Efeitos da inserção de protuberâncias no desempenho de uma turbina hidráulica do tipo Francis
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Data
2022-10-31
Autores
Matos Campos, Henrique
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Universidade Estadual Paulista (Unesp)
Resumo
Atualmente, o setor hidrelétrico é responsável por 63,8% da geração de energia elétrica no Brasil. Porém, devido às questões socioambientais e ao impacto causado durante a instalação de hidrelétricas para o crescimento do setor, tem-se investido na implementação de pequenas centrais hidrelétricas e modernização do parque hidrelétrico . Neste contexto a aplicação de dispositivos passivos nas turbinas hidráulicas tem se destacado, sendo a inserção de protuberâncias no bordo de ataque das pás do rotor uma das alternativas a ser estudada para melhoria dos projetos destes equipamentos, pois os impactos da aplicação deste dispositivo em turbinas hidráulicas ainda são desconhecidos . Deste modo, buscou-se avaliar, através de uma metodologia de simulação numérica, se a inserção de protuberâncias nas pás do rotor de uma turbina hidráulica é uma alternativa para aumentar a eficiência e o torque em turbinas hidráulicas e se a variação dos parâmetros estruturais das protuberâncias impactaram a eficiência e o torque deste tipo de turbina. Para isso, utilizou-se o softwares Ansys Meshing para a geração de malhas computacionais e Ansys CFX para resolver o escoamento na turbina hidráulica Francis fornecida pelo "workshop" Francis-99. Durante o estudo foram comparados o escoamento no rotor sem protuberâncias com o escoamento no rotor com diferentes configurações de protuberâncias encontradas na literatura. Nas análises não se obteve impactos significativos na eficiência do equipamento para a maioria das configurações e condições de operação testadas. Porém, na avaliação do torque percebeu-se ganhos de até 0,34% com a inserção do dispositivo apenas na pá principal e de até 0,53% ao utilizar o dispositivo tanto na pá auxiliar quanto na pá principal, sendo os maiores ganhos encontrados no ponto de máxima eficiência da turbina. Ao testar a inserção do dispositivo em uma geometria adaptada do rotor da usina hidrelétrica de Ilha Solteira, os impactos das protuberâncias foram mais significativos, propiciando ganhos de torque de até 1,77%. Além do aumento do torque houve um aumento de altura líquida de até 0,75% para a geometria da Francis-99 com protuberâncias na pá auxiliar e na pá principal e de até 4,13 para a geometria adaptada do rotor da hidrelétrica de Ilha Solteira. Avaliando o escoamento, verificou-se, que os ganhos obtidos no torque e na altura líquida foram causados pelas alterações no campo de velocidade e pressão próximo ao bordo de ataque das pás da turbina, devido a redução da pressão na superfície de sucção e do retardamento do descolamento da camada limite na superfície de pressão.
Nowadays, the Hydropower Industry is responsible for 63,8% of the electrical generation in Brazil. However, due to social and environmental issues and the impact during the installation of hydroelectric power plants for the Hydropower Industry growth, investments have been made in the implementation of small hydroelectric plants and the modernization of the Brazilian hydroelectric park. In this context, the application of passive devices in hydraulic turbines has stood out, being the insertion of leading-edge tubercles in the runner blades one of the alternatives to be studied for turbines projects improvement, since the impacts of the application of this device on hydraulic turbines are still unknown in the literature. The objective of the current study is to develop a numerical methodology capable of determining if the insertion of Leading-Edge Tubercles is an alternative to improve the efficiency and torque of hydraulic turbines and also to measure the impact of the leading-edge tubercles parameters variation in the efficiency and torque of the turbine. For this, we used Ansys Meshing for the numerical meshes generation and Ansys CFX to solve the flow in the Francis turbine provided by the Francis-99 workshop. In the study, we compared the flow over the Francis-99 original runner with the flow over modified runner geometries with leading-edge tubercles proposed by the literature. The results showed any significant impact on the efficiency for most of the test configurations and conditions. However, with the tubercles insertion, only in the turbine blade we obtained gains up to 0,3%, and gains up to 0,53%, by using the tubercles on the main blade and the splitter, being the higher gains obtained for the turbine operating at its best efficiency point. By testing the leading-edge tubercles insertion in a geometry adapted from the Ilha Solteira hydroelectric plant turbines runner, we obtained higher gains in torque generation, up to 1,77%. Along with the increase in the torque generation, we also verified an increase in the turbine net head, which was up to 0,75% for Francis-99 geometry with the tubercles on the main blade and the splitter and up to 4,13% for the geometry adapted from the Ilha Solteira hydroelectric plant turbines runner. By analyzing the flow behavior, we observed that the gains in torque and net head occurred due to the flow field modification in the leading edge of the turbine blade, being the device capable of reducing the pressure on the leading edge of the suction side and delay in the boundary layer separation in the pressure side.
Nowadays, the Hydropower Industry is responsible for 63,8% of the electrical generation in Brazil. However, due to social and environmental issues and the impact during the installation of hydroelectric power plants for the Hydropower Industry growth, investments have been made in the implementation of small hydroelectric plants and the modernization of the Brazilian hydroelectric park. In this context, the application of passive devices in hydraulic turbines has stood out, being the insertion of leading-edge tubercles in the runner blades one of the alternatives to be studied for turbines projects improvement, since the impacts of the application of this device on hydraulic turbines are still unknown in the literature. The objective of the current study is to develop a numerical methodology capable of determining if the insertion of Leading-Edge Tubercles is an alternative to improve the efficiency and torque of hydraulic turbines and also to measure the impact of the leading-edge tubercles parameters variation in the efficiency and torque of the turbine. For this, we used Ansys Meshing for the numerical meshes generation and Ansys CFX to solve the flow in the Francis turbine provided by the Francis-99 workshop. In the study, we compared the flow over the Francis-99 original runner with the flow over modified runner geometries with leading-edge tubercles proposed by the literature. The results showed any significant impact on the efficiency for most of the test configurations and conditions. However, with the tubercles insertion, only in the turbine blade we obtained gains up to 0,3%, and gains up to 0,53%, by using the tubercles on the main blade and the splitter, being the higher gains obtained for the turbine operating at its best efficiency point. By testing the leading-edge tubercles insertion in a geometry adapted from the Ilha Solteira hydroelectric plant turbines runner, we obtained higher gains in torque generation, up to 1,77%. Along with the increase in the torque generation, we also verified an increase in the turbine net head, which was up to 0,75% for Francis-99 geometry with the tubercles on the main blade and the splitter and up to 4,13% for the geometry adapted from the Ilha Solteira hydroelectric plant turbines runner. By analyzing the flow behavior, we observed that the gains in torque and net head occurred due to the flow field modification in the leading edge of the turbine blade, being the device capable of reducing the pressure on the leading edge of the suction side and delay in the boundary layer separation in the pressure side.
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Palavras-chave
Dinâmica dos Fluidos Computacional (CFD), Turbinas Francis, Dispositivos passivos, Protuberâncias no bordo de ataque, Francis-99, Computational Fluid Dynamics, Francis turbines (CFD), Passive devices, Leadingedge tubercles