23_1400_tetsuyakogaki_01 - PERFORMANCE IMPROVEMENT OF...

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PERFORMANCE IMPROVEMENT OF AIRFOILS FOR WIND TURBINES BY THE MODIFIED VORTEX GENERATOR Tetsuya KOGAKI #1 , Hikaru MATSUMIYA #1 , Kaori KIEDA #2 , Naofumi YOSHIMIZU #3 and Yuusuke YAMAMOTO #3 #1 National Institute of Advanced Industrial Science and Technology (AIST) Namiki 1-2-1, Tsukuba-shi, Ibaraki, 305-8564 Japan Phone: +81-(0)29-861-7251, FAX: +81-(0)29-861-7275 e-mail: kogaki.t@aist.go.jp, h-matsumiya@aist.go.jp #2 AES Co. Ltd., Takezono 1-6-1, Tsukuba-shi, Ibaraki, 305-0032 Japan Phone: +81-(0)29-855-2001, FAX: +81-(0)29-855-9815, e-mail: k.kieda@aist.go.jp #3 Ibaraki University, Narusawa 4-12-1, Hitachi-shi, Ibaraki, 316-8511 Japan Phone: +81-(0)294-38-5046, FAX: +81-(0)294-38-5047 e-mail: nyoshimi@mech.ibaraki.ac.jp, yamamoto-pukapuka@aist.go.jp In this paper, the new modified vortex generator (VG) was developed for wind turbine airfoils. The modified vortex generator has a section of airfoil to decrease the drag of the vortex generator itself while keeping the strength of streamwise vortices. The wind tunnel experiments were conducted to examine the effectiveness of the modified vortex generator. The effect of Reynolds number, height and interval of vortex generator were examined by the wind tunnel experiments. The preliminary CFD simulations were also conducted to confirm the turbulent enhancement effect of the modified vortex generator. The previous vortex generator of which section is flat plate enhances lift, however, the drag also increases simultaneously. Therefore, lift-to-drag ratio was not necessarily modified by the flat plate vortex generator. On the other hand, lift-to-drag ratio considerably increased by means of the modified vortex generator, especially in low Reynolds number of Re =100,000 - 400,000. Therefore, it was verified that the modified vortex generator is suitable especially for airfoil of small wind turbines. Keywords : vortex generator, airfoil, small wind turbine, CFD, wind tunnel experiments 1 INTRODUCTION Although the performance of wind turbines is dominated by various factors, the performance of airfoils is the most influential. The low Reynolds number airfoils designed for small aircraft were widely used in the early stage development of modern horizontal axis wind turbines. Airfoils designed for aircraft are not always suitable, however, because the range of operational Reynolds number is wide and because the inflow wind is fluctuated. Therefore, national institutes and Universities started to develop airfoils designed exclusively for wind turbines in 1980s, and we have also developed MEL-airfoil families for wind turbines [1, 2]. Because the development of airfoil series tailored for a specific wind turbine is not cost- effective, it is conjectured that the flow control techniques such as the vortex generators (VGs) become effective. We attached simple vortex generators with a flat plate cross section on the airfoil surface, and their effectiveness was verified by the wind tunnel experiment [3]. As a result, the lift coefficient was increased and airfoil performance is stabilized.
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23_1400_tetsuyakogaki_01 - PERFORMANCE IMPROVEMENT OF...

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