GB2244099A

GB2244099A - Turbine assembly

Info

Publication number: GB2244099A
Application number: GB9010971A
Authority: GB
Inventors: John Eric Meanwell
Original assignee: PRINTER MARKETING Co LIMI
Current assignee: PRINTER MARKETING Co LIMI
Priority date: 1990-05-16
Filing date: 1990-05-16
Publication date: 1991-11-20
Anticipated expiration: 2010-05-16
Also published as: GB2244099B; GB9010971D0

Abstract

in a bladed rotor 10 for a wind or water turbine or a fan or propeller blades 12 extend generally parallel to, and are rotatable about, an axis 14, the angle of incidence of each blade 12 being controlled to vary with respect to the angular position of the blade about the axis 14. Each blade 12 has a pivotal mounting 16 adjacent its leading edge 18 and at a predetermined distance from the axis 14. A respective linkage 22 extends from a pivotal attachment 24, adjacent the trailing edge 20 of each blade 12, to a hub 26 offset from the axis 14. Rotation of the blades about the axis 14 generates a resultant fluid flow in a direction W determined by direction of offset of the hub 26 and of a magnitude determined by the separation of the axes of the hub 26 and turbine axes 14. Control mechanisms for positioning of the hub 26 are disclosed. Such a bladed rotor 10 when driven by fluid flow can have application in a wind or water powered turbine generator and, when driven mechanically, as a fan or marine propulsion unit. <IMAGE>

Description

TURBINE ASSEMBLY The present invention relates to turbines of the type having a number of blades arranged, in the form of a cage, about a central axis of rotation. Turbines of this type will hereinafter be referred to generically as cage turbines and the word "turbine" will be taken to refer to bladed rotors generally, whether driven by an incident fluid flow (such as windmills or waterwheels) or driven by other means to generate a fluid flow (such as fans or propellers).

In particular, the present invention relates to cage turbines in which the angle of incidence of each blade is adjustable.

The advantages of cage turbines over propeller-type turbines are well known. Since the whole length of a blade leading edge moves at the same speed in a cage turbine, the stresses consequent on the blades passage through a fluid are evenly distributed along the length of the blade. This means that a simple straight blade of constant cross-section may be used as opposed to the more complex and costly blade shapes required by propeller-type turbines.

Cage turbines do, however, have certain disadvantages. If the blades of a cage turbine are fixed, any two blades displaced by 1800 about the turbine axis will be acting in opposition to one another.

This may be overcome by partially shrouding the turbine or by directing fluid flow tangentially toward one side of the turbine: both of these methods, relying on the use of a blade for only a small part of its travel, result in reduced efficiency. A more suitable method is to flake the angle of incidence of each blade variable with respect to the angular displacement. In this way, a flat blade travelling in the direction of fluid flow may be given a large angle of incidence to maximize its effect while a blade travelling in the opposite direction may be feathered to minimise its counteracting effect. A blade traversing the direction of fluid flow may be angled to give a resultant effect in the desired direction.

One such cage turbine having a mechanism for varying the blade angle in this way is described in U.S. Patent No. 4260328 (Hamel) which shows a vertical windmill system in which each paddle-like blade, pivotally mounted on a support body, is provided with a cam follower arm. As the support body and blades rotate around a central axis, the cam follower moves over the surface of a specially shaped cam which causes the blades to move about their pivotal mounting. The Hazel system requires the use of spring loaded levers to keep the cam followers in contact with the cam surface which, in oombination with the cam surface design, make this a very complex assembly.

Another mechanism for varying the blade angle of a vertical windmill is shown in published German patent application No.2826180 (Roth). The blades are pivotably mounted on a first rotor, rotating about a first axis. A guide channel is rigidly attached to each blade, so as to pivot with the blade. A second rotor, eccentric to, and driven by, the first rotor carries guide bodies in the form of pegs positioned to be received by the guide channels attached to the blades. Due to the eccentricity of the rotors, as they rotate the peg will move back and forth within the confines of the channel causing the blade to pivot on its mounting. Like the Hamel system the Roth mechanism is a complex design requiring, amongst other things, a gearing mechanism to drive the second rotor from the first.

The complex construction of the Hamel and Roth systems is in part due to the ccniDlex pattern of blade motion achieved. With both systems, throughout rotation about the turbine axis, the leading edge of each blade is forward of the trailing edge when viewed from the direction of incident fluid flow. The effect of this is that, for that part of the rotation where the blade is moving generally in the direction of the fluid flow, the trailing edge of the blade is moving ahead of the leading edge. Whilst this will not adversely affect the operation of these systems as wind-driven turbines, where the fluid flow rate generally exceeds the tangential speed of the blade, problems may arise when the turbine is being driven to generate the fluid flow.In such a situation, the tangential speed of the blade exceeds the fluid flow speed and a resultant fluid flow from the trailing edge of the blade to the leading edge occurs, resulting in reduced efficiency of operation.

In accordance with the present invention there is provided a cage turbine rotatable about a turbine axis, in which each turbine blade is pivotably mounted and in which the angle of incidence of each turbine blade is controlled in dependence on the angular displacement of the blade about the turbine axis with the leading edge of each blade being angularly displaced about the turbine axis in the direction of turbine rotation relative to the trailing edge of the blade.

When the turbine assembly of present invention is being driven to generate a fluid flow, the flow across the surface of each blade will be from the leading edge to the trailing edge at all points around the turbine axis. The trailing edge of each turbine blade may be controlled to travel a substantially circular path having its centre offset from the turbine axis.

Also in accordance with the present invention there is provided a cage turbine, rotatable about a turbine axis, in which each turbine blade is pivotably mounted and in which the angle of incidence of each turbine blade is controlled in dependence on the angular displacement of the blade about the turbine axis by a linkage pivotally attached at one end to the blade and at the other end to a hub, the linkage being rotatable about the axis of the hub which is offset from the turbine axis.

The turbine blades are preferably of aerofoil cross-section.

The applicants have appreciated the fact that aerofoil section blades have maximum effect when traversing the direction of fluid flow and have utilised this to provide a turbine assembly in which the blades describe a mxe regular path geametry than the complex blade paths of the Darnel and Roth systems. A further advantage arising from the efficiency of aerofoil section blades is than, when the turbine of the present invention is driven by an incident fluid flow, the resultant tangential speed of blade will exceed the fluid flow speed thus avoiding problems arising from reverse fluid flow from the trailing edge to the leading edge of the blade.

The linkage causes each blade to pivot about its mounting as it moves around the turbine axis. In the case where the turbine is driving a fluid flow, the magnitude of the flow will be determined by the distance from the turbine axis to the hub and the resultant flow direction will be determined by the direction of offset of the hub in relation to the turbine axis. The mechanism of the present invention is thus a far less complex construction than the Hsmel and Roth systems described above and, unlike the Hamel and Roth systems, the turbine assembly is equally suited to both driving and driven operation.

The linkage from each blade may be connected to a oommon hub which may either be fixed relative to the turbine axis or movable relative thereto under control of a hub positioning mechanism. To relieve mechanical stresses, a hub and linkage system may be provided at each end of the turbine with the two hubs linked to move in unison.

Additional cages of turbine blades may be provided concentric with the present cage turbine. The turbine blades of such additional cages, ref erred to hereinafter as secondary blades, may be positioned radially outward of the blades of the present cage turbine, referred to hereinafter as prImary blades. The secondary blades are preferably controlled to remain substantially parallel to the adjacent primary blade, such that all blades along a given radius from the turbine axis have the same angle of incidence.

One particular preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1. schematically illustrates the variation in blade angle of incidence for a given hub offset; Figure 2 graphically represents the individual and total power output for a three bladed turbine driven by a fluid flow; Figure 3 shows a manually operated hub offset control mechanism; and Figure 4 shows a further manually operated hub offset control mechanism which may be used in place of that of Figure 3.

Referring initially to Figure 1, the cage turbine 10 comprises a number of generally elongate turbine blades 12 of syiwttrical aerofoil cross-section mounted for rotation about the turbine axis 14. Each blade 12 is pivotably mounted to allow rotation about a blade pivot axis 16 adjacent the leading edge 18 of the blade.

Adjacent the trailing edge 20 of the blade, one end of a linkage 22 is pivotably attached so as to be rotatable about a link pivot axis 24. The opposite end of the linkage 22 is pivotally attached to a hub 26 positioned with its axis substantially parallel to the turbine axis and at a predetermined distance T from, and angular position about, the turbine axis 14.

Where the turbine is driving a fluid flow, the resultant flow will be in the direction W of offset of the hub axis. Where the turbine assembly is driven by an incident fluid flow, the turbine will be most efficient (in terms of the power generated) when oriented such that the incident fluid flow is in direction W with respect to the turbine and hub axes.

All of the linkages 22 are of the same length and the distance from blade pivot axis 16 to turbine axis 14 is equal to the distance from link pivot axis 24 to the axis of the hub 26. The pivot axes 16, 24 of the blade thus travel circular paths of equal radius, in a direction of rotation R, although with centres offset by a distance T.

In operation, a blade at position A is substantially parallel to the line between the turbine axis 14 and the axis of the hub 26.

As the blade moves to position C, via B, the outer surface of the blade generates lift providing a resultant fluid flow in the direction B to D (direction W). As the blade approaches C, the lift generated drops to zero and does not again become positive until position C has been passed. As the blade moves from C to A, via D, the lift is generated by the inside of the blade with the resultant fluid flow again in direction W.

Figure 2 shows output power predictions derived from an incident fluid flow in direction W, generated by the turbine assembly as it rotates through 3600. Curve 30a shows 00-1200, curve 30b shows 1200-2400 and curve 30c shows 240 -360 (0 ). The output power P is that delivered to a turbine shaft along the turbine axis. The predictions are derived for a three-bladed assembly under the following conditions: Wind speed = 15ft/sec (4.6ms 1) Tangential blade speed = 30ft/sec (9.2ms-1) Blade area = 1 sq.ft (0.0rum2) Blade coefficient of lift = 0.35 Blade coefficient of drag = 0.04 As shown, the output power P is positive over approximately 3100 rotation.The output power is negative over approximately 400 (froth 3400 to 200) as the blade changes from generating lift with its inner surface to generating lift with its outer surface when travelling against the fluid flow; this is shown by the blade passing through position A in Figure 1. Output power is negative for a further 100 (1750 to 1850) as the blade reverts to generating lift with its inner surface when travelling with the fluid flow; this is shown by the blade passing through position C in Figure 1.

With three equally angularly spaced blades, the components 30a, 30b and 30c are sumeed to give a resultant output power which, as shown by curve 30, is positive over 3600. The number of blades may vary, although an integral multiple of three blades is preferred. A minimum of three blades gives the smoothest theoretical overall response when summing the output from each individual blade whilst minimising turbulence arising from the effect of one blade on the others.

The output power P is proportional to the distance T. When the assembly is subjected to an incident fluid flow and T = 0, that is to say when the turbine axis 14 and the axis of the hub 26 are coincident and the blade axes 16, 24 travel the same circular path, the resultant output power P, supplied to the turbine shaft, is minimised and rotation may cease. To maximise the output power, the turbine and hub axes are spaced apart (i.e. T # 0) and the hub axis is positioned such that the turbine axis to hub axis direction W is aligned with the direction of incident fluid flow. When the turbine assembly is driven to generate a fluid flow, the magnitude and direction of the generated flow may thus be controlled by selection of the distance T and turbine axis to hub axis direction W.

One suitable control mechanism, applied to a rotary fan, is shown in Figure 3. The blades are pivotally attached, at the blade pivot axis, to an annular collar 32 which is mounted on a ball bearing race 34. The outer surface of the collar 32 is linked by a drive belt 36 to the fan motor 38. An opening 40 through the ball race 34 provides access for the hub 26 which is in the form of a bar of circular cross sectional, extending generally parallel to the turbine axis. Linkages (not shown) are pivotally attached to the hub 26 and extend therefrom to the link pivot axis of the blades.

The hub 26 is attached to a control linkage 42 extending perpendicular to the turbine axis. The control linkage 42 is held by a support body 44 which allows movement of the linkage along its major axis only. The support body 44 is slidably mounted on a track 46 extending perpendicular to the linkage major axis. The linkage 42 is thus confined to movement in two mutually perpendicular directions in a plane perpendicular to the turbine axis whilst being prevented from rotating in that plane.

The free end ofthe linkage 42 is connected to a joystick control lever 48. Movement of the lever 48 will thereby move the hub 26. The lever 48 is positioned such that, when it is aligned parallel to the turbine axis at the centre of its available travel, the axis of the hub 26 is coincident with the turbine axis 14 and there is no resultant air flow. Due to the nature of the control linkage mounting 44, 46 the hub 26 will move in the same direction as the lever 48 so that the direction and magnitude of offset of the lever 48 from its central position directly controls the direction and magnitude of the resultant air flow.

An alternative control mechanism to that of figure 3 is illustrated in Figures 4A and 4B which show respectively a sectional elevation and an end view of a rotary fan including the turbine assembly of the present invention. For the sake of clarity, only one of the three turbine blades 12 is shown in figure 4A whilst additional detail (not usually visible) is shown in figure 4B.

Each of the turbine blades 12 is pivotably mounted on an axle 60 extending along the blade pivot axis 16. Each axle 60 is a perpendicular projection from a support body 50 which is rotatable about the turbine axis 14. The support body 50 is rotatably mounted on a fan end plate 52 which carries an electric motor 38 which, through a drive gear 54 and a toothed flange 56 on the support body, rotates the support body 50 and turbine blades 12 about the turbine axis 14.

A linkage 22, from the link pivot axis 24 adjacent the trailing edge 20 of each blade, is pivotally attached to a central hub 26.

As can be seen from figure 4B, the mechanism shown is in a "neutral" position with the turbine and hub axes coincident such that there is no resultant air flow.

The hub 26 is eccentrically mounted on a rotatable inner hub support 62 which is itself eccentrically mounted on a rotatable outer hub support 64. The outer hub support 64 is rotatable about the turbine axis 14. The hub axis to turbine axis separation T, which governs the power of the generated fluid flow, is adjusted by rotation of the inner hub support 62. The direction of hub axis offset from the turbine axis, which governs the direction of the generated fluid flow, is adjusted by rotation of the outer hub support 64.

Rotation of the inner and outer hub supports 62,64 is effected by inner and outer control levers 72,74 which extend radially from respective hub supports.

Conventional rotary fans with fixed blades require a tangential air inlet and rely on vortex effects to generate an air flow in the desired direction. Using the cage turbine of the present invention, a "straight through" air flow is achieved and a rotary fan using the turbine would have the magnitude and direction of the output airflow controllable by one or two simple levers. It will be appreciated that the two control mechanism described are not the only ways of controlling hub location and that itchanical or electromechanical servo motor controls.could also be used, either in place of, or in conjunction with, the control mechanisms described.

It will be appreciated that the cage turbine of the present invention is not limited to use in rotary fans. Other driving applications may include use, either vertically or horizontally positioned, as a marine propulsion unit, or as the turbine of a jet engine. The cage turbine of the present invention may be used as a part of an aircraft wing, forming at least a part of the leading edge thereof, with the resultant fluid flow directed across the upper surface of the wing to produce lift as well as forward motion.

Where the turbine is driven, such as in a wind or water powered turbine generator, the control mechanism allows the turbine to be rapidly and simply adjusted to take account of variations in the direction and magnitude of the incident fluid flow.

Claims

CLAIMS.

1. A cage turbine, rotatable about a turbine axis, in which each turbine blade is pivotably mounted and in which the angle of incidence of each turbine blade is controlled in dependence on the angular displacement of the blade about the turbine axis with the leading edge of each blade being angularly displaced about the turbine axis in the direction of turbine rotation relative to the trailing edge of the blade.

2. Apparatus according to claim 1 in which the trailing edge of each turbine blade is controlled to travel a substantially circular path having its centre offset from the turbine axis.

3. Apparatus according to claim 1 or claim 2 in which the angle of incidence of each turbine blade is controlled by a linkage pivotally attached at one end to the blade and at the other end to a hub, the linkage being rotatable about the axis of the hub which is offset from the turbine axis.

4. A cage turbine, rotatable about a turbine axis, in which each turbine blade is pivotably mounted and in which the angle of incidence of each turbine blade is controlled in dependence on the angular displacement of the blade about the turbine axis by a linkage pivotally attached at one end to the blade and at the other end to a hub, the linkage being rotatable about the axis of the hub which is offset from the turbine axis.

5. Apparatus according to claim 3 or 4 in which each of the linkages is pivotally attached to a common hub and all linkages are rotatable about the axis of the hub.

6. Apparatus according to any of claims 3 to 5 in which the length of the linkages, from the hub axis to the point of pivotal attachment, is substantially the same.

7. Apparatus according to any of claims 3 to 6 in which the linkage is attached to the blade adjacent the trailing edge thereof and is pivotable about a link pivot axis substantially parallel to the turbine axis.

8. Apparatus according to any preceding claim in which each blade is mounted for rotation about a blade pivot axis substantially parallel to the turbine axis.

9. Apparatus according to claim 8 in which the blade pivot axis is adjacent the leading edge of the blade.

10. Apparatus according to claim 8 or claim 9 in which the blade pivot axis of each turbine blade is at substantially the same distance from the turbine axis as the blade pivot axis of each other turbine blade.

11. Apparatus according to claim 7 in which the distance from the link pivot axis of a blade to the hub axis is substantially the same as the distance from the point of pivotal attachment of that blade to the turbine axis.

12. Apparatus according to any of claims 3 to 7 in which the position of the hub axis relative to the turbine axis is adjustable.

13. Apparatus according to claim 12 including a control mechanism for controllably positioning the hub axis relative to the turbine axis.

14. Apparatus according to claim 13 in which the control mechanism oamprises a control linkage attached at one end to the hub and mounted to be movable in each of two mutually perpendicular axes in a plane perpendicular to the turbine axis.

15. Apparatus according to claim 14 in which the free end of the control linkage is attached to a joystick control lever.

16. Apparatus according to claim 15 in which, when the joystick control lever is at the centre of its available movement, the hub axis is coincident with the turbine axis.

17. Apparatus according to claim 13 in which the hub is eccentrically mounted on a first hub support, the first hub support is eccentrically mounted on a second hub support and the first and second hub supports are rotatable about respective first andgsecond substantially parallel axes.

18. Apparatus according to claim 17 in which the second hub support axis is coincident with the turbine axis.

19. Apparatus according to claim 17 or claim 18 including first and second control levers extending from the respective hub supports and operable to effect rotation thereof about the respective hub support axes.

20. Apparatus according to any of claims 13 to 19 in which the control mechanism includes a servomotor position control.

21. Apparatus according to any preceding claim further comprising two spaced apart support bodies between which the turbine blades extend and to each of which each turbine blade is pivotably attached.

22. Apparatus according to claim 3 or claim 4 having a hub and linkage angle of incidence control mechanism at each end thereof.

23. Apparatus according to claim 22 including a control mechanism for control lably positioning the hub axes relative to the turbine axis, the hubs at each end being controlled to move in unison.

24. Apparatus according to any preceding claim in which the turbine blades are equally angularly spaced about the turbine axis.

25. Apparatus according to any preceding claim, having three turbine blades.

26. Apparatus according to any preceding claim in which the number of turbine blades is an integral multiple of three.

27. Apparatus according to any preceding claim in which each turbine blade which is a primary blade is provided with one or more secondary blades positioned adjacent thereto, each secondary blade being controlled to remain substantially parallel to the adjacent primary blade as the angle of incidence of the primary blade is varied.

28. Apparatus according to claim 27 in which each secondary blade is positioned radially outward from the adjacent primary blade with respect to the turbine axis.

29. A cage turbine substantially as hereinbefore described with reference to figures 1 and 2 of the accompanying drawings.

30. A cage turbine including a control mechanism for controllably positioning the hub axis relative to the turbine axis substantially as hereinbefore described with reference to figures 1 and 2 and figure 3 or figure 4 of the acoompanying drawings.