Experimentally measured effects of height and location of the vortex generator on flow and heat transfer characteristics of the flat-plate film cooling

Abstract

Experimental measurements were performed to study the effects of vortex generator (VG) height H/D = 0, 0.37, 0.75, 1.00, 1.27, 1.50 and location L/D = 1, 2, 3, 4 on VG enhancing the film cooling performance at different blowing ratios (M = 0.5, 1.0, 1.5) in a flat plate. Detailed velocity field and streamwise vorticity distribution visualized by Particle Image Velocimetry (PIV) system showed that an anti-counter-rotating vortex pair (ACRVP) was generated by VG, whose strength and size increases no matter how M or H/D increases. The film cooling effectiveness distribution measurements by infrared camera indicated that VG shows a great advantage in enhancing film cooling. Especially at M = 1.5, the area averaged film cooling effectiveness of the model with H/D = 1.00 could increase by 220%, compared with that of the model without VG. As H/D increases, the film cooling performance becomes better and then worse, because the increase of VG height helps entrain more injection flow for the short VG but the mainstream would be entrained into the strong ACRVP towards the wall when VG is too high. Besides, as M increases, the film cooling performance of models with H/D = 0, 0.37 becomes worse while those models with H/D = 1.0, 1.27, 1.50 becomes better. For the impact of VG location, measurements conducted on the model with H/D = 1.00 at M = 0.5, 1.0, 1.5 shows that VG location hardly affects the film cooling attachment except for the zone around the VG. At the high blowing ratio M = 1.0 and M = 1.5, the film cooling effectiveness on the zone around VG decreases significantly when the VG location varies from L/D = 1 to L/D = 4, but at M = 0.5, it hardly changes with the VG location varying.