Computer Aided Design for Manufacturing and Tolerancing for a Turbine Stage

The design process has always been a complicated, long and iterative procedure and this is particularly true in the case of an aviation jet engine, therefore this thesis, which was carried out inside Avio Aero who is a world leader in the design of low pressure turbine, has the aim of finding and implementing new and innovative methods to achieve a smarter, more cost efficient and more optimized design process, in this case for the low pressure turbine component. But first of all, a brief introduction of an aviation jet engine is given, going over all the main principles, the significant factors that influence the performances of an aviation engine, as well as describing the most common configurations and architectures of an aviation engine, especially the most used one that is the turbofan architecture. Going deeper, a description of the main components present inside the engine is also made, with particular focus on the low pressure turbine. This introduction is needed in order to understand the principles behind the design process of an aviation engine and only then it will be clear why certain components have certain shapes and materials. Afterwards, a small digression is made to describe the project of Great2020, its birth, its objectives set for the year 2020 compatible with those set by ACARE, and the main actors and laboratories participating in this project. This is important to understand the current state of the art and the context on which this thesis finds itself in as well as to understand the possible future trends and scenarios reserved for the aviation engine of future generation. Then we will shift our attention back to the low pressure turbine, in particular the description of some of the analysis needed to verify this complex component, such as the modal analysis and the static analysis. A particular focus will be given to the overall procedure to carry out these analyses and showing the possible results that can be obtained. Next we will move to a different topic but still significant in the design of a component, and that is manufacturing, and therefore a brief introduction is given of the main manufacturing operations, especially those relevant to the manufacture of a turbine blade, such as casting and machining. In addition, possible future trends regarding this field is also presented. This will be necessary to understand the next part, which is the main topic of this thesis and it concerns the concept of design for manufacturability (DFM). A brief description of its principles and how it works is present, with particular focus to its benefits compared to the traditional design process. Then we will move on with the implementation of a possible DFM code for LPT blade and the results that can be achieved. Aside from the analysis of manufacturability, another analysis has also been carried out concerning the assembly operation, and that is tolerancing stack up analysis. That is why after a brief introduction to the stackup methods, a deep analysis is shown of a new and innovative method, through a commercial software, to carry out a 3D variational analysis based on Monte Carlo simulations, which could be used to substitute the old traditional methods. Finally, this thesis will end with the description of future proposals to improve and optimize both the code for DFM and the 3D variational analysis as well as possible trends and scenarios reserved for the field of design for manufacturing of a turbine blade.