A Simple Procedure for Assessing Rotor Stability

Paper No. 55

A Simple Procedure for Assessing Rotor Stability K. E. Atkins/R. X. Perez/D. M. Turner, Third International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, April 1990.

This paper describes a procedure for assessing rotor stability using perturbation tests in an at-speed balancing machine. The equipment required to perform the tests is readily available and could be used at most at-speed balancing facilities. Additional time required over and above normal balancing time is minimal. Results of using this procedure for evaluating a five stage, 2800 hp hydrogen recycle compressor are presented. Comparisons of calculated and measured stability characteristics are made using the concept of “mechanical logarithmic decrement” (dm). Three different bearing configurations were tested. The test data clearly showed the sensitivity of rotor stability (system damping) to rotor speed as well as bearing design parameters. The measured results were used to optimize bearing parameters (clearance and preload) to improve rotor stability.

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