The thickness ratios studied were 0.18, 0.15, and 0.12, and 0.09. Tests were conducted at Reynolds number ranging from 0.25 x 106 to 1.0 x 106.
#Naca 4 digit airfoil generator matlab series#
This report documents results of the wind tunnel investigation of constant chord blades having four more » aspect ratios, with NACA 44XX series airfoil sections, at angles of attack ranging from -10/sup 0/ to 110/sup 0/. The purpose of this wind tunnel study is to characterize the performance characteristics of a blade in stall as a function of its aspect ratio, airfoil thickness, and Reynolds number. Peak power predictions upon which wind turbine components are sized depend on a good understanding of a blade's post-stall characteristics. Unlike aircraft, a wind turbine's angle of attach range extends deep into stall where the three-dimensional performance characteristics of airfoils are not generally known. Wind turbine blades operate over a wide angle of attach range. It was concluded that rectilinear flow aerodynamic data are not applicable to Darrieus turbine blades, even for small chord-to-radius ratios. Boundary-layer centrifugal effects were manifested by discontinuous lift curves and large differences in the angle of zero lift between th NACA 0015 and elliptical airfoils. These features more » verified the predicted virtual camber and incidence phenomena. Although the airfoil sections were symmetrical, moment coefficients were not zero and the lift and drag curves were asymmetrical about zero lift coefficient and angle of attack. Blade aerodynamic coefficients were corrected to section coefficients for comparison to published rectilinear flow data. The first blade used an NACA 0015 airfoil section the second used a 15% elliptical cross section with a modified circular arc trailing edge. Lift, drag, and moment coefficients were measured for two blades whose angle of attack and chord-to-radius ratio were varied. « lessĪn indoor facility for the aerodynamic testing of Darrieus turbine blades was developed. An attempt was made to account for the flow curvature effects associated with Darrieus turbines by transforming the NACA 63/sub 2/-015 airfoil to an appropriate shape. Sample calculations for an NACA 63/sub 2/-015 airfoil showed an annual energy output increase of 17 to 27% depending upon rotor solidity, compared to an NACA 0015 airfoil. Furthermore, the power coefficient-tip speed ratio curves were broader and flatter for the 6-series airfoils. Performance calculations indicated that the NACA 6-series airfoils yield peak power coefficients at least as great as the NACA four-digit airfoils which have historically been chosen more » for Darrieus turbines. Ten different airfoils, having thickness to chord ratios of twelve, fifteen and eighteen percent, were investigated. Analysis was limited to machines using two blades of infinite aspect ratio, having rotor solidites from seven to twenty-one percent, and operating at maximum Reynolds numbers of approximately three million. The purpose of this study was to determine what aerodynamic performance improvement, if any, could be achieved by judiciously choosing the airfoil sections for Darrieus wind turbine blades.