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
  • F03D7/00—Controlling wind motors 
  • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
  • F03D7/022—Adjusting aerodynamic properties of the blades
  • F03D7/0224—Adjusting blade pitch
• • 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 
  • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
  • F03D7/022—Adjusting aerodynamic properties of the blades
• • 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 
  • F03D7/02—Controlling wind motors  the wind motors having rotation axis substantially parallel to the air flow entering the rotor
  • F03D7/04—Automatic control; Regulation
• • 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
• • 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
  • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

• the present application pertains to a novel means by which the blade pitch angle of a wind turbine can be automatically set for optimum power output in changing wind conditions.
• the present invention relates to a mechanism that can be employed by Horizontal Axis Wind Turbines (HAWT) to set the optimum blade pitch angle for the differing conditions they are likely to encounter in order to optimize their power yield.
• HAWT Horizontal Axis Wind Turbines
• a principal object of this invention is to provide a means to automatically set the blade pitch to a low TSR in order to deliver maximum torque at zero rotational speed for early turbine start up.
• a further object of this invention is to increase the TSR as the turbine accelerates and hold it stable at the ideal continuous running condition.
• a further object of this invention is to quickly react to gusts or transient increases in wind speed by reducing the TSR to increase the torque and hence rate of rotational acceleration.
• a further object of this invention is to quickly react to lulls or transient decreases in wind speed by increasing the TSR to reduce the torque and hence maintain rotational momentum.
• a further object of this invention is to react to excessive wind speed in order not to exceed the safe rpm limit by reducing the TSR in these conditions - akin to feathering the blades where they generate less drag.
• a further object of this invention is to provide for all of the above with a self powered and relatively simple mechanism that can be built at low cost.
• the invention proposes to utilize both the axial thrust on the rotor and the centripetal forces related to its rotational velocity to achieve an optimum solution for all conditions.
• the basic concept is that axial thrust pushes the turbine back along its shaft causing the pitch to be increased and TSR lowered, while rpm related centripetal force pulls the turbine forward causing the TSR to be increased.
• This overload spring acts between the centripetal forcing element and the turbine and thereby enables the turbine to move back in high winds irrespective of the amount of centripetal force being generated. It is set to a preload such that it begins to permit displacement after the known thrust generated at the rpm limit is exceeded and at a spring rate appropriate to maintain that limit as the TSR is proportionately reduced.
• a preferred embodiment Rather than utilize the blades to generate the balancing centripetal force, in a preferred embodiment separate masses are used.
• the advantage of decoupling the centripetal force from the blades is that blade forces could become excessively high and the increase in tip diameter as they move out radially could be a problem where the blades run in a confined duct as in a system where a diffuser is used to accelerate the wind through the turbine.
• Masses can be arranged to fly out axially, perhaps even surrounding the blade shaft, but a preferred embodiment is for them to swing up on arms much like what occurs with a speed governor.
• This action can be arranged to cause a roller on the mass lever to act against a cam whose profile presents a local ramp angle which gears the amount of axial balancing force generated to the optimum for any given rpm.
• the scheme requires that the blade shaft is rotated in proportion to the axial displacement of the hub.
• a preferred means of achieving this is by employing two rollers attached to the fixed generator shaft acting on double sided cams attached to the blade shafts.
• the cam angle progression can again be selected to vary the gearing so the relationship need not be linear.
• the cams are obliged to rotate as the rollers are in a fixed position with respect to the generator shaft.
• a further embodiment uses a belt firstly attached to the fixed part of the hub, then wrapped around the blade axles attached to the axially displaceable part of the hub and then returned to the fixed part via a spring. As the blade set is displaced axially, the belts cause the blades to rotate on their shafts with the slack taken up by the spring or belt lengthened by the spring.
• the springs act as a preload device in not just maintaining belt tension, but also in trying to bull the belt in they move the blades set such that it increases their pitch angle and becomes more feathered as would be appropriate in a start up condition. In doing so it also holds the centripetal masses in their closed position.
• the balance point is reached at the point where the turbine torque has decreased with increasing TSR such that it can no longer accelerate. This is helped by the start up spring which provides its axial force in proportion to the axial turbine displacement that sets the TSR. As such, the balance point reached tends to increase it's TSR a little as the wind speed increases (and the spring has a relatively smaller forcing effect). This is helpful in providing more torque at lower speed to better match the characteristics of the attached generator.
• the centripetal forces are geared by a varying ramp angle on the CAM against which they act as previously explained.
• Fig. 1 shows a first data illustration
• Fig. 2 shows a second second data illustration
• Fig. 3 shows a force balance relationship
• Fig. 4 shows a tip speed ratio relationship
• Fig. 5 Shows two isometric views of the mechanism. The left hand view shows it in start up condition where the blades are set to provide maximum torque. The right hand view shows it in maximum rpm condition where the weights have swung out, pulling the hub forward and setting the blades suitable for a high TSR.
• Fig. 6 Shows two top views with the upper blade system sectioned through its driving CAM.
• the left hand view shows it in start up condition with the blade CAM at its backwards limit and where it's offset between the CAM rollers has caused it to rotate to its clockwise limit.
• the right hand view shows the hub pulled forward, moving the CAM to its anti-clockwise limit.
• Fig. 7 Shows a side view section through the centre of the mechanism, shown in its start up condition.
• Fig. 8 Shows a similar side view section, but with the mechanism at its maximum rpm condition.
• Fig. 9 Shows a similar side view section, but in its overload condition where the overload springs have compressed and allowed the hub to move back despite the high centripetal force opposing it.
• Fig. lO Shows the embodiment where a belt is used to rotate the blades axles. In this view the belts have been pulled back by their springs causing the blades to move to a high pitch feathered position.
• Fig. 11 Shows the same embodiment as Fig. 10 but now in a running mode at a higher rpm where the centripetal masses have swung out and pulled the blade set forward, thereby stretching the springs that hold the belts and consequently causing the belts to rotate the blade's axles.
• the mechanism is show with its frame (1 ) comprising two profile cut sheets with lengths of tubing welded in a radial pattern to support the blade axes.
• This embodiment supports five blades, but it can be seem that other numbers are possible.
• the hub is pushed to the back of its shaft by the spring (2), holding in the centripetal masses (3) that swing on arms to drive the roller (4) against the CAM (5) to progressively displace the hub forward as the weights swing out as shown by (12).
• CAM roller supports (10) retain rollers (6) which act on the blade setting CAMs (7). It can be seen that the blades (8) rotate on their axes into position (11 ) as the weights force the hub forwards.
• the sectioned mechanism in the left hand view shows the back flange (14) that supports the CAM roller retainers (19) with their rollers (20) and (22) acting on the CAM (17) to set its degree of rotation about the blade axis.
• the roller (23) acts against the narrow wedge plate (24) and transmits the drive torque from the frame (13) to the flange (14).
• This device enables it to be adjusted to a degree of bearing preload in the rollers consistent with stiff control.
• the masses (15) are in their park position.
• the sectioned view shows the flange (28) rigidly connected to the generator shaft and the shaft extension.
• the CAM roller retainers (32) holding the rollers e.g. (34) against the CAM (38).
• the frame (30) includes a bore that permits it to slide along the shaft as required to achieve the force balance axial offset position.
• the frame is held up tight against a further stepped tube (29) by high force springs (33) riding on a radial array of shafts with end stops (31) trapping one of the frame's profiled plates between it and the springs. As will be seen this constitutes the overload preload device.
• the weight is show fully retracted by the action of the spring (37) displacing the CAM (36) and frame (29 & 30) as far back as possible causing the roller (35) to rise to its top position.
• the sectioned view now shows the mechanism in its maximum forward position where the roller (46) in swinging upwards has pulled the CAM (48) forward, dragging the stepped tube (45) and frame (39) with it - as may be found at the rpm limit.
• the start up preload spring (47) is now fully compressed.
• the blade rotation has been set for maximum rpm as the CAM (42) has been rotated by the action of the rollers e.g. (40) retained by the part (43) against the flange that is part of the shaft extension (44).
• FIG 11 The same embodiment as FIG 6 is shown, but now the blade set (58) has been forced forward by the centripetal masses (56) swinging out on their lever arms as a result of the hub's rotation.
• the springs e.g. (52) have now been stretched effectively lengthening the belts e.g. (53) which rotate the pulleys e.g. (54) and consequently adjust the blade pitch angle in this case reducing it.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Wind Motors (AREA)

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• 2009
  • 2009-03-24 GB GB0904921A patent/GB2471060A/en not_active Withdrawn
• 2010
  • 2010-03-24 EP EP10711259A patent/EP2411667A2/en not_active Withdrawn
  • 2010-03-24 US US13/260,197 patent/US20120014794A1/en not_active Abandoned
  • 2010-03-24 WO PCT/GB2010/050500 patent/WO2010109238A2/en active Application Filing
  • 2010-03-24 CN CN2010800179702A patent/CN102439294A/zh active Pending

Non-Patent Citations (1)

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