Experimental and numerical study of OH* chemiluminescence in hydrogen diffusion flames

A co-flow burner was designed to generate axisymmetric diffusion flames for the application of line-of-sight optical diagnostics to hydrogen flames. Chemiluminescence images of OH* from laminar hydrogen diffusion flames, with and without co-flowing air, were recorded using an intensified camera system with a narrow-band filter at approximately 310 nm. The spectra of OH* chemiluminescence was acquired by a separate optical system. Local concentrations of the radiating radical OH* were determined using the inverse Abel transformation and calibration against a light source of known radiance. The uncertainty of the OH* concentration measurements is analysed to be −22% to +12% in the current experimental configuration. Numerical reconstruction of the physical flames was performed using a two dimensional axisymmetric flow model coupled with a detailed H2/O2 oxidation chemistry mechanism and an OH* chemiluminescent sub-scheme which includes options to use 6 different rate coefficients recommended in the literature for the OH* formation reaction H+O+M⇌OH*+M (R1). The numerical simulations using the rate coefficient of 1.5 × 1013exp(−5.98kcalmol−1/RT)cm6mol−2s−1 for R1 demonstrate the best agreement with the measured OH* chemiluminescence.