Thermo-mechanical Modeling of a High Pressure Turbine Blade of an Airplane Gas Turbine Engine Pedro Marques Borges Brandão Thesis to obtain the Master of Science Degree in Mechanical Engineering Supervisors: Prof. Augusto Manuel Moura Moita de Deus Prof. Virginia Isabel Monteiro Nabais Infante Examination Committee: Chairperson: Prof. Luís Manuel Varejão Oliveira Faria Supervisor: Prof. Augusto Manuel Moura Moita de Deus Members of the Committee: Prof. Maria de Fátima Reis Vaz June 2015 ii Acknowledgment I would like to thank my thesis supervisor, Professor Augusto Moita de Deus, for all his guidance, patience and help, as well as for creating an environment of trust and ease, and mainly for always being available to address all and any doubts, difficulties or issues, and providing valuable advice, suggestions and much needed constructive criticism during this project. I would also like to thank my co-supervisor, Professor Virginia Infante, whom has accompanied this project since its inception and provided me with invaluable help, advice, and contacts, as well as directing me into the mentorship of my thesis advisor. This project would also have been impossible without the support of the Maintenance and Engineering Management of SATA Air Açores, and I would like to specially thank its director, Engineer Pedro Viveiros, with whom the idea of this thesis was first developed, for providing me all the conditions for this project to be made, and also my colleagues at the Engineering Department, especially Engineering Manager Nuno Rangel, for all the help, advice and patience they afforded me, as well as for the invaluable data on which this project is based. I would like to thank Professor Luis Sousa and Professor Marco Leite, for their assistance in the creation of the part’s 3D model, Professor Luís Alves and Engineer Isabel Nogueira, for their help in extracting some of the scrap part’s properties and composition data, and specially Professor Rui Ruben, for all is help and expertise with the Abaqus software, thus providing me the tools to complete this project. I would also like to thank all my friends and colleagues, that for the past years have accompanied me in this journey, without whom I wouldn’t have been able to reach this point in my life, my friends at TUCA, my teammates at AEIST Waterpolo and specially Vasco van Zeller, whose direct help with this project spared me countless hours of headaches. To Débora Simões, I would like to thank her for her love, caring and for being there for me on the more frustrating and though parts of this project. Last but not least, I would like to thank my family, especially my mother, father and sister, for their infinite and unwavering love, patience and support, and for putting up with me for all these years, especially for the duration of this project. i ii Resumo Durante a sua operação, os componentes de motores aeronáuticos estão sujeitos a condições de operação cada vez mais exigentes, tais como ciclos de temperaturas elevadas, elevadas velocidades de rotação e elevadas pressões, especialmente no caso das pás de turbina de alta pressão. Estas condições obrigam estas pás a estarem sujeitas a diferentes tipos de degradação dependente do tempo, um dos quais é a fluência, um mecanismo de ruína que pode reduzir significativamente a vida do componente, quer pela criação de fendas por fluência, quer através de sobre alongamento da pá que pode entrar em contacto com o revestimento interno da turbina. Deste modo, o objetivo deste projeto é a criação de um modelo utilizando o método dos elementos finitos, a fim de ser capaz de prever o comportamento da pá da turbina de alta pressão em fluência e o seu alongamento ao longo do tempo. A fim de atingir este objetivo, registos de voo de uma aeronave específica, providenciados por uma companhia aérea, foram utilizados para se obterem dados térmicos e mecânicos, isto é, a variação de temperatura entre turbinas e a variação de velocidade de rotação da turbina de alta pressão, para três tipos de ciclo de voo diferentes. Para criar o modelo 3D necessário para a análise pelo método dos elementos finitos, uma pá de turbina de alta pressão descartada foi utilizada, assim como para obter a composição e propriedades do material, também necessárias para essa análise. A pá descartada foi digitalizada utilizando um scanner 3D, e um software de modelação 3D foi utilizado para o modelo. A fim de determinar a sua composição química, foi efetuada sobre a superfície da pá descartada uma microscopia por varrimento de eletrões, assim como uma análise por espectroscopia de energia dispersiva. Todos os dados obtidos foram introduzidos no programa de elementos finitos e diferentes simulações foram efetuadas, primeiro com um modelo 3D simplificado de um paralelepípedo, para se aferir o modelo, seguidas de simulações com o modelo 3D simplificado obtido através da pá descartada. Estas simulações geraram resultados aceitáveis, apesar das limitações do modelo, uma vez que muitos aspetos importantes tiveram que ser ignorados ou simplificados. Não obstante, este modelo é visto como um bom passo em diante, e diversas melhorias, que podem ser feitas a fim de se aumentar a precisão do modelo, foram identificadas. Palavras-Chave Pá de Turbina de Alta Pressão, Fluência, Análise pelo Método dos Elementos Finitos, Modelo 3D, Simulação. iii iv Abstract During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, such as high temperature cycles, rotation speeds and pressure, especially the high pressure turbine (HPT) blades. These conditions make these blades undergo different types of time-dependent degradation, one of which is creep, a failure mechanism that can significantly reduce the parts life, either by generation of cracks, or by over-elongation of the blade tip, that may contact with the turbine’s casing. Thus, the goal of this project is to create a model using the finite element method (FEM), in order to be able to predict the HPT blade’s creep behavior and its elongation over time. In order to accomplish this, flight data records (FDR) for a specific aircraft provided by an aviation company were used to obtain thermal and mechanical data, i.e. inter turbine temperature (ITT) variation and HPT rotation speed variation, for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was used, as well as to obtain the blade’s chemical composition and material properties, also needed for that analysis. The blade scrap was scanned using a 3D mapping scanner, and 3D modeling software was used to create the model. In order to determine the scrap part’s chemical composition, surface scanning electron microscopy (SEM) was performed as well as energy dispersive spectroscopy (EDS) analysis. All the data gathered was fed into the FEM software used and different simulations were ran, first with a simplified 3D rectangular block shape to evaluate the model, and then with the simplified 3D model obtained from the blade scrap. The simulations yielded suitable results, despite the limitations of the model, as many important considerations had to be taken out or simplified. Nevertheless, it is seen as a good work in progress and several improvements, that can be made in order to achieve greater model accuracy, were identified. Keywords High Pressure Turbine Blade, Creep, Finite Element Method, 3D Model, Simulation. v vi Table of contents ACKNOWLEDGMENT .............................................................................................................................. I RESUMO ............................................................................................................................................... III PALAVRAS-CHAVE ................................................................................................................................ III ABSTRACT.............................................................................................................................................. V KEYWORDS ............................................................................................................................................ V TABLE OF CONTENTS ........................................................................................................................... VII LIST OF TABLES ..................................................................................................................................... IX LIST OF FIGURES ................................................................................................................................... XI LIST OF SYMBOLS ................................................................................................................................ XV 1. INTRODUCTION ............................................................................................................................. 1 2. BACKGROUND ............................................................................................................................... 2 2.1. GAS TURBINE CYCLE ......................................................................................................................... 2 2.1.1. The Brayton Thermal Cycle ..................................................................................................... 2 2.1.2. The Split-shaft Simple Cycle .................................................................................................... 4 2.2. AIRCRAFT GAS TURBINE ENGINES ........................................................................................................ 5 2.2.1. Turbojet .................................................................................................................................. 5 2.2.2. Turbofan ................................................................................................................................. 5 2.2.3. Turboprop ............................................................................................................................... 6 2.3. THE PW150A TURBOPROP ENGINE .................................................................................................... 7 2.3.1. Overview ................................................................................................................................. 7 2.3.2. Reduction Gearbox Module .................................................................................................... 7 2.3.3. Turbomachinery Module ........................................................................................................ 8 2.4. HIGH PRESSURE TURBINE (HPT) BLADE ............................................................................................. 16 2.4.1. Function of HPT Blades ......................................................................................................... 17 2.4.2. Common Failure Mechanisms .............................................................................................. 18 2.4.3. Materials .............................................................................................................................. 24 2.4.4. Protection Modes and Cooling Schemes .............................................................................. 29 2.5. CREEP IN NICKEL-BASE SUPPERALLOY HPT BLADES ............................................................................... 32 2.5.1. Creep Characteristics ............................................................................................................ 32 2.5.2. Creep Inducing Factors ......................................................................................................... 33 2.5.3. Superalloy Microstructure .................................................................................................... 33 vii 3. METHODOLOGY .......................................................................................................................... 36 3.1. PROBLEM DESCRIPTION ................................................................................................................... 36 3.2. FLIGHT DATA RECORD PROCESSING ................................................................................................... 37 3.3. PART REVERSE ENGINEERING AND MODELING ..................................................................................... 42 3.3.1. Part Modeling ....................................................................................................................... 42 3.3.2. Superalloy Material Data and Composition ......................................................................... 45 3.3.3. Superalloy Selection and Properties ..................................................................................... 49 3.4. FINITE ELEMENT MODELING ............................................................................................................. 55 3.4.1. Rectangular Block Model ...................................................................................................... 55 3.4.2. Blade Model.......................................................................................................................... 61 4. RESULTS AND DISCUSSION .......................................................................................................... 66 4.1. THERMAL ANALYSIS RESULTS ............................................................................................................ 67 4.2. ANALYSES COMPARISON .................................................................................................................. 68 4.3. ELASTOPLASTIC ANALYSIS VS CREEP ANALYSIS ...................................................................................... 70 4.4. CYCLE ACCUMULATION ANALYSIS ...................................................................................................... 74 5. CONCLUSION ............................................................................................................................... 79 5.1. FUTURE WORK ............................................................................................................................... 80 6. REFERENCES ................................................................................................................................ 81 APPENDIX .............................................................................................................................................. 2 APPENDIX A – EXAMPLE EXCERPT FROM ORIGINAL FLIGHT DATA RECORD FILE PROVIDED BY THE AIRLINE COMPANY ......... 2 APPENDIX B – MESH CONVERGENCE AND ERRORS ............................................................................................... 3 APPENDIX C – TEMPERATURE DISTRIBUTION ON THE THERMAL MODEL .................................................................... 5 APPENDIX D – DISTRIBUTION OF STRESS, STRAIN AND DISPLACEMENT FOR THE REMAINING DIRECTIONS ........................ 9 viii