Design and Noise Acceptability of Future Supersonic Transport Aircraft MSc. Thesis J.I. Nijsse Cover image: British Airways Concorde G­BOAC by Eduard Marmet, https://commons.wikimedia.org/wiki/File:British_Airways_Concorde_G­BOAC_02.jpg. CC BY­SA 3.0 (https://creativecommons.org/licenses/by­sa/3.0) Design and Noise Acceptability of Future Supersonic Transport Aircraft MSc. Thesis by J.I. Nijsse to obtain the degree of Master of Science at the Delft University of Technology, to be defended publicly on Friday December 18, 2020 at 10:30 AM. Student number: 4218124 Project duration: May 2018 – December 2020 Thesis committee: Prof.dr.ir. L.L.M. Veldhuis, TU Delft, committee chair Ir. J.A. Melkert, TU Delft, supervisor Dr.ir. M. Snellen, TU Delft An electronic version of this thesis is available at http://repository.tudelft.nl/. Contents Contents iii Summary vii List of Figures ix List of Tables xi Abbreviations xiii Lift of Symbols xv 1 Introduction 1 1.1 Market analysis ......................................... 1 1.2 Characteristics of supersonic flight .............................. 2 1.3 Research goal ......................................... 2 1.4 Report structure ........................................ 3 2 The design program 5 2.1 Aircraft design ......................................... 5 2.2 Program building ........................................ 6 2.3 Program layout ......................................... 6 3 Aircraft weight and design point 9 3.1 Initial MTOW estimation .................................... 9 3.2 Design point calculation .................................... 10 3.2.1 Stall speed ....................................... 10 3.2.2 Takeoff distance .................................... 10 3.2.3 Landing distance .................................... 11 3.2.4 Climb performance ................................... 11 3.2.5 Cruise speed ...................................... 12 3.2.6 Correction factors ................................... 12 3.2.7 Results ......................................... 13 3.2.8 Verification and validation ............................... 14 4 Engine design 17 4.1 Engine design method ..................................... 17 4.1.1 Cycle calculation .................................... 18 4.1.2 Design steps ...................................... 22 4.1.3 Engine size calculations ................................ 23 4.2 Engine off­design calculation ................................. 25 5 Geometric design 27 5.1 Fuselage design ........................................ 27 5.1.1 Nose and tail section .................................. 27 5.1.2 Cabin .......................................... 28 5.2 Wing design ........................................... 31 iii iv Contents 5.2.1 Planform shape .................................... 31 5.2.2 Subsonic leading edge ................................ 33 5.3 Empennage design ....................................... 34 5.4 Fuel tanks ............................................ 34 6 Aerodynamics and Class II weight estimation 37 6.1 Lift analysis ........................................... 37 6.2 Drag analysis .......................................... 39 6.2.1 Subsonic drag ..................................... 39 6.2.2 Supersonic drag .................................... 40 6.3 Class II weight estimation ................................... 41 6.3.1 V­n diagrams ...................................... 41 6.3.2 Weight estimation ................................... 42 6.3.3 Calibration ....................................... 42 6.3.4 Technological developments ............................. 42 7 Exploring the design space 43 7.1 Full program validation ..................................... 43 7.2 Design space exploration ................................... 44 7.2.1 Parameter selection .................................. 45 7.2.2 Parameter variations .................................. 45 7.3 Aircraft designs ......................................... 55 8 Low­speed noise analysis 57 8.1 Noise regulations ........................................ 57 8.2 Noise modelling ........................................ 59 8.2.1 Fully analytical methods ................................ 59 8.2.2 CFD combined with acoustic analogy ........................ 59 8.2.3 Fully numerical methods ................................ 59 8.2.4 Semi­empirical methods ................................ 59 8.2.5 Method applicability .................................. 59 8.3 Low­speed noise estimation method ............................. 61 8.3.1 Aircraft noise sources ................................. 61 8.3.2 Supersonic aircraft noise ............................... 62 8.3.3 Noise reduction measures ............................... 63 8.3.4 Noise prediction .................................... 65 9 Supersonic noise prediction 69 9.1 Sonic boom background .................................... 69 9.2 Sonic boom prediction ..................................... 71 9.3 Prediction results ........................................ 75 9.3.1 Method comparison .................................. 75 9.3.2 Acceptability of boom loudness ............................ 80 10 Conclusion 83 11 Recommendations 85 Bibliography 87 A Validation data for design point method 93 B Support data for engine method 95 B.1 Validation data for engine design ............................... 95 B.2 Station numbering ....................................... 98 B.2.1 Primary station numbering .............................. 98 B.2.2 Secondary station numbering ............................. 98 Contents v C Geometric data 101 C.1 Aircraft configuration ......................................101 C.2 Supersonic aircraft length and slenderness . 104 D Program inputs 105 D.1 Main inputs ...........................................105 D.1.1 Run parameters ....................................105 D.1.2 Key design parameters ................................105 D.1.3 Performance first guess parameters . 106 D.1.4 Airport constraints ...................................106 D.1.5 Maximum lift coefficients first guess . 107 D.1.6 Climate parameters ..................................107 D.2 Secondary inputs ........................................108 D.2.1 Run parameters ....................................108 D.2.2 Passenger data ....................................108 D.2.3 Class I inputs ......................................109 D.2.4 Aerodynamics inputs ..................................109 D.2.5 Airfoil inputs ......................................110 D.2.6 Class II inputs .....................................110 D.2.7 Geometry inputs .................................... 111 D.2.8 Engine inputs ...................................... 111 D.3 Parameter selection for sensitivity analysis .........................112 E Sonic boom and aircraft shaping 115 Summary Despite the COVID­19 outbreak, civil aviation is expected to grow in the long term. As part of this growth, companies are designing a new generation of supersonic aircraft. Concorde proved that flying supersonically results in high fuel burn, loud noise around airports and a loud sonic boom below the flight path. Therefore, it may be the case that this new generation of supersonic aircraft is unacceptable for the public. Due to a request of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP) two theses were created: one focussing on the acceptability of the emissions of supersonic aircraft and this one focussing on the acceptability of their produced noise. To investigate the noise production a design program has been created first. Using Python, various modules were combined into a single program for the design and analysis. This program consists of an iterative phase, containing a Class I weight estimation, design point calculation, engine design, geometry design, aerodynamics and a Class II weight analysis. When a design solution converges, the non­iterative phase is started which performs the noise and climate analyses and produces the output files. The Class I weight estimation predicts the takeoff mass based on the design mission profile and a predicted fuel usage. Based on this takeoff mass estimate the design point for wing loading and thrust loading is calculated. A set of constraints is then created to limit the wing size and thrust based on parameters like runway distance required and climb performance. This results in an optimal wing area and thrust for the given takeoff mass. Comparing the calculated design point to data from a set of real and conceptual aircraft resulted in a reasonable accuracy. The selected engine type is a low­bypass turbofan. To model the engine a cycle calculation method is used. This method evaluates every component in a zero­dimensional analysis where its temperature, pressure and mass flow rate are calculated. By using predefined component efficiencies and optimising the fuel flow rate for the required thrust, a suitable engine design is created. Its size and mass are estimated by using statistics. For all mission phases the engine off­design performance is calculated. Following this, the fuselage and wings are designed. The fuselage is a cylinder with the nose and tail sections defined as Von Kármán shapes. To ensure the wave drag is low the fuselage has a high slenderness ratio. The wing design is based on a trade­off between five planforms. The result of this trade­off is a cranked arrow wing with a subsonic leading edge and an inboard trailing edge sweep angle of 90∘. The empennage design is