Wind Tunnel Test Study On Wake Flow Field And Power Characteristics Of Wind Turbine In Sand-wind Environment

North China and northwest China are rich in wind resources and frequent dust weather.Wind power develops rapidly and has great potential.It is of great significance to the research of wind turbine technology in the unique climate environment of North China and northwest China.From Lanzhou University multi-function environmental wind tunnel,this paper constructed the uniform to shed wind environment atmosphere boundary layer flow field,clean environment and atmospheric boundary layer wind environment,with independent design of wind turbine as the research object,research: the uniform flow field,different flow to tip speed ratio under different wind speed runtime wake flow field characteristics of wind turbine;The wake field and power characteristics of wind turbines in different atmospheric boundary layers reveal the interaction between wind turbines and dust in wind-sand environment.Through the study of the influence of wind turbine on the dust transport under uniform flow,it is found that the dust movement behind wind turbine is mainly axial;Under the condition of single hole sand,the distribution characteristics of sand transport rate conform to gaussian distribution.The smaller the dust particle size range,the smaller the particle size,the larger the wind speed,the more tends to gaussian distribution.The higher the wind speed is,the slower the wake recovery is.Wind turbine wake has symmetry;Near the wake,the larger the tip velocity ratio is,the more chaotic the flow field is and the more obvious the velocity deficit is.In a certain wind speed,the effect of wind turbine on dust obstruction becomes obvious with the increase of wind speed.The higher the wind speed is,the more obvious the gathering phenomenon of vortex to sand is,and the more obvious the blowing sand is.The influence range of tip vortex on dust accumulation is larger than that of central vortex.The larger the blade tip speed ratio is,the dust deposits in advance,the longer the distance of dust carried,the more obvious the gathering effect of vortex on dust,the less dust carried by the upper part of wake behind the wind turbine,and the more obvious the wind turbine’s hindrance effect on dust.Wind turbine operation will hinder dust transport,dust with large particle size deposition faster,and dust with small particle size is easier to follow wake transport.The larger the particle size is,the more obvious the obstruction effect of wake field on sand dust is.The dust accumulation is not related to the wind turbine entity,but to the flow field.By studying the wake field and power characteristics of wind turbines in different atmospheric boundary layers,it is found that in the atmospheric boundary layer,the large-scale vortex structure develops backward with the wind speed in a generally stable state,and the velocity presents a stratified distribution with uniform stratification.The air flow develops integrally upward in the atmospheric boundary layer.With the addition of dust,the flow field in the atmospheric boundary layer becomes more stable,and the axial wind speed increases and slows down from the bottom along the vertical direction.Smaller swirls form around the dust.The axial velocity of wind turbine wake has symmetry,which depends on atmospheric boundary layer characteristics.The wake of wind turbine basically recovered to 80% of the incoming flow at 6.5d.With the development of wake,the influence area gradually increased,and the recovery speed gradually accelerated.In the sandwind environment,the wake field of wind turbine is generally the same as that in the clean environment,with less speed loss,less velocity fluctuation,slower recovery speed,smaller wake expansion range and stronger symmetry.The wake of wind turbine in clean environment shows the characteristics of meandering and swinging in the atmospheric boundary layer.The swing and meandering amplitude of wind turbine near wake is small,but with the development of wake,the swing and winding amplitude is gradually severe.The swing and meandering of wind turbine wake are periodic,mainly swing around in the direction parallel to the ground,meandering development,small swing amplitude in the direction perpendicular to the ground;In the sand-wind environment,the wind turbine flow field has smaller meandering and swing amplitude.In the clean environment,the wake field of wind turbine is mainly tip vortex.Due to the influence of tower,the vortex distribution in the tail flow layer of wind turbine is scattered,and the absolute value of vorticity is relatively small.The existence of dust can break the tip vortex of wind turbine and make tip vortex dissipate in advance.The vortex generated by air flow bypassing sand dust increases the complexity of vortex distribution in the flow field.The wind turbine has lower power output and higher wind energy utilization coefficient in the same sand environment with the same energy input.The power output of the wind turbine has a very consistent frequency response to the flow field characteristics of the atmospheric boundary layer.The performance of wind turbine power output at high frequency in sand-wind environment is different from that in clean environment.