Turbo Machinery Dynamics Part 1 potx

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ABOUT THE AUTHOR

A S Rangwala received a Master of Science degree in Mechanical Engineering fromDrexel University, Philadelphia, and a Master of Science degree in Industrial Engineeringfrom the University of Cincinnati He has worked for three decades in the field of struc-tural dynamics on compressors and gas turbines applicable to aircraft engines, and steamturbines and generators for power plant applications Mr Rangwala has written papersand reports on all facets of machinery system and component dynamics He has worked

in General Electric Company’s Aircraft Engines Group, both in Cincinnati and in Lynn,Massachusetts, and in GE’s Large Steam Turbines Department in Schenectady, NewYork Mr Rangwala has also worked at Siemens-Westinghouse Power Corporation inOrlando, Florida He now works as an international consultant and teaches short coursesfor practicing engineers on structural vibrations of rotating and reciprocating machinery

He has also served as an adjunct professor at Cincinnati State Technical College

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1.4 Power Generation Overview / 8

1.5 Marine and Industrial Turbines / 10

1.6 Supercharging for Diesel Engines / 10

2.3 High-Bypass Turbofan Engine / 18

2.4 Cycle Analysis Trend / 19

2.5 Performance Evaluation / 27

2.6 Component and Spool Match / 33

2.7 Compressor and Fan Sections / 35

2.8 Turbine Module / 39

2.9 Nacelle Design Concepts / 42

2.10 Experiments in Variable Geometry Intake / 45

2.11 Attachment with Aircraft / 48

2.12 Enhanced Power for Fighter Aircraft / 50

3.2 Simple-Cycle Gas Turbine / 63

3.3 Industrial Combustion Turbine / 67

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vi CONTENTS

3.4 Classification and Characteristics of Steam Turbines / 71

3.5 Advances in Steam Path Technology / 77

3.6 Combined Cycle Mode / 80

3.7 Combined Cycle for Periodic Demand / 83

3.8 Cogeneration / 86

3.9 Heat Recovery Steam Generator / 87

3.10 Compressor Rotor and Stator / 89

3.11 Turbine Construction Features / 94

4.2 Ship Propulsion Plant / 105

4.3 Gas Compression Systems for Pipeline Pumping / 109

4.4 Operational Experience of LM2500 Engine / 111

4.5 Power for Heavy Military Vehicles / 113

Part 2 Component Design

6.1 Introduction / 141

6.2 Stall and Surge / 143

6.3 Airfoil Design Considerations / 146

6.4 Unsteady Viscous Flow / 150

6.5 Flow Characteristics at Stall Inception / 152

6.6 Rotating Instability from Vortex at Blade Tip / 156

6.7 Prospects for Active Stall Control / 159

6.8 Cascade Flutter Analysis / 167

6.9 Fault Identification in Variable Stator Vanes / 170

6.10 End-Wall Blockage / 173

6.11 Acoustic Resonance in Multistage Compressors / 177

6.12 Finite Element Method in Blade Vibrations / 181

6.13 Swept Fan Blade / 186

6.14 Design of Axial Compressor / 190

6.15 Increased Power by Zero Staging / 193

6.16 Prediction of Forced Response / 197

6.17 Random Blade Mistuning / 202

7.2 Impeller Design Features / 224

7.3 Diffuser for Industrial Gas Turbine / 228

7.4 Interaction Between Impeller and Volute / 230

7.5 Flow Characteristics in Vaned Diffuser / 235

7.6 Radial Inflow Turbine / 238

7.7 Stresses in Rotating Disk / 244

7.8 Twin Web Disk / 247

7.9 Disk Burst Capability / 250

7.10 Fluid-Flow Forces in Whirling Impeller / 253

7.11 Uncontained Failure from Fracture of Fan Hub / 256

7.12 Compressor Disk Failure Investigation / 259

8.3 Individual Blade Vibration / 274

8.4 Cumulative Damage Theory in Life Prediction / 277

8.5 Integrity Evaluation of Turbine Blades / 280

8.6 Secondary Flow Loss Control / 284

8.7 Wake–Wake Interaction / 289

8.8 Clocking Effects in Turbine / 294

8.9 Steam and Air Cooling / 297

8.10 Impingement Cooling Aspects / 302

8.11 Nozzle Vane Design / 304

9.8 Dry Low NOxCombustion System / 345

9.9 Catalytic Combustor for Utility Turbine / 349

9.10 Acoustic Resonance / 351

9.11 Active Combustion Instability Control / 355

CONTENTS vii

9.12 Thermal Protection of Combustor Liner / 359

9.13 Structural Design for Dynamic Pressure / 361

10.2 Fluid Film Bearing / 373

10.3 Journal Bearing Types / 377

10.4 Dynamic Characteristics / 380

10.5 Thrust Bearing / 385

10.6 Rolling Element Bearing / 387

10.7 Vapor Phase Lubrication / 392

10.8 Deformation in Ball Bearing / 396

10.9 Tip Clearance Actuation with Magnetic Bearings / 399

10.10 Impact of Flexible Support / 405

10.11 Seals and Dampers / 409

10.12 Labyrinth and Honeycomb Seal Evaluation / 412

10.13 Damping Seal Dynamic Characteristics / 415

10.14 Squeeze Film Damper / 417

10.15 Example Problems / 422

References / 427

Bibliography / 429

Part 3 Materials and Manufacture

11.1 Introduction / 433

11.2 Strengthening Methods / 435

11.3 Nickel Base Alloys / 437

11.4 Cobalt Base Alloys / 440

11.5 Nickel–Iron Alloys / 442

11.6 Processing of Wrought Alloys / 443

11.7 Directionally Solidified Airfoil Technology / 446

17.8 Oxidation and Corrosion Resistance at Elevated Temperatures / 452

11.9 Protective and Thermal Barrier Coats / 453

11.10 Fracture Mechanism of Coats / 458

11.11 Fiber-Reinforced Ceramics for Combustor Liner / 465

11.12 Ceramic Components in MS9001 Engine / 469

CONTENTS ix

12.6 Brazing for Joining Nickel-Based and Cobalt-Based Components / 490

12.7 Laser Welding Techniques / 493

12.8 Generating a Five-Axis Cutter Path / 495

12.9 Machining Methods and Impeller Performance / 500

12.10 Dimensional Instability in Machining Superalloys / 503

12.11 Curvic Coupling for Turbine Rotor / 507

12.12 Vapor Deposition of Thermal Barrier Coating / 509

12.13 Vacuum-Plasma-Sprayed Coatings / 511

References / 515

Bibliography / 516

Index 517

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Dynamic analysis of rotating machinery has come a long way since Professor StephenTimoshenko considered the case of a uniform shaft with a disk at each end in his firsttechnical paper “O Yavleniyakh Rezonansa v Valakh (On Resonance Phenomena in

Shafts)” in the Bulletin of the Polytechnical Institute of St Petersburg Modern

machines have a large number of compressor and turbine blades The design of machinery airfoils is far more complicated due to the complex configuration Theshape of the airfoils is designed from aerodynamics consideration, but the blades muststructurally withstand constant changes in the loads imposed by the flow of fluids overits surface

turbo-When Abdulla S Rangwala came to America in 1967 as a student he was influenced

by the works of Professors S Timoshenko and J den Hartog, using Lord Rayleigh’smethod for resolving vibration problems in engineering His first job was with the LargeSteam Turbines Department of General Electric Company in Schenectady, New York.His initial practical experience was with calculating fundamental periods of torsionaland flexural vibrations of turbine rotor and journal bearing systems and in balancing ofdisks and rotors At GE’s Aircraft Engines Group he gradually shifted his attention tothe design and evaluation of compressor and turbine components The experience with

practical problems has culminated in his writing of Turbo-machinery Dynamics—Design and Operation The book represents a unique compilation of a large number of topics

in an organized manner that is closely associated with the design and evaluation ofturbo-machinery The author presents the latest technical developments in the areas ofengineering, manufacturing, and operation for turbine engineers

With the advent of computers, many important developments in the design and opment of turbo-machinery have occurred Though computers do not fundamentallychange the principles of fluid flow and structural vibration mechanics, they greatly influ-ence the choice of methods of calculation that are most attractive To uphold the technicalexcellence and unique appeal while keeping pace with new developments in the field is

devel-no small responsibility, and the author is to be commended for his fine work

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Considerable interest in the application of the theory of structural dynamics to thedesign of compressors, steam and gas turbines, and pumps has existed for severalyears The need for a comprehensive textbook on the dynamics of the rotating and sta-tionary blades and vanes and the associated disks and shafts incorporating the mostrecent developments of the subject has been strongly felt for a long time

Since the advent of the earliest water-driven power saw mills, problems of deformedand broken turbine blades, shafts, and bearings have plagued the operators and manufac-turers of the machines Problems associated with the relative motion between the rotatingand stationary parts and lubrication were so extensive that little effort was expended inunderstanding the impact of material fatigue, elevated temperature, and load cycling on thedynamic characteristics of the airfoils Although very extensive research has been doneand a great number of publications exist on the subject, little effort has been made to puttogether—in one concise publication—topics such as conceptual design, fluid flow, struc-tural dynamic analysis, design optimization, vibration measurement, and dynamic balance.Numerous other topics closely related to operation, manufacturing, and materials selection

of turbo-machinery components and system have been covered extensively Special sis is placed on computer simulation using finite element methods, correlation of analysiswith experimental test results, and procedures to improve performance efficiency and struc-tural integrity

empha-The basic premise in the operation of all turbo-machines calls for an interactionbetween the fluid media flowing over the surfaces of the stationary and rotating airfoils.Hence, the aerodynamic and structural dynamic characteristics of the airfoils are closelyintertwined The overall profile of the blades must be contoured to maximize the aerody-namic efficiency, but at the same time the part must have adequate structural strength towithstand the many different dynamic excitations imposed on it Dynamic loads arise frommany sources, the predominant one being the source of the operating principles itself onwhich the machine is designed When a rotor blade passes the stationary vanes of the noz-zle, it experiences repeated fluctuating lift and moment loads at a frequency dependent onthe number of vanes and the speed of the machine The rotating airfoils are flexible mem-bers, and possess a number of natural frequencies of vibration about their torsional axis,bending in and out of the plane of rotation of the disk In addition to the steady centrifugalforces arising from its mass, the airfoil must also withstand the dynamic loads due to theaerodynamic excitation Although the blades are designed to avoid resonance at its designspeed, resonant vibrations are still encountered A good example is an aircraft engine asthe aircraft accelerates from ground to flight idle, cruise, and takeoff speeds

This book is written to meet the needs of students in engineering colleges and ticing engineers in a large variety of industries where turbo-machines are used All thematerial has been specifically tailored for college undergraduate and graduate leveldesign engineering and vibration of rotating machine courses Electronic spread-sheettype of calculations are used in example problems to calculate natural frequencies ofvibration, dynamic response, fatigue life, and design parameters related to fluid flow and

prac-xiii

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component sizing It is expected that the reader is familiar with basic- to medium-levelcalculus offered at the college undergraduate level.

The book is split into three parts The first part focuses on the many different tions and forms of turbine engines and their special characteristics and operating features.The five chapters in this part look into the salient features of compressor, turbine, and com-bustor components for various applications of turbo-machines The second part investigatesthe design aspects of the major components The third part discusses associated topics such

applica-as material characteristics and manufacturing methods Since the design features of a machinery and its parts play such an overwhelming role in establishing the dynamic behav-ior of the components, module, or assembly during operation, a close correlation has beenmaintained throughout the book between the design and dynamics disciplines

turbo-The first chapter of Part 1 provides some historical insights about turbo-machines, standing characteristics of aircraft engines and power-generation turbines, and the latesttrends in compression, combustion, and turbine expansion processes The second, third,fourth, and fifth chapters are devoted to applications of turbo-machines for propelling air-craft, power generation and related industrial usage, aviation technology derived marineand industrial turbines, and turbocharging for diesel and automotive engines In Part 2,Component Design, structural integrity in the form of strength and component life man-agement issues for fan and compressor blades are discussed at length in Chapter 6,impellers and bladed disks in Chapter 7, turbine blades and vanes in Chapter 8, combus-tion systems for gas turbines in Chapter 9, and bearings and seals in Chapter 10 Superalloys and manufacturing methods are discussed in Part 3, Chapters 11 and 12

out-A list of symbols is provided mostly to facilitate identification with commonly usedparameters in the equations and the associated text However, because of the considerablenumber of topics the corresponding variables are adequately defined within each section.Oftentimes it is found necessary within the sections to redefine many of the symbols forconvenience and better understanding of the subject matter Thus, the list of symbols may

be used only as a general guideline

ACKNOWLEDGMENTS

I gratefully remember and appreciate past students of the course on this topic who havesent in comments and reported errors, and express my hope that those who work with thistreatise will do likewise I am indebted to Mr Mark Belloni and Dr Fred Ehrich ofGeneral Electric Company for performing a vast amount of computational work in finiteelement analysis and for valuable advice on the text and layout of the book I greatlyappreciate comments provided by Dr Ahmad Kamel, Mr George Robinson, and Dr RajSubbiah of Siemens-Westinghouse Power Corporation, who checked the problems andread the proof

A S RANGWALA

Orlando, Florida

xiv PREFACE

a n Fourier coefficient of Sin(nwt)

b n Fourier coefficient of Cos(nwt)

c damping constant, clearance

f and g numerical factors

F force in general or dry friction force in particular

J polar mass moment of inertia

j √(−1), imaginary unit of complex number

angular momentum vector

magnitude of angular momentum vector

xv

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n station number, number in general, gear ratio

p real part of complex frequency s, pressure

p1, p2 parameters

P o maximum force

P force, potential energy

q natural frequency of damped vibration

x st static deflection, usually, P o /k

y y o Sin(wt) = amplitude of relative motion

y lateral deflection of string or bar

a angle, bypass factor

a n nth crank angle in reciprocating engine

a mn influence number, deflection at m caused by unit force at n

b n angular amplitude of vibration of nth crank

d small length or other parameter in general

f, j phase angle or some other angle

j n phase angle between vibration of nth crank and first crank

w circular frequency = 2pf

w angular velocity

Ω large angular velocity

w n, Ωn natural circular frequencies

xvi LIST OF SYMBOLS

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