Application Of A Heat Barrier Sleeve To Prevent Synchronous Rotor Instability.
Abstract
This paper explains how synchronous rotor instability can occur
in high speed turbomachinery due to differential heating of bearing
journals. Theoretical investigations have indicated that rotors
supported by fluid-film bearings inherently exhibit a nonuniform
temperature distribution around the bearing journal circumference
(Keogh and Morton, 1993, 1994). This thermal effect results in
rotor bending, which in combination with an overhung mass, such
as couplings and overhung impellers, can significantly increase
rotor unbalance and thus, synchronous rotor vibration. Under
certain conditions, it can even lead to synchronous rotor instability.
In this paper, a case history on synchronous rotor instability is
presented, concerning two pipeline compressors for a natural gas
application. The compressors successfully passed an API 617
mechanical running test in the manufacturer's workshop. However,
installed at site, the rotor behavior of these machines was
completely unstable. The vibration analysis indicated that the
cause of the instability was likely to be thermal in origin. However,
ordinary labyrinth seal rubbing could be excluded. One of the
compressor cartridges was returned to the manufacturer's
workshop for a detailed examination and an extensive test
program. It appeared that rotor instability was caused by
differential heating of the impeller-end bearing journal, which
could not be reduced by modification of the bearing parameters.
Eventually, a heat barrier sleeve was designed to prevent thermal
bending of the rotor at this location. Additional testing confirmed
the expected effect and, after installation in the field, the unstable
behavior of both machines was completely eliminated.
Description
LecturePg. 17-26
Subject
TurbomachinesCollections
Citation
Jongh, Frits M. De; Hoeven, Pieter Van Der (1998). Application Of A Heat Barrier Sleeve To Prevent Synchronous Rotor Instability.. Texas A&M University. Turbomachinery Laboratories. Available electronically from https : / /hdl .handle .net /1969 .1 /163412.