Abstract: In order to explore the natural gas venting process of internal pressure change law, the use of 10 L plexiglass pipeline experimental device for a series of methane—air premixed gas explosion test. Thus, based on these experiments, this study analyzed the change relationships between peak overpressure, the peak overpressure duration, Helmholtz oscillation rate, and the leakage and explosion area when the premixed methane—air gas leaking and exploding in the scenarios of blockage in the end of pipe and in the middle of pipe. Research results show that, in the scenario of end blockage, both the pre—peak and post—peak overpressure increase with the decrease of the leaking and exploding area, while in the scenario of middle blockage, the post peak overpressure located outside the explosion pipe and inside the transmission pipe continuously decreases with the decrease of the leaking and exploding area. In terms of peak overpressure duration, there is little relationship between the duration of the pre—peak overpressure and the explosion area, while the duration of the post—peak overpressure is significantly affected by the leaking and explosion area. There is no consistency in the variation of explosive pressure rise rate in the scenarios of middle blockage and end blockage. In the scenario of middle blockage, the explosive pressure rise rate first increases and then decreases with blockage rate, and a maximum value appears at 60% blockage rate. In the scenario of end blockage, the explosive pressure rise rate decreases first and then increases with the blocking rate, and a minimum value appears at 60% blocking rate.

Key words: premixed methane—air gas, leaking and exploding process, pressure changes, overpressure duration, pressure rising rate, blocking ratio, peak overpressure