Machinery Vibration and Rotordynamics

by Vance, John M.; Zeidan, Fouad Y.; Murphy, Brian G.

• ISBN13: 9780471462132
• ISBN10: 0471462136
• Edition: 1st
• Format: Hardcover
• Copyright: 2010-05-24
• Publisher: Wiley

Summary

The book is a text/reference for rotating machinery vibrations and related topics such as bearings and seals with information suitable for both novices and experts. It contains fundamental physical phenomena, mathematical and computational aspects, practical hardware considerations and troubleshooting and instrumentation and measurement techniques. Case studies of vibration problems in several different types of machines are included as well as computer simulation models used in industry. With applicable theory supplying the tools for success, Machine Vibration and Rotordynamics is a must have for engineers and designers.

Author Biography

Dr. JOHN M. VANCE was professor of mechanical engineering at Texas A&M University, retiring in 2007. He received his PhD (1967) degree from The University of Texas at Austin. His book Rotordynamics of Turbomachinery (Wiley) has sold more than 3,000 copies and is used by turbomachinery engineers around the world. He is an inventor on several patents relating to rotating machinery and vibration reduction. His patented TAMSEAL has been retrofitted to solve vibration problems in a number of high-pressure industrial compressors. He is an ASME Fellow and a registered professional engineer in the state of Texas.

Dr. FOUAD Y. ZEIDAN is the President of KMC, Inc., and Bearings Plus, Inc., two companies specializing in the supply of high-performance bearings, flexible couplings, and seals. Dr. Zeidan holds nine U.S. patents for integral squeeze film dampers and high-performance journal and thrust bearings. He has published more than thirty technical papers and articles on various turbomachinery topics and has been lecturing at the Annual Machinery Vibrations and Rotordynamics short course since 1991. Dr. Zeidan holds a BS, MS, and PhD degrees in mechanical engineering from Texas A&M University.

BRIAN T. MURPHY, PhD, PE, is a senior research scientist with the Center for Electromechanics at The University of Texas at Austin. He is also president of RMA, Inc., which develops and markets the Xlrotor suite of rotordynamic analysis software used worldwide by industry and academia. Dr. Murphy is the creator of the polynomial transfer matrix method, which is the fastest known method of performing rotordynamic calculations. He has authored numerous technical papers on rotordynamics and machinery vibration, and is also caretaker of the Web site www.rotordynamics.org.

Table of Contents

Dedication

Preface

Fundamentals of Machine Vibration and Classical Solutions

The Main Sources of Vibration in Machinery

The Single Degree of Freedom (SDOF) Model

Using Simple Models For Analysis And Diagnostics

Six Techniques for Solving Vibration Problems With Forced Excitation

Identify And Reduce The Excitation Source

Tune The Natural Frequency To A Value Further Away From The Frequency Of Excitation To Avoid Resonance

Isolate The Modal Mass From The Vibratory Excitation By Making The Modal Stiffness Very Low

Add Damping To The System

Add A Vibration Absorber

Stiffen The System

Some Examples with Forced Excitation

Illustrative Example #1

Illustrative Example #2:

Illustrative Example #3:

Illustrative Example #4:

Some Observations about Modeling

Unstable Vibration

References

Exercises - Chapter 1

Torsional Vibration

Torsional Vibration Indicators

Torsional and Lateral Vibration - The Key Differences

Objectives of Torsional Vibration Analysis

Simplified Models

Computer Models

Kinetic Energy expression:

Potential Energy

Torsional Vibration Measurement

Frenc's Comparison Experiments

Strain Gages

Carrier Signal Transducers

Frequency-Modulated Systems

Amplitude-Modulated Systems

Frequency Analysis and the Sideband System

Frenc's Test Procedure and Results

A Special Tape for Optical Transducers

Time Interval Measurement Systems

Tora's Method

Barrios/Darlow Method

References

Exercises

Introduction to Rotordynamics Analysis

Objectives Of Rotordynamics Analysis

The Spring-Mass Model

Synchronous And Nonsynchronous Whirl

Analysis Of The Jeffcott Rotor

Polar Coordinates

Cartesian Coordinates

Physical Significance of the Solutions

Three Ways to Reduce Synchronous Whirl Amplitudes

Some Damping Definitions

The "Gravity Critical"

Critical Speed Definitions

Effect Of Flexible (Soft) Supports

Rotordynamic Effects Of The Force Coefficients - A Summary

The Direct Coefficients

The Cross Coupled Coefficients

Rotordynamic Instability

Effect Of Cross-Coupled Stiffness On Unbalance Response

Added Complexities

Gyroscopic Effects

Effect Of Support Asymmetry On Synchronous Whirl

False Instabilities

Agreement of the sub-synchronous frequency with known eigenvalues of the system

Presence of higher harmonics or multiple frequencies

Orbit Shape - Ellipticity

Sub-synchronous frequency exactly one half of shaft speed

Sub-synchronous frequency equal to a torsional natural frequency

A change in the measured synchronous phase angle due to cross-coupled stiffness

References

Exercises

Computer Simulations of Rotordynamics

Different Types Of Models

Bearing & Seal Matrices

Torsional and Axial Models

Different Types Of Analyses

Eigenanalysis

Linear Forced Response (LFR)

Transient Response

Shaft Modeling Recommendations

How Many Elements

45 Degree Rule

Interference Fits

Laminations

Trunnions

Impeller Inertias via CAD Software

Stations for Added Weights

Rap Test Verification of Models

Stations for Bearings and Seals

Flexible Couplings

Example Simulations

Damped Natural Frequency Map (NDF)

Modal Damping Map

Root Locus Map

Undamped Critical Speed Map

Mode Shapes

Bode/Polar Response Plot

Orbit Response Plot

Bearing Load Response Plot

Operating Deflected Shape (ODS)

Housing Vibration (ips & 's)

List of References

Bearings and Their Effect on Rotordynamics

Fluid Film Bearings

Fixed Geometry Sleeve Bearings

Variable Geometry Tilting Pad Bearings

Fluid Film Bearing Dynamic Coefficients and Methods of Obtaining Them

Load Between Pivot (LBP) vs. Load on Pivot (LOP)

Influence of Preload on the Dynamic Coefficients in Tilt Pad Bearings

Influence of the Bearing Length or Pad Length

Influence of the Pivot Offset

Influence of the Number of Pads

Ball and Rolling Element Bearings

Case Study: Bearing Support Design for a Rocket Engine Turbopump

Ball Bearing Stiffness Measurements

Wire Mesh Damper Experiments and Computer Simulations

Squeeze Film Dampers

Squeeze Film Damper without a Centering Spring

O-Ring Supported Dampers

Squirrel Cage Supported Dampers

Integral Squeeze Film Dampers

Squeeze Film Damper Rotordynamic Force Coefficients

Applications of Squeeze Film Dampers

Optimization for Improving Stability in a Centrifugal Process Compressor

Using Dampers to Improve the Synchronous Response

Using the Damper to Shift a Critical Speed or a Resonance

Insights into the Rotor Bearing Dynamic Interaction with Soft/Stiff Bearing Supports

Influence on Natural Frequencies with Soft/Stiff Bearing Supports

Effects of Mass Distribution on the Critical Speeds with Soft/Stiff Bearing Supports

Influence of Overhung Mass on Natural Frequencies with Soft/Stiff Supports

Influence of Gyroscopic Moments on Natural Frequencies with Soft/Stiff bearing supports

Exercises

References

Fluid Seals and Their Effect on Rotordynamics

Function and Classification of Seals

Plain Smooth Seals

Floating Ring Seals

Conventional Gas Labyrinth Seals

Pocket Damper Seals

Honeycomb Seals

Hole Pattern Seals

Brush Seals

Understanding and Modeling Damper Seal Force Coefficients

Alfor's Hypothesis of Labyrinth Seal Damping

Cross-Coupled Stiffness Measurements

Invention of the Pocket Damper Seal

Pocket Damper Seal Theory

Rotordynamic Testing of Pocket Damper Seals

Impedance Measurements of Pocket Damper Seal Force Coefficients (Stiffness and Damping) and Leakage at Low Pressures

The Fully Partitioned PDS Design

Effects of Negative Stiffness

Frequency Dependence of Damper Seals

Laboratory Measurements of Stiffness and Damping from Pocket Damper Seals at High Pressures

The Conventional Design

The Fully Partitioned Design

Field Experience with Pocket Damper Seals

Designing for Desired Force Coefficient Characteristics

The Conventional PDS Design

The Fully Partitioned Pocket Damper Seal

Leakage Considerations

Some Comparisons of Different Types of Annular Gas Seals

Sources

References

History of Machinery Rotordynamics

The Foundation Years, 1869-1941

Summary

Shaft Dynamics

Bearings

Refining and Expanding The Rotordynamic Model, 1942-1963

Multi-Stage Compressors and Turbines, Rocket Engine Turbopumps, and Damper Seals, 1964 - Present

Stability Problems With Multi-Stage Centrifugal Compressors

Kaybob, 1971-72

Ekofisk, 1974-75

Subsequent Developments

New Frontiers of Speed and Power Density With Rocket Engine Turbopumps

The Space Shuttle Main Engine (SSME) High-Pressure Fuel Turbopump (HPFTP) Rotordynamic Instability Problem

Non-Contacting Damper Seals

List of references

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