1D MODELLING OF ENGINE CRANKSHAFT: IMPACT OF IGNITION TIMING ON CRANKSHAFT TORSIONAL VIBRATIONS

摘要

Internal combustion engines by nature do not generate a constant torque. The torque varies within an engine cycle as a consequence of the non-uniform combustion and inertia forces, leading to a varying engine rotational speed, named torsional vibrations. Torsional vibration can negatively impact the engine performance, and potentially leading to fatigue failure of the crankshaft, or to important NVH problems. The demand for more fuel efficient powertrains and reduction of CO_2 emissions has been leading to a general engine downsizing trend. Technologies like charged direct injection combined with advanced ECU strategies allow reducing the number of cylinders without compromising vehicle performance. However all these technologies result in significantly increased engine torsional excitations from the firing order, making the driveline NVH integration more challenging. A thorough understanding of the impact of the engine control parameters on the NVH performance represents an important step in the engine development phase. This paper presents an example of how different ECU (Engine Control Unit) parameters influence crankshaft torsional vibrations by means of 1D simulation. Different ignition timing settings have been simulated. Finally the simulated torsional vibration results have been compared with experimental data acquired on a Ford 1.6L Ecoboost engine. The good correlation between the simulation and measured data proves the reliability of 1D modelling for this application case, and highlights the importance of combine simulation models and advanced testing methodologies during the engine development phase.