Experimental study on heat transfer and throughflow losses characteristics of single/triple-row holes with an engine-representative density ratio

Abstract

In present study, the heat transfer and the throughflow losses characteristics of single/triple-row of fan-shaped and cylindrical film cooling holes with a fixed outlet width are studied experimentally with an engine-representative density ratio. The pressure-sensitive paint (PSP) measurement technology is utilized to test the film cooling performance. The film cooling holes with the inclination angle α which ranged from 20° to 30° and the diffusion angle β which ranged from 0° to 15° are considered. The heat transfer and flow resistance characteristics of film cooling holes under the engine-representative density ratio, DR, of 1.52 as well as the blowing ratio, BR, which ranged from 0.3 to 2.0 are studied. The critical blowing ratios of the secondary flow detaches from wall surface of each hole shape and the hole shape parameters which acquire the highest span-wise averaged adiabatic film cooling efficiency are obtained. Moreover, the experimental results indicate that, within the scope of the investigative parameters pondered in present study, the discharge coefficient and the film cooling performance of the cylindrical hole are significantly lower than that of the fan-shaped film cooling holes. The coolant jet which ejects from the fan-shaped holes does not blow off from the wall surface when BR ≤ 1.5. However, when BR = 2.0, a part of coolant jet begins to detach from the wall surface. In addition, when BR ≤ 1.5, the fan-shaped film cooling hole with the hole shape parameters of α = 20°, β = 15° generates the highest film cooling effectiveness. However, when BR > 1.5, the highest film cooling effectiveness is obtained by the fan-shaped hole with hole shape parameters of α = 25°, β = 10°. Importantly, the discharge coefficient does not change monotonously with the variation of the hole shape parameters. In addition, the fan-shaped film cooling holes with the hole shape parameters of α = 25°, β = 13° as well as those with α = 30°, β = 10° offer the highest discharge coefficient. Finally, the correlations for the discharge coefficients of different hole shape parameters are developed.