WO2000045048A1

WO2000045048A1 - Flow energy converter

Info

Publication number: WO2000045048A1
Application number: PCT/IE2000/000014
Authority: WO
Inventors: David Callaghan
Original assignee: David Callaghan
Priority date: 1999-01-29
Filing date: 2000-01-31
Publication date: 2000-08-03
Also published as: AU2315800A; IES20000081A2; IE20000082A1

Abstract

A flow energy converter comprises a plurality of vanes (14) mounted in a support means (10) for movement around a closed path (16) and each vane is deflectable to either side of the closed path by rotation about an axis (15) at an angle to its direction of movement along the path. The deflection of each vane (14) is constrained on at least one side of the closed path (16) such that at least for a given direction of fluid flow relative to the converter the cumulative pressure exerted by the fluid on the vanes provides a net force tending to drive the vanes around the closed path.

Description

FLOW ENERGY CONVERTER

This invention relates to a flow energy converter which converts kinetic energy from a moving fluid (liquid or gas) and converts it to mechanical energy suitable, for example, for power generation. According to the present invention there is provided a flow energy converter comprising a plurality of vanes mounted in a support means for movement around a closed path, each vane being deflectable to at least one side of the closed path by rotation about an axis at an angle to its direction of movement along the path, and means for constraining the deflection of each vane on the said at least one side of the closed path such that at least for a given direction of fluid flow relative to the converter the cumulative pressure exerted by the fluid on the vanes provides a net force tending to drive the vanes around the closed path. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figures 1(a) and 1(b) are perspective and side views respectively of a first embodiment of the invention, Figure 1(c) is a cross-sectional plan view of the first embodiment, taken on line C-C of figure 1(b), Figures 2 (a) and 2 (b) are perspective and plan views respectively of a second embodiment of the invention, Figure 2 (c) is an enlarged perspective view of part of the embodiment of figures 2(a) and 2(b),

Figure 3 is a perspective view of a third embodiment of the invention,

Figure 4 is a perspective view of a fourth embodiment of the invention, Figure 5 is a perspective view of a fifth embodiment of the invention,

Figures 6(a) and 6(b) are perspective and plan views respectively of a sixth embodiment of the invention,

Figure 6(c) is an enlarged detail of figure 6(a) ,

Figure 7 is a plan view of a seventh embodiment of the invention, Figures 8 (a) and 8 (b) are perspective views of an eighth embodiment of the invention seen from two different viewpoints.

Figure 8 (c) is a schematic plan view of the eighth embodiment of the invention, Figure 8 (d) illustrates one of the flexible spring links of figure 8 (a) , and

Figure 8 (e) shows a single vane and stop member assembly m the embodiment of figure 8(a) .

Before describing the embodiments, it should be made clear that the use of terms such as "vertical",

"horizontal", "upper", "lower", "left", "right" and the like when describing any particular embodiment is intended to refer to that embodiment as viewed in the figures being referred to, and is not intended to limit the orientation of any particular embodiment in use.

Referring to figures 1(a) to 1(c), a flow energy converter according to the first embodiment of the invention is m the general form of a drum or cylinder 10 comprising axially spaced circular top and bottom plates (or spoked wheels) 11 mounted for rotation about an axis 12. Other embodiments may have only one plate or spoked wheel, at the top or bottom only. A plurality of similar flat vanes 14 are mounted at intervals around the periphery 16 of the arum 10, i.e. between the circumferential edges of the plates 11, for movement around the closed circular path defined by the periphery 16 as the drum 10 rotates. Each vane 14 is pivotally mounted at the periphery 16 of the drum 10 for rotation about an axis 15 substantially parallel to the axis 12, i.e. at right angles to the direction of movement of the vanes 14. Thus each vane can be deflected inside the periphery 16 of the drum, as seen for the vanes generally at the top and right hand side of figure 1 (c) , or outside the periphery 16 of the drum, as seen for the vanes generally at the bottom and lower left hand side of the drum m figure 1 (c) .

The deflection of each vane 14 is constrained by stop means to an angle theta on each side of the periphery 16, as indicated for the vane 14' at the 3 o'clock position m figure 1(c), but can pivot freely between these two extreme positions. The stop means is not shown but may be of a kind shown m later embodiments. The angle theta may be from 0.5 to 179.5 degrees, and m figure 1 (c) it is assumed to be about 60 degrees. Since the drum 10 consists essentially only of the circular top and bottom plates 11 with the vanes 14 pivotally supported between them, the drum 10 is hollow and fluid flow is possible between the vanes 14 and through the interior of the drum 10.

When fluid is flowing relative to the drum 10 m the direction indicated by the arrow 20, figure 1 (c) , those vanes 14 which at any given moment are generally on the right of the drum, i.e. from about the 12 o'clock position to the 5 o'clock position m figure 1 (c) , are deflected inside the drum periphery by fluid pressure until they come to stop against their respective stop means. These vanes are referred to herein as "active", which is to say that they are held non-parallel to the fluid flow direction 20 and hence offer resistance to the fluid flow. This resistance causes a pressure drop across the active vanes which tends to drive the drum 10 in the direction of rotation indicated by the arrow 22. It will be seen that each active vane 14 tends to drive the drum 10 in the same (clockwise) direction and therefore their effect is cumulative . Those vanes 14 which at any given moment are generally on the left of the drum 10, i.e. from about the 7 o'clock position to the 11 o'clock position m figure 1(c), are free to "feather" m the fluid flow between their stop positions, and hence offer little resistance to the fluid. These vanes are referred to herein as "passive" vanes.

At about the 5 o'clock position of the drum 10, as seen within the circled region 24 m figure 1 (c) , each vane "flips over" or reverts from being inside the periphery 16 to being outside the periphery 16.

However, it remains active for a short while because the fluid pressure drives it against its opposite stop means and it remains held non-parallel to the fluid flow direction 20 until rotation of the drum 10 brings it parallel to the fluid flow direction 20 at around the 7 o'clock position. Thereafter it becomes passive and is free to feather between its stop positions until about the 12 o'clock position. It will be seen that the fluid pressure on the reverted vanes 14 between the 5 o'clock and 7 o'clock positions will also tend to drive the drum 10 in the same direction 22.

The result is that the pressure cumulatively exerted by the fluid on all the vanes 14 provides a net force tending to drive the drum 10 m the direction of rotation 22, because the pressure on the active vanes tending to drive the drum m the direction 22 is greater than the drag on the feathered passive vanes. Thus, provided the fluid is flowing strongly enough that this net force is sufficient to overcome the mechanical friction of the drum 10 and the resistance offered by power transferring apparatus (not shown) coupled to the drum 10, the drum will rotate and continue to rotate all the while the fluid is flowing. It will be observed that m this embodiment, due to the circular symmetry of the drum 10, the converter works equally effectively whatever the direction of fluid flow.

A significant advantage of the above arrangement, where the vanes 14 are constrained both on the inside and outside of the drum 10, is that, due to the flow of fluid between the plates (or spoked wheels) 11, at any given moment the vanes 14 are active substantially entirely from the 12 o'clock position to the 7 o'clock position, i.e. over more than half the total length of the closed path defined by the the periphery 16 of the drum 10.

If desired, however, the deflection of each vane 14 could be constrained on only one side of the periphery 16. For example, if the deflection of each vane were limited only on the inside of the periphery 14, after reversion the vanes would immediately be permitted to feather, and thus become passive earlier than they otherwise would. This is indicated by the dashed lines on the three vanes m the region of the 6 o'clock position m figure 1(c) .

A further significant advantage of the above embodiment, is that the transition of each vane 14 from being outside the periphery to inside the periphery, i.e. as it moves from the 7 o'clock position to the 12 o'clock position, is very gradual, so that rapid reversion, and attendant shock, is avoided. Thus the device is less prone to mechanical failure. Referring now to figures 2 (a) to 2 (c) , a second embodiment of the invention is in the form of a wide resilient belt 30 passing around an elongated closed path 32 around two guide rollers 34 having substantially parallel axes of rotation 35. The belt is provided with a large number of vanes constituted by flaps 36, each such flap being formed by cutting through the material of the belt on three sides and all the flaps facing in the same direction around the belt, as seen m more detail m figure 2 (c) . Each flap or vane 36 has an unstressed position substantially in alignment with the belt 30, but can be deflected, about an axis 38 perpendicular to the direction of belt movement, out of the plane of the belt 30 to either the inside or the outside of the closed path 32 against the resilient bias tending to return it to the unstressed position. Accordingly, the deflection of each vane is constrained, by the resilient bias, on each side of the belt. Each flap or vane can also be pivot mounted with stops 76 as shown for example m Figures 6(a) and 6(b) .

When a flowing fluid is incident on one elongate side of the belt 30, as indicated by the arrow 40 m figures 2(b) and 2(c), the vanes 36 on that side of the belt are driven by fluid pressure to the inside of the belt against the resilient bias. This is seen for the upper vanes m fiσure 2 (b) and tne vanes on the right hand side in figure 2 (c) . However, due to the resilient bias tending to urge the vanes back into alignment with the belt, the vanes are not free to feather m the fluid flow and, accordingly, each assumes an active position non-parallel to the direction of fluid flow resulting m a pressure difference P1+/P1- across each vane 36 which cumulatively tend to drive the belt m the direction indicated by the arrow 42. Further, after passing through the interior of the belt, the fluid emerges from the other side by deflecting the vanes 36 on that side of the belt to the outside of the belt. This is seen for the lower vanes in figure 2 (b) and the vanes on the left hand side m figure 2(c). A further pressure drop P2+/P2- occurs across these latter vanes which also tends to drive the belt m the direction 42. Overall, therefore, the cumulative pressure exerted by the fluid on the vanes 36 provides a net force tending to drive the belt 30 around the closed path 32. Again, provided the fluid is flowing strongly enough that this net force is sufficient to overcome the mechanical friction of the belt 30 and guide rollers 34 and the resistance offered by power transferring apparatus coupled to the guide rollers, the belt will continue to rotate around the guide rollers 34 all the while the fluid is flowing. In this embodiment the converter s positioned m use such that the angle alpha, figure 2 (b) , between the direction of fluid flow and the longitudinal direction of the belt 30 is between zero and 180 degrees, and preferably about 45 degrees.

Similarly to the first embodiment, the passage of fluid through the belt 30 from one longitudinal run to the other ensures that at any αiven moment the vanes 36 are active over most of the length of the belt, substantially the only inactive vanes being those on the periphery of the rollers 34. In figure 3, two converters as described in figures 2 (a) to 2 (c) are supported rigidly m a V-shape m a frame 44. The angle of separation beta between the two converters is about 90 degrees, but it could be from about 10 to about 170 degrees. The frame 44 is rotatable about an axis 46 perpendicular to the axes of rotation of the guide rollers 34 and which is located at or near the apex of the V. Thus the two converters provide a balanced dual system which can pivot as a whole to point upstream into the fluid flow and thereby assume at all times an appropriate angle to the fluid flow direction.

The embodiment shown in figure 4 is similar to the embodiment of figures 2(a) to 2(c) except that m this case the endless "belt" comprises a succession of rigid rectangular panels 50 pivotally connected at their adjacent major edges 52 to form a chain which follows a closed path around two hexagonal or other polygonal guide "rollers" 54 rotatable about parallel axes 56. Each panel 50 has a large number of flaps or vanes 58, each of which is pivotable about a respective axis parallel to the axes 56 for deflection out of the plane of the respective panel either to the inside or to the outside of the closed path defined by the movement of the panels around the guides 54. All the vanes face m the same direction around the closed path. Mechanical stop means (not shown) limits the angle by which each vane can deflect on each side of the respective panel to an angle theta, as described for the embodiment of figures 1(a) to 1(c).

The operation of this embodiment is essential! the same as for figures 2 (a) to 2 (c) , with energy conversion likely to be more efficient when the fluid flow is incident at an angle of about 45 degree to the longitudinal direction of the converter. Thus, similarly to figure 3, it is possible to arrange two such converters in a V-formation to always face upstream of the fluid flow, as shown m figure 5. Referring now to figures 6(a) to 6(c), a further embodiment of the invention comprises upper and lower chains 60', 60" which pass around upper and lower pairs 62' and 62" respectively of sprocket-type wheels. The sprocket wheels 62', 62" vertically one above the other at each end of the apparatus are mounted on respective hubs 64, figure 6(c), for rotation about parallel axes 66.

The chains 60 comprise rigid links 68 pivoted end to end at pivot points 70, each pivot point 70 m the upper chain 60' being located vertically above a respective pivot point m the lower chain 60". A plurality of vanes 72 are mounted vertically between the chains 60' and 60". In particular, each vane 72 is mounted for pivoting about a vertical axis passing through a respective pair of vertically aligned pivot points 70, so that it can revert either to the inside or to the outside of the closed path 73 defined by the movement of the chains 60 around the sprocket wheels 62. Thus the vanes 72 along the run of the chains

60 nearest the viewer m figure 6(a) and at the bottom of figure 6(b) are deflected outside the closed path 73 whereas the vanes 72 along the top run of the chains 60 furthest from the viewer m figure 6(a) and at the top of figure 6(b) are deflected inside the closed path. In this connection it will be seen that each vane ^"?2 has major and minor surface area portions 72' and 72", figure 6 (b) , on opposite sides respectively of the axis of deflection of the vane. Accordingly, in this specification a reference to the vane being deflected to one side or the other of the closed path is to be understood to be a reference to the major surface area portion of the vane being so deflected. Each link 68 further carries a pair of fixed stop arms 74 arranged m a V-shape and each bearing a stop member 76 at its free end. These stop members 76 limit the deflection of each vane 72 to an angle theta on each side of the closed path, as described for the embodiment of figures 1(a) to 1(c).

This embodiment operates m principle the same as the embodiments of figures 2 (a) to 2 (c) and figure 4. Thus, referring to figure 6(b), fluid flow in a direction towards one side of the converter, for example as indicated by the arrows 78, causes the vanes 72 on that side to be deflected inside the closed path 73. However, they are there constrained by the stop members 76 and hence they are held m an active position non-parallel to the fluid flow direction. This tends to drive the chains 60 m the direction of the arrow 79.

After passing through the converter the fluid exiting from the other side deflects the vanes on the exit side outside the closed path. In this case the vanes 72 are also held in an active position by the respective stop members 76, which also tends to drive the chains 60 m the direction of the arrow 79.

Overall, therefore, and provided the distance between one reverting vane and the next is sufficient to allow the particular fluid to flow through the apparatus without a significant element cf stallmc, the cumulative pressure exerted by the fluid on the vanes 72 provides a net force tending to drive the chains 60 around the closed path 73. Although figure 6(b) shows the fluid incident at 90 degrees to the longitudinal direction of the converter, it will work for wide range on incident angles, as described for preceding embodiments. This embodiment will operate effectively under water, in rivers or in currents such as those found m ocean, sea, lake or estuary, and m alternating ortidal currents the apparatus will rotate m the same direction regardless of an upstream or downstream direction of flow. The apparatus can be shut down by adjusting or enabling the stop arms to permit all vanes 72 to feather, after which a light brake will maintain the apparatus stationary. Also, by adjusting the operational length of the stop arms 74, i.e. adjusting the angle theta, it is possible to adjust the speed of rotation of the hubs 64 and accordingly the power output .

Figure 7 shows a modification of the embodiment of figures 6(a) to 6(c) which differs solely m that only one arm 74 and stop member 76 is provided on each link 68, so that the deflection of the vanes 72 is constrained only on the inside of the closed path 73. Thus the vanes 72 on the far side of the apparatus from the oncoming fluid are free to feather. This is shown for the vanes along the lower run of the chains 60 m figure 7, assuming that the fluid is flowing m the direction indicated by the arrow 80. Nevertheless, the pressure cumulatively exerted by the fluid on all the vanes 72 provides a net force tending to drive the chains 60 m the direction indicated by the arrow 82, because the pressure on the active vanes tending to drive the drum in the direction 82 is greater than the drag on the feathered passive vanes. Figures 8 (a) to 8 (e) show an embodiment of the invention for use as, for example, an undersea unit but it will be appreciated that the converter will function m any suitable gas or liquid. This embodiment is m principle the same as that described with reference to figures 6(a) to 6(c), and the same reference numerals have been used for the same or equivalent components. The present description will concentrate on the differences from figures 6(a) to 6(c). In the undersea unit the chains 60', 60" are preferably made from flexible spring links 90, figures 8 (c) to 8 (e) , rather than rigid links 68 or conventional chain links which can involve additional cost, and because the links 90 are able to flex the present embodiment uses circular wheels 92', 92" at each end of the structure rather than the sprocket wheels 62', 62" used m the embodiment of figures 6(a) to 6(c) or conventional sprocket wheels. Thus the links 90 pass around and flex to conform to the circumference of wheels 92. The wheels 92 are flanged to accommodate the chains 60, thereby to retain the chains 60 in position on the wheels' circumference. The undersea unit also has generally U-shaped guide tracks 94 which support the length of chains 60 between the wheels 92, and smooth their acceptance onto and off each wheel 92.

Each spring link 90, figure 8 (d) , consists of a spring strip flat or other suitable bar with a suitable coupling such as a single annular coupling component 96 at one end and a pair of axially spaced annular coupling components 98 at the other end. Ir assemblinσ each chain 60 the coupling component 98 at the end of each link 90 is inserted between the spaced coupling components 98 at the adjacent end of the next link so that the apertures m all three components are aligned, and the ends of the two links are retained pivotally coupled together by a single pin passing through all three coupling components. These retaining pins are carried by the vanes 72 and the stop arms 74, as will now be described with reference to figure 8 (e) .

Each vane 72 has a pair of axially aligned pins 100 at the top and bottom respectively, and these pins 100 are inserted into the aligned coupling members 96, 98 at the ends of adjacent links 90 m the top and bottom chains respectively and then the free ends of the pins 100 are swaged over to inhibit subsequent withdrawal. This mechanism thus couples the adjacent ends of the links 90 together and also allows the necessary pivoting of the vanes to either side of the chains. However, this connection is done only for every alternate link coupling in the top and bottom chains.

The link couplings intermediate to those which are connected together by the pins 100 are connected together by pins 102 carried by the stop arms 74. Thus each V-shaped pair of stop arms 74 has a pm 102 which is inserted into the intermediate aligned coupling members 96, 98 at the ends of adjacent links 90 m each chain. In this case it is not desired that the stop arms 74 be free to pivot, and accordingly a bifurcated retainer bracket 104 is fixed to the free end of each pm 102 and extends towards and either side of the link 90. This not only prevents the stop arms 74 from pivoting, but also prevents withdrawal of the pm 102 from the coupling members 96. 98.

Referring back to fiσures 8(a) and 8 (b^ , the structure is supported oy a pressurised housing 110 to provide overall buoyancy and contain generators for the conversion of the rotation of the hubs 64 to electric, hydraulic or other forms of power. The housing 110 is itself retained m position by locating ties 112 which also support power cables and service links to shore. To assist in buoyancy, each vane 72 also has a buoyancy element 114 at the top. As seen m figure 8(e), each vane 72 also has an irregular surface to avoid transverse or shunting movements. This can be achieved by creating a "dimpled" type surface on both sides of each inverting vane 72. It will be appreciated that in the embodiments of Figs. 4, 6 and 8, like the embodiment of Fig. 2, the passage of fluid through the device from one longitudinal run to the other ensures that at any given moment the vanes are active over most of the length of their path of travel.

Claims

CLAIMS :

1. A flow energy converter comprising a plurality of vanes mounted m a support means for movement around a closed path, each vane being deflectable to at least one side of the closed path by rotation about an axis at an angle to its direction of movement along the path, and means for constraining the deflection of each vane on the said at least one side of the closed path such that at least for a given direction of fluid flow relative to the converter the cumulative pressure exerted by the fluid on the vanes provides a net force tending to drive the vanes around the closed path.

2. A flow energy converter as claimed m claim 1, wherein the vanes are deflectable to either side of the closed path and are so arranged that, as a result of fluid flow through the support means, at any given moment the vanes are active (as herein defined) over more than half the total length of the closed path.

3. A flow energy converter as claimed in claim 1 or

2, wherein the constraining means constrains the deflection of the vanes on each side of the closed path.

4. A flow energy converter as claimed claim 1, 2 or 3, wherein the vanes are pivotally mounted on the support means and the constraining means comprises mechanical stop means which limits the angle of pivoting of the vane on one or both sides cf the closed path.

5. A flow energy converter as claimed m claim 1, 2 or 3, wherein the vanes are resiliently attached to the support means and have an unstressed position substantially m alignment with the closed path, and wherein the constraining means comprises the resilient attachment of the vanes to the support means which tends to urge the vanes to the unstressed position upon deflection thereof to either side of the closed path.

6. A flow energy converter as claimed any preceding claim, wherein the support means supports the vanes for movement along a circular path.

7. A flow energy converter as claimed any one of claims 1 to 5, wherein the support means is the form of a chain or belt passing m a closed path around at least two guide members rotatable about substantially parallel axes.

8. A flow energy converter as claimed m claim 7, wherein two support means are provided each passing along an elongated closed path around two rotatable guide members, and wherein the two support means are arranged in a V-shape and are pivotable as a whole about an axis substantially parallel to the axes of rotation of the guide members and located at least approximately at the apex of the V.