Large Eddy Simulation of Scalar Dissipation Rate in an Internal Combustion Engine

A novel algebraic similarity model for subgrid scalar dissipation rate has been developed as part of the Large Eddy Simulation (LES) package KIVA3V-LES for diesel engine study. The model is proposed from an a priori study using Direct Numerical Simulation (DNS) of forced isotropic turbulence. In the a posteriori test, fully resolved turbulent passive scalar field measurements are used to validate the model in actual engine flows. For reason of the length limit by SAE and the specific interest in engine applications, only a prior test and a posteriori test in engine flows are included in this paper. A posteriori tests in isotropic cube flow, turbulent round jet and flame cases will be presented in separate papers.

An engine LES simulation of multi consecutive cycles was performed in this study. In multi-cycle analysis, the LES simulations show the capability of capturing cycle-to-cycle variations in addition to correctly estimating the ensemble averaged scalar dissipation rate in the sampling domain. The averaged magnitude of resolved scalar dissipation rate as well as subgrid scalar dissipation rate is quantified for the experiments and LES simulation. The accurate prediction of the mixing at resolved level, in combination with reasonable scaling relation between the resolved dissipation and residual dissipation, contributes to the satisfactory prediction of the model.