Study on flow and heat transfer characteristics of impingement/effusion cooling with different gradient diameters patterns under initial crossflow

This paper studies the effects of gradient impingement hole and film hole diameters on impingement/effusion cooling at different crossflow-to-jet mass flow ratio ( CMFR ) and blowing ratio ( BR ) condition. From the results, when the CMFR is less than 0.5, the Nusselt number of 5in_imp and uniform patterns are almost the same and higher than that of 5de_imp pattern, and when the CMFR is more than 0.5, the relative size of Nusselt number for different gradient impingement hole patterns are related to BR . Additionally, it also affects the film cooling, but this only occurs at the BR of 0.5, and the film cooling of 5in_imp pattern is the best. As for gradient film hole diameter, it only affects in film cooling when the BR doesn’t exceed 1.0, and the 5de_film pattern always performs the best. Similarly, it also affects in impingement cooling. Among them, the 5de_film pattern always has the highest Nusselt number, while the 5in_film pattern always has the lowest value. In conclusion, adjusting the distribution of impingement hole and film hole diameters can improve impingement heat transfer and film attachment simultaneously, such as 5in_imp and 5de_film patterns, which provides ingenious thoughts for performance improvement of impingement/effusion cooling under crossflow.