The effects of fuel chemical composition on particulate matter (PM) emissions of a T63 engine were investigated. Fuels with different aromatic, cycloparaffin (naphthene), iso-paraffin and normal paraffin levels were evaluated in the turboshaft engine and compared to the performance of a typical JP-8 fuel. The fuels studied include: a semi-synthetic jet fuel, two high naphthenic experimental fuels, three Exxon solvents (Isopar M, Isopar H and Norpar-13) and methylcyclohexane. The effect of blending solvents in JP-8 on PM emissions was also assessed. Commercially available particulate instruments were used to measure particle number density, particulate mass concentration and particle size distribution. Results showed a general trend of higher particulate concentrations and larger diameter soot particles with decreasing fuel hydrogen-to-carbon (H/C) ratio or increasing aromatic content. However, for several fuels with approximately the same H/C ratio, significant differences in PND and calculated mass were observed. Furthermore, blends of JP-8 with solvents of similar H/C ratio but varying chemical composition produced significantly different particulate emissions. These findings demonstrate that particulate emissions from hydrocarbon-fueled combustion processes are not solely a function of the H/C ratio or aromatic concentration of the fuel, but that other properties or constituents also impact soot emissions. Chemical and physical properties of the fuels and their potential effect on particulate emissions are discussed. These findings provide insight into fuel properties that impact PM emissions, which may aid in the development of fuel additives to reduce particulate emissions from turbine engine combustors.

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