Improved Spatiotemporal Distributions of Sweeping Jet Film Cooling With a Shaped Exit Design

Sweeping jet (SJ) is a self-excited flow control device that can generate continuous and periodic flow, which makes it a promising geometry for film cooling. However, the cooling performance of current SJ configurations is not significantly better than that of 777-shaped holes. This paper presents two modified SJ configurations, named shaped SJ1 and shaped SJ2, which possess distinct shaped exit geometries. The spatiotemporal coolant distributions were comprehensively quantified for the 777-shaped hole, the compact SJ (with compact geometry), the shaped SJ1, and the shaped SJ2. The instantaneous cooling effectiveness distributions of the four configurations at blowing ratios (M) ranging from 0.5 to 3.0 were measured using the fast pressure-sensitive paint technique. The shaped SJ2 integrated the cooling characteristics of the 777-shaped hole and SJ. It maintained stability at a relatively low M, while began to oscillate when M was increased above 1.5. The shaped SJ design exhibited superior cooling effectiveness at both low and high M of 0.5 to 3.0. A proper orthogonal decomposition analysis and simulations illustrated the oscillation processes and flow structures within the SJ configuration. The shaped SJ2 showed a reduced outlet momentum and a more even distribution of film coverage than the 777-shaped hole, resulting in considerably improved cooling performance.