The impact of the infinite liquid diffusivity and the diffusion limit droplet heating model on the evaporation and combustion characteristics in a diesel spray

The impact of two models representing two limiting cases of the droplet heat-up process, namely the infinite diffusivity (ID) and the diffusion limit (DL) model, on the evaporation, self-ignition and subsequent combustion in a diesel spray is investigated. The simulation results show that, as compared with the DL model, the ID model leads to an over-prediction of the length of the ignition delay period by about 20 %. This is attributed mainly to the under-prediction of the evaporated mass predicted in the case of the ID model, during the early stages after injection. Accordingly, the time evolution of the combustion processes in the case of the ID model is found to lag that predicted when the DL model is employed, by roughly 0.3 ms.