Abstract
As compared with the conventional diesel combustion, Premixed Compression Ignition (PCI) combustion has an opportunity to achieve low fuel consumption and clean exhaust gas simultaneously. However, to improve the stability of fuel consumption, exhaust gas, and combustion noise, it is necessary to control ignition timing appropriately in PCI combustion. We therefore conducted a study to develop a new prediction model to control ignition timing. In this model, an empirical equation of Arrhenius expression including some sub-models and Livengood-Wu integral were applied to consider the in-cylinder condition of a mixture formed by fuel injection. The model constants were determined based on the experimental results obtained by Design of Experiments (DOE) so that sufficient prediction accuracy could be achieved for transient operating condition. By using a mass-produced Engine Control Unit (ECU) employing feed-forward control logic based on this model, we confirmed that the ignition timing in the transient operating mode could be controlled rather well by reflecting a predicted ignition delay period to fuel injection timing. With the controllability of ignition timing, the robustness of engine performances in terms of fuel consumption, exhaust gas and combustion noise could be improved with PCI combustion.
