Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigate...Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigated by using of wind turbine blade design software, PROPID. Firstly, a wind turbine blade of 2MW class was designed with DU-serics airfoils in the inner part and with aNACA series airfoil as a main airfoil in the outer part. Lift distribution was set to have near L/D maximum at each span station. Then, lift and drag curves were modified to observe effect of L/D variation. Drag and lift change with constant L/D on blade power coefficient was also studied for sensitivity investigation. Each case was optimized with Newtonian iteration incorporated in PROPID. High design lift coefficient results in less chord length and twist angle to maintain same aerodynamic load level. And, power coefficient wasn＇t improved much with high L/D. During the process, optimal inputs such as lift distribution, design lift and induction factors were suggested. As results, it was found that L/D maximization was important to obtain high efficiency. For the L/D maximization, lift maximization was important to minimize structural weight, but decreasing drag didn＇t affect the blade shape.展开更多
As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of t...As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of the prediction and passive control of trailing-edge noise source with the non-porous and porous treatment,respectively.The flow fields around the bionic airfoil indicate that the leading-edge separation causes both the noise contributors,i.e.,the turbulent boundary layer and the vortex shedding.In addition,the effect of the porous trailing edge is substantiated in the distribution of the static pressure.The relevant noise also suggests a pronounced noise reduction potential in excess of 10 dB,but it has dependence on the flow resistivities.The two trailing-edge noise reduction mechanisms are characterized:(1)the suppression of the tonal vortex shedding noise;(2)the reduction of broadband turbulent boundary layer scattering noise.The findings may be used as reference in the design of silent aircraft.展开更多
Predicting wind turbine S825 airfoil＇s aerodynamic performance is crucial to improving its energy efficiency and reducing its environmental impact. In this paper, a numerical simulation on the wind turbine S825 airfo...Predicting wind turbine S825 airfoil＇s aerodynamic performance is crucial to improving its energy efficiency and reducing its environmental impact. In this paper, a numerical simulation on the wind turbine S825 airfoil is con- ducted with k-to turbulence model at different attack angles. By comparing with experimental data, a new method of modifying k-to model is proposed. A modifying function is proposed to limit the production term in ω equation based on fluid rotation and deformation. This method improves turbulent viscosity and decreases separating re- gion when the airfoil works at large separating conditions. The predictive accuracy could be improved by using the modified k-to turbulence model.展开更多
文摘Optimization of airfoil characteristics such as lift and drag is essential for high efficiency wind turbine blade design. In this research, effects of airfoil lift and drag on blade power coefficients were investigated by using of wind turbine blade design software, PROPID. Firstly, a wind turbine blade of 2MW class was designed with DU-serics airfoils in the inner part and with aNACA series airfoil as a main airfoil in the outer part. Lift distribution was set to have near L/D maximum at each span station. Then, lift and drag curves were modified to observe effect of L/D variation. Drag and lift change with constant L/D on blade power coefficient was also studied for sensitivity investigation. Each case was optimized with Newtonian iteration incorporated in PROPID. High design lift coefficient results in less chord length and twist angle to maintain same aerodynamic load level. And, power coefficient wasn＇t improved much with high L/D. During the process, optimal inputs such as lift distribution, design lift and induction factors were suggested. As results, it was found that L/D maximization was important to obtain high efficiency. For the L/D maximization, lift maximization was important to minimize structural weight, but decreasing drag didn＇t affect the blade shape.
基金supported by the National Natural Science Fundation of China(Major Project of International Cooperation)(Grant No.50920105504)
文摘As a promising means,the passive porosity technology is used for the trailing-edge noise reduction of a bionic airfoil.The detailed two-dimensional Large Eddy Simulation is achieved to gain a better understanding of the prediction and passive control of trailing-edge noise source with the non-porous and porous treatment,respectively.The flow fields around the bionic airfoil indicate that the leading-edge separation causes both the noise contributors,i.e.,the turbulent boundary layer and the vortex shedding.In addition,the effect of the porous trailing edge is substantiated in the distribution of the static pressure.The relevant noise also suggests a pronounced noise reduction potential in excess of 10 dB,but it has dependence on the flow resistivities.The two trailing-edge noise reduction mechanisms are characterized:(1)the suppression of the tonal vortex shedding noise;(2)the reduction of broadband turbulent boundary layer scattering noise.The findings may be used as reference in the design of silent aircraft.
基金supported by the National Natural Science Foundation of China(No.51420105008,No.51376001)the National Basic Research Program of China(2012CB720205,2014CB046405)
文摘Predicting wind turbine S825 airfoil＇s aerodynamic performance is crucial to improving its energy efficiency and reducing its environmental impact. In this paper, a numerical simulation on the wind turbine S825 airfoil is con- ducted with k-to turbulence model at different attack angles. By comparing with experimental data, a new method of modifying k-to model is proposed. A modifying function is proposed to limit the production term in ω equation based on fluid rotation and deformation. This method improves turbulent viscosity and decreases separating re- gion when the airfoil works at large separating conditions. The predictive accuracy could be improved by using the modified k-to turbulence model.
