Abstract
Soot samples were extracted from a swirl-stabilized, liquid-fuel fired laboratory combustor to (i) assess the validity of the ASTM smoke point test in predicting the sooting characteristics of fuels in complex combustion systems and (ii) assess the effect of fuel molecular structure and smoke suppressant additives on the physical and chemical properties of soot. Fuels utilized were shale JP-8, iso-octane, and blends of iso-octane with either decalin, toluene, tetralin, or 1-methylnaphthalene such that smoke points similar to JP-8 were achieved. Each fuel was separately blended with 0.05 percent (by weight) ferrocene smoke suppressant. The results indicate that the ASTM test can be misleading, increased fuel molecular complexity increases soot content of higher molecular weight polycyclic aromatics, and ferrocene additive reduces small particle number density but not necessarily the soot mass loading.
Highlights
With the continued consumption of petroleum resources outpacing discovery, the use of fuels derived from shale and coal is evolving as a practical alternative for jet fuels
The soot weight concentrations of iso-octane and the pure fuel blends were consistent with the sooting propensity indicated by the ASTM method, whereas the soot weight concentration of the chemically complex shale JP-8 was significantly higher (>400 percent) than the soot weight concentrations produced by the fuel blends prepared with a similar smoke point
The weight concentration results obtained with the ferrocene additive (Table 3) divide into two distinct groups - a general increase in the particulate weight concentration, and a substantial reduction in particulate weight concentration
Summary
With the continued consumption of petroleum resources outpacing discovery, the use of fuels derived from shale and coal is evolving as a practical alternative for jet fuels. The widespread use of these synfuels in aircraft propulsion and power generation systems will depend on overcoming the propensity of these fuels to form soot. Approaches under consideration to reduce this soot production include the future development of fuel-flexible gas turbines through combustor modification and the use of smoke suppressant fuel additives for the current generation of gas turbines. Two questions arise in the resolution of problems associated with the use of liquid synfuels in complex (i.e., recirculating and turbulent) flows typical of gas turbine combustors. Such information could provide direction for the use of additives in suppressing the soot production in existing engines and identify paths for combustor modification in generation gas turbines. What methods are appropriate for testing the sooting propensity of fuels in complex flows? What methods are appropriate for testing the sooting propensity of fuels in complex flows? In
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