Multi-dimensional quasi-discrete model for the investigation of heating and evaporation of Diesel fuel droplets

Previously developed droplet heating and evaporation models, taking into account temperature gradient, recirculation, and species diffusion within droplets, and their application to the analysis of commercial automotive fuel droplets are reviewed. It is shown that the most efficient analysis of Diesel fuel droplet heating and evaporation is based on the MDQD (multi-dimensional quasi-discrete) model, taking into account the contribution of all groups of hydrocarbons in automotive fuels. The main features of this model are summarised and its new application to the analysis of droplets in Diesel engine-like conditions, taking into account time-dependent velocities, is described. In the MDQD model,Diesel fuel is approximated by six groups of components: alkanes, cycloalkanes, bicycloalkanes, alkylbenzenes, indanes & tetralines, naphthalenes, and three characteristic components C19H34 (tricycloalkane), C13H12 (diaromatic), and C14H10 (phenanthrene). It is shown that errors in estimated temperatures and evaporation times in typical Diesel engine conditions, using the approximation of Diesel fuel by 15 quasi-components/components compared to the case when all 98 components are taken into account, are up to 1% and 3%, respectively. This is acceptable in most engineering applications. This approximation has also reduced CPU time by about 6 times compared with the casewhen the contribution of 98 components is taken into account. The approximations of Diesel fuel with n-dodecane (widely used in engineering modelling) and 20 alkane components lead to under-prediction of the evaporation time by over 50% and 22%, respectively.