Model-based torsional vibration control of internal combustion engines

For internal combustion engines, it is important to ensure uniform cylinder-wise torque contributions in order to avoid excessive crankshaft torsional vibrations. Especially, the high-torsional vibration levels of medium-speed power plants and marine engines cause unnecessary wear of mechanical components, such as the flexible coupling between the engine and the load. This is because of the fact that the lower torque-order frequencies excited by the fuel combustions are usually in the vicinity of the natural frequency of the flexible coupling. A cylinder-balancing method is presented, which minimises crankshaft torsional vibrations on medium-speed internal combustion engines. Using a model of engine dynamics, the reduction of crankshaft torsional vibrations can be addressed as an online optimisation problem, where the Newton direction of fuel-injection adjustments is determined at each step. The proposed method is tested on a six-cylinder 6 MW Wartsila power plant engine, showing that the torsional vibration level can be significantly reduced, well below admissible levels.