Recirculating Hydro-Pneumatic Impulse Turbine

Abstract

The recirculation hydro-pneumatic impulse turbine includes a collector assembly having a central draft tube extending below the collector assembly, a collector plate having a generally horizontal upper surface with the draft tube configured to be in fluid communication with the upper surface, and a series of drive cups circumferentially disposed about the upper surface, a drive assembly around the central draft tube having a fluid inlet at its lower end in fluid communication with the lower end of the draft tube and a plurality of outlet nozzles at its upper end configured to be tangentially disposed, and a central air tube having an upper air inlet and a lower air distribution manifold having at least one venturi outlet capable of entraining air into the fluid to assist in moving the fluid upward from the lower end of the drive assembly to the outlet nozzle. In use, a fluid jet formed at the outlet nozzle engages the drive cup to create relative rotation between the outlet nozzle and the drive cup about a vertical axis such that the rotation can provide useful work, and fluid then flows from the drive cup, across the upper surface of the collector plate, down the draft tube and into the fluid inlet of the drive assembly where the fluid, along with air, is recirculated back to the outlet nozzle.

Description

[Technical field]

[0001] Related Applications This application claims convention priority to Australian Provisional Patent Application No. 2022900497, filed March 2, 2022, the contents of which are incorporated herein by reference.

[0002] The present invention relates to impulse turbines that convert hydraulic energy (among other energies) to mechanical or electrical energy, including the generation of useful work from the kinetic energy of a flowing fluid, such as water, which may be useful in power generation or mechanical drive applications. [Background technology]

[0003] Hydroelectric power typically utilizes a one-time flowing fluid, such as water held in a dam, to convert kinetic energy into electricity. Power output is the product of the vertical head and the flow rate at a particular location when the head provides the water pressure, so a higher head or flow rate generally results in a higher power output, since the higher the head, the greater the pressure driving the turbines.

[0004] By way of explanation, a turbine is a rotating mechanical device that extracts kinetic energy from a flowing fluid and converts that energy into useful work, whereas a hydraulic turbine extracts potential energy from a flowing liquid such as water. In particular in such cases, the turbine is often combined with an electrical generator to convert the generated useful work into, for example, electricity.

[0005] Hydraulic turbomachinery has been widely used for over a century, but most traditional equipment is optimized for high-head applications where the available head is between 100 and 500 meters. However, today, many of the opportunities for hydroelectric power generation, especially for reduced environmental impact generation, are found in locations and situations where the head is less than 10 meters.

[0006] Historically, turbines found in low head level applications have included various propeller type turbines, such as the Archimedes screw turbine, or progressive cavity devices, such as water wheels, where a bucket pushes a volume of water from top to bottom, so that the specific volume of water moves at the same speed as the bucket. Therefore, this type of device is slow to operate and must be very large to pass large volumes of water.

[0007] Propeller turbines and their variants, such as Kaplan turbines, are capable of passing large volumes of water over the turbine blades at high speeds, but these units often must be mounted at a relatively low height relative to the water level downstream of the turbine to prevent operational problems such as cavitation.

[0008] As a result, conventional turbines designed to generate power from low head are typically very expensive, require extensive civil engineering work due to the turbine's operating requirements, often raise environmental concerns, and are often needed in remote areas far from most electricity users. Thus, there remains a need for simple, continuously operating turbines that can operate efficiently under very low head (VLH) conditions, especially below 10 meters head.

[0009] Before moving to an overview of the solution offered by the present invention, it should be noted that the prior art mentioned in this specification is not an admission or an indication that this prior art is widely known or forms part of the shared general knowledge in any country.

[0010] Additionally, the following description uses directional terms such as downward and downward, upward and upward, lower and upper, upper and lower, using the impulse turbine of the present invention arranged for rotation about a vertical axis as a reference, and furthermore, radially inward and outward, inward and outward, are also referenced to a centrally located vertical axis of rotation. Summary of the Invention

[0011] Those skilled in the art will appreciate that an impulse turbine is one in which a liquid, usually water, typically flows at a large volume and high pressure (often due to the effects of gravity) into a stationary nozzle, causing the liquid in a pressurized jet to impinge on the drive cups (also called buckets or blades) of a rotating wheel, such as a Pelton-type rotating wheel, causing rotation of the wheel to produce the required torque and work output.

[0012] In this regard, some references are made below to Pelton collector assemblies and collector plates, but those skilled in the art will understand that these are general references to radial configurations of drive cups similar in nature to those found in the rotating wheels of Pelton impulse turbines. It is important to note that the broadest aspects of the present invention are not limited to Pelton configurations in which stationary nozzles interact with rotating drive cups. Pelton configurations that may be envisioned as relevant to the present invention include rotating nozzles interacting with stationary drive cups and rotating nozzles interacting with rotating drive cups, and thus, collectively, briefly, there is relative rotation between the nozzles and the drive cups.

[0013] The present invention relates to a collector assembly having a central suction tube extending below the collector assembly, the collector assembly having a collector plate having a generally horizontal upper surface with the suction tube configured to be in fluid communication with the upper surface, a series of drive cups arranged circumferentially around the upper surface, a drive assembly around the central suction tube having a fluid inlet at its lower end in fluid communication with the lower end of the suction tube and a plurality of outlet nozzles at its upper end arranged to be tangentially arranged, and a central air tube having an upper air inlet and a lower air distribution manifold, the manifold being connected to the drive assembly. and a central air pipe having at least one venturi outlet capable of entraining air with the fluid to assist in moving the fluid upwardly from the lower end to an outlet nozzle, wherein in use a fluid jet formed at the outlet nozzle engages a drive cup to create relative rotation between the outlet nozzle and the drive cup about a vertical axis, the relative rotation capable of providing useful work, and thereafter the fluid flows from the drive cup across an upper surface of a collector plate into a draft tube, down the draft tube and into a fluid inlet of a drive assembly where the fluid is recirculated, entrained with air, to the outlet nozzle.

[0014] The recirculating hydropneumatic impulse turbine is useful in a power generation system having the recirculating hydropneumatic impulse turbine, a turbine starting system, a turbine braking system, and a generator, where the turbine starter can start rotation of the outlet nozzle or rotation of the outlet nozzle and the drive cup when the turbine is primed with fluid to generate relative rotation, after which the turbine starter can be disengaged and the braking system can stop the relative rotation, and the generator converts the useful work of the relative rotation into electrical energy.

[0015] It will be appreciated that in connection with such a power generation system, the turbine starter and braking system can be conventional components used for these same purposes and sized appropriately for the power requirements of the system, and the generator (also sized appropriately) can be of any conventional type conventionally used for similar purposes. In this regard, it will also be appreciated that it would be ideal for the power generation system to also include some type of conventional speed regulator, such as a parasitic speed regulator of the type used in standard industrial drive systems.

[0016] The recirculating hydropneumatic impulse turbine is also useful in a mechanical drive system having a recirculating hydropneumatic impulse turbine, a turbine starting system, a turbine braking system, and a mechanical drive converter, where the turbine starter can start rotation of the outlet nozzle alone or the outlet nozzle and the drive cup when the turbine is primed with fluid to generate relative rotation, after which the turbine starter can be disengaged and the braking system can stop the relative rotation, and the mechanical drive converter can convert the useful work of the relative rotation into useful mechanical work.

[0017] It will be appreciated that in the context of this mechanical drive system, the turbine starter and braking system can simply be conventional components used for these same purposes, and the mechanical drive converter can simply be any type of mechanism capable of mechanically converting the rotation of the impulse turbine into the rotation or movement of another mechanism so that the other mechanism can benefit from the work produced by the impulse turbine. In this regard, it will also be appreciated that it would be ideal for the mechanical drive system to also include some type of conventional speed regulator, such as a parasitic speed regulator of the type used in standard industrial drive systems.

[0018] In connection with the inclusion in these power generating and mechanical drive systems of a "turbine starter" capable of initiating and subsequently disengaging relative rotation, it is noted that the turbine starter serves to provide an initial energy input, and that, once relative rotation of the type described above is already present, the impulse turbine is generally in an operational mode, thus utilizing gravity as the continuous energy input (as produced in a conventional hydro-electric generator), in terms that will be functional in many of the following descriptions relating to the configuration of various aspects of the impulse turbine of the present invention.

[0019] Returning to the description of the various features of the impulse turbine, as noted above, in the broadest aspects of the invention, the fluid jet formed at the exit nozzle engages the motive cup to create relative rotation between the exit nozzle and the motive cup which is a source of useful work. It will be understood that this reference to "relative rotation" includes the manner in which the exit nozzle rotates to interact with a stationary motive cup, and the manner in which the exit nozzle rotates to rotate the motive cup in the opposite direction.

[0020] It should be noted that in all embodiments, the collector plates of the collector assemblies have generally horizontal upper surfaces, so that whatever element rotates does so about a generally vertical axis, in contrast to conventional Pelton impulse turbines, where rotation of a Pelton wheel is typically produced about a horizontal axis.

[0021] In such cases in particular, a preferred mode of relative rotation would be for the outlet nozzle to rotate and interact with a stationary drive cup. In one mode, this is achieved in that the collector assembly has a stationary upper drive plate spaced above the collector plate, and the drive cup is disposed around the periphery of the drive plate such that the drive cup is integral with or fixed to the underside of the drive plate and extends downwardly towards the collector plate just above but not in contact with the collector plate.

[0022] The drive cup may be formed integrally with the drive plate so that the drive plate and drive cup form a unitary element, or the drive cup may be removably or permanently attached to the drive plate by any suitable means such as bolts or by welding.

[0023] In this embodiment, the collector plate is ideally a floating plate, where the collector plate is mounted such as on bearings to rotate, but is not driven to rotate. This floating feature helps to dampen any energy remaining in the fluid moving out of the nozzle and across the upper surface of the collector plate after it engages the drive cup. This minimizes turbulence of the fluid and subsequent interaction of the fluid with other drive cups, such as drive cups adjacent or opposite the drive cup with which the fluid immediately interacts as it exits the nozzle.

[0024] Also in this aspect, the outlet nozzle of the drive assembly is preferably located outside the periphery of the collector plate and rotates around the periphery of the collector plate, the drive plate is configured to extend beyond the periphery of the collector plate, and the drive cup also extends beyond the periphery of the collector plate so that fluid exiting the rotating nozzle can directly interact with the drive cup. As outlined above, fluid exits the drive cup onto the upper surface of the floating collector plate, across the upper surface and down the central draft tube.

[0025] In this embodiment, the central draft tube is preferably formed integrally with the collector assembly or at least with the collector plate and extends vertically below the collector plate such that the upper surface and the draft tube together have a funnel-like configuration and the draft tube is in fluid communication with the generally horizontal upper surface of the collector plate. Ideally, fluid on the upper surface will flow by gravity from the upper surface to the center of the collector plate and down the draft tube. Thus, the expression that the upper surface of the collector plate is "generally horizontal" refers to the overall aspect of the upper surface that allows for the presence of at least a slight inward tilt that directs the flow of fluid so that the fluid can flow from its surface towards the central draft tube and down the central draft tube.

[0026] The central draft tube may be a diverging, converging or constant diameter tube, but the preferred embodiment is a constant diameter tube, which has a transition region (shoulder region) between the upper surface of the collector plate and the upper portion of the draft tube.

[0027] Furthermore, since the overall configuration of the present invention is such that the recirculating fluid comes from below the collector plate (in the form of a fluid jet engaging the drive cup) and travels across the upper surface of the collector plate after engaging the drive cup, the drive cup preferably has at least a fluid jet engagement portion that extends outwardly beyond the periphery of the collector plate and is integral with a fluid return portion that returns the fluid to the upper surface of the collector plate. In this embodiment, the outlet nozzle is positioned tangentially to and outwardly of the periphery of the collector plate so that the fluid jet can first engage the fluid jet engagement portion of the drive cup and the fluid is then transported across the drive cup via the fluid return portion to the upper surface of the collector plate.

[0028] In a preferred embodiment, the drive cup is configured such that a high velocity fluid jet impacts the fluid jet engagement portion of the drive cup and deflects the fluid jet 160°-170° such that the direction of the water changes to follow the contour of the drive cup. The impact energy of the water applies a torque to the drive cup which causes relative rotation between the drive cup and the outlet nozzle, which in a preferred embodiment rotates the outlet nozzle and drive assembly. As described above, the fluid changes direction and exits at a low velocity out the side of the drive cup onto the collector plate.

[0029] In relation to the drive assembly of the impulse turbine of the present invention, the drive assembly is preferably disposed about the periphery of the central draft tube, generally below the collector plate, and configured with one or more fluid inlets at a lower end of the drive assembly in fluid communication with the lower end of the draft tube through which fluid exits the draft tube, and with a plurality of tangentially disposed outlet nozzles at an upper end of the drive assembly.

[0030] In particular in such cases, the drive assembly may be, for example, a cylindrical drum rotatable about its central vertical axis, with a side wall having a smooth interior surface that is angled away from the vertical axis of the drum, across which fluid from a lower fluid inlet of the drum flows to exit through a plurality of outlet nozzles arranged circumferentially around the upper end of the drum. In this embodiment, the lower fluid inlet of the drum may be configured to direct fluid flow from the lower fluid inlet up the interior of the side wall of the drum, preferably in a direction angled tangentially to the side wall of the drum.

[0031] Alternatively, the sidewall of the drum may be configured with open flow channels such as corrugations or grooves, the sidewall and therefore the corrugations or grooves also preferably being inclined from the vertical axis of the drum and also tangentially to the sidewall of the drum, each channel aligned with a particular outlet nozzle to direct fluid flow from a lower fluid inlet of the drum to an upper outlet nozzle. In this aspect, the fluid inlet of the drum may also have a lower fluid distribution manifold that distributes and directs the fluid flow from the fluid inlet to the lower ends of each corrugation or groove.

[0032] In yet another embodiment, the open channels can be replaced with closed channels that are integrally formed with or rigidly secured to the inside of the drum sidewall and have the same vertical and tangential slopes as described above.

[0033] Furthermore, the drive assembly need not have a solid-walled drum, in which case the flow passages are provided in the form of a plurality of tubes, essentially forming a cage of tubes around a central draft tube, each tube aligned with a particular upper outlet nozzle, directing fluid flow from a lower fluid distribution manifold which distributes fluid from the central draft tube to the lower end of each tube and providing the directed fluid flow to a respective upper outlet nozzle. Moreover, such tubes are also preferably configured to be inclined vertically from the vertical axis of the drive assembly (and therefore of the collector assembly) and also inclined tangentially from the periphery of the collector plate in a similar manner as outlined above, such that a generally helical array of tubes forms a cage-like drive assembly.

[0034] In these embodiments, although not required, the flow of fluid from the lower end of the drive assembly to the upper outlet nozzle of the drive assembly is ideally generally spiraling upwards, with a preferred double slope, one sloped away from the vertical axis of the collector assembly and one sloped tangentially to the periphery of the collector plate, as opposed to embodiments where there is no such slope, aiding in the movement of fluid upwards from the lower end of the drive assembly to the outlet nozzle, where a fluid jet formed engages the drive cup to create relative rotation between the drive cup and the outlet nozzle about the vertical axis as described above, which rotation can provide useful work.

[0035] Returning to the description of the collector assembly including the collector plate and the central draft tube, as noted above, the collector plate is configured such that it has a generally horizontal upper surface with a central draft tube extending vertically below the upper surface and the draft tube in fluid communication with the upper surface, as fluid flows from the drive cup across the upper surface of the collector plate to the draft tube and down the draft tube, where it enters the fluid inlet of the drive assembly, entrains air, and is recirculated back up to the outlet nozzle.

[0036] In particular in such a case, the central draft pipe has a central air pipe with an upper air inlet and a lower air distribution manifold. Preferably, the lower air distribution manifold has at least one venturi outlet that can entrain air with the fluid to help move the fluid upward from the lower end of the drive assembly to the upper outlet nozzle. It will be understood that there are several variations available for the drive assembly of the impulse turbine, particularly with respect to the presence or absence of fluid flow structures (i.e. open or closed flow paths that can be corrugated, grooved, integral or stand-alone tubes), and that the lower air distribution manifold itself can have many variations as required. Ideally, the fluid inlet of the drive assembly is paired with a lower air distribution manifold, and although there are many structures for the preferred guidance of the fluid flowing upward in the drive assembly, in each such structure, the lower air distribution manifold has a venturi outlet for each outlet nozzle that can entrain air with the fluid to help move the fluid upward from the lower end of the drive assembly to the outlet nozzle.

[0037] With regard to the flow of air into and through the impulse turbine of the present invention, air is first drawn from above the collector plate through an upper air inlet, which may take the form of a number of suitably positioned inlet openings, into the central air pipe, where air entrained with the circulating fluid (emerging from an outlet nozzle and flowing across the upper surface of the collector plate) is exhausted. Air is also preferably drawn from an external air valve above the collector assembly, which allows air to be drawn from the atmosphere. In this regard, such an external air valve may ideally be incorporated into an air relief valve, and is therefore preferably a passive vent that allows internal and external air pressures to be equalized, and is ideally designed to minimize fluid loss from the system.

[0038] In a preferred embodiment, the central air pipe has a plurality of inlet openings located near the level of the collector plate or just below the level of the collector plate, such that air entering the central air pipe travels downward from these openings into the lower air distribution manifold. In this regard, in one embodiment, the lower air distribution manifold can have a series of radial ports (one for each venturi outlet), each in fluid communication with a respective venturi tube. Such venturi tubes ideally extend from the central air pipe wall to a location associated with or adjacent to an open flow passage, such as a corrugation or groove, or to a location within a closed flow passage, such as a tube, with their outlets facing downstream relative to the flow, thereby forming a venturi, whereby air passing through the venturi is entrained with the passing fluid.

[0039] After leaving these venturi outlets, the air is compressed within the fluid by centrifugal forces in the flow passages, and after peak compression, the air expands as it leaves the flow passages, thereby pressurizing the fluid and increasing and regulating the velocity of the fluid moving up the flow passages.

[0040] Since the drive assembly is typically supported by bearings at both ends of its shaft, rotation of the drive assembly is subject to small mechanical friction losses. It will further be appreciated that the counter-rotating fluid contained within the flow passage of the drive assembly, circulating at a maximum radius relative to the shaft, acts as a compressed fluid mass. Although this fluid circulation is also subject to friction losses, the counter-rotation of the fluid compared to the rotation of the drive assembly negates the normal downward gravitational force applied to the fluid flowing upward within the drive assembly to the extent that there is little resistance to the upward movement of the fluid.

[0041] Furthermore, as the fluid moves away from the peak compression point, the air entrained within the fluid begins to expand, ejecting the fluid from the exit nozzle at a faster velocity than the unentrained fluid. In this manner, this "no longer compressible" fluid emerges from the exit nozzle and impacts the drive cup of the collector assembly, transferring energy (thrust) from the fluid to the rotary drive assembly, thus rotary driving the entire drive assembly.

[0042] Under very low head (VLH) conditions, such as operation at less than 10 meters of head, the impulse turbine of the present invention ideally operates at less than 5 meters of head (in terms of preferred acceleration rate), and ideally in the range of 1-3 meters of head. In this regard, the impulse turbine of the present invention does not have significant energy available from falling fluid beyond about 5 meters, so ideally the turbine of this configuration would have a head in the range of 1-3 meters. Also, in the present configuration, the longer the fluid falls, the further the fluid will have to be pumped back up to the collector assembly, but in the range of 1-3 meters efficiency is maximized without sacrificing additional fluid head. [Brief description of the drawings]

[0043] Having briefly described the general concepts encompassed by the present invention, the following describes some preferred embodiments of the recirculating hydro-pneumatic impulse turbine of the present invention, with the understanding that the following description is not intended to limit the generality of the above description. Regarding the drawings [Figure 1a-1d] FIG. 1a is an isometric top view of an impulse turbine according to a first embodiment of the present invention; FIG. 1b is an isometric bottom view of the first embodiment mounted on a support frame; FIG. 1c is a schematic isometric top view of the first embodiment with the drive plate cover removed to show the drive cup and collector plate; and FIG. 1d is another isometric top view of the first embodiment with the drive plate cover and drive cup removed to show the outlet nozzle. [Figure 2a-2b]2a and 2b are schematic isometric views of a second and third embodiment of an impulse turbine. [Diagram 3-4] 3 and 4 are cross-sectional views of the impulse turbine according to the first embodiment as seen from above and from the side, respectively. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing the lower end of the drive assembly of the impulse turbine of the first embodiment from below for easier understanding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] 1a-1d and 3-5 show a recirculating hydropneumatic impulse turbine according to a first preferred embodiment of the present invention. Before referring to certain parts in the figures using reference numbers, in this first embodiment, the impulse turbine of this embodiment has a relative rotation between its outlet nozzle and the drive cup, with the drive cup being stationary and the outlet nozzle rotating. Furthermore, this first embodiment has a drive assembly with flow passages in the form of tubes, generally a plurality of tubes arranged in the form of a cage of tubes around a central draft tube of the collector assembly. The second and third embodiments of the impulse turbine shown in Figs. 2a and 2b differ from the first embodiment in the type of flow passages incorporated in the drive assembly.

[0045] 1a-1d, an exemplary impulse turbine 10 includes a collector assembly, generally designated 14, which in this embodiment includes a drive plate 12 disposed adjacent to but spaced above a collector plate 15 having a central draft tube 16 extending therebelow. The collector plate 15 has a generally horizontal upper surface 18 with the draft tube 16 configured to be in fluid communication with the upper surface 18. From FIG. 1c it can be seen that there are a series of circumferentially arranged drive cups 20 which are shown diagrammatically in FIG. 1c but typically integral with or secured to the underside of the drive plate 12, which is generally shown removed in FIGS. 1c and 1d. The typical relationship of the drive cups 20 to the drive plate 12 and collector plate 15 can be seen from FIG. 3. The drive cups 20 are described in more detail below.

[0046] The impulse turbine 10 also includes a drive assembly 22 disposed about the draft tube 16, the drive assembly 22 having a fluid inlet 24 (see FIGS. 3-5) at a lower end thereof in fluid communication with the lower end of the draft tube 16, and a plurality of tangentially arranged outlet nozzles 26 configured at an upper end thereof.

[0047] The impulse turbine also has a central air pipe 30 having an upper air inlet in the form of a plurality of inlet openings 80 and a lower air distribution manifold 34 (see Figures 3-5) having at least one venturi outlet 36 (see Figures 3-5) capable of entraining air into the fluid to assist in moving the fluid upwardly from the lower end of the drive assembly 22 to the outlet nozzle 26 of the drive assembly 22.

[0048] As described more generally above, during use of the impulse turbine 10, a fluid jet formed at the outlet nozzle 26 engages the drive cup 20 to create relative rotation between the outlet nozzle 26 and the drive cup 20 about the vertical axis A, which rotation can provide useful work, and thereafter, fluid flows from the drive cup 20, across the upper surface 18 of the collector plate 15, into the draft tube 16, down the draft tube 16 and into the fluid inlet 24 of the drive assembly 22 where the fluid, along with air, is recirculated back to the outlet nozzle 26.

[0049] The impulse turbine 10 can be used in a power generation system or a mechanical drive system, in either case utilizing a turbine starter system, a turbine braking system and a generator or a mechanical drive converter. These systems and additional equipment are not shown in the overall figures, but preferred locations of the equipment are illustrated generally at X and Y in Fig. 1b (and also at X and Y in the second and third embodiments shown in Figs. 2a and 2b), which shows the impulse turbine 10 according to the first embodiment mounted on a suitable support cage 40 ready for installation.

[0050] In this regard, as described above, the turbine starter can initiate rotation of the outlet nozzle 26 of the drive assembly 22 to prime the drive assembly 22 with fluid, creating relative rotation between the outlet nozzle 26 and the drive cup 20, after which gravity provides a continued energy input (as in a conventional hydroelectric generator) and the turbine starter is subsequently disengaged. A braking system can stop that relative rotation if necessary. The generator, in use, converts the useful work of the relative rotation between the drive cup 20 and the outlet nozzle 26 into electrical energy, and the mechanical drive converter, in use, converts the useful work of the relative rotation between the drive cup 20 and the outlet nozzle 26 into useful mechanical work.

[0051] 1c and 1d, with some parts removed for ease of reference, a fluid jet (not shown) formed at an outlet nozzle 26 (best seen in FIG. 1d) of the impulse turbine 10 engages a drive cup 20 (best seen in FIG. 1c) to generate relative rotation between the drive plate 12 of the collector assembly 14 and the outlet nozzle 26 of the drive assembly 22, which, as discussed above, is a source of useful work. In this embodiment, the outlet nozzle 26 of the drive assembly 22, and therefore the drive assembly 22 itself, rotates and interacts with the drive cup 20 of the stationary drive plate 12.

[0052] This relative rotation is about a vertical axis A. This is in contrast to conventional Pelton impulse turbines, where the rotation of the Pelton wheel is typically about a horizontal axis.

[0053] The collector plate 15 is a floating plate, mounted for rotation on bearings (not shown), but is unconstrained and does not normally rotate, or at least not at speeds approaching the speed of the drive assembly. As mentioned above, the floating feature helps to dampen any energy remaining in the fluid moving across the upper surface 18 of the collector plate 15 as it exits the outlet nozzle 26 after it engages the drive cup 20.

[0054] The outlet nozzles 26 are located outside the periphery 52 of the collector plate 15 (see FIG. 3) and therefore rotate around the periphery 15 of the collector plate, and the drive plate 12 is configured to extend beyond the periphery of the collector plate, with the drive cups 20 also extending beyond the periphery of the collector plate 15 so that fluid exiting the rotating nozzles 26 can directly interact with the drive cups 20. The fluid exits the drive cups 20 onto the upper surface 18 of the floating collector plate 15 and flows across the upper surface towards and down the central draft tube.

[0055] The draft tube 16 and the elements constituting the draft tube 16 in this embodiment will now be described with particular reference to Figures 3 to 5. In this embodiment, the two parts 15a and 15b of the draft tube 16 are integrally formed with the collector plate 15 and extend vertically below the collector plate, with the generally horizontal upper surface 18 of the collector plate 15 and the draft tube 16 together having a funnel-shaped upper part 15a at the inlet 44 to the draft tube 16, with the draft tube 16 in fluid communication with the upper surface 18. Fluid on the upper surface 18 will therefore flow by gravity from the upper surface 18 to the centre of the collector plate 15, down the upper part 15a through the inlet 44 and through the inside of the middle part 15b of the draft tube 16. As can be seen from Figure 4, the upper surface 18 therefore has a slight inwardly directed inclination to orient the fluid to flow from its upper surface 18 towards the draft tube 16 and down the draft tube.

[0056] The central draft tube 16 in this embodiment is a constant diameter tube with an inlet 44 having an upper portion 15a (shoulder region) between the upper surface 18 of the collector plate 15 and an intermediate portion 15b of the draft tube 16.

[0057] It will also be seen from Figures 3 and 4 that the outlet nozzle 26 is integral with the nozzle plate 90, which extends below the collector plate 15 and down through its lower parts 90a, 90b outside the upper and middle parts 15a, 15b of the draft tube 16 to fit between the nozzle plate 90, 90a, 90b and the collector plate 15, 15a, 15b to allow relative rotation between them. In this case, it is noted that in this embodiment in particular, a gap 102 is provided between the collector plate 15 and the nozzle plate 90, with an inlet at the location indicated by reference number 100, which allows the movement of fluid that unintentionally flows outwards past the outlet nozzle 26 down through the gap 102 and back to the draft tube 16.

[0058] The collector plate 15 has its upper portion 15a and its intermediate portion 15b and generally floats as described above, while the nozzle plate 90 has its lower portions 90a, 90b and rotates during operation due to the forced rotation of the outlet nozzle 26. In this regard, in this embodiment, the lowermost portion 90b of the nozzle plate 90 has its lower end extending below the intermediate portion 15b of the collector plate 15 and descends into the inlet 24 of the drive assembly 22 and its tube 70, thereby forming the lower element of the draft tube 16.

[0059] It will be appreciated that as the drive cup 20 and drive plate 12 are both stationary and the outlet nozzle 26 and nozzle plate 90 rotate in this manner during use, the upstanding side walls 96 of the nozzle plate 90 also rotate. Note that suitable sealing engagements are provided between the corner flanges 94 of the drive plate 12 to permit relative rotation between the drive plate 12 and the side walls 96 of the nozzle plate 90.

[0060] The drive cup 20 in this embodiment is attached to the underside of the drive plate 12 by any suitable means, such as bolts or welding, and in this embodiment has a mounting flange 46 for securing the drive cup 20 to the drive plate 12. Because the recirculating fluid comes from below the collector plate 15, the drive cup 20 has a fluid jet engagement portion 50 (as seen in Figures 1c, 3 and 4) that extends outwardly beyond the periphery 52 of the collector plate 15 and is integral with a fluid return portion 54 that returns the fluid to the upper surface 18 of the collector plate 15. In this aspect, the outlet nozzle 26 is positioned tangentially below and outwardly of the periphery 52 of the collector plate 15 so that a fluid jet (not shown) can first engage the fluid jet engagement portion 50 of the stationary drive cup 20 and the fluid is then transferred across the engagement portion 50 via the fluid return portion 54 to the upper surface 18 of the collector plate 15.

[0061] In this embodiment, the drive cup 20 is configured such that a high velocity fluid jet impacts the fluid jet engaging portion 50 of the drive cup 20 and the fluid jet is deflected 160°-170° such that the direction of the water changes to follow the contour of the drive cup 54. The impact energy of the water applies a torque to the drive cup 20, causing relative rotation between the drive cup 20 and the outlet nozzle 26 by rotating the drive assembly 22 and therefore the outlet nozzle 26. The fluid then changes direction and exits the drive cup 20 at a low velocity onto the upper surface 18 of the collector plate 15.

[0062] With respect to the drive assembly 22 of the impulse turbine of the present invention, the drive assembly 22 is preferably disposed generally about the central draft tube 16, generally below the upper surface 18 of the collector plate 15, and configured with a fluid inlet 24 at a lower end of the drive assembly 22 in fluid communication with the lower end of the draft tube 16, and a plurality of tangentially disposed outlet nozzles 26 at an upper end of the drive assembly.

[0063] As mentioned above, and will now be described in relation to the embodiments illustrated in Figures 1a-1d, 3 and 4 (first embodiment), and then in Figures 2a (second embodiment) and 2b (third embodiment), the drive assembly 22 can be a cylindrical drum 60, for example in Figure 2a, rotatable about its central vertical axis A, with a smooth interior (not shown) of a sidewall 62 that is angled away from the vertical axis A of the drum 60, across which fluid from a lower fluid inlet of the drum flows to exit through a plurality of outlet nozzles 26 (shown in the previous figures) arranged circumferentially around the upper end of the drum 60. In this embodiment, the lower fluid inlet of the drum could have one or more lower nozzles (not shown) configured to direct fluid flow from the lower fluid inlet up the interior of the sidewall of the drum 60 in a direction angled tangentially to the sidewall of the drum.

[0064] 2b, a cylindrical drum 66 may be formed with flow channels 68 in a side wall 64, each aligned with a particular outlet nozzle 26 (shown in the previous figure), to direct fluid flow from a lower fluid inlet of the drum 66 to the upper outlet nozzle 26. In this embodiment, the drum fluid inlet may also have a lower fluid distribution manifold (not shown) that distributes and directs fluid flow from the fluid inlet to the lower ends of each of the flow channels 68.

[0065] It should be noted that in the first embodiment shown in Figures 1a-1d, 3 and 4, the flow passages directing such fluid flow do not necessarily have solid-walled drums, but are closed flow passages in the form of tubes 70, which in this case essentially form a cage of tubes around the central suction tube 16 of the collector plate 15, each tube 70 being aligned with a particular upper outlet nozzle 26 to direct the fluid flow from the lower fluid inlet 24 to the upper outlet nozzle 26. In this embodiment, the fluid inlet of such an assembly has a lower fluid distribution manifold which distributes the fluid from the fluid inlet 24 to the lower ends 72 of each tube 70 (two such lower ends 72 in the reference in Figure 4) and again directs the fluid flow to the respective upper outlet nozzle 26.

[0066] Moreover, such tubes 70 are configured to be inclined vertically from the vertical axis A of the drive assembly 22 (and therefore of the collector plate 15) and also inclined tangentially in the same manner as outlined above, thereby forming a generally helical array of tubes forming the cage-like drive assembly 22 of the first embodiment.

[0067] It will thus be apparent that the fluid flow in all embodiments from the lower inlet 24 to the upper outlet nozzle 26 of the drive assembly 22 is generally spiraling upwardly due to the double slopes, one slope away from the vertical axis of the collector plate 15 and one slope tangential to the outer circumferential edge 52 of the collector plate 15. These double slopes assist the fluid to travel upwardly from the lower end 72 of the tube 70 towards the outlet nozzle 26 where the fluid jet formed engages the drive cup 20 creating the relative rotation discussed above.

[0068] 3-5, the central draft tube 16 has a central air tube 30 therein having an upper air inlet in the form of a plurality of openings 80 and a lower air distribution manifold 34. The lower air distribution manifold 34 has a plurality of venturi outlets 36 through which air can be entrained into the fluid to assist in moving the fluid upwardly from the lower end of the drive assembly 22 to the outlet nozzle 26. In this embodiment, the lower air distribution manifold 34 has a respective venturi outlet 36 for each tube 70 of the drive assembly 22.

[0069] 4, at the upper end of the central air tube 30 is a hollow axle shaft through which an actuation rod extends from a speed control mechanism (not shown) to the central air tube 30. The actuation rod is connected to an internal air control piston 104 which controls the amount of air entering the central air tube 30 by opening and closing the inlet opening 80, thereby effectively controlling air flow by effectively increasing or decreasing the area available for air flow into the central air tube 30 as needed to increase or decrease the rotational speed of the drive assembly 22.

[0070] With regard to the flow of air entering and passing through the impulse turbine 10, air is drawn from just above the upper surface 18 of the collector plates 15 down through openings 80 (see FIG. 1c) located at a level just below the level of the collector plates 15 into the central air tube 30, allowing air entrained with the circulating fluid at the collector plates to escape the circulating fluid. This embodiment also allows the inside and outside air pressures to ideally be equalized, but could also provide an air relief valve, which is a passive vent that minimizes fluid loss from the system.

[0071] Air entering the air tubes 30 travels downward through openings 80 into a lower air distribution manifold 34 which has a series of radial ports 82 (one for each venturi outlet) with attached venturi tubes 36 extending from a central air tube wall 84 to a position within each tube 70, with the outlet of each tube facing downstream relative to the flow, thereby forming a venturi which entrains air passing therethrough with the fluid as it enters the tubes 70.

[0072] After exiting the venturi outlet 36, the air is compressed within the fluid in tube 70 and expands as it exits the venturi outlet 36 after peak compression, thereby pressurizing the fluid and increasing and regulating the velocity of the fluid moving up tube 70. As the fluid moves away from the point of peak compression, any air entrained within the fluid begins to expand rapidly, ejecting the fluid from the exit nozzle 26 at a much greater velocity than the unentrained fluid.

[0073] In this embodiment, this "no longer compressible" fluid emerges from outlet nozzle 26 and impacts stationary drive cups 50 at the periphery of drive plate 12, transferring energy (as thrust) from the fluid to rotary drive tube assembly 22, thus driving the entire drive tube assembly 22 in continuous rotation and rotating drive shaft 100 to produce useful work.

[0074] Finally, it will be understood that variations and modifications may be made to the structures described herein and that such variations and modifications are within the scope of the present invention.

Claims

1. 1. A recirculating hydropneumatic impulse turbine, comprising: a collector assembly having a central draft tube extending below the collector assembly, the collector assembly having a collector plate having a generally horizontal upper surface, the draft tube being configured to be in fluid communication with the upper surface, and a series of drive cups circumferentially disposed about the upper surface; a drive assembly around the central draft tube, the drive assembly having at a lower end thereof a fluid inlet in fluid communication with the lower end of the draft tube, and at an upper end thereof a plurality of outlet nozzles configured to be tangentially arranged; a central air pipe having an upper air inlet and a lower air distribution manifold having at least one venturi outlet capable of entraining air into the fluid to assist in moving the fluid upwardly from the lower end of the drive assembly to the outlet nozzle; It is equipped with an impulse turbine wherein, in use, a fluid jet formed at the outlet nozzle engages a drive cup to create relative rotation between the outlet nozzle and the drive cup about a vertical axis, said rotation capable of providing useful work, and wherein fluid then flows from the drive cup, across the upper surface of the collector plate, into the draft tube, down the draft tube, and into the fluid inlet of the drive assembly, whereby the fluid, entrained with air, is recirculated to the outlet nozzle.

2. 2. The impulse turbine of claim 1, wherein the outlet nozzle rotates and interacts with the stationary drive cup, or the outlet nozzle rotates and the drive cup also rotates, but in an opposite direction.

3. 3. An impulse turbine according to claim 1 or 2, wherein the outlet nozzle rotates and interacts with a stationary drive cup.

4. 4. The impulse turbine of claim 3, wherein the collector assembly includes a stationary upper drive plate spaced above the collector plate, and the drive cups are integral with or secured to a lower surface of the drive plate and are positioned around a periphery of the drive plate such that the drive cups extend downwardly toward the collector plate just above but without contacting the collector plate.

5. 5. The impulse turbine of claim 4, wherein the drive cup is integrally formed with the drive plate or the drive cup is removably or permanently attached to the drive plate such that the drive plate and drive cup form a single element.

6. 5. The impulse turbine of claim 4, wherein the collector plate is a floating plate mounted for rotation.

7. 5. The impulse turbine of claim 4, wherein the outlet nozzle is located outside the periphery of the collector plate and rotates around the periphery of the collector plate.

8. 8. The impulse turbine of claim 7, wherein the drive plate extends beyond the peripheral edge of the collector plate and the drive cup also extends beyond the peripheral edge of the collector plate.

9. 3. An impulse turbine according to claim 1, wherein the draft tube is integrally formed with the collector plate and extends vertically below the collector plate such that the upper surface and the draft tube together have a funnel-shaped configuration and the draft tube is in fluid communication with the upper surface.

10. 10. The impulse turbine of claim 9, wherein the draft tube is a constant diameter tube having a transition region between an upper surface of the collector plate and an upper portion of the draft tube.

11. 10. An impulse turbine according to claim 9, wherein the two sections of the central draft tube, an upper section and an intermediate section, are integrally formed with the collector plate and extend vertically below the collector plate such that the generally horizontal upper surface of the collector plate and the draft tube together have a funnel-shaped configuration.

12. 12. The impulse turbine of claim 11, wherein the inlet of the draft tube has an upper portion that is a shoulder region between the upper surface of the collector plate and the intermediate portion of the draft tube.

13. 10. The impulse turbine according to claim 9, wherein the outlet nozzle is integral with a nozzle plate, the nozzle plate extending below the collector plate and descending outside the upper and middle portions of the draft tube to fit within the nozzle plate to an extent that relative rotation is possible between the nozzle plate and the collector plate.

14. 14. An impulse turbine as claimed in claim 13, wherein said collector plate and said upper and intermediate portions of said draft tube are generally floating, and said nozzle plate extends with its lower end below said intermediate portion of said draft tube and into said inlet of said drive assembly, and is rotated in operation by forced rotation of said outlet nozzle.

15. 14. The impulse turbine of claim 13, wherein the nozzle plate has upstanding side walls with sealing engagements between corner flanges of the drive plate to permit relative rotation between the drive plate and the nozzle plate side walls.

16. 3. An impulse turbine according to claim 1, wherein the outlet nozzle is arranged tangentially to the periphery of the collector plate and outside the periphery of the collector plate.

17. 3. The impulse turbine of claim 1, wherein the drive cup has a fluid jet engaging portion that extends outwardly beyond the periphery of the collector plate and is integral with a fluid return portion that returns fluid to the upper surface of the collector plate.

18. 3. The impulse turbine of claim 1, wherein the drive cup is configured such that a fluid jet impinges on a fluid jet engaging portion of the drive cup and deflects the fluid jet by 160° to 170° so that the direction of the water changes to follow the contour of the drive cup.

19. 3. The impulse turbine of claim 1, wherein the drive assembly is disposed about the draft tube below an upper surface of the collector plate, and wherein a fluid inlet at a lower end of the drive assembly is in fluid communication with a plurality of outlet nozzles disposed tangentially at the lower end of the draft tube and at an upper end of the drive assembly.

20. 3. The impulse turbine of claim 1, wherein the drive assembly is a cylindrical drum having a single peripheral sidewall with an inner surface, the drum rotatable about its central vertical axis, the inner surface being a smooth surface across which fluid from a lower fluid inlet of the drum travels and exits through an outlet nozzle around the upper end of the drum.

21. 21. The impulse turbine of claim 20, wherein the inner surface of the drum defines channels, each channel aligned with a particular outlet nozzle, for directing fluid flow from the lower fluid inlet of the drum to the upper outlet nozzle.

22. 22. The impulse turbine of claim 21, wherein the drive assembly includes a lower fluid distribution manifold that distributes fluid from the fluid inlet to lower ends of respective flow paths to direct fluid flow.

23. 23. An impulse turbine according to claim 22, wherein the flowpath is a tube integrally formed with or rigidly fixed to the interior of the drum.

24. 3. The impulse turbine of claim 1 or 2, wherein the drive assembly is a cage of tubes around the central draft pipe, each tube in the cage of tubes being aligned with a particular upper outlet nozzle to direct fluid flow from a lower fluid inlet to an upper outlet nozzle.

25. 25. The impulse turbine of claim 24, wherein the drive assembly has a fluid inlet at a lower end thereof with a lower fluid distribution manifold that distributes fluid from the fluid inlet to the lower ends of each tube in the cage of tubes.

26. 26. An impulse turbine according to claim 25, wherein each tube in the cage of tubes is arranged to be inclined vertically from a vertical axis of the drive assembly and tangentially to a periphery of the collector plate, whereby a generally helical array of tubes forms a cage-like drive assembly.

27. 25. The impulse turbine of claim 24, wherein fluid flow from the lower inlet to the upper outlet nozzle of the drive assembly is upward and generally helical.

28. 3. The impulse turbine of claim 1, wherein the central draft pipe includes a central air pipe having an upper air inlet and a lower air distribution manifold, the lower air distribution manifold including at least one venturi tube capable of entraining air into the fluid to assist in moving the fluid upwardly from the lower end of the drive assembly to the upper outlet nozzle.

29. 30. The impulse turbine of claim 28, wherein the upper air inlet is in communication with an air relief valve, the air relief valve being a passive vent that allows internal and external air pressures to equalize.

30. 29. The impulse turbine of claim 28, wherein the central air pipe has a plurality of inlet openings located below the collector plate such that air entering the central air pipe travels downwardly from those openings to a lower air distribution manifold which includes a series of radial ports corresponding to respective venturi tubes extending from the central air pipe wall to a location in communication with, adjacent to, or within the flowpath, the outlets of the venturi tubes facing downstream relative to the flow path to form a venturi through which the passing fluid and entrained air pass.

31. 3. An impulse turbine according to claim 1 or 2, sized to operate at a head of water of less than 5m, preferably in the range of 1 to 3m.

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