Vertical axis wind turbine blade and its wind rotor

A vertical axis wind turbine comprising blade(s) characterized in an airfoil cross section, wherein the top end and the bottom end of said blade(s) are rotationally off-set from each other, twisted up with a vertical line vertical to the horizontal plane.

TECHNICAL FIELD

The present invention relates to the structure of a vertical axis wind turbine (VAWT) blade and its wind rotor in the wind power generation field. In particular, this invention relates to the structure of the VAWT blade and its wind rotor.

BACKGROUND ART

At present, the wind rotor of a VAWT has the capability to compete with a horizontal axis three-blade wind rotor on efficiency. However, the wind rotor of the VAWT is hard to be started up without the help of external force. This has brought difficulty to the prevalence of this type of wind turbine.

VAWTs have an advantage over horizontal-axis wind turbines in that they do not need to be orientated into the prevailing wind direction. VAWTs are able to produce a rotational movement irrespective of the wind direction.

The blades can be subject to very high stresses. This is due to the centrifugal forces produced on rotation of the turbine at high rotational speeds. The noise levels can reach unacceptable grades, produced by large vortices shed at the blade tips, rotation of the turbine at high rotational speeds. As the blades alternate between crossing the wind direction and coasting, uneven torque may be produced from the lifting surfaces of VAWTs.

WO2005010355 discloses a VAWT comprising a shaft rotatable about a longitudinal axis and a plurality of substantially rigid blades mechanically coupled to the shaft, each of the plurality of blades comprising an elongate body having an upper end and a lower end, wherein the upper end and the lower end of each blade are rotationally off-set from each other about the longitudinal axis such that each blade has a helix-like form, the section of the elongate body of each blade, taken perpendicularly to the longitudinal axis, being shaped as an aerofoil having a leading edge and a trailing edge and a camber line defined between the leading edge and the trailing edge, characterised in that the aerofoil is accurately shaped such that the camber line lies along a line of constant curvature having a finite radius of curvature.

WO2009151359 discloses a wind turbine with vertical axis and having a plurality of axial extending turbine blades where the structure of each blade varies along the axial extension of the blade.

DEFINITIONS

SUMMARY OF THE INVENTION

Provided herein is a wind blade and wind rotor of a VAWT started up by breeze wind.

The VAWT comprises a blade. The blade(s) may be twisted up with a vertical line wherein said vertical line is vertical to a horizontal plane, to rotationally offset the top end and bottom end of the blade. The distances between the mentioned vertical line and the midpoint of the chord between leading edge and tailing edge of a series of airfoil cross sections of the mentioned blade may be the same or may vary (e.g., between 5 cm and 500 cm).

The VAWT may further comprise the wind rotor of the VA WT blade(s), connecting arm(s) the connecting arm(s) may be or may not be airfoil shaped, and the rotor shaft. Both ends of the mentioned connecting arm(s) may be connected with the mentioned blade and the rotor shaft respectively. Secured with the connecting arm(s), the blade(s) may be twisted up with a vertical line wherein said vertical line is vertical to the horizontal plane, to rotationally offset the top end and bottom end of the blade and the distances between the mentioned vertical line and the midpoint of the chord between leading edge and tailing edge of a series of airfoil cross section of the mentioned blade are the same. The line intersectant with the mentioned vertical line and midpoint of the mentioned chord in the same plane may form a set angle with the mentioned chord, wherein, the first line and the second line may form a set angle, and the mentioned first line may be the one intersectant with the mentioned vertical line and the midpoint of the chord at the top most airfoil cross section(s) of the mentioned blade, while the second line may be the one intersectant with the mentioned vertical line and the midpoint of the chord at the bottom most airfoil cross section of the mentioned blade.

Preferably, the mentioned wind rotor may be equipped with two or more blades and the vertical projection of the mentioned two or more blades may form a closed circle. More preferably, the mentioned wind rotor may be equipped with three blades, and the vertical projection of the mentioned three blades may form a closed circle.

The distance between the chord midpoint of the mentioned airfoil cross section to the mentioned vertical line may be the same as the length of the mentioned connecting arm width. The mentioned vertical line may be superposed with the axis of the mentioned rotor shaft, and the length of the mentioned rotor shaft may be less than or equal to the vertical distance between the top most airfoil cross section to the bottom most airfoil sectional circle in the mentioned blade.

In an alternative embodiment, the length of the mentioned rotor shaft may be more than or equal to the vertical distance between the top most airfoil cross section to the bottom most airfoil sectional circle in the mentioned blade.

The distance between the chord midpoint of the mentioned airfoil cross section to the mentioned vertical line may be the same as the length of the mentioned connecting arm airfoil. The mentioned vertical line may be superposed with the axis of the mentioned rotor shaft, and the length of the mentioned rotor shaft may be less than or equal to the vertical distance between the top most airfoil cross section to the bottom most airfoil sectional circle in the mentioned blade.

The mentioned line intersectant with the mentioned vertical line and midpoint of the mentioned chord in the same plane may form an angle of between about 30° to about 150° with the mentioned chord, wherein, the first line and the second line may form an angle of from about 50° to about 200°.

Preferably the mentioned line intersectant with the mentioned vertical line and midpoint of the mentioned chord in the same plane may form an angle of between about 70° to about 110° with the mentioned chord, wherein, the first line and the second line may form an angle of from about 80° to about 150°.

More preferably the mentioned line intersectant with the mentioned vertical line and midpoint of the mentioned chord in the same plane may form an angle of about 96°±1° with the mentioned chord, wherein, the first line and the second line may form an angle of about 120°.

Preferably said vertical line is super-positioned with the axis of the rotor shaft.

The mentioned blade may comprise an airfoil measurement of about FX63-137.

The mentioned blade may comprise an anti-symmetric airfoil with a high Lift/Drag ratio.

The mentioned blade(s) may form an outer concave and/or convex surface with respect to the central rotor shaft. Preferably the mentioned blade(s) forms an outer concave surface with respect to the central rotor shaft.

The distance from the bottom of the airfoil blade section to the point of the connecting arms attachment may be any distance along the length of the blade. Preferably the distance from the bottom of the airfoil blade section to the point of the connecting arm(s) attachment may be no more than about 1000 mm and in particular, between about 1000 mm and about 0.1 mm. More preferably the distance from the bottom of the airfoil blade section to the point of the connecting arm(s) attachment may be between about 800 mm and about 250 mm. Even more preferably the distance from the bottom of the airfoil blade section to the point of the connecting arm(s) attachment may be between about 760 mm and about 300 mm. Most preferably the distance from the bottom of the airfoil blade section to the point of the connecting arm(s) attachment may be about 753.5 mm, 490 mm or 305 mm.

The distance from the top of the airfoil blade section to the point of the connecting arm(s) attachment may be any distance along the length of the blade. Preferably the distance from the top of the airfoil blade section to the point of the connecting arm(s) attachment may be no more than about 1000 mm and in particular, between about 1000 mm and about 0.1 mm. More preferably the distance from the top of the airfoil blade section to the point of the connecting arm(s) attachment may be between about 800 mm and about 250 mm. Even more preferably the distance from the top of the airfoil blade section to the point of the connecting arm(s) attachment may be between about 770 mm and about 300 mm. Most preferably the distance from the top of the airfoil blade section to the point of the connecting arm(s) attachment may be about 766.5 mm, 490 mm or 305 mm.

The blade(s) may comprise for example a mixture of any one of the following; fibre glass or carbon fiber with epoxide resin, high strength glass, plastic, foam and/or metal. In an alternative embodiment, the blade(s) may have a secure material inside the length of the blade. The secure material may or may not be attached to the inside of the blade. The secure material may extrude outside of the blade, or be accessible from outside of the blade, at a point where the blade attaches to the connecting arm. At said point where the blade attaches to the connecting arm, the secure material may form a loop. Said blade loop may attach to a loop, extruding from the connecting arm through the connecting arm attachment piece, or located inside the connecting arm or attachment piece. Said connecting arm loop may be formed from secure material extending either the length of the connecting arm or no more than the length of the connecting arm. The loop from the blade and the loop from the connecting arm may be securely attachable to each other.

Alternatively, the secure material may exist in a loop through a lower connecting arm through the generator shaft, through the upper connecting arm and through the blade so as to form a closed loop. The secure material may comprise but is not limited to either one or more of rope, chain, metal, wire, string, nylon, rubber and or plastic.

In accordance with the above mentioned VAWT, the wind rotor is connected to the VAWT blade with above mentioned structure, along the vertical axis direction, the blade is twisted up from the bottom, and oblique torque will be produced at all windage of the blade when air comes from various directions, therefore, the wind rotor may self-start up and rotate with low wind speed. The twisted structure of the blade provides an area of surface, at substantially every angle. The blade design is such that wind, from substantially every direction, may be caught by the wind blade, forcing movement of the blade. Furthermore the blade design of the present invention provides a levelling of pulsating wind, hence lowering vibration. With implication of an alternative embodiment the above mentioned VAWT provides a safety feature to ensure the blades cannot become fully separated from the other parts of the VAWT.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereunder the present invention may be given further description on the mode of carrying out the invention with incorporation of the attached figures, wherein, the attached figures are only for reference and description assistance, which are not proportion or an accurate layout. Therefore, the actual mode of carrying-out the present invention may not be restricted by the proportion and layout relation indicated in the attached figures.

Provided herein is a VAWT blade, with the airfoil cross section, the mentioned blade may be twisted up along a vertical line, vertical to a horizontal plane, and the distances between the mentioned vertical line and chord midpoint of leading edge and tailing edge of a series of airfoil cross sections of the mentioned blade may be the same. Moreover, the line intersectant with the mentioned vertical line and the mentioned chord midpoint in the same plane may form an angle of 96°±1° with the mentioned chord, wherein, the first line and the second line may form an angle of 120°. The mentioned first line may be the one intersectant with the mentioned vertical line and chord midpoint at the top most airfoil cross section of the mentioned blade, and the mentioned second line may be the one intersectant with the mentioned vertical line and chord midpoint at the bottom most airfoil cross section of the mentioned blade.

According toFIG. 1,FIG. 4andFIG. 5, applying the above-mentioned blade into the wind rotor of the vertical axis wind turbine, the wind rotor may comprise blade101, connecting arm flat or airfoil102and rotor shaft103, and both ends of the connecting arm flat or airfoil102may be connected with the blade101and rotor shaft103respectively. Moreover, the complete appliance of the VAWT may include generator104, wherein, with airfoil cross section, the blade101may be twisted up along a vertical line, vertical to horizontal plane. The distances between the mentioned vertical line and chord midpoint of the leading edge405and tailing edge406of a series of airfoil cross sections of the mentioned blade may be the same, and the line intersectant with the mentioned vertical line and the mentioned chord midpoint in the same plane may form and angle of 96°±1°508with the mentioned chord, wherein, the first line and the second line may form an angle of 120°510. The mentioned first line may be the one intersectant with the mentioned vertical line and chord midpoint at top most airfoil cross section of the mentioned blade, and the mentioned second line may be the one intersectant with the mentioned vertical line and chord midpoint at bottom airfoil cross section of the mentioned blade.

During the fabrication and erection process of the blade, the distance between the chord midpoint of the airfoil cross section and vertical line may be set to be equal to the length of connecting arm usually, and the vertical line may be set to be superposition with axis of wheel axle. Such setup can decrease the drag torque of the blade, during operation, effectively. Preferably, three blades may be equipped for the wind rotor (as perFIG. 1,FIG. 2andFIG. 3), and the vertical projection of the three blades may form a closed circle307, so that wind from various directions may produce stronger oblique torque on windage of blade, and wind power can be utilized more efficiently to enhance the wind rotor self-start and rotation with low wind speed.

Based on for example FX63-137 airfoil or an anti-symmetric airfoil with high Lift/Drag ratio, the above-mentioned blade can be fabricated by methods as below.

With reference toFIG. 1,FIG. 2,FIG. 3,FIG. 4andFIG. 5a line segment L may be led from chord midpoint of leading edge and tailing edge of airfoil FX63-137, or an anti-symmetric airfoil with high lift/drag ration which forms an angle of 96°±1°508with the mentioned chord. Preferably the length R509of the line segment L may be set as the length of the connecting arm flat or airfoil102of the wind rotor (the length is called radius of wind rotor usually under such condition). A vertical line may be made to connect the terminal point of the mentioned line segment L and be vertical to the plane, in which the terminal point of line segment L may be the one to connect with the chord midpoint of the leading edge405and the tailing edge406of the airfoil cross section. The distance between the vertical line and the chord midpoint of the leading edge and the tailing edge of the airfoil cross section may be R, and preferably the vertical line may be setup to be superposed with the axis of the rotor shaft103. Taking the vertical line as axis, the airfoil blade101may be twisted up with constant speed around the vertical line. During twirling process, the angle of 90°±1°508formed by line segment L and chord between leading edge405and tailing edge406, and the distance L between the chord midpoint and the vertical line may be kept unchanged. The blade101can be formed after 120°510horizontal rotation. The vertical twirling height i.e. the vertical distance between the top most cross section and the bottom sectional circle of the blade may be as perFIG. 1,FIG. 2andFIG. 3, which may be longer than or equal to the length of rotor shaft.

With reference toFIG. 4,FIG. 6andFIG. 7the blade401,601,701of the VAWT with above-mentioned structure made as per above-mentioned method, and the wind rotor connected to the VAWT blade with the adoption of above-mentioned structure, the blade401,601,701forms a twisted structure from bottom to top along the vertical axle direction. The windage of blade may produce oblique torque when wind comes from various directions, therefore, the wind rotor can be started up and twirled automatically with low wind speed.

The above-mentioned is only the preferred embodiment of the present invention, however, since this present invention may be structurally modified in various forms by those skilled in the art, while its utilities remained unchanged, the extent of protection of the present invention may be subject to the protection domain stipulated by Claims.