Generalised analysis of compensating balancing sleeves with experimental results from a scaled industrial turbine coupling shaft

Knowles, Grahame and Kirk, Antony and Bingham, Chris and Bickerton, Ron (2017) Generalised analysis of compensating balancing sleeves with experimental results from a scaled industrial turbine coupling shaft. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science . ISSN 0954-4062

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Abstract

The paper furthers the analysis of a recently proposed balancing methodology for high-speed,
flexible shafts. This mechanism imparts corrective balancing moments, having the effect of
simulating the fixing moments of equivalent double or single encastre mounted shafts. This
is shown to theoretically eliminate/nullify the 1st lateral critical speed (LCS), and thereby
facilitate safe operation with reduced LCS margins. The paper extends previously reported
research to encompass a more generalised case of multiple, concentrated, residual
imbalances, thereby facilitating analysis of any imbalance distribution along the shaft.
Solutions provide greater insight of the behaviour of the balancing sleeve concept, and the
beneficial implications for engineering design. Specifically: 1) a series of concentrated
imbalances can be regarded as an equivalent level of uniform eccentricity, and balance sleeve
compensation is equally applicable to a generalised unbalanced distribution, 2) compensation
depends on the sum of the applied balancing sleeve moments and can therefore be achieved
using a single balancing sleeve (thereby simulating a single encastre shaft), 3) compensation
of the 2nd critical speed, and to a lesser extent higher orders, is possible by use of two
balancing sleeves, positioned at shaft ends, 4) the concept facilitates on-site commissioning
of trim balance which requires a means of adjustment at only one end of the shaft, 5) the
Reaction Ratio, RR, (simply supported/ encastre), is independent of residual eccentricity, so
that the implied benefits resulting from the ratio (possible reductions in the equivalent level
of eccentricity) are additional to any balancing procedures undertaken prior to encastre
simulation. Analysis shows that equivalent reductions in the order of 1/25th, are possible.
Experimental measurements from a scaled model of a typical drive coupling employed on an
industrial gas turbine package, loaded asymmetrically with a concentrated point of
imbalance, are used to support the analysis and conclusions.

Keywords:High-speed shafts, lateral vibrations, balancing sleeve, critical speed, mechanical design
Subjects:H Engineering > H321 Turbine Technology
Divisions:College of Science > School of Engineering
ID Code:28882
Deposited On:26 Sep 2017 10:44

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