EP2831407A2

EP2831407A2 - A screw device for a power generation or a material handling apparatus

Info

Publication number: EP2831407A2
Application number: EP13719132.6A
Authority: EP
Inventors: Gordon FRANKLAND
Original assignee: Towerlane Ltd
Current assignee: Towerlane Ltd
Priority date: 2012-03-26
Filing date: 2013-03-26
Publication date: 2015-02-04
Also published as: GB201205308D0; GB2500619A; GB2500619B; WO2013144610A2; WO2013144610A3

Abstract

A screw device for a power generation or a material handling apparatus is disclosed. In particular a support structure or central cylinder is provided. To the central cylinder screw members are connected. The screw members are formed from pipe portions that are joined together and wound around the central cylinder to form a number of helical pipes. Attached to the upper end of each helical pipe are feeder members that together form an annular aperture feeding the helical pipes. The number of feeder members and pipes is selected depending upon the design flow of the device.

Description

A Screw Device for a Power Generation or a Material Handling Apparatus

The present invention relates to a screw device for use in a power generation or a material handling apparatus and relates particularly, but not exclusively, to an Archimedes screw for use in a small scale hydroelectric power generation device.

The use of an Archimedes screw in small scale hydroelectric power generation has become increasingly popular in recent years as they provide an efficient method of generating electricity from the potential energy of low head hydropower resources such as weirs and are ^v fish- friendly' . There are several types of Archimedes screw.

In a 'closed' Archimedes screw there is a central cylinder and extending from this in an axially outward direction are one or more helical blades turning around it like the thread of a screw. A concentric second cylinder is connected to the outermost edge of the blades and water is able to pass through the channels formed between the inner and outer cylinders and adjacent blades. The interaction between the angle to the horizontal of the screw and the helical blades splits these channels into a number of 'buckets' which are off centre with respect to the axis of the screw so the weight of water in them causes the screw to rotate. In a pumping application the buckets travel up the screw when it is rotated in the right direction so lifting water or other material to the top of the screw. An 'open' Archimedes screw is formed in the same manner as the closed screw but without the second outermost cylinder which is functionally replaced by a channel/trough or cylinder fixed in relation to the ground and shaped to closely follow the outermost edge of the blade as it rotates; 'buckets' are formed between adjacent blades, this trough and the central cylinder. The gap between the outermost edge of the blade and the channel must be kept to a minimum to avoid excess leakage of water from the 'buckets' .

Archimedes screws of the prior art are subject to strong economies of scale and this has limited their commercial use to exceptionally good and accessible sites which are comparatively rare and most commercial installations have employed 'open' Archimedes screws.

The high cost of smaller installations arises from multiple causes including the high costs for civil engineering works. Also, every site has a unique combination of head and design flow so installers must choose between the bespoke manufacture of a unit optimised for the site (in which case it may cost more and certain manufacturing techniques will be precluded) and a standard unit (in which case it may not be optimally sized for the site) . Most installations require a large screw and transporting the screw assembly to site and handling / installation is therefore expensive. The transportation and handling problems are exacerbated where vehicle access is difficult, for example in remote locations or where there is no road access right up to the site. In addition to these general disadvantages of the prior art, the efficiency of an 'open' Archimedes screw is reduced at smaller sizes by the leakage of water past the blade tips. This leakage is proportionately greater for smaller units or for larger units with the smaller buckets that result from having more interleaved blades on a screw of given diameter. Other things being equal, the smaller the buckets the more slowly the performance of an Archimedes screw declines as the screw's angle to the horizontal increases therefore more and smaller buckets enable a steeper angle and correspondingly shorter screw. An 'open' screw with larger buckets is therefore most effective at a shallower angle (and correspondingly greater length) .

'Closed' Archimedes screws do not suffer from leakage flow past the blade tips but can suffer leakage at the top end where water is fed into the rotating mechanism. Moreover, their size is limited by the weight of mechanism plus contained water that must be supported by the bearings. On the other hand they can in principle be made with more smaller buckets and therefore retain acceptable performance to significantly steeper angles than Open' screws which means that they can be shorter for a given head.

One variant of 'closed' Archimedes screws employs a number of helical pipes to form the channels through which the water or other material flows rather than utilising the blades and inner and outer cylinders as described above and such designs have often been built for demonstration purposes . An example of the prior art is shown in French patent publication no. FR2532012, which shows an Archimedes pump device that utilises pipes to form the closed screw helices. However, it does not address the efficient transfer of water with minimal turbulence or loss into the end of the screw which is necessary in hydropower applications and desirable in pumping applications.

Preferred embodiments of the present invention seek to overcome the above described disadvantages of the prior art .

According to an aspect of the present invention, there is provided a screw device for a power generation or a material handling apparatus, the device comprising: - at least one support structure axially rotatable around an axis ; a plurality of substantially tubular material engaging elements attached to and extending around and substantially along the length of the support structure thereby forming an Archimedes screw device; and at least one feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element and a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device. For optimum efficiency and minimal turbulence or loss in transferring water or other material into a screw device, an annular entrance should be provided that is divided depending upon the number of tubular material engaging elements being fed. Each of the material engaging elements or pipes in the screw device has an optimum volume of water that it can carry in each turn of the helical pipe . This can be used to calculate the optimum rate at which water should enter each pipe based on factors such as the diameter/size of the pipe and the rotation speed of the screw (which has an optimum rate and sometimes also a regulatory limit) . For example, a given size of pipe may optimally handle a flow of water into it of 100 litres per second. As a result, if the design flow at a particular site is 200 litres per second, a screw device having two pipes would ideally be provided to handle this flow. However, if the design flow rate at a site is 600 litres per second, the screw device should ideally be provided with six such pipes and so on up to the maximum number that can be fitted around the central cylinder. If the design flow exceeds the maximum possible number of material engaging elements on a screw, then a second screw in parallel to the first can be provided and so on.

As a result, screw devices can be formed mainly from a kit of standard parts that can handle a wide variety of flow rates by simply changing the shape of the feeder members that form the entrance aperture to the screw device . The pipes remain the same and the support structure remain very nearly the same (the length may vary) , thereby reducing manufacturing costs at the same time as enabling the device to customised for the site. By making the channels from pipe segments in a 'closed' screw it is possible to economically utilise more but smaller pipes (and therefore buckets) . This is because the pipe segments can be cheaply mass produced by extrusion or moulding, and also there is no leakage flow to worry about. Utilising more, smaller buckets means in turn that performance is better (other things being equal) at steeper angles and as a result, the overall screw can be shorter and cheaper. In a preferred embodiment, at least one said material engaging element comprises a plurality of pipe portions.

By forming the material engaging elements from a plurality of pipe portions, the advantage is provided that a screw device can be assembled on site from a large component in the form of a support structure (for instance a central cylinder) with the addition of smaller components in the form of the pipe portions. The largest single component is therefore the support structure which is significantly smaller, lighter and easier to handle than the whole screw device although, where access is good, partially or wholly pre-assembled screws might be craned into position. This in turn reduces transport and handling costs for example by significantly reducing the size of the vehicle that is required to transport, handle and manoeuvre the screw device into place. As a result, screw devices of the present invention can be used in places where access restricts the size of vehicle that could assist in the installation of the screw device. Moreover, there is no gap between blade tips and trough that must be kept as small as possible so making the installation less demanding of accuracy. In another preferred embodiment, the device comprises a single said feeder member that feeds into a plurality of material engaging elements .

The device may further comprise a plurality of feeder member with one feeder member per material engaging element .

In a further preferred embodiment the support structure comprises a substantially cylindrical body.

According to another aspect of the present invention, there is provided a power generation apparatus comprising: - at least one screw device as defined above; and at least one power generation device for converting rotation of said screw device into electrical power.

According to a further aspect of the present invention, there is provided a material handling apparatus comprising: - at least one screw device as defined above; and at least one drive device for providing rotational drive to at least one said screw device.

According to an aspect of the present invention, there is provided a kit of parts for forming screw a device for a power generation or a material handling apparatus, the device comprising:- at least one support structure axially rotatable around an axis; a plurality of substantially tubular material engaging elements for attaching to and extending around and substantially along the length of the support structure thereby forming an Archimedes screw device; and a plurality of feeder members, each feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element and a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device, one or more feeder members being selected to be used in the screw device depending upon the optimum flow to be carried by the screw device . According to another aspect of the present invention, there is provided a method of making a screw device for a power generation or a material handling apparatus, comprising: - providing at least one support structure axially rotatable around an axis; attaching a plurality of substantially tubular material engaging elements to the support structure such that they extend around and substantially along the length of the support structure thereby forming an Archimedes screw device; and engaging around an end of at least one material engaging element at least one feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element, the feeder member also having a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device wherein said feeder member is selected from a plurality of differently sized feeder member each designed to engage and seal the same sized material engaging element but designed that alone or together the feeder members feed into a different number of material engaging elements.

The method may further comprise determining an optimum flow for the screw device and selecting the number of material engaging elements depending on the optimum flow. Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense, with reference to the accompanying drawings in which: - Figure 1 is a perspective view of a screw device of the present invention;

Figure 2 is a perspective view of a feeder member used in the screw device of Figure 1;

Figures 3 and 4 are perspective views of a series of feeder members of Figure 2 ; and Figures 5 and 6 are perspective views of a series of feeder members of an alternative embodiment of the present invention. Referring to Figure 1, a screw device 10 is provided for use in a power generation device, such as an Archimedes screw turbine or in a material handling apparatus, with the device shown in Figure 1 particularly for use in an Archimedes screw turbine or pump. The screw device 10 has a support structure or central cylinder 12 that includes an axle 14 having a lower axle end 16 and an upper axle end 18. The central cylinder 12 is typically formed as a cylinder and has the axle 14 mounted at its centre of rotation .

The screw device 10 also has a plurality of substantially tubular material engaging elements or pipes 20 attached to and extending around and substantially along the length of the central cylinder 12 from adjacent the upper axle end 18 to the lower axle end 16. The pipes 20 are formed from pipe sections 22 that are typically identically formed and joined together to form the pipe 20 that spirals around the central cylinder 12. The pipe sections are attached to the central cylinder by any suitable means which includes bolts fastened to the central cylinder and pipe section and/or by strappings extending around the outside of the pipe portions thereby holding them into engagement with the central cylinder 12. Adjacent the upper axle end 18, at least one feeder member 24 is provided. The feeder member 24 has a first or output end 26 that is sized to engage and substantially seal around an end of a pipe 22 so as to allow transfer of material from said feeder member to said material engaging element. The feeder member 24 also has a second or input end 28 that combines with other feeder members to form a substantially annular entrance aperture to the pipes 20 of screw device 10, as shown most clearly in Figure 3. When the screw device 10 is used in a turbine, part of the flow of the river is diverted to direct water into the feeder members 24 at a depth in normal flow conditions somewhat greater than the radial length R of feeder member 24. A device such as an upward pointing cone formed around the screw axle and covering the space radially inward of the feeder members 24 serves to direct flow into the feeder members and prevent it running down the centre of the support structure thereby adding weight without contributing power output.

In the embodiment shown in Figures 3 and 4, six feeder members 24 are brought together and the six input ends 28 together form the annular inlet .

In an alternative embodiment, shown in Figures 5 and 6, the annular inlet is formed from the input ends 28 of three feeder members 24 that are sized differently from those shown in Figures 3 and 4. However, it should be noted that the first ends 26 of feeder members 24 are sized similarly to those in Figures 3 and 4 and are designed to attach to pipes 20 that are the same size for both embodiments . As a result, an embodiment of the present invention using the feeder members 24 shown in Figures 5 and 6 will feed to three pipes 20 that are wound in a helical manner around the central cylinder 12 instead of the six pipes 20 used for the feeder members 24 in Figures 3 and 4 and as shown in Figure 1. The other components of the screw device 10, particularly the central cylinder 12 and pipes 20, formed from pipe sections 22, are the same for both embodiments and it is only the feeder members 24 that change, although less pipe sections 22 are required for the embodiment having three feeder members 24. It will be immediately apparent that the screw device 10 having the three feeder members shown in Figures 5 and 6 is designed to work with a flow rate of approximately half that which the embodiment shown in Figures 1, 3 and 4 is designed to use. As a result, the major components of the screw device 10, namely the central cylinder 12 and pipe sections 22, are standard with the feeder members 24 changing depending upon the design flow rate of the screw.

For example, the pipes 20 in a screw device 10 may be designed for and sized to operate with a flow rate of 100 litres per second per pipe at the optimum rotational speed. As a result, on a river with an anticipated average flow of 200 litres per second that can be utilised for the screw turbine, a pair of feeder members 24, each having a input end 28 in the form of a half-annulus , will be used together with two pipes 20 to form the screw device 10. However, if the average usable flow for the water course is 500 litres per second, then five feeder members that each form a fifth of the annulus are used to feed into five pipes 20. The support structure can be made in any convenient form including, but not limited to, a cylinder formed from thin steel plate or composite materials of sufficient strength. It may be pierced by openings to facilitate assembly and allow maintenance inspections and, if necessary, treated and/or painted to prevent corrosion. It may also have holes for bolts to secure pipe clamps or other fixings to hold the material engaging elements securely in place. At each end the support structure is fixed securely to a stub axle by any of the well-known means .

The material engaging elements can be extruded as helical pipes or they can be moulded in segments from a suitable grade of plastic or plastic composite. The feeder devices can be moulded from a suitable grade of plastic or made from steel or other suitable material .

In use for hydropower, water in a river is directed into a channel such that a flow of water is directed towards a screw device 10. As a result, water should enter the feeder members 24 through the input end 28 which acts as a funnel directing the flow past the output end 26 and into the pipes 20. Because the pipes 20 form multiple helices around the central cylinder 12, the weight of water in a portion of pipe 20 causes the screw device 10 to rotate in the well-known manner of an Archimedes screw acting as a turbine. This rotation of a screw device 10 allows power to be drawn from the screw device 10 either via the axle 14 or from other well-known means.

In use as a pump, the input end 28 of a screw device 10 is immersed in the water or other material to be pumped and as it rotates water or other material is scooped into the feeder members 24 and then directed by them into the pipes 20 where is collects into buckets which are lifted to the top of the screw by its rotation. It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, support for the screw device may be provided by using rollers engaging an external surface of the screw device rather than using axle 1 . Furthermore, central cylinder 12 may be provided with apertures in its curved surface allowing access and making attachment of the pipe sections to the central cylinder 12 easier. In principle any number of feeder members 24 can feed into any number of pipes, including a single pipe with a large annular feeder member. However, a larger number of smaller material handling elements is more likely to snag debris and is likely to have a higher ratio of material and manufacturing cost to the total flow they can handle plus a larger number of fixings which again increases costs. Taken together these considerations limit the maximum number of material handling elements that is cost- effective .

Claims

1. A screw device for a power generation or a material handling apparatus, the device comprising: - at least one support structure axially rotatable around an axis ; a plurality of substantially tubular material engaging elements attached to and extending around and substantially along the length of the support structure thereby forming an Archimedes screw; and at least one feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element and a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device.

2. A screw device according to claim 1, wherein at least one said material engaging element comprises a plurality of pipe portions .

3. A screw device according to claim 1 or 2, wherein said device comprises a single said feeder member that feeds into a plurality of material engaging elements.

4. A screw device according to claim 1 or 2, wherein said device comprises a plurality of feeder members with one feeder member per material engaging element.

5. A screw device according to any one of the preceding claims, wherein said support structure comprises a substantially cylindrical body.

6. A screw device for a power generation or a material handling apparatus substantially as hereinbefore described with reference to the accompanying drawings.

7. A power generation apparatus comprising: - at least one screw device according to any one of claims 1 to 6 ; and at least one power generation device for converting rotation of said screw device into electrical power.

8. A material handling apparatus comprising: - at least one screw device according to any one of claims 1 to 6; and at least one drive device for providing rotational drive to at least one said screw device.

9. A kit of parts for forming screw device for a power generation or a material handling apparatus, the device comprising :- at least one support structure axially rotatable around an axis ; a plurality of substantially tubular material engaging elements for attaching to and extending around and substantially along the length of the support structure thereby forming an Archimedes screw device; and a plurality of feeder members, each feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element and a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device, one or more feeder members being selected to be used in the screw device depending upon the design flow to be carried by the screw device .

10. Method of making a screw device for a power generation or a material handling apparatus, comprising: - providing at least one support structure axially rotatable around an axis; attaching a plurality of substantially tubular material engaging elements to the support structure such that they extend around and substantially along the length of the support structure thereby forming an Archimedes screw device; and engaging around an end of at least one material engaging element at least one feeder member having a first end sized to engage an end of at least one material engaging element so as to allow transfer of material from said feeder member to said material engaging element, the feeder member also having a second end forming, or combining with other feeder members to form, a substantially annular entrance aperture to the material engaging elements of the screw device wherein said feeder member is selected from a plurality of differently sized feeder member each designed to engage and seal the same sized material engaging element but designed that alone or together the feeder members feed into a different number of material engaging elements.

11. A method according to claim 10 further comprising determining a design flow for the screw device and selecting the number of material engaging elements depending on the optimum flow.