Experiment on explosion limits of methane-air mixtures at high pressure and high temperature

Key words:  methane explosion  air injection  high pressure and high temperature  explosion limits  critical oxygen volume fraction  explosion ignition

Abstract:

The explosion limits and theoretical critical oxygen volume fraction of methane-air mixtures at high pressure (up to 20 MPa) and high temperatures (up to 100 ℃) were measured in the laboratory via explosion experiments. Electrically powered tungsten wires with high ignition energy were used as ignition sources, and an approximation method was adopted in the determination of the explosion limits. Based on the experimental data, a high pressure and high temperature explosion limit prediction model for methane-air mixtures was established. The experimental results indicate that as the initial pressure and temperature increase, the lower explosion limit (LEL) of methane in air is slightly reduced, while the upper explosion limit (UEL) is significantly increased, and the theoretical critical oxygen volume fraction is gradually reduced. The explosion limits of methane arevaried linearly and logarithmically with temperature and pressure, respectively. The explosion limit of methane-air mixtures at 20 MPa and 100 ℃ is 2.87％ to 64.40％, and the theoretical critical oxygen volume fraction is as low as 5.74％. In addition, at near the UEL points, some CO can be generated after the explosion reaction due to lack of oxygen, while at near LEL, the reaction products mostly consist of CO₂ since oxygen is sufficient in the gas mixture.