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.
