Study on characteristics of methane explosion flame and pressure wave propagation to the non-methane area in a connected chamber

This study is aimed at investigating the characteristics of CH₄ explosion diffusion and propagation to the non-methane area. The CH₄ explosion pressure and flame were tested with the aid of a self-built horizontal pipeline system. On this basis, the flame images, photoelectric signals, and pressure propagation laws during explosions of methane with different volume fractions in the pipeline were obtained. The experimental research results indicate that an obvious secondary explosion pressure occurs at L/D = 3.5. After the explosion pressures at different positions along the entire pipeline reach the peak values, they experience varying degrees of oscillations. The maximum explosion pressure in the non-methane zone may occur at different length-to-diameter ratios. When the volume fraction of CH₄ is larger, the maximum explosion pressure occurs farther. However, the explosion pressure at the end of the pipeline is lower than that at the explosion source. The flame intensity and flame duration of methane explosion are remarkably enhanced at L/D = 17.5 and then become gradually weakened in the non-methane area. The variations of explosion pressure are always prior to those of flame signal. CO and CO₂ are the main toxic and harmful gases produced by methane explosions, and high-concentration (13% in this experiment) methane explosions produce a small amount of hydrocarbon gases such as C₂H₄ and C₂H₆. The volume fractions of the gases produced decrease with the increase in the distance from the explosion source. The research results boast great significance for suppressing methane explosions and their propagation in the pipeline.