Design Of Hydrofoil And Impeller For Half-rotating Impeller Tidal Turbine

In order to achieve the goal of ecological protection,the development and utilization of new energy was increased in China.Tidal current energy is a regular and stable new marine energy,which has a broad space for development.Half-rotating impeller tidal turbine(HRITT)is a new type of tidal current power generation equipment with high efficiency.Because of a special structure,the HRITT can be applied to the low-speed flow of ocean and river in China.Studies have shown that the HRITT has an efficient energy utilization rate,but the efficiency of the energy output by the impeller can be further improved,and the output power fluctuates greatly.Therefore,in order to solve the problem of the output power of the HRITT,the power performance(including the efficient energy utilization and the output power stability)of the turbine was proposed as the performance index in this paper.The hydrofoil of blades and the impeller structure were designed for the HRITT to improve the power performance.The main research contents of this paper include the following:Firstly,the HRITT,as the object of the study,and the half-rotating impeller(HRI)was introduced.The power performance and research methods of the vertical axis turbine was described.The numerical experiment method and analysis method based on XFlow software was described.Secondly,the hydrofoil of the HRITT was designed by referring to the reversible hydrofoil by analyzing the motion process of the HRI.The effects of two types of reversible hydrofoils on the power performance of HRITT were studied by classification of reversible hydrofoils,and the effect of hydrofoils on the HRITT was analyzed from the flow field.The results shown that the sharp anteroposterior edges are conducive to inhibiting the tail vortex and improving the power performance of the HRITT.The profile difference between the upper and lower surfaces of hydrofoils is favorable for improving the extra output torque of the HRI and improving the efficient energy utilization of the HRITT.Although the double-headed asymmetrical airfoil can improve the efficient energy utilization of the HRITT.,the rhombic hydrofoils improve the efficient energy utilization and improves the output power stability of the HRITT.Thirdly,the effect of structure parameters of the HRI on the power performance of HRITT.was studied.The effect of the aspect ratio on the power performance of the HRITT was studied.The relationship between chord-diameter ratio and compactness of HRITT and the influence of chord-diameter ratio on the power performance of HRITT were analyzed.The effect of the scale on the HRI was analyzed.The effect of the change of the aspect ratio on the HRITT was studied.The relationship between the chord-diameter ratio and the compactness of the HRITT and its influence was analyzed.The variation law of the tip ratio of the HRI was also explored,and the influence of the scale on the hydrodynamic performance of the HRI was analyzed.The results shown that with the increase of the scale-to-chord ratio,the efficiency of the HRITT increased,and the output power stability decreased.With the increase of the chord-to-diameter ratio,the compact structure of the HRI,the energy utilization efficiency of the HRITT increased,and the output power stability of HRITT increased.The similarity criterion was applied to HRIs.And the model with a smaller scale at the same flow rate had a higher adaptive speed,and the prototype with a larger scale had a smaller adaptive speed.Then,in order to eliminate the influence of the tip vortex,a design method for the end-plate of the HRITT was proposed.The use of end plates suppresses the tip vortex and the power performance of the HRITT was improved.The results show that through the end-plate,the energy utilization efficiency of the HRITT was improved,but the fluctuation of the HRI cannot be suppressed and the output power stability of the HRITT cannot be improved.The energy utilization efficiency of the HRITT of different airfoils was affected by the end-plate,the tail vortex elimination was different,and the power performance of the HRITT was different.The energy utilization efficiency of the HRITT was increased more significantly by the addition of roulette end-plates than the addition of the blade end-plates.Finally,the HRITT studied in the previous paper was designed and manufactured,and the high efficiency and low fluctuation of the new blade HRITT were verified by experiments.At the same time,through the reliability analysis of the blades,the complex hydrofoils had better strength and stiffness.