Visualization of supersonic combustion using high-speed camera/dual-component planar laser-induced fluorescence simultaneous diagnostic technique

Abstract

High-spatiotemporal-resolution diagnostics are important for capturing fine physicochemical structures in supersonic combustion. In this study, a high-speed camera (HSC)/dual-component planar laser-induced fluorescence (PLIF) simultaneous diagnostic technique is developed and applied to an ethylene-fueled scramjet to determine the flame structures and heat release characteristics of cavity shear-layer stabilized combustion. CH2O-PLIF and OH-PLIF simultaneous imaging techniques are used to capture the transient structures in the preheat and product zones of the flame, while the heat release zone (HRZ) is identified by the product of these two signals. Synchronized HSC techniques are used to capture the full-band flame fluorescence. The flame base was found to stabilize in the cavity shear layer at a certain distance downstream of the leading edge. The HRZ was initiated near the flame base and gradually spread into the mainstream. Upstream of the HRZ, the partially premixed fuel jet undergoes preheating oxidation reactions, forming the preheat zone adjacent to the HRZ. Downstream of the HRZ, hot products were produced, forming the product zone distributed in both the cavity and mainstream. The central role of the cavity is to provide a favorable environment for stabilizing the flame base rather than participating in heat release reactions. Schlieren images and wall pressure distributions are also documented, constituting a dataset that could be used to validate computational models.