Research On Aerodynamic Performance Of A Nested Inverted Vertical Axis Wind Turbine

With the development of human society and the progress of scientific and technological level,the traditional energy(coal,natural gas,oil,etc.)is constantly consumed,and the development and utilization of renewable energy has received increasing attention.Wind energy plays a very important role in the development of new energy,Vertical axis wind turbine is an important research direction for the development of green energy in the future because of its simple structure,strong adaptability to wind direction,reasonable force and low installation and maintenance cost.Taking it as a distributed energy supply unit can further enrich energy supply methods and improve energy utilization efficiency.Because of its simple appearance,H-type vertical axis wind turbine can more obviously reflect the aerodynamic performance and cycle characteristics of vertical axis wind turbine.Therefore,most studies on aerodynamic performance of vertical axis wind turbine take H-type vertical axis wind turbine as the research object.In this paper,aiming at the dynamic stall characteristics of H-type vertical axis wind turbine,the nested inverse rotor geometry is adopted,and the influence of geometric configuration and speed difference of internal and external wind turbines on aerodynamic performance is studied by numerical simulation,and the single wind energy utilization efficiency of Htype vertical axis wind turbine is improved by adjusting parameter values.The main contents of this paper are as follows:(1)A traditional vertical axis wind turbine was numerically simulated based on RANS SST k-co turbulence model and SIMPLE algorithm,and the experimental results were compared With the published data to analyze the aerodynamic performance of wind turbine blades to verify the model grid and time step independence,and the grid size and time step were determined in this paper.(2)The degree and process of the influence of the inner blade on the aerodynamic performance of the outer blade are analyzed.Based on the fixed chord length,the stress conditions of four groups of models with different chord length ratios of the inner and outer blades are simulated and calculated in this paper,and the results are compared and analyzed to study the influence of the chord length ratio of the inner and outer blades on the aerodynamic performance,which mainly exists in the downstream area.The vortex generated by the shedding of the inner blade collides with the outer blade and influences the formation and shedding of the separation vortex on the outer blade surface.Moreover.the influence of the inner blade on the aerodynamic performance of the outer blade is positively correlated with its chord length.(3)The influence of the inner vane on the outer vane in the upstream region is studied.The velocity field and pressure field of the nested inverted vertical axis wind turbine under different rotation radii of the inner vane are simulated and calculated.The flow field when the inner vane and the outer vane meet in the upstream region is compared and analyzed,and the mechanism of the influence of the inner vane on the outer vane in the upstream region is defined.The effect of the ratio of inner and outer blade rotation radii on aerodynamic performance is studied.It is found that when the inner and outer blades intersect in the upstream region,the inner wind turbine can affect the separation vortex shedding of the outer blade and the enrolling of the separation vortex by the tip vortex,but this phenomenon is not positively correlated with the inner wind turbine radii.(4)In order to further improve the single wind energy utilization efficiency of the nested inverted vertical axis wind turbine,the assumption of changing the inner wind turbine speed is put forward in this paper,and the change of wind energy utilization efficiency under the conditions of 1 to 2.5 times of 7 different inner and outer wind turbine speed ratios is studied.The effect of rotational speed difference of internal and external wind turbines on aerodynamic performance is studied.It is found that the integral multiple of rotational speed of internal and external wind turbines has stronger regularity in the flow field between the two wind turbines,and the wind energy utilization in the downwind area is more regular and the wind energy utilization efficiency is higher.(5)In order to analyze the adaptability of the nested reverse vertical axis wind turbine under different working conditions,the wind energy utilization efficiency of the traditional vertical wind turbine,the nested reverse vertical axis wind turbine with the inner and outer wind turbine rotational speeds of 1:1 and the nested reverse vertical axis wind turbine with the inner and outer wind turbine rotational speeds of 2:1 were compared and analyzed in this paper under seven different working conditions from 1 to 2.4.The adaptability of the nested reverse vertical axis wind turbine under different tip speed ratios is studied.It is found that the increase of the inner wind turbine speed has a positive effect on the available tip speed ratio interval and the wind energy utilization efficiency at the optimum tip speed ratio.