Convective heat transfer characteristics of periodic oscillating jet-regenerative composite cooling for scramjet engines

This study employs numerical simulation to investigate the flow and heat transfer characteristics of periodic oscillating jet-regenerative composite cooling in regenerative micro-ribbed channels on the walls of a scramjet combustor under a constant high heat flux density at the inner bottom surface. Transient flow and heat transfer properties of single-hole and array oscillating jets within a cycle were examined. Parametric studies were conducted on the jet Reynolds number (Re), oscillation frequency (f), maximum unilateral oscillation angle (θ), and the ratio of jet height to inlet diameter (H/L), with visualized analysis of numerical results. The research findings indicate that periodic oscillating jets significantly enhance the uniformity of overall heat transfer. For single-hole oscillating jets: The time-averaged Nusselt number (Nu) on the heated target surface increases with higher Re, H, L, and f. For every 20 m/s increase in velocity (v), the maximum enhancement of Nu reaches 76.9 %. For every 15° reduction in θ, the maximum improvement of Nu attains 66.7 %. The effect of H/L on Nu exhibits inconsistent behavior due to independent variations in H and L. For array jets: direct jets and reverse-oscillation jets show similar flow-heat transfer characteristics; however direct jets exhibit higher values at the jet centers. Conversely, co-directional oscillation delivers superior heat transfer performance. Variations in f and θ have minimal impact on thermal performance under reverse-direction oscillation, but larger f and θ significantly improve heat transfer efficiency and uniformity under co-directional oscillation.