Condensation in Near-Field Airplane Exhaust Plumes

Abstract:

Aircraft engines emit carbonaceous particles and condensable gases. The exhaust is hot and at high velocity as it leaves the engine, and these conditions drive rapid mixing and cooling as ambient air is entrained in the exhaust plume. The three important classes of condensable gases in the exhaust are sulfuric acid, low-vapor pressure organic species, and water vapor. How these condensable species interact with each other and with the emitted soot particles depends on their levels and on ambient conditions. Both new particle nucleation and coatings on the soot particles can be observed in experimental data and predicted through detailed microphysical modeling. Comparisons between experimental data and model results will be presented and discussed both for ground level emissions, where sulfate and organic species are most important, and for airplanes during cruise, where water condensation and contrail formation can dominate.