Basic Concepts in Turbomachinery

Author Grant Ingram
ISBN 978-87-7681-435-9
1 edition
144 pages

Description

This book is about the fundamentals of turbomachinery, the basic operation of pumps, aircraft engines, wind turbines, turbomachinery for power generation and hydro-electric machines. It compliments courses that you will be studying in these areas by concentrating on getting the basics right. Enormous emphasis is placed on relating the complex geometry of turbomachines to the fundamental analysis models used throughout the design of all turbomachinery. The simple techniques described in the book provide the basis for preliminary design of all turbomachinery and so mastering the concepts in this book provides a solid foundation for later study.

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Preface

This book is based on an introductory turbomachinery course at Durham University. This course was taught by Dr David Gregory-Smith and Professor Li He over a number of years and I am extremely grateful to them for providing a clear and lucid set of principles on which to base this work.

My current colleagues at Durham Dr Rob Dominy and Dr David Sims-Williams have also provided invaluable help (even if they didn’t realise it!) in preparing this work.

The book is designed to help students over some important “Threshold Concepts” in educational jargon. A threshold concept is an idea that is hard to grasp but once the idea is understood transforms the student understanding and is very hard to go back across. Within turbomachinery my view is that understanding the cascade view, velocity triangles and reaction form three threshold concepts, perhaps minor ones compared to the much bigger ideas such as "reactive power" or "opportunity cost" that are also proposed but this view has significantly influenced the production of this book.

I’d therefore like to acknowledge Professor Eric Meyer for introducing me to the idea of threshold concepts.

1 Introduction
1.1 How this book will help you
1.2 Things you should already know
1.3 What is a Turbomachine?
1.4 A Simple Turbine
1.5 The Cascade View
1.6 The Meridional View
1.7 Assumptions used in the book
1.8 Problems

2 Relative and Absolute Motion
2.1 1D Motion
2.2 2D Motion
2.3 Velocity Triangles in Turbomachinery
2.4 Velocity Components
2.5 Problems

3 Simple Analysis of Wind Turbines
3.1 Aerofoil Operation and Testing
3.2 Wind Turbine Design
3.3 Turbine Power Control
3.4 Further Reading
3.5 Problems

4 Different Turbomachines and Their Operation
4.1 Axial Flow Machines
4.2 Radial and Centrifugal Flow Machines
4.3 Radial Impellers
4.4 Centrifugal Impellers
4.5 Hydraulic Turbines
4.6 Common Design Choices
4.7 The Turbomachine and System
4.8 Problems

5 Application of The Equations of Fluid Motion
5.1 Conservation of Mass
5.1.1 Application to Radial Machines
5.2 Conservation of Momentum
5.2.1 The Difference Between a Single Aerofoil and a Cascade of Blades
5.3 Conservation of Energy and Rothalpy
5.3.1 Rothalpy
5.3.2 Rothalpy in Stators and Rotors
5.4 Problems

6 Efficiency and Reaction
6.1 Efficiency
6.1.1 Using Efficiency
6.1.2 Other Efficiency Definitions
6.2 Reaction
6.3 Reaction on the h − s Diagram
6.4 Problems

7 Dimensionless Parameters for Turbomachinery
7.1 Coefficients for Axial Machines
7.2 Coefficients for Wind Turbines
7.3 Coefficients for Hydraulic Machines
7.3.1 Specific Speed for Turbines
7.3.2 Specific Speed for Pumps
7.3.3 Using Specific Speeds
7.4 Problems

8 Axial Flow Machines
8.1 Reaction for Repeating Stage
8.1.1 Zero Reaction (Impulse) Stage
8.1.2 50% Reaction Stage
8.2 Loading and Efficiency Variation with Reaction
8.3 Stage Efficiency
8.4 Choice of Reaction for Turbines
8.5 Compressor Design
8.6 Multistage Steam Turbine Example
8.7 Problems

9 Hydraulic Turbines
9.1 Pelton Wheel
9.2 Analysis Approach
9.3 Francis Turbine
9.4 Kaplan Turbine
9.4.1 Loss Estimation
9.4.2 Draft Tube Analysis
9.4.3 Effect of Draft Tube
9.5 Problems

10 Analysis of Pumps
10.0.1 Pump Geometry and Performance
10.1 Pump Diffuser Analysis
10.2 Pump Losses
10.3 Centrifugal Pump Example
10.4 Net Positive Suction Head (NPSH)
10.4.1 Cavitation Example
10.5 Application to Real Pumps
10.6 Problems

11 Summary

Appendix A: Glossary of Turbomachinery Terms

Appendix B: Picture Credits

List of Figures

1.1 Applications of Turbomachinery

1.2 A Simple Turbine

1.3 A Simple Turbine: Exploded View

1.4 Simple Turbine Operation

1.5 Cascade View

1.6 The Cascade View as a Large Radius Machine

1.7 Meridional View

2.1 Relative and Absolute Velocities for a Cyclist

2.2 Velocity Triangles for an Aircraft Landing

2.3 Graphical Addition and Subtraction of Vectors

2.4 Cascade and Meridional Views of a Turbine Stage

2.5 Velocity Triangles for a Turbine Stage

2.6 Velocity Triangles at Station 3 of a Turbine

2.7 Velocity Triangles for a Desk Fan

3.1 Wind Turbine Picture and Sketch

3.2 Wind Turbine Blade and Velocity Triangle

3.3 Forces on a Wind Turbine Blade

3.4 Aerofoil at Two Incidences

3.5 CL and CD for a NACA 0012 Aerofoil

3.6 Relationship between γ and i

3.7 Schematic Showing Wind Turbine Pitch Control

4.1 Radial Pump

4.2 3D View of the Radial Impeller

4.3 Centrifugal Impeller

4.4 The Cascade View for a Radial Impeller

4.5 Velocity Triangles for a Radial Impeller

4.6 Common errors in Velocity Triangles

4.7 Constructing the Cascade View for a Centrifugal Impeller

4.8 Velocity Triangles for a Centrifugal Impeller

4.9 Schematic of Hydro-Electric Scheme

4.10 The Four Major Types of Hydraulic Turbine

4.11 Pelton’s Patent Application and Analysis Model

4.12 Three Dimensional Views of a Francis Turbine

4.13 Three Dimensional Views of a Kaplan Turbine

5.1 Meridional View of a Gas Turbine

5.2 Meridional Views of Radial and Centrifugal Machines

5.3 A Generic Turbomachinery Flow Passage

5.4 Isolated Aerofoil compared to a Cascade

5.5 Generic Velocity Triangle

6.1 Enthalpy-Entropy Diagram for a Turbine

6.2 Enthalpy-Entropy Diagram for a Compressor

6.3 Basic h-s diagram

6.4 h-s diagram with h0

6.5 h-s diagram with h0 and h0rel

7.1 Velocity triangles for exit and inlet combined

7.2 CP vs λ for 2.5MW Wind Turbine

7.3 Collapsing Pump Data onto Non-dimensional Curves

7.4 Specific Speed for a Number of Hydraulic Turbines

8.1 h-s diagram with h0 and h0rel

8.2 Impulse and 50% Reaction Blading

8.3 Locations for Tip Clearance Flow

8.4 Schematics of Disc and Diaphragm Construction

9.1 Pelton’s Patent Application and Analysis Model

9.2 Analysis of a Francis Turbine

9.3 Velocity Triangle for Francis Turbine Guide Vane Exit

9.4 Velocity Triangle for Francis Runner Exit

9.5 Analysis of a Kaplan Turbine

9.6 Velocity Triangle for a Kaplan Turbine at Guide Vane Exit

9.7 Velocity Triangle for a Kaplan Runner

10.1 Three Blade Angles at Impeller Exit

10.2 H vs Q for Three Blade Angles

10.3 P vs Q for Three Blade Angles

10.4 Inlet to Pump Impeller

10.5 Exit from Pump Impeller

10.6 Pump Inlet

About the Author

Author's websites
http://www.dur.ac.uk/g.l.ingram/
http://www.dur.ac.uk/ecs/engineering/staff/teachstaff/?id=2764

Grant Ingram graduated from Durham University in 1997 on the first cohort of the then brand new MEng degree. After two years in the electricity supply industry working on power stations large and small he returned to Durham to complete a PhD sponsored by Rolls-Royce. Technology developed in conjuction with his work is now flying around in aeroplanes around the world.

Following the successful conclusion of his PhD, Grant spent a year working at the Engineering Design Centre at Newcastle University before joining the School of Engineering as a lecturer in September 2005.

Since then he has worked on two key areas of research: 1. Making Turbomachinery more efficient and 2. Making renewable devices work better. Both of these activities are approached from a fluid dynamics background.

He won the PE Publishing Prize for the best paper published in the Journal of Power and Energy in 2008 and in 2009 published his first book which is available as a free download.

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