Experimental Study on Soot Suppression of Acetylene Diffusion Flame by Acoustic-Excited Oscillation in Rijke-Type Burner

This work reports that the flame oscillation induced by acoustic excitation can effectively suppress soot generation in Rijke-type burners. When the acoustic frequency is close to the natural frequency of the burner system, it can produce resonance resulting in intense oscillation of the flame. The relationship between the soot suppression efficiency and the acoustic field of standing wave at different flame positions is discussed. Compared with that under self-excited oscillation, when there is external forced acoustic force introduced to the flame, oscillation combustion occurred in a lager zone in the glass tube. The fundamental cause of different soot suppression efficiency at different positions is that the standing wave acoustic field causes the particles to move at different speeds in different positions of the glass tube. The axial particle velocity difference results in the formation of acoustic vortexes and the change of the flame shape. The high particle velocity causes the air in the glass tube to turn into the turbulent condition and make the flame temperature rise. Simulation results show that the surface growth rate of soot is reduced, while the oxidation rate of soot is enhanced, which result in the soot suppression under acoustic oscillation. This study can provide some reference for the practical application of oscillate combustion in soot suppression.