A kinetic algorithm for modelling the droplet evaporation process in the presence of a heat flux and background gas

Although the droplet evaporation process is essentially a kinetic one (its description requires the analysis of the distribution function of molecules), in practical engineering applications its analysis is almost universally based on the hydrodynamic approximation. Recent papers published by the PI, together with researchers from the Moscow Power Engineering Institute, point out that the latter approximation may lead to noticeable underestimates of the evaporation time of droplets in diesel engines, where the applicability of this approximation has never, to the best of our knowledge, been questioned. This conclusion, however, was made based on the simplistic kinetic model, or the numerical algorithm based on some assumptions, the applicability of which is not at first evident. For example, it was assumed that the contribution of heat flux inside the Knudsen layer can be ignored. The main focus of this work will be on the development of a new model, taking into account both the heat flux in the Knudsen layer and the presence of ambient background gas. It is expected that the temperature at the outer boundary of the Knudsen layer will be found using the condition of matching heat fluxes at the outer boundary of the Knudsen layer. This new model will be applied to the simulation of the evaporation of diesel fuel droplets in the first instance and its wider applicability is anticipated.