Article,

Large Eddy Simulation of Diesel Engine In-cylinder Flow

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Flow, Turbul. Combust., 88 (1): 233--253 (Mar 1, 2012)
DOI: 10.1007/s10494-011-9376-6

Abstract

The numerical simulation of the in-cylinder flow of a realistic Diesel engine is presented. Over the past three decades most of the CFD research for internal combustion engines (ICE) has been carried out using the Reynolds Averaged Navier Stokes (RANS) approach. Despite the achievements obtained in engine design, numerical investigations with RANS models can only give insight into the mean behaviour of the in-cylinder flow. By contrast, Large--Eddy Simulation (LES) allows a better description of the in-cylinder flow motion and gives access to the cycle-to-cycle variations. Multi-cycle simulations of a motored case using LES and a hybrid LES/RANS approach are compared against experimental data and results obtained with a RANS methodology. The cycle-to-cycle variations in global in-cylinder characteristics such as pressure, swirl number and tumble number are reported and an analysis of the in-cylinder flow for each stroke of the engine cycle is presented. The interaction between spray and turbulence is also analysed with closed-chamber simulations. The effects of the hybrid RANS/LES approach on mixing of the vapour phase of the fuel is described and compared to the results obtained with a standard RANS approach. This work gives an insight into the numerical simulation of Diesel engine and illustrates some of the advantages of the LES methodology over RANS. The trade-off between computational cost and details in the flow description using a hybrid RANS/LES approach is discussed.

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