EFFECT OF AEROFOIL THICKNESS ON THE WIND TURBINE BLADE: CASE STUDY OF FFA-W3-270 AND FFA-W3-240 AEROFOIL

Abstract

Due to the climate change nowadays, there are a lot of alternative ways to convert renewable energy to generate electricity and the wind energy is one of them. Reynold's numbers of 0.8 × 10⁶ and 1.0 × 10⁶ are compared in this study to see their effects on the FFA-W3-270 and FFA-W3-240 aerofoil models. The dimension of the FFA-W3-240 type is 120 mm thick, with a chord of 500 mm and a span of 800 mm. In contrast, the FFA-W3-270 type has 128 mm maximum thickness, 500 mm chord and a span of 750 mm. Investigation of the lift force, drag force, pitching moment and pressure distributions on these two aerofoil models is done in a wind tunnel test using UTM LST Wind Tunnel, which has dimensions of 1.5 m x 2 m x 5.8 m. The wind tunnel experiments are carried out at 25 m/s and 31.2 m/s wind stream velocity and angle of attack ranging from -4 ° to 18 ° with an increment of 2°. From the experimental results, it is observed that the pressure coefficient on the upper surface of the FFA-W3-240 has a significant change in comparison to that for the FFA-W3-270. When the adverse pressure gradient increases, it causes earlier separation for thinner aerofoil. In contrast, it causes separation delay for the thick aerofoil. From this, it shows that FFA-W3-270 has better aerodynamic performance. For FFA-W3-240, at Reynold’s number 1.0 × 10⁶, stall occurs at 14° with maximum lift coefficient of 1.26. However, for FFA-W3-270, stall does not occur up until 18°. Besides, for FFA-W3-240, increasing the Reynold’s number will increase the drag coefficient at stall point by over 5.48%. For both models, the pitching moment coefficient remains relatively constant over the considered range of angles of attack due the moment being calculated at the aerodynamic center of the aerofoil, which is estimated to be at the quarter-chord location from the leading edge.