Influence of gas compressibility on a burning accident in a mining passage

Abstract

A recent predictive scenario of a methane/air/coal dust fire in a mining passage is extended by incorporating the effect of gas compressibility into the analysis. The compressible and incompressible formulations are compared, qualitatively and quantitatively, in both the two-dimensional planar and cylindrical-axisymmetric geometries, and a detailed parametric study accounting for coal-dust combustion is performed. It is shown that gas compression moderates flame acceleration, and its impact depends on the type of the fuel, its various thermal-chemical parameters as well as on the geometry of the problem. While the effect of gas compression is relatively minor for the lean and rich flames, providing 5–25% reduction in the burning velocity and thereby justifying the incompressible formulation in that case, such a reduction appears significant, up to 70% for near-stoichiometric methane–air combustion, and therefore it should be incorporated into a rigorous formulation. It is demonstrated that the flame tip velocity remains noticeably subsonic in all the cases considered, which is opposite to the prediction of the incompressible formulation, but qualitatively agrees with the experimental predictions from the literature.

Keywords:

• gaseous–dusty combustion
• gas compression
• Darrieus–Landau instability
• expanding and finger flames
• flame acceleration
• mining fire safety

Acknowledgements

The authors thank Ali S. Rangwala of Worcester Polytechnic Institute for useful discussions. This work is sponsored by the US National Science Foundation (NSF), through the CAREER Award #1554254 (V.A.), prior to which this research was supported by the Alpha Foundation for the Improvement of Mine Safety & Health, Inc., through the Award #AFSTI14-05 (V.A). The views, opinions and recommendations expressed herein are solely those of the authors and do not imply any endorsement by the Alpha Foundation, its directors and staff.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Alpha Foundation for the Improvement of Mine Safety & Health, Inc. [grant number #AFSTI14-05]; US National Science Foundation (NSF) [grant number CAREER #1554254].