Experimental investigations on the effects of inclination angle and blowing ratio on the flat-plate film cooling enhancement using the vortex generator downstream

Experimental studies were carried out to study the effects of inclination angle (alpha = 20 degrees,30 degrees,40 degrees) and blowing ratio (M = 0.5, 1.0, 1.5) on the vortex generator (VG) to enhance the film cooling performance in a flat plate. Clear vortical structures visualized by Particle Image Velocimetry (PIV) system showed that an anti-counter-rotating vortex pair (ACRVP) was generated by VG. The secondary flow was entrained towards the wall and spread laterally because of the downwash effect of the ACRVP. The VG significantly improved the film cooling effectiveness. Especially when alpha = 20 degrees, M = 1.5, the area averaged film cooling effectiveness was improved as much as 248% by using VG. For the cases with VG, as the blowing ratio increases, the film cooling effectiveness increases in those cases with alpha = 20 degrees,30 degrees due to the strong downwash effect of ACRVP. In the case with alpha = 40 degrees, the film cooling effectiveness was enhanced with the increase of the blowing ratio when M < 1, due to the strong downwash effect of ACRVP. However, when M > 1, the film cooling effectiveness decreased because the upward momentum of the secondary flow was so high that its flow rate exceeded the entrainment capacity of ACRVP, worsening the film attachment on the wall. (C) 2017 Elsevier Ltd. All rights reserved.