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Combustion and pollutant formation in a new recently introduced Common-Rail DI Diesel engine concept with roof-shaped combustion chamber and tumble charge motion are numerically investigated using the Representative Interactive Flamelet concept (RIF). A reference case with a cup shaped piston bowl for full load operating conditions is considered in detail. In addition to the reference case, three more cases are investigated with a variation of start of injection (SOI). A surrogate fuel consisting of n-decane (70% liquid volume fraction) and α-methylnaphthalene (30% liquid volume fraction) is used in the simulation. The underlying complete reaction mechanism comprises 506 elementary reactions and 118 chemical species. Special emphasis is put on pollutant formation, in particular on the formation of NOx, where a new technique based on a three-dimensional transport equation within the flamelet framework is applied.

Quenching of premixed flames at cold walls is investigated to study the importance of the model fuel choice for combustion modeling. Detailed chemical mechanisms for two different fuels, namely the low-molecular-weight fuel methane, and the more complex fuel iso-octane are employed. For both fuels the response of the flame to the very rapid heat loss at the cold wall is studied. The most important and significant difference between methane and iso-octane for this problem is the postquench oxidation of unburned hydrocarbons. Methane shows fast oxidation of unburned fuel and intermediate hydrocarbons whereas postquench oxidation for iso-octane is slow especially for the intermediate hydrocarbons. Furthermore, the Soret effect which is usually considered to be of minor importance appears to be important in modeling the rate limiting diffusion process. This is caused by different directions of the thermal diffusive transport for certain species.

Combustion and pollutant formation in a DI-Diesel engine are numerically investigated using the Eulerian Particle Flamelet Model (EPFM). A baseline case for part load operating conditions is considered as well as an EGR variation. The surrogate fuel consisting of n-decane (70% liquid volume fraction) and α-methylnaphthalene (30% liquid volume fraction) is used in the simulation. Results are compared to experimental data that has been obtained using real diesel fuel. The effect of multiple flamelets on the simulation of the auto-ignition process and the pollutant formation is discussed and a converging behavior of the model with respect to the number of flamelets is found. The effect of homogenization of the three-dimensional mixture field is investigated and it has been included in the formulation of the scalar dissipation rate.