Page 7 - Fluid Mechanics and Thermodynamics of Turbomachinery

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vi Contents
3. Two-dimensional Cascades 55

Introduction 55
Cascade nomenclature 56
Analysis of cascade forces 57
Energy losses 59
Lift and drag 59
Circulation and lift 61
Efﬁciency of a compressor cascade 62
Performance of two-dimensional cascades 63
The cascade wind tunnel 63
Cascade test results 65
Compressor cascade performance 68
Turbine cascade performance 70
Compressor cascade correlations 71
Fan blade design (McKenzie) 80
Turbine cascade correlation (Ainley) 81
Comparison of the proﬁle loss in a cascade and in a turbine stage 86
Optimum space-chord ratio of turbine blades (Zweifel) 87
References 88
Problems 90
4. Axial-ﬂow Turbines: Two-dimensional Theory 93

Introduction 93
Velocity diagrams of the axial turbine stage 93
Thermodynamics of the axial turbine stage 94
Stage losses and efﬁciency 96
Soderberg’s correlation 97
Types of axial turbine design 99
Stage reaction 101
Diffusion within blade rows 103
Choice of reaction and effect on efﬁciency 107
Design point efﬁciency of a turbine stage 108
Maximum total-to-static efﬁciency of a reversible turbine stage 112
Stresses in turbine rotor blades 114
Turbine ﬂow characteristics 120
Flow characteristics of a multistage turbine 122
The Wells turbine 124
References 132
Problems 133

5. Axial-ﬂow Compressors and Fans 137
Introduction 137
Two-dimensional analysis of the compressor stage 138
Velocity diagrams of the compressor stage 140
Thermodynamics of the compressor stage 141

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