Effect of square-hole obstacle in a long pipe on methane/air premixed explosion characteristics

Abstract

ABSTRACT This paper primarily studies the impact of the obstacle blocking ratios (BR) on the explosion characteristics of CH4 and Air premixed gases in cuboid pipes, a small plexiglass CH4 explosion pipe test platform of 50 mm × 50 mm × 600 mm was built independently. In this study, square-hole obstacles with different blocking ratios pressure peak set in a horizontal cuboid pipe to analyze the evolution of the explosion pressure, the shape and speed of the flame of propagation of the pre-mixed CH4/air in the pipeline. According to the results, the obstacle has a negligible impact on the initial and secondary pressure peaks, P1 and P2, However, it has a substantial impact on the P3, and the P3 only exists when there is an obstacle. As the BR increases, the time taken for the third pressure peak P3 to appear becomes shorter, the greater the pressure value. When BR = 0.75, the highest P3 recorded was 12.5 kPa and 30 kPa for methane equivalent ratios of 0.8 and 1, respectively. Compared with the non-obstacle, the square-hole obstacle in the pipe has a significant influence on the evolution of the flame shape. When there is an obstacle, after the hemispherical flame, the center position of the flame front is deformed and convex, and then the bundle flame is formed, and there is no tulip flame. Simultaneously, the presence of an obstruction results in a rise in the mean flame propagation velocity, the flame is the first to reach the location of the obstacle, when BR = 0.5. As the flame moves through the obstacle, its propagation velocity escalates with the blockage ratio’s progression.