Fluid Film Bearings
Fluid film bearings are commonly used in heavy rotating machines because they possess not only high load carrying capacity but also inherent damping properties. Unlike rolling element bearings, fluid film bearings are an important machine element which offers, in addition to support stiffness, substantial damping to insure rotordynamic stability. This feature is also retained in the squeeze film damper. The stiffness and damping properties of the fluid film significantly alter the critical speeds and unbalance response of a rotor, lowering its critical speed by up to 25 % in practice. It was shown in the previous chapters that internal damping in the rotor without support(external) damping easily causes rotordynamic instability. However, some types of fluid film bearings, as well as seals, are characterized by cross-coupled, as well as direct, stiffness and damping, leading to complicated system behavior and, sometimes, system instability. This type of rotor instability due to a bearing fluid film effect is known as a self-excited vibration.
KeywordsVibration Analysis Critical Speed Journal Bearing Fluid Film Eccentricity Ratio
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