Effects of crossflow-fed-shaped holes on the adiabatic film cooling effectiveness

Abstract

The effects of internal crossflow-fed-shaped holes on the unsteady behavior of the adiabatic film cooling effectiveness were extensively investigated using high-resolution fast-response pressure-sensitive paint (fast-PSP). During the experiment, coolant (DR ≈ 1.0) was fed into either plenum chamber or crossflow channel at coolant to mainstream velocity ratio of VRc = 0.4-1.6, channel to mainstream velocity ratio of VRch = 0.4-0.7, and channel to coolant (hole-inlet) velocity ratio of VRin = 0.25-1.75. The mean and unsteady effectiveness were presented in the near-hole region (9D), where the significance of the internal crossflow was captured. The results affirmed the asymmetrical coolant deterioration behind the crossflow-fed-shaped holes compared with the plenum feed. The unsteadiness was originated from the hole entrance (i.e., in-hole counter-rotating vortex-pair (CRVP) and the in-hole vortex-tube structures for plenum and crossflow, respectively). The vortex-tube formed a swirl-vortex, which interacted with the CRVP at the windward side, leading to asymmetric CRVP and declined effectiveness. Meanwhile, the coolant spreading behind the crossflow-fed-shaped holes was sensitive to the hole-inlet velocity (VRin), showing symmetric spreading at VRin ≈ 1.0, biased to the windward at VRin < 1.0, and biased to the leeward when VRin > 1.0. The combined results insight our understanding into the coolant unsteadiness of the shaped-holes in-flow conditions, recommends modifying the hole-inlet shape in order to enhance the effectiveness and damp the corresponding unsteadiness.