xviii
Contents
2.1.3 Pressure Distribution .............................................................. 51
2.1.4 Boundary Layer Separation .................................................... 52
2.1.5 Loss Mechanism Associated to Friction: Energy Dissipation 55
2.1.6 Profile Shapes ......................................................................... 58
2.1.7 Blade Rows with Low Solidity .............................................. 59
2.2 Linear Cascades ................................................................................. 60
2.2.1 Relation with the Real Machine ............................................. 60
2.2.2 Cascade Geometry ................................................................. 61
2.2.3 Flow in Lossless Cascades: Force Components ..................... 62
2.2.4 Significance of Circulation .................................................... 65
2.2.5 Flow in Lossless Cascades: Work .......................................... 67
2.2.6 Flow in Cascades with Loss: Force Components .................. 68
2.2.7 Flow in Cascades with Loss: Energy Dissipation
and Work by Drag Force ........................................................ 70
2.2.8 The Zweifel Tangential Force Coefficient ............................. 72
2.2.9 The Lieblein Diffusion Factor ................................................ 74
2.2.10 Performance Parameters of Axial Cascades ......................... 75
2.3 Channels ............................................................................................. 75
2.3.1 Straight Channels ................................................................... 75
2.3.2 Bends ...................................................................................... 77
2.4 Diffusers ............................................................................................. 79
2.4.1 Dump Diffusers ...................................................................... 79
2.4.2 Inlet Flow Distortion .............................................................. 79
2.4.3 Flow Separation ..................................................................... 81
2.4.4 Flow Improvement ................................................................. 81
2.4.5 Representation of Diffuser Performance ................................ 82
2.4.6 Equivalent Opening Angle ..................................................... 84
2.4.7 Diffusion in a Bend ................................................................ 85
2.5 Exercises ............................................................................................ 87
References ................................................................................................... 95
3 Fans ............................................................................................................ 97
3.1 Fan Aplications and Fan Types .......................................................... 97
3.1.1 Fan Applications ..................................................................... 97
3.1.2 Large Radial Fans .................................................................. 98
3.1.3 Small Radial Fans .................................................................. 99
3.1.4 Large Axial Fans .................................................................... 99
3.1.5 Small Axial Fans .................................................................... 100
3.1.6 Cross-Flow Fans ..................................................................... 100
3.2 Idealised Mean Line Analysis of a Radial Fan ................................... 101
3.2.1 Idealised Flow Concept: Infinite Number of Blades .............. 101
3.2.2 Degree of Reaction ................................................................. 102
3.2.3 Relation Between Rotor Blade Shape and Performance Parameters ................................................................... 103
3.2.4 Performance Characteristics with Idealised Flow .................. 105
Contents
2.1.3 Pressure Distribution .............................................................. 51
2.1.4 Boundary Layer Separation .................................................... 52
2.1.5 Loss Mechanism Associated to Friction: Energy Dissipation 55
2.1.6 Profile Shapes ......................................................................... 58
2.1.7 Blade Rows with Low Solidity .............................................. 59
2.2 Linear Cascades ................................................................................. 60
2.2.1 Relation with the Real Machine ............................................. 60
2.2.2 Cascade Geometry ................................................................. 61
2.2.3 Flow in Lossless Cascades: Force Components ..................... 62
2.2.4 Significance of Circulation .................................................... 65
2.2.5 Flow in Lossless Cascades: Work .......................................... 67
2.2.6 Flow in Cascades with Loss: Force Components .................. 68
2.2.7 Flow in Cascades with Loss: Energy Dissipation
and Work by Drag Force ........................................................ 70
2.2.8 The Zweifel Tangential Force Coefficient ............................. 72
2.2.9 The Lieblein Diffusion Factor ................................................ 74
2.2.10 Performance Parameters of Axial Cascades ......................... 75
2.3 Channels ............................................................................................. 75
2.3.1 Straight Channels ................................................................... 75
2.3.2 Bends ...................................................................................... 77
2.4 Diffusers ............................................................................................. 79
2.4.1 Dump Diffusers ...................................................................... 79
2.4.2 Inlet Flow Distortion .............................................................. 79
2.4.3 Flow Separation ..................................................................... 81
2.4.4 Flow Improvement ................................................................. 81
2.4.5 Representation of Diffuser Performance ................................ 82
2.4.6 Equivalent Opening Angle ..................................................... 84
2.4.7 Diffusion in a Bend ................................................................ 85
2.5 Exercises ............................................................................................ 87
References ................................................................................................... 95
3 Fans ............................................................................................................ 97
3.1 Fan Aplications and Fan Types .......................................................... 97
3.1.1 Fan Applications ..................................................................... 97
3.1.2 Large Radial Fans .................................................................. 98
3.1.3 Small Radial Fans .................................................................. 99
3.1.4 Large Axial Fans .................................................................... 99
3.1.5 Small Axial Fans .................................................................... 100
3.1.6 Cross-Flow Fans ..................................................................... 100
3.2 Idealised Mean Line Analysis of a Radial Fan ................................... 101
3.2.1 Idealised Flow Concept: Infinite Number of Blades .............. 101
3.2.2 Degree of Reaction ................................................................. 102
3.2.3 Relation Between Rotor Blade Shape and Performance Parameters ................................................................... 103
3.2.4 Performance Characteristics with Idealised Flow .................. 105