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May 18, 2020
In the previous article we introduced the factors that affect the stability of the hydro-generator set. The unstable operation of the turbine unit will cause problems such as vibration of the turbine unit. The severe vibration of the turbine unit will have serious consequences and even affect the safety of the entire plant. Therefore, the stability optimization measures of the turbine are very important. What are the optimization measures?
(1) Constantly optimize the hydraulic design of the turbine, improve its performance design in the turbine design, and ensure the stable operation of the turbine. Therefore, in actual design work, designers not only need to have solid professional knowledge, but also combine their own work experience, and strive to optimize the design.
At present, computational fluid dynamics analysis technology (CFD) and model tests are widely used. In the design stage, the designer must combine the work experience, use CFD and model tests in the work, continuously optimize the guide vane airfoil, runner blade airfoil and drain cone, and try to reasonably control the amplitude of draft tube pressure fluctuation. At present, there is no unified standard for the amplitude range of draft tube pressure pulsation. Normally, high-head power plants have lower speeds and smaller vibration amplitudes, but low-head power plants have higher speeds and relatively larger amplitudes of pressure pulsations.
(2) Strengthen the quality control of turbine products and improve the level of overhaul and maintenance. In the design stage of the turbine, strengthening the quality control of the turbine product is also an important way to improve its operational stability. In this regard, first of all, the rigidity of the flow components of the turbine should be improved to minimize its deformation under the action of hydraulics. In addition to this, the designer should also fully consider the possibility of resonance at the natural frequency of the draft tube and the frequency of the water flow vortex and the natural frequency of the runner at low loads during the design stage.
In addition, the blade transition part should be scientifically designed. For the local strengthening of the blade root, the finite element analysis method should be used to reduce the stress concentration. In the manufacturing stage of the runner, rigorous manufacturing process should be adopted, and stainless steel should be used in the material. Finally, three-dimensional software should also be used to design the runner shape to control the blade thickness. After the runner is processed, a balance test should be carried out to avoid weight deviations and improve balance. In order to better guarantee the quality of the turbine, it is necessary to strengthen its later maintenance.
These are some of the measures to optimize the stability of the hydraulic turbine. For the optimization of the stability of the hydraulic turbine, we should start from the design stage and combine the actual situation and work experience to continuously optimize and improve in the model test. In addition, what other measures do we have to optimize stability in use? Our next article continues.