Aspects of 0D and 3D Modeling of Soot Formation for Diesel Engines

Abstract

In this work, zero-dimensional (0D) and three-dimensional (3D) models were applied to the same engine experiment, investigating aspects of 0D and 3D modeling of combustion and soot formation for diesel engines. The 0D simulations were carried out using a direct injection stochastic reactor model (DI-SRM), which is built on a probability density function (PDF) approach. The 0D model allows for the use of detailed chemistry for calculation of combustion, emission formation, and interaction between chemistry and turbulent flow. The 3D computational fluid dynamics (CFD) simulations were performed using a PDF-time scale combustion model and a flamelet library soot source term model. The DI-SRM results demonstrate the applicability of the flamelet model for the combustion process and also elucidate the limitations of the interactive flamelet model when calculating emission formation. The emission results, if plotted in mixture fraction space, show a dispersion for species such as NO and CO, but a flamelet structure for species such as C2H2 and OH, which makes the latter ones applicable for calculation of the source terms of soot formation in mixture fraction space. The CFD calculations were used to verify assumptions made in the DI-SRM and the DI-SRM results were used to verify the assumptions inferred by using tabulated chemistry. It is demonstrated that the DI-SRM can be used for soot modeling under diesel engine conditions and that the flamelet library approach for modeling of soot formation in CFD is sound.