This invention relates to wind power engineering, namely to vertical axis wind turbines which may be used in wind electrical generators or equipments for conversion of wind energy into electrical energy.

Rotor of prior art for wind turbine is known from Russian Federation patent application No. 2135824, IPC⁶ F03D7/06, filing date 09.10.1996, publication date 27.08.1999. Known rotor of wind turbine comprises two S-shaped blades mounted on vertical shaft. S-shaped blades are fastened on rotatable paralel cross-arms which are rigidly connected with vertical shaft. Moreover the fastening points of blades are aligned with the axis of symmetry of the blade behind of its centre of gravity in direction away from the vertex of the S-shaped blade.

A disadvantage of the above described known rotary wind turbine resides in the complexity of rotary design, low power range and relatively low efficiency.

Another rotary wind turbine with vertically positioned shaft is known, e.g., from Russian Federation patent application No. 2096259, IPC⁶ B63H13/00, filing date 15.11.1993, publication date 20.11.1997 (prototype), which is provided with lower and upper disc type washers and mechanism for rotating of blades. Axis of washers is aligned with vertical axis of rotation. On lower end faces of blades there are fastened position locators with possibility to engage them with holes made in said washers. The said mechanism for rotating of blades comprises an element, which is fixed to the rotor shaft, situated on lower washer. A vertical rotor comprising two blades on each arm is known from the document EP-A-679805.

A disadvantage of the said known wind turbine resides in insufficient reliability, insuficient power range and insufficiently high efficiency.

An object of the present invention is to increase efficiency and power owing to provision of high rotation speed of rotor and to improve starting acceleration of the rotor.

According to the present invention there is provided a vertical axis wind turbine which comprises rotor provided with a plurality of arms mounted at equal angles round the vertical axis and a plurality of blades connected to the blocks and in cascade, characterized by that the number of the blade blocks is selected from the following number range: two, three; the blade blocks are provided with four cascaded blades, the said cascaded blades in the blocks are displaced in respect to the symmetry line of each block in the direction of rotation of rotor.

It is advisable to provide the wind turbine with two blade blocks and four cascaded blades in each block so that the said cascaded blades in the blocks are displaced in clockwise direction in respect to the symmetry line of the said two blocks; or in other embodiment thereof it is advisable to provide the wind turbine with three blade blocks and four cascaded blades in each block so that the said cascaded blades in the blocks are displaced in clockwise direction in respect to the symmetry line of the each block.

The invention may be better understood from the following detailed description of an embodiment thereof due reference being made to the accompanying drawings, in which:

• Figure 1 shows schematic view cascaded configuration of blades;
• Figure 2 is a top view of wind motor rotor; and
• Figure 3 is a blade profile.

Vertical axis wind turbine comprises rotor 1 provided with two symmetrical arms with blocks 2 and 3 of aerodynamic cascades whereinto each block advantageously consists of four blades 4 realized in the form of a turbine-type configuration of blades. Arms with blocks 2 and 3 of aerodynamic cascade are mounted on central vertical shaft 5 at equal angles around thereof, namely at 180° one from another. Blade profiles are in the form of subsonic aerodynamic profiles (Figure 3). Figure 2 shows that the cascaded blades 4 in the block 2 and accordingly the cascaded blades 4 in the block 3 are displaced in respect to the symmetry line O-O of the said blocks 2 and 3 in the direction of rotation (shown by arrow) of the said rotor 1. The rotor I of described embodiment of wind turbine is shown rotating in clockwise direction. Efficiency of the suggested design of rotary cascaded wind turbine is determined by selection of the lead (γ) of blade, mounting angle (ϕ_p) of cascaded block, cascaded blade deflection (χ), value of the shading factor (K₃) and value of the chord of blade profile (b). It is established that values of the said parameters may be in the range of:

• lead (γ) of blade: 0.4 to 0.6 b;
• mounting angle (ϕ_p) of cascaded block: 0 to 5°;
• cascaded blade deflection (χ): 0.4 to 0.6 b;
• value of the shading factor (K₃): 0.3 to 0.5;

in which:

• b - value of the chord of blade profile.

However it is established in the process of testing of models equipped with subsonic aerodynamic blade profiles that the optimum values of the said parameters are as follow:

• γ = 0.5 b;
• ϕ_p = 0°;
• χ = 0.5 b;
• K₃ ≤ 0.5;

Value of the chord (b) of blade profile is determined in dependance of number (Z) of blade profiles, selected values of shading factor (K₃) and diameter (D) of the rotor of wind turbine. It is established that that the optimum numer of cascaded blocks equals to two, but optimum range of number (Z) of blade profiles in each block does not exceed four. However the number of cascaded aerodynamic blocks of wind turbine may be determined on conditions that the value of the shading factor K₃ ≤ 0.5. According to the requirements of strength and power efficiency the most expedient number of blocks equals to two or three.

Rotary cascaded wind turbine may be used in the most efficient way as a large power wind turbine having dimensions: diameter D ≥ (6 ÷ 10) m; height H = (1.0 ÷ 1.5) D.

Single-unit power (Ñ) of one row of aerodynamic blade profiles at optimum mode of operation may be determined by experimental dependence: $$\begin{array}{||}\hline \bar{\mathrm{N}}=\mathrm{N}/\mathrm{S}=\mathrm{a}\times \mathrm{\rho }\times {\mathrm{U}}_n^3/{10}^3\mathrm{\hspace{0.17em}}\left(\mathrm{kw}/{\mathrm{m}}^2\right),\\ \hline\end{array}$$

in which:

• N - total power of one row of two blocks,
• S - total area of blades arranged in one row of two blocks;
• U_n - peripheral velocity of blades arranged in one row of two blocks (m/sec);
• ρ - air density (kg/m³);
• a - efficiency factor of aerodynamic characteristics of cascaded blade profiles; this factor is determined during testing of full-scale wind turbines being equipped with specific blade profiles.

Rotor of wind turbine is rotating under action of wind actuating electrical generator or other equipment (not shown), ensuring conversion of wind energy into electrical or mechanical energy.

The wind turbine equipped with cascaded block in turbine-type configuration of aerodynamic blade profiles according to the results of testing of models allows:

• significantly to increase efficiency of wind turbine due to the more effective making use of aerodynamic characteristics of blade profiles in turbine-type configuration; practically the efficiency is more than 0.8 (ξ_max ≥ 0.8 );
• to increase power of wind turbine due to keeping up specific speed of rotor because of widening of the variable range of value of the shading factor (K₃) up to K₃ ≤ 0.5 instead of K₃ ≤ 0.3 since it was in connection with rotary wind turbines of prior art;
• to improve starting acceleration of the wind turbine due to making use of turbine-type configuration of cascades.

Further improvement of power parameters of wind turbine may be achieved by improving aerodynamic properties of subsonic blade profiles used in turbine-type cascades of wind motors by means of using of mechanization devices for blades, e.g., by means of using of leading-edge flap, trailing-edge flap, discharging facilities of boundary layer etc.

The wind turbine in accordance with the present invention is industrially applicable due to the fact that the said wind turbine may be manufactured and widely used in production of vertical axis wind turbines for converting wind energy into electrical or mechanical energy.