THE INFLUENCE OF ATOMIZING AIR PARAMETERS ON SOOT FORMATION IN HEAVY LIQUID-HYDROCARBON FLAMES

The influence of the atomizing air pressure and temperature on soot formation in the turbulent diffusion flames of a mixture of heavy liquid hydrocarbons is presented. Heavy fuel oil and its water-emulsion with 10% water (E10) were used as the experimental fuels. Soot was classified as a carbonaceous residue after Soxhlet extraction of solid material that was collected on a fiberglass filter. The sizes and number densities of soot particles and aggregates as well as soot mass concentrations were determined. It was found that soot formation took place in the fuel-rich zone (high-temperature flame region: 0.2-0.4 m from the burner nozzle) while soot oxidation predominated in the fuel-lean zone (over 1.0 m from the burner). An increase in the atomizing air pressure produced more advantageous conditions for soot oxidation, counteracting soot formation in the initial zones of the flames. In the regions beyond the 'luminous flame', it caused deficiencies of oxygen and weakened of soot particles burn out. This process resulted in an increase in the size of soot particles and aggregates. It was also observed that the increase in atomizing air temperature promoted the reactions that convert precursors to soot, causing an increase in soot mass concentrations and soot particle number density in the high-temperature zone. The rise in the atomizing air temperature also favored an intensive burn out of soot in the regions near the exhaust section.