Experiments on vented deflagration of stoichiometric hydrogen–methane–air mixtures: Effect of hydrogen fraction

Abstract

In this study, experiments on the vented deflagration of stoichiometric hydrogen–methane–air mixtures were performed in a 300 mm (length) × 300 mm (width) × 1000 mm (height) duct with a 250 mm × 250 mm vent on the top surface, to investigate the effect of hydrogen fraction in fuel (χ) ranging from 0 to 1.0 on flame evolution and pressure buildup within and outside the duct. The results reveal that χ significantly affects flame propagation and pressure–time histories. The movement of the entire flame bubble toward and away from the vent and a spike-shaped structure, which had been observed in a vented methane–air mixture in a previous study, was observed for low χ in current tests. For a given χ, the maximum overpressure in the duct increased with the distance to the vent. Both the maximum internal and external overpressure increased slowly as χ increased from 0 to 0.7, and increased quickly with a further increase in χ. Violent external explosions occurred for χ = 0.8 and 1.0, and an extremely high internal overpressure appeared under the effect of the external explosion.