Effect of the Position of the Centerbody on Thermoacoustic Instabilities in a Central-Staged Model Combustor

Abstract

Abstract The present study investigates the effect of the position of the centerbody on thermoacoustic instabilities in a central-staged model combustor with a dual-swirl layout. The position of the centerbody significantly influences the combustor’s vortex breakdown and combustion performance, such as combustion instability. In this paper, three different axial positions of the center body are studied experimentally under atmospheric pressure and temperature with premixed methane-air mixtures. The result shows that the position of the center body alters the pilot flame shape, and then the overall flame shape changes, no lifted flames have been discovered in the case of the center body in the Down-5mm. The degradation of the centerbody also could increase the amplitudes of pressure oscillation in the combustor. Moreover, the dominant frequency of oscillation is different with different positions of the center body. The beating oscillations are also found in three positions of the center body. Flame dynamics are further analyzed using the Dynamic Mode Decomposition method. It is concluded that the cases of the center body downstream have the best thermoacoustic stability within the tested range of three cases. The flow mechanisms of three different center body positions have been revealed using the numerical simulation of RANS. It is found that the degradation of the center body could decrease its ability of stabilized the pilot flame and then decrease the thermoacoustic stability.