Impact of mesh size,time step,turbulence,and species parameters on diesel combustion simulation accuracy: A sector model perspective

Abstract

The combustion processes in diesel engines need to be optimized due to the increasing global energy demand and tightening environmental regulations. Although experimental methods provide valuable information, they have cost, time, and measurement limitations for detailed investigation of complex physical and chemical processes in the cylinder. On the other hand, three-dimensional (3D) computational fluid dynamics (CFD) based reactive flow simulations allow detailed and economic analysis of in-cylinder processes. However, the accuracy of these simulations is directly dependent on preprocessing parameters such as mesh size, time step, turbulence model, and number of chemical species. In this study, the effects of these parameters are investigated using a sector modeling approach to balance the computational cost with the numerical simulation accuracy. The 44407-element mesh reached the experimental value with only 0.27% difference at maximum cylinder pressure; the difference for the coarse mesh increased to 2.6%. The standard 5.0 × 10⁻⁰⁶ s time step was found to be optimum with an error of 0.27% in pressure estimation. The RNG k−ε turbulence model provided 10% better results in pressure and emissions compared to the standard k−ε. The chemical model, which contains 191 species, gave results very close to the experimental data, especially for the emission. These findings reveal the importance of pretreatment parameters for high accuracy in diesel engine CFD analyses.