For a hydro-generator set, any periodic motion beyond a constant speed rotation is additional vibration. In terms of direction, there are three types of vibration of the unit:
(1) Axial vibration, vertical units appear to jump up and down; horizontal units appear to move forward and backward.
(2) Radial vibration, manifested as rocking in a direction perpendicular to the axis.
(3) Torsional vibration around the axis is manifested as uneven rotation, and the angular velocity of the unit periodically increases and decreases.
So what are the impacts and harms of the turbine vibration? The following Hydraulic Turbine Generator Supplier will tell you.
For hydro-generator units, in addition to consuming a portion of power to reduce the efficiency of the unit, it will also bring a series of adverse effects, and even endanger normal operation and unit safety.
(1) The rotating part and bearing of the unit are subject to periodic alternating forces, which cause bolts to loosen, welds to crack, and even damage the main shaft due to material fatigue.
(2) The bearings, frames, anchor bolts, connecting bolts, etc. of the fixed part of the unit will be deformed and loose due to vibration.
(3) The frequency and waveform of the output of the unit will change due to vibration, reducing the quality of power supply.
(4) Severe vibration will also destroy the stability of the unit operation, making the unit unable to operate.
Reasons that cause unit vibration
The causes of the vibration of the hydro-generator set are many and complicated. In general, it can be analyzed from the following three aspects:
1. Hydraulic reasons
The water turbine is the source of power for the rotation of the unit, and its unstable operation will inevitably affect the entire unit. In terms of turbines and passing water, the main common problems are:
(1) Hydraulic imbalance around the runner. The gap between the upper and lower leak-tight rings of the mixed-flow runner is uneven; the gap between the axial-flow runner and the runner chamber is not uniform, which inevitably makes the runner oscillate by the lateral force.
The wrap angle of the concrete volute is too small, and the cross-section design is not reasonable. The uneven opening of the Casting Guide Vane will make the water inflow around the runner uneven. In some power stations, the guide vanes were blocked by foreign matter during the trial operation, which caused the unit to vibrate violently.
(2) Guide vanes or vanes produce unstable eddy currents. Under certain conditions, a series of unstable vortices will be generated behind the guide vanes or vanes, called "Carmen Vortex". They make the guide vanes or blades unstable and cause vibration. When this vibration causes the unit to resonate, it will show a strong vibration phenomenon. This usually varies from unit to unit and occurs only in the vicinity of a certain output.
(3) Units with high heads and long water pipelines may cause vibration due to water hammer when the load changes. At this time, the pressure in the pressure pipe fluctuates up and down, and the hydraulic head of the hydraulic turbine is unstable, so the unit vibrates for a period of time.
2. Electrical reasons.
Generators, power grids, and consumers of electrical energy are the load of the unit, and the instability of their power consumption will inevitably affect the unit.
Unit manufacturing or installation failure caused unit vibration, and this is exactly the issue that people are most concerned about during the start-up and trial operation of the unit. Once mechanical vibrations are identified, specific problems must be identified and resolved as best as possible.
The above is the phenomenon and reason of the turbine vibration introduced by Francis Turbine supplier, I hope to help everyone.