Effect of mesh refinement and model parameters on LES simulation of diesel sprays

Abstract

Review of the recent literature on fuel spray modeling suggests that the use of Large Eddy Simulation (LES) approach is of fundamental importance in order to adequately represent the complex phenomena related to spray–turbulence interactions, which affect all physical processes of the mixture formation and combustion. However, some deficiencies have been identified related to the accuracy of non-reacting spray simulations, mainly related to the adequate set-up of different models and numerical parameters and, in particular, to mesh size, to adequately capture the spray turbulence interactions. This work presents the application of advanced turbulence modeling to the spray injection process in a static chamber, based on the implementation of a LES turbulence model in a Lagrangian spray based solver in OpenFOAM (open source code). Results obtained hitherto for non-reacting sprays proved that highly accurate results can be obtained for liquid and vapor length penetrations by correct modeling of spray phenomena and adequate mesh refinement to correctly capture turbulence–spray interactions. In addition, a new criterion for adaptive mesh refinement based on the droplet Stokes number, is proposed and tested. This criterion can be also used to evaluate to what extent the spray turbulent dispersion, is adequately captured with a given mesh refinement, using LES approach.