Dynamic balancing of rotors supported on fluid film bearings using finite element analysis

Ahuja, Sunil (1984) Dynamic balancing of rotors supported on fluid film bearings using finite element analysis. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis presents a comprehensive analysis of a multi-rotor bearing system, that includes realistic end support conditions. It provides a design engineer with the present day technology available in carrying out a balancing analysis. The design is based on minimizing the flexural response, due to mass unbalance. -- The model is developed based on the finite element approach which provides a convenient and accurate means of balancing a rotor-bearing system. The model incorporates the effects of translational, and rotational inertia, and gyroscopic moments, using the consistent matrix approach in conjunction with dynamic matrix reduction technique, modal analysis, and least-square balancing technique. The use of matrix reduction technique for determining a equivalent reduced system, provides subsequent saving of both computational time and space on the digital computer. This allows modelling of complex rotor system conveniently, while retaining only those degree of freedom essential to the solution of the problem. The modal analysis used is an effective means of determining the unbalance force response, for systems with unsymmetric stiffness and damping matrices. The least-square method for balancing, is used to include balancing cases where the number of measuring lanes exceeds the number of balancing planes. This represents most actual balancing situations, and allows an increase in the input data, whereby the consequence of a single error in data tends to decrease. The balancing at one speed is usually sufficient to bring the rotor amplitude down over its entire speed range. Further, flexibility in rotor balancing is provided by including the effect of varying the location, and number of balancing planes.

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