Abrupt decrease in vibration on runup
Abrupt decrease in vibration on runup
(OP)
On a high speed, well balanced rotor, when running up in speed, there is a speed where vibrations start to increase significantly. At this point, increasing the power does not increase rpm very much, but does increase vibration. After considerable increase in power and subsequent slight increase in speed, the vibration in the system suddenly drops to a level about the level before the vibration increase started. There are several resonances involved within the speed range with the increase of vibration. During the high vibration band, and only during that band, a sub-order resonance that can be explained is apparent, but also a second sub-order resonance that is not explained appears. The rotor is supported by two ball bearings, one is rigid, and one is floating in all directions. An axial mode is probably at play here as well as possible excitation of a structure resonance excited by bearing cage frequency. I have seen data similar to this before, and I do not expect simple unbalance to be the full explanation here. Is this a well known phenomena? What Google search terms would lead to info on this?
Thanks.JH
Thanks.JH





RE: Abrupt decrease in vibration on runup
- Steve
RE: Abrupt decrease in vibration on runup
RE: Abrupt decrease in vibration on runup
While near the critical speed, the assembly is flexing, possibly a lot, and dissipating extra energy, some as vibration, by doing so.
Do not attempt to force it into operation in that critical speed range; it clearly doesn't like doing so.
Read up on 'critical speed'.
Mike Halloran
Pembroke Pines, FL, USA
RE: Abrupt decrease in vibration on runup
http://ww
Here is a good article on it.
Spud says; Meticulous effort and willingness to learn are honorable traits.
RE: Abrupt decrease in vibration on runup
http://centrifugalpump.org/bulletinboard_02.html
Spud says; Meticulous effort and willingness to learn are honorable traits.
RE: Abrupt decrease in vibration on runup
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(2B)+(2B)' ?
RE: Abrupt decrease in vibration on runup
RE: Abrupt decrease in vibration on runup
Cheers
Greg Locock
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RE: Abrupt decrease in vibration on runup
The test of this hypothesis would be to see what happens in a run down...
M
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Dr Michael F Platten
RE: Abrupt decrease in vibration on runup