Quasi-Analytical Modelling and Optimisation Techniques for Transport Aircraft Design
Total Page：16
File Type：pdf, Size：1020Kb
QUASI-ANALYTICAL MODELLING AND OPTIMISATION TECHNIQUES FOR TRANSPORT AIRCRAFT DESIGN by Askin T. Isikveren Doctoral Thesis Report 2002-13 intentionally blank i Preface This document constitutes a dissertation of research work for eligibility of a PhD Degree from the Department of Aeronautics (Flygteknik), Royal Institute of Technology (KTH), Stockholm, Sweden. This accomplishment is not only a product of one’s ability to conceive and investigate topics under the guidance of the pedagogical process, but such a formulation of ideas or even the notion of approaching the conceptual aircraft design problem from an alternate perspective simply would not have be possible without accumulating a wide-ranging skill set in industry. In conjunction with a welcome professional association with Williams International, it is with great fortune I have had the opportunity to be employed by such companies as Hawker de Havilland Ltd, Saab Aircraft AB, American Airlines and Bombardier Aerospace. Expressions of gratitude are forwarded to my supervisor Professor Arthur Rizzi for his invaluable advice and insight during the course of this degree. As a student, I affiliate myself with the Royal Institute of Technology with honour. The institution’s progressive attitude towards selection of research topics and innovative approach to contemporary tertiary education will serve to perpetuate its unqualified prestige. A final word of profound thanks goes to my family, my wife Carina and daughter Emma, for the untold amount of patience, understanding and support exhibited by them during the protracted period of accomplishing this milestone on a part-time basis. Montreal, Quebec, Canada May 2002 Askin T. Isikveren Nota bene: The reader is advised that the data of known aircraft used in this document have intentionally not been labelled in the multitude of charts and plots presented herein. This act is to ensure the security of sometimes highly confidential information, and ensures the author does not violate any current non-disclosure agreements. ii intentionally blank iii Abstract The research work presented here focuses on the subject of transport aircraft design at the pre-design or conceptual level. The primary topics addressed are: (1) generation of a vast array of new quasi-analytical expressions to permit a conceptual treatment of commercial and business transport aircraft with adequate sensitivity for more advanced trade studies; (2) review and adoption of a method to predict stability and control characteristics (using the Mitchell method); (3) a study of the relative merits between various methods in facilitating an expedient and robust constrained multi-objective optimisation result within the context of traditional conceptual design problems (Genetic Algorithms and Nelder-Mead Simplex search); (4) creation of a software package as a new and unique conceptual tool that permits the generation of design proposals in an accurate yet expeditious manner; and, (5) practical demonstration of the new conceptual design software package by undertaking some actual aircraft design proposals. The design problem is addressed using mostly closed form solutions but transcendental expressions with much simplified numerical scheme algorithms have also been adopted for sake of accuracy. Various new models have been proposed for atmospheric properties, geometry, gas-turbine engine performance, low-speed and high- speed aerodynamic characteristics, minimum control speed limited balanced field estimation, asymmetric flight, and, en route performance characteristics including definition of operationally permissible speed schedules and flight techniques for payload- range/fixed sector profiles optimised in terms of maximum specific air range, minimum fuel, minimum time, minimum direct operating cost and maximum profit/return on investment. The work was extended further to include issues relating to the impact of vehicular attributes to pricing the market is willing to absorb. Useful information regarding how these individual computational elements of the methodology may be integrated for the purpose of constructing coherent modular sub-spaces and formulation of a basic inter- disciplinary coupling is also presented. The mathematical foundations derived in this work have lead to an array of tangible conclusions that aid the conceptual designer via implicit guidelines to achieve truly balanced design concepts. In an explicit demonstration of methodology effectiveness and relative simplicity, a software package called QCARD or Quick Conceptual Aircraft Research and Development was created in the MATLAB environment. The new software system was developed to assist the designer in predicting, visualising and optimising conceptual aircraft designs in a much more interactive and far-reaching manner than what is afforded with contemporary applications whilst emphasising speed and economy of effort. The methodology and software was employed for a 19 passenger turbofan commuter transport design using the cost effective Williams International FJ44-2 engines. To complement this, a fuselage stretch version of the baseline vehicle designed to accommodate 31-34 passengers was also undertaken utilising a growth version of the original FJ44 power plant. The minimum goal for both of these concepts was to afford unparalleled comfort through speed and spaciousness with a competitive edge against turboprops in terms of economics and field performance. The final design effort involved proposal of a Trans-Atlantic high-performance executive transport employing an unconventional Twin Oblique Lifting Surfaces, or, TOLS configuration. The intent here was to produce a new super-large business jet able to operate up to low supersonic speeds with field performance, en route fuel burn efficiency and cost comparable to that of contemporary business aircraft for this market segment. iv intentionally blank v Quasi-analytical modelling and Optimisation Techniques for Transport Aircraft Design vi intentionally blank vii Dissertation The thesis embodies a synopsis of research work undertaken for this degree and four related technical papers. A list of all the technical papers are itemised as thus, Paper I Methodology for Conceptual Design and Optimisation of Transport Aircraft Askin T. Isikveren, Paper 98-7.8.2. Presented at 21st ICAS Congress, Melbourne, Australia, September 1998. Paper II Design and Optimisation of a 19 Passenger Turbofan Regional Transport Askin T. Isikveren, Paper 1999-01-5579. Presented at 1999 World Aviation Congress and Exposition, San Francisco, USA, October 1999. Paper III High-Performance Executive Transport Design Employing Twin Oblique Lifting Surfaces Askin T. Isikveren, Paper 2001-01-3031. Presented at 2001 World Aviation Congress and Exposition, Seattle, USA, September 2001. Paper IV Identifying Economically Optimal Flight Techniques of Transport Aircraft Askin T. Isikveren, Paper C-9699. Submitted to AIAA Journal of Aircraft, status “accepted for publication”, issue pending in 2002. viii intentionally blank ix Table of Contents 1 Introduction 1 1.1 What is Conceptual Design 1 1.2 Basis and Protocol for Conceptual Aircraft Design Prediction 3 1.2.1 First Order Minimalism 4 1.2.2 Advanced Higher Order Iterative Algorithms 4 1.2.3 Quasi-analytical Algorithms – A Compromise Between Economy of Effort and Higher Order Accuracy 5 1.3 Operational Criteria Placed On Contemporary Transport Aircraft 6 1.3.1 Present-Day Air Traffic Control and Route Structure 6 1.3.2 Operationally Permissible Flight Control Techniques 7 1.4 Stability and Control 7 1.5 Multi-disciplinary Design Optimisation 8 1.6 Computer Aided Engineering in Conceptual Design 9 1.7 Decision Support Systems 11 1.8 Objectives, Scope and Thesis Structure 11 2 Formulation of a New Project Design Specifications 15 2.1 Establishing the Value of Performance and Amenities 15 2.2 Constructing the Airframer Paradigm 16 3 Mathematical Foundations: Concept of an Impulse Function 19 3.1 Mathematical Formulation and Governing Rules of Operation 19 3.2 Identification of Maxima and Minima Using the Impulse Function Approximation 20 3.3 Exponential Interpolation for Integrated Computations 20 x 4 The International Standard Atmosphere 23 4.1 Nomenclature Describing Atmospheric Properties 23 4.2 Modelling Temperature Variation 23 4.3 Density 24 4.4 Coefficient of Viscosity 24 5 Geometric Definitions 25 5.1 An Overview of Equivalent Reference Wing Conventions 25 5.1.1 Weighted Mean Aerodynamic Chord Method 25 5.1.2 ESDU Method 26 5.1.3 Simple Trapezoid or Net Method 27 5.1.4 Ancillary Wing Conventions 28 5.1.5 Fundamental Parametric Relationships for the Reference Wing 29 5.2 Quasi-analytical Methods for Fuselage Geometric Description 30 5.2.1 Fuselage Centre-Section: Cross Section Definition 31 5.2.2 Forward and Aft Fuselage Sections: Three-dimensional Definition 33 5.3 Analytical Method for Wing-to-Fuselage Fairing Geometric Description 36 5.4 Quasi-analytical Method for Turbofan Nacelle and Miscellaneous Power Plants Geometric Description 37 5.4.1 Nacelle Three-dimensional Definition 37 5.4.2 The Nacelle Geometric Design Variables 38 5.5 Estimating the Wetted Area of Primary Components 40 5.5.1 Centre Fuselage External Area 40 5.5.2 Forward and aft Fuselage External Area 40 5.5.3 Wing-Fuselage Fairing 42 5.5.4 Wing, Empennage and Other Streamlined Surfaces 42 5.5.5 Nacelle Surfaces 44 5.5.6 Sample Computations of Wetted Area Using Actual Aircraft Data 46 5.6 Estimating the Volume for Living Space and Fuel 47 5.6.1 Approximating