Experimental investigation on flame pattern formations of DME–air mixtures in a radial microchannel

Flame pattern formations of premixed DME–air mixture in a heated radial channel with a gap distance of 2.5 mm were experimentally investigated. The DME–air mixture was introduced into the radial channel through a delivery tube which connected with the center of the top disk. With an image-intensified high-speed video camera, rich flame pattern formations were identified in this configuration. Regime diagram of all these flame patterns was drawn based on the experimental findings in the equivalence ratio range of 0.6–2.0 and inlet velocity range of 1.0–5.0 m/s. Compared with our previous study on premixed methane–air flames, there are several distinct characteristics for the present study. First, Pelton-wheel-like rotary flames and traveling flames with kink-like structures were observed for the first time. Second, in most cases, flames can be stabilized near the inlet port of the channel, exhibiting a conical or cup-like shape, while the conventional circular flame was only observed under limited conditions. Thirdly, an oscillating flame phenomenon occurred under certain conditions. During the oscillation process, a target appearance was seen at some instance. These pattern formation characteristics are considered to be associated with the low-temperature oxidation of DME.