SOOT FORMATION IN LAMINAR DIFFUSION FLAMES

Soot and temperature measurements were performed in sooting and non-sooting laminar diffusion flames of ethylene, ethane, n-hexane and n-hexadecane in still air. Laser light scattering and extinction was used to determine soot volume fractions and number densities. Temperatures were measured with thermocouples. Maps of soot volume fraction f(V), number density N(S), mean particle diameter D(S) and soot surface area A(S) are derived. These distributions are compared for smaller and larger fuel molecules, and for different flow rates. For the liquid fuel n-hexane the soot field is compared with spatially resolved chemical species measurements. The ethylene and ethane data are combined with modelled flame field velocities and particle trajectories to obtain local soot formation rates. The correlation of surface specific mass growth rates with local temperature and stoichiometry (calculated as mixture fraction) is discussed.