DESCRIPTION

The invention relates to a vertical axis wind rotor equipped with a plurality of inclined blades.

The wind rotor of the present invention having blades inclined at about 45° relative to the axis and orthogonal to one another is a fast-type rotor, as it has a ratio between peripheral speed and wind speed higher than 1 (this ratio is known as ratio λ in techno-scientific literature) ; such ratio can be up to values of 2.5, with specially devised parameters .

In the rotor as shown in Figure 1, the three blades 1 are arranged at an angle a of 120° relative to one another and are inclined at an angle β of 45° relative to the vertical axis of rotation Y-Y and are mutually perpendicular. According to the invention, the angle β can range between 30° and 60°.

Each of the three blades 1 consists of two parallel elements 1A, IB having the same aerodynamic profiles. According to the invention, the elements 1A, IB are mounted suitably spaced from each other, this condition allowing self-starting of the rotor even with modest wind speeds.

Due to its particular configuration (sub-vertical impeller), the rotor, which during rotation is much faster than the wind stream, causes a phenomenon of secondary induced flow with respect to the main stream flow, said secondary induced flow enveloping the entire upper circular area of the rotor and arriving at the inner conical area between the blades, yielding a further amount of kinetic energy of the flow to the blades, whereby the power delivered to the shaft 2 of the wind-power generator associated to the rotor is remarkably increased.

The entity of this particular phenomenon with consequent remarkable overall efficiency of the system depends on several parameters such as, for instance, the instantaneous wind speed, the shape of the blade profiles, the length of the blades, the distance between the profiles and so on. An optimization of the rotor characteristic quantities which is valid for a wide range of values is not easy to achieve; this problem has been solved through several, systematic experiences carried out at various wind sites and with different parametric values integrated with sophisticated CFD (Computer Fluid Dynamics) systems; in this way it was possible to achieve application developments that allow satisfactory results for the whole operating range of the wind turbine.

Owing to the fact that the rotor is very fast, the centrifugal forces arising on the blades 1 have remarkable values, which greatly stress the entire structure and more particularly the section at which the rotor are wedged in the base of the rotor.

In order to limit the structural deformations and have low stress upon wedging, a tie-rod 3, preferably an adjustable tie-rod, is provided on each of the three blades, which tie- rod connects the upper end of the blade 1 in a point Lb and the central hub 4 in a point Mh.

Through the connection between blades 1 and tie-rod 3 the rotor acquires high rigidity that allows safe operation thereof at high rotational speeds Or that characterize this type of machine, whereby the field of application of the rotor also extends to very fast winds, which can become a critical factor for the application of other types of rotors .

Figure 2 shows the schematic cross section of composite blades 1 consisting of two parallel elements 1A, IB equipped with blade profiles having a length equal to the chord C with their respective median planes P spaced apart by a distance "dl" having a value from 0.2 to 1.2 times the chord C and staggered at their respective leading edges Bt by a value "d2" from 0.1 to 0.8 times, and preferably 0.4 times, the chord C. With this range of dimensional ratios it is possible to obtain the best aerodynamic efficiency values of the rotor and high performances.

In practice, the rotor which is the subject matter of the present invention combines all the aerodynamic advantages of horizontal axis fast turbines with the simplicity of vertical axis turbines, this type or rotor being a hybrid construction between the aforesaid two systems.