Experimental characterization of aircraft combustor soot: Microstructure, surface area, porosity and water adsorption

Abstract

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 C₃H₈–n-C₄H₁₀ mixture at typical cruise 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 specific adsorbability of non-polar gases such as Kr, CH₄ and C₆H₆. With respect to water adsorption, aircraft combustor soot is far from being hydrophobic. Initial water adsorption on polar heterogeneities leads to pore filling at increasing pressures. The microstructure of soot particles is easily transformed under the influence of adsorbates, giving rise to swelling effects. Due to its specific physico-chemical properties aircraft combustor soot may act as contrail condensation nuclei at low sulfur content in the jet fuel.