Progress of research on the effect of non-uniform premixing on hydrogen and methane explosion characteristics

This study attempted to systematically understand the research results on the explosion disaster effects of premixed hydrogen and methane gas driven by concentration. Based on the effect of obstacles on the explosion characteristics of non-uniform premixed gases, the experimental approach of non-uniform concentration distribution was comprehensively determined, and the experimental and numerical simulation results of the influence of non-uniform distribution on flame acceleration and deflagration to the detonation process were discussed. The results showed that the effects of non-uniform premixing on the hydrogen and methane deflagration characteristics were different in the unobstructed space. For hydrogen, the smooth pipe exhibited stronger flame acceleration and earlier deflagration to detonation, whereas for methane, the presence of concentration gradients did not promote flame acceleration or an overpressure rise. The presence of a critical value between the average fuel concentration and the concentration gradient in an obstructed space can result in flame acceleration or slowdown; however, owing to the limitations of the experimental method and equipment, the current results did not yield a more accurate critical value. Consequently, a new experimental device was proposed to investigate combustible gas deflagration driven by the concentration gradient, which provided a basis for further experiments on the influence of the concentration gradient interval on the deflagration characteristics of the premixed gas in the later stage. This review aimed to provide new research ideas and methods for studying the deflagration characteristics of combustible gases under nonuniform premixed conditions.