Design and Analysis of the Control and Stability of a Blended Wing Body Aircraft

210 Pages·2014·24.24 MB·English

by  Roberto Merino Martínez

Design and Analysis of the Control
and Stability of a Blended Wing
Body Aircraft
Roberto Merino Martínez

Supervisor: Arthur Rizzi

Royal Institute of Technology (KTH)

Stockholm, Sweden

May 2014

Abstract
Futureaircraftgenerationsarerequiredtohavehigherperformanceandcapacities.
This achievement should be fulfilled with the minimum cost and environmental
impact. Thiscallsforthedesignofnewunconventionalconfigurations, suchasthe
Blended Wing Body (BWB), a tailless aircraft which integrates the wing and the
fuselage into a single lifting surface. It has been proven in previously published
works that this concept is feasible, has an efficient economical performance and
is a promising candidate for solving the current air traffic problems, despite its
challenging control and stability features. Moreover, the size of the vertical sur-
faces, such as the winglets, condition the radar detectability of the BWB model,
especially for military missions. The goal of the department of Aeronautical and
Vehicle Engineering at the Royal Institute of Technology (KTH) and of the de-
partment of Air Transport Systems of the German Aerospace Centre (DLR) is to
investigate new ways to improve the conceptual design process of the aircrafts in
a multidisciplinary environment. In order to design future unconventional aircraft
configurations (such as the Blended Wing Body), the CEASIOM (Computerised
Environment for Aircraft Synthesis and Integrated Optimisation Methods) geom-
etry module, AcBuilder, is replaced and enhanced by implementing the Common
Parametric Aircraft Configuration Scheme (CPACS), developed by the DLR as
a basis technology. CPACS is meant to become a unified software framework to
allow the sharing of the work and information, making it accessible for every per-
son. It requires an implementation of the software modules in a framework using
a common language for all the tools, in order to make later alterations of this
framework easier. A detailed research of the latest developments and advances
in the BWB concept was performed in order to identify the main principles and
best design options. Afterwards, by using the implemented improved tool CPAC-
SCreator (CC) based on CPACS, instead of Acbuilder, a BWB aircraft baseline
was designed. The aerodynamic behaviour and performance of this model were
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then analyzed with the aid of the improved CEASIOM platform, with an special
emphasis on its control and stability features. This analysis enables to improve
the baseline design and the allocation and size of the control surfaces was studied
and optimized. The minimum winglet required for a target flight performance was
identified, due to its importance for reducing the drag and the radar detectability
of the aircraft.
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Preface
This Master Thesis was accomplished during my Erasmus course at the Royal
Institute of Technology (KTH) in Stockholm. This experience was definetely
enriching and helped me to complement my studies at the Technical University
of Madrid (UPM), in the “Escuela Técnica Superior de Ingenieros Aeronáuticos”.
First of all I would like to address special thanks to my supervisor Professor
Arthur Rizzi for giving me the opportunity to carry out my Master Thesis in his
department and for his patience and all his support and helpful discussions. I
would also like to kindly thank Professor Jesper Oppelstrup for his helpful advice
and interesting conversations. Moreover, I am very thankful to Mengmeng, Mio
and Cong, also from the department of Aeronautical and Vehicle Engineering at
KTH, for their help and useful discussions.
I would like to express my sincere gratitude to my family, especially to my
parents and to my brother, who where always there to encourage me and making
everything easier to me. Without them this work would not have been possible.
Last but not least, I would like to acknowledge the presence of all the wonder-
ful people I have met this year in Sweden, specially my girlfriend Lenka, whose
understanding and motivation were very important for me.
Email of the author: [email protected]
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Contents
1 Introduction 1
1.1 Motivation for this work . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Crucial and distinguishing aspects of the BWB configuration . . . 3
1.3 Aircraft design process . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 A new design solution . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Objectives of this work . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6 Thesis breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Aircraft conceptual design 9
2.1 Traditional methods . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Computational tools for conceptual design: CEASIOM . . . . . . 16
2.2.1 Coordinate systems and control sign conventions . . . . . . 16
2.2.2 AcBuilder (Geometry) . . . . . . . . . . . . . . . . . . . . 18
2.2.3 SUMO (Geometry mesher) . . . . . . . . . . . . . . . . . . 21
2.2.4 Weight & Balance . . . . . . . . . . . . . . . . . . . . . . . 21
2.2.5 AMB-CFD (Aerodynamics) . . . . . . . . . . . . . . . . . 23
2.2.6 Propulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.7 SDSA (Stability and Control) . . . . . . . . . . . . . . . . 27
2.2.8 NeoCASS (Aeroelasticity) . . . . . . . . . . . . . . . . . . 33
2.3 CPACS, a new solution . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3.1 CPACS XML file structure . . . . . . . . . . . . . . . . . . 38
2.3.2 CPACSCreator . . . . . . . . . . . . . . . . . . . . . . . . 44
3 The Blended Wing Body concept 51
3.1 Main features of the BWB . . . . . . . . . . . . . . . . . . . . . . 53
3.2 Previous models . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.2.1 Horten Ho 229 . . . . . . . . . . . . . . . . . . . . . . . . 57
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CONTENTS
3.2.2 Northrop YB-49 . . . . . . . . . . . . . . . . . . . . . . . . 58
3.2.3 MOB BWB . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.2.4 SAX-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.2.5 Cranfield University BW11 Eagle Ray . . . . . . . . . . . 62
3.2.6 NASA-Boeing X48-B . . . . . . . . . . . . . . . . . . . . . 63
3.2.7 Main features in common . . . . . . . . . . . . . . . . . . 64
3.3 ELSA BWB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4 Definition of the baseline BWB geometry 67
4.1 Definition in CPACSCreator . . . . . . . . . . . . . . . . . . . . . 67
4.1.1 Wing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.1.2 Fuselage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.1.3 Control surfaces . . . . . . . . . . . . . . . . . . . . . . . . 79
4.1.4 Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2 Geometry refinement using CATIA and SUMO . . . . . . . . . . 83
4.3 Final model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5 Generation of aerodynamic data 91
5.1 TORNADO fundamentals . . . . . . . . . . . . . . . . . . . . . . 92
5.2 B-747 example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.2.1 Description of the B-747 model . . . . . . . . . . . . . . . 95
5.2.2 Validation of aerodynamic sources . . . . . . . . . . . . . . 97
5.2.2.1 Low speed aerodynamics (M=0.15) . . . . . . . . 98
5.2.2.2 High speed aerodynamics . . . . . . . . . . . . . 100
5.2.2.3 Stability analysis . . . . . . . . . . . . . . . . . . 103
5.2.2.4 Linear mode analysis . . . . . . . . . . . . . . . . 104
5.2.3 Conclussions . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.3 TORNADO results . . . . . . . . . . . . . . . . . . . . . . . . . . 105
5.4 XFLR5 results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.5 Comparison of the two tools . . . . . . . . . . . . . . . . . . . . . 115
5.6 Parasite drag estimation . . . . . . . . . . . . . . . . . . . . . . . 116
6 Analysis of the stability and control of the BWB model 125
6.1 Theoretical introduction . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.1.1.1 Static stability . . . . . . . . . . . . . . . . . . . 125
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