Experimental and Simulation Investigation of J-Shaped and Kammtail Virtual Airfoils in Small-Scale Horizontal Axis Wind Turbines

Abstract

Abstract In this work, the performance of new wind blade designs for small-scale horizontal axis wind turbines (HAWTs) was studied and compared with the performance of a baseline design. The studied designs were J-shaped and Kammtail Virtual Foil (KVF) profiles. Three J-shaped opening ratios (1/3, 1/2, and 2/3) and two KVF truncation ratios (1/8 and 1/4) were studied. All proposed designs were first investigated in a two-dimensional simulation study to get the lift-to-drag ratio by applying different wind speeds and angles of attack. The baseline design was experimentally investigated. Output power was measured using a digital rotary torque sensor using three different wind speeds. Tip speed ratio (TSR) was calculated after measuring each wind speed’s free rotating revolutions per minute (RPM). Three wind speeds and experimental TSRs were used in three-dimensional simulation to capture the performances of the proposed designs and compare them with the baseline. The simulation investigation was carried out for lab-scale and scaled designs. The two-dimensional study found that the J-shaped and KVF airfoils yielded more lift-to-drag ratios than the baseline for some angles of attack and wind speeds. The three-dimensional study found that the J-shaped blades enhanced the performance of the HAWTs for both lab-scale and scaled designs. J-shaped blades with a 1/3 opening ratio yielded an average power coefficient enhancement of around 1.56% and 4.16% for lab-scale and scaled designs, respectively. J-shaped blades with a 1/2 opening ratio yielded an average power coefficient enhancement of around 1.15% and 4.23% for lab-scale and scaled designs, respectively. On the other hand, J-shaped blades with a 2/3 opening ratio yielded an average power coefficient enhancement of around −0.12% and 2.54% for lab-scale and scaled designs, respectively. Furthermore, it was found that the KVF blades diminished the performance for both lab-scale and scaled designs.