A theoretical investigation on experimental model of torsional vibration for turboset shafting

This paper deduces the relationships between the natural frequency f of torsional vibration and the geometry dimension both for a simple ideal model and a real turboset shafting at first. It is found that the frequency of torsional vibration for the shafts with same shape is inversely-proportional to their length but is independency with their diameter, and the mode of torsional vibration is the same for the shafts with same shape. In addition, the distribution of the maximum torque and the maximum shearing stress along the shaft is the same for the shafts with same shape. Then, this paper studies the sensitivity of torsional natural frequencies and modes to the steam turboset shafting's rotary inertia and stiffness based on physical data of torsional simulation experimental rig. It is showed that mechanical parameters, either rotary inertia or stiffness, may influence shafting's torsional vibrations greatly in a certain case.