Ke Yang

Large thickness airfoils with high lift in the operating range of angle of attack

This paper presents the design, prediction and evaluation of a family of large thickness airfoils with blunt trailing edges. The family includes four airfoils, whose relative thickness ranges from 45% to 60% and relative thickness of trailing edge ranges from 7% to 16%. These airfoils are designed by the RFOIL solver at different design Reynolds numbers of 4.0u2009×u2009106, 3.5u2009×u2009106, 3.0u2009×u2009106, and 2.5u2009×u2009106 with increasing thickness. The design Reynolds numbers are calculated by the operating characteristics of a 5u2009MW wind turbine. The design objectives focus on the aerodynamic performance in operating ranges of angle of attack at blade root, differing from those of the aviation airfoils and traditional wind turbine airfoils. And the main design constraint is the stability of the lift coefficients in range of large angles of attack with the variation of Reynolds number. The predictions by RFOIL show that, in the range of angle of attack (15°–30°), the values of lift coefficient of the four new airfoils are lar...

A method to evaluate the overall performance of the CAS-W1 airfoils for wind turbines

This paper presents an evaluation method with a performance parameter system of wind turbine airfoils, and then estimates the overall performance of the CAS-W1 airfoils compared with some DU airfoils with available experimental data. The CAS-W1 airfoil family is developed by Institute of Engineering Thermophysics with the XFOIL code. The family includes 11 airfoils, whose relative thickness ranges from 15% to 60%. Four thin airfoils and three thick airfoils have been measured in NF-3 wind tunnel in Northwestern Polytechnical University. Different from previous airfoil performance analysis, the evaluation herein focuses on design point, off-design performance, stalling characteristic, and performance stability. Results show that, compared with DU airfoils, thin CAS-W1 airfoils have favorable design point, good off-design performance, and could keep stable with the variation of surface roughness and Reynolds number; Three inboard airfoils have soft stall performance but ordinary design point and off-design ...

Experimental study of Reynolds number effects on performance of thick CAS wind turbine airfoils

In this study, the effects of Reynolds number on four thick CAS airfoils of two generations were studied at two different wind tunnels. The results show that in natural transition, increasing Re leads to a reduction of the maximum lift coefficient and stall angle of attack. Furthermore, the results show that increasing Re causes the separation point to move to the leading edge in thick CAS airfoils. This could be reflected by the influence of Re on the separation of the laminar boundary layer. Specifically, it is found that for thick airfoils, the large leading edge radius helps to maintain a laminar boundary layer near the frontal upper surface even at very high angles of attack, whereas the high slope of the rear part of suction surface triggers early separation at small angles of attack. Both of these contribute to a “negative” effect of Reynolds number. The study indicates that the positive effect of Reynolds number on thin airfoils is not suitable for thick airfoils, which is at least highly geometry...