Modelling the Effect of Split Injections in Diesel Engines Using Representative Interactive Flamelets

A major problem in reducing pollutant emissions from diesel engines is the soot-NO_x trade-off. With the introduction of the Common-Rail injection system splitting the injection into separate pulses has become possible. Experiments using multiple injections indicated that there is the chance to shift the soot-NO_x curve closer to the origin.

In order to understand the underlying physical process multidimensional simulations have been carried out for a baseline as well as a split injection case using the Representative Interactive Flamelet (RIF)-Model. The computations are compared to experimental data showing good agreement for both cases. The computations as well as the experiments confirm the possibility of reducing soot with only a slight increase in NO_x emissions. It is shown that soot is reduced due to a different mixing process resulting in fewer rich regions.