Experimental Testing of a Wind Tunnel Model for Use in a Vertical Axis Wind Turbine

Abstract

Experimental testing was performed on a circulation controlled airfoil with upper and lower trailing edge blowing slots, controlled by span wise pneumatic valves. The augmented blade was designed for application to a circulation controlled vertical axis wind turbine. The design is based upon a conventional NACA0018 shape, replacing the sharp trailing edge with a rounded Coanda surface and blowing slots. A scale model with a chord of 8 inches and span of 16.5 inches was created using an ABS plastic rapid prototyping machine. In the past, circulation control wind tunnel models have been constructed with a separate blowing slot and trailing edge using conventional machining methods. The slot must be tediously aligned along the span for a consistent height which ultimately affects the uniformity and performance of the circulation control jet in combination with the flow rate. The rapid prototyping machine eased fabrication as a modular trailing edge section was printed which includes the Coanda surface, blowing slot, and diffuser all in one piece. Pressure taps were integrated by the prototyping machine into both the printed skin and trailing edge module. This method left additional space inside the model for circulation control valving components and eliminated the need for machining pressure ports. This paper will outline the model building procedures, wind tunnel test rig, and experimental results. Aerodynamic forces were determined by both load cells and surface pressure measurements; the agreement between the two methods will be analyzed and addressed. Test conditions include various angles of attack (±20°) at Cμ = 0, 0.02, 0.06, and 0.10; the test Reynolds number was kept constant at 300K. The results indicate that the blade performed at ΔCl/Cμ near 30 for Cμ = 0.02.

Lift Enhancement of Circulation Control as Influenced by Ground Effect

“…To match the results from previous efforts of a similar NACA 0018 circulation control model, the blowing coefficient will equal 0.020. Panther et al 16 found that at an effective angle of attack of zero degrees and a blowing coefficient of 0.020, the coefficient of lift equaled approximately 0.52. Similarly, to produce these results, the free stream velocity was determined such that the Reynolds number was 300,000.…”

“…The next topic of discussion is the lift enhancement due to the airfoil in ground effect. According to Panther et al 16 , for the same airfoil, NACA 0018, the lift coefficient is 0 and 0.52 for C μ of 0 and 0.020, respectively. At the peak in Figure 13 for day two, the lift coefficient for C μ of 0 and 0.020 is 1.054 and 1.062, respectively.…”

Application of Circulation Controlled Blades for Vertical Axis Wind Turbines

“…This research considers the technical feasibility of utilizing active CC technology for improving VAWT aerodynamic efficiency, particularly at low wind speeds when performance is compromised relative to HAWTs. Although CC technology has previously been considered for wind turbine applications [19][20][21][22][23][24][25][26][27][28][29] few researchers consider the system requirements essential to determine if the technology is feasible for deployment on medium to large VAWTs.…”

Aerodynamic Response of a Pitching Airfoil with Pulsed Circulation Control for Vertical Axis Wind Turbine Applications

“…Recent work at CIRA and WVU revealed proof of concept that circulation control (CC) can be applied to VAWT blades to expand the operational envelope and performance (31) (32). Large aerodynamic improvements were proven for a conventional NACA0018, modified to include TE circulation control (herein described as "CCNACA0018"), with computational (33) (34), analytical (31) (35) (36) (37), and experimental methods (38). Analytical turbine models revealed the augmented blades increased both VAWT performance and operational envelope.…”

“…19 I want to extend a special and personal thanks to my closest friends, for understanding my two Figure 9. Measured Influence of  on CCNACA0018 Lift Augmentation (Re=300x10 3 , C  =Steady) (38) .... 12 Figure 38. Numerical and Experimental Loading on a Pitching NACA0012 : Re=3.45x10 6 , k=0.151 (110) .…”