COUPLED RADIATION AND SOOT KINETICS CALCULATIONS IN LAMINAR ACETYLENEAIR DIFFUSION FLAMES

Radiation heat transfer from flames depends on the instantaneous soot volume fractions and temperatures. A coupled radiation and soot kineti cs calculation in laminar acctylene/air and acetylene-methane/air diff usion flames is described. Transport equations for mass, momentum, gas -phase mixture traction, enthalpy (sensible + chemical), soot mass fra ction, and soot number density are solved. A simplified soot kinetics model incorporating nucleation, growth, oxidation, and agglomeration p rocesses is used. The reaction rates in the simplified kinetics model depend on the temperature and the local concentrations of acetylene an d oxygen. The major gas species concentrations are obtained from state relationships. The local temperature is obtained by solving the energ y equation, taking radiation loss and gain and the energy exchanges as sociated with soot formation and oxidation into consideration. The rad iative source/sink term in the energy equation is obtained using a mul tiray method. Since these flames radiate a substantial part of their e nergy, the kinetic rates associated with soot processes are strongly c oupled to the energy equation. This strong coupling between radiation, and soot formation and oxidation processes is modeled for the first t ime. The results of the soot kinetics model are compared with measurem ents of soot volume fractions obtained using laser tomography. The agr eement between measurements and predictions of soot volume fractions s upports the present method, The predicted temperature profiles support the structure of strongly radiating flames discovered earlier.