Abstract: In order to explore the propagation characteristics of urban gas explosion in the confined space of civil building structures, a circular explosion shock pipe with a length of 12 m and an inner diameter of 90 mm was used to simulate the real explosion scenario, and biaxial stretched polypropylene film (BOPP film) was used as flexible obstacles to simulate destructive building structures such as doors and windows. A methane/air premixed gas explosion experiment with a volume fraction of 9.5% was carried out. The results show that the flexible obstacle film made of polypropylene material has a significant influence on the excitation effect of methane explosion, which can change the evolution process of pressure wave system and accelerate the flame propagation speed. After the film breaking, the pressure wave changes from a continuous weak disturbance wave to a sudden shock wave, and the maximum flame propagation speed increases to 177.30 m/s, which is 3.37 times that of the maximum flame propagation speed under the condition of no film. The gas conditions before and after the film also have a significant influence on the explosion pressure. If the region behind the film is combustible gas, the flame moving at high speed after the film is broken will react with the combustible gas and produce detonation phenomenon, making the maximum pressure as high as 1 634.08 kPa and the maximum flame propagation velocity as high as 671.14 m/s. At the same time, Schlieren technique was used to record the superposition of new shock waves and multi-channel shock waves during the evolution of wave system after film breaking.

Key words: confined space, shock wave tube, flexible obstacles, methane explosion, shock wave