A further evaluation of the mixing controlled direct chemistry (MCDC) combustion model for diesel engine combustion using large eddy simulation

作者：Zhang Yuxin^*; Rutland Christopher J

来源：Fuel, 2013, 105: 272-282.

DOI：10.1016/j.fuel.2012.09.050

• Diesel engine modeling
• Scalar dissipation rate
• Large eddy simulation
• Kinetic time scale
• Mixing time scale

The local mixing effect at sub-grid scale (SGS) is explored using Large Eddy Simulation (LES) turbulence model with a mixing controlled direct chemistry (MCDC) model. The MCDC model is developed using the computation of chemical kinetics, thermo-chemical equilibrium state and SGS mixing effects by combining a mixing time scale and a kinetic time scale with the integration of direct chemistry solver (DCS) solutions. The mixing time scale is based on the SGS scalar variance and SGS scalar dissipation rate. The kinetic time scale is based on thermal-chemical equilibrium state and the kinetic reaction rate. These two time scales have been previously evaluated in experiments and computations, showed reasonable quantifications of local mixing and kinetic progress, which improved accuracy of combustion modeling.
In this study, the conventional diffusion-type operating conditions are represented by a Caterpillar 3401 T single cylinder oil test engine (SCOTE). The cylinder-averaged results are compared between the DCS model, MCDC model and 'Kong-Reitz' model. A grid dependence study for the MCDC model on a baseline grid and a coarse grid is performed. The mixing time scale and kinetic time scale analysis for the MCDC model and 'Kong-Reitz' model is provided to investigate the differences in predictions. Compared to the DCS model and 'Kong-Reitz' model, the MCDC model shows improved capability in modeling mixing effects at the SGS level, which is represented by the improved prediction of combustion phasing and good matching with experimental results.

• 出版日期2013-3