Investigation On Straight-bladed Wind Turbines

With the development of technology and the improvement of knowledge level, Wind Power Generation are now widely used all over the world as a renewable energy source.Mostly they are divided into two kinds:horizontal axis wind turbine(HAWT) and vertical axis wind turbine(VAWT).Compared with HAWTs,VAWTs have their obvious advantages.Comparisons between VAWT and HAWT,both of them have the same theoretical basis in the design aspect.However,Both of them has different in the aerodynamic performance,and the way designed the VAWT is impossible used completely as the way of HAWT.How to get better aerodynamic performance arouses lots of interests in the design of VAWT.Even though many home and abroad scholar reached the main effects of the aerodynamic performance of the VAWT in many aspects,the design theory is not perfect.In this paper,it is investigated on the design parameter of straight-bladed VAWT affect the aerodynamic performance,the optimization of wind turbine,airfoil and wind turbine simulation method.The main contents include four parts as follows:1.The aerodynamic performance of a straight-bladed vertical-axis wind turbine(VAWT) is calculated and compared with the experimented data based on singe stream tube model,multiple stream tube model and double-multiple stream tube model by means of MATLAB software.The computer code can be use to analysis the relation between the power and power coefficients and tip speed ratio and wind turbines solidly.2.An optimization model for straight-bladed Darrieus-type vertical-axis wind turbines is presented.It referred to the wind speed distribution function on the specific wind site,with the objective to satisfy the maximum annual energy output,using genetic algorithm to carry on the search process.3.In order to improve CFD simulation aerodynamic characteristics of wind turbine more accurately,especially the 2-D drag coefficient of the wind turbine airfoil. In this paper,for solving the N-S equations,different models,different grid distributions were employed to be discussion the affect the calculates accuracy.4.In order to analyse the flow field characteristics of straight-bladed VAWT. Numerical simulation on unsteady rotated flow of a straight-bladed VAWT is done based on moving meshes by means of the software FLUENT,its wake velocity and the variation of velocity at the special cross-section are obtained. The results of unsteady flow are compared with ones solved by the multiple stream-tube model,at the same time,Comparison simulation result between 2-D and 3-D model,and analyse the different between them.The following conclusions can be obtained according to study and analyze:1.Double-multiple stream tube model is more suitable in design of a VAWT.Effects of tip speed ratio and solidity on power coefficient of a straight-bladed VAWT are also discussed.The computational results indicate that power coefficient curves are in approximate parabolic forms with maximum values with respect to tip speed ratio and solidly,and maximum efficient points move towards low tip speed ratio area and high efficiency areas narrow with the increase of solidly.2.It showed obviously for the equation that the close relation between aerodynamic performance and solidity and tip speed ratio based on the Double stream tubes model.So an optimization model for straight-bladed Darrieus-type vertical-axis wind turbines is presented.algorithm to carry on the search process.Based on the developed optimization program,a wind turbine are designed,Compared with an existing wind turbine,the design shows obvious advantages,which verifies affectivities and functionalities of the optimization model.3.The solution of the airfoil's drag coefficient is more accurate for using k-ωsst model,The calculation precision strongly depends on the apart mesh near the boundary layers.This study has laid a foundation for further research about numerical simulation of straight-bladed VAWT.4.The results of unsteady flow are compared with ones solved by the multiple stream-tube model,and they have the coincidence each other.The conclusion can be made that the 2-D and 3-D numerical simulation on unsteady rotated flow of a straight-bladed VAWT based on moving meshes can present its flow field.The 3-D model numerical simulation calculation need large quality,however,but its can find essence of the blade tip loss.