Numerical Analysis of Combined Leakage-Main Flows in Francis Turbine Part 1: Leakage through Clearance around Runner-Band

• Published in: Turbomachinery Vol. 33; no. 4; pp. 214 - 222
• Main Authors: XIAO, Ruofu, WEI, Caixin, HAN, Fengqin, KUBOTA, Takashi
• Format: Journal Article
• Language: English; Japanese
• Published: Turbomachinery Society of Japan 2005
• Subjects: CFD Analysis; Discharge Loss; Dissipation of Kinetic Energy; Francis Turbine; Hydraulic Loss; Leakage Flow; Power Loss; Runner Band
• ISSN: 0385-8839; 1880-2338
• DOI: 10.11458/tsj.33.214

The specific energy efficiency ηε of a Francis turbine can be predicted by the 3-D numerical analysis of the main flow through the turbine from the spiral case inlet to the draft tube outlet. In order to predict the discharge efficiency ηQ and the power efficiency ηp of the turbine, it is necessary to perform the 3-D numerical analysis of the leakage flow through the clearances around the runner, under the inflow and outflow conditions for the clearances defined by the main flow analysis. Moreover, a lump-sum analysis of the combined leakage-main flows is prerequisite to investigate the interaction between the leakage flow and the main flow in the turbine. The aim of a series of the papers is to clarify the effect of leakage flows along the runner band and crown on the main flow through the medium-high specific speed Francis turbine. This paper focuses on the numerical analysis of leakage flow through the clearance around the runner band to evaluate the discharge and power efficiencies.