Applying ILMD technique with time scaling for CFD simulation of diesel engine

Detailed mechanisms describing ignition, flame propagation and pollutant formation typically involve several hundred species and elementary reactions, prohibiting their use in practical three-dimensional engine simulations. Conventionally reduced mechanisms often fail to predict minor radicals and pollutant precursors. The ILDM-method is an automatic reduction of a detailed mechanism, which assumes local equilibrium with respect to the fastest time scales identified by a local eigenvector analysis. In the reactive flow calculation, the species compositions are constrained to these manifolds. Conservation equations are solved for only a small number of reaction progress variables, thereby retaining the accuracy of detailed chemical mechanisms. This gives an effective way of coupling the details of complex chemistry with the time variations due to turbulence. A standard and RNG k-e model is used to model the turbulent flow field. Turbulence-chemistry interactions are taken into account by integrating the chemical source terms over a presumed probability density function (pdf ). The standard KIVA III code along with the above models for chemistry and turbulence were used to simulate the flow in a single cylinder of a DI diesel engine. Since no equilibrium or partial-equilibrium approach is involved, accurate concentrations of O radicals and soot-precursors (C2H2 & C3H3) can be obtained from the ILDM