Explosion characteristics of methane-air mixture near lower explosion limit at different relative humidities

Abstract

To explore the explosion characteristics of methane-air mixtures with low concentration of methane at various humidities, a device for producing and containing water-saturated air was developed. The temperature and flow of pipes, air bag and explosion vessel were controlled to obtain methane-air mixture with variable humidity. The 20 L spherical explosion vessel was employed to analyze the effect of relative humidity and methane concentration on methane explosion characteristics (i.e., maximum explosion pressure, maximum rate of pressure rise, lower explosion limit and laminar burning velocity). It is concluded that the maximum explosion pressure and maximum rate of pressure rise show a linear decrease with an increasing value of humidity. As the humidity of gas mixture changes from 27.7% to 80.1%, the lower explosion limit of methane in air increases from 5.15% to 5.25% with a rising rate of 1.9%. The laminar burning velocity performs a similar linear downtrend with the increase of relative humidity. Under the given circumstances, the relative humidity has no significant influence on the explosion characteristic of methane-air mixture, which can be ascribed to the low value of partial pressure of water vapor at ambient condition. However, this influence cannot be neglected as the water vapor increases to a certain extent level at high temperatures and high pressures.