Experimental investigation of the ignition process of a methane diffusion impinging flame

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The ignition process is of great importance both in fundamental combustion research and industrial applications. In this study, the flame structure and propagation characteristics of a methane diffusion impinging flame were investigated experimentally. Both high speed schlieren and stereo imaging techniques were applied to visualise the hot gas and visible flame evolution from ignition to flame establishment. It was found that the visible flame at the initial stage of ignition is highly three dimensional (3D) in space. The digital 3D reconstruction methods based on stereo images were applied to obtain the real flame structures. It can be seen from the 3D results that a long flame was formed tortously at first; after the flame reached the impinging plate, a round and wavy flame structure was observed; finally a flat round flame with a slender conical bottom was established. Moreover, the weak blue flame at the very beginning of ignition has been enhanced selectively for a more clear visualisation. It is found that the blue flame was in a ring-like shape locating at the top of the flame front. The diameter of the ring is increasing with time after it reaches the solid disc. After 120 ms over ignition initiation, the blue flame is vanishing gradually and the dominated flame is in yellow-redish color only.