Experimental and numerical research on film cooling characteristics on the compound angle hole

Experimental research was conducted for studying the effect of blowing ratio (M) as well as cross-flow Reynolds number (Rec) on distribution characteristics in film cooling effectiveness (η) and heat transfer coefficient (h) on compound angle hole configuration with applying transient liquid crystal technology. At the same time, the distribution characteristics of discharge coefficient (Cd) were measured by the flow resistance experiment. Furthermore, the net heat flux reduction (NHFR) is applied for assessing the film cooling performance. Numerical simulation was carried out to present the flow features for analyzing the film cooling mechanism. Results demonstrate that the increasing Rec presents a great influence on the measured Cd at the small M. The flow loss caused by the cross-flow presents the slight influence on the measured Cd at the large M. In addition, the measured Cd shows upward tendency with the increase in M and is almost no change until M increases to a certain extent. At small M, the measured η at the hole downstream area is higher and descends with the increase in Rec. At the large M, jets at the hole outlet almost separated from the surface. Thus, the measured η at the hole downstream area is lower and rises with the increase in Rec. The increase in M makes the measured h at the hole downstream area descend. The increase in Rec makes the measured h of the hole downstream area rise. The NHFR shows the decreasing tendency with the increasing M. Under the condition of M = 0.5, values of the laterally averaged NHFR are between 0 and 0.4, which represents the positive effect on film cooling function. At the condition of M = 2.0, values of laterally averaged NHFR are less than 0, involving negative effects. Under the condition of M = 1.0, most of the laterally averaged NHFR presents the positive values, and only a small part of the laterally averaged NHFR is the negative values. Due to the rising η and the descending h, the NHFR decreases in the increase in Rec under the condition of M = 0.5 and M = 2.0. The increase in Rec presents the slight influence on the NHFR under the condition of M = 1.0.