The Effects of Multiplane Balancing on Flexible Rotor Whirl Amplitudes

Influence coefficient balancing of an advanced gas turbine rotor in fluid-film bearings with nonsymmetrical properties has been examined. The effect of the number of balancing planes in use of the quality of balance has been studied with particular attention being paid to the reasons why an increase from three planes to four planes gives no apparent improvement. Effects examined include the influence of nonsymmetrical bearing properties, the effect of having a bending critical speed close to either side of the intended operating speed, and the effect of correction weight errors on balance quality. Reasons why the addition of a fifth balancing plane resulted in a significant improvement in balance quality are given.