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Supersonic Combustion of Hydrogen in Mach 2 Flows Over an Axisymmetric Model

An external axisymmetric model featuring a cavity flame-holder fuelled by hydrogen was adopted for the study of the supersonic combustion in Mach 2 flows. The self-sustained hydrogen flames ignited by a spark gap igniter were detected using two optical techniques: an intensified camera attachment coupled with a high speed camera with a narrow-band-pass filter centred at 310 nm for detection of OH* chemiluminescence; and high-speed schlieren imaging for flow visualization. The spark ignition was identified on the schlieren images which also enabled visualisation of changes in the flow structure associated with the combustion. Local concentrations of the radiating radical OH* were determined using the inverse Abel transformation based on the ICCD images and calibration against a light source of known radiance. The combustion flow was reconstructed numerically using a CFD Solver, Eilmer4 in an axisymmetric configuration coupled with a detailed H2/O2 oxidation chemistry mechanism and a OH* chemiluminescence sub-scheme. The maximum magnitude of the results for the OH* chemiluminescence simulations demonstrated reasonable agreement with measurements.