The venting explosion process of premixed fuel vapour and air in a half-open vessel: An analysis of the overpressure dynamic process and flame evolution behaviour

Experimental study on premixed fuel-air mixture venting explosion process with various gas volume concentrations and vent sizes was conducted in a 20 L cylinder vessel. The results showed that both overpressure dynamic process and flame evolution process could be divided into 4 stages, including 2 positive and 2 negative overpressure peaks. Specifically, the 1st and 2nd positive overpressure peaks were respectively induced by flame venting and external explosion, while the 1st and 2nd negative overpressure peaks were respectively caused by expansion wave after the external explosion and external large-scale vortex. Both the overpressure and flame parameters were related to initial gas volume concentrations. As the gas volume concentration increased from 1.00% to 2.99%, both the positive overpressure peaks, flame velocity and flame propagation distance presented a first increasing and then decreasing trend, but the negative overpressure peaks and the time corresponding to each overpressure peak presented a first decreasing and then increasing trend. Moreover, as the vent coefficient K-v increased from 1.16 to 10.44, the maximum positive overpressure peaks increased from 2.32 to 60.54 mbar, and the maximum axial flame velocity increased from 9.21 m.s(-1) to 53.85 m.s(-1). However, as the K-v increased, the minimum negative overpressure peak and the maximum radial flame velocity changed non-monotonically.