Numerical investigation on flame propagation in vented gas explosion

Abstract

Explosion venting technology is one of the effective and widely used methods in protection measures against accidental internal gas explosions by relieving the pressure generated within the volume. Extensive studies have been carried out to investigate factors governing to the explosion development i.e. ignition position and vent burst pressure. However, the physical and dynamic process of explosion development during the venting to ambient air is yet not well understood. The primary motivation of this research was to gain improved understanding of turbulent flame propagation in vented gas explosion, with a view to develop improved models and methods for assessing explosion risks in the process industries. Computational Fluid Dynamic (CFD) analyses using FLUENT is adopted to study the phenomenology underlying vented gas explosions. Computations were run on deflagrating turbulent flames in small-scale combustion chambers with two different volumes (0.02 m3 and 0.0065 m3), with both closed at the rear end and open at the opposite face, in order to replicate the experimental work. All cases are initialised from stagnation. Only stoichiometric concentration of propane and methane-Air mixtures was considered with different ignition positions and vent static burst pressure, Pv. From the finding, end ignition gave higher reduced overpressure on both experimental and simulation results, compared to central ignition. The inclusion of vents in the enclosures provides significant reduction on the peak overpressures. However, it has been recognised on a tendency to a less effective reduction as the vent burst pressure, Pv was further increased. The competition between combustion rate and venting rate allows the explanation on both number and intensity of the overpressure peaks observed in propane-Air explosion.