Experimental study on overpressure and flame characteristics of hydrogen-methane mixture

In order to evaluate the consequences of hydrogen-methane mixture explosion accidents in open space and confined space, large-scale (8 m³) open space and confined space (55 m³) hydrogen-methane mixture explosion experiments were carried out to study the effects of hydrogen-doped ratio and equivalent ratio on hydrogen-methane mixture explosion characteristics. In the open space experiments, within the equivalence ratio range of 0.9 to 1.3, the overpressure measured at an equivalence ratio of 1.1 is the highest. When the equivalent ratio is 1.1, the higher the hydrogen blending ratio, the higher the overpressure peak and the farther the action distance. The overall overpressure increased significantly when the hydrogen blending ratio increased from 20% to 30%. When the hydrogen ratio is 30%, the flame propagation speed is as high as 20 m/s, which is about twice the flame propagation peak speed when the hydrogen ratio is 10%–20%. Therefore, from the angle of overpressure and flame development, the step point of overpressure harm can be obtained by a hydrogen mixing ratio of 20%. The overall trend of external overpressure change in confined and open spaces is consistent; both decrease with the increase in distance. However, the external overpressure in confined space is more significant than in open space, and the flame propagation speed is much higher than in open space. Compared with open space, the harm range of confined space is more extensive. This study provides an experimental basis for the safety assessment of hydrogen-methane mixture and the formulation of safety protection measures.