(425a) Burnout of Soot Particles Derived From a JP-8 Surrogate in a Two- Stage Premixed Burner

Reduction of particulate emission from combustion sources is motivated by concerns about the negative impact of soot particles on human health, the environment, and engine performance. This study focuses on the mitigation of soot particles derived from a JP-8 surrogate (n-dodecane/m-xylene) flame where the enhancement of soot oxidation after it is formed arises as a potential methodology to reduce particle emissions from this type of fuel. To facilitate the understanding of the soot oxidation mechanisms from the formation steps, a two-stage burner was used. The two-stage system consists of an initial premixed burner where soot was generated under a variety of conditions. The soot-laden combustion gases were passed through a dilution/mixing zone where formation reactions were quenched and the required reactant mixture and temperature conditions for the subsequent oxidation reactions were controlled. The stream was then passed through a secondary flat-flame burner where soot was burned out under fuel lean or slightly fuel rich conditions. The process of soot burnout in the secondary burner was studied by following the evolution of particle size distribution (PSD) using a sampling dilution probe coupled to a Scanning Mobility Particle Sizer (SMPS). PSD and information obtained from flame temperature, gas-phase composition, soot surface area, soot morphology and nanostructure are allowing better understanding of soot evolution during its oxidation. Measurements of soot size distribution and number concentration as a function of the height above the second burner under fuel lean (fverall = 0.8) and slightly rich (fverall = 1.14) conditions showed particle fragmentation, evidenced by a decrease in particle mean diameter and a significant increase in number concentration in the region where O2 concentration decreased. Higher in the burner soot is burned as a result of the increase in OH* concentration. In Addition, first insights into the oxidation process using TEM and HR-TEM analysis supported the burning of particles higher in the burner and showed significant differences in soot nanostructure with increasing soot burnout.