The heat transfer enhancement mechanism of W-shaped micro-ribs on impingement cooling

Abstract

In order to improve the performance of impingement cooling in turbine blades, W-shaped micro-ribs are arranged on the target surface to weaken the influence of cross-flow and generate longitudinal vortexes. The k-ω SST turbulence model is used for numerical simulation, and the mechanism of W-ribs on the enhancement of air impingement cooling performance and the influence of W-ribs geometry are studied. Under the condition of jet flow Reynolds number 4000 to 10000, based on the W-ribs with an angle α = 120°, width W = 0.1 mm and height H = 0.3 mm, the effects of angle (α = 90°, 120°, 150°, 180°), width (W = 0.05, 0.1, 0.2, 0.4 mm) and height (H = 1, 3, 4, 8 mm) on flow and heat transfer are investigated respectively. The results show that the W-ribs can separate the flow to both sides while generating longitudinal vortexes, which can reduce the influence of crossflow and enhance the sweep of the target surface to achieve the effect of enhancing heat transfer. α is the key factor affecting the generation of longitudinal vortex. W has little effect on the flow structure, but mainly affects the vorticity. H mainly affects the distribution of mass flow rate, which has a direct impact on the uniformity of upstream and downstream heat transfer. The W-ribs with α = 120°, W = 0.1 mm and H = 0.4 mm is recommended because of its excellent heat transfer performance and high comprehensive heat transfer performance, which are 39.7–48.9 % and 1.5–9.7 % higher than the smooth target surface, respectively.