Flame liftoff height dependence on geometrically modified bluffbodies in a vitiated flow |
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Authors: | Wookyung Kim Seong-kyun Im Hyungrok Do M Godfrey Mungal |
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Institution: | (1) Mechanical Engineering Department, Stanford University, Stanford, CA 94305-3032, USA; |
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Abstract: | In this study, the improvement of liftoff height of bluffbody-stabilized, partially premixed methane flames and the change
of flow field in the recirculation zone of bluffbodies, of variously modified base geometries, are investigated in a high
temperature (~1,315 K) vitiated flow. The basic geometry of the bluffbody consists of a two-dimensional rectangular body with
a rounded nose with fuel jets being discharged from the body at several locations upstream of the base. Flame liftoff height
measurements are characterized by CH chemiluminescence, while the three-dimensional flow field is determined using stereo
particle image velocimetry (PIV). The lowest liftoff height is observed when the geometric modifications from the original
rectangular bluffbody base are carried out such that the base has three-dimensional local cavities together with two-dimensionally
modified geometries. PIV measurements show that the improvement of liftoff height is primarily attributed to an intense recirculation
induced by multi-dimensional vortex structures in the presence of the two- and three-dimensionally modified base. |
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