Vortex combustion in a low aspect ratio dump combustor with tapered exit

This paper reports an experimental study of the flow field in a dump combustor that has a low length/diameter ratio, tapered exit section and the combustor length is lesser than the re-attachment length. The vortex combustion phenomenon in this combustor is evaluated by the cold and hot flow field visualization studies. In the cold flow field position of the vortices and their behavior with time are illustrated. It is observed that two vortices are formed inside the combustor and the second one exhibits a cyclic behavior due to re-circulation and reversal of the flow. The hot flow field and temperature profile normal to the axis of the combustor also support this observation showing similar behavior of the vortex in the combustor. Furthermore, the flow field for reacting flow is seen to closely resemble the cold flow field, suggesting strong influence of vortex dynamics on the combustion process. The results of this study show that sustained combustion can be obtained in a low aspect ratio dump combustor without a swirler due to the flow reversal from the exit section leading to the periodic growth, convection and decay of vortices in the flow field resulting in improved fuel/air mixing.