Experimental study on methane-air mixtures explosion limits at normal and elevated initial temperatures and pressures

In order to study the influence of initial conditions on methane-air mixtures explosion limits, the explosion limits of methane-air mixtures were obtained experimentally at different initial temperatures up to 200 ℃ and initial pressures up to 1.0 MPa. The experiments were performed in a closed spherical 20 dm³ vessel with an ignition electrode at the center. The results show that with the increasing of initial temperature and initial pressure, the upper explosion limit increases, but the lower explosion limit decreases, that is the explosion limit expands. At atmospheric pressure/ambient temperature, the dependences of the upper explosion limit and lower explosion limit on initial temperature and initial pressure are both linear in the experimental temperature-pressure ranges. The dependence of the upper explosion limit on initial temperature/initial pressure is influenced by the initial pressure/initial temperature, but the dependence of the lower explosion limit on those is not influenced obviously. The coupling effects of initial temperature and initial pressure on the upper explosion limit and lower explosion limit are greater than that of a single factor, especially on the upper explosion limit. Surfaces are formed to describe how the initial temperature and initial pressure influence the upper explosion limit and the lower explosion limit of methane-air mixtures.