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Progress in Energy and Combustion Science, Vol.23, No.4, 303-347, 1997
Spray stagnation flames
Spray combustion in laminar stagnation flows is discussed. This review covers spray structures in counterflowing streams, spray counterflowing diffusion flames, spray two-stage flames in counterflowing configurations and spray combustion in jets impinging on surfaces. Its focus concerns droplet and spray characteristics and details of the flame structures. It is demonstrated that there are two qualitatively different types of spray structures. In one type of structure, some larger droplets are able to cross the stagnation plane and pass through the flames to execute underdamped oscillation in the counterflowing streams or to collide with the target wall in an impinging stream. This type of behavior occurs if the strain rate of the flow field is high and droplets in the spray are large. In the other type of spray structure, all droplets vanish at a vaporization plane before the stagnation plane and fuel vapor burns in a reaction zone in the flame, This second type of behavior occurs if the strain rate is relatively low and droplets are relatively small. The review then illustrates how the investigations on the former provide information concerning relative motion between two phases as well as droplet collision dynamics with target walls and how the studies on the latter play roles in understanding flame structure and flame chemistry of liquid fuels.
Keywords:COUNTERFLOW DIFFUSION FLAMES;HEATED FLAT PLATES;COMBUSTION;JET;IMPINGEMENT;EXTINCTION;METHANOL;DROPLET;FLOWS;EVAPORATION