Investigation of Effects of Piston Bowl and Fuel Injector Offsets on Combustion and Emissions in D.I. Diesel Engines

The effects of piston bowl and fuel injector offsets on combustion and emissions in a D.I. diesel engine have been investigated by using a KIVA CFD code. In this investigation, modeling combustion and emissions in the diesel engine at different regimes is performed, including the model of the single spray sector without piston bowl and fuel injector offsets, the model of the full cylinder of 360 degrees without piston bowl and fuel injector offsets, and the model of the full cylinder of 360 degrees with both a piston bowl offset and a fuel injector offset, respectively. In addition, the corresponding experiments are conducted to validate the modeling. The fuel spray patterns are compared for different models. The cylinder pressure, the heat release rate, and the emissions of NOx and soot are examined. From inspection of the calculated results, it is found that the computational results are in good agreement with the experimental data for the cylinder pressure, the heat release rate, and the emissions of NOx and soot. The results from the models of the full cylinder of 360 degrees with/without piston bowl and fuel injector offsets show some difference from those from the model of the single spray sector without piston bowl and fuel injector offsets. But this discrepancy may be accepted for most engineering practices. Therefore, it is concluded that in practical applications, the model of the single spray sector without piston bowl and fuel injector offsets can be used, which will greatly reduce the computation time without causing large errors. Only in some special cases, is it necessary to use the full cylinder of 360 degrees with piston bowl and fuel injector offsets to obtain local details.