Analysis of angular velocities, surrounding air pressure and velocities of various designed micro vertical axis Savonius wind turbines by the computational fluid dynamics (CFD) method

Abstract

Copyright © 2019 ASME. The objective of this study is to analyze angular velocities, surrounding air pressure and velocities of various micro vertical axis Savonius wind turbine prototypes by the Computational Fluid Dynamics (CFD) method. The angular velocities of turbines are the basic parameters for determining the major parameters of the wind turbines, such as efficiency, torque, power and electricity etc. Eight models of the micro vertical axis Savonius wind turbine made of acrylic were designed by varying three parameters including the turbine distance between the pivot point and the tip, the distance between the apex curvature and the center plane curvature and the cross section types (circular, square, triangular and trapezoid). The eight models were divided into three groups including two models (B1, B2) with two different cross section types (triangle and rectangular) in the first group, three models (C1, C2, C3) with three different distances from the curvature tip to the centerline of 110, 85 and 40 millimeters in the second group and three models (D1, D2, D3) with different distances between the pivot point and the tip in the third group. Then, the angular velocities, the surrounding air pressure and velocities of the micro vertical axis Savonius wind turbine at the five wind speeds at 5.59, 7.67, 9.76, 10.45 and 11.84 m/s were measured and evaluated by the ANSYS program. The simulation by the CFD method of the angular velocities of the designed wind turbines was compared with the experimental results. Some discrepancies due to the absence of friction in the CFD results were observed. However, discrepancies between the simulation and the experimental results were decreased when the wind speed was increased due to the increase of torque and force in the experimental results which has overcome the turbine core friction. It has indicated that at the highest wind speed (11.84 m/s), the designed micro vertical axis Savonius circular cross section wind turbine with the curvature of the distance from the apex curvature to the center plane at 110 millimeters gave the highest turbine angular velocity of 441 rpm. At this highest turbine velocity by the CFD simulation, the high surrounding air pressure was not the smallest and the low turbine surrounding air pressure area was not the largest. This might be due to the effect of the suitable apex curvature distance to the center plane causing the efficient air flow to overcome the effect of the surrounding air pressure. The wind turbine of the second group gave the highest angular velocities followed by the first and the third group. These designed micro vertical axis Savonius wind turbines can be used as a preliminary model for the design and construction of the micro wind turbine to generate electricity at low wind speed region, such as Thailand.