Soot suppression by nonthermal plasma in coflow jet diffusion flames using a dielectric barrier discharge

The effect of nonthermal plasma on diffusion flames in coflow jets has been studied experimentally by adopting a dielectric barrier discharge (DBD) technique. The plasma reactor had wire-cylinder-type electrodes with AC power supply operated at 400 Hz. The effect of flame on the behavior of electrical discharge was first investigated to identify the regime of plasma generation, discharge onset voltage, and delivered power to the plasma reactor. The generation of streamers was enhanced with a flame by the increase in the reduced electric field intensity due to high-temperature burnt gas and by the abundance of ions in the flame region. The effect of streamers on flame behavior reveals that the flame length was significantly decreased as the applied voltage increased. The yellow luminosity by the radiation of soot particles was also significantly diminished. The temperature of burnt gases, the concentrations of major species, and the spatial distribution of OH radical, PAH, and soot have been measured. The formation of PAH and soot was influenced appreciably by the nonthermal plasma, while the flame temperature and the concentration of major species were not influenced much with the plasma generation. The results demonstrated that the application of nonthermal plasmas can effectively suppress PAH and soot formation in the flames with low power consumption even in the order of 1 W.