Experimental investigation on thermoacoustic oscillation of a new dual-swirl combustor

In this paper, a new type of dual-swirl combustor is tested. The effects of two varying processes of combustion state parameters on the thermoacoustic oscillation characteristics of flame are studied. The two processes are: keep methane volume flow rate constant and reduce the equivalence ratio from 0.900 to 0.725 and then increase it back to 0.925; keep the equivalence ratio constant as 0.850 and increase the premixed gas volume flow. The results show that there are two distinct flame patterns of M-shaped and V-shaped in this combustor. In process 1, the flame changes from unstable M-shaped flame to stable V-shaped flame with decreaseing equivalence ratio, and then changes to M-shaped flame with increaseing equivalence ratio, the combustor exists hysteresis phenomenon; In process 2, Thermoacoustic oscillation is only found at the initial flow rate, and the flame becomes stable with increaseing flow rate.Through the analysis of the power spectrum characteristics and phase space reconstruction of the pressure fluctuation signal, it is found that there are unstable frequencies around 400.0 and 256.0 Hz in this dual-swirl combustor.