| China has a long coastline and rich tidal energy resources in offshore areas.The development prospect of tidal power generation is becoming better and better.However,the generation of cavitation will cause great damage to the blade,which will directly affect the power generation efficiency and operation stability of the unit.In addition,in the sediment-containing sea area connecting to the estuary,the abrasion of sediment will also cause serious damage to the unit.At present,there is still a lack of research results on the cavitation and erosion problems of tidal current energy turbine blades.Most of them are studies on traditional hydraulic generating units and focus on experimental studies,lacking research content in numerical simulation calculation.Based on the above problems,this paper uses computer simulation technology to numerically simulate the blades of bidirectional direct-drive tidal current turbine,and analyzes the flow field distribution around the blades and the pressure distribution of the blades.Combined with the development of bubbles around the blades under different working conditions,the prone area of cavitation is determined,and then the qualitative analysis is used to determine whether the region has the conditions to meet the occurrence of cavitation.Based on the theoretical basis,the influence of airfoil structure on the cavitation resistance of turbine blades was studied,so as to provide reference for the optimization design of blade cavitation resistance.The erosion rate and volume fraction of particle phase of the blade under different working conditions were calculated to determine the severely damaged parts of the blade and evaluate the erosion performance.The details are as follows: 1)Taking the rated power 200 W AC tidal turbine of Shanghai Marine Renewable Energy Technology Research Center as the research carrier,the 3D model with the ratio of 1: 1 is constructed by Solid Works,the model data is derived,and the research object is meshed by ICEM.2)The cavitation performance of turbine blades was studied.The RNG k-ε turbulence model combined with Schnerr-Sauer transport cavitation model was used for simulation,and the calculation results were analyzed.3)For the optimization of blade anti-cavitation performance,at the beginning of the design,the pressure coefficient was used as the evaluation criterion to study the anti-cavitation performance differences of airfoil types,attack angles and “S” structure,and the calculation results were analyzed.4)The k-ε turbulence model combined with Finnie model was used to simulate the erosion of the turbine blade,and the erosion of the turbine blade under different sediment concentrations,different sediment particle sizes and different erosion velocities was obtained.The particle volume fraction distribution and the maximum erosion rate were used to determine.The results show that the bubbles at the edge of the blade are well developed,especially in the negative pressure area near the edge of the hub on the back of the blade,which is the key area for cavitation.With the increase of impeller speed,the more sufficient the bubble develops,the larger the impact range caused by the bubble burst at the same time.Different types of airfoils have different anti-corrosion performance.The larger the curvature and thickness of the blade airfoil,the smaller the pressure coefficient,the better the anti-corrosion performance of the airfoil.With the increase of angle of attack,the pressure coefficient also increases,and the possibility of cavitation will increase.The “S” airfoil not only has better lift and drag characteristics,but also has better cavitation resistance characteristics.The “S-shaped” symmetrical structure of the blade leads to the concentration of erosion in half of the blade.Under the action of centrifugal force,the edge of the blade is greatly affected by erosion.The particle volume fraction of the blade upstream surface decreases gradually from the direct impact position in the middle of the blade to the surrounding,and the solid particles moving to the edge of the blade have high impact pulsation energy.The coupled velocity of water flow and particles is one of the main factors that cause erosion damage.When the particle concentration is constant,the erosion damage increases almost in multiples with the increase of flow velocity.The larger the particle size,the more obvious the damage effect is,and the large particle size plays a leading role in the erosion damage.The particle concentration is also one of the factors affecting the erosion performance.When the flow velocity is 1 m/s,the erosion damage caused by the particle concentration has little effect.With the increase of the flow rate,the destructive effect of the water flow with high concentration of solid particles is more obvious;the above simulation of cavitation and erosion of the turbine blade can provide the optimal design of the anticavitation and erosion performance of the blade to a certain extent.Reference. |
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