Machinery Vibration and Rotordynamics

by John M. Vance (Texas A&; M University); Fouad Y. Zeidan (Bearings Plus, Inc.); Brian Murphy (RMA, Inc.)

• ISBN13: 9780470916070
• ISBN10: 0470916079
• Format: eBook
• Copyright: 2010-06-01
• Publisher: Wiley

Summary

An in-depth analysis of machine vibration in rotating machineryWhether it's a compressor on an offshore platform, a turbocharger in a truck or automobile, or a turbine in a jet airplane, rotating machinery is the driving force behind almost anything that produces or uses energy. Counted on daily to perform any number of vital societal tasks, turbomachinery uses high rotational speeds to produce amazing amounts of power efficiently. The key to increasing its longevity, efficiency, and reliability lies in the examination of rotor vibration and bearing dynamics, a field called rotordynamics.A valuable textbook for beginners as well as a handy reference for experts, Machinery Vibration and Rotordynamics is teeming with rich technical detail and real-world examples geared toward the study of machine vibration. A logical progression of information covers essential fundamentals, in-depth case studies, and the latest analytical tools used for predicting and preventing damage in rotating machinery. Machinery Vibration and Rotordynamics:Combines rotordynamics with the applications of machinery vibration in a single volumeIncludes case studies of vibration problems in several different types of machines as well as computer simulation models used in industryContains fundamental physical phenomena, mathematical and computational aspects, practical hardware considerations, troubleshooting, and instrumentation and measurement techniquesFor students interested in entering this highly specialized field of study, as well as professionals seeking to expand their knowledge base, Machinery Vibration and Rotordynamics will serve as the one book they will come to rely upon consistently.

Table of Contents

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

Some Examples with Forced Excitation

Some Observations about Modeling

Unstable Vibration

References

Exercises

Torsional Vibration

Torsional Vibration Indicators

Objectives of Torsional Vibration Analysis

Simplified Models

Computer Models

Kinetic Energy Expression

Potential Energy

Torsional Vibration Measurement

French's Comparison Experiments

Strain Gages

Carrier Signal Transducers

Frequency-modulated Systems

Amplitude-modulated Systems

Frequency Analysis and the Sideband System

French's Test Procedure and Results

A Special Tape for Optical Transducers

Time-interval Measurement Systems

Results from Toram's Method

Results from the 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

References

Exercises

Computer Simulations of Rotordynamics

Different Types of Models

Bearing and 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 and g 's)

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 Pivots Versus Load on Pivot

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

References

Exercises

Appendix: Shaft With No Added Weight

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

Alford'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

Two Back-to-Back Compressor Applications

A Fully Partitioned Application

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

References

History of Machinery Rotordynamics

The Foundation Years, 1869-1941

Shaft Dynamics

Bearings

Refining and Expanding the Rotordynamic Model, 1942-1963

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

Stability Problems with Multistage 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

Noncontacting Damper Seals

Shaft Differential Heating (The Morton Effect)

References

Index

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