Experimental and numerical investigation of methane ignition and flame propagation in cylindrical tubes ranging from 5 to 71 cm – Part I: Effects of scaling from laboratory to large-scale field studies

• Methane-air flame burning velocities are explored as a function of scale.
• ANSYS Fluent was used to simulate methane-air flame propagation.
• An empirical correlation between tube size and burning velocity is provided.

A firmer understanding of the dependence of flame characteristics as a function of scale is needed to describe methane driven longwall coal mine explosions, which are among the largest industrial explosions. Toward this goal, experimental and numerical investigations of methane combustion and flame propagation in horizontal cylindrical tubes as a function of stoichiometry and tube diameter were carried out. The effect of ignition location was also investigated for stoichiometric air-fuel conditions with ignition at the closed–end of the reactor producing a significant increase in burning velocities on the order of 2–4 times faster as the diameter of the reactor was increased. In the experimental section, horizontal tubes were used with one end allowed to vent to the atmosphere, and the other end a solid wall. Tubes with diameters ranging from 5 to 71 cm were used. It is found that maximum laminar flame propagation velocity increases with tube diameter. 2-D numerical simulations for these tubes were carried out with ANSYS Fluent. A hot-wall was used as an ignition source, with burning velocity trends consistent with experimental data. A functional relationship between stoichiometric uniform burning velocity and tube diameter is presented.