Vertical-axis wind turbines(VAWTs)have been widely used in urban environments,which contain dust and experience strong turbulence.However,airfoils for VAWTs in urban environments have received considerably less resear...Vertical-axis wind turbines(VAWTs)have been widely used in urban environments,which contain dust and experience strong turbulence.However,airfoils for VAWTs in urban environments have received considerably less research attention than those for horizontal-axis wind turbines(HAWTs).In this study,the sensitivity of a new VAWT airfoil developed at the Lanzhou University of Technology(LUT)to roughness was investigated via a wind tunnel experiment.The results show that the LUT airfoil is less sensitive to roughness at a roughness height of<0.35 mm.Moreover,the drag bucket of the LUT airfoil decreases with increasing roughness height.Furthermore,the loads on the LUT airfoil during dynamic stall were studied at different turbulence intensities using a numerical method at a tip-speed ratio of 2.Before the stall,the turbulence intensity did not considerably affect the normal or tangential force coefficients of the LUT airfoil.However,after the stall,the normal force coefficient varied obviously at low turbulence intensity.Moreover,as the turbulence intensity increased,the normal and tangential force coefficients decreased rapidly,particularly in the downwind region of the VAWT.展开更多
Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the ...Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the real magnitude and direction of the onflow velocity at the rotor blade can be determined, and subsequently, the aerodynamic force on the rotor can be determined. The commonly employed wake aerodynamic models are of the cylindrical form instead of the actual expanding one. This is because the influence of the radial component of the induced velocity on the wake configuration is neglected. Therefore, this model should be called a "linear model". Using this model means that the induced velocities at the rotor blades and aerodynamic loads on them would be inexact. An approximately accurate approach is proposed in this paper to determine the so-called "nonlinear" wake aerodynamic configuration by means of the potential theory, where the influence of all three coordinate components of the induced velocity on wake aerodynamic configuration is taken into account to obtain a kind of expanding wake that approximately looks like an actual one. First, the rotor aerodynamic model composed of axial (central), bound, and trailing vortexes is established with the help of the finite aspect wing theory. Then, the Biot-Savart formula for the potential flow theory is used to derive a set of integral equations to evaluate the three components of the induced velocity at any point within the wake. The numerical solution to the integral equations is found, and the loci of all elementary trailing vortex filaments behind the rotor are determined thereafter. Finally, to formulate an actual wind turbine rotor, using the nonlinear wake model, the induced velocity everywhere in the wake, especially that at the rotor blade, is obtained in the case of various tip speed ratios and compared with the wake boundary in a neutral atmospheric boundary layer. Hereby, some useful and referential conclusions are offered for the aerodynamic computation and design of the rotor of the horizontal-axis wind turbine.展开更多
基金This work was supported by the Natural Science Foundation of GANSU(grant 1508RJYA098)National Natural Science Foundation of China(grants 51766009,51761135012,11872248)+1 种基金National Basic Research Program of China(grant 2014CB046201)The authors also thank the people who provided many good suggestions for this paper,and Northwestern Polytechnical University for providing the experimental instruments and wind tunnel.
文摘Vertical-axis wind turbines(VAWTs)have been widely used in urban environments,which contain dust and experience strong turbulence.However,airfoils for VAWTs in urban environments have received considerably less research attention than those for horizontal-axis wind turbines(HAWTs).In this study,the sensitivity of a new VAWT airfoil developed at the Lanzhou University of Technology(LUT)to roughness was investigated via a wind tunnel experiment.The results show that the LUT airfoil is less sensitive to roughness at a roughness height of<0.35 mm.Moreover,the drag bucket of the LUT airfoil decreases with increasing roughness height.Furthermore,the loads on the LUT airfoil during dynamic stall were studied at different turbulence intensities using a numerical method at a tip-speed ratio of 2.Before the stall,the turbulence intensity did not considerably affect the normal or tangential force coefficients of the LUT airfoil.However,after the stall,the normal force coefficient varied obviously at low turbulence intensity.Moreover,as the turbulence intensity increased,the normal and tangential force coefficients decreased rapidly,particularly in the downwind region of the VAWT.
基金Project supported by the National Basic Research Program of China(No.2014CB046201)the National Natural Science Foundation of China(Nos.51766009,51566011,and 51479114)
文摘Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the real magnitude and direction of the onflow velocity at the rotor blade can be determined, and subsequently, the aerodynamic force on the rotor can be determined. The commonly employed wake aerodynamic models are of the cylindrical form instead of the actual expanding one. This is because the influence of the radial component of the induced velocity on the wake configuration is neglected. Therefore, this model should be called a "linear model". Using this model means that the induced velocities at the rotor blades and aerodynamic loads on them would be inexact. An approximately accurate approach is proposed in this paper to determine the so-called "nonlinear" wake aerodynamic configuration by means of the potential theory, where the influence of all three coordinate components of the induced velocity on wake aerodynamic configuration is taken into account to obtain a kind of expanding wake that approximately looks like an actual one. First, the rotor aerodynamic model composed of axial (central), bound, and trailing vortexes is established with the help of the finite aspect wing theory. Then, the Biot-Savart formula for the potential flow theory is used to derive a set of integral equations to evaluate the three components of the induced velocity at any point within the wake. The numerical solution to the integral equations is found, and the loci of all elementary trailing vortex filaments behind the rotor are determined thereafter. Finally, to formulate an actual wind turbine rotor, using the nonlinear wake model, the induced velocity everywhere in the wake, especially that at the rotor blade, is obtained in the case of various tip speed ratios and compared with the wake boundary in a neutral atmospheric boundary layer. Hereby, some useful and referential conclusions are offered for the aerodynamic computation and design of the rotor of the horizontal-axis wind turbine.