IE50692B1 - Windmill speed regulatory and overload cutout device - Google Patents

Abstract

The device comprises a baffle 25 pivotally mounted on housing 12 to face broadside into the wind, adapted for movement between an upwind and a downwind position, and biased by a counterweight into the upwind position. Means, including axially movable rod 30, responsive to the baffle position are provided for altering the pitch of the blades 13 to deploy the blades fully in the upward position of the baffle, feather them fully in the downwind shut-down position thereof, and partly feather them at intermediate baffle positions according to the wind velocity.

Description

This invention relates to the generation of electrical energy from wind power. In particular it relates to a windmill of the type which comprises a fixed support, a weathervane-guided housing mounted on the support for rotation about a vertical axis, a horizontally disposed windmill rotor mounted in the housing, and at least two elongated aerofoils each pivotally mounted on the rotor to permit feathering, hereinafter referred to as a windmill of the type described. Such windmills normally incorporate an electrical generator in the housing, the shaft of which generator is an extension of the windmill rotor.

In windmills of the type described, it has not been possible to design a shape of fixed-pitch aerofoil which will stand up in use to wind speeds above about 100 Km/h without mechanical failure, so long as the size and output of the mill are of domestic magnitude e.g. 8 KVA for a swept area of 35 to 40 square meters. Thus it is known to adapt the aerofoils for feathering, so that the power output can be rendered more nearly constant by adjusting the aerofoil pitch to compensate for variations in wind velocity, including adjusting to a predetermined shut-down pitch for use when the wind velocity exceeds a given maximum. Such adjustment has normally been carried out manually, in response to the readings of airspeed indicators or personal observation, or alternatively by means of expensive electronic transducer arrangements.

The invention seeks to control the rotary speed and output of a windmill of the type described, and to provide automatic shut-down of the mill above a predetermined wind velocity, by means of an inexpensive automatic device sensitive to a selected range of wind velocities.

The invention accordingly provides a speed regulatory and overload cut-out device for a windmill of the type described, which comprises - 3 a baffle mounted on the housing to face substantially broadside into the wind and adapted for movement in the wind direction between an upwind and a downwind position, biasing means to urge the baffle into the upwind position, means responsive to the baffle position for altering the pitch of the aerofoils between a fully deployed state corresponding to the upwind baffle position and a fully feathered state corresponding to the downwind baffle position, the biasing means being of a magnitude suitable to withstand a selected rated wind velocity, and to yield to velocities thereabove.

It will be understood that the fully feathered state of the aerofoil pitch corresponds to a shut down of the windmill.

The baffle is preferably fixed to one arm of a lever pivotally mounted on the housing. Preferably the resultant arcuate freedom of movement of the baffle extends to an angle not exceeding 90°, more preferably an angle not exceeding 60°, so that the baffle can remain disposed substantially broadside to the wind from its upwind to its downwind position without further provision for altering its angle of tilt.

The means for altering the pitch of the aerofoils in response to the position of the baffle preferably comprises a connecting rod slidably mounted on the housing for axial movement, one end of the rod being arranged for sliding actuation by the lever which carries the baffle, the other end of the rod being linked to a crank member on each aerofoil for altering the pitch thereof. To provide a strong, balanced construction it is preferred that the windmill rotor be tubular, and the connecting rod be mounted coaxially within said tubular rotor in bearings which permit the rotor to rotate freely around the connecting rod.

Since the lever which carries the baffle is pivotally mounted, but must move the connecting rod in a straight line, it is preferred that the lever carry a slidable housing or bearing for engaging said one end of the connecting rod. The slidable housing or bearing is desirably located in proximity to the pivotal mounting of the lever on the housing, so that the necessary sliding motion of the housing or bearing is of conveniently small magnitude. Thus the housing or bearing may move, for example, on short guide rails fixed to the lever and disposed in the direction of the length of said -lever.

The biasing means for the baffle is conveniently a counterweight carried on a transverse extension of the lever, either the magnitude of the weight or its location along said transverse extension being adjustable.

Preferably there are provided wans for manually overriding the biasing means to move the baffle into the unwind position and thus shut down the windmill by intentionally feathering the blades thereof to the fullest extent. Such overriding means may comprise for example a cable operated by a hand lever or winch mounted at a convenient height on the fixed support of the windmill.

The invention will be appreciated in greater detail from the following description of a particular and preferred embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which Fig. 1 is a side elevation, partly cutaway, of a windmill for electricity generation.

Fig. 2 is an enlarged perspective view of a baffle and biasing means as detached from the windmill of Fig. 1, Fig. 3 is a schematic enlargement of a detail of Fig. 1, and Fig. 4 is a schematic plan view of a detail from Fig. 1, taken along the line IV-IV in that figure and viewed in the direction of the associated arrows. - 5 Referring now to the drawings, a windmill 10 for electricity generation comprises a fixed support 11, a swivelling nacelle 12, a pair of aerofoils 13 pivotally mounted on the nacelle 12, a weathervane 14, a speed regulatory and overload cutout device 15, and a shutdown handle 16.

The support 11 is of tubular steel, groundmounted and supported by conventional stays (not shown).

The nacelle 12 is mounted on the support 11 by a bearing 17 for swivelling in a horizontal plane, as guided in use by the weathervane 14 in response to the wind direction. The operating wind direction is shown by an arrow W. The weathervane 14 is fixed on a support arm 18 which in turn is mounted on the nacelle 12 by conventional fastening means 19. The nacelle 12 also mounts an electrical generator 20 driven through appropriate gearing (not shown) by a hollow shaft 21 journalled in the generator the shaft 21 being secured at one of its ends perpendicularly to an aerofoil axle 22 upon each end of which a respective aerofoil 13 is pivotally and coaxially mounted for feathering.

Each aerofoil 13 has an inwardly facing end surface 23 from which a crank 24 projects, operation of the crank serving to feather or unfeather the aerofoil 13 by pivoting the aerofoil about the aerofoil axle 22.

The speed regulatory and overload cutout device 15 comprises a baffle 25 fixed to a framework 26 which is pivotally mounted about an axis 27 to the nacelle 12. The framework 26 includes a transverse member 28 which carries a counterweight 29, the position of the counterweight along the transverse member 28 being adjustable.

The device 15 further comprises a push rod 30 one end of which is retained and journalled in a hanger bearing 33, while the other end thereof carries a cross-member 31 connected to each of the cranks 24 by a respective lengthadjustable link 32. The push rod 30 lies within the hollow 602 - 6 core of the shaft 21 within which it is axially displaceable, guided by bronze bushings 35 housed within the hollow shaft 21. The hollow shaft 21 is grease filled, to ease the axial motion of the push rod 30 in use. The hanger bearing 33 has parallel lateral grooves and is slidably retained by cooperating guide rails 34 fixed to the framework 26, whereby in use the push rod 30 is restricted to co-axial motion with respect to the hollow shaft 21, although pushed and pulled in use by the framework 26, which being pivoted (at 27) travels in a circular arc.

The shutdown handle 16 is a lever pivoted to the support 11, and connected to the framework 26 by a cable 36. The handle 16 cooperates with a catch (not shown) on the support 11 to retain the framework 26, and consequently the entire device 15,in the shutdown condition wherein the aerofoils 13 are fully feathered as shown in dotted outline in Figs. 1 and 4.

In use of the windmill according to the invention, there are predetermined a rated windspeed V^, and a shutdown windspeed The counterweight 29 is positioned to balance the baffle 25 against the rated windspeed Vp whereby the framework 26 begins to pivot clockwise, as seen in Fig. 1, only at windspeeds in excess of V^. The pivotal attitude of the framework 26 at the shut-down windspeed Vj is then determined with the links 32 disconnected. This attitude is represented by the angle a in Fig. 1. With the aerofoils 13 held stationary and fully feathered the framework 15 is positioned in said pivotal attitude at the angle a, and the links 32 are then reconnected and length-adjusted to eliminate play.

The device 15 will subsequently operate to shut down the windmill by fully feathering the aerofoils 13 at all windspeeds in excess of V^, and will automatically redeploy the aerofoils to some extent every time the windspeed drops below Vj. Moreover the shutdown handle 16 may be operated at any - 7 time to override the counterweight 29 and shut the windmill down for repair or maintenance, or when power is not required therefrom.

A prototype wind-powered generator assembly in accordance with the invention was designed and built capable of giving 8 KVA in a 23 mph wind. In view of the variable output of wind-powered generators its most suitable application is for heating, this also being most appropriate in the present situation of oil shortages and rising prices for fuel of every kind. The basic aims of the designer were therefore to produce a machine capable of directly heating a dwelling house of average size having a reasonable site from the point of view of wind power. There are very few machines on the world market capable of doing this (perhaps 2 or 3) and at the moment they are very expensive to import. The applicant's previous experience of importing and erecting these known machines has indicated that many do not stand up to the extreme windspeeds sometimes experienced in Ireland, particularly on the west coast. The basic design adopted was therefore a simple welded steel fabrication using as many off-the-shelf components (standard A.C. generator, self-aligning bearings etc.) as possible to keep the costs down, in combination with a relatively large and aerodynamically efficient rotor to extract the utmost power from low windspeeds and also to make up for a slight loss of efficiency in using a standard generator.

The windmill of the invention provides for an immediate response to a sudden gust of wind thereby relieving the bending stresses on the blades. The generator is a standard three-phase A.C. machine giving a maximum output of 8.1 KVA at 1450 r.p.m.

Because of the use of as many standard industrial components as possible in conjunction with the very simple governing system it is expected that the complete machine including tower can be produced for approximately half the 692 - 8 cost of any comparable machine imported into Ireland. Reference to the yearly energy production curve would indicate a pay-back period of 3 - 5 years on a good site at the present cost of electricity from commercial sources.

Testing and development work is expected to concentrate on adjustment and development of the governing system, particularly on its speed of response to a sudden gust of wind and hence the resulting increase in stress on the whole rotor structure. Such work will not only check the stress analysis of this machine but will also provide the basis for structural analysis of larger machines in the future. Another important design aspect will be the provision of a control unit and load matching device for the generator and the matching of the whole machine to a heating installation so that a complete heating system for a dwelling house can be provided.

The following technical data refer to the prototype and are given by way of example.

Rotor Two bladed upwind of tower Diameter 25 feet Swept Area 490 Sq.ft. Rotational Speed (rated) 120 r.p.m. Tip Speed Ratio 5.3 Blade Chord - Root 1.66 ft. Blade Chord - Tip 1.00 ft. Aerofoil Section 4418 NACA Aerodynamic twist - root to tip 22° Mass balance degree about blade axis Position of blade feathering axis (S of mean 100% Aerodynamic chord of blade) 20% Cut-in Windspeed 8 m.p.h. Rated 22 m.p.h. Shut Down 60 m.p.h. Survival 120 m.p.h. - 9 50682 Generator Stamford D8C - rated 8.1 KVA at 1450 r.p.m.

Mechanical Configuration Welded steel chassis. Drive by timing belt via 5 lay shaft to generator; gear ratio 1:12. Sealed, self aligning bearing units. Tail vane of aerofoil section raised above nacelle. Tower of 9 steel tube. 1 set of 5 guy wires, pin jointed at base.

Governing Mechanism The geometry is so arranged as to give a fixed blade angle in windspeeds up to full rated output, constant r.p.m. from 22 m.p.h. to 35 m.p.h., thence a gradual shutdown till the blades are fully feathered at 60 m.p.h. The pivot axis of the blades is placed forward of the mean aerodynamic centre thereby ensuring an increasing twisting moment tending to feather the blades should they start to overspeed due to belt failure or generator no load condition.

Claims (14)

1. CLAIMS:1. A speed regulatory and overload cut-out device for a windmill of the type described, which comprises a baffle mounted on the housing to face substantially broadside into the wind and adapted for movement in the wind direction between an upwind and a downwind position, biasing means to urge the baffle into the upwind position, means responsive to the baffle position for altering the pitch of the aerofoils between a fully deployed state corresponding to the upwind baffle position and a fully feathered state corresponding to the downwind baffle position, the biasing means being of a magnitude suitable to withstand a selected rated wind velocity, and to yield to velocities thereabove.

2. A device according to claim 1 wherein the baffle is fixed to one arm of a lever pivotally mounted on the housing.

3. A device according to claim 2 wherein the resultant arcuate freedom of movement of the baffle extends to an angle not exceeding 90°.

4. A device according to claim 3 wherein the angle does not exceed 60°.

5. A device according to any of claims 2 to 4 wherein the means for altering the pitch of the aerofoils comprises a connecting rod slidably mounted on the housing for axial movement, one end of the rod being arranged for sliding actuation by the lever which carries the baffle, the other end of the rod being linked to a crank member on each aerofoil for altering the pitch thereof. - 11

6. A device according to claim 5 wherein the windmill rotor is tubular, and the connecting rod is mounted coaxially within said tubular rotor in bearings which permit the connecting rod to slide therein.

7. A device according to any of claims 2 to 6 wherein the lever carries a slidable housing or bearing for engaging said one end of the connecting rod.

8. A device according to claim 7 wherein the slidable 10 housing or bearing is located in proximity to the pivoted mounting of the lever on the housing.

9. A device according to claim 8 wherein the lever is provided with short guide rails disposed in the direction of the length of the lever, along which guide rails the 15 housing or bearing is adapted to move.

10. A device according to any of claims 2 to 9 wherein the biasing means for the baffle is a counterweight carried on a transverse extension of the lever.

11. A device according to claim 10 wherein the 20 magnitude of the counterweight is adjustable.

12. A device according to claim 10 wherein the counterweight is displaceable along the transverse extension.

13. A device according to any of claims 1 to 12 which comprises means for manually overriding the biasing means 25 to move the baffle into the upwind position and thus shut down the windmill by intentionally feathering the blades thereof to the fullest extent.

14. A device according to claim 1, substantially as herein described. 50893 - 12 Dated this the 9th day of April, 1981. F. R. KELLY & CO. BY: ./ EXECUTIVE. 27 Cilyde Road, ballsbridge/Dublin 4. AGENTS FOR THE APPLICANTS. ALTERNATIVE TECHNOLOGY LIMITED