| As the core component of the power flow capture device,the performance of the blade plays a decisive role in the power generation efficiency of the turbine.The rise of bionics provides a new idea for the design of the turbine blade.Therefore,based on the full study of the humpback whale fin structure,this thesis designs the bionic blades with different parameters,and uses the STAR-CCM+ software for numerical simulation,so as to select the bionic blades with better performance and apply them to the horizontal axis tidal current turbine.Considering the practical application of offshore water,the linear shear flow field suitable for horizontal axis turbine is further established,and the performance variation of bionic turbine in shear flow field is deeply discussed,which provides a reference for subsequent development and research.In this thesis,several groups of bio-mimetic blades with different nodule parameters were designed.The numerical simulation results show that the hydrodynamic performance of the bio-mimetic blade has a certain lift loss compared with the standard blade at a small Angle of attack,but the hydrodynamic performance of the bio-mimetic blade at a large Angle of attack(?>22°),the bionic blade has a higher lift coefficient and lift-drag ratio,among which,the bionic blade with large nodular height has a larger lift coefficient at a large Angle of attack,while the lift-drag ratio of the blade with fewer nodules is relatively small.Then,the bionic blade with better performance is applied to the horizontal axis tidal power turbine,and the standard blade without nodules at the leading edge is used to establish a standard horizontal axis tidal power turbine model to study the performance difference between the two in the uniform flow field.Under different pitch angles,the bionic blade mainly has a great influence on the torque coefficient and energy utilization rate of the turbine in the low point ratio area(i.e.,the point ratio is between 2 and 3).When the pitch Angle is greater than 5,there is a certain improvement in the high tip ratio area(that is,the tip ratio is between 6 and 7),but the improvement effect is not as significant as that in the low tip ratio area.With the increase of the pitch Angle,the optimal energy utilization rate of the turbine moves to the low tip ratio area,and the torque coefficient and energy utilization rate decrease overall.Finally,after simplifying the shear flow model,three kinds of linear shear flow fields with shear rate k=0(uniform flow)k=0.04 and k=0.05 are established,which are suitable for horizontal axis turbine.Through numerical simulation,it is found that the flow field with different shear rate has little influence on the standard turbine,and the torque coefficient and energy utilization rate of the bionic turbine vary greatly in different shear flow field,especially in the high tip ratio area of the flow field k=0.05,and the energy utilization rate of the torque coefficient is greatly improved.The torque coefficient and energy utilization ratio of the bionic turbine in each flow field are greatly improved compared with the standard turbine in the low and high point ratio area,but the axial force coefficient is always higher than that of the standard turbine.That is to say,compared with the standard hydraulic turbine,the bionic hydraulic turbine is more adaptable to the shear flow field and easier to start than the standard hydraulic turbine.The energy conversion efficiency is improved more in the flow field with high shear rate,but the requirements for the strength of the supporting structure are also higher. |
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