Mechanical model of domestic gas explosion load

Abstract

With the increase of domestic gas consumption in cities and towns in China, gas explosion accidents happened rather frequently, and many structures were damaged greatly. Rational physical design could protect structures from being destroyed, but the character of explosion load must be learned firstly by establishing a correct mechanical model to simulate vented gas explosions. The explosion process has been studied for many years towards the safety of chemical industry equipments. The key problem of these studies was the equations usually involved some adjustable parameters that must be evaluated by experimental data, and the procedure of calculation was extremely complicated, so the reliability of these studies was seriously limited. Based on these studies, a simple mathematical model was established in this paper by using energy conservation, mass conservation, gas state equation, adiabatic compression equation and gas venting equation. Explosion load must be estimated by considering the room layout; the rate of pressure rise was then corrected by using a turbulence factor, so the pressure-time curve could be obtained. By using this method, complicated calculation was avoided, while experimental and calculated results fitted fairly well. Some pressure-time curves in a typical rectangular room were calculated to investigate the influences of different ignition locations, gas thickness, concentration, room size and venting area on the explosion pressure. The results indicated that: it was the most dangerous condition when being ignited in the geometry centre of the room; the greater the burning velocity, the worse the venting effect; the larger the venting pressure, the higher the peak pressure; the larger the venting area, the lower the peak pressure.

Keywords

gas explosion / mechanical model / venting / peak pressure / turbulence factor

References

[1] Pearson C., Delatte N.. Ronan point apartment tower collapse and its effect on building codes[J]. Journal of Performance of Constructed Facilities, 2005, 19(2): 172-177.

[2] Kobiera A., Kindracki J., Zydak P., et al. A new phenomenological model of gas explosion based on characteristics of flame surface[J]. Journal of Loss Prevention in the Process Industries, 2007, 20(3): 271-280.

[3] Lu J., Ning J., Wang C., et al. Study on flame propagation and acceleration mechanism of city coal gas[J]. Explosion and Shock Waves, 2004, 24(4): 305-311.

[4] Yu L., Sun W., Wu C.. Flame propogation of H₂-air in a semi-open obstructed tube[J]. Journal of Combustion Science and Technology, 2002, 8(1): 27-30.

[5] Wang Z.. Study on the Dynamics of Gas Explosion Process in Confined Space [D]. 2005, Nanjing: Nanjing University of Technology.

[6] Li Yue, Wang Shulan, Ding Xinwei. Experimental investigation on explosion venting of flammable gas in spherical vessels [J]. Natural Gas Industry, 2004 (7): 104–107(in Chinese).

[7] Moen I O. The influence of turbulence on flame propagation in obstacle environment [C]. In: First International Specialist Meeting on Fuel-Air Explosions. Montreal, 1982: 101–135.

[8] Hijertager B. H., Fuher K., Parker S. J., et al. Flame acceleration of propane-air in a large scale obstructed tube [C] Progress in Astronautics and Aeronautics, 1984, New York: AIAA Inc 504-522.

[9] Canu P., Rota R., Carra S.. Vented gas deflagrations: A detailed mathematical model tuned on a large set of experimental data[J]. Combustion and Flame, 1990, 80 49-64.

[10] Dobashi R.. Experimental study on gas explosion behavior in enclosure[J]. Journal of Loss Prevention in the Process Industries, 1997, 10(2): 83-89.

[11] Molkov V., Dobashi R., Suzuki M., et al. Modeling of vented hydrogen-air deflagrations and correlations for vent sizing[J]. Journal of Loss Prevention in the Process Industries, 1999, 12(2): 147-156.

[12] Molkov V., Dobashi R., Suzuki M., et al. Venting of deflagrations: Hydrocarbon-air and hydrogen-air systems[J]. Journal of Loss Prevention in the Process Industries, 2000, 13(3/4/5): 397-409.

[13] Qian X., Chen L., Feng C.. Simulation analysis of indoor gas explosion damage[J]. Journal of Beijing Institute of Technology, 2003, 12 286-289.

[14] Bradley D. H., Hicks M. Z., Kitagawa R. A., et al. Turbulent burning velocity, burned gas distribution, and associated flame surface definition[J]. Combustion and Flame, 2003, 133 415-430.

[15] Razus D. M., Krause U.. Comparison of empirical and semi-empirical calculation methods for venting of gas explosions[J]. Fire Safety Journal, 2000, 36 1-23.

[16] Gao J.. Damage of Indoor Gas Explosion in Domestic Buildings [D]. 1991, Beijing: Tsinghua University.

[17] Kumar R. K., Dewit W. A., Greig D. R.. Vented explosions of hydrogen-air mixtures in a large volume[J]. Combusion Science and Technology, 1989, 66 251-266.