Full-scale experimental study on external explosion dynamics induced by liquefied petroleum gas explosion in residential environment

With the widespread popularization of energy, gas explosion accidents in urban residential areas occur frequently. To investigate the dynamics and disaster characteristics of external gas explosions in residential environments, a 100 m2 full-scale liquefied petroleum gas explosion experimental platform was employed to study the dynamic mechanism of external explosions induced by multiple vents, as well as the propagation characteristics of shock waves and flames. Studies have shown that the long-depth and high-blocking residential environment significantly promoted flame acceleration and pressure accumulation. Under the geometric constraints of doors and windows, the shock wave focusing effect induced by the outdoor venting gas jet was enhanced, which made the Mach disk-like zone with high temperature and high pressure was easier to form and the conditions were more extreme, thus more likely to trigger high-intensity external explosion. The spatial distribution of external explosion overpressure was influenced by both the ignition position and the vent characteristics. Due to the long-distance acceleration of indoor flame and the significant formation of an outdoor Mach disk-like structure, a severe explosion with an overpressure peak of 138 kPa was generated outside the vent far from the ignition. The semi-empirical prediction model indicated that the external explosion peak overpressure exhibited a superlinear amplification pattern with respect to the indoor initial explosion intensity. The failure of multiple doors and windows resulted in multiple external explosions. The shock wave velocity fluctuated in a wavy manner due to turbulent combustion and ground Mach reflection, with the maximum velocity reaching 1079 m/s. Influenced by the external explosion, the explosion-venting flame ultimately formed an inverted spoon-shaped flame consisting of a 'stem' and a 'head'. A typical flame temperature structure of 'white flame core-orange inner flame-purple red outer flame' was formed outdoors, and finally transitioned to a temperature distribution dominated by jet flame.