Passive control of premixed lifted flame in a dump combustor

This paper reports an experimental investigation of the dynamics of premixed lifted flame inside a dump combustor with tapered exit. The pressure and heat release measurements along with flame visualization were carried out to understand the combustion phenomenon inside the combustion chamber. High levels of combustion driven oscillations in pressure were observed in the lifted flame due to the coupling of the heat release and flow oscillations. The dominant mode of oscillations was seen to be governed by the convection of hot burned gases into the combustion zone due to flow reversal from the exit section. The fluctuations of pressure decreased in the presence of a stabilizing rod due to mistuning of heat release and pressure oscillations resulting in a decrease in their correlation and coupling as the dominant frequency of oscillation in the presence of rod resembled the frequency of vortex shedding from the rod. Consequently, a 4 dB decrease in overall sound pressure level could be achieved by passive control in the dump combustor.