CRANFIELD UNIVERSITY MICHAEL J SEFAIN HYDROGEN AIRCRAFT CONCEPTS & GROUND SUPPORT SCHOOL OF ENGINEERING PhD CRANFIELD UNIVERSITY SCHOOL OF ENGINEERING Aerospace Vehicle Design PhD THESIS Academic Year 2000 MICHAEL J SEFAIN HYDROGEN AIRCRAFT CONCEPTS & GROUND SUPPORT Supervisor: Dr. R. I. Jones November 2005 ©Cranfield University, 2006. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. 2 ABSTRACT As worldwide petroleum supplies diminish and prices escalate, the aviation industry will be forced to consider relying on energy resources other than kerosene for its aviation fuel needs. Additionally, there is growing environmental concern regarding greenhouse emissions particularly as aircraft cause pollution in sensitive layers of the atmosphere. These are serious implications necessitating prudence in seeking alternative fuels sooner rather than later. Liquid Hydrogen (LH2) combustion produces zero CO2 emissions, very little NOx, and water providing a solution to sustain air traffic growth whilst preventing further atmospheric pollution. Hydrogen itself is abundant and can be produced from renewable sources meaning worldwide availability and sustainability permitting sustainable growth of aviation at high rates (typically 4-5% per year). Despite these major advantages, there are compromises to be made. The low density fuel means ingenuity must be exercised to design an aircraft configuration which will accommodate a fuel volume more than four times that which would normally be required. Practical unconventional aircraft conceptual designs providing solutions to this problem are presented including estimates of performance, mass, and relative cost- and energy-effectiveness. To provide a means to produce, store and transport the fuel safely and efficiently, ground support operations have been systematically checked and the required airport infrastructure defined. Technical issues such as safety, airworthiness certification, environmental issues and system synergies are also discussed, and an outline plan is presented providing the R&D necessary to introduce LH2-fuelled civil aircraft into service. This Thesis proves that LH2 has sufficient long term promise to justify more substantial R&D offering possible improvement in performance and engine 3 reliability. The overall cost for a LH2 aircraft are within reasonable values, and the requirement for new equipment to maintain and support LH2-fuelled aircraft is not extensive. Importantly LH2 is at least as safe. 4 Acknowledgements I am indebted to my supervisor Dr. Robert Jones who provided me with excellent support, advice, suggestions and invaluable information on a continuous basis throughout and without whom, this study would not have been possible. I would also like to express my sincere appreciation to Professor J.P. Fielding, and Professor D Howe who also took a lot of time out of their very busy schedules to contribute to this work providing me with invaluable advice that only years of experience and expertise could have provided. I would also like to express my gratitude to the staff and students at the College of Aeronautics (now part of the School of Engineering) for their continual support. I also acknowledge the support given to me by my family and friends who have provided an endless source of encouragement. Above all my thanks must go to God without Whom nothing is possible. 5 CONTENTS ABSTRACT ............................................................................................................... 3 Acknowledgements .................................................................................................... 5 CONTENTS............................................................................................................... 6 List of Figures .......................................................................................................... 10 List of Tables............................................................................................................ 13 ABBREVIATIONS/NOMENCLATURE ............................................................... 17 Preface...................................................................................................................... 23 1.0 SCOPE OF THESIS..................................................................................... 24 1.1 Thesis Chapter Content .........................................................................24 2.0 HYDROGEN FUEL..................................................................................... 26 2.1 Introduction...........................................................................................26 2.2 Background...........................................................................................26 2.2.1 Renewable Energy.............................................................................26 2.2.2 Environmental and Greenhouse Effect...............................................27 2.2.3 Candidate fuels..................................................................................29 2.2.4 Characteristics of Hydrogen fuel .......................................................30 2.2.4.1 Advantages of hydrogen.................................................................33 2.2.4.2 Disadvantages of hydrogen............................................................34 2.2.4.3 Summary of LH2 characteristics and effects on aircraft design.......35 2.3 Objectives .............................................................................................37 3.0 UNCONVENTIONAL AIRCRAFT DESIGN ............................................ 40 3.1 Development of passenger jet configurations – Challenges faced by designers ..........................................................................................................40 3.2 What drives a unique configuration?.....................................................41 3.2.1 Very Large Aircraft .......................................................................42 3.2.2 Multi-Body Concept.......................................................................43 3.2.3 Oblique wing .................................................................................46 3.2.4 Transonic biplane..........................................................................47 3.2.5 Joined Wing...................................................................................49 3.2.6 Multirole Global Range Transport.................................................50 3.2.7 Forward Swept Wing and application in high aspect ratio aircraft configurations...............................................................................................51 3.3 Aircraft Configuration Design...............................................................51 3.3.1 Brainstorming................................................................................52 3.3.2 Results of Brainstorming Session – Configurations........................55 3.3.3 Configuration assessment ..............................................................63 3.3.4 Design attributes ...........................................................................64 3.3.5 Final concepts ...............................................................................66 6 3.4 Conceptual Design ................................................................................69 3.4.1 Medium-Range Aircraft Specification (JAR/FAR 25) ....................69 3.4.2 Twin-Boom Conceptual design......................................................72 3.5 Results................................................................................................. 122 3.6 Configuration description....................................................................131 3.6.1 Fuselage Layout ..........................................................................131 3.6.2 Wing and Tail layout ...................................................................132 3.6.3 Mass and balance........................................................................134 3.6.4 Lift and Drag...............................................................................137 3.6.5 Powerplant and Installation.........................................................138 3.6.6 Performance................................................................................139 3.6.7 Fuel Tank Structure .....................................................................139 3.6.8 LH2-fuel tank pylon structure (twin boom) ...................................143 3.6.9 Safety...........................................................................................144 4.0 HYDROGEN SAFETY.............................................................................. 146 4.1 Characteristics of Liquid Hydrogen.....................................................147 4.2 Risks related to low temperatures ........................................................148 4.3 Phenomena associated with combustion ..............................................149 4.3.1 Danger zones of spilled liquid gases ............................................149 4.4 Specific hydrogen hazards...................................................................150 4.5 Infrastructure-specific safety aspects...................................................152 4.5.1 Hydrogen production methods .....................................................152 4.5.2 Hydrogen liquefaction ................................................................. 152 4.5.3