Experimental and Theoretical Study of Diffusion Combustion of Methane above a Gas Hydrate Layer in a Laminar Air Flow

Dissociation of Gas Hydrates in the Combustion Environment

“…Shvab-Zeldovich approximation widely used in combustion theory [39,40]. Gas combustion above a decomposing hydrate powder can be considered as a reaction process in the boundary layer above a permeable surface [41] (in this case, the injection velocity is, as a rule, low enough to consider its effect insignificant and to use the approximation for an impermeable surface [12,22]). In some experimental setups, air is supplied through the hydrate layer [42,17].…”

“…The model allows calculating the critical conditions for flame extinction (including local extinction in turbulent flows [44]). In [22], we calculated the stability limits of combustion for methane/water vapor mixtures (using data from the experimental work [24]). In addition, it is shown that with the accurately chosen spatial scale, it is possible to reproduce the extinction conditions for methane above the methane hydrate layer.…”

“…In the combustion of a boundary layer, the linear scale is related to its thickness; therefore, in general, it depends on the position of the flame front. Even for moving flame front, it is possible to choose an averaged length that allows calculating its stability under conditions of convective heat transfer [22]. The calculations show that the radiative term ( 12) cannot be neglected due to high concentration of CO2 and H2O [20].…”

“…The separation of isola from the region of lowtemperature solutions indicates the impossibility of selfignition in such mixtures, which is consistent with the reality (methane hydrate flames are usually initiated by pilot heat source). The critical concentration of water vapor in a mixture with methane for the room temperature environment is of the order of 70% [22]. The higher the environment temperature, the wider the flame stability limits.…”

“…In this case, however, the conditions on the outer surface of the powder layer are approximate. In [22], this model is used to estimate the stability of a methane-air-steam diffusion flame (such flames are considered experimentally and theoretically in [23,24]).…”