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Helicopter Blade Twist Optimization in Forward Flight Aerospace

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Helicopter Blade Twist Optimization in Forward Flight Aerospace Helicopter Blade Twist Optimization in Forward Flight Marco Lonoce Thesis to obtain the Master of Science Degree in Aerospace Engineering Supervisor(s): Prof. Filipe Szolnoky Ramos Pinto Cunha Examination Committee Chairperson: Prof. Fernando José Parracho Lau Supervisor: Prof. Filipe Szolnoky Ramos Pinto Cunha Member of the Committee: Prof. João Manuel Gonçalves de Sousa Oliveira November 2016 ii To my father... iii iv Acknowledgments I want to start by thanking Professor Filipe Cunha for the theme of thesis and for his help during the work. Every meeting was really important to understand the correct direction to the end of this thesis. My university in Italy, Politecnico di Torino, that gives me the opportunity of a Double Degree Project with the Instituto Superior Tecnico in Lisbon, Portugal. It was fundamental the heavy work between the coordinator of the two universities to create this new project. The important help that the government of Italy and Piedmont region gave me as scholarship and student residence every year. My family and specially my father that couldn’t see the end of my studies. They believed me in every choice that I took. Finally, all of people that were not mentioned but gave a contribution to this thesis. v vi Resumo O incremento da eficienciaˆ do helicoptero´ e´ um aspecto fundamental a ter em considerac¸ao˜ no desenvolvimento inicial do helicoptero.´ Este ponto pode ser conseguido de varias´ maneiras. Em relac¸ao˜ a` potenciaˆ consumida ha´ certos aspectos ligados a` aerodinamicaˆ do rotor que precisam de ser tomados em conta, em especial a potenciaˆ induzida aquela que e´ necessaria´ fornecer ao rotor para este gerar a propulsao.˜ E´ poss´ıvel minimizar esta potenciaˆ uniformizando a velocidade induzida ao longo da pa´ para todas as posic¸oes˜ azimutais. Nesta tese e´ explorada a ideia de modificar a torc¸ao˜ na pa´ para cada condic¸ao˜ de voo de maneira a minimizar a potenciaˆ induzida. Sao˜ considerados as seguintes hipoteses:´ uma secc¸ao˜ com torc¸ao˜ linear, uma secc¸ao˜ com torc¸ao˜ quadratica,´ duas secc¸oes˜ com torc¸oes˜ lineares, e tresˆ secc¸oes˜ com torc¸oes˜ lineares. Por outro lado esta tese tem tambem´ como objectivo determinar quais os conceitos apresentam uma boa oportunidade para a aplicac¸ao˜ de uma controlo activo da torc¸ao˜ da pa.´ As simulac¸oes˜ foram realizadas tendo como base o Sikorsky UH-60A Black Hawk, para o qual todos os parametrosˆ do rotor estao˜ dispon´ıveis. Palavras-chave: Controlo activo da torc¸ao,˜ reduc¸ao˜ da potenciaˆ induzida, estruturas adap- tativas, optimizac¸ao˜ do rotor principal, actuadores piezoeletricos,´ materiais compositos´ em fibras. vii viii Abstract Improving the efficiency of the helicopter is one of the main objective in helicopter design. Several ways are already taken in account to achieve this purpose. In relation to the power consumption there are some aspects connected with the aerodynamic of the main rotor, specially the induced power, the power used to generate the thrust needed to fly. It’s possible to minimize this power trying to uniform the inflow along the blade for all the azimutal positions. In this thesis the idea is to modify the blade twist in each flight conditions to obtain the minimum induced power. The twist distribution concepts considered are one segment linear twist, quadratic twist, two linear twist segments with different divisions of the blade in inner and outer parts and a three linear twist segments with different airfoils. This thesis has the purpose to understand which concepts represent good opportunity for active twist control implementations. With the results of the simulations a simple active twist control concept is developed. An objective is to understand which piezoelectric actuators work better for this purpose, where they have to be placed and how they have to be actuated. All the simulations are done on the Sikorsky UH-60A Black Hawk where all the main rotor parameters are available. Keywords: Active Twist Control, Induced power reduction, morphing, main rotor optimization, piezoelectric actuators, macro fibers composite materials. ix x Contents Acknowledgments...........................................v Resumo................................................. vii Abstract................................................. ix List of Tables.............................................. xiii List of Figures............................................. xv Nomenclature xvii Nomenclature.............................................. xviii 1 Introduction 1 1.1 Motivation.............................................1 1.2 Active Blade Twist Control....................................2 1.3 Objectives.............................................3 1.4 Thesis Outline..........................................3 2 Background 5 2.1 Momentum Theory........................................5 2.2 Blade Element Theory......................................8 2.3 Xfoil................................................9 2.4 Blade Element Momentum Theory............................... 11 2.5 Inflow Models........................................... 12 2.6 Flapping.............................................. 15 2.7 Fmincon and Global Search................................... 16 3 Implementation 17 3.1 Numerical Model......................................... 17 3.2 Verification and Validation.................................... 25 3.3 Effect of Blade twist on Main Rotor Power........................... 26 4 Results 31 4.1 Optimized Blade Twist...................................... 31 4.1.1 One section with linear twist............................... 32 4.1.2 Quadratic Twist...................................... 32 xi 4.1.3 Two sections with linear twist.............................. 34 4.1.4 Two sections with linear twist and different airfoils................... 36 4.1.5 Three linear segments.................................. 37 4.2 Optimum Solution........................................ 38 5 Concept 41 5.1 Smart Blades........................................... 41 5.2 Constraints............................................ 42 5.3 Piezoelectric Actuation Systems................................ 43 5.4 Application............................................ 46 6 Conclusions 51 6.1 Future Work............................................ 52 Bibliography 52 A Appendix: Matlab Code 59 A.1 Main Code............................................ 59 A.2 Constraints............................................ 69 A.3 Optimization function....................................... 71 A.4 Flapping.............................................. 72 xii List of Tables 3.1 UH-60A Tail Rotor Characteristics [19]............................. 25 3.2 UH-60A Data [19]........................................ 25 4.1 Reduction of power between Fixed linear twist and simulations............... 39 5.1 Actuators Properties [6]..................................... 47 5.2 Actuators and Concepts Comparison.............................. 48 xiii xiv List of Figures 2.1 Flow Model Momentum Theory Hovering...........................6 2.2 Blade Element Theory Model..................................8 2.3 Forces around NACA 23015 - Xfoil............................... 10 2.4 CP distribution NACA 23015 - Xfoil............................... 10 2.5 Local Momentum Analysis BEM Theory............................ 11 2.6 Velocity distribution Hovering.................................. 13 2.7 Inflow and Thrust Hovering................................... 14 2.8 Velocity distribution Forward Flight............................... 14 2.9 Flapping Hinge.......................................... 16 3.1 Sikosrky SC 1095 Airfoil..................................... 17 3.2 Sikosrky SC 1094 R8 Airfoil................................... 18 3.3 Error Analysis lift curve..................................... 19 3.4 Error Analysis drag curve.................................... 19 3.5 Interpolation lift curve...................................... 20 3.6 Interpolation drag curve..................................... 20 3.7 Blade Elements for Hovering.................................. 22 3.8 Blade Elements for Forward Flight............................... 23 3.9 Number of Azimuthal Position.................................. 23 3.10 Flight Test Data Comparison.................................. 26 3.11 Power consumption with different twists - Hovering...................... 27 3.12 Power consumption with different twists - Low Speed Forward Flight............ 28 3.13 Power consumption with different twists - Medium Speed Forward Flight.......... 28 3.14 Power consumption with different twists - High Speed Forward Flight............ 29 3.15 Comparison among different twist behaviours......................... 29 4.1 Linear Twist - Only one section................................. 32 4.2 Parameter a - Quadratic twist.................................. 33 4.3 Root Tip difference - Quadratic twist.............................. 33 4.4 Two sections with linear twist 40 - 60.............................. 34 4.5 Two sections with linear twist 50 - 50.............................. 35 xv 4.6 Two sections with linear twist 60 - 40.............................. 35 4.7 Two sections with linear twist 70 - 30.............................. 36 4.8 Two sections, two airfoils and linear twist 50 - 50....................... 36 4.9 Blade planform UH-60A..................................... 37 4.10 Three sections with linear twist................................. 38 4.11 Sikorsky UH-60A Twist.....................................
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