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데이터베이스 기반 프란시스 수차 러너 두께 설계 및 수치해석적 연구
노민수(Min-Su Roh),모하메드 아부 사져(Mohammad Abu Shahzer),김진혁(Jin-Hyuk Kim) 한국에너지학회 2024 에너지공학 Vol.33 No.1
In this study, a high-efficiency Francis turbine was designed using a database-driven approach for the runner thickness of a prototype Francis turbine with a specific speed in the 170-class. Numerical analysis was carried out to investigate the hydraulic performance and internal flow characteristics of the turbine. The runner blade thickness database was constructed by normalizing data from models with specific speeds of 150, 210, and 270-classes. The thickness distribution data was obtained through interpolation and encompasses information from the runner inlet to the outlet at the hub, mid, and shroud spans. Subsequently, Reynolds-averaged Navier-Stokes (RANS) equations were employed in numerical simulations to accurately analyze the hydraulic performance and characteristics of the internal flow field of the Francis turbine. The Grid Convergence Index (GCI) method, utilized as a grid independence test, was used to select the optimal grid system, ensuring both the accuracy and cost effectiveness of the numerical analysis. The numerical results confirmed the feasibility of designing a Francis turbine operating at an efficiency of 93.63% and an output of 30.71MW. The internal flow analysis revealed that the runner exhibited a uniform velocity component across all span regions, without any observed unstable flow characteristics, such as flow separation at the runner inlet and outlet areas. Additionally, there was no blockage effect disrupting the flow within the runner, and uniform flow characteristics were confirmed throughout all spans. The analysis of the flow field in the draft tube downstream of the runner indicated a stable flow distribution and pressure profiles, thereby establishing the reliability of the database-driven approach for designing the runner thickness of the Francis turbine with a specific speed in the 170-class, as utilized in this study. The findings of this research can be applied in the future design of turbines across different specific speed ranges.