Research on the effect of the vent area on the external deflagration process during the explosion vent

Abstract

Explosion-vent area is an important parameter for pressure vessel explosion vent design, which is of great significance to the safe operation of pressure vessels. The phenomenon of external explosion occurs outside the vent when the pressure vessel vents. The impact of explosion vent area on the external explosion was researched by numerical simulation in this paper. The results show that the impact of the explosion vent area on the external explosion is relatively significant. The large vent area has a larger area of high pressure, higher pressure and higher fluid turbulence intensity outside the vessel, which leads to more powerful explosion intensity. The smaller vent area leads to weaker external explosion intensity, but leads to higher pressure values inside the vessel. Additionally, the pressure-relief process of vessel with smaller vent area tends to form a “jet fire” and the pressure-relief efficiency is low, in which process, the external flame’s shapes show a long strip. The pressure-relief form of vessel with larger vent area tends to “external explosion” and the process of pressure relief is quicker, in which process, the shape of the external flame showing a “spherical”. Gas from the vent, the under-expansion flow in high-pressure develops into sub-atmospheric in process of moving forward, which can be compressed by surrounding air to intensify the thermochemical reaction, thus prompting the occurrence of external explosions. The larger the venting area is, the quicker the dissipation of the high-pressure area appears. As a result of the external explosion, the Helmholtz oscillation appears inside vessels. Larger vent area leads to larger amplitude and higher frequency of Helmholtz oscillations, in which process, the duration of Helmholtz oscillations is longer.