Concentration Limits of Flammability of Hydrogen–Methane–Carbon Monoxide Mixtures with Air in the Presence of Water Vapor

We present experimentally determined concentration limits of flammability of methane–air–water vapor mixtures, methane–hydrogen–air–water vapor mixtures at methane-to-hydrogen volume ratios of 1 : 2 and 2 : 1, and carbon monoxide–hydrogen–air–water vapor mixtures at a hydrogen-to-carbon monoxide volume ratio of 4 : 1. The initial temperature was 150°C, pressure was 101 kPa, and the water vapor content was varied in the range 0–60 vol %. The experiments were carried out in a 100-dm3 spherical chamber. Mixture ignition and flame propagation were imaged using infrared photography. The experimentally determined flammability limits of the methane–air–water vapor mixtures agree with available literature data. In the hydrogen-containing mixtures near their lower flammability limit, the flame was observed to propagate in the form of a spherical flame, which transformed into a toroidal vortex.