Fluid Performance Analysis Of Offshore Variable-pitch Vertical Axis Wind Turbine

With the offshore wind power technology gradually mature, the stationary offshore windpower of inshore shallow water area has been rapid developed. In order to make full use of marinewind energy resources, the European countries have launched floating offshore wind powerresearch and experiments, the proposed floating wind power scheme mainly take horizontal axiswind turbine as the object to design the floating foundation. But with the increase of wind turbinepower, its weight and dimension is very big, it should be undertook by a large floating foundation.Due to the horizontal axis wind turbine mutual interference is bigger, a set of foundation only canundertake the installation of one wind turbine, and the resistance ability of sea waves is poor, theconstruction of the wind power cost will be unbearable.Vertical axis wind turbine (VAWT)as the object of study, in order to reduce the cost ofoffshore floating foundation and enhance the resistance ability of sea waves，a new cluster balloonwind turbine system was designed in this paper. To achieve this goal, we must carry out VAWTfluid performance study and explore the mutual interference law of cluster VAWT flow field.According to the working environment and requirements, the VAWT design scheme was putforward. In order to improve its wind energy utilization, a variable propeller mechanism wasdesigned to make the blade keep the best angle of attack in the arbitrary position of the rotationcircumference. And using MATLAB software to comparison and analysis the change of outputtorque when the blade had took this way or not. The results show the output torque in the highestdirection can be increased by25%, and reduce the resistance moment downwind direction.The2D numerical simulation of a single VAWT in the uniform flow was carried out to studyand analysis its fluid performance. Base on the result, the velocity field and pressure fielddistribution situation and each blade pressure were analysised. The results show that the embeddedsliding meshes technology simulation can well reflect the flow field of the variable-pitch VAWT.Due to the actual wind field has different velocity in different height, the single wind turbinewhose inlet velocity had a gradient change in the height direction was implemented. The resultsshow that, the blade pressure distributes symmetrically along the elongation direction, the lateralpressure change has diversity. Considering the influence of3D tip loss,the3D simulation can wellreflect the fluid performance of the VAWT. With the height increasing, the wake flow diffusionlength increases gradually.The flow fields of six VAWT in hexagon arrangement whose separation distance were from100m to600m were simulated to study the mutual interference law. The results show that, there are some advantageous interference for the cluster VAWT in the small spacings, and the flow fieldinterference reduces with separation space increasing, but the impact is not big. From100m to600m, its overall average output torque influence within11%. When the separation space is400mand600m, advantageous interference exists in the flow field, the overall average output torque hasrebounded.