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Influence Of Guide Vane Airfoil On Runaway Characteristics And Unit Performance Of Pump-turbine

Posted on:2023-01-29Degree:MasterType:Thesis
Country:ChinaCandidate:Q Z MaFull Text:PDF
GTID:2532306809990879Subject:Power engineering
Abstract/Summary:PDF Full Text Request
The pumped-storage unit plays the role of peak regulation,phase regulation and other tasks in the power system.In order to meet the efficient operation of the power grid,the pumped-storage power station has become the mainstream means of energy storage and power grid regulation at present.The pump-turbine as the core component of pumped storage power station,its safety and stable operation is crucial.When pump-turbine load rejection,there may be the extreme case of guide vane rejection,in this case,the unit is easy to enter a state of runaway condition.When the runaway time of unit is too long,it is easy to cause the damage of the fixing bolt,which leads to the instability of the large shaft.When it is serious,it may be jacked up by the tail water,resulting in irreversible accidents such as flooding plant.It can be seen that the construction of pumped storage power station and the improvement of the operation stability of the reversible pump-turbine are very heavy tasks in China in the future,and the development potential is huge.Guide vane is an important water guide mechanism of pump-turbine,its hydraulic performance and structural strength will directly affect the efficiency and operation stability of the unit.At present,the research to improve the"S"characteristics,improve the stability of unit operation at the runaway condition and so on is less by changing the pump-turbine guide vane geometry structure.Based on this,this paper takes the guide vane airfoil of pump-turbine as the research object to explore its influence on the runaway characteristics and other hydraulic properties("S"characteristics,pressure,efficiency,radial force of runner,etc.)of pump-turbine.The conclusions are as follows:1.Based on the test bench of Harbin Institute of Electrical Machinery,the maximum relative error of numerical calculation and test results is within 3%,and the experimental error is within the allowable range.2.Improving the original guide vane airfoil of pump-turbine,establishing two different guide vane airfoil models,and analyzing the internal flow field of pump-turbine with opening of 11mm,33mm and 41mm respectively.The results show that the distribution of velocity streamlines in the guide vane and runner area is uniform,and the vortex core concentration distribution area is reduced after the improved guide vane airfoil.In the vaneless area,the annular water resistance phenomenon formed by high-speed water ring is obviously weakened,which makes the inlet liquid flow of the runner flow more smoothly and reduces part of the energy loss.The concentrated distribution area of vortex core in the draft tube is reduced,and the unit can operate in a relatively stable state.In addition,some small-scale vortices in the concentrated area of vortex core fall off and flow out with water,which is mainly due to the high-speed liquid flow at the runner outlet and the inlet of the draft tube impinging on the vortex core and promoting its downstream movement.3.The geometric structure of the guide vane airfoil B is further optimized,and different guide vane airfoil schemes are established.The Q11-n11curve and internal flow characteristics of pump-turbine under different schemes were analyzed.When reduce the head circle radius r of guide vane airfoil,the energy dissipation in the guide vane and runner area is the least,and the improvement effect on the"S"characteristics of pump-turbine is the most obvious.4.Analyzing the influence rule of head circle radius r of guide vane on hydraulic performance of pump-turbine,and establishing 6 schemes a,b,c,d,e and f through numerical calculation to analyse comparatively.It is found that the scheme e has the best improvement effect on"S"characteristics of unit,the streamline distribution is the most uniform and the high pressure area is the least in the guide vane and runner area.In scheme e,the resultant force of radial excitation force on the runner is the minimum,and the interference to the smooth operation of the unit is the minimum.5.Based on reducing the radius of the head circle of the guide vane airfoil from r to r-0.313mm,the flow characteristics of the pump-turbine in the vaneless area,runner and draft tube during its operation under runaway conditions were analyzed:(1)The local high pressure is generated in the vaneless area,the outlet of the guide vane and the inlet of the runner due to the rotating flow of the vortex;Vortices with different scales are uniformly distributed at the runner inlet,and the pressure in the vortex region varies with the position shift and intensity of the vortices.The vortex structure in the runner of pump-turbine not only affects the pressure and velocity fluctuation of the flow field inside the runner,but also affects the force of the runner blade,thus causing more complex vibration phenomenon,which poses a serious threat to the service life of the runner and the safe and stable operation of the pump-turbine.(2)Affected by the vortex structure,the fluid will produce backflow at the front of the diffusion section of the draft tube,which will interfere with the normal outflow of water in the draft tube,and part of it will gather and swirl in the draft tube,affecting the outflow rate and hydraulic characteristics of the pump-turbine.The closer to the elbow section of the draft tube,the more complex the flow pattern and the more backflow.Moreover,the pressure distribution of the characteristic section presents gradient diffusion.The closer the characteristic section is to the outlet position of the draft tube,the smaller the change amplitude of the fluid pressure gradient is,and the more stable the pressure change is.The pressure gradient change of the characteristic section which is 600mm away from the central axis to the runner of pump-turbine is the least.
Keywords/Search Tags:Pump-turbine, Guide vane airfoil, Guide vane head circle radius, Runaway characteristics, High-speed water ring
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