Now let us talk the first reason: Hydraulic Reasons
Hydroelectric generating units because of hydraulic factors caused by vibration mainly in the subsequent instances. First, the turbine from the non-design conditions to operate the vibration. When the turbine reaches the no-load, low mind, little load, higher head, overload and high flow of this operating condition, in addition to the pressure of the fluid load, but also bear the pressure pulsation and circadian rhythms caused by the dynamic load. Secondly, the pressure vortex generated by the vortex belt in the draft tube. Since the Francis turbine is a fixed-blade hydraulic system, when the toaster is emptied from the best operating conditions, because the rotor outlet water flow has a rotational circumferential speed, a large vacuum seems in the area close to the tail pipe radius below the runner, When the vacuum reaches the fixed value after the cavity cavitation cavitation, the vortex is a coil around the tail pipe axis of this unstable rotation, will cause the unit vibration, and the tail pipe includes a substantial damage. Third, the telescope spinning and fixed region of the gap caused by uneven pressure pulsation. Due to the uneven rotation of the telescope as well as the fixed part of the gap so the center of the wheel away from the center of the unit, the wheel around the circumference of the rotating and fixed maze ring gap with the rotation of the wheel is continually changing, the gap between the water pressure also changes across the wheel The integral of this hydraulic pressure, there's a role from the runner around the transverse water pressure of this force, the force is always forced to additional change the center of the wheel centre, impair vibration. Four vortex caused by vibration. After the flow around the stream of leaves, in the exit side of the flow, it will make a vortex at the exit side, in the front and back of the blade alternately appear to form the impact of alternating leaves. When the natural frequency of the blade and also the frequency of the same hit, it is going to resonate. Five is the hydraulic imbalance brought on by stress pulsation. When the water flow to the runner is axially symmetrical, an unbalanced lateral force occurs, causing the wheel .
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