Including the Effects of Flexible Bearing Supportsin Rotating Machinery

Abstract

Unbalance response and stability analyses of a flexible rotor on three lobe journal bearings on flexible supports are presented. The influence of the support structure was included in the analyses using polynomial transfer functions. These transfer functions were extracted from measured dynamic compliance data of the support structure, measured at the bearing locations. Numerical predictions using polynomial transfer functions and single mass supports are compared to the experimental data. Predictions using the transfer function representation of the support structure show a clear improvement over the predictions using single mass supports without over-complicating the problem. The predicted critical speeds are within 2.9% of the measured critical speeds. The predicted stability threshold agrees with the measured stability threshold within 1%. The effects of cross talk between supports and cross coupling between horizontal and vertical directions are investigated. The cross talk between supports was found to have a strong influence in the results while the influence of cross coupling between the vertical and horizontal directions is negligible.

Theoretical Modeling for a Rotor-Bearing-Foundation System and Its Dynamic Characteristics Analysis

“…What brings to decision for application of MDOF models. Vasquez et al [7,8] proposed a method to include the dynamic characteristics of bearing supports using transfer function, where it could be extracted from modal information of the supports or from experimentally obtained forced response functions of the substructures at the bearing locations. Edwards et al based on experimental equipment proposed an identification method for the flexible foundation parameters using run-up/run-down method [9][10][11].…”

Improving the Stability and Critical Speed of Rotor Bearing System By Using External Damping Source

“…[1], have been examined the stiffness influences on dynamic parameters of rotor bearing and foundation systems and they concluded that, the increasing of foundation size leads to rises the mode natural frequencies and expands the operating speed range. Vazquez et al [2] have been studied the effects of bearings mounted on flexible supports on the dynamic response and critical speed and they concluded the cross coupling coefficients does not have a large effect on the dynamic response and critical speed. David et al [3] study the effect of using roller bearings on the vibration amplitude of rotor and they concluded that damping will significantly decrease the rotor vibration amplitude.…”

A Flexible Rotor on Flexible Supports: Modeling and Experiments

“…This can be accomplished by predicting rotor dynamic behavior properly. Since the flexible supports have an important role on the dynamics of the structure, they should be taken into account in the rotordynamic structural model [1][2][3][4][5][6][7][8][9]. However including a detailed model of the support requires much effort and increases the computational time drastically.…”