Session: 41-03 Small-scale Wind Turbines

Paper Number: 128897

128897 - Investigating the Performance of a Small Horizontal Axis Wind Turbines (HAWT) Using Toroidal Blades 

Optimizing the aerodynamic design of wind turbine blades for small-scale horizontal-axis wind turbines (HAWT) is crucial to the annual energy augmentation, performance, and efficiency of the turbine. The principal objective of the present work is to study the newly designed multi-bladed HAWT aerodynamic behavior and characteristics by introducing the toroidal blade using computational fluid dynamics (CFD). The present work also aims to properly understand the aerodynamic behavior of the two- and three-bladed toroidal rotor, to improve HAWT performance through increasing the power coefficient (Cp), to search for the optimum looping ratio (C), and to improve the performance of the HAWT toroidal blade. The toroidal blade has been revived by the MIT group as a propeller. However, no performance results have been reported for toroidal turbines. In the present work, a comparison between the toroidal and conventional turbine blades is conducted by monitoring the power coefficient (Cp). The Blade Element Momentum (BEM) theory is used to design and carry out the geometry of the conventional blade. A NACA 4412 airfoil is used as the baseline for the blade optimization process, which provides higher aerodynamic efficiency by increasing the lift-to-drag ratio and the lift coefficient. The geometry characteristics, such as chord length and twist, were calculated along the blade. The main dimensions for the toroidal and basic blades are considered. The toroidal blade turbine has a 42 cm rotor diameter and 5 cm hub diameter, while the basic blade turbine has a 47 cm rotor diameter and a 5 cm hub diameter. Then, the 3D geometric domain was created and meshed appropriately for the rotor. The analysis is performed on a model representing one-half of the rotor at a constant wind speed and various tip speed ratios (TSR), and the Moving Reference Frame (MRF) method is used to define the blade rotational motion. The k-ε turbulence model is applied with the required boundary conditions. A parametric study for the toroidal blade is carried out on shape ratio (C), which is the ratio of the minor to major diagonal of the ellipse forming the toroidal blade. The toroidal rotor consists of two looped blades, so that the blade tip curves back into the other blade. This looped structure minimizes the drag effects and vortices created at the blade tip and strengthens the rotor's overall stiffness. These features cause the rotor’s acoustic signature and, most importantly, the tip losses to reduce, which affect the Cp. The results demonstrate the computed power coefficient (Cp) of the two bladed toroidal blade with a looping ratio (C) of 0.75 and the three bladed basic blade turbines at different tip speed ratios (λ). The results show a close performance of the toroidal blade rotor with that of the basic blade rotor. However, the basic blade Cp is higher at a high tip speed ratio. The toroidal blade rotor has a high Cp at a lower tip speed ratio. It is planned to investigate three blade toroidal rotors of different looping ratios to find out which geometry can be used to augment wind turbine performance. The results illustrate that the toroidal blades can be used in small HAWT to improve performance and reduce noise level, and the power coefficient is increased compared to the conventional blades at a lower tip speed ratio.

Presenting Author: Ahmed El Baz The British University in Egypt

Presenting Author Biography: Dr. Elbaz graduated in 1984 from the Energy and Automotive department at Ain Shams University. He joined the same department as a demonstrator and finished his MSC in Mechanical engineering from the same department in 1987. He then joined the University of Manchester Institute of Science and Technology (UMIST) as PhD student. He worked with one of the key scientists in turbulent flow modelling, Brian Launder from 1987 to 1992. Having obtained his PhD he joined Ain Shams University in 1992 as a Lecturer. He stayed at Ain Shams University till 2013 when he joined the British University in Egypt as an Associate Professor and was promoted as full time Professor in 2015. He is working in the field of thermofluidic engineering. He has more than 40 articles and supervised more than 40 MSC and PhD students. Recently, his interest is focused on research work in the wind energy conversion systems.

Authors:

Ahmed Ezz The British University in Egypt
Ahmed El Baz The British University in Egypt