EXPERIMENTAL AND NUMERICAL STUDIES OF H₂/CH₄/AIR EXPLOSION IN OPEN SPACE

In recent years, the use of hydrogen involves many fields. Multi-component mixture gas containing hydrogen is widely used in industrial production and domestic fuels. To ensure the safety of hydrogen containing gas in every links, e.g., production, transportation, and use, an outdoor open space mixed gas explosion test system is built. Five cases of hydrogen mole fraction (100%, 75%, 66.67%, 50%, 33.33%), five cases of equivalence ratio of mixed gas (0.8, 1.0, 1.1, 1.2, 1.4), three cases of initial volume of mixed gas (1 m³, 4 m³, 8 m³) and three kinds of constraints are adopted to study their effects on the mixed gas explosion pressure and flame. An explosion pressure prediction model considering the component ratio of the mixture and the initial volume of mixed gas is established based on the classical TNT equivalent method, and the theoretical model of explosion flame propagation radius is further modified by adding the effect of hydrogen mole fraction on the mixed gas explosion. Finally, the influence of building structure on explosion of H₂/CH₄/air mixtures is illustrated by experiments and large-scale high-resolution simulation. The results show that the addition of hydrogen can significantly enhance the gas explosion intensity. The maximum explosion pressure and flame propagation velocity increase with the hydrogen mole fraction, and first increases and then decreases with the increase of equivalence ratio, where the value increase to its peak value when the equivalence ratio is 1.1-1.2. At the same time, the hydrogen mole fraction and the initial volume of mixed gas seriously affect the accuracy of TNT equivalent method in predicting gas explosion pressure. The key parameters, e.g. explosion flame propagation distance, flame velocity and maximum explosion pressure, are obviously different under different construction conditions in the gas filling station. When the top and back side are restrained at the same time, the scope of explosion injury and consequences of an accident are the most serious. Thus, the influence of different building structures should be fully considered when delineating the safety distance of the gas station.