Effects of impingement gap and hole arrangement on overall cooling effectiveness for impingement/effusion cooling

Abstract

The effects of geometrical parameters on overall cooling effectiveness were experimentally investigated on the flat plate with impingement/effusion cooling. Geometrical parameters investigated included two relative positions of impingement and effusion holes (staggered arrangement and overlapped arrangement) and three impingement gap distances (H/D = 2.5, 5 and 7.5). In addition, numerical simulation was employed to predict the effect of gap distance in a wider range. The results indicate that overall cooling effectiveness is significantly improved by adding impingement, while distribution of cooling effectiveness is mainly determined by film cooling and bore cooling. The comparison of cooling effectiveness between staggered and overlapped hole arrangement indicates that the former produces higher value at each blowing ratio and gap distance. At the same blowing ratio, the overall cooling effectiveness decreases as the increase of gap distance for staggered arrangement. For overlapped arrangement, the cooling effectiveness peaks at H/D = 10. Specific scaling principles of overall cooling effectiveness are experimentally validated by three cases with different temperature ratios. After matching mainstream side Reynolds number, Biot number, and the momentum flux ratio, the cooling effectiveness of case with lower temperature ratio agrees well with that of case with higher temperature ratio at each gap distance and hole arrangement.