EMBEDDED STRUCTURE OF RECIRCULATION ZONES IN COAXIAL DUMP COMBUSTOR WITH INNER SWIRL INLET

The new swirling chamber designed by combining swirlers with bluff bodies is considered in this paper.The cold flowfields in the coaxial dump combustor with inner swirl inlet were measured and investigated by using five-hole probes.It is found that when the flow ratio of the swirling chamber to the outer annular channel decreases and the expansion ability of outer annular flows toward the combustor wall is enhanced,a two-dimensional axisymmetrical central recirculation zone without tangential velocities occurs behind it in the dump combustor in addition to the swirling chamber recirculation zone.Both recirculation zones are embedded in each other.The swirling chamber recirculation zone not only tends to create the central recirculation zone,but also generates the suction which makes the latter bigger and stronger.Experimental results of combustion show that the high combustion efficiency is obtained as the embedded structure exists.