Forward Subrotative Speed Resonance Action Of Rotating Machinery
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A wide variety of mechanisms can create net effective forces on those rotor systems which follow the rotor around in its rotation direction. While whatever dampening the rotor system has always exists, it is frequently the nature of these forward acting forces to act effectively opposite to the system damping. Once any one or a combination of these forces matches or exceeds the existing rotor damping the rotor system responds by excitation of resonances which lie below rotative speed. To show this general category of machinery malfunction mechanisms, first the oil whirl and oil whip behaviors are shown in graphical non-mathematical forms. To show that its relationship to oil whip is more than symptom-deep, the next presentation is the internal friction malfunction. Following this, a series of other known energy transformers are shown to exhibit the behavior and relationship of this class of rotor malfunction mechanisms. The relationships between the forward acting mechanisms, the non-directional mechanisms, and reverse mechanisms are discussed, and demonstrations of some of the forward mechanisms are performed. Recent classical cases of some of the destructive mechanisms are presented, and the general category of malfunction is summarized.
Bently, Donald E. (1975). Forward Subrotative Speed Resonance Action Of Rotating Machinery. Texas A&M University. Gas Turbine Laboratories. Available electronically from