Experimental and numerical study on the Effect of Mixture Composition on Vented Explosions

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A parametric set of vented explosion experiments for three mixtures, stoichiometric propane-air, methane-air and 18.0 vol. % hydrogen-air were performed. The three mixtures each displayed various physical phenomena and behaviors and their similarities and differences were identified. A physics based CFD model was developed, using a small subset of the experimental data, with a single set of empirical coefficients for all three mixtures. The model takes into account the effect of turbulence, flame instabilities and the Rayleigh-Taylor instability on flame propagation and pressure generation. For cases dominated by a pressure transient associated with the external explosion, the results of the simulations show good agreement between experimental and numerical results for all three mixtures, typically within the experimental uncertainty of the experiments. Further work remains on improving the model, however, particularly to account for the pressure transient generated during structure-acoustic interactions.

Venting is a commonly used method to minimize the damage done by accidental explosions. Engineering guidelines and standards exist to estimate the minimum vent size required for a given enclosure [ ], however, these standards are not sufficiently reliable. Other approaches exist [ , ], but several issues remain unresolved due to the complex nature of the phenomena and the limited set of existing experimental data.
Historically, vented explosions have proven to be a challenge to model due to the wide range of physical phenomena present, all of which directly influence the dynamics of the process [ , ]. These phenomena include Helmholtz oscillations [4, ], the external explosion [4, ], flame instabilities [4], flam...

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...on of a flame-wrinkling LES combustion model to a turbulent mixing layer,” Proceedings of the 27th Int. Symp. on Combustion, Combustion Institute, Pittsburgh, PA, 899-907 (1998).
. Bradley, D., Gaskell, P. H. and Gu, X. J., “Burning velocities, Markstein lengths, and flame quenching for spherical methane-air flames: a computational study,” Combust. Flame 104 (2): 176-198 (1996).
. Bychkov, V., “Importance of the Darrieus-Landau Instability for Strongly Corrugated Turbulent Flames,” Physical Review E 68 (2003).
. Bradley, D., Lawes, M., Liu, K., Verhelst, S. and Woolley, R., “Laminar Burning Velocities of Lean Hydrogen–Air Mixtures at Pressures Up To 1.0 MPa,” Combust. Flame, 149: 162–172 (2007).
. Zeldovich, Y. B., Barenblatt, G. I., Librovich, V. B. and Makhviladze, G. M., Mathematical Theory of Combustion and Explosion, Consultants Bureau, New York, 1985.

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