On the propagation of partially premixed flame spanning a wide range of gravity levels

摘要

Methane-air edge flames in two-dimensional mixing layers under different equivalence ration gradients and gravity levels are numerically simulated. Edge flame propagation speed (U_(edge)) is estimated through dynamic balance between flame propagation and flow field. Edge flames were found to be stabilized under large positive gravity level, while it would propagate unstably under large negative gravity level due to vortex appearance. Uedge of stably propagating flame increases with increasing gravity level. The dependence of normalized U_(edge) on gravity level can be described through a theoretical mathematic form with good agreement within a wide gravity level range (from -10g to +50g). The re-direction effect of flow field is influenced by buoyant convection and its strength increases with increasing gravity level and thus Uedge increases consequently. For unstably propagating flame, double vortices can be generated between flame and the side wall due to buoyant convection. Flame propagation would be influenced by these vortices, which leads to unstable propagation.