Airfoil Selection for a Straight Bladed Circulation Controlled Vertical Axis Wind Turbine

Abstract

A vertical axis wind turbine (VAWT) prototype is being developed at West Virginia University that utilizes circulation control to enhance its performance. An airfoil was chosen for this turbine based on its performance potential, and ability to incorporate circulation control. The selection process for the airfoil involved the consideration of camber, blade thickness, and trailing edge radius and the corresponding impact on the lift and drag coefficients. The airfoil showing the highest lift/drag ratio augmentation, compared to the corresponding unmodified airfoil was determined to be the most likely shape for use on the circulation control augmented vertical axis wind turbine. The airfoils selected for this initial investigation were the NACA0018, NACA2418, 18% thick elliptical, NACA0021, and the SNLA2150. The airfoils were compared using the computational fluid dynamics program FLUENT v.6.3.26 with a blowing coefficient of 1% [1]. The size of the trailing edge radius and the slot heights were varied based on past experimental data [2]. The three trailing edge radii and two blowing slot heights were investigated. The thickness of the airfoil impacts the circulation control performance [3], thus it was studied by scaling the NACA0018 to a 21% thickness and compared to an SNLA2150 airfoil. The airfoils’ lift and drag coefficients were compared to determine the most improved lift-drag ratio (L/D). When comparing the increases of the L/D due to circulation control, the NACA0018 and 2418 airfoils were found to outperform the elliptical airfoil; the NACA0018 performed slightly better than the 2418 when comparing the same ratio L/D. The results showed that the 21% thick airfoils produced a decreased L/D profile compared to the NACA0018 airfoils. Therefore, the NACA0018 was found to be the optimal airfoil based from this initial investigation due to an increased L/D compared to the other airfoils tested.

2D CFD Simulation Study on the Performance of Various NACA Airfoils

“…Nonetheless, the drag coefficient values are found to be consistent. As for investigation on NACA 0018 airfoil, it was further proven that the lift coefficient is dependent on the angle of attack for the NACA 0018 airfoil at three different trailing radius ratios [15]. It was found through this investigation that at a high angle of attack between 12 and 15 degrees with a trailing edge radius of 0.04, this setup is beneficial when considering the lift.…”

Application of Circulation Controlled Blades for Vertical Axis Wind Turbines

“…In 2006 the aerodynamic performance of a circulation controlled horizontal axis wind turbine (HAWT) rotor was investigated numerically and showed an augmentation in the net power production at low wind speeds (7 m/s) with moderate blowing momentum coefficients (C μ ≤ 0.075) [19]. WVU also performed preliminary numerical studies on a CC H-type VAWT in 2009, predicting that overall power output performance could be increased by 24% at a blowing coefficient of C μ = 0.1 [20].…”

“…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.…”