A Study On The Aerodynamic Characteristics And Airfoil Optimization Of The Vertical Axis Wind Turbine

Vertical axis wind turbines(VAWTs)are attracting increasing attention in recent years for their ability to work in varied wind directions,lower center of gravity,higher adaptability to turbulent flows,easier manufacturing,lower installation & maintenance cost,reduced level of noise compared to horizontal axis wind turbines(HAWTs).In spite of these advantages,the relatively low power coefficient restricts the wide application of VAWTs.Effective solutions to this problem include improving design parameters of VAWTs and produce new airfoil profiles which directly influence the capture ratio of wind power.The main aim of the present study is to investigate the effects of different parameters on the aerodynamic performance of VAWTs and develop an automatic airfoil profile optimization system for VAWTs.This study firstly explores the influence rules of four parameters(number of blades,pitch angle,rotor solidity and blade aspect ratio)on the aerodynamic performance of VAWTs with the help of three dimensional CFD modelling.Then an automatic airfoil profile optimization system is developed with the objective of maximizing the power coefficient of certain VAWT.It is based on the Multi-Island Genetic Algorithm(MIGA)and contains modules of parametric modelling,meshing,numerical calculation and post-processing.This highly adaptive system investigates the airfoil as part of a three-blade VAWT rather than as a single isolated component which distinguishes it from optimization methods in other papers.To the author's knowledge,there has been no report on such work in this field which involves both MIGA and 3D CFD simulation techniques.The results can be divided into two parts.On one hand,the influence rules of the four parameters mentioned above on the power coefficient and the optimum tip speed ratio have been revealed.On the other,compared to the initial airfoil,the maximum thickness of the optimized airfoil increases by 12.8%.The radius of the leading edge is enlarged while the angle of the trailing edge shrinks.The power coefficient of the VAWT equipped with the optimized blades sensibly improves at all tip speed ratios(TSRs)and the maximum growth rate of it occurs at TSR=0.9 with a value of 26.82%.Overall,this optimization system provides an effective way to generate suitable airfoil profiles for given VAWTs with the goal to achieve higher power efficiency.