The laboratory combustion technique operating on a typical combustor of a gas turbine engine is used for soot sampling. Soot particles are derived by combustion of a hydrocarbon mixture at typical cruise C 3 H 8 Èn-C 4 H 10 conditions. Size, morphology, microstructure, surface area, porosity, and the chemical nature of the soot surface particles are studied by transmission electron microscopy (TEM), Raman and Auger electron spectroscopies (AES), volumetry and gravimetry. Structural irregularities such as micropores determine the speciÐc adsorbability of non-polar gases such as Kr, and With respect to water adsorption, CH 4 C 6 H 6. aircraft combustor soot is far from being hydrophobic. Initial water adsorption on polar heterogeneities leads to pore Ðlling at increasing pressures. The microstructure of soot particles is easily transformed under the inÑuence of adsorbates, giving rise to swelling e †ects. Due to its speciÐc physico-chemical properties aircraft combustor soot may act as contrail condensation nuclei at low sulfur content in the jet fuel.

The conversion of fuel sulfur to S(VI) (SO3 + H2SO4) in supersonic and subsonic aircraft engines is estimated numerically. Model results indicate between 2% and 10% of the fuel sulfur is emitted as S(VI). It is also shown that, for a high sulfur mass loading, conversion in the turbine is kinetically limited by the level of atomic oxygen. This results in a higher oxidation efficiency at lower sulfur loadings. SO3 is the primary S(VI) oxidation product and calculated H2SO4 emission levels were less than 1% of the total fuel sulfur. This source of S(VI) can exceed the S(VI) source due to gas phase oxidation in the exhaust wake.

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