio; while that of compound hole decreases firstly and then increases, which reaches the peak value of 0.3 under the blowing ratio of 0.75; while that of fan-shaped hole decreases after the anti-kidney vortex appears caused by two pairs of opposite velocity gradients when the blowing ratio is bigger than 0.5. For all-round blockage cases, as the exit area of cooling hole shrinks, the coolant jet velocity increases, the cooling effectiveness of three types hole decreases with the increase of blockage ratio at up-stream area. And due to the overall velocity increase in the fan-shaped hole, the reverse pressure gradient and velocity gradient are reduced, which lead to the disappearance of anti-kidney vortex structure; at down-stream area of film cooling holes, the range of the vortex in the y and z directions increases with the blockage ratio increase, causing the mixed gas to return to the wall surface in the cylindrical hole and fan-shaped hole, and this trend will be stronger due to the increase in the strength of the vortex with the increase of blowing ratio. For leading-edge blockage cases, the coolant jet velocity component along mainstream direction increases sharply, which weakens the adverse effect of the overall speed. The increase rate of cooling effectiveness of fan-shaped hole is more than 20%, higher than that of 11% in cylindrical hole and 15% in compound hole, and the weaker anti-kidney vortex makes the coolant distribution more even. For trailing-edge blockage, a higher pretention speed of coolant jet is resulted, the cooling effectiveness of the compound hole and cylindrical hole decreases by 15% - 20%, while that of fan-shaped hole is below 5% under the action of the anti-kidney vortex and wide trailing-edge structure. In all cases, cylindrical hole demonstrates the worst cooling performance among all blockage cases while the fan-shaped hole performs the best. The compound hole shows better anti-blockage performance at conditions of leading-edge blockage and all-round blockage under low blowing ratio, while the fan-shaped hole shows better anti-blockage performance at conditions of trailing-edge blockage and all-round blockage under high blowing ratio.</p>

Influence of Film Cooling Holes Partial Blockage on Cooling Effectiveness

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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