Measurement Of Dynamic Performance Of Large Tilting Pad Journal Bearing And Rotor Stability Improvement

Abstract

Capacities at today’s modern ethylene and refinery plants have steadily increased, giving rise to a growing demand for larger compressors and more powerful drivers all of which require larger rotating parts. In keeping with this trend, it is critically important to optimize the design of rotors, impellers and journal bearings for improved rotor dynamics and high performance fluid dynamics. Rotor stability itself can be greatly influenced by maintaining schroter bearing spans through careful impeller design and the proper selection of journal bearings, such as load-on-pad (LOP) or load-between-pad (LBP) types, and determining the correct number of pads. In order to achieve a robust compressor design, case studies can be important tools in understanding the actual behavior and dynamic characteristics of large journal bearings. In this paper, the authors will present the results of a unique test to measure and compare the oil film profile, pressure and temperature along the bearing pad surface as well as the pad movement vibration for several types of journal bearings under rotating conditions. The dynamic data are compared with 3D finite element analysis/computational fluid dynamics (FEA/CFD) results for each type of journal bearing including rotor response comparison with experiment and analysis. The design and performance of improved impellers to create high shaft rigidity and shorter bearing spans are also discussed. Finally,the authors will present their findings on optimum designs for large journal bearings and make recommendations on how to model journal bearings by separating each pad in the vibration system.