High spatiotemporal frame-straddling focusing schlieren imaging in a scramjet engine

Abstract

Abstract Flow visualization in harsh environments such as a scramjet combustor featuring highly turbulent supersonic reactive flow with intensive luminescence emission is challenging and typically lack of sufficient spatiotemporal resolution that is essential for resolving flow dynamics. This study presents a development of a robust flow visualization technique with an exceptional spatiotemporal resolution in a scramjet combustor. By utilizing a customized LED light source, the short pulse duration along with a high peak power and a single-color emission ensures an instantaneous exposure with little background luminescence interference. Focusing schlieren image measurements with mitigated path-integration effect are successfully demonstrated in a scramjet engine combustor at instant, frame-straddling, and sequential temporal resolutions of 100 ns, 500 ns, and 26 μs, respectively, along with a megapixel imaging resolution. Consequently, in addition to flow visualization, it is worth highlighting that the exceptional spatiotemporal correlation resolved by present measurements exhibits attractive potentials of velocimetry for harsh high-speed flow environments.