Abstract: On the basis of the analysis of the cause for low efficiency of the traditional vertical axis wind turbine(VAWT), the structure advantage of a new type of VAWT—Guiding VAWT is introduced. On that basis, a new blade shape called as combined blade for Guiding VAWT is proposed and numerical investigation is completed on its aerodynamic performance by computational fluid dynamics (CFD) technique. The guiding VAWT includes two components：Guiding impeller and rotating impeller, both are combined blade in shape. The guiding blade is composed of three sections, namely, radial section at inlet, linear section at outlet and the arc section tangent to the above two sections. The rotor blade consists of two sections: Arc section at inlet and linear section tangent to the arc section at outlet. The guiding impeller can not only prevent the rotating impeller from direct impact by the coming flow on its suction section of the blade so as to decrease the drag torque, but also improve the effective impact by the coming flow on the pressure section of the blade, both of which contributes to the enhancement of the driving torque of the wind turbine. Results indicate that the new type of guiding VAWT with combined blade has a wider operating range, higher aerodynamic efficiency than the traditional VAWTs. Moreover, the aerofoil blade is introduced into this new type of VAWT and the validation is numerically obtained that even though the flow inside the VAWT is a large separated flow with variable attack angles, the aerodynamic advantages of the aerofoil shape blade can still be shown, to some extent, which helps to enhance the aerodynamic efficiency of the VAWT. Furthermore, this new type of VAWT has an essentially planar structure, which is convenient for manufacture and has the potential of popularization.

Key words: Aerodynamic performance, Combined blade, Guiding impeller, Numerical investigation, Vertical axis wind turbine (VAWT), Belt grinding, Contact wheel, Cutting depth, Deformation, Robotic Machining