Relating Physicochemical Properties of the Aerosols Emitted from Jet Aircraft to Contrail Formation

ANSON REGI, Connor Malley, Sungho Hwang, Tonghun Lee, Vishal Verma, University of Illinois Urbana Champaign

     Abstract Number: 526
     Working Group: Aerosols, Clouds and Climate

Abstract
Condensation trails (Contrails) are linear clouds that are formed in the upper troposphere (10-14 km) by water vapor condensing onto aerosols present in aircraft engine exhaust. Contrails can persist as cirrus-like clouds and contribute to radiative forcing, with a net positive effect. A key component in contrail formation is the presence of soot particles from fuel combustion, which act as nuclei for ice crystals to form. The objective of this study is to examine critical soot properties, e.g. primary particle diameter (D_p), mobility diameter (D_m), specific surface area (SSA), porosity (Φ) and chemical composition, and how they impact the ice nucleating potential (INP) of soot particles.

Representative soot particles were generated by the combustion of aviation fuels like Jet-A and Sustainable Aviation Fuel (SAF) in a lab-scale combustor. These particles are then sampled and imaged using Transmission Electron Microscopy (TEM) to determine D_p. Brunauer-Emmett-Teller (BET) analysis is employed to quantify SSA and porosity using nitrogen gas adsorption. The emissions are simultaneously collected onto quartz filters for elemental and organic carbon analysis while a part of it is diluted and directed to a Scanning Mobility Particle Sizer to assess D_m. The INP of soot particles are analyzed by channeling these emissions into an atmospheric chamber that simulates upper tropospheric temperature, pressure and relative humidity.

Preliminary results indicate that D_p of soot generated from Jet-A fuel combustion is in the range of 20-40 nm, and the SSA is 49.4 m²/g. The development of the atmospheric chamber for the measurement of ice nucleation is in process and the results investigating the relationship between these physicochemical parameters and INP will be presented. Our future efforts are directed towards developing a predictive model to link these properties of the generated soot with its INP.