Experimental study on the effects of equivalence ratio on vented methane-hydrogen mixture explosion in confined area

The combustion and explosive characteristics of a methane-hydrogen mixture (with 15 % hydrogen mixing volume ratio) were studied in a 55 m³ confined space at various equivalence ratios (Φ = 0.9/1.0/1.1/1.2/1.3). Internal and external pressures, along with flame shape, were analyzed. The results suggest that the outside flame propagation rate initially increases and then decreases as the equivalency ratio increases. The fastest flame propagation speed (62.751 m/s) and the greatest outer flame length (11.045 m) occur at an equivalency ratio of 1.1. At the summit of the four phases that typically constitute the development of internal overpressure, the Helmholtz oscillation-generated peak is predominant. For equivalency ratios of 0.9/1.0/1.1/1.2/1.3, P_hel has values of 2.705/6.815/12.210/12.339/4.098 kPa. The hazard of the confined space is assessed using the deflagration index (K_G), closely associated with P_hel. The maximal value of K_G, which is 8693.5493 kPa m/s, is achieved at an equivalency ratio of 1.1. The outdoor overpressure is influenced by the pressure generated by the venting structure's aperture and external explosion. The link between the flame propagation speed and the outdoor overpressure apex can be approximated using an exponential function. Findings support designing explosion prevention, investigating accidents, and assessing risks in methane-hydrogen energy industry.