近期，我院研究生赵鹤等的“Experimental study of equivalence ratio and fuel flow rate effects on nonlinearthermoacoustic instability in a swirl combustor”的成果在期刊《Applied energy》上发表。
Industrial combustion systems such as power generation gas turbines, rocket motors, furnaces and boilers oftenface the problem of large-amplitude self-excited pressure oscillations that occur due to the onset of thermoacousticinstability. To prevent the onset of such instability, understanding the effects of fuel–air equivalence ratioϕ, fuel flow rate Vf on self-excited nonlinear thermoacoustic oscillations is of fundamental and practical importance.Experimental investigation of the roles of these parameters on triggering thermoacoustic instability in aswirl combustor has received very little attention. In this work, we design a swirling thermocoustic combustorand conduct a series of experimental tests. Autocorrelation and recurrence analysis of phase space trajectoriesreconstructed from the acoustic pressure time trace are performed. These experimental tests allow us to studythe effect of fuel–air equivalence ratio ϕ on the onset of thermoacoustic instability by varying the fuel volumeflow rate Vf. We demonstrate that the fuel volume flow rate and the equivalence ratio play different but criticalroles on generating thermoacoustic instability at different frequencies and amplitudes. Maximum sound pressurelevel can be as high as 135dB. In addition, mode switching, (i.e. frequency swap) is found to occur betweenapproximatelyω3≈ 510Hz andω1≈ 170Hz, depending on the equivalence ratio ϕ. Furthermore, the dominantfrequency corresponding to the maximum amplitude is shown to be shifted by approximately 20%, as the fuelflow rate Vf is increased and the combustion condition is changed from lean to rich. These findings are quiteuseful for designing a feedback control strategy to stabilize an unstable combustor. The present work opens upan applicable means to design a stable swirling combustor.