Rotor-Bearing Dynamics of Integrally Geared Turbomachinery
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This tutorial focuses on the rotordynamic characteristics of integrally geared compressors and expanders. Although the focus is for turbomachinery the topics discussed also apply to industrial gearing. The topics covered include understanding the influence of gear forces, thrust collars (hydrodynamic elements that transmit load from pinion shaft to bull gear shaft), and thrust bearings on the reaction loads of the pinion and bull gear bearings. The various aspects that couple the pinion and bull gear dynamics such as: 1) gear contact stiffness and 2) thrust collar moment stiffness are examined to show the influence of coupled pinion-bull gear rotordynamics. Torsional, lateral, and axial rotordynamic behavior of geared systems is discussed relative to different design standards: API617, API672, etc. Various case studies are presented that show the vibration characteristics for common field and shop problems. The case studies used to illustrate the topics presented show the origin of “step increases in vibration,” “sub-synchronous vibration originating from aerodynamic excitation and bull gear harmonics on the pinion shafting.
Wygant, Karl; Robertson, Chad; Li, Fang (2018). Rotor-Bearing Dynamics of Integrally Geared Turbomachinery. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station. Available electronically from