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May 13, 2020
Everyone knows that the hydroelectric generating set is the core key component machinery of the hydropower station. Therefore, it is very important to ensure the stable operation of the entire hydraulic turbine. There are many factors that affect the stability of the hydraulic unit, and there have been influencing factors since the design of the entire hydraulic unit. In the following we will introduce what specific factors affect the stability of the turbine.
In the design work of the entire hydraulic unit, the design influence of hydraulics is relatively small. When the water turbine unit is operating under normal operating conditions, the water flow at the runner outlet of the unit will continue to flow out, but the water flow at the runner outlet will not rotate. When the turbine is not in the optimal working state, the water flow at the runner outlet will gradually form a ring-shaped water flow in the tail pipe of the turbine. When the turbine is at a partial load of 40 to 70% of the low head, the water flow at the turbine runner outlet will be positive To rotate and gradually form a band-shaped vortex, which may even cause the vibration of the turbine unit.
In the operation of the hydraulic turbine, the most important factor causing the vibration of the hydraulic turbine is the pressure pulsation of the draft tube, and this factor will pose a threat to the normal operation of the Francis turbine. In addition, if a Karman vortex is generated at the tail of the airfoil, it will also affect the normal operation of the turbine, because it will cause forced vibration of the runner blades of the turbine. When the frequency of this forced vibration is When the vibration frequency forms a multiple relationship, it will cause cracks in the turbine runner blades, or even cause the blades to break.
In addition to this, there is another factor that also affects the stable operation of the turbine, that is, the hydraulic factor. If there is a deviation between the operation condition of the turbine unit and the design condition of the turbine, a deflow phenomenon will occur at the inlet and outlet of the blade. Frequency is unstable, so the degree of harm is also different. The hydraulic model of the turbine is the source of power for the entire hydropower station.
In addition to the hydraulic factors mentioned above, the pressure pulsation of the draft tube and the direction of the water flow at the runner outlet, the structural design and manufacturing of the hydraulic turbine unit are also the key factors affecting the stability of the hydraulic turbine generator set, and are also the main Optimization. We will introduce the specifics in the next article.