The effect of vent size and congestion in large-scale vented natural gas/air explosions

Abstract

A typical building consists of a number of rooms; often with windows of different size and failure pressure and obstructions in the form of furniture and décor, separated by partition walls with interconnecting doorways. Consequently, the maximum pressure developed in a gas explosion would be dependent upon the individual characteristics of the building. In this research, a large-scale experimental programme has been undertaken at the DNV GL Spadeadam Test Site to determine the effects of vent size and congestion on vented gas explosions. Thirtyeight stoichiometric natural gas/air explosions were carried out in a 182 m 3 explosion chamber of L/D = 2 and K A = 1, 2, 4 and 9. Congestion was varied by placing a number of 180 mm diameter polyethylene pipes within the explosion chamber, providing a volume congestion between 0 and 5% and cross-sectional area blockages ranging between 0 and 40%. The series of tests produced peak explosion overpressures of between 70 mbar and 3.7 bar with corresponding maximum flame speeds in the range 35 -395 m/s at a distance of 7 m from the ignition point. The experiments demonstrated that it is possible to generate overpressures greater than 200 mbar with volume blockages of as little as 0.57%, if there is not sufficient outflow through the inadvertent venting process. The size and failure pressure of potential vent openings, and the degree of congestion within a building, are key factors in whether or not a building will sustain structural damage following a gas explosion. Given that the average volume blockage in a room in a UK inhabited building is in the order of 17%, it is clear that without the use of large windows of low failure pressure, buildings will continue to be susceptible to significant structural damage during an accidental gas explosion.

The effect of vent burst pressure on a vented hydrogen–air deflagration in a 1 m3 vessel

“…However, these results do not seem to follow the findings for hydrocarbon air mixtures. In addition According to previous investigations, the first pressure peak is generated by the rupture of the vent cover [9,19,20]. Because the oscillograph and high-speed camera are triggered simultaneously, the time of the vent failure can be determined by the time when the flame vents outside the vessel.…”

Duct-vented hydrogen–air deflagrations: The effect of duct length and hydrogen concentration

“…Then, pressure wave 3 (PW3) appeared and resulted in the first pressure peak (p 1 ), and PW3 is actually the pressure wave, which resulted from burn-up in the duct (PW2 in Fig.8), rushed outside the duct. Unburned gas mixtures following PW3 were vented as shown in Fig 10(b) and (c), and a combustible gas cloud that formed in the exterior was ignited by the vented flame to result in pressure wave 4 (PW4) shown in Fig.10(d) and consequently the second pressure peak [29][30][31][32][33]. In the tests without the duct, only one dominant pressure peak was measured in the external pressure time histories, as shown in Fig.…”

CFD Simulations to Study Parameters Affecting Gas Explosion Venting in Compressor Compartments

“…The flammable gas cloud size mainly depends on the kinds of leakage sources, space dimensions, and ventilation conditions. In general, the maximum explosion overpressure would be generated when the volume ratio of gas fuel to air is close to the stoichiometric ratio [4,5]. In other words, the entire compartment filled with a gas cloud close to the stoichiometric ratio can be taken as the worst-case scenario.…”

“…The gas explosion venting characteristics are strongly dependent on ignition location [4,5]. Thus, the effect of ignition location should be discussed first.…”

“…Bauwens et al [4] studied the effects of ignition location, vent size, and obstacles on vented explosion overpressure using stoichiometric propaneair mixtures in a 63.7 m 3 vented vessel. Tomlin et al [5] performed explosion venting experiments using natural gasair mixture with chemical equivalence ratio to analyze the effects of vent area and room congestion degree in a 182 m 3 steel structure vessel. Fakandu et al [6] investigated the effect of vent burst pressure on vented gas explosion pressure in a 10 L cylindrical vessel.…”