Experimental Study of the Spray Flames in a Swirl-Stabilized Can Combustor

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indicated that the high temperature zone and the recircula­tion zone were coincident. The objective of the present paper was to determined the characteristcs of the recircu­lation of the swirling spray flame for the various swi~l strength and fuel/air ratio in a swirl-stabilized dump combustor. Experiments were conducted with a 140 mm quartz tube having 140 mm diameter same as steel combustor model. Three swirlers of 8=0.3, 0.8 and 1.2 were employed. Direct photographs of the swirling spray flames were taken for different swirl numbers and fuel air rates in ord­er to obtain information pertaining to their flame shape and recirculation zone. The camera was placed at one meter dis­tance away from the centerline of the quartz combustor model · Plate 1-(a) shows an image of the brushy flame fronts for the low swirl number 8=0.3. No obvious swirling flows exist in this photograph. The reddish flames show the poor mixing between droplets and air. Plate 2-(a) was viewed from back of the combustor. There exists a small recirculation co~e but not clear surrounded by the reddish flames. The same burning condition of increasing swirl number to S=0.8 was discussed. Plate l-(b) shows a strong s~irling flow than the previous case. From this plate, the effect of the swirling flows become gradually more important on spray flames. With high swirl number, the intense blue reaction zone was limited to a region around the reaction zone near the combustor wall .It does not extend far downstream;seen in Plate 2-(b). Most of the fuel reacts outside the recirculation. The process of the fuel air mixing" starts to happen in very upstream zone near atomizer tip. The characteristics of the swirling spray flame is dominated by conditions in the neighborhood of this upstream zone. Plate l-(c) and 2-(c) showed a typi­cal strong swirling flame pattern with swirl number 5=1.2. It is seen that the droplets of the spray was more wide­spread than the weak swirl number cases. And the flame pat­tern exhibits the marked change. Based on observations of the combustion process, the recirculation zone does not ex­tend downstream beyond about 1.0 D except the weak swirl number 8=0.3.The recirculation zone is getting shorter with increasing the swirl number. The following case, we investigats the changes of the flame pattern with reducing the air flow rate. And the equi­valence ratio (E.R) of the burning spray is changed from 1.1 to 0.6 near blow-off condition. The flame pattern shows - 4 -