Planar laser-induced fluorescence imaging of OH in a supersonic combustor fueled with ethylene and methane

A supersonic combustor was experimentally investigated using both conventional instrumentation and laser-based diagnostics. Planar laser-induced fluorescence (PLIF) imaging of OH was used in the main section of the combustor to examine flameholding and flame propagation during a series of evaluations at conditions simulating Mach-5.5 flight. Parameters of interest in this study included the angle of the primary fuel injectors, the distribution of fuel throughout the combustor, and the fuel composition. Changes in fuel-injection angle were expected to influence the mixing and combustion processes, and therefore combustor operation. Fuel-distribution variations were expected to modify the flame propagation between flameholding regions. Finally, ethylene and methane were used to examine the suitability of the flameholder designs over a wide range of fuel reactivity. Results suggest that the combustor provides relatively robust flameholding regardless of the fuel used and good flame propagation as long as the fuel distribution provides favorable conditions in the flameholding regions. In addition, the results show that the primary injectors can be useful in controlling certain aspects of combustor operability.