文档介绍：Source: Torsional Vibration of Turbomachinery
Chapter
1
Introduction
Torsional Vibration
Torsional vibration involves angular oscillations of the rotors of a
machine. For large rotating machinery the mechanical system often
consists of several rotors that are connected by relatively slender shafts
and couplings. For example, Fig. is a photograph of the generator
rotor of a large steam turbine-generator. It has a large-diameter body
section and relatively flexible shaft extensions.
Each rotor in the system will oscillate following a torsional distur-
bance to the machine about its rotational axis, resulting in twisting in
the shafts and to a lesser extent in the large-diameter rotor bodies
themselves. For some machines involving geared rotor connections, for
example, there may be several rotor axes of rotation. The twisting
oscillations following severe torsional disturbances to a machine may
be sufficient to cause fatigue damage to the machine’s shafts and other
In the design of rotating machinery, torsional vibration analysis is
vital for ensuring reliable machine operation due to machine stimuli
that range from rarely occurring, high-level transients to continuous,
relatively low levels of excitation.
If shaft and ponent failures occur on these large
machines as a result of shaft torsional oscillations, the consequences
can be catastrophic. In the worst case, an entire machine can be
wrecked as a result of the large unbalancing forces that can arise fol-
lowing shaft separation and turbine blade failures, and this has actu-
ally occurred. There is also potential for loss of human life. For these
reasons great attention is generally taken at the design stage to
ensure that high-speed rotating machines have the required torsional
capability.
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