Aerofoil optimization for improving the power performance of a vertical axis wind turbine using multiple streamtube model and genetic algorithm.

Changping Liang,Huaxing Li

doi:10.1098/rsos.180540

Changping Liang, Huaxing Li

Open Access

https://doi.org/10.1098/rsos.180540

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Abstract

This paper reports on the optimization of the NACA0015 aerofoil for improving the power performance of a vertical axis wind turbine (VAWT). The target range of the chord Re is 3 × 105–106, the tip speed ratio (TSR) is 2–6 and the solidity is 0.2–0.6. This aerofoil is widely applied in small-scale VAWTs. In the optimization process, in which the class and shape function transformation parametrization method was used to perturb the aerofoil geometry, the thickness and camber of the aerofoil were selected as the constraints and the value of the maximum tangential force coefficient was chosen as the objective function. The aerodynamic performance of the aerofoil was calculated by combining the XFOIL program and Viterna–Corrigan post-stall model, while the aerofoil's performance was validated with computational fluid dynamic simulations. The results illustrated that, compared to an unoptimized NACA0015 aerofoil, the optimized aerofoil's lift to drag ratio was improved over a wide range of attack angles and the stall performance was gentler. The maximum lift coefficient, the maximum lift to drag ratio and the maximum tangential force coefficient were increased by 7.5%, 9% and 8.87%, respectively. Finally, this paper predicted the rotor efficiency with both the unoptimized and optimized NACA0015 aerofoils for different TSRs and different solidities using the multiple streamtube model. The results showed that the rotor with the optimized aerofoil has a higher efficiency.

Highlights

Energy is arguably the foundation of economic and social development and is closely related to human life and living environments
Because the tangential force is responsible for the power produced by a vertical axis wind turbine (VAWT), we maximized the tangential force coefficient, and this study proposes an optimization of the NACA0015 aerofoil based on the class and shape function transformation (CST) parametrization and the non-dominated sorting genetic algorithm (NSGA-II)
Compared to the previous methods, the optimization method proposed in this paper takes the fact that the angle of attack of the blades in a VAWT changes continuously into account, and proposes maximizing the tangential force coefficient at seven angles of attack instead of just maximizing the lift or ratio of the lift to drag coefficient at a single angle of attack, and this optimization method is more suitable for the optimization of the NACA0015 aerofoil which is widely applied in small-scale VAWTs

Summary

Introduction

Energy is arguably the foundation of economic and social development and is closely related to human life and living environments. Compared to the previous methods, the optimization method proposed in this paper takes the fact that the angle of attack of the blades in a VAWT changes continuously into account, and proposes maximizing the tangential force coefficient at seven angles of attack instead of just maximizing the lift or ratio of the lift to drag coefficient at a single angle of attack, and this optimization method is more suitable for the optimization of the NACA0015 aerofoil which is widely applied in small-scale VAWTs. Compared to Zhang et al.’s [13] study of the optimization of a horizontal axis wind turbine (HAWT) aerofoil and Qu et al.’s [14] study of the optimal design of a VAWT aerofoil based on the complex optimum method, the aerofoil optimization method proposed in this paper gave better results. Cds drag coefficient of stall α angle of attack αs stall angle of attack μ aspect ratio t aerofoil thickness c aerofoil camber

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Results

Conclusion