AEROSOL DYNAMICS IN NEAR-FIELD AIRCRAFT PLUMES

A numerical model including gas phase HOx, NOx, and SOx chemistry, H2S O4-soot adsorption; binary H2SO4-H2O nucleation; aerosol coagulation; and vapor condensation is used to investigate aerosol formation and gr owth in near-field aircraft plumes. The plume flow field is treated us ing the JANNAF standard plume flow field code, SPF-II. Model results a re presented for a Mach 2.4 high-speed civil transport at 18 km altitu de and 85 degrees N latitude and a subsonic Boeing 707 at 12.2 km, 47 degrees N. The results, based on hydroxyl radical driven oxidation kin etics, indicate that 1-2% of the emitted SO2 is converted to H2SO4 in the near-field exhaust (1-2 s) and that for typical exhaust SO2 emissi on indices (approximate to 1 g kg-fuel) the plume is supersaturated wi th respect to both the pure liquid acid and H2SO4/H2O solutions. Class ical nucleation theory predicts high levels of small (0.3-0.6 nm radiu s) H2SO4/H2O embryos. Coagulation and gas-to-particle conversion are f ollowed to provide estimates for the number density of activated soot particles capable of serving as condensation nuclei for contrail forma tion. Results are presented illustrating the dependence of water conde nsation on the number density and size distribution of activated exhau st soot nuclei.