DEFINITION:

These topics are of the most importance in the actual context. The emissions of the turbojets are produced by the combustion. They are of two categories : minor and major species. Minor species : NOx, CO, HC, particulates, are characterised by the fact that in certain conditions they can be quasi avoided. The art of the engineer consists in finding the best compromise to minimise these emissions, some, like NOx and CO, necessitating contradictory conditions. Their study requires a great knowledge in advanced chemical kinetics, particularly for soots : precursors, nucleation, growth and oxidation. The characteristic times are of the order of the millisecond. Major species : CO2, H2O, have a production strictly proportional to the fuel consumption and cannot be avoided. They concern mainly the greenhouse effect. The only way to reduce them is to reduce the fuel consumption and the solution relies on overall engine, and aircraft, efficiencies. The effect of these emissions on the environment involve very complex phenomena belonging to the physical chemistry of the atmosphere. Characteristic times are much longer, from one second to several days. The evolution of the effluents are not deterministic and depend of the local and instantaneous meteorological conditions, and particularly the eventual presence of the solar radiation. These phenomena include heterogeneous mechanisms due to the presence of condensed phases that constitute aerosols presenting important evolution in composition during their lifetime. The two characteristic situations are the local impact, in the vicinity of airports, and the global impact during the flight, the consequences being different for troposphere and stratosphere. In all these problems, sophisticated diagnostics have the greatest importance.

(Source: ACARE Domain 314)

SUBDOMAINS:

1. chemical kinetics
2. turbulent combustion
3. atmosphere physico-chemistry
4. diagnostics
5. species transport and dispersion