The unstable operation of hydraulic turbine unit will lead to vibration of hydraulic turbine unit. When the vibration of hydraulic turbine unit is serious, it will have serious consequences and even affect the safety of the whole plant. Therefore, the stability optimization measures of hydraulic turbine are very important. What optimization measures are there?
1) Continuously optimize the hydraulic design of the water turbine, improve its performance design in the water turbine design, and ensure the stable operation of the water turbine. Therefore, in the actual design work, designers not only need to have solid professional knowledge, but also strive to optimize the design combined with their own work experience.
At present, computational fluid dynamics (CFD) and model test are widely used. In the design stage, the designer must combine the work experience, use CFD and model test in the work, constantly optimize the guide vane airfoil, runner blade airfoil and discharge cone, and try to reasonably control the pressure fluctuation amplitude of draft tube. At present, there is no unified standard for the amplitude range of draft tube pressure fluctuation in the world. Generally, the rotating speed of high head power station is low and the vibration amplitude is small, but the specific speed of low head power station is high and the pressure fluctuation amplitude is relatively large.
2) Strengthen the quality control of water turbine products and improve the maintenance level. In the design stage of hydraulic turbine, strengthening the product quality control of hydraulic turbine is also an important way to improve its operation stability. Therefore, firstly, the stiffness of the flow passage parts of the hydraulic turbine should be improved to minimize its deformation under hydraulic action. In addition, the designer should also fully consider the possibility of resonance of draft tube natural frequency and the frequency of flow vortex band and runner natural frequency at low load.
In addition, the transition part of the blade should be designed scientifically. For the local reinforcement of the blade root, the finite element analysis method should be used to reduce the stress concentration. In the stage of runner manufacturing, rigorous manufacturing process should be adopted, and stainless steel should be used in the material. Finally, three-dimensional software should be used to design runner modeling and control blade thickness. After the runner is processed, the balance test shall be carried out to avoid weight deviation and improve the balance. In order to better ensure the quality of hydraulic turbine, its later maintenance must be strengthened.
These are some measures for the stability optimization of hydraulic turbine unit. For the stability optimization of hydraulic turbine, we should start from the design stage, combine the actual situation and work experience, and constantly optimize and improve it in the model test. In addition, what measures do we have to optimize the stability in use? Let’s continue in the next article.
How to improve and optimize the stability of hydro generator units in use.
During the use of water turbine, its blades, runner and other components will gradually suffer cavitation and abrasion. Therefore, it is necessary to detect and repair the water turbine regularly. At present, the most common repair method in the maintenance of hydraulic turbine is repair welding. In the specific repair welding work, we should always pay attention to the deformation of deformed components. After the repair welding work is completed, we should also carry out nondestructive testing and polish the surface smooth.
Strengthening the daily management of hydropower station is conducive to ensure the normal operation of hydraulic turbine unit, and improve its operation stability and work efficiency.
① The operation of water turbine units shall be managed in strict accordance with relevant national regulations. Hydropower stations generally have the task of frequency modulation and peak shaving in the system. In a short time, the operating hours outside the guaranteed operating range are basically unavoidable. In practical work, the operating hours outside the operating range should be controlled at about 5% as far as possible.
② Under the operation condition of the water turbine unit, the vibration area should be avoided as far as possible. Francis turbine generally has one vibration zone or two vibration zones, so in the startup and shutdown stage of turbine, the method of crossing can be adopted to avoid the vibration zone as far as possible. In addition, in the daily work of the water turbine unit, the number of startup and shutdown should be reduced as much as possible. Because in the process of frequent startup and shutdown, the turbine speed and water pressure will change continuously, and this phenomenon is extremely unfavorable to the stability of the unit.
③ In the new era, science and technology are developing rapidly. In the daily operation of hydropower stations, advanced detection methods should also be used to monitor the operation status of water turbine units in real time to ensure the operation stability of water turbine.
These are the measures to optimize the stability of hydro generator units. In the actual implementation of optimization measures, we should scientifically and reasonably design the optimization scheme according to our specific actual situation. In addition, during the normal overhaul and maintenance, pay attention to whether there are problems in the stator, rotor and guide bearing of the water turbine unit, so as to avoid vibration of the water turbine unit.
Post time: Sep-24-2021
