INCOMPRESSIBLE FLOW TURBOMACHINES Design, Selection, Applications,

Transcription

1 INCOMPRESSIBLE FLOW TURBOMACHINES Design, Selection, Applications, George F. Round Professor Emeritus McMaster University Hamilton, Ontario Canada ELSEVIER BUTTERWORTH HEINEMANN Amsterdam Boston Heidelberg London New York Oxford Paris San Diego San Francisco Singapore Sydney Tokyo

2 CONTENTS Preface Nomenclature Dimensions of Fluid Mechanics Quantities Units Fundamental Definitions xiv xvi xviii xix xx Historical Background and Present State of Development, Greek and Roman Machines The Middle Ages The Renaissance The Post Renaissance The Nineteenth Century to the Present General Classification of Rotodynamic Turbines and Pumps Theoretical Limitations References 11 Theory of Turbomachines, Equations Governing the Behavior of Turbomachines Continuity Equation Linear Momentum Theorem Angular Momentum Equation Euler Turbine Equation Bernoulli Equation Example: Use of Bernoulli Equation for Radial Flow The Energy Equation 18 vii

3 VIII Contents 2.8 Similarity Dimensional Analysis Restrictions on Similarity Applications Dimensionless Groups and Specific Speed Scaling Discrepancies Graphical Correlations for Specific Speed General Geometry of Rotational, Radial, and Axial Flows Circulation, Free Vortex Flow, and the Kutta-Joukowski Theorem Forces Acting on an Axial-flow Turbine and Axial-flow Pump Blade Stream Function and Streamlines Velocity Potential Superposition of Streamlines Axisymmetric Flows and Stokes's Stream Function Meridional Streamlines and Velocities Effects of Friction on Flows through Turbomachines Solved Problems References 54 3 Turbines, Classification of Turbines General Operating Conditions Impulse Turbines-Pelton Wheels Speed Factor, <t Specific Speed of Pelton Wheels Nozzles Jet Force on Runner Arrangement of Nozzles and Size of Jets Jet Velocity and Diameter Runner Turgo Wheels Radial-Flow Turbines Francis Turbines Choice of Turbine Speed Effect of Gate Opening Axial-flow Turbines Propeller and Kaplan Turbines Combinator Effects of Rotor and Guide-vane Angle Selection of Speed and Runner Dimensions Other Turbines Pump Turbines, Deriaz Turbine Bulb Turbine 81

4 Contents IX Banki Turbine Michell Turbine Control and Governing of Turbines Function of a Governor Equations for Load Changes Governors Relief Valves Solved Problems References Pumps, Introduction Theoretical Characteristics of Centrifugal Pumps Classification of Rotary Pumps Radial-flow Pumps Geometry Power Theoretical Head Energy Losses Head Losses Leakage Losses Disk Friction Loss Mechanical Losses Specific Speed and Impeller Geometry Modeling of Flow through an Impeller Axisymmetric Flow Net Positive Suction Head (NPSH) Slip Factors Effect of Blade Number, Outlet Blade Angle, and Circulation in Blade Passages Choice of Blade Number and Blade Overlap Energy Recovery Examples of Radial-flow Pumps Installation of a Typical Centrifugal Pump Special-purpose Radial-flow Pumps Mixed-flow Pumps Diagonal Impeller Pumps Axial and Semiaxial Pumps Unbounded Axial Impellers or Propellers Pump Characteristics of Centrifugal Pumps Single Centrifugal Pumps Radial- and Mixed-flow Impellers Effect of Fluid Properties 145

5 Contents 4.7 Series and Parallel Connections Multistage Centrifugal Pumps Displacement Rotary Pumps Vane Pumps Peristaltic Pump Lobe Pumps RVP Pump Water Ring Pumps Flow Control Throttling of the Flow at Inlet or Outlet Pump Disconnection Regulated Flow Bypass Speed Regulation Impeller Blade Adjustment Inlet Guide-vane Adjustment Air Locking Automatic Priming Fluid Couplings Solved Problems References 187 Some Aspects of Design, General Remarks Application to Flow Axial-flow Design Axial and Radial Thrusts in Pumps and Turbines Axial Closed Single-entry Centrifugal Impellers Multistage Balancing of Single-entry Stages Radial Critical Speeds Lateral Critical Speed of an Unbalanced Simple Rotor Multiple Disks Use of Singularity Functions Solution by Numerical Integration Torsional Critical Speed r Seals Cooling Seals Glands Solved Problems References 208

6 Contents XI 6 Design of Impellers and Runners of Single and Double Curvature, General Remarks on Design of Runners and Impellers Single-Curvature Design Meridional Velocities, Inlet Diameter, and Inlet Angle Tip Impeller Velocity, U2, and Outlet Diameter, d Inlet Areas and Impeller Widths Dimension Calculations, Continuity Adjustments Example of Design Blade of Single Curvature Design of Blades of Double Curvature Impeller Blades with Double Curvature Design of Double-curvature Blades by Conformal Mapping References Inlet and Outlet Elements, Inlet Elements of Turbines Surge Tanks Basic Equations for Differential Surge Tanks Instability of the Surge Tank Inlet Elements of Pumps Outlet Elements of Turbines Draft Tubes Outlet Elements of Pumps Volute Design Velocity Distributions in Different Volute Cross Sections Design of a Volute Relation between Volute Velocity and Specific Speed Solved Problem References Head Losses in Components of Turbine and Pump Systems, Pipes Friction Factor Hydraulic Diameter Losses through Other Elements Discharge, Velocity, and Contraction Coefficients Nozzle Loss Fittings, Valves, and Joints 253

7 XII Contents Expansions and Contractions Losses in Pipe Branches Total Frictional Loss in a Pipe System Solved Problems References Cavitation, Causes of Cavitation and Parts Affected Methods of Detecting Cavitation Cavitation in Turbines Thoma Number, a Cavitation in Pumps Cavitation and Specific Speed Determination of Limits of Cavitation Limitations of Similarity Laws Methods of Prevention of Cavitation Conclusions about Cavitation References Water Hammer, Introduction Equations Describing Wave Generation and Propagation Valve Opening or Closure Position as a Function of Time Graphical Solution Other Wave Reflections Reflection at the Closed End of a Pipe Effect of Change of Area Cross Section Junctions and Branches Pump Failure Solved Problems References Corrosion, Introduction Thermodynamics of the Corrosion Process Corrosion of Iron and Steel Effect of Temperature Effect of ph Action of Anaerobic Bacteria Pitting and Crevice Corrosion Corrosion Resistance of Steel Alloys 304

8 Contents XIII 11.5 Stress Corrosion Cracking and Corrosion Fatigue Galvanic or Bimetallic Corrosion Cathodic Protection Sacrificial Anodes Protection and Overprotection Effect of Flow Rate of the Environmental Fluid References 309 Appendices 310 Al Equations 310 A2 Specific Gravity and Viscosity of Water at Atmospheric Pressure 313 A3 Vapor Pressure Chart for Various Liquids 315 A4 Densities of Various Liquids 316 A5 Mathematical and Physical Constants 317 A6 Conversion Factors 318 A7 Beam Formulas and Figures 321 A8 Charts for Flows through Fittings 324 A9 Friction Factor: Reynolds Number Chart (Moody Diagram) 334 A10 Values of Pipe Roughness, e for Various Materials 335 All Characteristic Values of Water in the Saturation States 336 Index 338