The Resolution of Unwanted Vibrations in Rotating Machinery

Abstract

The field of rotating machinery dynamic analysis has evolved over the past 60 years from the calculation of zero damped critical speeds using mechanical calculators to the computation of multi-rotor and multi-bearing damped response and stability analysis with unbelievable speed and accuracy. This capability has also required the advances in the understanding of antifriction and hydrodynamic bearings as well as both liquid and gas seals. The understanding and calculation of the aerodynamic forces from axial flow and radial flow compressors and turbines is still less than perfect and requires the application of special equations developed from practical experience. It seems then that practical experience is in fact the key to understanding the internal forces that influence the radial vibrations of the rotor shaft. That being said, it could be argued that the resolution of unwanted vibrations might require practical experience to be successful. This line of reasoning has prompted the author to document the practical experience that has allowed some very difficult machinery problems to be resolved with a combination of analytical tools, prior experience, and a dash of in-depth reasoning. The analytical tools can be purchased, the experience can be gained in a life time, but the gift of in-depth reasoning is priceless. Solving a problem that has a known cause and remedy is rewarding but when a problem from an unknown cause can be finally solved, that is the most rewarding of all. This paper will document the process of solving some very interesting problems that have occurred in the last 40+ years.