Fans: Aerodynamic Design - Noise Reduction - Optimization

✍ Scribed by Thomas Carolus

• Publisher: Springer Vieweg
• Year: 2023
• Tongue: English
• Leaves: 263
• Category: Library

✦ Synopsis

This textbook combines in a unique concept the design and construction of radial and axial fans with the problem of noise generation as well as its mitigation already in the fan development stage. The aim is to describe selected, easily applicable methods of aerodynamic design and noise prediction and to demonstrate their physical principles. Exercises with solutions facilitate understanding. The completely revised and expanded edition now also includes guidance on selecting fans for a given task, simulation-based optimization methods for fan design, and psychoacoustic methods that can be used to measure the quality of fan noise.

This book is a translation of the original German 4^th edition Ventilatoren by Thomas Carolus, published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2020. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com). A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors.

✦ Table of Contents

Preface
Acknowledgements
Contents
List of Symbols (Selection)
Subscripts
Subscripts
Abbreviations
1: Basics
1.1 Fan Performance Parameters
1.2 Selection of the Fan: Demand of the Plant
1.3 Aerodynamic Performance Characteristics
1.4 Non-dimensional Parameters, Model Laws, Types of Fans
1.4.1 Non-dimensional Parameters
1.4.2 Model Laws
1.4.3 Scale-Up Methods
1.4.4 Systematics of Fan Types: The Cordier-Diagram
1.5 Practice Problems
1.5.1 Pressure Rise Requirement of a Plant and Fan Specification
1.5.2 Selection of the Type of Fan
1.5.3 From Model- to Full-Scale
References
2: Blade Performance Parameters, Cascades of Blades, Kinematics, Losses and Efficiencies
2.1 Blade Work, Blade Volume Flow Rate
2.2 Flow Kinematics (Velocity Triangles)
2.2.1 Cascade of Radial Blades
2.2.2 Cascade of Axial Blades
2.3 Losses and Efficiencies
2.3.1 Losses in the Impeller and Efficiencies
2.3.2 Losses in the Casing and Guide Vanes, Efficiencies
References
3: Design of Centrifugal Fans
3.1 Blade Design
3.1.1 Slip of Flow
3.1.2 The Slip Factor
3.1.3 Selection of the Number of Blades
3.1.4 Blockage of the Inlet and Outlet Due to the Finite Thickness of the Blade
3.1.5 Summary: Blade Design for Centrifugal Impellers
3.1.6 Further Empirical Geometry Parameters of the Centrifugal Impeller
3.2 Layout of a Volute Casing
3.2.1 One-Dimensional Streamline Theory
3.2.2 Further Empirical Geometrical Parameters of the Simple Volute Casing
3.3 Practice Problems
3.3.1 Design of a Centrifugal Fan Impeller
3.3.2 Design of a Volute
References
4: Design of Axial Fans
4.1 Flow Kinematics in the Axial Impeller: Radial Equilibrium
4.1.1 Isoenergetic Loading Distribution
4.1.2 Radius-Dependent Loading Distribution
4.1.3 Summary of Swirl Distributions
4.2 Segmentation
4.3 The Blade Element Momentum (BEM) Method for Low-Pressure Axial Fans
4.3.1 Derivation of the Key Equation
4.3.2 Summary: Blade Design for Low-Solidity Axial Impellers with the BEM Method
4.3.3 Blade Skew
4.4 The Lieblein Method for High-Pressure Axial Fans
4.4.1 Blade Element Inlet Angle
4.4.2 Blade Exit Angle
4.4.3 Camber and Mean Line
4.4.4 Summary: Blade Design for High-Solidity Axial Impellers
4.5 Design Criteria
4.5.1 De Haller-Criterion
4.5.2 Criterion of Strscheletzky
4.5.3 Diffusion Coefficient According to Lieblein
4.5.4 Further Limitations
4.6 Practice Problems
4.6.1 Design of a Low-Pressure Axial Fan
4.6.2 Design of High-Pressure Axial Fan Stage
References
Further Reading
5: Sound Generation and Propagation
5.1 The Mechanisms of Sound Generation: An Overview
5.2 Rotating Pressure Fields of Axial Fans
5.2.1 The Rotating Pressure Field of an Isolated Impeller
5.2.2 Rotor-Stator Interaction
5.3 Flow-Induced Sound from Lift-Generating Surfaces
5.4 Sound Propagation
5.4.1 Radiation into the Free Field
5.4.2 Sound Propagation in Ducts: Duct Modes
5.4.3 Excitation of Duct Modes by a Fan
5.5 Significance of Sound Sources and Examples
5.5.1 Rotor-Stator Interaction
5.5.2 Turbulent Inflow, Stall
5.5.3 Vortex Shedding
5.5.4 Tip Clearance Noise
5.6 Practice Problems
References
6: Sound Prediction Methods
6.1 Overview
6.2 Class I Sound Prediction Methods
6.2.1 Formula of Madison
6.2.2 Regenscheit´s Approach
6.2.3 Estimation of the Octave Band Sound Power Level
6.3 Class II Sound Prediction Methods
6.3.1 The Sharland Method
6.3.2 Spectral Distribution
6.3.3 Duct Model
6.3.4 Summary and Example
6.4 Practice Problems
6.4.1 Acoustic Model Law
6.4.2 Fan Acoustic Power
References
Further Reading
Sound in Turbomachinery in General
Acoustic Model Laws for Fans
Inflow Turbulence
Trailing Edge Sound
7: Psychoacoustic Assessment of Fan Noise
7.1 Introduction
7.2 Perception of Annoyance and Quality of Fan Sound
7.3 Two Psychoacoustic Metrics for Fan Noise
7.4 Examples
References
8: Design Features of Noise Reduced Fans
8.1 General Measures
8.1.1 Reduction of the Circumferential Speed
8.1.2 Increasing the Spacing Between Stationary and Rotating Components
8.1.3 Phase Shift of the Interaction Between Stationary and Rotating Components
8.1.4 Uneven Blade Spacing
8.1.5 Wavy Leading Edge and Serrated Trailing Edge
8.1.6 Optimum Inlet Geometry and Turbulence Control Screen
8.2 Further Special Measures for Centrifugal Fans
8.2.1 Meridional Contour of Shroud
8.2.2 Suppression of Resonance
8.3 Further Special Measures for Axial Fans
8.3.1 Tuning the Number of Blades (Mode Propagation)
8.3.2 Skewed Blades
8.3.3 Influencing the Tip Gap Flow
References
9: Numerical and Experimental Methods
9.1 Numerical Flow Field Simulation
9.1.1 Overview of CFD Methods
9.1.2 Computational Domain and Numerical Grid
9.1.3 Boundary and Initial Conditions
9.1.4 The Rotor-Stator Problem
9.1.5 Control Parameters, Convergence, Residuals and Termination of Iteration
9.1.6 Post Processing
9.1.7 Validation and Verification
9.1.8 Example: Axial Fan
9.2 Experimental Methods
9.2.1 Fan Test Rigs
9.2.2 Measurement of Flow Field Quantities: Measuring Probes
9.2.3 Measurement of Acoustic Quantities
9.3 Optimization
9.3.1 Optimization Procedures
9.3.2 Example: Optimization of an Axial Fan
9.3.3 Example: Centrifugal Fan Impellers with Maximum Total-to-Static Efficiency
References
Further Reading
10: Appendix
10.1 Effective Pressure Rise
10.1.1 Centrifugal Impeller
10.1.2 Axial Impeller
10.1.3 Axial Impeller with Outlet Guide Vanes and Diffuser
10.2 Airfoil Sections
10.2.1 Isolated Airfoil Section in Unbounded Flow
10.2.2 Airfoil Families
10.2.3 Airfoil Sections in a Cascade
10.3 Some Basics of Acoustics
10.4 Tables
10.5 Lieblein Design Diagrams
References
11: Answers to Practice Problems
11.1 Answer to Problem 1.5.1: Pressure Rise Requirement of a Plant and Fan Specification
11.2 Answer to Problem 1.5.2: Selection of the Type of Fan
11.3 Answer to Problem 1.5.3: From Model- to Full-Scale
11.4 Answer to Problem 3.3.1: Design of a Centrifugal Fan Impeller
11.5 Answer to Problem 3.3.2: Design of a Volute
11.6 Answer to Problem 4.6.1: Design of Low-Pressure Axial Fan
11.7 Answer to Problem 4.6.2: Design of High-Pressure Axial Fan Stage
11.8 Answer to Problem 5.6: Axial Fan - Acoustic Modes
11.9 Answer to Problem 6.4.1: Acoustic Model Law
11.10 Answer to Problem 6.4.2: Fan Acoustic Power
References
Index