Structure and Stabilization Mechanisms of an Ethylene Flame in Supersonic Coflow

This work describes the characterization of flame stabilization mechanisms present in a recirculation-stabilized ethylene–air flame in supersonic coflow. OH-PLIF measurements are presented to highlight the influence of fuel jet momentum on the combustion-stabilizing radical pool at the center of the recirculation zone. The time-averaged shape of the jet interaction region and its proximity to areas of high heat release in the shear layer are also described as a function of fuel jet momentum. Decomposition of high-speed chemiluminescence images of the electronically excited methylidyne (CH*) radical indicates the presence of a large-scale instability. The flame base position extracted from the chemiluminescence data and the fuel jet penetration height extracted from high-speed schlieren measurements are analyzed in the time domain to reveal a temporal coupling. This coupling highlights the sensitivity of flame stabilization to the dynamics of the fuel injector.