Investigation on the characteristics of vented stoichiometric methane-air explosion: Effect of ignition positions and obstacles

In this study, the effect of ignition positions and obstacles on the vented stoichiometric methane-air explosion is investigated experimentally in a 20L vessel with a 4.5 m long tube. Explosion overpressures are recorded by pressure transducers (CYG1508GSLF), and a high-speed camera is employed to observe the process of the flame propagation. The results indicated that the peak overpressure, pressure rising rate in explosion vessel and the secondary explosion strength in vented tank all are increased obviously with the decrease of the distance be-tween ignition position and vent. Especially at the end of the explosion vessel, the peak overpressure can be increased from 125 kPa at ignition position 1 to 619 kPa at ignition position 4. The pressure rising rate at ignition position 4 is 410 % higher than that obtained at ignition position 1. In addition, the explosion parameters also closely depend on the obstacle thickness and blockage ratio. When the thickness of the film obstacle increases from 0 mm to 0.4 mm, the peak overpressure and the pressure rising rate are increased by 48 % and 337 %, respectively. As the blockage ratio of orifice plate reaches 80 %, the explosion overpressure is dropped sharply, and there no the secondary explosion can be observed in the vented duct.