Design optimization of the A320 engine inlet cowl Bruno Santos da Conceição Thesis to obtain the Master of Science Degree in Aerospace Engineering Supervisors: Prof. Luís Filipe Galrão dos Reis Prof. Vítor Manuel Rodrigues Anes Examination Committee Chairperson: Prof. Filipe Szolnoky Ramos Pinto Cunha Supervisor: Prof. Luís Filipe Galrão dos Reis Member of the Committee: Prof. Aurélio Lima Araújo November 2016 ii Acknowledgments I would like to express my gratitude to Prof. Lu´ıs Reis and V´ıtor Anes for their support and recom- mendations through the development of the Thesis. I would like to thank TAP Engines Engineering department for their availability and for the opportunity of having direct contact with the components at their facilities. I would like to express my gratitude to my parents and grandparents for their support and for their moti- vational speeches when most needed. I would like to thank my sister for her wise advises when difficult decisions had to be made. Finally, I would like to thank my girlfriend for having been so supportive, patient and comprehensive when late night work had to be done. iii iv Resumo As aeronaves operam em meios nos quais os seus componentes estao˜ sujeitos a grandes variac¸oes˜ de pressao˜ e temperatura. Em estruturas como as nacelles dos motores, que sao˜ compostas por varios´ componentes e materiais, tornam-se vis´ıveis alguns sinais de desgaste e corrosao,˜ originados pela sua operac¸ao˜ em ambientes como o acima descrito. Nestes casos, devem de ser tomadas medidas correctivas. Os paineis´ acusticos´ da entrada de ar do Airbus A320/A321, apresentam alguns problemas de desgaste e corrosao˜ nas doublers de alum´ınio das juntas. Por forma a poder desenvolver-se uma acc¸ao˜ correctiva ao n´ıvel das juntas dos paineis´ acusticos,´ deve ser realizada uma analise´ do comportamento mecanicoˆ e das forc¸as actuantes nas mesmas. Nesta tese de mestrado, foi desenvolvida uma metodologia para a analise´ do comportamento mecanicoˆ das juntas dos paineis´ acusticos´ com base em ferramentas, tais como, Dinamicaˆ de Fluidos Com- putacional (CFD), Metodo´ dos Elementos Finitos (FEM) e Desenho Assistido por Computador (CAD). A modelac¸ao˜ da entrada de ar e dos seus componentes e´ feita atraves´ da utilizac¸ao˜ do programa Solidworks. A utilizac¸ao˜ do programa de CFD, STAR CCM+, permitiu a determinac¸ao˜ do carrega- mento aerodinamicoˆ a que a entrada de ar esta´ sujeita. A analise´ estrutural dos componentes da junta do painel acustico´ e´ realizada com uso das ferramentas de FEM, dispon´ıveis no programa ANSYS Workbench. Todos os passos envolvidos nestas analises´ sao˜ explicados e os resultados obtidos sao˜ apresentados. Palavras-chave: Aeronave, entrada de ar, paineis´ acusticos,´ carregamento aerodinamico,ˆ com- portamento mecanico,ˆ juntas. v vi Abstract Aircraft operate in environments in which the components are subject to large temperature and pressure variations. In structures as the engine nacelles, composed by several components and materials, the presence of wear and corrosion becomes noticeable, due to the their operation in environments as the one foremost described. Corrective actions must be employed to the components which present this kind of problems. The acoustic panels of the inlet cowl of the Airbus A320/A321, present corrosion problems on the aluminium doublers of the joints. In order to develop a corrective action to the joint of the acoustic panels, the analysis of the mechanical behaviour and forces acting on the joint must be made. In this master’s thesis, a methodology involving Computational Fluid Dynamics (CFD), Finite Element Method (FEM) and Computer Aided Design (CAD) tools is developed in order to analyse the mechanical behaviour of the acoustic panel’s joint. The geometry of the inlet cowl and of its components is modelled with the use of Solidworks software. The determination of the aerodynamic loads acting on the inlet cowl is made with the use of CFD tools, with STAR CCM+ software. The structural analysis of the members of the joint of the acoustic panels is made with the use of FEM tools in ANSYS Workbench software. The steps involved in the analysis are explained and the results are presented. Keywords: Aircraft, inlet cowl, acoustic panels, aerodynamic loads, mechanical behaviour, joints. vii viii Contents Acknowledgments........................................... iii Resumo.................................................v Abstract................................................. vii List of Contents............................................. ix List of Tables.............................................. xiii List of Figures............................................. xv Acronyms and Nomenclature..................................... xix 1 Introduction 1 1.1 Motivation.............................................1 1.2 Objectives.............................................3 1.3 Thesis Outline..........................................4 2 Background 5 2.1 Turbofan Engine.........................................5 2.2 The Nacelle............................................7 2.3 Aircraft noise...........................................9 2.3.1 Aircraft Noise Sources..................................9 2.3.2 Noise Reduction Technology.............................. 10 2.3.3 The Acoustic Liner.................................... 12 2.4 Computational Fluid Dynamics - Overview........................... 13 2.4.1 Governing Equations of Fluid Flow........................... 14 2.4.2 RANS Equations and Turbulence Models....................... 18 2.5 Joints and Fasteners....................................... 19 2.5.1 Comparison between mechanically fastened and adhesive bonded joints..... 19 2.5.2 Fasteners......................................... 20 2.5.3 Fastened Joints Failure and Prevention........................ 21 2.5.4 Honeycomb Sandwich Tensile and Shear Properties................. 24 2.6 Bolted Joints in Ansys Workbench............................... 24 2.6.1 Modelling Bolts...................................... 25 2.6.2 Modelling Contact in Joints............................... 25 ix 3 Aerodynamic Loads Determination - CFD Methodology 27 3.1 CAD Modelling of the A320/321 Nacelle Inlet......................... 27 3.2 Simulated Flight Conditions................................... 29 3.3 CFD Approaches......................................... 30 3.3.1 Methodology 1...................................... 30 3.3.2 Methodology 2...................................... 30 3.4 The CFD Methodology...................................... 32 3.4.1 Computational Domain................................. 32 3.4.2 Generated Mesh..................................... 32 3.4.3 The Problem Physics.................................. 34 3.5 Boundary Conditions....................................... 36 3.5.1 Setting The Boundary Conditions............................ 36 3.5.2 The FAN Boundary Condition Calculation....................... 37 3.6 Methodology Suitability..................................... 38 3.7 CFD Results and Discussion.................................. 39 4 FEM Methodology - Analysis of the Joints of the Acoustic Panel 51 4.1 Inlet Cowl Components..................................... 51 4.1.1 The Acoustic Panel Joint................................ 52 4.2 Preparing the FEM Simulations................................. 52 4.2.1 Aerodynamic Load.................................... 53 4.2.2 Geometry and Geometry Importation......................... 54 4.2.3 Materials and Properties................................. 55 4.2.4 Contact Between Components............................. 58 4.2.5 Defining the Mesh.................................... 59 4.3 Determination of the Critical Load Condition.......................... 60 4.3.1 Model Considerations.................................. 60 4.4 Approach to Analyse the Acoustic Panel Joint......................... 61 4.4.1 Model Simplifications.................................. 62 4.5 Analysis of the fasteners of the Joint.............................. 64 4.5.1 Components Contact and Mesh Refinement..................... 64 4.5.2 Convergence Analysis.................................. 65 4.5.3 Result and Discussion of the Fasteners Analysis................... 66 4.6 Analysis of the Interface between Internal Honeycomb Core and Internal Doubler..... 70 4.6.1 Components Contact and Mesh Refinement..................... 70 4.6.2 Convergence Analysis.................................. 71 4.7 Results and Discussion of the Joints Analysis......................... 72 4.7.1 The Flatwise Tensile Strength.............................. 73 4.7.2 The Shear Stress..................................... 74 x 5 Conclusions 75 5.1 Future Work............................................ 76 6 Bibliography 77 A Appendix - Noise Certification Points 81 B Appendix - T.P.S. Experimental Properties 83 C Appendix - LOCTITE EA 9658 AERO - Technical Datasheets 85 xi xii List of Tables 2.1 CFM56-5B engine data [13]...................................7 2.2 Quota Count system classification [22]............................. 10 2.3 Torque Coefficient for different bolt conditions [34]....................... 22 3.1 Simulated flight conditions.................................... 30 3.2 Main physical properties of the simulation............................ 35 3.3 Boundary condition summary................................... 37 3.4 T.P.S Pressure Coefficient comparison between numerical and experimental results.... 41 3.5 Half and complete model comparison.............................