Dynamic Characteristics of Flame near the V-gutter Bluff Body in Ducted Combustor

摘要

The dynamic characteristics of flame closed to lean blowoff were investigated in the ducted combustor with the V-gutter bluff body. The combustor has a long duct shape and rectangular cross-section. Bluff body takes the shape of an equilateral triangle. Methane(CH_4) was used as fuel, which was injected transversely into the cross-flow. Inlet air and fuel were supplied to latm, 290±1K. Inlet air velocity conditions were controlled from 10g/s to 25 g/s. Equivalent ratio was controlled between 0.45 and 1.1, respectively. In order to observe the structure and change of the flame near the bluff body, image-based methods was used such as direct photography and OH radical chemiluminescence using an ICCD high-speed camera. The blowoff equivalence ratio increased with the Reynolds number. And the blowoff equivalence ratio changed depending on the extent of the recirculation zone. When the flame closed to blowoff, recirculation zone and flame underwent a considerable change, but this phenomenon was not directly connected to the blowoff. Blowoff had a similar process, irrespective of bluff body geometry. Shortly before the blowoff, the unburned gas strongly penetrated into the recirculation zone. These made the dramatic change of the heat release in the vicinity of the bluff body. This change would be precursor to predict the blowoff. The flame was disconnected at bluff body downstream and recirculation zone was completely collapsed. The combustible mixture eventually did not ignite and the blowoff occurs.