Combustion characteristics of methane hydrate in a laminar boundary layer

This Article reports the experimental study on the dissociation and flame propagation characteristics of methane hydrate in a laminar boundary layer over a horizontal flat plate. Experiments were performed at room temperature under atmospheric pressure using the methane hydrate crystals that were initially stored at liquidnitrogen temperature. The methane hydrate crystals were packed in an insulated rectangular cell such that the surface of the packed hydrate layer was flush with the horizontal flat plate. The air was supplied over the horizontal plate from a blower through an orifice, a settling chamber, and a converging nozzle. The surface of the dissociating hydrate crystals was ignited at the downstream end of the hydrate crystals by a pilot flame. The free stream velocity of the air was varied from 0.1 to 1.5 m/s. It was observed that the leading flame edge propagated in the upstream direction against the air flow and finally reached the upstream end. The flame was then extinguished despite the fact that the methane hydrate crystals were not completely dissociated. An ice layer was formed over the methane hydrate crystals that prevented the dissociation of the methane hydrate, thereby resulting in the flame extinction. The propagation speed of the flame over the hydrate crystals was experimentally measured. A discussion is presented on the relation between the flame propagation speed and the free stream velocity.