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 arereviewed. It is shown that the most efficient analysis of Diesel fuel droplet heating and evaporation is based on theMDQD (multi-dimensional quasi-discrete) model, taking into account the contribution of all groups of hydrocarbons inautomotive fuels. The main features of this model are summarised and its new application to the analysis of dropletsin 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 Dieselengine conditions, using the approximation of Diesel fuel by 15 quasi-components/components compared to the casewhen all 98 components are taken into account, are up to 1% and 3%, respectively. This is acceptable in mostengineering 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 byover 50% and 22%, respectively.