Experimental and Numerical Investigations of Soot Suppression in Diffusion Flames of Oscillating Acetylene

Combustion-generated soot remains a significant environmental and health concern, necessitating effective mitigation strategies. This study investigates the suppression of soot in acetylene diffusion flames through fuel flow oscillation, employing both experimental and numerical approaches. The effects of relative amplitude (Aout) on soot production rates (Rsoot) and sound pressure level (SPL) were examined across a range of excitation frequencies (f from 25 to 1200 Hz), acetylene flow rates (QC2H2), and nozzle inner diameters (Din from 1.05 to 6 mm). Additionally, the formation of standing acoustic waves was analyzed to reduce energy consumption. Results indicate that Rsoot is minimally influenced by QC2H2 but is predominantly controlled by the ratio Aout/Din. There exists an optimal f at which both Rsoot and SPL reach their minima when Aout/Din ≤ 2 mm–1, highlighting the role of combustion-acoustic coupling. Notably, the SPL increases sharply with ignition intensification. When standing waves are established within the fuel delivery tube, Rsoot can be reduced by 96.7% with a remarkably low speaker power of only 1.4 mW. These findings demonstrate a promising, energy-efficient method for soot mitigation in combustion systems through controlled acoustic oscillations.