On the formation of multiple rotating Pelton-like flame structures in radial microchannels with lean methane - Air mixtures

This paper reports the experimental observation of multiple Pelton-like rotating flame structures in radial microchannels with lean methane-air mixtures supplied at the center of the two closely placed circular quartz plates. The bottom quartz plate was heated with a porous burner to create a positive temperature gradient distribution along the flow direction. Stable flames were observed at a radial location for stoichiometric and rich mixtures over a wide range of operating conditions. On the other hand, for lean methaneair mixtures at Φ = 0.67 and channel gap of ∼1-2 mm, distinct and single/multiple Pelton-like rotating flame structures were observed experimentally. These rotating flames were semi-circular in shape with a rotational speed varying from 15 to 50 Hz. Due to continuous rotation and a semi-circular flame shape; the rotating flames resemble a classical Pelton wheel. These flame structures were observed to appear over a range of velocities varying from 1.5 to 6 m/s. One, two and three rotating flames fronts appear in the domain at similar operating conditions. The effects of change in the temperature gradient and temperature profile were examined by employing a different porous burner and these modes were observed to be present for an asymmetric temperature profile. The appearance of these multiple rotating flame fronts was a function of peak temperature of the plates.