| With the in-depth study of the flow field characteristics of wind turbines,optimizing the aerodynamic performance of wind turbines and improving the efficiency of wind energy utilization are the current research hotspots of wind turbines.In this paper,the double-forked tip structure of Boeing 737MAX wing is taken as the design idea of wind turbine tip modification,and a double-forked tip structure wind turbine model is designed by Wilson method.Numerical calculation is carried out by means of computational fluid dynamics,and the accuracy of numerical calculation is verified by wind tunnel experiment.The main research contents and conclusions are as follows:Based on the unsteady incompressible N-S equation and realizable k-ε turbulence model,the aerodynamic characteristics of a double-forked blade tip wind turbine are numerically calculated using the structured grid in ICEM.The calculation results of Fluent show that:The double-forked blade tip structure can increase the output power of wind turbine;at the rated wind speed of 1Om/s,the power coefficients of the double-fork tip wind turbine with 0=300 and 0=600 are 1.47%and 3.68%respectively compared with the non-modified θ=0° wind turbine;Compared with the non-modified 0=00 wind turbine,the torque coefficient of the double-fork tip structure 0=300 and 0=600 wind turbine increases by 3.23%and 6.45%respectively.The results of numerical calculation are used to analyze the three-dimensional flow field of the wake of the wind turbine with double-forked tip structure.It is found that the double-forked tip structure increases the blade pressure difference.At the blade tip,the pressure difference between the upper fork and the lower fork of the double-fork blade tip structure wind turbine is less than that of the unmodified wind turbine blade,but the sum of the pressure difference between the upper fork and the lower fork is greater than that of the unmodified wind turbine blade.The double fork blade tip structure increases the blade tip linear velocity,which is equivalent to that the diffuser can play the role of gathering wind,thus increasing the output power of the wind turbine.Because the pressure difference between the upper fork and the lower fork of the double-forked blade tip wind turbine is less than that of the unmodified blade,the vortex magnitude of the blade tip is reduced.Meanwhile,the upper fork and the lower fork of the double-forked blade tip structure also hinder the tip turbulence and scatter the tip vortex into two vortex systems and reduce the vortex magnitude.Under the condition of variable inlet wind speed,the absolute value of positive pressure on the pressure surface and negative pressure on the suction surface of the double-fork blade tip wind turbine increases with the increase of wind speed,but the change of incoming wind speed has a greater impact on the negative pressure on the suction surface of the double-fork blade tip wind turbine.With the increase of wind speed,the vortex value of wake tip of double-forked blade tip structure will increase,while the shedding frequency will decrease.In conclusion,the aerodynamic characteristics of the flow field of the modified double-fork blade tip structure θ=60° are the best.The wind tunnel and hot-wire probe were used to measure the velocity of the wake flow field of a double-forked blade tip wind turbine.There is a three-dimensional velocity field in the wake flow field.The velocity of the wake flow field of the double-forked blade tip structure wind turbine increases gradually from the center to the blade tip,which is similar to the axial velocity variation trend,and the tangential velocity and radial velocity are fluctuating.There are some errors between the experimental results and the numerical simulation results,but the development trend is consistent. |
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