(673g) Studies of Soot Oxidation On a Two- Stage Premixed Burner; Effects of Temperature and Fuel Composition On the Evolution of Particle Size Distribution

Soot is commonly regarded as a pollutant which has a negative impact on human health and the environment. One of the alternative methodologies proposed to control soot emissions is the enhancement of its oxidation. For gas turbines, soot/O2 oxidation are critical to the understanding of soot oxidation since in flames oxidation is dominated by OH surface reaction. This research is focused on the soot oxidation by O2 and its main objective is to elucidate the kinetics of soot oxidation by measuring the evolution of soot structure, soot size distribution, temperature and internal surface area as a function of the height above burner. In this work, experiments are being performed in a novel, two-stage burner. In the first stage, soot is generated, while in the second stage, the soot is oxidized in either a fuel rich or fuel lean environment. The effect of temperature is studied by changing the fuel/air ratio in the system. Experiments were initially carried out on ethylene/air flame because this flame has been extensively studied and, the kinetic mechanism is well known. These experiments are supported by temperature measurements using a fast response thermocouple set-up, particle size measurements by a nano-scanning mobility particle sizer (SMPS) and transmission electron microscopy (TEM) of grids used to collect soot samples thermophoretically. The results for the lowest flame temperature in the ethylene/air flame, showed a decrease in particle diameter and an increase in particle number concentration with increasing height above burner, which indicates fragmentation of the bigger particles, while at higher elevations, the soot oxidation process was dominated by soot burnout as confirmed by particle size distribution and TEM measurements. Liquid fuels, specifically surrogates (m-xylene and n-dodecane), and fuel-lean conditions (?¶overall = 0.8, 0.875, 0.94), were also tested. Preliminary data show that the temperature effects are less likely to control fragmentation due to the amount of soot generated.