The effect of precession on the ignition region in jet flames

Abstract

Planar Laser-induced Fluorescence (PLIF) of the OH radical was used to study the base of the active combustion region in the flame produced by a mechanically precessed jet (MPJ) nozzle firing methane. Instantaneous images of the OH radical distribution were obtained for a range of jet flow rates and frequencies of jet precession about the central jet axis. The MPJ burner has been developed to better understand the effects of jet precession which have been found to reduce NOx emissions and increase emissivity in industrial flames. Broad distributions of the OH radical with widths up to 31.3 mm are shown to exist in the flame. Furthermore, combustion at the base of the flame is seen to occur not only at the periphery of the flame but also along the nozzle axis indicating the presence of a stoichiometric fuel air mixture there.