| dc.description.abstract | The influence coefficient (IC) method is typically used in balancing, especially on-site. For a two-bearing machine, there are basically two approaches to apply this method. The first one is to treat it as a multiplane balance problem involving a 2x2 matrix of complex ICs. In this approach, two direct ICs along with two cross-effect ICs are generated so that correction weights at one or two balance planes can be determined. The second one is to apply a static pare (in-phase) and/or couple pair (180 degrees out-of-phase) weights to reduce the vibration. The latter approach has been used extensively in the field, especially on steam turbine and generator rotors. Dependent on vibration mode shapes and combinations as well as balance plane accessibility, sometimes applying static or couple pair weights can be a wise choice; other times weights at one or two end planes are needed. There are totally 4 possible sets of IC data due to weights at plane 1, plane 2, static pair, and couple pair. Influence coefficient data would typically be obtained by applying trial weights followed by trial weight runs. It is found, however, that these IC data can be converted easily without trial weight runs once any two of 4 sets are known. The above findings and conversion equations have been obtained analytically and verified by experimental results. This paper presents all available IC conversion equations together for the first time. Experimental verification is also provided by a rotor kit to demonstrate their accuracy. Four real cases are presented to demonstrate their applications. The first case is to show the necessity of applying a couple pair weight by obtaining its IC converted from plane 1 and plane 2 ICs. The second case is to show a one-trial weight run method on symmetric Copyright© 2021 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station rotor. The third case is to show the necessity of applying individual weights each at plane 1 and plane 2 by obtaining their ICs converted from static and couple pair ICs. And the fourth case is to apply individual weights each at plane 1 and plane 2 after having one trial weight run only, with previously known static pair IC data. | |
