CALCULATION OF THE UPPER EXPLOSION LIMIT OF METHANE-AIR MIXTURES AT ELEVATED PRESSURES AND TEMPERATURES

摘要

Four different existing methods to calculate the upper explosion limit of methane-air mixtures at initial pressures up to 10 bar and initial temperatures up to 200°C are evaluated by comparison with experimental data. Planar freely propagating flames are calculated with the inclusion of a radiation heat loss term in the energy conservation equation to numerically obtain explosion limits. Three different reaction mechanisms are used in these calculations. At atmospheric pressure, the results of these calculations are satisfactory. At elevated pressures, however, large discrepancies are found. The spherically expanding flame calculations only show a marginal improvement compared with the planar flame calculations. On the other hand, the application of a limiting burning velocity with a pressure dependence S_(u,lim) ~ p~(-1/2) is found to give good agreement with the experimental data, whereas the application of a limiting flame temperature is found to underestimate the pressure dependence of the upper explosion limit.