Torsional vibration is an inherent characteristic of marine diesel generator sets . When the initial interference torque is applied to the shafting, the shafting will produce a periodically changing torsional elastic deformation motion, that is, torsional vibration. If there is no damping in the shaft system at this time, this torsional vibration will continue to be repeated, which is called undamped free vibration. Appears as the natural frequency of various modes.
When the unit is running, the shaft system is stimulated by the gas force of the diesel engine cylinder and the reciprocating inertia force of the piston link mechanism. When the frequency of some simple harmonic components in the excitation torque is equal to or close to the natural frequency of the shaft system torsional vibration, the shaft system torsional vibration The amplitude will increase sharply, and the torsional vibration stress will also increase significantly. This phenomenon is called the shaft torsional vibration resonance. Severe primary harmonic torsional resonance can cause serious damage to the shaft system or even break the shaft.
Shaft torsional vibration mode is the most intuitive manifestation of the torsional vibration of the diesel generator set shaft system. The shaft section where the node appears, especially the position where the relative moment of inertia point at the two ends of the shaft section is relatively large, and the mode is self-oscillating. Frequency has the greatest impact. If the calculation result of the torsional vibration of the shafting system does not meet the design requirements during the design, you can improve the relevant parts of the shafting system by analyzing the number of modes of each node, and change the natural frequency of the shafting system to make it the main Harmony avoids the working speed zone to ensure the safe and reliable operation of the shafting.