文章基本信息

标题：Self-validated calculation of characteristics of a Francis turbine and the mechanism of the S-shape operational instability
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作者：Z Zhang ; M Titzschkau
期刊名称：IOP Conference Series: Earth and Environmental Science
印刷版ISSN：1755-1307
电子版ISSN：1755-1315
出版年度：2012
卷号：15
期号：3
DOI：10.1088/1755-1315/15/3/032036
出版社：IOP Publishing
摘要：A calculation method has been presented to accurately estimate the characteristics of a Francis turbine. Both the shock loss at the impeller inlet and the swirling flow loss at the Impeller exit have been confirmed to dominantly influence the turbine characteristics and particularly the hydraulic efficiency. Both together totally govern the through flow of water through the impeller being at the rest. Calculations have been performed for the flow rate, the shaft torque and the hydraulic efficiency and compared with the available measurements on a model turbine. Excellent agreements have been achieved. Some other interesting properties of the turbine characteristics could also be derived from the calculations and verified by experiments. For this reason and because of not using any unreliable assumptions the calculation method has been confirmed to be self-validated. The operational instability in the upper range of the rotational speed, known as the S-shape instability, is ascribed to the total flow separation and stagnation at the impeller inlet. In that range of the rotational speed, the operation of the Francis turbine oscillates between pump and turbine mode.