Propagation of a confined explosion to an external cloud

Abstract

Since the pioneering work of Harrison and Eyre (1986), the existence of secondary or external explosion outside explosion vents is recognized. It was later shown (Proust, 2004(Proust, , 2010) that the phenomenon is rather systematic and that this explosion can be much more powerful than the internal explosion particularly when the mixture is very reactive. But today, the understanding of the formation of the external cloud and its subsequent combustion remains largely outstanding. Very rapid burning was noticed and significant UVCE pressure effects. In some circumstances, a preexisting flammable cloud encompasses the vented vessel, like in Buncefield for instance. What would happen if the cloud is ignited inside the vessel resulting in an external explosion developing inside the preexisting flammable cloud ? In this paper, new information is presented about the physics of the external explosion and the subsequent combustion of outside cloud. Experiments and numerical simulations were performed.

Experimental study on dust explosion vented through a bent duct

“…Gao et al, 3,4 Tascón et al, 5 and Yan and Yu 6 focused on the influence of different static activation overpressures on the venting overpressure within the vessel using traditional venting techniques. In addition, the influence of the vent area has been extensively studied 7‐9 . Tascón et al 10‐12 also confirmed above influencing factors (static activation overpressure and vent area) by numerical simulations with FLACS‐Dust Ex software.…”

Experimental Study of External Flame Evolution and Temperature Characteristics after a Methane Explosion in a Rectangular Chamber

“…Results obtained by Proust et al 24 showed that a jet flame occurs under conditions of rear ignition in the case of a small vent area similar to that in the current study (Figure 2(a)). However, no mushroom-like flame was observed at the vent area of 0.16 m 2 , which was also obtained by Jeŕome et al, 27 because a small vent area permits only a slower gas-venting rate so that the combustion rate in the chamber exceeds the venting rate during venting. 5 Therefore, the internal pressure in a high-pressure state after opening the vent causes a continuous and rapid discharged velocity, moving the vented gas away from the vent.…”

“…The largest length of jet flames is closely linked to the hydrogen equivalence ratio. Jérôme et al 27 clarified the fact that, in the case where the discharge area is sufficiently small, the external vortex bubble formed by the ejection is disturbed to form a jet flame. By measuring the speeds of laminar flames of a methane–air mixture in a bomb of a constant volume and shock tube, Hu et al 28 found that a faster laminar flame speed of the methane-rich mixture was measured using the linear approach compared with that predicted using a nonlinear approach.…”