A Flexible Rotor on Flexible Bearing Supports: Part I — Stability

1999 ◽  
Author(s):  
José A. Vázquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Frequency Response ◽  
Transfer Functions ◽  
Structure Stability ◽  
Response Functions ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Vertical Stiffness ◽  
Fluid Film Bearings ◽  
Flexible Supports ◽  
Rigid Supports

Abstract An experimental study of the effects of bearing support flexibility on rotor stability is presented. A flexible roto supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal suppor stiffness was varied systematically while the vertical stiffness was kept constant. The support charactristics 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. Predictions for the rotor on rigid supports are included for comparison.

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

2000 ◽  
Vol 123 (2) ◽  
pp. 137-144 ◽  
Author(s):  
Jose´ A. Va´zquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Experimental Data ◽  
Frequency Response ◽  
Transfer Functions ◽  
Structure Stability ◽  
Response Functions ◽  
Flexible Rotor ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Critical Speeds ◽  
Unbalance Response

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.

A Flexible Rotor on Flexible Bearing Supports: Part II — Unbalance Response

1999 ◽  
Author(s):  
José A. Vázquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Experimental Data ◽  
Frequency Response ◽  
Transfer Functions ◽  
Response Functions ◽  
Flexible Rotor ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Critical Speeds ◽  
Vertical Stiffness ◽  
Unbalance Response

Abstract An experimental study of the effects of bearing support flexibility on rotor 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. 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%. The predicted second critical speeds agree with the experimental data within 3.4%. Predictions for the rotor on rigid supports are included for comparison.

Model Calibration of Anisotropic Rotordynamic Systems With Speed Dependent Parameters

2005 ◽  
Author(s):  
A. A. Younan ◽  
A. El-Shafei
Keyword(s):  
Frequency Response ◽  
Model Calibration ◽  
Field Application ◽  
Fluid Film ◽  
Operating Speed ◽  
Response Functions ◽  
Test Rig ◽  
Frequency Response Functions ◽  
Fluid Film Bearings ◽  
Speed Range

In this paper, a method for calibrating rotordynamic models of speed dependent systems supported on anisotropic supports is presented. The method is based on the comparison between the calculated eigenvalues and the ones extracted from the synchronous frequency response functions. An eigensensitivity analysis is conducted to calculate the sensitivity of the computed eigenvalues to the selected elements to be updated. This method is suitable for field application since it requires simple coast down tests. The method is illustrated on a test rig with fluid film bearings, and is shown to be effective in the calibration of rotordynamic models at the speeds of the modes excited within the operating speed range.

Model Calibration of Anisotropic Rotordynamic Systems With Speed-Dependent Parameters

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
A. A. Younan ◽  
A. El-Shafei
Keyword(s):  
Frequency Response ◽  
Model Calibration ◽  
Field Application ◽  
Fluid Film ◽  
Operating Speed ◽  
Response Functions ◽  
Test Rig ◽  
Frequency Response Functions ◽  
Fluid Film Bearings ◽  
Speed Range

In this paper, a method for calibrating rotordynamic models of speed-dependent systems with anisotropic support is presented. The method is based on the comparison between the calculated eigenvalues and those extracted from the measured synchronous frequency response functions. An eigensensitivity analysis is conducted to calculate the sensitivity of the computed eigenvalues to the selected elements to be updated. This method is suitable for field application since it requires simple coastdown tests. The method is illustrated on a test rig with fluid film bearings and is shown to be effective in the calibration of rotordynamic models at the speeds of the modes excited within the operating speed range.

scholarly journals Identification of relevant acoustic transfer paths for WT drivetrains with an operational transfer path analysis

2021 ◽  
Author(s):  
W. Schünemann ◽  
R. Schelenz ◽  
G. Jacobs ◽  
W. Vocaet
Keyword(s):  
Path Analysis ◽  
Wind Turbine ◽  
Frequency Response ◽  
Mechanical System ◽  
Reference Point ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Transfer Path ◽  
Transfer Path Analysis ◽  
Turbine Model

AbstractThe aim of a transfer path analysis (TPA) is to view the transmission of vibrations in a mechanical system from the point of excitation over interface points to a reference point. For that matter, the Frequency Response Functions (FRF) of a system or the Transmissibility Matrix is determined and examined in conjunction with the interface forces at the transfer path. This paper will cover the application of an operational TPA for a wind turbine model. In doing so the path contribution of relevant transfer paths are made visible and can be optimized individually.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 2: Application

1998 ◽  
Vol 120 (2) ◽  
pp. 509-516 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Coupled System ◽  
Companion Paper ◽  
Component Mode Synthesis ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Coupled Beams ◽  
The Individual

This paper demonstrates how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered, as presented in the companion paper, Part I (Morgan et al., 1998). A system of two coupled beams is analyzed using the experimentally-based method. The individual beams’ CMS matrices are calculated from measured frequency response functions. Then, the two beams are analytically coupled together using the test-derived matrices. Good agreement is obtained between the coupled system and the measured results.

Experimental Study for Extraction of Normal Modes

1995 ◽  
Author(s):  
S. Y. Chen ◽  
M. S. Ju ◽  
Y. G. Tsuei
Keyword(s):  
Frequency Response ◽  
Normal Mode ◽  
Normal Modes ◽  
Measurement Data ◽  
Mode Shapes ◽  
Complex Frequency ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Incomplete System ◽  
Coupled Structures

Abstract A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.

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