| The wind turbine wake effect not only lead to a reduce on the power generation efficiency,but also an increase on the fatigue load.Therefore,it is important to study the wind turbine wake and load characteristics.The inflow turbulence intensity is one of the important parameters affecting the wake and load charac teristics of the horizontal axis wind turbine.Due to the influence of atmospheric environment and surface roughness,the size and distribution of turbulence intensity of different wind fields are different.Therefore,this paper takes the 33 kW horizontal axis wind turbine of Lanzhou University of Technology field experiment as the research object,the large eddy simulation coupled actuation line method is used to simulate the wake flow field under uniform inflow,different turbulence intensity inflow and neutral atmospheric boundary layer flow conditions,and the effects of turbulence intensity on the wake and load characteristics of horizontal axis wind turbine are studied.The main work is as follows:(1)By simulating the wind turbine wake flow field with the tip speed ratios of 5,6,7,8,and 9 respectively,the law of change with the tip speed ratios about the wind turbine wake velocity distribution,vorticity distribution,wake boundary,blade root waving load and low speed axis are analyzed,and the study about the wake and load characteristics of the wind turbine under uniform flow conditions are carried out.It is found that under uniform inflow conditions,the larger the tip velocity ratio,the faster the wake recovery and the greater the rate of wake velocity loss.The wake vorticity is concentrated at the tip and root of the blade.The intermittent vortex core gradually merges into a continuous vortex after drop fall off from the blade,and then dissipates into a vortex with less intensity.As the tip speed ratio increasing,The dissipation rate of the vortex become faster.The expansion of the wake can be divided into three stages: in the first stage,the growth rate of the wake radius is larger and gradually decreases in the 1D range after the wind turbine;in the second stage,the growth rate of the wake radius is small within a certain distance after 1D.The wake radius remains almost unchanged;in the third stage,the wake radius growth rate increases,and the wake reappears significantly.The expansion of the wake is related to the tip speed ratio,as the tip speed ratio increasing,the wake expansion position is advanced.Wind turbine blade root bending moment and wind rotor torque fluctuate periodically,and the fluctuation is mainly caused b y wake induction.The low-frequency part of the blade root bending moment and the wind rotor torque power spectrum are lower than the high-frequency part energy.(2)By simulating the turbulent inflow with turbulence intensity of 0.85%,5.2% and 10.3% respectively,the law of change with the tip speed ratios about the wake velocity distribution,vorticity distribution,turbulent kinetic energy,blade root waving moment and wind rotor torque are analyzed.The variation law of turbulence is studied,and the study about the wake and load characteristics of wind turbines under turbulent flow conditions are carried out.It is found that compared with the uniform inflow,the wake dissipation of turbulent field is accelerated,and the mixing rate with the surrounding flow is accelerated,so that the axial velocity reco very in the wake region is accelerated,and the greater the turbulence intensity is,the faster the velocity recovered.Compared to the uniform flow,the maximum loss rate of the axial velocity of the wake of the wind turbine is reduced,but the turbulence intensity has little effect on the maximum loss rate of the axial velocity of the wake;The growth rate of the wake radius gradually decreases from 1D after the wind turbine plane to the wind turbine,and is basically unchanged after 1D;Turbulence make the degree of expansion of the wake increases,and the greater the turbulence intensity is,the greater the degree of expansion;The increase of turbulence intensity leads to the mean value of blade root waving moment decreases,the amplitude of the fluctuation increases,and the high-frequency and low-frequency parts of the blade root waving moment increase,the low-frequency part increases the energy faster.Under the 11m/s wind speed,as the turbulence intensity increasing,the mean value of the torque of the wind tubine decreases,and the amplitude of the fluctuation increased,the energy of the high frequency and the low frequency part of the wind tubine torque is increased,and the energy of the low frequency part is increased faster.(3)By simulating the wind turbine flow field in the neutral atmosphere boundary layer,the influence of the turbulence of the neutral atmospheric boundary layer on the axial velocity distribution,vorticity distribution,turbulent kinetic energy and blade root waving moment of the wind turbine wake are analyzed.The wake and load characteristics of wind turbines in the neutral atmospheric boundary layer flow field are studied.It is found that the axial velocity of the wake of the wind turbine in the neutral atmospheric boundary layer recovers faster than that under the uniform flow condition,because the turbulence in the boundary layer of the neutral atmosphere accelerates the dissipation of the wake vortex;Compared with the uniform flow in the wind field of the neutral atmosphere boundary layer,the energy of the blade root wave moment power spectrum is higher,and the low frequency part of is higher than the energy of the high frequency part,indicating that the fluctuation of blade root wave moment in the neutral atmospheric boundary layer wind field more intense,the fluctuation of the blade root waving moment caused by the unevenness of the wind speed in the range of the wind turbine is stronger than the fluctuation caused by the turbulent pulsation speed. |
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