DILUTION OF AIRCRAFT EXHAUST PLUMES AT CRUISE ALTITUDES

The dilution of jet engine exhaust in the plume behind cruising aircra ft is determined from measured plume properties. The data set,includes in situ measurements of CO2, NO, NOy, SO2, H2O, temperature, and cont rail diameters behind subsonic and supersonic aircraft in the upper tr oposphere and lower stratosphere, for plume ages of seconds to hours. The set of data is extended into the range of milliseconds based on co mputations and measured temperature values. The bulk plume dilution is expressed in terms of the dilution ratio N which is the mass of air w ith which the exhaust from a unit mass of burned fuel mixes. For: 0.00 6 s < t < 10(4) s, the bulk dilution ratio measured in more than 70 pl ume encounters follows approximately N = 7000(t/t(0))(0.8), t(0) = 1 s . (C) 1998 Elsevier Science Ltd. All rights reserved.