The effects of the location of the leading-edge tubercles on the performance of horizontal axis wind turbine

Abstract

Horizontal axis wind turbines (HAWTs) stand out in terms of providing energy for sustainable ecosystems. Therefore, increasing the power coefficient (CP) of wind turbines is essential for the efficient use of energy. This study experimentally examined the influence of the location of the leading edge (LE) tubercles on the performance of a three-bladed small-scale HAWT rotor. For this purpose, experimental studies were conducted to determine the performance of a small-scale HAWT under static and dynamic conditions, and information about the 3D flow field was obtained using the surface oil flow visualization technique. The NACA 4412 airfoil was selected, and the optimum blade geometry was designed using Schmitz equations based on the blade element momentum (BEM) theorem. Experiments were conducted in a blowing-type wind tunnel with an open test section for three different rpm of the rotor (300, 400, and 500) to determine the CP of the rotor.Three different configurations with LE tubercles at 100 %, 50 %, and 25 % rotor radius toward the blade tip, designated B1, B2, and B3, have been compared with the baseline blade. Measurements indicate that the LE tubercles, located over 50 % of the blade span, provide a notable enhancement in the CP.B2 exhibited the best performance at all the examined rotor speeds, followed by B3. The highest CP was 0.32 for the B2 at 500 rpm, a 39.1 % improvement over the baseline blade. Moreover, the maximum improvement in the CP was achieved by 63.2 % at 400 rpm on the B2 blade compared with the baseline blade. The CP was accurately predicted via regression analysis based on the location of the LE tubercles, and the model demonstrated high accuracy and reliability.