Hydroxyl Tagging Velocimetry in Cavity-Piloted Mach 2 Combustor

Abstract

Hydroxyl tagging velocimetry (HTV) measurements of velocity were made in a Mach 2 scramjet combustor with a wall cavity flameholder. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas flow and dissociate H2O into H + OH to form a tagging grid of OH molecules. Previously demonstrated with a 7x7 grid of hydroxyl (OH) molecules, HTV is now demonstrated with an 11x11 grid of OH tracked by planar laserinduced fluorescence to yield about 120 velocity vectors of the two-dimensional flow over a fixed time delay. Instantaneous, single-shot measurements of two-dimensional flow patterns were made in the non-reacting Mach 2 flow from step to step in the cavity under lowand high-backpressure conditions. Single-shot profiles were analyzed to yield mean and rms velocity profiles in the Mach 2 non-reacting flow. A set of velocity data (spanning the entire length of the cavity) for an open wall cavity in a supersonic flow under low and high backpressure conditions was compiled for validation of CFD models.