Explosion behaviors of mixtures of methane and air with saturated water vapor

• Saturated water vapor effect on explosion of methane/air mixtures was evaluated.
• Explosion and combustion parameters of methane/air mixtures were measured.
• The dual role of water vapor in the explosion was revealed and interpreted.

The explosion and combustion parameters of mixtures of methane and air with saturated water vapor were experimentally measured in a standard 20-L spherical explosion vessel at room temperature and atmospheric pressure. The experimental data were carefully scrutinized and compared to elucidate the effect of saturated water vapor in air. When the methane content is below 10%, the maximum explosion pressure, maximum rate of pressure rise and laminar flame speed during explosion are slightly affected, which is attributed to the dual role of water vapor: on one hand, the water vapor suppresses the explosion by thermal and chemical effects; on the other hand, the addition of water vapor makes the equivalence ratio higher than that at dry condition with the same methane content. Then when the methane content is relatively higher, the discrepancies between parameters are quite pronounced for the same reason. The flammability limits of methane in the mixture become narrower (6–14%) compared to dry methane/air mixtures (5–15%). Additionally, the measured laminar flame speeds and computed ones by HP-Mech agree well with each other in this work.