Jørgen Lund: A Perspective on His Contributions to Modern Rotor Bearing Dynamics

2003 ◽  
Vol 125 (4) ◽  
pp. 434-440
Author(s):  
Anthony J. Smalley
Keyword(s):  
Knowledge Base ◽  
Modal Testing ◽  
Squeeze Film ◽  
Gas Bearings ◽  
Road Map ◽  
Flexible Rotors ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
Bearing Dynamics ◽  
Rotor Balancing

This paper presents a perspective on the work of Dr. J. W. Lund, in the field of rotor-bearing dynamics. It traces his most influential work in published journals, software, data published in various manuals, government reports, and course notes. It addresses his work in oil bearings, gas bearings, unbalance response of flexible rotors, stability of flexible rotors, squeeze-film dampers, rotor balancing, and modal testing of rotors. It provides a road map for those who would revisit the knowledge base. It shows how Dr. Lund’s work has permeated the practice of today’s suppliers and users of turbomachinery, and industry consultants.

Jorgen Lund: A Perspective on His Contributions to Modern Rotor Bearing Dynamics

2001 ◽  
Author(s):  
Anthony J. Smalley
Keyword(s):  
High Performance ◽  
Industrial Applications ◽  
Modal Testing ◽  
Squeeze Film ◽  
Problem Solution ◽  
Gas Bearings ◽  
Road Map ◽  
Flexible Rotors ◽  
Rotor Bearing ◽  
Bearing Dynamics

Abstract This paper presents a perspective on the work of Dr. J. W. Lund, in the field of rotor-bearing dynamics. Dr. Lund died on November 16, 2000 — indisputably the father of modern rotor-dynamic analysis. The perspective is somewhat personalized, and supplemented by personal knowledge, coming from someone who has known Dr. Lund for over 30 years, who has benefited from the insights of Dr. Lund, and whose career has been measurably advanced as a result of Dr. Lund’s personal and public contributions. The paper traces what the author considers to be the most influential work of Dr. Lund, both in published journals, in the software which has shaped the design and problem solution for modern turbomachinery, and in data published in various manuals, government reports, and course notes. It addresses, in particular, his work in oil bearings, gas bearings, unbalance response of flexible rotors, stability of flexible rotors, squeeze-film dampers, rotor balancing, and modal testing of rotors. It provides a road map for those who would revisit the knowledge base, which has shaped the design of high performance turbomachinery for industrial applications. It shows how the work of Dr. Lund has permeated the practice of today’s suppliers of turbomachinery, the users of turbomachinery, and the consultants to the industry. Some of the publications addressed specifically by the paper are the report volumes on rotor-dynamics prepared under contract by MTI, authored by Dr. Lund, and sponsored by the U.S. Air Force in the mid-1960’s, the RPI-MTI short course notes on gas bearings, software documentation, and major papers.

Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1983 ◽  
Vol 105 (3) ◽  
pp. 606-614 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.

scholarly journals Analytical and Experimental Investigation of the Stability of the Rotor-Bearing System of a New Small Turbocharger

1987 ◽  
Author(s):  
H. R. Born
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stability ◽  
Squeeze Film ◽  
Test Results ◽  
Flow Capacity ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
The Stability ◽  
Turbine Design ◽  
Bearing System

This paper presents an overview of the development of a reliable bearing system for a new line of small turbochargers where the bearing system has to be compatible with a new compressor and turbine design. The first part demonstrates how the increased weight of the turbine, due to a 40 % increase in flow capacity, influences the dynamic stability of the rotor-bearing system. The second part shows how stability can be improved by optimizing important floating ring parameters and by applying different bearing designs, such as profiled bore bearings supported on squeeze film dampers. Test results and stability analyses are included as well as the criteria which led to the decision to choose a squeeze film backed symmetrical 3-lobe bearing for this new turbocharger design.

Theoretical and Experimental Studies on Squeeze Film Stabilizers for Flexible Rotor-Bearing Systems Using Newtonian and Viscoelastic Lubricants

1990 ◽  
Vol 112 (4) ◽  
pp. 473-482 ◽  
Author(s):  
B. Halder ◽  
A. Mukherjee ◽  
R. Karmakar
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotor ◽  
Stability Range ◽  
High Speeds ◽  
Flexible Rotors ◽  
Rotor Bearing

A combination of a squeeze film damper and a plane journal bearing is studied as a stabilizing scheme. The damper is made to play the role of a stabilizer to postpone the instability threshold speeds of flexible rotors. Both Newtonian and viscoelastic fluids are used in the rotor-bearing system. Dynamics of the system is theoretically analyzed using bond graphs. Analysis reveals that the use of a Newtonian fluid in the stabilizer largely improves the high speed stability range. However, viscoelastic stabilizing fluid has a detrimental effect on highly flexible rotors. Experimental investigations, conducted on a flexible rotor (natural frequency, 30 Hz), confirm the theoretical findings. In addition, experiments indicate that though the use of viscoelastic stabilizing fluids leads to instability in flexible rotors, the growth of large amplitude whirl is postponed to very high speeds.

Use of the Harmonic Balance Method for Flexible Aircraft Engine Rotors With Nonlinear Squeeze Film Dampers

2014 ◽  
Author(s):  
Feng He ◽  
Paul Allaire ◽  
Timothy Dimond
Keyword(s):  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Aircraft Engine ◽  
Balance Method ◽  
Squeeze Film ◽  
Spring Stiffness ◽  
Squeeze Film Damper ◽  
Flexible Rotors ◽  
Squeeze Film Dampers ◽  
Nonlinear Transient

Squeeze film dampers in flexible rotors such as those in compressors, steam turbines, aircraft engines and other rotating machines are often modeled as linear devices. This linearization is valid only for a specified orbit where appropriate equivalent stiffness and damping coefficients can be found. However, squeeze film dampers are inherently nonlinear devices which complicates the analysis. This paper develops the harmonic balance method with a direct force model of the SFDs. This model is used for flexible rotors with squeeze film dampers where the rotor is treated as linear and the squeeze film damper is treated as nonlinear. The predictor-corrector method is employed to obtain the system forced response in the frequency domain after separating the nonlinear components from the linear components of the equations of motion. This approach is much more efficient than conventional full nonlinear transient analysis. The application considered in this paper is the low pressure (LP) compressor of an aircraft engine. The LP compressor rotor has two roller bearings with squeeze film dampers and one ball bearing without a squeeze film damper. Orbits at the fan end dampers and the turbine end dampers for both the harmonic balance and nonlinear transient modeling are compared for accuracy and calculation time. The HB method is shown to be 5 to 12 times faster computationally for similar results. Fast Fourier transform results were obtained for various shaft operating speeds. Results were also obtained for the unbalance response at different locations with gravity loading. Finally, unbalance response of the rotor with varying centering spring stiffness values were obtained. The results show that the centering spring stiffness for the turbine end damper is less sensitive than the fan end damper.

Dynamic Response and Stability of Pressurized Gas Squeeze-Film Dampers

1998 ◽  
Vol 120 (1) ◽  
pp. 306-311
Author(s):  
N. K. Arakere ◽  
B. C. Ravichandar
Keyword(s):  
High Temperature ◽  
Gas Flow ◽  
Squeeze Film ◽  
Orifice Diameter ◽  
Oil Lubrication ◽  
Damping Force ◽  
Circular Orbits ◽  
Foil Bearings ◽  
Flexible Rotors ◽  
Squeeze Film Dampers

Compressible squeeze films, an important and interesting area in gas lubrication, have been relatively neglected in recent times. Aircraft engines are being designed with light weight flexible rotors operating at high speeds and temperatures that may eventually eliminate the use of oil lubrication. A gas or air SFD might be a viable alternative to a conventional oil damper, in high temperature applications that preclude the use of oil lubrication. Oil squeeze-film dampers currently being used for rotordynamic control will not be viable at temperatures above 350°F, due to limitations on lubricant oil temperature. A good example of gas SFD application is in conjunction with high temperature gas lubricated foil bearings, which inherently have low damping. This paper presents an analysis of pressurized air dampers, similar to a hydrostatic gas bearing. Pressurized air is supplied through a series of orifices in the bearing midplane. Airflows through the orifices and the resulting pressure forces are calculated using a simple gas-flow model, as in orifice compensated hydrostatic bearings. A small perturbation analysis of the shaft center yields the stiffness and damping coefficients, for centered circular orbits. Damping characteristics are studied for a range of parameters such as supply pressure, orifice diameter, pocket volume, orbit size, number of orifices and shaft speed. Results show that maximum damping forces are generated for near choking flow conditions. The damping coefficient becomes negligible at frequencies above 350 Hz. For damping force to be present, the gas pressurization has to exert a force on the rotor opposing the instantaneous velocity, or, 90 degrees out of phase with displacement. Linear stability of unbalanced dampers undergoing centered circular orbits, is also investigated, in view of their relevance to rotordynamics. Damper design curves are presented for various parameters.

Imbalance Response of a Rotor Supported on Flexure Pivot Tilting Pad Journal Bearings in Series With Integral Squeeze Film Dampers

2001 ◽  
Author(s):  
Luis San Andrés ◽  
Oscar De Santiago
Keyword(s):  
Peak Amplitude ◽  
Squeeze Film ◽  
Critical Speeds ◽  
Rotor Imbalance ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
In Series ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearings

Measurements of the imbalance responses of a massive 45 kg rotor supported on series (flexure pivot) tilting pad bearings and integral squeeze film dampers (SFDs) are presented. The rotor-bearing configuration is of interest in compressor applications where often oil lubricated dampers are introduced in series with fluid film bearings to relocate critical speeds, enhance the overall system damping, and reduce the risks of rotordynamic instabilities due to seals and impellers, for example. Coast-down experiments from 9,000 rpm are conducted for increasing levels of rotor imbalance, and equivalent system damping coefficients identified from the peak amplitude of rotor response while traversing cylindrical mode critical speeds. The tests performed with locked (inactive) and active SFDs demonstrate the effectiveness of the flexible damped support in reducing the system critical speed and improving the overall rotor response with reduced transmitted forces to ground. The SFDs allow safe rotor operation with values of imbalance twice as large as the maximum sustained by the rotor supported on tilting pad bearings alone. The experiments reveal a linear relationship between the peak amplitude of vibration at the critical speeds and the imbalance displacement, even for rotor motions larger than 50% of the tilting pad bearing and damper clearances. The tests also show little cross-coupling effects with the shaft centerline moving along a nearly vertical path. The rotor-bearing system remained stable in the entire range of operation and without the appearance of subsynchronous vibration or non-linear damper jump response.

Imbalance Response of a Rotor Supported on Flexure Pivot Tilting Pad Journal Bearings in Series With Integral Squeeze Film Dampers

2003 ◽  
Vol 125 (4) ◽  
pp. 1026-1032 ◽  
Author(s):  
L. San Andre´s ◽  
O. De Santiago
Keyword(s):  
Peak Amplitude ◽  
Squeeze Film ◽  
Critical Speeds ◽  
Rotor Imbalance ◽  
Squeeze Film Dampers ◽  
Tilting Pad ◽  
Rotor Bearing ◽  
In Series ◽  
Tilting Pad Bearings ◽  
Tilting Pad Journal Bearings

Measurements of the imbalance responses of a massive 45 kg rotor supported on series (flexure pivot) tilting pad bearings and integral squeeze film dampers (SFDs) are presented. The rotor-bearing configuration is of interest in compressor applications where often oil lubricated dampers are introduced in series with fluid film bearings to relocate critical speeds, enhance the overall system damping, and reduce the risks of rotordynamic instabilities due to seals and impellers, for example. Coast-down experiments from 9000 rpm are conducted for increasing levels of rotor imbalance, and equivalent system damping coefficients identified from the peak amplitude of rotor response while traversing cylindrical mode critical speeds. The tests performed with locked (inactive) and active SFDs demonstrate the effectiveness of the flexible damped support in reducing the system critical speed and improving the overall rotor response with reduced transmitted forces to ground. The SFDs allow safe rotor operation with values of imbalance twice as large as the maximum sustained by the rotor supported on tilting pad bearings alone. The experiments reveal a linear relationship between the peak amplitude of vibration at the critical speeds and the imbalance displacement, even for rotor motions larger than 50% of the tilting pad bearing and damper clearances. The tests also show little cross-coupling effects with the shaft centerline moving along a nearly vertical path. The rotor-bearing system remained stable in the entire range of operation and without the appearance of subsynchronous vibration or nonlinear damper jump response.

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