Experimental Study on Explosion Characteristics and Consequences for Homogeneous and Inhomogeneous Methane-Air Mixtures within a Kitchen

Owing to the effect of a non-uniform concentration distribution, natural gas leakage explosion accidents usually cause different degrees of damage inside residential kitchens. According to the similarity principle, a reduced-scale experiment setup of a kitchen was established. Uniform and non-uniform explosion experiments for methane-air mixtures with concentrations of 7.7%, 9.5%, and 11.2% were performed. The flame propagation behavior and pressure evolution characteristics were analyzed for homogeneous and inhomogeneous methane-air mixtures. In addition, two dimensionless coefficients, namely macroscopic and directional non-uniformity coefficients, were introduced to quantify the uneven distribution of gas concentration within the kitchen. Furthermore, the flame development process and pressure evolvement characteristics were compared between homogeneous and inhomogeneous methane-air mixtures in a fuel-lean, chemical equivalence concentration and fuel-rich state. The results show that the macroscopic non-uniformity coefficients are 0.0998, 0.0653, and 0.0571 on the fuel-lean, chemical equivalence concentration and fuel-rich conditions, respectively. It indicates that the greatest non-uniformity of methane concentration distribution within the kitchen is represented on the fuel-lean condition. The concentration gradient could obviously reduce the explosion overpressure in the fuel-lean condition, whereas it would not significantly decrease the explosion overpressure in the chemical equivalence concentration or fuel-rich condition. It means that the greater the non-uniformity coefficient is, the more significant the effect on the overpressure peak is.