Description

Wind turbine with application of several aerodynamic effects

Technical Field

[1] Wind turbine with application of several aerodynamic effects relates to alternative sources of power, namely vertical axis wind turbines, which convert kinetic energy of moving air into electric one by means of interaction of the air motion with the turbine actuating medium. Background Art

[2] The turbine actuating medium of known vertical axis wind turbines commonly feature blades or disk rotor having axis of revolution normal to the ground surface plane, wherein the rotor has certain shape or / and surface gradient being designed in the way that when air passes through the turbine in arbitrary direction the drag torque caused by interaction of air with the rotor is different on either side of it with respect to frontal air motion, thus the torque difference results in rotor spinning and passing the rotation to generator. The existing vertical axis wind turbines might also have stator wind guiding blades which redirect the air current in order to create the rotation torque or / and increase the efficiency of wind turbine. There are also vertical axis wind turbines with rotors being supported on magnetic platforms so to reduce the friction force caused by weight acting on the axis aiming to result in increased efficiency. Disclosure of Invention Technical Problem

[3] One of the disadvantages of existing vertical axis wind turbines is that the side of a rotor, which rotates against wind direction, i.e. where drag should be minimized, will always cause certain drag decreasing in such a way the difference of torques on opposite sides of rotor, which results in loss of certain quantity of energy and hence, the efficiency of such system is also decreased. The existing solution for the disadvantage to only guide wind current on one side of the rotor with stator blades reduces the strength of the wind current interacting with rotor due to stator blades own surface drag, thus reducing the efficiency of wind turbine. Another disadvantage of existing wind turbines arises from weight of rotor of appropriate size to achieve maximum efficiency, as it has high friction with stator supporting elements losing in such a way efficiency by spending certain energy on friction. Known solution to avoid high friction of rotor with stator supporting elements involves magnetic levitation of the rotor, yet magnets providing sufficient magnet induction on its own have considerable weight, which adds to rotation resistance torque of a rotor and leads to certain loss of a potential wind energy, which could be otherwise generated.

Technical Solution

[4] The present invention suggests providing technical solution to the above-mentioned problems as well as generally increasing efficiency of wind turbine by means of certain application of a number of aerodynamic properties, such as: aerodynamic lift, vorticity and Coanda effect etc. The rotor assembly represents thin flat blades of sufficient lift surface area being connected by membrane, which is meant to keep pressure difference over and under the rotor surface different; wherein the blades flatness plane is parallel to rotation plane; wherein the rotor is placed between stator airfoils of proportional size; wherein the distance between upper rotor surface is smaller than the bottom one, hence as per Bernoulli equal air speed over and under rotor surface results in lower pressure over the top rotor surface and in upward aerodynamic lift accordingly. This reduces the friction between the rotor and stator supporting elements. Said airfoils have slightly bigger area than said blades rotor swept area and specific profile which generate vortex current just before the leading edge of the blades rotor, which results in amplification of kinetic energy of incoming wind current and due to the skin friction with blades rotor surface accelerates its rotation. Said airfoils have a round shape offset the projected blades rotor swept area, thus, due to Coanda effect, i.e. air sticking to the surface and following its shape, more air is guided towards the blades. In order to create a rotation torque on side of the rotor respecting the rotation axis is fully covered from frontal wind currents by air intake of redirecting duct. Said redirecting duct is placed underneath the rotor and roughly occupies the half of the rotor swept area and narrows its cross sectional area from the front intake till the outlet; wherein as per Bernoulli accelerating the outgoing velocity of air motion; wherein the duct being curved in such a way that its outlet vector points against the wind current and its horizontal component (i.e. in the rotor rotation plane) accelerates the rotor rotation and its vertical component pointing at the rotor bottom surface provides lift. Said redirecting duct is integrated in said airfoil, i.e. being stator with respect to the rotor. Said arrangement provides the rotor spinning as one side of with respect to rotation axis is subjected to direct frontal wind current interaction as well as being accelerated from top and bottom by vortex flux created by airfoils and another side of it being fully covered with respect to frontal wind current by the duct air intake and and being lifted and rotated in the same rotation direction due to the curved shape of the redirecting duct. Said stator assembly with respect to the rotor, however is guided, so that air intake cross section plane is always facing towards the wind frontal current by the rudder being fixed to the airfoils and duct accordingly and connected to a definite ground stator supporting element by means of bush with bearings; wherein said stator assembly can be rotated around the rotor rotation axis when wind changes its azimuth and the rotor rotates when there is a wind current in arbitrary direction. The suggested

wind turbine can represent a number of said blades rotor and relative to it stator elements being placed one above another; wherein numerous rotors being connected to the same shaft would provide bigger capacity of such a wind turbine arrangement. The relative stator elements can be, therefore reinforced by thin beams. Advantageous Effects

[5] Main advantage of technical solution claimed is the use of complete frontal with respect to wind current cross section area, i.e. engaging both sides of actuating medium - blades rotor respecting the rotation axis at the same time due to direct exposing of half of it to wind current and its rotation amplified by vortex fields generated by airfoils and indirect use of air mass moving on other side due to curved duct system, i.e. where the outgoing stream of air would still follow the rotation direction at the exposed part of the rotor. The claimed wind turbine also benefits from rational aerodynamic lift solution on either side of the rotor as described in previous chapter, resulting in minimization of weight load on the shaft thus reducing the friction and increasing efficiency. The advantage of said stator elements with respect to the rotor being independently movable by the rudder is that it will always follow the wind direction which maximizes efficiency. Description of Drawings

[6] The claimed wind turbine, hereafter depicted on the following figures:

[7] Figure 1 - shows top view of the claimed wind turbine with main elements causing rotor rotation;

[8] Figure 2 - shows the look of rotor blades with membrane;

[9] Figure 3 - shows profile view of airfoils acting as vortex field generators and pressure difference creators and the rotor;

[10] Figure 4 - shows side view and principle of action of redirecting ducts;

[11] Figure 5 - shows rear exploded view of rotor, airfoils, redirecting duct and lift torques acting upon the rotor;

[12] Figure 6 - shows perspective front view of the claimed wind turbine with a number of blades rotor arrangements and stator elements;

[13] Figure 7 - shows perspective view of the complete assembly of the claimed wind turbine mounted on the roof of a building.

[14] As shown in Figure 1 air moving in direction (1) spins blades rotor (3) and membrane (4) connected to blades (3) in direction (2), as due to redirecting duct air intake (7)resulting in front plane coverage (better explained by Fig.4 and Fig.6) the direct influence of air stream only takes place on one side of the rotor and as the redirecting duct ejects air in direction (13); wherein the rudder (24) with chord tending to be parallel to wind direction being connected airfoils (6) with integrated duct (7)

follows wind azimuth change moving airfoils (6) and duct (7) accordingly. It is also seen how airfoils (6) having round edge shape guide airflow towards tangent to the rotor blades (3) rotation (2) in direction (5) caused by the Coanda effect.

[15] Figure 2 demonstrates perspective look of flat thin blades rotor (3) being surrounded by membrane (4) and fixed to shaft (18), the membrane (4) is spread around the blades rotor swept area.

[16] The airfoils (6) profile shown in Figure 3 being thicker at offset the projected blades

(3) swept area create vortex layers (8) due to air motion (1) and as the airfoils (6) are positioned at certain vortex interaction distance from blades rotor (3) rotation plane they accelerate its rotation by vortex flux (9). It is also shown that the distance (10) between upper rotor (3) surface and airfoil (6) above it is smaller than the distance (11) between bottom rotor (3) surface and airfoil (6) below it, which with effect of air motion (1) results in upward lift force (12) created as per Bernoulli.

[17] Figure 4 shows that redirecting duct (7) prevents frontal wind current (1) interact directly with blades rotor (3). The ejected by duct (7) air stream (13) vector in side plane is split into horizontal (14) and vertical (15) components; wherein horizontal component (14) provides additional rotation momentum to blades (3) and vertical component (15) provides lift to blades rotor (3).

[18] The blades rotor (3) and airfoils (6) exploded view shown in Figure 5 explains how lift torque (16) caused by aerodynamic lift (12) due to interaction of blades rotor (3) with airfoils (6) is countered on opposite side of the rotor (3) by torque (17) emerging from ejected by the duct (7) air upwardly (15), thus torques (16) and (17) eliminate or reduce twist of blades rotor (3) and provide overall lift to it.

[19] Figure 6 represents complete assembly of suggested wind turbine with moving parts:

2 blades rotors (3) with membranes (4) fixed to the shaft (18), relative to the rotors (3) stator parts, which are redirecting ducts (7) integrated in airfoils (6) being fixed with rudder (24) and supporting beams (23); wherein relative stator parts are supported by absolute stator part such as tower (20) via bearings (21) and bush (22) fixed to beams (23), hence when wind changes its azimuth the motion is passed via rudder (24) to all relative to the rotor (3) parts.

[20] Figure 7 shows convenient application of the claimed wind turbine being mounted on a building (25) via absolute stator supporting element tower (20) and gearbox/ generator (19) being actuated by shaft (18), which rotation is caused by the above- described arrangement of elements due to air motion (1). Best Mode

[21] The above described execution of vertical axis wind turbine should be preferably placed on a tower or a building with certain height from earth surface, where wind current strength is higher, hence the efficiency of wind turbine is also higher. Fair

attention should be drawn on the coating, namely surface roughness of the elements in any way interacting with moving air. The moving parts, such as flat blades rotor(s) and membranes surrounding it (them) should be coated with high skin friction materials as well as being executed with turbolence-creating surface relief, whereas redirecting duct and airfoils surface should be of as low drag as possible, thus more kinetic energy of the moving air will be passed onto moving parts. The airfoils curvature shape in the aft section of wind turbine will provide more efficiency by guiding air at tangent to rotation of blades rotor due the Coanda effect. Preferably the system should have number of the rotors with corresponding relative stator elements. Mode for Invention

[22] The invention comprises: thin flat large area blades rotor with membrane around its swept area; wherein the rotor is placed between airfoils of rotor offset area size at a distance of vortex interaction; wherein said airfoils have profile thickness at the rotor offset leading edge, thus due to the air moving through creating vortex flux above and below the rotor surface; wherein the airfoil above is closer to the rotor area than the below one, thus resulting in the rotor being sucked upwards and reducing own weight load. In order to allow wind current only affecting one side of the rotor with respect to rotation axis the system is fitted with redirecting duct placed beneath the rotor; wherein said duct has large opening at the front plane of the wind turbine; wherein the other end of said duct being directed against original wind current direction thus ejecting it at certain angle on the rotor surface accelerating its rotation and providing lift. Said duct system is integrated into the airfoils which are connected by beams and rudder; wherein the beams below are fixed to a bush, which is connected to stator supporting tower via bearings. Hence, wind changing its azimuth would move the rudder along with airfoils and duct and wind current would rotate the blades rotor which would pass its rotation on to generator. Industrial Applicability

[23] The suggested wind turbine with application of several aerodynamic effects can be mounted on the tower just as most of existing wind turbines are as well be mounted in a practically convenient way on a roof of a building, allowing wider urban application. The present invention can also be mounted on large ships and hence used as wind power generating unit, obviously with no polluting emission. Sequence List Text

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