Experimental Investigations of the Flow Field Structure and Interactions between Sectors of a Double-Swirl Low-Emission Combustor

In this paper, the flow field characteristics of a double-swirl low-emission combustor were analyzed by using Particle Imaging Velocimetry (PIV) technology in an optical three-sector combustor test rig. The interactions between sectors and the flow field structure were explained. The results illustrated that there was a big difference between the flow field structures of the middle sector and the side sector under the same pressure drop, which was mainly induced by the interactions between sectors. The interactions made the swirl intensity of the middle sector weaker than that of the side sector, which made the recirculation zone of the middle sector be smaller than that of the side sector. With the increase of swirler pressure drop, the jet velocity at the exit of the swirler, the jet expansion angle, the width of the recirculation zone and the recirculating speed of the central axis became larger, enhancing the interactions between air streams from middle sector and side sector. The flow velocity in the central plane between sectors was small, especially the radial velocity, mainly because of the loss of the swirl intensity by the interactions between flow field of adjacent sectors. The expansion angle determined the position of the vortex in the primary recirculation zone; the axial and radial position of the vortex move downstream and radial outward with the increase of the jet expansion angle. The results of the mechanism of flow field organization in this study can be used to support the design of new low-emission combustor.