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首页> 外文期刊>Journal of Fluids and Structures >Experimental investigation of added mass effects on a Francis turbine runner in still water
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Experimental investigation of added mass effects on a Francis turbine runner in still water

机译：静水中混流​​式水轮机转轮附加质量效应的实验研究

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摘要

The mechanical design of hydraulic turbines is conditioned by the dynamic response of the runner that is usually estimated by a computational model. Nevertheless, the runner has complex boundary conditions that are difficult to include in the computational model. One of these boundary conditions is the water in which the runner is submerged. The effect of the added mass and damping of water can modify considerably the natural frequencies of the runner. An experimental investigation in a reduced scale model of a turbine runner, using modal analysis, was carried out. Several impact tests with the runner freely suspended in air and in water were done. The response was measured with accelerometers located in different positions of the runner. From the modal analysis, the natural frequencies, damping ratios, and mode-shapes were determined. The same mode-shapes obtained in air were obtained in water but with lower natural frequencies and higher damping ratios in water. The difference in the natural frequencies is shown to be dependant basically on the added mass effect of the water and not on its added damping. This difference also depends on the geometry of the mode, presenting different values for different mode-shapes. Using nondimensional values, the reduction in the natural frequencies can be extrapolated to other Francis runners presenting similar geometrical characteristics.
机译：水轮机的机械设计取决于通常由计算模型估算的转轮动态响应。但是，跑步者具有复杂的边界条件，很难将其包括在计算模型中。这些边界条件之一是赛跑者被淹没的水。附加质量和水阻尼的影响会大大改变转轮的固有频率。使用模态分析对涡轮机转子的缩小模型进行了实验研究。在跑步者自由悬挂在空气和水中的情况下，进行了几次冲击测试。用位于转轮不同位置的加速度计测量响应。通过模态分析，确定了固有频率，阻尼比和模态形状。在水中可获得与空气中相同的振型，但在水中具有较低的固有频率和较高的阻尼比。结果表明，固有频率的差异主要取决于水的附加质量效应，而不取决于水的附加阻尼。这种差异还取决于模式的几何形状，为不同的模式形状提供不同的值。使用无量纲值，固有频率的降低可以外推到具有类似几何特征的其他弗朗西斯选手。

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