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

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. Three J-shaped pressure-side truncation ratios (1/3, 1/2, and 2/3) and two Kammtail Virtual Foil (KVF) truncation ratios (1/8 and 1/4) were studied. The baseline design was experimentally investigated. Output power was measured using a digital rotary torque sensor at 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 simulations to capture the performances of the proposed cases and compare them with the baseline. The simulation investigation was carried out for lab-scale and scaled cases. The three-dimensional study found that the J-shaped blades enhanced the performance of the HAWTs for both lab-scale and scaled cases. 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 cases, 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 cases, 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 cases, respectively. Furthermore, it was found that the KVF blades diminished the performance for both lab-scale and scaled cases.