Numerical Study on the Influence of Tip Clearance

• Autor(a) principal: O'Neill, Patrick Leonard
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/7963
• topic: Cfd; Fluent; Nasa; No-Tip Gap; Tip Gap; Turbina A Gás; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

Due to a constant rise in costs and a continuous demand for travel from customers, airlines look to new technologies as a way of potentially reducing operational costs, such as fuel costs. With such objectives in mind, NASA and other organizations are studying and experimenting new configurations of gas turbines to determine if this could be a viable solution for the near future. Several simulations are run for an axial compressor blade in order to verify the influence in total pressure ratio and flow velocity between the No-Tip Gap model and the Tip Gap model. This will determine the impact of tip clearance on the aforementioned parameters. The CFD simulations will be carried out using FLUENT where it is possible to determine the inlet and outlet conditions of the experiment as well as other boundary conditions to properly present the problem and a realistic solution. In this study two distinct models will be simulated, No-Tip Gap and Tip Gap, each at three different rotational speeds to simulate the impact for different velocities of blade rotation and determine which model would be more beneficial for future turbines. It was concluded that the pressure along the blade using the No-Tip Gap model was higher when compared to the Tip Gap model. This could be explained by simply analysing the surface area of the blade. Being that the blade occupies the area up to the engine casing it will have a greater surface area, hence, transferring more work and having higher pressure at the compressor exit. As for the velocity, the results were reversed, meaning that a higher velocity of flow was found when using the Tip Gap model. The explanation for this higher speed could be the existence of a tip clearance, allowing the flow to pass through this area with no contact with the blade and therefore not reducing the speed of the airflow resulting in a higher outlet velocity.