Potential of the Miller cycle on a HSDI diesel automotive engine

The paper explores, by means of CFD simulations, the potential of the Miller cycle, applied to High Speed Direct Injection (HSDI) Diesel engines, facing the challenge of emissions reduction enforced by the near-term regulations, with particular reference to Euro VI. In fact, a valuable benefit of the Miller technique is the strong reduction of combustion temperature, thus the abating of NOx emissions, compared to a traditional cycle with the same values of AFR and EGR rate. actical application of the Miller cycle yields a number of critical issues, which are generally addressed in the paper. However, the goal of the study is to assess the potential and the limits of this technique, more than develop a specific engine configuration. e analysis, a 2.8 L 4-cylinder turbocharged engine produced by VM Motori was selected, carrying out a comprehensive experimental campaign, at both full and partial load. The experimental data allowed the authors to calibrate two types of numerical models, one for the whole engine analyses (0/1D), the other for the combustion process simulation (CFD-3D). The integrated use of these computational tools provides a reliable comparison between the base engine and the one modified according to the Miller cycle, in terms of both emissions and fuel consumption in the European Driving Cycle. It was found a reduction of NOx and Soot of 25% and 60%, respectively, and a worsening of fuel efficiency of 2%. The abating of NOx can be further enhanced, since it is demonstrated that the engine operated according to the Miller cycle can tolerate higher rates of EGR.