A Flexible Rotor on Flexible Bearing Supports: Stability and Unbalance Response

Abstract

An experimental study of the effects of bearing support flexibility on rotor stability and unbalance response is presented. A flexible rotor supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal support stiffness was varied systematically while the vertical stiffness was kept constant. The support characteristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. Stability predictions were compared with measured stability thresholds. The predicted stability thresholds agree with the experimental data within a confidence bound for the logarithmic decrement of ±0.01. For unbalance response, the second critical speed of the rotor varied from 3690 rpm to 5200 rpm, depending on the support configuration. The predicted first critical speeds agree with the experimental data within −1.7 percent. The predicted second critical speeds agree with the experimental data within 3.4 percent. Predictions for the rotor on rigid supports are included for comparison.

Investigate the Effect of Damping Parameters of the Hydrodynamic Bearings Using the Optimization Method of Design of Experiments

“…The non-linear forces are achieved in the hydrodynamic bearing studied the limit stability for a shorthydrodynamic bearing in Newton liquid [5,6]. Some designers have studied the impact of the flexibility of the turbo machinery by using experimental data and procedures allowing to increase the effectiveness and the characteristics [7,8]. In order to study the dynamic behavior of the rotary systems, the use of finite elements was applied to increase models adapted in the field of the dynamics of the rotors and of the hydrodynamic bearings allowed to exploit these models in order to design rotating machines employed with parameters well defined [9].…”

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.…”

Multiphysical effects on high-speed rotordynamics

“…These matrices are then combined with the matrices for the rotor system and the dynamic behavior is predicted. Vazquez et al [81][82][83][84][85] used transfer functions at the bearing locations to model the support structure. These transfer functions are extracted from frequency response functions measured at the bearing locations and then combined with the rotordynamics model.…”

“…Since the flexible supports have an important influence on the dynamics of the structure, they should be included in the rotordynamic structural model [15,22,72,79,[81][82][83][84][85]. Accurate flexible support models demand large efforts and increase the computational time drastically, so simple models are deducted from experimental modal analysis, from static loading tests and by reduction of finite element models [16,74,[81][82][83]85].…”

“…Accurate flexible support models demand large efforts and increase the computational time drastically, so simple models are deducted from experimental modal analysis, from static loading tests and by reduction of finite element models [16,74,[81][82][83]85]. Stephenson and Rouch [74] generated mass and stiffness matrices for the supporting structure from test data.…”