Preliminary Theoretical Study of Double Blade 2-D Aerodynamics for Applications to Vertical Axis Wind Turbines

摘要

As part of a preliminary system feasibility analysis of a vertical axis wind turbine system LDB-VAWT, theoretical calculations of 2D aerodynamic characteristics of double blade configurations have been performed. The theoretical method used is a method developed at Lockheed, Georgia for NASA, here referred to as the NASA- Lockheed method, which computes the subsonic, viscous, attached flow about multielement airfoils. The objective of this preliminary study is to get an idea of how much energy is lost when using double blades instead of single. The resulting tangential force for the double or single blade configuration is used as a criterion for this , and shall be as great as possible (mean value). The following parameters are varied to see how the tangential force, expressed as Csub(t), is affected; the radial spacing, toe in toe out angle and tangential displacement (stagger). The results obtained indicate that the greatest Csub(t)-values are achieved for maximum allowable radial spacing, which is determined by structural considerations, and is assumed to be in the order of 1.5 c. At this rather large distances, stagger as well as toe in - toe out angle may only give slight improvements as long as the flow separation effects (stall region) are not considered. However, a large part of the energy is captured at relatively high wind speeds when the flow on the blades is partly. (ERA citation 07:062948)