WO2011158256A2 - Self governing pitch control mechanism in vertical axis wind turbine - Google Patents

Self governing pitch control mechanism in vertical axis wind turbine Download PDF

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Publication number
WO2011158256A2
WO2011158256A2 PCT/IN2011/000400 IN2011000400W WO2011158256A2 WO 2011158256 A2 WO2011158256 A2 WO 2011158256A2 IN 2011000400 W IN2011000400 W IN 2011000400W WO 2011158256 A2 WO2011158256 A2 WO 2011158256A2
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WO
WIPO (PCT)
Prior art keywords
airfoil blades
rotational speed
speed
spring
vertical axis
Prior art date
Application number
PCT/IN2011/000400
Other languages
French (fr)
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WO2011158256A8 (en
WO2011158256A3 (en
Inventor
V. R. Raghunathan
Original Assignee
Raghunathan V R
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Filing date
Publication date
Application filed by Raghunathan V R filed Critical Raghunathan V R
Publication of WO2011158256A2 publication Critical patent/WO2011158256A2/en
Publication of WO2011158256A3 publication Critical patent/WO2011158256A3/en
Publication of WO2011158256A8 publication Critical patent/WO2011158256A8/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F03D3/061—Rotors characterised by their aerodynamic shape, e.g. aerofoil profiles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F03D3/062—Rotors characterised by their construction elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/06—Controlling wind motors  the wind motors having rotation axis substantially perpendicular to the air flow entering the rotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/21—Rotors for wind turbines
    • F05B2240/211—Rotors for wind turbines with vertical axis
    • F05B2240/214—Rotors for wind turbines with vertical axis of the Musgrove or "H"-type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/70—Adjusting of angle of incidence or attack of rotating blades
    • F05B2260/72—Adjusting of angle of incidence or attack of rotating blades by turning around an axis parallel to the rotor centre line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/70—Adjusting of angle of incidence or attack of rotating blades
    • F05B2260/77—Adjusting of angle of incidence or attack of rotating blades the adjusting mechanism driven or triggered by centrifugal forces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/327—Rotor or generator speeds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/74—Wind turbines with rotation axis perpendicular to the wind direction

Definitions

  • This invention relates to wind turbines and more particularly to a vertical axis high speed wind turbine in which the mechanical means of spring based governor is used for the control of the rotational speed over its entire operational mode, i.e., the starting, normal operation and braking.
  • the rotational speed of the turbine should fall within the scope of design and has to be regulated in order to avoid the runaway condition and to ensure the safety of the system.
  • the spring governors serve the purpose of maintaining the speed within the operating speed thereby ensuring the desired output.
  • the propeller wind turbine (horizontal axis wind turbine) is required to have the propeller rotating disk always rightly aligned with the wind direction, whereas the vertical axis wind turbine is omni-directional, is not influenced at all by the wind direction and is better in respect of the configuration and operation.
  • the present inventors have developed and suggested a vertical axis high speed wind turbine using airfoil blades of an efficient airfoil and electromechanical means for the control of rotational speed and to maintain the constant frequency from the generator.
  • the turbine apparatus consists of three fixed flat airfoil blades, mounted vertically between two flat horizontal discs. The airfoil blades are bent at both ends, at precise angles and different locations from their respective ends. There are three movable control airfoil blades which are mounted 15 degrees behind the fixed airfoil blades in a clockwise rotation. The movable or adjustable airfoil blades are controlled by vertical shafts which can be adjusted to various positions while the turbine is in operation. Adjusting the movable airfoil blades affects the pressure and velocity within the turbine, causing changes in the turbine's speed.
  • the fixed airfoil blades are positioned at 120 degree intervals in rotation from each other and 55 degrees off centre to the turbines pivot point.
  • the airfoil blades are all positioned so as to allow the wind constant flow through the turbine at all times, even when stopped.
  • the adjustable airfoil blades when in the working mode, will increase the wind velocity and at the same time direct the force towards the airfoil blades that are ahead in rotation and are moving put of the wind's direct force.
  • the adjustable airfoil blades cause a nozzle effect on the blind airfoil blades for up to an additional 90 degrees in the null area of rotation.
  • a worm gear device With links and arms turns the shafts supporting the adjustable airfoil blades from above the turbine. Power to operate this device is fed through carbon brushes and slip rings from below the turbine. Very low current is used to reduce wear on the slip rings and brushes.
  • the adjustable airfoil blades can be positioned to cause a perfect balance of wind pressure on both sides of the turbine, in order to bring the rotation to a complete stop. In the event of mechanism failure, the adjustable airfoil blades will act from centrifugal force to limit the turbine's speed.
  • the turbine is fitted with a centre hub that must be of a specific dimension in order to form a nozzle area in combination with the two airfoil blades.
  • Two sealed ball bearings are fitted in the hub, one each at the top and bottom.
  • the complete assembly is then mounted on a hollow axle which extends below the turbine and slip rings into an adapter bracket.
  • the complete assembly is mounted on a suitable tower.
  • the drive is taken from the top of the turbine via a drive flange and drive shaft.
  • the drive flange is bolted through the upper disc and into the centre hub.
  • the drive shaft is keyed to the drive flange and extends down through the hollow axle to the load below the turbine.
  • a centering bearing is fitted in the bottom of the support bracket, in order to keep the drive shaft in alignment with the load. In areas where the wind direction is constant within 30 degrees this turbine can be mounted horizontally, on the crest of a beach or hill where the wind speed is usually higher.
  • the Japanese document JP2007-255788 describes a wind turbine device comprising a rotating shaft provided so as to have a vertical axis, a plurality of supporting arms fixed to the rotating shaft, a plurality of supporting shaft supported by the supporting shafts and provided at an equal distance in parallel with the rotating shafts, and a plurality of airfoil blades fixed to each supporting shaft and provided so as to rotate about the supporting shafts.
  • the airfoil blades circumferentially move integrally with the rotating shaft by receiving wind.
  • a guiding mechanism guiding an end portion on the rotating shaft side of each blade so as to pass on a circular orbit about an eccentric shaft which is eccentric from the rotating shaft in an orthogonal direction to the wind direction is provided for improving energy converting efficiency, and for automatically preventing the breakage of a wind turbine at strong wind without external power, by suppressing rotations.
  • the vertical axis wind turbine comprises a mechanical means that controls the speed of the rotation of the airfoil blades irrespective of the wind speed and direction.
  • the spring govemors connected between the hub and the airfoil blades controls the rotational speed of the airfoil blades based on the centrifugal force corresponding to the rotational speed of the wind turbine.
  • the spring govemors control the amount of wind incident on the airfoil blades by varying the angle of attack thereby retarding the speed gradually and bringing it within the operating speed of electric generator.
  • VAWT vertical axis wind turbine
  • VAWT vertical axis wind turbine
  • VAWT vertical axis wind turbine
  • a vertical axis wind power generation system with self governing pitch control mechanism comprising
  • Airfoil blades(1) that transmits the wind energy into rotary motion
  • Spring governor (4) connected diagonally between hub and the airfoil blades for controlling the rotational speed of the system.
  • the nacelle(6) for housing the rotor, gearbox, generator, anemometer, main shaft and other accessories
  • the method for controlling the rotational speed of the wind turbine by mechanical means of spring governor comprises of:
  • Airfoil blades are rotated by the approaching wind and they reach the determined rotational speed meanwhile Power is generated simultaneously from the turbine.
  • Fig.1 illustrates a vertical axis wind turbine (VAWT) with mechanical means for controlling the speed of the rotor airfoil blades irrespective of the wind speed and direction.
  • VAWT vertical axis wind turbine
  • Fig.2 illustrates a cross sectional view showing the spring governor connected diagonally between the hub and the airfoil blades.
  • Fig.3 illustrates a cross sectional view showing the hinge portion at the airfoil blades about which the arm is connected by means of c-clamp.
  • Fig.4 illustrates a block diagram showing the steps involved the controlling the rotational speed of the airfoil blades by mechanical means.
  • the present invention relates to a novel wind turbine and its speed regulation by means of self governor (4).
  • rotational speed is regulated by the spring governor (4) connected between airfoil blades (1) and the hub (5) of the assembly.
  • the speed is regulated by varying the angle of attack of the airfoil blades (1) thereby retarding the rotational speed of the airfoil blades (1) and preventing the above said runaway condition.
  • Fig.1 illustrates a front view of vertical axis wind turbine with mechanical means for controlling the rotational speed of the airfoil blades.
  • the objective of the wind turbine lies in generating power by harnessing the wind energy.
  • the wind incident on the airfoil blades rotates it thereby power is generated from the system.
  • the rotational speed of the system has to be regulated in such a way that the entire system is under control to prevent the runaway condition and ensure safety of the system.
  • the present invention utilizes spring governors (4) with its one end connected to the hub (5) and the other end connected to the airfoil blades (1).
  • the spring governors (4) are preloaded with determined tension corresponding to the desired or maximum rotational speed of the system.
  • the spring governors (4) are calibrated for the determined stiffness corresponding to the centrifugal force of the maximum or desired rotational speed.
  • the preloaded spring governors (4) hold the airfoil blades (1) firmly in position as long as the rotational speed falls with tin the desired range thereby generating the desired and continuous output from the system.
  • Fig.2 illustrates a cross sectional view showing the spring governors (4) connected between hub (5) and the airfoil blades (1).
  • the spring governors (4) are connected diagonally at the trail edge of the airfoil blades (1) from the hub (5) of the assembly.
  • Fig.3 illustrates a cross sectional view of preferred embodiment showing the hinge (8) portion at the airfoil blades (1) about which the arms (2) are connected.
  • the airfoil blades have slots at predetermined locations to accommodate the hinge (8).
  • the arm (2) has a clamp integrated with it at the end which seats exactly in the hinge (8) portion of the airfoil blades.
  • the arms(2) are fastened to the hinge(8) by means of c-clamp(7) so that the airfoil blades(1) are rigidly fixed at the speed below the operating speed and it can turn or rotate about the hinge(8) by means of spring governor(4) in case of rotational speed exceeding the desired or operating speed.
  • Fig.4 is a block diagram showing the steps involved in generation of power from the rotation of airfoil blades (1) by the incident wind at normal rotational speed. At speed higher than determined value the corresponding centrifugal force exceeds the stiffness of the spring governor (4) thereby airfoil blades (1) are turned by a certain degree.
  • the angle of attack is the predominant factor for the rotational speed and it is dependent on the position of the airfoil blades (1) incident to the wind. By turning the blade the angle of attack is changed thereby bringing the rotational speed to the desired level.

Abstract

According to an aspect of the present invention, there is provided an apparatus and method for controlling the rotational speed of the vertical axis wind power generation system without the requirement of the mechanical brake mechanism in order to prevent the runaway condition. The vertical axis wind turbine comprises a mechanical means of spring governor preloaded with determined tension corresponding to the optimum rotational speed. The spring holds the airfoil blades firmly as long as the rotational speed falls within the determined level. The spring acts as actuator while the rotational speed crosses the optimum level by tuming the blade to a certain degree thereby varying the angle of attack of the airfoil blades. The rotational speed is then retarded and regulated within the prescribed level.

Description

Title of the Invention
SELF GOVERNING PITCH CONTROL MECHANISM IN VERTICAL AXIS WIND TURBINE
Field of the Invention
This invention relates to wind turbines and more particularly to a vertical axis high speed wind turbine in which the mechanical means of spring based governor is used for the control of the rotational speed over its entire operational mode, i.e., the starting, normal operation and braking. In the existing system, the rotational speed of the turbine should fall within the scope of design and has to be regulated in order to avoid the runaway condition and to ensure the safety of the system. The spring governors serve the purpose of maintaining the speed within the operating speed thereby ensuring the desired output.
Background and prior art of the Invention
Generally, various wind turbines converting wind energy to a rotary motion have been already suggested and practiced. Among them, the propeller wind turbine (horizontal axis wind turbine) is required to have the propeller rotating disk always rightly aligned with the wind direction, whereas the vertical axis wind turbine is omni-directional, is not influenced at all by the wind direction and is better in respect of the configuration and operation.
Therefore, the present inventors have developed and suggested a vertical axis high speed wind turbine using airfoil blades of an efficient airfoil and electromechanical means for the control of rotational speed and to maintain the constant frequency from the generator.
Whereas the patent document CA 2158491 describes a vertical axis wind turbine apparatus, for converting the kinetic energy of the wind into usable force in a rotary manner as to turn a mill or drive a generator suitable for the home or business. The turbine apparatus consists of three fixed flat airfoil blades, mounted vertically between two flat horizontal discs. The airfoil blades are bent at both ends, at precise angles and different locations from their respective ends. There are three movable control airfoil blades which are mounted 15 degrees behind the fixed airfoil blades in a clockwise rotation. The movable or adjustable airfoil blades are controlled by vertical shafts which can be adjusted to various positions while the turbine is in operation. Adjusting the movable airfoil blades affects the pressure and velocity within the turbine, causing changes in the turbine's speed.
The fixed airfoil blades are positioned at 120 degree intervals in rotation from each other and 55 degrees off centre to the turbines pivot point. The airfoil blades are all positioned so as to allow the wind constant flow through the turbine at all times, even when stopped. The adjustable airfoil blades, when in the working mode, will increase the wind velocity and at the same time direct the force towards the airfoil blades that are ahead in rotation and are moving put of the wind's direct force. The adjustable airfoil blades cause a nozzle effect on the blind airfoil blades for up to an additional 90 degrees in the null area of rotation. From that point there is some negative or reverse effect, but only on the fixed airfoil blades since at that point the adjustable airfoil blades are shielded. Because the area of wind contact on the rear of the fixed airfoil blades is 20% of the area in contact with the wind on the front or positive side of the airfoil blades, the negative effect is overwhelmed and the turbine keeps on turning.
To control the adjustable airfoil blades, a worm gear device with links and arms turns the shafts supporting the adjustable airfoil blades from above the turbine. Power to operate this device is fed through carbon brushes and slip rings from below the turbine. Very low current is used to reduce wear on the slip rings and brushes. The adjustable airfoil blades can be positioned to cause a perfect balance of wind pressure on both sides of the turbine, in order to bring the rotation to a complete stop. In the event of mechanism failure, the adjustable airfoil blades will act from centrifugal force to limit the turbine's speed. The turbine is fitted with a centre hub that must be of a specific dimension in order to form a nozzle area in combination with the two airfoil blades. Two sealed ball bearings are fitted in the hub, one each at the top and bottom. The complete assembly is then mounted on a hollow axle which extends below the turbine and slip rings into an adapter bracket. The complete assembly is mounted on a suitable tower. The drive is taken from the top of the turbine via a drive flange and drive shaft. The drive flange is bolted through the upper disc and into the centre hub. The drive shaft is keyed to the drive flange and extends down through the hollow axle to the load below the turbine. A centering bearing is fitted in the bottom of the support bracket, in order to keep the drive shaft in alignment with the load. In areas where the wind direction is constant within 30 degrees this turbine can be mounted horizontally, on the crest of a beach or hill where the wind speed is usually higher.
The Japanese document JP2007-255788 describes a wind turbine device comprising a rotating shaft provided so as to have a vertical axis, a plurality of supporting arms fixed to the rotating shaft, a plurality of supporting shaft supported by the supporting shafts and provided at an equal distance in parallel with the rotating shafts, and a plurality of airfoil blades fixed to each supporting shaft and provided so as to rotate about the supporting shafts. The airfoil blades circumferentially move integrally with the rotating shaft by receiving wind. A guiding mechanism guiding an end portion on the rotating shaft side of each blade so as to pass on a circular orbit about an eccentric shaft which is eccentric from the rotating shaft in an orthogonal direction to the wind direction is provided for improving energy converting efficiency, and for automatically preventing the breakage of a wind turbine at strong wind without external power, by suppressing rotations.
But none of the prior art documents disclose a vertical axis wind turbine comprising mechanical means of spring governor for the self regulation and control of the rotational speed of the airfoil blades irrespective of the wind energy.
Summary of the Invention
According to an aspect of the present invention, there is provided a system for controlling the rotational speed of the vertical axis wind power generation system without the requirement of the electromechanical and control mechanism. The vertical axis wind turbine comprises a mechanical means that controls the speed of the rotation of the airfoil blades irrespective of the wind speed and direction. The spring govemors connected between the hub and the airfoil blades controls the rotational speed of the airfoil blades based on the centrifugal force corresponding to the rotational speed of the wind turbine. The spring govemors control the amount of wind incident on the airfoil blades by varying the angle of attack thereby retarding the speed gradually and bringing it within the operating speed of electric generator.
Object of the Invention
It is an object of the invention to convert the natural resource of wind energy to consumable electrical energy by the proposed new turbine vertical axis wind turbine.
It is another object of the invention to provide a vertical axis wind turbine (VAWT) with mechanical means for the control of rotational speed of the airfoil blades and to act as a brake and speed control mechanism.
It is another object of the invention to provide a vertical axis wind turbine (VAWT) with constant rpm of the airfoil blades and to generate a fixed frequency from the generator irrespective of the wind speed and direction.
It is another object of the present invention to provide a vertical axis wind turbine (VAWT) with pitch control on the airfoil blades to control the rotational speed.
Statement of the Invention
A vertical axis wind power generation system with self governing pitch control mechanism comprising
A. Airfoil blades(1) that transmits the wind energy into rotary motion
B. Arm (2) for connecting the airfoil blades to the hub of the vertical axis wind turbine.
C. Spring governor (4) connected diagonally between hub and the airfoil blades for controlling the rotational speed of the system. D. Hinge (8) connecting the arm and the airfoil blades about which the airfoil blades rotates or turns.
E. The nacelle(6) for housing the rotor, gearbox, generator, anemometer, main shaft and other accessories
The method for controlling the rotational speed of the wind turbine by mechanical means of spring governor comprises of:
A. Airfoil blades are rotated by the approaching wind and they reach the determined rotational speed meanwhile Power is generated simultaneously from the turbine.
B. Spring governors hold the airfoil blades firmly as long as the rotational speed is within the operating speed.
C. When rotational speed crosses the optimum level, Centrifugal force on the airfoil blades exceeds the tension of the spring governor.
D. The airfoil blades are turned by a certain degree by the centrifugal force since it
overcomes the tension of the spring governor.
E. Angle of attack is changed by the rotation of airfoil blades.
F. Variation in pitch angle retards the rotational speed of the turbine.
G. Speed is regulated and brought within the operating speed.
Brief Description of the Drawings
Fig.1 illustrates a vertical axis wind turbine (VAWT) with mechanical means for controlling the speed of the rotor airfoil blades irrespective of the wind speed and direction.
Fig.2 illustrates a cross sectional view showing the spring governor connected diagonally between the hub and the airfoil blades.
Fig.3 illustrates a cross sectional view showing the hinge portion at the airfoil blades about which the arm is connected by means of c-clamp. Fig.4 illustrates a block diagram showing the steps involved the controlling the rotational speed of the airfoil blades by mechanical means.
Detailed Description of the Drawings
In case of wind turbine the rotational speed of the airfoil blades should fall within the operating speed to prevent the runaway condition for generating the desired output.
Runaway condition:
When the grid connection is lost, there is no back electromechanical force at the generator and the generator will run at no load condition. The energy received from wind during the course of time will cause the rotor to pick up more rotational speed. The increased rotational speed in turn will increase the energy captured from the wind. There is an upward spiral action that cumulatively increases the rotational speed to go beyond the rated speed over the time. If this condition is not stopped, this eventually will lead to catastrophic failure of rotor system.
The present invention relates to a novel wind turbine and its speed regulation by means of self governor (4). In this present invention, rotational speed is regulated by the spring governor (4) connected between airfoil blades (1) and the hub (5) of the assembly. The speed is regulated by varying the angle of attack of the airfoil blades (1) thereby retarding the rotational speed of the airfoil blades (1) and preventing the above said runaway condition.
Fig.1 illustrates a front view of vertical axis wind turbine with mechanical means for controlling the rotational speed of the airfoil blades. The objective of the wind turbine lies in generating power by harnessing the wind energy. The wind incident on the airfoil blades rotates it thereby power is generated from the system. But for achieving the steady and desired output from the turbine, the rotational speed of the system has to be regulated in such a way that the entire system is under control to prevent the runaway condition and ensure safety of the system. The present invention utilizes spring governors (4) with its one end connected to the hub (5) and the other end connected to the airfoil blades (1). The spring governors (4) are preloaded with determined tension corresponding to the desired or maximum rotational speed of the system. When the airfoil blade rotates, the centrifugal force that develops should fall within the desired range corresponding to the tension of the spring governors (4). The spring governors (4) are calibrated for the determined stiffness corresponding to the centrifugal force of the maximum or desired rotational speed. The preloaded spring governors (4) hold the airfoil blades (1) firmly in position as long as the rotational speed falls with tin the desired range thereby generating the desired and continuous output from the system.
When the wind incident on the airfoil blades (1) rotates it at the speed above the operating speed, the airfoil blades (1) rotate at higher speed and the centrifugal force developed is higher than the prescribed range. Since the spring
governor (4) is designed for the stiffness corresponding to the determined rotational speed, it will lose its tension at the speed above the operating speed which will cause the airfoil blades (1) to turn by a certain degree. The angle of attack is changed by the turning of the airfoil blades (1) which retards the rotational speed of the airfoil blades (1) and the spring governor (4) regains its stiffness as the centrifugal force is reduced correspondingly to the rotational speed.
Fig.2 illustrates a cross sectional view showing the spring governors (4) connected between hub (5) and the airfoil blades (1). The spring governors (4) are connected diagonally at the trail edge of the airfoil blades (1) from the hub (5) of the assembly. When the rotational speed goes beyond operating speed the corresponding centrifugal force on the airfoil blades(1) exceeds the preloaded tension of spring governors(4) which makes them to lose their tension causing the airfoil blades(1) turn about its trail edge thereby changing the angle of attack which reduces the rotational speed to operating speed.
Fig.3 illustrates a cross sectional view of preferred embodiment showing the hinge (8) portion at the airfoil blades (1) about which the arms (2) are connected. The airfoil blades have slots at predetermined locations to accommodate the hinge (8). The arm (2) has a clamp integrated with it at the end which seats exactly in the hinge (8) portion of the airfoil blades. The arms(2) are fastened to the hinge(8) by means of c-clamp(7) so that the airfoil blades(1) are rigidly fixed at the speed below the operating speed and it can turn or rotate about the hinge(8) by means of spring governor(4) in case of rotational speed exceeding the desired or operating speed.
Fig.4 is a block diagram showing the steps involved in generation of power from the rotation of airfoil blades (1) by the incident wind at normal rotational speed. At speed higher than determined value the corresponding centrifugal force exceeds the stiffness of the spring governor (4) thereby airfoil blades (1) are turned by a certain degree. The angle of attack is the predominant factor for the rotational speed and it is dependent on the position of the airfoil blades (1) incident to the wind. By turning the blade the angle of attack is changed thereby bringing the rotational speed to the desired level.
It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not restricted to the above examples but may vary within the scope of the claims.
Further the above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

Claims
Claim 1
The system for controlling the rotational speed of the wind turbine by mechanical means of spring governor comprises of:
A. Airfoil blades(1 ) that transmits the wind energy into rotary motion
B. Arm (2) for connecting the airfoil blades operably to the hub of the vertical axis wind turbine.
C. Spring govemor (4) mounted between hub and the airfoil blades for controlling the rotational speed of the system.
D. Hinge (8) connecting the arm and the airfoil blades about which the airfoil blades rotates or turns.
E. The nacelle(6) for housing the rotor, gearbox, generator, anemometer, main shaft and other accessories
Claim 2
The system as claimed in claim 1 wherein the airfoil blades(1) are connected operably to the system by means of arm(2).
Claim 3:
The system as claimed in claim 1 wherein the arms (2) are attached to the hub (5) for transmitting the torque to the airfoil blades.
Claim 4:
The system as claimed in claim 1 wherein the mechanical spring governor (4) is connected between hub (5) and the airfoil blades (1).
Claim 5
The system as claimed in claim 1 wherein the nacelle (6) houses all the accessories for generating power from the rotation of the airfoil blades(1). Claim 6
The system as claimed in claim 3 wherein the mechanical spring governor (4) firmly holds the airfoil blades (1) until the system operates within the rated or operating speed.
Claim 7
The system as claimed in claim 3 wherein the mechanical spring governor (4) is preloaded with determined value of tension corresponding to the centrifugal force of optimum rotational speed.
Claim 8
The system as claimed in claim 1 wherein the centrifugal force exceeds the tension of loaded spring governor (4) while the rotational speed exceeds the optimum or operating speed.
Claim 9
The system as claimed in claim 1 wherein the airfoil blades (1) are turned by a certain degree at rotational speed above the optimum speed.
Claim 10
The system as claimed in claim 1 wherein the angle of attack of the airfoil blades(1) is changed by turning of airfoil blades(1) which retards the speed gradually.
Claim 11
A method of controlling the rotational speed of the vertical axis wind turbine by mechanical means of spring governor as claimed in claim 7 comprises of:
A. Airfoil blades (1) are rotated by the approaching wind and they reach the determined rotational speed meanwhile Power is generated simultaneously from the turbine.
B. Spring governors (4) hold the airfoil blades firmly as the rotational speed is within the operating speed.
C. When rotational speed crosses the optimum level, Centrifugal force on the airfoil
blades exceeds the tension of the spring governor (4). D. The airfoil blades (1) are turned by a certain degree by the centrifugal force since it overcomes the tension of the spring governor (4).
E. Angle of attack is changed by the rotation of airfoil blades (1 ).
F. Variation in pitch angle retards the rotational speed of the turbine.
G. Speed is regulated and brought within the operating speed.
Claim 12
The vertical axis wind turbine with pitch control as claimed in claim 7 for speed regulation and method substantially as herein described with respect to the accompanying drawings.
PCT/IN2011/000400 2010-06-17 2011-06-14 Self governing pitch control mechanism in vertical axis wind turbine WO2011158256A2 (en)

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IN1685/CHE/2010 2010-06-17

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FR2985291A1 (en) * 2011-12-30 2013-07-05 Marc Bois Torque limiter device for e.g. Darrieus type vertical axis wind turbine, for e.g. production of electricity, has return element provided for each blade to authorize pivoting of blade due to wind action to cause stalling and return blade
CN103742371A (en) * 2014-01-22 2014-04-23 深圳市宝联风光热能源科技有限公司 Vertical-axis wind turbine generator system with multi-layer wings and double swing vanes
CN103742370A (en) * 2014-01-22 2014-04-23 深圳市宝联风光热能源科技有限公司 Rising swing blade type vertical-shaft wind generating set

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Publication number Priority date Publication date Assignee Title
FR2985291A1 (en) * 2011-12-30 2013-07-05 Marc Bois Torque limiter device for e.g. Darrieus type vertical axis wind turbine, for e.g. production of electricity, has return element provided for each blade to authorize pivoting of blade due to wind action to cause stalling and return blade
CN103742371A (en) * 2014-01-22 2014-04-23 深圳市宝联风光热能源科技有限公司 Vertical-axis wind turbine generator system with multi-layer wings and double swing vanes
CN103742370A (en) * 2014-01-22 2014-04-23 深圳市宝联风光热能源科技有限公司 Rising swing blade type vertical-shaft wind generating set
CN103742371B (en) * 2014-01-22 2016-05-04 深圳市宝联风光热能源科技有限公司 A kind of multilayer spademan double pendulum blade vertical-shaft wind power generating set
CN103742370B (en) * 2014-01-22 2016-05-11 深圳市宝联风光热能源科技有限公司 A kind of spademan swing blade type vertical axis aerogenerator group

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