Investigation of self-induced thermoacoustic instabilities in gas turbine combustors

Abstract

The self-induced thermoacoustic instabilities in partially premixed combustors remain a significant challenge which has received a limited research attention. This numerical work investigates the effect of air-fuel equivalence ratio ∅ on exciting thermoacoustic instabilities and its impact on the characteristics of both the acoustic and combustion fields in a partially premixed swirl combustor. For this purpose, three sets of numerical investigations are studied. The first set is a comparison between the present numerical study and previous experimental work considering the normalized combustor wall temperature. The second set of simulations is performed to predict the behavior of the reacting and non-reacting flows with regard to pressure fluctuations, power spectral density, and the sound pressure levels. The third set of simulations considered the effect of the air-fuel equivalence ratio on the acoustics and combustion characteristics. The results reveal that at an equivalence ratio of 0.5, the sound pressure level for the non-reacting and reacting flows are 98 and 118 dB, respectively. It is concluded that the equivalence ratio plays a crucial rule on exciting combustion instabilities at various amplitudes and frequencies. The sound pressure levels increase with increasing in the air-fuel equivalence ratio due to increase the heat release rate.