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This paper discusses the influence of rolling element and fluid film bearings on rotor dynamics of “high-speed” turbo-machinery. System critical speeds, rotor response to unbalance, instability, and turbulence are discussed. The types of fluid film bearings best suited for high-speed operation are identified. Examples of high-speed turbomachinery using rolling element, liquid film and gas bearings are presented.

The need for balancing a high-speed rotor in a manner that accounts for its speed-dependent deformations is discussed. The influence coefficient method of flexible rotor balancing is described with reference to the balancing of an advanced gas turbine engine rotor. This engine rotor-bearing system is then studied in detail as an application of flexible rotor balancing, using the influence coefficient method. The relative effectiveness of various combinations of balance speeds and numbers of balance planes is compared.