Experimental Investigation of Vessel Volume and Equivalence Ratio in Vented Gas

Authors: Rafiziana M. Kasmani, Gordon E. Andrews, Herodotos N. Phylaktou, Norazana Ibrahim, Roshafima R. Ali

Abstract:

An experiment of vented gas explosions involving two different cylinder vessel volumes (0.2 and 0.0065 m3) was reported, with equivalence ratio (Φ) ranged from 0.3 to 1.6. Both vessels were closed at the rear end and fitted at the other side with a circular orifice plate that gives a constant vent coefficient (K =Av/V2/3) of 16.4. It was shown that end ignition gives higher overpressures than central ignition, even though most of the published work on venting uses central ignition. For propane and ethylene, it is found that rich mixtures gave the highest overpressures and these mixtures are not considered in current vent design guidance; which the guideline is based on mixtures giving the maximum flame temperature. A strong influence of the vessel volume at constant K was found for methane, propane, ethylene and hydrogen-air explosions. It can be concluded that self- acceleration of the flame, which is dependent on the distance of a flame from the ignition and the ‘suction’ at the vent opening are significant factors affecting the vent flow during explosion development in vented gas explosion. This additional volume influence on vented explosions is not taken into account in the current vent design guidance.

Keywords: Equivalence ratio, ignition position, self-acceleration flame, vented gas explosion.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1054741

References:

[1] European Standard : Gas Explosion Venting Guidance EN 14994:2007, 2007.
[2] D. Bradley and A. Mitcheson, The venting of gaseous explosions in spherical vessels.II-Theory and experiment , Combustion and Flame, 32, 1978b, pp. 237-255.
[3] S. Chippett, Modelling of Vented Deflagrations. Combustion and Flame, 55, 1984, pp.127-140.
[4] V.V. Molkov, Theoretical Generalization of International Experimental data on Vented Gas Explosion Dynamics, Physics of Combustion and Explosions, 25, 1995, pp. 165-181.
[5] V.V. Molkov, Unified correlations for vent sizing of enclosures at atmospheric and elevated pressures, Journal of Loss Prevention in the Process Industries, 14, 2001, pp. 567-574.
[6] NFPA 68: Guide for Venting of Deflagrations: 2007, National Fire Protection Association, 2007.
[7] D.M. Razus and U. Krause, Comparison of empirical and semi-empirical calculation methods for venting of gas explosion, Fire Safety Journal, 36, 2001, pp. 1-23.
[8] E. Runes, Explosion venting, Plant Operations & Loss Prevention, 6, 1972, pp. 63-71.
[9] R. Siwek,Explosion venting technology, Journal of Loss Prevention in the Process Industries, 9(1), 1996, pp. 81-90.
[10] W. Bartknecht, Explosions-Schultz. 1993, Berlin: Springer-Verlag.
[11] R.M. Kasmani, Willacy, S.K., Phylaktou, H.N. and Andrews, G.E., Selfaccelerating gas flames in large vented explosions that are not accounted for in current vent design, 2nd International Conference on Safety and Environment in Process Industries, Naples, Italy, 2006.
[12] European Parliament and Council Directive 1994/9/EC, The Explosive Atmosphere Directive (ATEX), 94/9/EC, 23.3.1994
[13] G. Ferrara, Benedetto, A.Di, Salzano, E and Russo, G., CFD analysis of gas explosions vented through relief pipes, Journal of Hazardous Materials, 137, 2006, pp. 654-665.
[14] R.M. Kasmani, Andrews, G.E. and Phylaktou, H.N., Experimental study on vented gas explosion in a cylindrical vessel with a vent duct, Process Safety and Environmental Protection, In Press, Corrected Proof, Available online 1 June 2012.
[15] G.E. Andrews and Bradley, D., Determination of burning velocity: A critical review, Combustion and Flame, 20, 1973, pp. 77-89.