Experiments were performed to examine cluster formation when simulated engi
ne exhaust gas passes through an atmospheric pressure plasma discharge cell
at 180 degrees C. The gas composition included N-2, NO, CO, CO2, C3H8, C3H
6, Ar, H-2, H2O, O-2 and SO2. Aerosol particles or clusters were measured a
fter the gas was treated with a dielectric barrier discharge, although the
quantity of clusters generated was several orders of magnitude smaller than
normal engine emissions. The clusters were not formed when water was not p
resent in the mixture. The number and size of clusters increased when hydro
carbons were not present, although the quantity was still very small. Metho
ds to describe cluster formation phenomena are discussed. (C) 2000 American
Institute of Physics. [S0003-6951(00)00821-4].