One-dimensional simulation methods for unsteady (transient) engine operations have been developed and published in previous studies. These 1-D methods utilize heat release and emissions results obtained from 3-D CFD simulations which are stored in a data library. The goal of this study is to improve the 1-D methodology by optimizing the control strategies. Also, additional independent parameters are introduced to extend the 3-D data library, while, as in the previous studies, the number of interpolation points for each parameter remains small.
The data points for the 3-D simulations are selected in the vicinity of the expected trajectories obtained from the independent parameter changes, as predicted by the transient 1-D simulations. By this approach, the number of time-consuming 3-D simulations is limited to a reasonable amount. Boost pressure, EGR and relative A/F limit control procedures are compared to improve the engine response to speed/load requirements at minimized emission levels.
The influence of transient operations on the behavior of the prescribed EGR flow rates is demonstrated. The examples are calculated for a medium speed diesel engine but the method is seamlessly transferable to road vehicle engines. Since this method reduces the simulation time, it is possible to predict emissions during standardized unsteady tests in real time. Therefore, this 1-D simulation method is a useful tool for engine optimization and control, that is, it allows the minimization of the fuel consumption while meeting legislated emission standards.