An experimental study on the improvements in the film cooling performance by an upstream micro-vortex generator

In this study, the placement of a micro-vortex generator (VG) upstream of the film cooling hole is proposed to improve the film cooling performance. The film cooling effectiveness and flow characteristics at three blowing ratios (M = 0.2, 0.4, and 0.8) are measured by using pressure-sensitive paint (PSP) and particle image velocimetry (PIV), respectively. The results indicate that the VG upstream of the cooling hole can improve the film cooling performance, and the effect is more pronounced at high blowing ratios (M = 0.4 and 0.8). Flow field measurements reveal that an anti-counter-rotating vortex pair (anti-CRVP) is generated by the upstream VG, counteracting the detrimental effects of the counter-rotating vortex pair (CRVP) induced by the coolant jet. The detachment of the coolant jet from the test surface is significantly suppressed at high blowing ratios, and the coverage of the cooling gas in the spanwise direction is extended due to the anti-CRVP induced by the VG. In addition, the influences of the VG height and the distance between the VG and the cooling hole are investigated to obtain the optimal VG geometry to achieve high film cooling efficiency.