FLAME-VORTEX INTERACTION IN A REACTING VORTEX RING

Direct numerical simulations are used to study the flame-vortex intera ction in a laminar reacting vortex ring. The chemical reaction occurs by a one-step, Arrhenius-type reaction that mimics the combustion of t ypical hydrocarbon and air. The ring is generated by an axisymmetric j et that is impulsed to emit a cold fuel through a nozzle. The fuel ent ers a quiescent ambient at a much higher temperature. By adjusting the ratio of the ambient and fuel temperatures, the ignition either occur s during the formation or post-formation phase of the ring. When ignit ion occurs during the formation phase of the ring, the bulk of combust ion is by a flame at the front of the vortex bubble. When ignition is delayed until after the formation phase, most of the reaction occurs i nside the vortex ring. It is found that premixing the fuel and the oxi dizer enhances the amount of product formation. The heat released from the reaction significantly affects production, redistribution, and di ffusion of the vorticity throughout the field. The results of the simu lations also reveal that the heat of reaction affects the strain rate fields differently depending on when the ignition of the ring occurs. (C) 1998 American Institute of Physics.