Study on the explosion characteristics and flame propagation of hydrogen-methane-air mixtures in a closed vessel

In this study, the examination of the explosion pressure and flame propagation characteristics were investigated for premixed CH4-H2-air mixtures, with varying equivalence ratios (phi = 0.8-1.5) and methane volume ratios (R = 0-100%). This investigation was conducted employing a 20 L explosion vessel and a high-speed ripple shadow meter, while maintaining ambient temperature and pressure. The most critical primitive reactions effecting the formation and consumption of OH* were obtained by normalisation through rate analysis. The result found that as the R increased at the same phi, the premixed system exhibited a gradually decreased in the Pmax, (dP/dt)max, and KG. The increase in the R caused the flame structure to stabilise, extending the flame front distance and the time to reach the wall. The reaction process was divided into three phases based on the R: 0 < R<40% (dominated by hydrogen combustion), 40% < R<80% (dominated by methane and hydrogen co-combustion), and 80% < R<100% (dominated by methane combustion). The analysis of OH* production rate showed that R84 and R38 were the most dominant reactions promoting the OH* production and consumption, respectively. As R was increased, both the production and consumption rates of OH* decreased resulting in a weakening of the explosive reaction's intensity.