RU2307951C1 - Method of automatic control of wing of windmill with vertical axle of rotation - Google Patents

Abstract

FIELD: wind power engineering.

SUBSTANCE: invention contributes to development of ecologically clean methods of power generation. Proposed method of automatic control of wing of windmill with vertical axle of rotation provided with wings of symmetrical profile secured on radial cross members for articulation comes to mechanical limiting of angle of their turning and displacement of hinge axle along wing chord towards wing tip. Center of gravity of wing is displaced to perpendicular to wing chord passing through axle of hinge joint to outer side relative to center of rotation of rotor. To provide self-acceleration of windmill, angle of wing turning on hinge axle is limited. Advantage of proposed automatic control method of windmill wing is dispensing with complex mechanical devices and provision of high efficiency.

EFFECT: simplified design of windmill and reduced cost of production.

2 cl, 2 tbl, 4 dwg

Description

The invention relates to wind energy and contributes to the development of environmentally friendly methods of generating energy.

A wind turbine is known in which a method of automatically controlling a wing with a vertical axis of rotation with wings of a symmetrical profile mounted on radial traverses is pivotally mounted, while the axis of the hinge is shifted along the chord of the wing towards its nose (see, for example, RU 2235901 C2, class F03D 3/00, 09/10/2004, 6 pp.), Based on the set of essential features adopted for the closest analogue of the invention (prototype).

The disadvantages of the prototype include the complexity of the design and the ability of the wing to work effectively only on the windward side.

The technical result consists in providing such a method of automatic control of the wing, which provides effective traction of the wing over the entire circle swept by it, as well as in simplifying the design.

A method of automatically controlling a wing of a wind turbine with a vertical axis of rotation with wings of a symmetrical profile pivotally mounted on radial traverses, mechanically limiting the angle of rotation and shifting the hinge axis along the wing chord towards its nose, and the center of gravity of the wing is shifted perpendicular to the wing chord, passing through the hinge axis to the side external from the center of rotation of the rotor.

To assess the capabilities of any wind turbine, wind power can be represented by the formula

where S is the area of the wind flow;

ρ is the air density;

V _in - wind speed.

The density of air at 0 ° C and a pressure of 760 mm Hg equal to 1.293 kg / m ³ . The power of the wind flow passing through 1 square meter of the surface will be

The efficiency of a wind turbine depends on what part of this energy can be taken.

Consider the conditions in which the wing is moving around the circumference (see figure 2). For a high-speed wind turbine, the peripheral speed V _{0 is} significantly greater than the wind speed V _c . The speed V of the wind flow acting on the wing will be the sum of the wind vector V _in and the peripheral speed V ₀ , and β is the angle between the tangent to the circle and the current wind. When the wing moves in a circle, the angle β and the modulus of the velocity of the acting wind V will change. Replacing the effective velocity by its relative value

we get

where γ is the angle of the wing on the circle;

n is the ratio of peripheral speed to wind speed;

V _n - the ratio of the current speed to wind speed.

The graphs (see figure 3) show that when n is greater than unity, the wing works with the sharp corners of the current wind. To ensure positive wing traction along the circumference, the angle α must be greater than zero and less than the wind angle β. Naturally, in this interval there will also be an optimal value of the angle α. The limitation of the rotation of the wing within 20 degrees provides independent acceleration of the wind turbine, since the above condition will be fulfilled on most of the circumference.

As the wind turbine accelerates, the mechanical stops will cease to act, since the angle α at n = 2 will be less than 20 degrees.

If we assume that the wing lift F is a linear function of the angle of attack

it is easy to obtain the optimal value of the angle of rotation of the wing

where α is the angle between the chord of the wing and the tangent to the circle.

As an example of the possible use of the proposed method for automatic wing control, figure 1 shows a wind turbine with a vertical axis of rotation, where the following notation is accepted:

1 - a rotor shaft of a wind turbine;

2 - profiled wings;

3, 4- radial traverses;

5 - plate with cutouts that limit the angle of rotation of the wing;

6 - weight, shifting the center of gravity of the wing;

7 - pin, restricting the rotation of the plate;

8 - wing hinge bearing;

F - focus of the wing.

On the hubs of the vertical shaft 1 there are fixed radial traverses 3, 4, which together with the wings 2 rotating in hinges 8 form a rotor. The pin 7, located in the cutouts of the plate 5, limits the rotation of the wing. A weight 6 provides a shift in the center of gravity of the wing 2.

In the proposed method for automatic wing control, displacement of the hinge axis to the nose of the wing provides a moment tending to put the wing in a weather vane. At the same time, the shift of the center of gravity from the center of rotation behind the wing by centrifugal force tends to put the wing along the tangent to the circle. This moment is represented by formula (7)

where R is the radius of the circumference of the rotor,

m is the effective displacement mass;

V ₀ - the linear speed of the wing,

α is the angle between the chord of the wing and the tangent to the circle;

r ₂ is the distance between the center of gravity and the axis of the hinge.

The vane moment is

where r ₁ is the distance from the focus of the wing to the axis of the hinge;

F _p - the lifting force of the wing.

In aerodynamics, the wing is characterized by lift and drag

where S is the wing area;

ρ is the air density;

V is the air velocity;

With _y is the aerodynamic coefficient of lift;

C _x - aerodynamic drag coefficient;

F _l - drag.

The coefficients C _y and C _x depend on the wing profile and angle of attack.

Typically, the coefficients C _y and C _x according to the results of the purge are given in tabular form as a function of the angle of attack.

The vane and centrifugal moments are directed towards each other, then you can get the equation

Expressing speed through the ratio

V = V _n · V _in , V ₀ = n · V _in ,

we get

The coefficients C _y and C _x are a function of the angles β and α. The relative speed V _n and angle β depend on n and the position of the wing on the circle φ.

Equation (11) is transcendental and is solved numerically with respect to angle α. In a real device, the angle α is set automatically when the centrifugal and aerodynamic moments are equal.

Knowing the angle α, it is easy to obtain the useful force acting along the circle

Instant power will be

Average power can be imagined

where K is the number of measurements on the circle with a step Δφ,

P _i is the instantaneous power value.

To confirm the effectiveness of the proposed method for automatic wing control, mathematical modeling was performed.

As the initial parameters, a wing with an area of one square diameter with a NACA 0009 profile, rotor radius R = 0.5 m was adopted. The hinge offset relative to the focus is r ₁ = 5 cm. The center of gravity shift is r ₂ = 5 cm. The weight of the weight of the center of gravity is ranged from 5 grams to 20 grams. The functions of the coefficients C _y and C _x from the angle of attack are given in a table. Table 1 for the weight of the weight 10 shows the calculated values of the angles β, α and the relative speed V _n depending on the parameter n and the angle of the wing position on the circle (formulas 3, 4, 11). Table 2 shows the calculated values of instantaneous power (formula 13) for the angles α from table 1 for the weight of the weight m = 10 g and P ₀ for the optimal angle

(formula 6),

when V = wind velocity _at 10 m / s. The bottom line of table 2 shows the average values of the respective capacities (formula 14). The graphs of figure 4 show the dependence of the average power on the parameter n and the mass of the weights of the displacement of the center of gravity. A power plot for a legally controlled wing is also provided.

.

.

As can be seen in these graphs, the maximum power is achieved when the ratio of the wing circumferential speed to the wind speed n≈5. Comparing the value of the average power of the proposed method of controlling the wing with the average power of control according to the law α _opt , we can conclude that the proposed method is highly efficient. Errors in the choice of the mass of the loads of displacements of the center of gravity are not critical.

The results of mathematical modeling allow us to conclude that the proposed method for automatic wing control is highly efficient. Efficiency of tens percent can be expected.

Table 1 m = 10 g n = 2 n = 3 n = 4 n = 5 FI be vn al be vn al be vn al be vn al 0 0.0 1.0 0.0 0.0 2.0 0.0 0.0 3.0 0.0 0.0 4.0 0.0 10 9.7 1.0 3.3 4.9 2.0 2.5 3.3 3.0 2.1 2.5 4.0 1.7 twenty 17.9 1.1 5.5 9.4 2.1 4.7 6.4 3.1 3.7 4.8 4.1 3.0 thirty 23.8 1.2 7.8 13.2 2.2 6.7 9.1 3.2 5.2 6.9 4.2 4.2 40 27.5 1.4 10.3 16.1 2.3 8.4 11.2 3.3 6.5 8.6 4.3 5.3 fifty 29.4 1.6 12.8 18.0 2.5 9.9 12.9 3.4 7.7 10.0 4.4 6.2 60 30.0 1.7 14.9 19.1 2.6 11.2 13.9 3.6 8.6 10.9 4.6 7.0 70 29.5 1.9 16.7 19.5 2.8 12.1 14.4 3.8 9.2 11.4 4.8 7.5 80 28.3 2.1 17.9 19.2 3.0 12.6 14.4 4.0 9.6 11.5 4.9 7.8 90 26.6 2.2 18.5 18.4 3.2 12.7 14.0 4.1 9.7 11.3 5.1 7.8 one hundred 24.4 2.4 17.9 17.2 3.3 12.3 13.3 4.3 9.4 10.8 5.3 7.7 110 21.9 2.5 16.7 15.7 3.5 11.6 12.2 4.4 8.9 10.0 5.4 7.3 120 19.1 2.6 15.0 13.9 3.6 10.6 10.9 4.6 8.2 8.9 5.6 6.7 130 16.2 2.8 13.1 11.9 3.7 9.3 9.4 4.7 7.2 7.7 5.7 5.9 140 13.1 2.8 10.9 9.7 3.8 7.8 7.7 4.8 6.1 6.4 5.8 5.1 150 9.9 2.9 8.5 7.4 3.9 6.1 5.9 4.9 4.8 4.9 5.9 4.0 160 6.6 3.0 5.8 5.0 4.0 4.2 4.0 5.0 3.3 3.3 5.9 2.8 170 3.3 3.0 3.0 2.5 4.0 2.2 2.0 5.0 1.8 1.7 6.0 1.5 180 0.0 3.0 0.0 0.0 4.0 0.0 0.0 5.0 0.0 0.0 6.0 0.0 table 2 M = 10 g V = 10 m / s n = 2 n = 3 n = 4 n = 5 n = 6 n = 7 FI P Po P Po P Po P Po P Po P Po 0 -0.1 -0.1 -0.7 -0.7 -2.0 -2.0 -4.4 -4.4 -8.2 -8.2 -13.7 -13.7 10 0.2 0.4 0.2 0.2 -0.8 -0.8 -2.9 -3.0 -6.5 -6.8 -11.8 -12.3 twenty -1.6 0.9 2.1 2.1 2.3 2.0 1.2 1.0 -1.5 -1.5 -6.1 -6.1 thirty -3.5 0.2 4.8 4.7 6.3 5.9 6.7 6.0 5.7 4.9 2.4 2.2 40 -4.2 -0.3 7.6 7.1 11.2 10.5 12.9 11.9 13.5 12.1 12.2 10.9 fifty -3.4 -0.6 10.9 6.7 16.4 14.8 19.3 18.1 21.3 19.6 21.8 19.7 60 -1.0 -0.9 14.4 6.4 21.1 18.6 25.2 23.7 28.3 26.5 30.0 27.7 70 2.8 -1.0 17.8 6.8 24.7 21.7 29.7 28.0 33.8 32.0 36.3 34.1 80 7.6 -0.8 19.9 8.0 26.8 23.8 32.3 30.7 36.9 35.4 39.9 38.0 90 12.6 -0.4 20.4 10.2 27.1 24.7 32.7 31.6 37.2 36.3 40.4 38.9 one hundred 12.4 0.6 19.3 13.6 25.5 24.3 30.8 30.6 34.9 34.5 37.6 36.7 110 10.8 2.1 16.9 15.4 22.3 22.5 26.8 27.3 30.1 30.2 31.2 31.4 120 8.7 4.3 13.7 13.9 18.0 18.9 21.3 22.1 22.8 23.7 22.2 23.9 130 6.4 6.7 10.1 11.2 13.0 14.1 14.4 15.7 14.1 16.0 11.7 14.5 140 4.2 5.2 6.3 7.6 7.4 8.8 7.1 9.0 5.0 7.5 0.7 4.3 150 2.1 3.1 2.8 3.9 2.3 3.7 0.3 2.3 -3.5 -0.8 -9.5 -6.6 160 0.4 1.1 -0.1 0.7 -1.9 -0.8 -5.1 -4.0 -10.2 -9.2 -17.4 -16.8 170 -0.6 -0.4 -2.0 -1.8 -4.5 -4.5 -8.5 -8.7 -14.4 -14.8 -22.4 -23.1 180 -1.0 -1.0 -2.6 -2.6 -5.4 -5.4 -9.8 -9.8 -16.0 -16.0 -24.4 -24.4 Pcr 2.9 1.1 9.0 6.3 11.2 11.2 12.8 12.7 12.4 12.3 10.1 10.0

Claims (1)

A method for automatically controlling a wing of a wind turbine with a vertical axis of rotation with wings of a symmetrical profile pivotally mounted on radial traverses, mechanically limiting the angle of rotation and shifting the hinge axis along the wing chord towards its nose, and the center of gravity of the wing is shifted perpendicular to the wing chord, passing through the axis of the hinge to the side external from the center of rotation of the rotor.

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