Aerospace propulsion devices embody some of the most advanced technologies, ranging from materials, fluid control, and heat transfer and combustion. In order to maximize the performance, sophisticated testing and computer simulation tools are developed and used.
Aerospace Propulsion comprehensively covers the mechanics and thermal-fluid aspects of aerospace propulsion, starting from the fundamental principles, and covering applications to gas-turbine and space propulsion (rocket) systems. It presents modern analytical methods using MATLAB and other advanced software and includes essential elements of both gas-turbine and rocket propulsion systems. Gas turbine coverage includes thermodynamic analysis, turbine components, diffusers, compressors, turbines, nozzles, compressor-turbine matching, combustors and afterburners. Rocket coverage includes chemical rockets, electrical rockets, nuclear and solar sail.
Key features:
- Both gas-turbine and rocket propulsion covered in a single volume
- Presents modern analytical methods and examples
- Combines fundamentals and applications, including space applications
- Accompanied by a website containing MATLAB examples, problem sets and solutions
Aerospace Propulsion is a comprehensive textbook for senior undergraduate graduate and aerospace propulsion courses, and is also an excellent reference for researchers and practicing engineers working in this area.
Table of Contents
Contents – Aerospace Propulsion
Series Preface ix
Preface xi
1 Introduction to Propulsion Systems 1
1.1 Conservation of Momentum 7
1.2 Conservation of Energy (the First Law of Thermodynamics)
and Other Thermodynamic Relationships 10
1.3 One-Dimensional Gas Dynamics 13
1.4 Heat Transfer 14
1.5 Standard Atmospheric Air Properties 15
1.6 Unit Conversion 17
1.7 Problems 20
Bibliography 20
2 Principle of Thrust 21
2.1 Thrust Configurations 21
2.2 Thrust Equation 23
2.3 Basic Engine Performance Parameters 28
2.4 Propulsion and Aircraft Performance 34
2.5 Propeller Propulsion 38
2.6 MATLAB1 Program 39
2.7 Problems 40
Bibliography 42
3 Basic Analyses of Gas-Turbine Engines 43
3.1 Introduction 43
3.2 Gas-Turbine Engine as a Power Cycle (Brayton Cycle) 43
3.3 Ideal-Cycle Analysis for Turbofan Engines 49
3.4 Turbojets, Afterburners and Ramjets 61
3.4.1 Turbojet 61
3.4.2 Turbojets with Afterburners 64
3.4.3 Turbofan Engines with Afterburning (Mixed Stream) 68
3.4.4 Ramjets 70
3.5 Further Uses of Basic Engine Analysis 73
3.6 MATLAB1 Program 76
3.7 Problems 77
Bibliography 79
4 Gas-Turbine Components: Inlets and Nozzles 81
4.1 Gas-Turbine Inlets 81
4.2 Subsonic Diffuser Operation 82
4.3 Supersonic Inlet Operation 91
4.4 Gas-Turbine Nozzles 95
4.5 Problems 98
Bibliography 99
5 Compressors and Turbines 101
5.1 Introduction 101
5.2 Basic Compressor Aero-Thermodynamics 103
5.2.1 Compressor Stage Performance 107
5.2.2 Pressure Coefficient and Boundary Layer Separation 109
5.2.3 de Haller Number and the Diffusion Factor 110
5.2.4 Mach Number Effect 111
5.2.5 Degree of Reaction 112
5.3 Radial Variations in Compressors 115
5.3.1 Stage Work and Degree of Reaction for Free-Vortex Swirl
Distribution 118
5.4 Preliminary Compressor Analysis/Design 119
5.5 Centrifugal Compressors 120
5.6 Turbine 123
5.6.1 Estimation of the Blade Stagnation Temperature 126
5.6.2 Turbine Blade and Disk Stresses 128
5.7 MATLAB1 Programs 129
5.8 Problems 131
Bibliography 133
6 Combustors and Afterburners 135
6.1 Combustion Chambers 135
6.2 Jet Fuels and Heating Values 137
6.3 Fluid Mixing in the Combustor 141
6.4 Afterburners 149
6.5 Combustor Heat Transfer 152
6.6 Stagnation Pressure Loss in Combustors 153
6.7 Problems 155
Bibliography 157
7 Gas-Turbine Analysis with Efficiency Terms 159
7.1 Introduction 159
7.2 Turbofan Engine Analysis with Efficiency Terms 160
7.2.1 Polytropic Factor 162
7.2.2 Diffuser 164
7.2.3 Compressor and Fan 164
7.2.4 Combustor 165
7.2.5 Turbine Power Balance 165
7.2.6 Nozzle Exit Pressure 165
7.2.7 Output Parameters 166
7.3 MATLAB1 Program 172
7.4 Problems 174
Bibliography 175
8 Basics of Rocket Propulsion 177
8.1 Introduction 177
8.2 Basic Rocketry 182
8.2.1 Specific Impulse 182
8.2.2 Vehicle Acceleration 183
8.2.3 Staging 184
8.2.4 Propulsion and Overall Efficiencies 188
8.3 MATLAB1 Programs 189
8.4 Problems 190
Bibliography 191
9 Rocket Propulsion and Mission Analysis 193
9.1 Introduction 193
9.2 Trajectory Calculations 195
9.3 Rocket Maneuvers 203
9.3.1 Coplanar Orbit Change 205
9.3.2 Hohmann Transfer 206
9.3.3 Plane Change 207
9.3.4 Attitude Adjustments 208
9.4 Missile Pursuit Algorithms and Thrust Requirements 209
9.4.1 Velocity Pursuit 210
9.4.2 Proportional Navigation 211
9.4.3 Command-to-Line-of-Sight (CLOS) 212
9.5 Problems 213
Bibliography 215
10 Chemical Rockets 217
10.1 Rocket Thrust 217
10.1.1 Ideal Rocket Thrust 217
10.1.2 Thrust Coefficient and Characteristic Velocity 218
10.2 Liquid Propellant Rocket Engines 220
10.2.1 Liquid Propellants and Their Chemistry 222
10.2.2 Chemical Equilibrium 225
10.2.3 Liquid Propellants Combustion Chambers 232
10.3 Solid Propellant Combustion 244
Contents vii
10.3.1 Burning Rate Analysis 247
10.4 Rocket Nozzles 252
10.4.1 Thrust Vector Control 254
10.4.2 Nozzle and Combustion Chamber Heat Transfer 254
10.5 MATLAB1 Program 256
10.6 Problems 256
Bibliography 258
11 Non-Chemical Rockets 259
11.1 Electrothermal Devices 261
11.2 Ion Thrusters 265
11.2.1 Ion Generation 266
11.2.2 Acceleration of Ions 271
11.2.3 Electromagnetic Thrusters 275
11.3 Problems 280
Bibliography 282
Appendices 283
Appendix A: Standard Atmospheric Air Properties 283
Appendix B: Specific Heats for Air as a Function of Temperature 286
Appendix C: Normal Shock Properties 287
Appendix D: Oblique Shock Angle Chart 291
Appendix E: Polynomial Coefficients for Specific Heat of Selected Gases 292
Appendix F: Standard state Gibbs free energy (T = 298.15K, P = 1 atm)
Index 295
Series Preface – Aerospace Propulsion
There are books in the Aerospace Series that deal with propulsion systems for aircraft. They
generally treat the engine and its control system as an integral part of the aircraft – as an
installed system. The interactions between the propulsion system and the aircraft systems are
described.
The power plant of an airborne vehicle is critical to its performance and its safe operation,
so it is vital for engineers working in this field to understand the fundamentals of the
propulsion system. This book provides a different viewpoint to that of the systems books: it is
very much an analytical view of the power plant itself, and it should be read as a complement
to the other propulsion books. The author introduces the reader to the principles of thrust and
the gas turbine engine before providing a comprehensive mathematical treatment of the major
components of the propulsion mechanism and the complex aerodynamic and thermodynamic
processes within various engine types – both air-breathing and rocket. This is to provide a
basis for developing an understanding of propulsion systems and the modeling tools that can
be used to provide a comprehensive and practical knowledge for use in research and industry.
MATLAB1models are provided to reinforce the explanations, and exercises are also set for
the diligent student to pursue.
The book covers gas turbine (aeronautical) systems and rocket propulsion (astronautic)
systems and is hence of interest to engineers working in the fields of aircraft, missiles and
space vehicles. Some novel propulsion systems are also described, that may be pertinent to
emerging fields of aerospace transportation systems, setting out to meet environmental
objectives.
This is a book for those engineers who wish to understand the fundamental principles of
aerospace propulsion systems.
Peter Belobaba, Jonathan Cooper and Allan Seabridge
Introduction to Propulsion Systems
Propulsion systems include some of the most advanced technologies. The high performance requirements, at low system weight, necessitate advanced thermal-fluid design, materials and system integration.
The thrust, generated through a simple-looking principle of conservation of momentum (or Newton’s second law), enables many human capabilities, such as high-speed civil transport (approximately 12 hours for trans-Pacific flights), affordable personal aircraft, advanced military aircrafts (e.g. F-22 Raptor, Sukhoi), Earth orbital operations (Space Shuttle) and numerous satellites, planetary probes and possible missions.
The propulsion technology can also lead to potentially destructive uses, as in cruise missiles, intercontinental ballistic missiles and many other weapons propelled at high speeds. A typical gas-engine shown in Figure 1.1 achieves the high exit momentum through a sequence of devices that include compressor, combustor, turbine and nozzle.
The ambient air is ingested in gas-turbine engines. The compressor consists of a series of rotating blades, which aerodynamically is a set of airfoils using rotary motion to generate a pressure differential as the air traverses the blade elements. The air pressure is increased in the compressor, and sent into the combustor where the fuel is injected, mixed with the air, and burned. The air energy (enthalpy) increase is now used in the turbines to convert some of the thermal energy (enthalpy) into shaft power.
This shaft power is used to power the compressor, by simply having a common axis between the turbine and the compressor in turbojet engines. However, in turbofan engines, the turbine power is used to run both the compressor and the fan. The fan adds enthalpy to the air stream in the fan section. The energy available at the end of the turbine section is converted to air kinetic energy in the nozzle. The high kinetic energy of the exhaust stream also has high momentum, which is useful in generating thrust.
Ramjets are a much simpler form of turbojet engines, where “ram compression” of incoming stream at supersonic speeds is sufficient to elevate the pressure of the air. Fuel then needs to be injected into this high-pressure air stream and the resulting flame stabilized in the ramjet combustor, for sustained thrust.
Advances in practically all aspect of engineering, including propulsion technology, can be found in the Lockheed Martin F-22 Raptor (Figure 1.2) that entered service in 2005. New materials such as advanced alloys and composite materials are used in the Raptor airframe, aerodynamic surfaces and engine components.
The power plant in the F-22 consists of Pratt-Whitney afterburning turbofans (F119-PW-100) with a high efficiency, which provide supersonic cruise speeds with long range and unmatched agility with pitch-vectoring thrust nozzles. But these technological advances came with a high price tag. Many of the new technologies were researched and developed specifically as part of the F-22 project. If all the development costs are added in, the F-22 carries a price tag of over $300 million per aircraft. Table 1.1 shows some of the main specifications of the F-22, including some of the propulsion characteristics. The Pratt-Whitney F119-PW-100 engine is another component in the F-22 that is arguably the most advanced in aircraft technology
Preface – Aerospace Propulsion
Aerospace propulsion devices embody some of the most advanced technologies, ranging from
materials, fluid control and heat transfer and combustion. In order to maximize performance,
sophisticated testing and computer simulation tools are developed and used. In undergraduate
or introductory graduate courses in aerospace propulsion, we only cover the basic elements of
fluid mechanics, thermodynamics, heat transfer and combustion science, so that either in
industry or in research labs the students/engineers can address some of the modern design and
development aspects.
Compressor aerodynamics, for example, is a dynamic process involving rotating blades that
see different flows at different radial and axial locations. Cascade and transonic flow behavior
can make the analyses more complex and interesting. In turbine flows, the gas temperature is
high, and thus various material and heat transfer issues become quite important. Owing to the
rotating nature of turbine and compressor fluids, intricate flow control between the axis and
the blade section needs to be used, while allowing for cooling flow passage from the
compressor to the turbine blades. Combustor flow is even more complex, since liquid-phase
fuel needs to be sprayed, atomized, evaporated and burned in a compact volume. High heat
release and requirements for downstream dilution and cooling again make the flow design
quite difficult and challenging.
All of these processes – spray atomization, phase change, combustion, heat transfer (convection and radiation) and mixing – occur in turbulent flows, and no computational tools can accurately reproduce real flows without lengthy modeling and calibration. Any one of the issues mentioned above, such as spray atomization, turbulent flow
or combustion, is an unsolved problem in science and engineering, and this is the reason for
industry and research labs developing expensive testing and computational analysis methods.
This aspect makes aerospace propulsion an important part of engineering curricula, as it
provides an interdisciplinary and “tough” training ground for aerospace engineers.
As noted above, owing to the multiple engineering topics involved, we only go into basic
elements of aerospace propulsion. After some of the basics are covered, we try to expose the
students to projects involving computational fluid dynamic (CFD) software, since this is
frequently used in industry and in research labs. There are commercial CFD packages that can
be readily made available to the students, using educational licenses. With online documentation
and examples, students can learn to operate these codes, individually or in group
projects. In addition, the gas-turbine lab at ASU allows the students to use actual testing data
for performance analyses. These elements cannot be included in this book without stretching
the physical and mental limits, but they are essential components in an aerospace propulsion
course, to link the underlying science and engineering to practical applications.
I have included discussions of both gas-turbine and rocket propulsion, for combined or
separate aerospace propulsion courses. There are some good interrelations between aeronautical
(gas-turbine) and astronautical (rocket) propulsion, based on the same knowledge set. In
addition, many students opt to take both aeronautical and astronautical propulsion, unless a
combined course is offered, since their final career choices are made many years downstream.
Thank you for reading up to this point, and potentially beyond.
About the Author – Aerospace Propulsion
T.W. Lee, Arizona State University, USA
T.W. Lee is currently an Associate Professor in the Mechanical and Aerospace Engineering department at Arizona State University. He has been teaching an Aerospace Propulsion class for the last 15 years and is the author of two books. His research interests include combustion, thermal-fluids, and propulsion systems and current projects include hypersonic inlets and supersonic reactors.
