Contents. 2 Basic Components Aerofoils Force Generation Performance Parameters xvii

Size: px

Start display at page:

Download "Contents. 2 Basic Components Aerofoils Force Generation Performance Parameters xvii"

Beryl Booth
6 years ago
Views:

1 Contents 1 Working Principles Definition of a Turbomachine Examples of Axial Turbomachines Axial Hydraulic Turbine Axial Pump Mean Line Analysis Basic Laws for Stationary Duct Parts Conservation of Mass Conservation of Momentum Conservation of Energy Forms of Energy: Mechanical Energy and Head Energy Dissipation: Head Loss Basic Laws for Rotating Duct Parts Work and Energy Equations in a Rotating Frame with Constant Angular Velocity Moment of Momentum in the Absolute Frame: Rotor Work Moment of Momentum in the Relative Frame: Forces Intervening in the Rotor Work Energy Component Changes Caused By the Rotor Work Rotor Work in the Mean Line Representation of the Flow Energy Analysis of Turbomachines Mechanical Efficiency and Internal Efficiency Energy Analysis of an Axial Hydraulic Turbine Energy Analysis of an Axial Pump Examples of Radial Turbomachines Performance Characteristics Exercises References Basic Components Aerofoils Force Generation Performance Parameters xvii

2 xviii Contents Pressure Distribution Boundary Layer Separation Loss Mechanism Associated to Friction: Energy Dissipation Profile Shapes Blade Rows with Low Solidity Linear Cascades Relation with the Real Machine Cascade Geometry Flow in Lossless Cascades: Force Components Significance of Circulation Flow in Lossless Cascades: Work Flow in Cascades with Loss: Force Components Flow in Cascades with Loss: Energy Dissipation and Work by Drag Force The Zweifel Tangential Force Coefficient The Lieblein Diffusion Factor Performance Parameters of Axial Cascades Channels Straight Channels Bends Diffusers Dump Diffusers Inlet Flow Distortion Flow Separation Flow Improvement Representation of Diffuser Performance Equivalent Opening Angle Diffusion in a Bend Exercises References Fans Fan Aplications and Fan Types Fan Applications Large Radial Fans Small Radial Fans Large Axial Fans Small Axial Fans Cross-Flow Fans Idealised Mean Line Analysis of a Radial Fan Idealised Flow Concept: Infinite Number of Blades Degree of Reaction Relation Between Rotor Blade Shape and Performance Parameters Performance Characteristics with Idealised Flow

3 Contents xix 3.3 Radial Fan Analysis for Lossless Two-Dimensional Flow with Finite Number of Rotor Blades Relative Vortex in Blade Channels Velocity Difference over a Rotating Blade Slip: Reduction of Rotor Work Number of Blades and Solidity: Pfleiderer Moment Coefficient Number of Blades: Examples Internal Losses with Radial Fans Turning Loss at Rotor Entrance Incidence Loss at Rotor Entrance Displacement by Blade Thickness Rotor Friction Loss and Rotor Diffusion Loss Dump Diffusion Loss at Volute Entrance Incidence Loss at Volute Entrance Friction Loss Within the Volute Diffusion at the Rotor Inlet Flow separation at Rotor Inlet and Rotor Outlet Applicability of the Loss Models Optimisation of the Rotor Inlet of a Centrifugal Fan Characteristics Taking Losses into Account Overall Performance Evaluation Mechanical Loss Leakage Loss Overall Efficiency with Power Receiving Machines Overall Efficiency with Power Delivering Machines Rotor Shape Choices with Radial Fans Axial and Mixed-Flow Fans Degree of Reaction with Axial Fans Free Vortex and Non-Free Vortex Types Axial Fan Characteristics; Adjustable Rotor Blades Mixed-Flow Fans Exercises Centrifugal Pump (Idealised Flow) Rotor of a Centrifugal Fan (Finite Number of Blades and Internal Losses) Number of Blades of a Rotor of a Centrifugal Fan Volute of a Centrifugal Fan Leakage Flow Rate with Centrifugal Fan Centrifugal Pump (Finite Number of Blades and Internal Losses) Axial Fan (Idealised Flow): Analysis on Average Diameter Axial Fan (Idealised Flow): Free Vortex and Non- Free Vortex

4 xx Contents Inlet Guide Vane with a Centrifugal Fan Change of Rotational Speed with Centrifugal and Axial Fans Two-Stage Axial Fan Axial Turbine References Compressible Fluids Basic Laws Compressibility and Velocity of Sound Compressibility Effect on the Velocity-Pressure Relation Shape of a Nozzle Nozzle with Initial Velocity Nozzle with Losses: Infinitesimal Efficiency Isentropic and Polytropic Efficiencies Exercises References Performance Measurement Pressure Measurement The Metal Manometer The Pressure Transducer The Digital Manometer Calibration of Pressure Meters Temperature Measurement The Glass Thermometer The Temperature Transducer The Digital Thermometer Flow Rate Measurement Reservoir Flow Over a Weir Pressure Drop Devices Industrial Mass Flow Rate Meters Positioning of Flow Rate Meters in Ducts Torque Measurement Swinging Suspended Motor or Brake Calibrated Motor The Torque Transducer Rotational Speed Measurement Pulse Counters The Speed Transducer Electric Tachometer Laboratory Test of a Pelton Turbine Test Rig Measurements

5 Contents xxi Measurement Procedure Calculations Measurement Example Laboratory Test of a Centrifugal Fan Test Rig Measurements Measurement Procedure Calculations Measurement Example Laboratory Test of a Centrifugal Pump Test Rig Measurements Measurement Procedure Calculations Measurement Example Steam Turbines Applications of Steam Turbines Working Principles of Steam Turbines The Steam Cycle The Single Impulse Stage or Laval Stage Velocity Triangles Work and Energy Relations Stage Efficiency Definitions Blade Profile Shape Loss Representation Optimisation of Total-to-Static Efficiency The Pressure-Compounded Impulse Turbine or Rateau Turbine Principle Efficiency The Velocity-Compounded Impulse Turbine or Curtis Turbine The Reaction Turbine Degree of Reaction Efficiency Axial Inlet and Outlet Steam Turbine Construction Forms Large Steam Turbines for Power Stations Industrial Steam Turbines Blade Shaping HP and IP Blades LP Blades Exercises References

6 xxii Contents 7 Dynamic Similitude Principles of Dynamic Similitude Definition of Dynamic Similitude Dimensionless Parameter Groups Similitude Conditions Purpose of Similitude Analysis Dimensional Analysis Independent and Dependent Parameter Groups Dimensionless Parameter Groups in Turbomachines with a Constant Density Fluid Strong and Weak Similitude Conditions Characteristic Numbers of Turbomachines Definition of a Characteristic Number Specific Speed and Specific Diameter Relation Between Characteristic Numbers and Machine Shape Design Diagrams Shape of Characteristic Curves Power Specific Speed Application Example of Similitude: Variable Rotational Speed with a Pump Imperfect Similitude Effect of Reynolds Number with the Same Fluid Effect of Relative Roughness Effect of Viscosity Rotor Diameter Reduction: Impeller Trimming Reduced Scale Models Series and Parallel Connection Parallel Connection of Fans Parallel Connection of Pumps Series Connection of Fans Turbomachine Design Example: Centrifugal Fan Exercises References Pumps Cavitation Cavitation Phenomenon and Cavitation Consequences Types of Cavitation Cavitation Assessment: Cavitation Number and Required Net Positive Suction Height Optimisation of the Inlet of a Centrifugal Pump Rotor Net Positive Suction Head of the Installation Increasing the Acceptable Suction Height

7 Contents xxiii 8.2 Priming of Pumps: Self-Priming Types Side Channel Pump Peripheral Pump (regenerative pump) Self-Priming Centrifugal Pump Jet Pump Unstable Operation Component Shaping Simply and Doubly Curved Blades in Radial Rotors Mixed-Flow and Axial Pumps Pump Inlet Pump Outlet Vaneless Diffuser Rings Vaned Diffuser Rings Volute Return Channels Internal Parallel and Series Connection Of Rotors Reason for Internal Parallel or Series Connection Internal Parallel Connection of Rotors Internal Series Connection of Rotors: Multistage Pumps Constructional Aspects Rotor Stator Shaft Sealing Bearings Axial Force Balancing with Single-Stage Pumps Axial Force Balancing with Multistage Pumps Wear Rings Special Pumps Borehole Pumps High-Pressure Pumps Sealless Pumps: Circulation Pumps, Chemical Pumps Slurry Pumps Pumping of Solid Materials Vertical Submerged Pumps Partial Emission Pumps Pumps for Viscous Fluids Exercises Looking up Pump Characteristics Verification of an NPSH-Value References Hydraulic Turbines Hydraulic Energy Hydraulic Turbine Types Large Turbines (> 10 MW) Small Turbines (< 10 MW)

8 xxiv Contents 9.3 Pelton Turbines: Impulse Turbines Performance Characteristics Specific Speed Determination of the Main Dimensions Flow Rate Control and Over-Speed Protection Francis and Kaplan Turbines: Reaction Turbines Shape of the Velocity Triangles: Kinematic Parameters Optimisation of the Velocity Triangles Degree of Reaction and Speed Ratio Velocity Triangles with Varying Degree of Reaction Specific Speed and Meridional Shape of Francis Turbines Flow Rate Control with Reaction Turbines Examples (Figs. 9.16, 9.17) Bulb and Tube Turbines Reversible Pump-Turbines Exercises References Wind Turbines Wind Energy Types of Wind Energy Conversion Systems Drag Machines High-Speed Horizontal-Axis Turbines Technical Aspects of Horizontal-Axis Wind Turbines for Electricity Generation Low-Speed Horizontal-Axis Wind Turbines Vertical-Axis Wind Turbines Wind Turbine Performance Analysis Momentum Analysis (Single Streamtube Analysis) Multiple Streamtube Analysis Blade Element Analysis Adaptation to a Wind Regime References Power Gas Turbines General Concept and Components Definition of a Gas Turbine Comparison with Other Thermal Engines Example of a Power Gas Turbine Compressor Part Turbine Part Combustion Chamber Thermodynamic Modelling Isentropic Efficiency with Adiabatic Compression or Expansion Reheat Effect

9 Contents xxv Infinitesimal Efficiency; Polytropic Efficiency Thermodynamic Properties of Air and Combustion Gas Heat Capacity Representation Cooled Expansion Compression with Extraction Performance of Simple-Cycle Power Gas Turbines Idealised Simple Cycle Simple Cycle with Component Efficiencies and Different Heat Capacities of Air and Combustion Gas Simple Cycle with Component Efficiencies, Cooling and Variable Gas Properties Performance of Power Gas Turbines with Enhanced Cycles Compression with Intercooling Expansion with Reheat Recuperator Combined Gas and Steam Cycles Steam Injection References Thrust Gas Turbines Thrust Generation Screw or Propeller Reactor or Jet Engine Rocket Overview of Aircraft Gas Turbine Engines Turbojet Turboprop and Turbo-Shaft Bypass Turbojet Turbofan Prop-fan and Unducted Fan Geared Turbofan Performance Parameters of Aircraft Propulsion Systems Specific Thrust Dynamic Power Gas Power and Dynamic Efficiency Thermal Power, Thermodynamic Efficiency and Thermal Efficiency Propulsive Power and Propulsive Efficiency Overall Efficiency Rocket Generalisation for Double-Flow Engines Specific Fuel Consumption Performance of the Gas Generator and the Single-Jet Engine Analysis with Loss-Free Components Analysis with Component Losses

10 xxvi Contents 12.5 Performance of Double-Flow Engines Unmixed Flows (Double-Jet Engine: Turbofan, Turboprop) Mixed Flows (Bypass Engine) Intercooling and Recuperation Technological Aspects of the Turbofan Engine Discs and Shafts Vanes and Blades Combustion Chamber Mixer and Thrust Reverser Exercises Single-Flow Jet Engine Single-Flow Jet Engine with Post-Combustion Turbofan with Separate Flows Turbofan with Mixed Flows Optimisation of Turbine Inlet Temperature with a Turbofan Engine Helicopter Rotor Ramjet References Axial Compressors Mean Line Analysis Velocity Triangles Fundamental Equations Loss Representation Loss Coefficients Force Components Diffusion Factor and Loss Correlations Kinematic Parameters Secondary Flow: Principle Radial Variation of Flow: Principle Optimisation of a Stage Blade Shape Attainable Pressure Ratio Secondary Flow Definition of Secondary Flow Passage Vortex and Trailing Vortices Corner Vortices Horseshoe Vortex Leakage Vortex and Scraping Vortex Loss Assessment Radial Flow Variation S 1 -S 2 Decomposition Radial Equilibrium Free Vortex Blades

11 Contents xxvii Forcing of the Vortex Distribution Effect of End Wall Boundary Layers Three-dimensional Blade Design Compressor Blade Profiles Subsonic and Supercritical Cascades Transonic Cascades Supersonic Cascades and Transonic Cascades with High Inlet Mach Number Performance Characteristics and Operating Range General Shape of a Characteristic Curve Rotating Stall Choking Surge Operating Range Exercises References Radial Compressors Construction Forms and Applications Rotor Types General Shape of a Radial Compressor Comparison Between Radial and Axial Compressors Examples of Radial Compressors Kinematic Parameters Pressure Ratio Rotor Shape Number of Blades Inducer Diffusers Flow Non-homogeneity at Rotor Outlet Mixing Zone Vaneless Diffusers Vaned Diffusers Performance Characteristics Flow Instability Choking Operating Characteristics and Operating Range Exercises Velocity Variation at Constant Radius in a Rotor Variable Geometry References Axial and Radial Turbines for Gases Axial Turbines Kinematic Parameters Radial Variation of Flow Parameters

12 xxviii Contents Blade Profiles Three-dimensional Blade Design Vane and Blade Clocking Operating Characteristic of Axial Turbines Radial Turbines Shape and Functioning Kinematic Parameters Operating Characteristic of Radial Turbines Radial Turbine Applications Dimensional Analysis with Compressible Fluids Independent and Dependent Π-groups Dimensionless Compressor and Turbine Characteristics Corrected Quantities Exercises References Index

Contents. Preface... xvii

Contents. Preface... xvii Contents Preface... xvii CHAPTER 1 Idealized Flow Machines...1 1.1 Conservation Equations... 1 1.1.1 Conservation of mass... 2 1.1.2 Conservation of momentum... 3 1.1.3 Conservation of energy... 3 1.2