A large two-stroke Diesel engine (1) in a ship has a main shaft consisting of a crankshaft and the propeller shaft, and of intermediate shafts, if any. The opening and closing movements of the exhaust valves (12) and the fuel injection into the cylinders are controlled by means of a computer (16). During an interval of revolutions about a resonance point for torsional vibrations in the main shaft the engine is controlled so that the exhaust valve (12) of at least one of the cylinders is set open during the compression stroke of the cylinder, and that the power of at least one of the remaining cylinders is increased corresponding to the lack of power from the cylinder or the cylinders without compression. The contribution (K) of the compression pressure to the vibration order which excitates the torsional vibrations is thus removed so that the torsional stresses in the main shaft are diminished.
展开▼
