Pump assembly

Abstract

A pump assembly is disclosed. The pump assembly has an impeller chamber and an impeller configured to rotate in the impeller chamber about a rotational axis to transfer fluid through the impeller chamber. The impeller has a central hub and at least one impeller blade. The at least one impeller blade extends radially outward from an outer surface of the central hub. A guide device located upstream of the impeller is configured to guide fish towards an inner radial region of the impeller chamber outside the central hub. The guide device has a guide grating configured to permit fluid to pass therethrough. Also disclosed is an input chamber for a pump assembly.

Description

[0001] PUMP ASSEMBLY

[0002] Field of the invention

[0003] The present invention relates to pumping apparatus, such as a pump assembly, and more particularly to pumps and assemblies designed to be less damaging to fish, such as so-called LDP pumps and assemblies.

[0004] Background

[0005] Water management systems, including hydropower facilities, irrigation systems, and water treatment plants, often use pumps to transfer water between reservoirs or other systems. Conventional pump designs can pose risks to aquatic life, particularly fish. During the pumping process, fish that are drawn into the pump inlet can be injured by impellers, for example.

[0006] Land Drainage pump stations are typically low lift and require pumps to lift the water over a range of heads from say 0.5m to 6.0m. The types of pumps which fulfil these requirements are either Archimedean screw pumps or axial-flow pumps. In the UK the axial-flow is the preferred choice whereas in other countries the Archimedean screw pump is the norm. In many of the UK land drainage pump stations the discharge side is tidal or is influenced by tidal conditions further downstream as a result there is a large variation in head. If Archimedean screw pumps were employed the station would have to be designed so that the discharge or “pour point” was always above the max discharge water level irrespective of the downstream water level. This would result in excessive amounts of energy being wasted every time the pump station operated, except for the most extreme design case which may never occur in the life of the pump station.

[0007] Axial-flow pumps by contrast are simple in construction and relatively easy to install and does provide the most cost-effective solution for land drainage applications. The draw back as regards fish friendliness is its construction which consists of an impeller which will have 3 or 4 blades which sits in front of the diffuser or guide-vane casing which will have between 5 and 7 guide-vanes which turn the flow into an axial direction. Other numbers ofvanes and other numbers of blades may be used in axial flow pumps.

[0008] Higher head pumping stations or specially designed LDP pumping stations may also comprise mixed or radial flow pumps with 1 to 5 impeller vanes with volutes or diffusers with 3 to 9 guide-vanes.

[0009] It is an aim of the present invention to provide an improved pump assembly.

[0010] Summary of the invention

[0011] Aspects of the invention are as set out in the independent claims and optional features are set out in the dependent claims. Aspects of the invention may be provided in conjunction with each other and features of one aspect may be applied to other aspects.

[0012] Embodiments of the disclosure aim to provide a pump assembly comprising any or all of the following features; an impeller chamber; an impeller configured to rotate in the impeller chamber about a rotational axis to transfer fluid through the impeller chamber, wherein the impeller comprises: a central hub; and at least one impeller blade extending radially outward from an outer surface of the central hub; and a guide device located upstream of the impeller and configured to guide fish towards an inner radial region of the impeller chamber outside the central hub, wherein the guide device comprises a guide grating configured to permit fluid to pass therethrough.

[0013] Embodiments of the disclosure may provide axial flow pumps, or mixed or radial flow pumps, and such pump assemblies for use with axial flow pumps, or mixed or radial flow pumps.

[0014] Embodiments of the disclosure may also provide a guide device for a pump assembly configured to be assembled to the intake of an impeller chamber, the impeller chamber comprising an impeller configured to rotate in the impeller chamber about a rotational axis to transfer fluid through the impeller chamber, wherein the impeller comprises: a central hub; and at least one impeller blade extending radially outward from an outer surface of the central hub; and the guide device, when assembled to the intake of the impellerchamber, is located upstream of the impeller and configured to guide fish towards an inner radial region of the impeller chamber outside the central hub, wherein the guide device comprises a guide grating configured to permit fluid to pass therethrough.

[0015] The guide device can be made and sold separately from the pump assembly.

[0016] The guide device may be configured to guide fish towards a region of the impeller which has a better survival rate for the fish. For example, this may comprise a region of the impeller in which the blades have a slower linear speed. Generally, this is a region nearer to a central hub of the impeller. The guide grating in the guide device allowing fluid to pass therethrough may mean that the guide device does not has a significant effect on the flow of fluid through the impeller chamber. Guiding fish towards an inner radial region of the impeller chamber outside the central hub may mean that the fish are guided through the inner radial region and around the outside of the central hub, in contrast to arrangements in which fish can travel through the central hub.

[0017] The at least one impeller blade may be forward swept, for example it may comprise a forward swept portion, which may be provided by a radially outer part of the blade which extends more circumferentially than a radially inner part of the blade. The forward direction may be defined with respect to a rotation direction for which the impeller is designed. The rotation direction is defined as the direction of rotation of the impeller (i.e. clockwise or anticlockwise) with respect to its rotational axis. The use of a forward swept impeller blade may further improve fish survival rates. The inner radial region may lie between a circle through a point on the leading edge of the forward swept portion of the impeller blade and the outer surface of the central hub.

[0018] The guide device may comprise an entrance. The entrance may be configured to receive fish. The guide device may comprise an exit. The exit may be configured to deliver fish towards the inner radial region. A diameter of the exit may be at least 20 percent smaller than a diameter of the impeller chamber. The diameter of the exit may be at least 30 percent smaller, optionally 40 percent smaller than the diameter of the impeller chamber.

[0019] ln some examples, the guide device has a diameter, for example a maximum diameter,which may be defined at the entrance of the guide device. The axial length of the guide device may be at least one quarter of its diameter. It will be appreciated that the axial length of the guide device may be defined as the length of the guide device parallel to the rotational axis of the impeller, for example between the entrance and the exit. In some examples, the axial length is at least one third of the diameter. The axial length may be at least half the diameter.

[0020] A first axial distance may be defined along the rotational axis between the exit of the guide device and a leading edge of the at least one impeller blade. For example, the first axial distance may be defined along the rotational axis between the exit of the guide device and a position on the leading edge of the at least one impeller blade that is at the same diameter as the guide device exit. The first axial distance is optionally no more than the diameter of the exit of the guide device. The first axial distance is optionally no more than three quarters of the diameter of the exit. The first axial distance is optionally no more than one half of the diameter of the exit. In some examples, the first axial distance may be zero, such that there is no axial separation between the exit and the leading edge. In some examples, the exit of the guide device is arranged downstream of at least a portion of the impeller blade, such as a tip. The exit of the guide device may overlap a tip of the impeller blade with respect to the rotational axis. This may provide the advantage of guiding fish towards the impeller such that they bypass a portion of the impeller blade, such as a tip portion of the impeller blade.

[0021] The guide device may comprise a support. The support may be provided around the rotational axis. The guide device may further comprise a fence. The fence may extend from the support towards the impeller. The fence may be a guiding funnel. The support may define the entrance to the guide device. The exit may be defined by the fence at a region along the rotational axis that is closest to the impeller.

[0022] The guide grating may be configured to guide the fish towards the inner radial region. Guiding fish may comprise the guide grating providing a barrier which is impermeable to fish and along which the fish can slide into the inner radial region. The guide grating has an inside surface, which may be defined as the radially inner surface of the guide grating with respect to the rotational axis. The inside surface of the guide grating may be smoothin the flow direction, which may provide the advantage of reducing the likelihood of injury to fish which rub against this inside surface. The guide grating may comprise a plurality of fingers. The surfaces of the fingers may be smooth. As an alternative to a plurality of fingers, the guide grating may be provided by a sheet-like element having openings to permit fluid flow through its surface while guiding fish along the surface. The fence may be configured to guide fish through the exit while permitting fluid in the impeller chamber to flow through the exit and around the exit. The fence may be permeable to fluid and impermeable to fish. The fence may comprise the guide grating.

[0023] The fence, which may be the guide grating, may comprise a plurality of fingers. The plurality of fingers may extend from the support towards the impeller. The plurality of fingers may be evenly distributed around the rotational axis. The plurality of fingers may be arranged to provide a funnel to guide the fish towards the inner radial region. A gap between adjacent fingers of the plurality of fingers may be configured to be less than 50 mm. The gap may be less than 40 mm, optionally less than 30 mm. The gap may be approximately 25 mm. The gap may be less than 25 mm. The gap may be less than 20 mm. The gap may be approximately 10 mm. The gap between adjacent fingers may have a constant width. In other words, the width of the gap may be constant along the fence with respect to the rotational axis. This may be achieved by the plurality of fingers being arranged in a conical, for example frustoconical, array, and each of the plurality of fingers being tapered, such that the edges of adjacent fingers are parallel to one another.

[0024] The plurality of fingers may comprise an alternating array of first fingers and second fingers. The first fingers may have a first length. The second fingers may have a second length. The first length may be greater than the second length. The first length may be approximately double the second length. The second length may be at least one quarter of the first length, optionally at least one third, optionally at least half of the first length.

[0025] The first fingers may extend from the support at a first angle with respect to the rotational axis and the second fingers may extend from the support at a second angle with respect to a rotational axis. The first angle may be different to the second angle. This may provide the advantage of arranging a relatively large number of fingers which can converge to guide the fish towards the inner radial region, while ensuring that fish or other objects (suchas grass) do not get trapped in the end of the fence (i.e. at the exit).

[0026] The plurality of fingers may comprise at least 20 fingers, optionally at least 40 fingers, optionally at least 60 fingers. The plurality of fingers may be arranged in a conical frustum. A longitudinal axis of the conical frustum may be co-axial with the rotational axis of the impeller.

[0027] With respect to the rotational axis of the impeller, the impeller chamber may comprise a first axial portion and a second axial portion. The first axial portion may define an intake of the impeller chamber. The guide device may be arranged in the first axial portion. The impeller may be arranged in the second axial portion of the impeller chamber. The first axial portion may be adjacent to the second axial portion. The first axial portion may overlap with the second axial portion, for example in arrangements wherein the exit of the guide device overlaps the tip of the impeller blade along the rotational axis.

[0028] The fence may comprise a fluid barrier, which may be a solid fluid barrier, for example a solid wall. The fluid barrier may be configured to guide fish and fluid towards the inner radial region. The fluid barrier may divide the impeller chamber, for example the first axial portion of the impeller chamber, into a first fluid channel and a second fluid channel. This arrangement may provide a first fluid channel within the guide device for fish and fluid to flow from the entrance to the exit. This arrangement may also provide a second fluid channel around the guide device for fluid to flow towards the impeller and to bypass the fence. The barrier may be configured to separate the first fluid channel from the second fluid channel. The second fluid channel may be arranged radially (e.g. concentrically) outwards of the first fluid channel and may permit fluid to flow around the first fluid channel (such as around the fence).

[0029] The pump assembly may be configured such that the flow resistance of the first fluid channel is matched to the flow resistance of the second fluid channel. The pump assembly may be configured such that the flow of fluid into the complete impeller eye has a uniform velocity distribution, for example by being configured such that the flow velocity of fluid through the first fluid channel is the same as the flow velocity of fluid through the second fluid channel. The pump assembly may be configured to provide a uniform flow velocity offluid to the impeller, for example over the entire area of the impeller chamber, where the area is defined as a cross sectional area (defined by the plane normal to the rotational axis) of the impeller chamber, such as between the guide device and the impeller.

[0030] The fence may comprise a flow balancing feature, which may be configured to balance the pressure or velocity of the fluid in the first fluid channel with the fluid in the second fluid channel. Balancing the pressure or velocity may comprise equalising the pressure or velocity. The flow balancing feature may comprise one or more openings in the fence. For example, the flow balancing feature may comprise at least one opening in a wall of the fluid barrier. The at least one opening may be permeable to fluid and impermeable to fish, for example fish which are greater than a selected size.

[0031] The support may comprise the guide grating. The guide grating may comprise a plurality of fingers. The plurality of the fingers may be connected to the fence by a plurality of plate ribs. The plurality of plate ribs may be located downstream of the plurality of fingers. The plurality of fingers may extend at least partially over the fluid barrier. The plurality of fingers may comprise round fingers. The plurality of fingers may comprise curved plate fingers.

[0032] The pump assembly may comprise an input chamber upstream of the guide device. The pump assembly may comprise a screen configured to permit fluid to flow from the input chamber towards the impeller chamber. The screen may comprise a plurality of fine openings to permit fluid to pass through the screen. Such fine openings may be configured to prevent fish greater than a selected size from passing through.

[0033] The screen may comprise a first portion. The first portion may have a plurality of coarse openings to permit the passage of fish through the first portion of the screen. The coarse openings are coarser than the fine openings. The first portion may be provided at the entrance of the guide device so that to enter the guide device, fish must be small enough to be able to pass through the coarse openings.

[0034] The pump assembly may comprise a bubble generator. The bubble generator may be positioned above and / or next to the entrance of the guide device.Embodiments of the disclosure may provide an input chamber for a pump assembly comprising any or all of the following features: a guide device comprising an entrance and an exit; and a screen comprising a first portion and a second portion; wherein the first portion comprises a plurality of coarse openings configured to permit the passage of fish through the first portion of the screen, the first portion being provided at the entrance of the guide device such that fish passing through the first portion enter the guide device; wherein the second portion comprises a plurality of fine openings configured to permit fluid to flow towards an impeller chamber of the pump assembly; and wherein the guide device is configured to guide fish from the entrance to the exit to guide fish towards an inner radial region of the impeller chamber.

[0035] This may advantageously provide an input chamber whose guide device does not disturb (or at least does not significantly disturb) the fluid flow into the pump assembly. The input chamber may provide the advantage that the flow through the entrance is the same as that outside the entrance.

[0036] Embodiments of the disclosure may provide an input chamber for a pump assembly, the input chamber comprising any or all of the following features: a guide device comprising an entrance and an exit, wherein the guide device is configured to guide fish from the entrance to the exit to guide fish towards an inner radial region of an impeller chamber of the pump assembly; and a bubble generator assembly provided adjacent to the entrance and configured to provide a bubble curtain to prevent fish passing through the bubble curtain.

[0037] The input chambers described hereinabove may be for a fish friendly pump assembly. The input chambers may be for a pump assembly configured to improve the survival rates of fish entering the pump. The guide device may have any of the features described hereinabove in relation to the pump assembly.

[0038] Brief description of the drawings

[0039] Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:FIG. 1A shows a perspective view of an impeller of a pump assembly according to the present disclosure;

[0040] FIG. 1 B shows a plan view of the impeller of FIG. 1 A;

[0041] FIG. 2 is a schematic side view of a pump assembly according to the present disclosure; FIG. 3A is a side view of a pump assembly according to the present disclosure;

[0042] FIG. 3B is a perspective view of a guide device according to the present disclosure;

[0043] FIG. 3C is a front view of the guide device of FIG. 3B;

[0044] FIG. 4 is a schematic side view of a pump assembly according to the present disclosure; FIG. 5A is a side view of a pump assembly according to the present disclosure;

[0045] FIG. 5B is a perspective view of part of a guide device according to the present disclosure; FIG. 5C is a perspective view of a guide device according to the present disclosure;

[0046] FIG. 6A is a schematic side view of an input chamber according to the present disclosure; FIG. 6B is a front view of an input chamber according to the present disclosure.

[0047] Detailed description of the drawings

[0048] Embodiments of the disclosure relate to a pump assembly, in particular to a pump assembly configured to improve the survival rate of fish passing though the pump assembly. Such a pump assembly may be deemed a “fish-passable”, “fish-friendly” or “less damaging” pump assembly. The pump assembly includes an impeller which rotates in an impeller chamber about a rotational axis. This transfers fluid through the impeller chamber, i.e. from a location upstream of the impeller to a location downstream of the impeller. The impeller has a central hub and at least one impeller blade, for example two or more impeller blades. The impeller blades extend radially outward from the central hub. In particular, the impeller blades extend outward from an outer surface of the central hub. The pump assembly may comprise other components of a pump, such as a drive shaft driven by a motor to provide rotational drive to the impeller.

[0049] The pump assembly also has a guide device located upstream of the impeller. The guide device is configured to guide fish towards an inner radial region of the impeller chamber. It will be appreciated that as the impeller rotates about the rotational axis, the portion of each impeller blade at an inner radial region of the impeller chamber will be rotating witha smaller rotational velocity than the portion of each impeller blade at an outer radial region. As such, if a fish is struck by an impeller blade as the fish passes the impeller, there is a reduced likelihood that the fish will be injured if it is guided towards the inner radial region of the impeller chamber. The inner radial region of the impeller chamber is outside the central hub. This may mean that the inner radial region is defined between the outer surface of the central hub and a region whose radius is smaller than that of the impeller chamber. Therefore, in contrast to other arrangements in which fish are guided through an aperture in the central hub, in the present disclosure the fish are guided around the central hub.

[0050] The guide device also comprises a guide grating. It will be appreciated that a grating has an arrangement of parallel and / or crossed bars / wires which can permit fluid to pass therethrough while preventing larger objects, such as fish, to pass through the grating. As such, the guide device can be arranged such that the flow of fluid is relatively unaffected by the presence of the guide device, while the fish are guided towards the inner radial region. This can increase the survivability of the fish passing through the pump assembly without having a significant effect on the flow characteristics of the fluid passing through the pump assembly.

[0051] Figures 1A and 1B show an impeller 120. The impeller 120 is arranged to rotate about a rotational axis 123. The impeller 120 comprises a central hub 121. The impeller 120 also comprises at least one impeller blade 122. In the arrangement shown, the central hub 121 is substantially conical. The at least one blade 122 comprises two impeller blades 122. The impeller blades 122 may be forward swept, as shown in Figure 1A. The at least one impeller blade 122 comprises a leading edge 122a which, in the case of a forward swept impeller blade 122, is concave. The at least one impeller blade 122 extends from an outer surface 121a of the central hub 121.

[0052] The impeller 120 may be configured to be driven by a drive means such as a motor (not shown). The impeller 120 may be connected to a drive means by an impeller shaft (not shown). The impeller shaft may be configured to rotate about the rotational axis 123. The impeller shaft may be directly connected to the central hub 121.Figure 1A also shows a fish 10 which has a length Lf. With reference to Figure 1 B, a calculation of the fish survival rate is provided. The fish survival rate of an impeller or turbine can be calculated by multiplying the strike possibility of fish hitting the vane (or blade) leading edges with the mutilation ratio.

[0053] The strike possibility is defined by the chance that a fish is hit by a leading edge 122a when the fish 10 is passing the blade leading edge plane area (i.e. the area swept by the leading edge). The strike possibility can be determined in its simplest form by dividing the time period a fish needs to pass the impeller blade leading edge plane (which can be calculated as the length of the fish, Lf, divided by fluid velocity, Vf, passing the leading edge plane area, where Vf can be approximated as the flowrate, Q, divided by the leading edge plane area), by the time period an impeller blade 122 needs to rotate one blade pitch ((2Tir / N) / (cor) = 60 / nN, where r is the radial position, co is the angular velocity (rad / s), n is the pump speed in rpm and N the number of blades). This gives:

[0054]

[0055] The mutilation ratio is defined as the possibility that a fish can survive a hit with an impeller blade. The mutilation ratio is dependent on the type of fish, the shape of the leading edge and the perpendicular strike velocity with the leading edge. A forward swept leading edge (defined by a sweep angle 5) can reduce the perpendicular strike velocity Vs. There is a critical perpendicular strike velocity that fish can survive, meaning that for every impeller there is a maximum pump speed at which fish will not survive a blade strike. By using a forward swept leading edge, the maximum survivable pump speed can be increased. Since the circumferential velocity Vr of the blade leading edge increases linearly with radius r, the sweep angle 5 also has to increase with radius r in order to keep the perpendicular strike velocity Vs (which is Vr*cos(<5)) below the critical strike velocity of a fish.

[0056] Embodiments of the disclosure may permit fish to pass at a smaller radius r of the impeller where the circumferential velocity Vr is lower. As such, embodiments of the disclosure may increase fish survival rates of impellers.Figures 2 to 3C illustrate an example of a pump assembly 100. In particular, Figure 2 shows a schematic view of the pump assembly 100 and Figures 3A to 3C show the pump assembly 100 in more detail. The example of the pump assembly 100 shown in Figures 2 to 3C may be particularly suitable for pumps or turbines where the impeller is located in a suction pipe, because the guide device can be located in the same suction pipe. The pump assembly 100 comprises an impeller 120 which may be the same as the impeller 120 described in relation to Figure 1.

[0057] The pump assembly 100 comprises an impeller chamber 110 and a guide device 130. The impeller 120 is configured to rotate in the impeller chamber 110 about the rotational axis 123 to transfer fluid through the impeller chamber 110. With respect to Figure 2, it will be appreciated that the impeller 120 is configured to transfer fluid up the page. The impeller chamber 110 comprises a wall, for example a cylindrical wall, which defines a conduit through which fluid can flow. In the illustrated example, the impeller chamber 110 comprises a mouth 110a. The mouth 110a is arranged at an entrance to the impeller chamber 110. The guide device 130 may extend from the mouth 110a towards the impeller 120. As such, the guide device 130 may be provided between the mouth 110a and the impeller 120 with respect to the rotational axis 123. The radius of the impeller chamber 110 may be substantially the same as the radius of the impeller 120. In this way, the impeller 120 is configured to rotate about the rotational axis 123 such that the at least one blade 122 sweeps along (or at least very closely to) the inside wall of the impeller chamber 110.

[0058] The guide device 130 is located upstream of the impeller 120. The guide device 130 is configured to guide fish 10 towards an inner radial region 111 of the impeller chamber 110 outside the central hub 121. In the example shown, the guide device 130 comprises a funnel configured to guide fish 10 from an outer radial region of the impeller chamber 110 towards an inner radial region of the impeller chamber 110. The funnel may achieve this by providing a tapering channel for fish 10, wherein the cross-sectional area of the tapering channel decreases as a fish 10 moves closer towards the impeller 120.

[0059] The guide device 130 comprises an entrance 131 and an exit 132. The entrance 131 is configured to receive fish 10 into the guide device 130 while the exit 132 is configured todeliver fish 10 from the guide device 130 to the inner radial region 111. In the arrangement shown, the entrance 131 extends from the wall of the impeller chamber 110 and tapers in a direction towards the impeller 120. The exit 132 is provided closer to the impeller 120 than the entrance 131. As shown in Figure 2, the cross-sectional area (and therefore, for example, the diameter) of the guide device 130 decreases linearly from the entrance 131 to the exit 132. In this way, the shape of the guide device 130 may resemble a conical frustum. The cross-sectional area (for example, the diameter) of the exit 132 is smaller than that of the entrance 131. In the arrangement shown, the diameter of the exit 132 is approximately half the diameter of the impeller chamber 110.

[0060] The guide device 130 may comprise a support 150. The support 150 may be provided around the rotational axis 123. The guide device 130 may also comprise a fence 140. The fence 140 can extend from the support 150 towards the impeller 120. In the example of Figures 2 to 3C, the fence 140 provides the funnel. With particular reference to Figures 3A to 3C, the support 150 may be substantially annular and may be fixedly connected to the impeller chamber 110. In this way, the support 150 is configured to mount the guide device 130 within the impeller chamber 110. In particular, the support 150 provides a base from which the fence 140 can extend towards the impeller 120.

[0061] The fence 140 may comprise a plurality of pins or fingers 141. The plurality of fingers 141 may extend from the support 150 towards the impeller 120. In the arrangement shown, the plurality of fingers 141 are evenly distributed around the rotational axis 123. The plurality of fingers 141 are arranged to provide a funnel to guide the fish 10 towards the inner radial region 111. As best seen in Figure 3C, the plurality of fingers 141 may comprise an alternating array of first fingers 141a having a first length and second fingers 141b having a second length. The first length is greater than the second length. In other words, the fence 140 may comprise an array of alternating short and long fingers. The first length may be approximately double the second length. In the example shown, there are approximately 60 fingers. Furthermore, the plurality of fingers 141 are arranged in a conical frustum. The conical frustum may be centred on the rotational axis 123. For example, the conical frustum may have a longitudinal axis which is coaxial with the rotational axis 123 of the impeller 120, as best seen in Figure 3A.As shown in Figure 3A, a portion of the impeller 120 is received in the exit 132 of the guide device 130. In particular, the nose of the impeller 120 is at a similar position along the rotational axis 123 as the exit 132. As such, there is no axial separation between the exit 132 and the impeller 120. For example, the leading edge 122a of the impeller blade 122 is arranged at a similar axial position to the exit 132, such that there is no axial separation between the leading edge 122a (specifically the tip) of the blade 122 and the exit 132. In the illustrated arrangement, the guide device 130 is arranged such that the exit 132 is further downstream (i.e. at a position further away from the mouth 110a with respect to the rotational axis 123) than the tip of the impeller blade 122. In other words, the guide device 130 overlaps the tip of the impeller blade 122 with respect to the rotational axis 123.

[0062] Figure 2 is arranged such that there is an axial separation, with respect to the rotational axis 123, between the exit 132 and the leading edge 122a of the impeller blade 122. The axial distance is relatively small compared to the diameter of the exit 132. In particular, in the arrangement shown in Figure 2, the axial distance is no more than the diameter of the exit. Specifically, the axial distance is no more than half the diameter of the exit 132.

[0063] With particular reference to Figures 3A to 3C, the support 150 may define the entrance 131 to the guide device 130. The exit 132 is defined by the fence 140 at a region along the rotational axis 123 that is closest to the impeller 120. In other words, the exit 132 of the guide device 130 is arranged on the guide device 130 at a downstream-most position of the guide device 130.

[0064] In the example shown, the pump assembly 100 comprises a guide grating which is configured to guide the fish 10 towards the inner radial region 111. The fence 140 comprises the guide grating. This is because the fence 140 has the plurality of fingers 141 which are spaced apart so as to provide a grating which guides fish 10 towards the inner radial region 111. Furthermore, the gaps between adjacent fingers 141 permit fluid to flow through the guide device 130 (i.e. through the gaps between the adjacent fingers 141 , not merely through the exit 132) while preventing fish 10 from flowing flow through such gaps, such that the fish 10 are forced to travel from the entrance 131 to the exit 132 of the guide device 130. As such, the fence 140 is permeable to fluid and impermeable to fish 10. In particular, the fence 140 is configured to guide fish 10 through the exit 132 (i.e. not aroundthe exit, such as through the gaps between adjacent fingers 141), while permitting fluid in the impeller chamber to flow through the exit 132 and also to flow around the exit 132. In the example shown, the entrance 131 is defined by the circular region of the support 150 at a position along the rotational axis 123 which is furthest from the impeller 120, while the exit 132 is defined at a distal end of the plurality of fingers 141 (in particular the longer, first fingers 141a) as a circular region located at a position along the rotational axis 123 which is closest to the impeller 120.

[0065] The plurality of fingers 141 may each be tapered. In other words, in addition to the arrangement of the plurality of fingers tapering to provide a funnel, each finger of the plurality of fingers may be tapered from its proximal end (i.e. the end connected to the support 150) to its distal end (i.e. the end at which the exit 132 is defined). In particular, if the fingers comprise conical or frustoconical fingers, then the diameter of each finger can decrease (whether such decrease is linear or not) moving along the fence 140 with respect to the rotational axis 123 towards the impeller 120. In this way, the plurality of fingers 141 can be arranged such that the gaps between adjacent fingers 141 do not themselves taper. In other words, the plurality of fingers 141 may be arranged such that their edges are parallel to one another, which can provide a gap between adjacent fingers having a constant width. This reduces the likelihood of a fish 10 getting trapped within the gaps between adjacent fingers 141. Furthermore, as best seen in Figures 3B and 3C, the distal ends of the fingers 141 are free (i.e. not connected to each other). This can provide the advantage of a non-clogging guide device 130 because objects such as grass or reeds are less likely to be trapped by the guide device 130 as they flow through the impeller chamber 110.

[0066] Figure 4 is a schematic diagram of another example of a pump assembly 200. Features labelled with similar reference numerals (i.e. reference numerals whose final two digits are the same) in Figure 4 correspond to features of Figures 1 to 3C. For example, the pump assembly 200 comprises an impeller 220 which may be the same as the impeller 120 described in relation to Figures 1 to 3C. The pump assembly 200 can be integrated into a pump or turbine that has a suction bell, wherein the diameter of the inlet of the suction bell is larger than that of the impeller 220 such that the fluid passing area can be increased by using the larger inlet diameter.The impeller chamber 210 comprises a mouth 210a, which may define the inlet of the pump assembly 200. Similarly to the arrangement described in relation to Figures 2-3A, the mouth 210a is arranged at an entrance to the impeller chamber 210, and the guide device 230 may extend from the mouth 210a towards the impeller 220 such that the guide device 230 is arranged between the mouth 210a and the impeller 220 with respect to the rotational axis 223. In this example, the impeller chamber 210 comprises a cylindrical portion in which the impeller 210 is arranged to rotate, while the mouth 210a provides a flared portion of the impeller chamber 210. Specifically, the radius of the mouth 210a decreases gradually, for example at a decreasing rate, with respect to the rotational axis in a direction towards the impeller 220 (i.e. downstream). The impeller chamber 210 may comprise a smooth transition between the flared portion and the cylindrical portion.

[0067] Similarly to the pump assembly 100, the guide device 230 of the pump assembly 200 is located upstream of the impeller 220 and is configured to guide fish 10 towards an inner radial region of the impeller chamber 210 outside the central hub 221. Specifically, the guide device 230 extends from the mouth 210a of the impeller chamber 210.

[0068] In this type of inlet to the pump assembly 200, the main difference between the guide device 230 of this pump assembly 200 and the guide device 130 of the pump assembly 100 described in relation to Figures 2 to 3C is its shape. In view of the flared portion of the mouth 210a, the guide device 230 may have a greater entrance diameter compared to the guide device 130 described in relation to Figures 2 to 3C. A greater entrance diameter increases the area through which the fluid can pass, thereby reducing throughflow velocity and throughflow resistance. Similarly to the fence 140, the fence 240 has a gradually reducing cross sectional area (for example, diameter). However, in the fence 240, the cross-sectional area decreases in a non-linear manner. In the particular arrangement shown, the fence 240 has a maximum diameter at the entrance 231 which initially reduces linearly along the rotational axis 223 until the diameter of the fence 240 begins to reduce at a reducing rate with respect to the longitudinal axis 223, for example to form a curved funnel as shown in Figure 4. At the exit 232, the fence 240 may be substantially parallel to the rotational axis 223. The diameter of the entrance 231 is approximately seven times the diameter of the exit 232. In other examples, the diameter of the entrance 231 is at leastthree times, preferably at least four times, preferably at least five times, preferably at least six times the diameter of the exit 232.

[0069] The guide device 230 comprises a guide grating configured to permit fluid to pass therethrough. In the arrangement shown, the guide grating is comprised in the fence 240. In particular, the fence 240 provides a guide grating which is configured to guide the fish 10 towards the inner radial region 211. The fence 240 extends from the support 250. In the arrangement shown, the support 250 is fixedly connected to the mouth 210a of the pump assembly 200 and the fence 240 extends from the support 250 towards the impeller 220 in a direction along the rotational axis 223. Although not shown in Figure 4, the fence 240 may comprise a plurality of fingers, which may be arranged in a similar manner to the plurality of fingers 141 shown in Figures 3A to 3C, except that the plurality of fingers in the pump assembly 200 are curved along their longitudinal axis so as to provide the curved funnel shown in Figure 4.

[0070] Figure 5A shows another example of a pump assembly 300. The pump assembly 300 may have similar features to the previously described examples of pump assemblies 100, 200 and it will be appreciated that features with corresponding reference numerals to those examples may have similar arrangements. The pump assembly 300 may be particularly suitable for pumps or turbines with suction boxes. In the arrangement shown, the impeller chamber 310 comprises a mouth 310a, which may be arranged in a similar manner to the mouth 210a described in relation to Figure 4. In the illustrated example, the impeller chamber 310 comprises a flange section 310b. The flange section 310b may extend outwardly from the mouth 310a, for example in a radially outward direction. In this respect, the flange section 310b may comprise an annulus around the mouth 310a, wherein the annulus is normal to the rotational axis 323. In the pump assembly 300, the fluid permeable area may be greater than that for the pump assembly 200 described in relation to Figure 4.

[0071] The fence 340 is configured to guide fish to the inner radial region 311. In this arrangement, the fence 340 comprises a fluid barrier 342, which may comprise a solid wall. As such, the fence 340 is impermeable to both fish 10 and fluid, such that both fish 10 and fluid are guided from an entrance 331 of the guide device 330 to the exit 332 of the guide device330. The impeller chamber 310 may comprise a first axial portion and a second axial portion with respect to the rotational axis 323. The fence 340 may be arranged in the first axial portion. The impeller 320 may be arranged in the second axial portion. The fluid barrier 342 may divide the impeller chamber 310 (in particular, the first axial portion thereof) into a first fluid channel and a second fluid channel. The first fluid channel may be defined within the fluid barrier 342, i.e. radially inward of the fence 340 with respect to the rotational axis 323, while the second fluid channel may be defined outside of the fluid barrier 342, i.e. radially outward of the fence 340. In this way, the guide device 330 is configured such that fish and fluid can flow through the first fluid channel, while fluid only (i.e. without fish, or at least without fish greater than a selected size) flows through the second fluid channel. As shown in Figure 5A, as fluid and fish flow from the first axial portion to the second axial portion (i.e. in a direction up the page), the division is terminated and the impeller chamber is no longer divided.

[0072] The pump assembly 300 may be arranged such that the flow resistance of the first fluid channel and the second fluid channel are matched. This may be achieved by selecting the relative sizes (e.g. diameters) of the fluid channels, for example by selecting a particular shape of the fence 340. By matching the flow resistance of the flow path which is blocked for fish (i.e. the second fluid channel) with the flow path open for fish (i.e. the first fluid channel), a uniform inlet flow over the complete inlet area of the impeller chamber 310 may be achieved. In the pump assembly 300, the guide device 330 comprises a support 350 provided around the rotational axis 323. Specifically, the support 350 extends from the mouth 310a, more specifically from the flange section 310b, of the impeller chamber 310. Therefore, the guide device 330 may be mounted in the impeller chamber 310 by the flange section 310b.

[0073] The fence 340 is mounted to the impeller chamber 310 via the support 350, and extends from the support 350 towards the impeller 320. Similarly to previous examples, the support 350 defines the entrance 331 to the guide device 330. Furthermore, the exit 332 is defined by the fence 340 at a region along the rotational axis 323 that is closest to the impeller 320.

[0074] In the example shown, the support 350 comprises the guide grating. In this respect,differently to the examples described in relation to Figures 2 to 4, it is the support 350 which permits the passage of fluid while remaining impermeable to fish. The support 350 may comprise a plurality of fingers which may each extend from the inlet of the pump assembly 300 to the fence 340. In particular, the plurality of fingers may extend to the fence 340 at the entrance 331 of the guide device 330. This arrangement provides a first fluid channel within the guide device 330 for fish and fluid to flow from the entrance 331 to the exit 332, and a second fluid channel arranged radially (e.g. concentrically) outwards of the first fluid channel and which permits fluid to flow around the first fluid channel (around the fence 340).

[0075] Figure 5B shows a partial view of an example of the guide device 330. As mentioned above, the guide grating may comprise a plurality of fingers 351. In the arrangement shown in Figure 5B, the fingers comprise round fingers 351. In this respect, the fingers 351 may have a circular cross section. The plurality of fingers 351 are connected to the fence 340 by a plurality of plate ribs 352. The plurality of plate ribs 352 are located downstream of the plurality of fingers 351. In this way, each plate rib 352 is arranged in the shadow of its corresponding finger 351 with respect to the direction of fluid flow through the support 350, as indicated by the arrows. Furthermore, the plurality of fingers 351 extend at least partially over the fluid barrier 342.

[0076] As shown in Figure 5B, the fence 340 may comprise a fence rim 343. In this respect, the fence 340 may comprise the fluid barrier 342, which may provide a substantially planar portion, and a fence rim 343 arranged on the fence 340 around the entrance 331 of the guide device 330 and providing a thicker portion for connection to the support 350. The fence rim 343 may be curved so as to provide a smooth edge to the fluid barrier 342. In the arrangement shown, the fingers 351 are connected to the plate ribs 352 which are connected to the fluid barrier 342 via the fence rim 343.

[0077] Figure 5C shows an alternative guide device 330’ which may also be incorporated into the pump assembly 300 shown in Figure 5A. The main difference between the alternative guide device 330’ and the guide device 330 shown in Figure 5B is that the alternative guide device 330’ comprises a plurality of fingers 35T which comprise curved plate fingers 35T. The curved plate fingers 35 T may comprise a semicircular or part-annular cross-section,as shown in Figure 5C. In particular, each of the curved plate fingers 351’ may comprise a pipe section, wherein the plate ribs 352 are connected to each of the curved plate fingers 351’ via an internal surface of the pipe section. Other examples are envisaged, such as one in which the plurality of fingers comprises a mixture of round fingers 351 and curved plate fingers 35T.

[0078] Figures 6A and 6B schematically illustrate an input chamber 460 for a pump assembly 400. Similar reference numerals illustrate similar components with respect to the pump assemblies described in relation to Figures 2 to 5C. The input chamber 460 comprises a guide device 430. The guide device 430 comprises an entrance 431 and an exit 432. Similarly to previous examples, the guide device 430 is configured to guide fish 10 from the entrance 431 to the exit 432 to guide fish towards an inner radial region 411 of the impeller chamber 410. In this arrangement, the fluid permeable area may be further increased compared to the pump assembly 300 described in relation to Figure 5A.

[0079] In the arrangement shown, the guide device 430 comprises a fence 440. The fence 440 comprises a fluid barrier. In this respect, the fence 440 may resemble a pipe. By matching the flow resistance of the flow path which is blocked for fish with the flow path open for fish, a uniform inlet flow over the complete inlet area of the impeller chamber 410 may be achieved. To fulfil this requirement for different suction water levels, a flow balancing area in the fence 440 may be added. The flow balancing area may comprise one or more openings in the fence 440, for example in the fluid barrier wall, which are permeable to fluid but impermeable to fish. Similarly to the arrangement of Figure 5A, the fence 440 provides a first fluid channel within the guide device 330 for fish and fluid to flow from the entrance 431 to the exit 432, and a second fluid channel arranged radially (e.g. concentrically) outwards of the first fluid channel and which permits fluid to flow around the first fluid channel (around the fence 440). The fence 440 may be connected to a base 460a of the input chamber 460 by a support 450.

[0080] As best seen in Figure 6A, the impeller 420 is arranged to rotate about the rotational axis 423, which is substantially vertical. As such, the impeller chamber 410 is arranged as a substantially vertical conduit for fluid to transfer through the impeller 420. The exit 432 of the fence 440 is arranged in the impeller chamber 410 and may surround the rotationalaxis 423. As described in previous examples, the exit 423 may be arranged such that there is no axial separation between the exit 423 and a leading edge, for example a tip, of an impeller blade. In the arrangement shown, the axial separation is no more than the diameter of the exit 423.

[0081] The input chamber 460 may provide a substantially horizontal conduit and may fluidly connect to the impeller chamber 410 at a corner 401, as best seen in Figure 6A. As such, the fence 440 is arranged to bend around the corner 401 as it extends from the input chamber 460 to the impeller chamber 410. As such, the first fluid channel defined between the entrance 431 and the exit 432 may comprise a bend to direct the fluid (and the fish) from a horizontal direction to a vertical direction.

[0082] The input chamber 460 also comprises a screen 470, which may be considered a trash rack. The screen 470 is configured to prevent fish 10 from accessing the impeller chamber 410 other than through the fence 440. In other words, the screen 470 is configured to block fish from entering the second fluid channel, so as to guide fish to the first fluid channel only (i.e. through the fence 440 via the entrance 431), while permitting fluid to flow towards the impeller chamber 410 via the first fluid channel and the second fluid channel. In some arrangements, the screen 470 provides the support 450 between the base 460a of the input chamber 460 and the fence 440.

[0083] As best seen in Figure 6B, the screen 470 may comprise a first portion 471 and a second portion 472. The first portion 471 comprises a plurality of coarse openings 471a. The coarse openings 471a are configured to permit the passage of fish 10 through the screen 470 via the first portion 471. The first portion 471 is provided at the entrance 431 of the guide device 430. In this way, the fish 10 passing through the first portion 471 enter the guide device 430 via the entrance 431.

[0084] The second portion 472 comprises a plurality of fine openings 472a configured to permit fluid to flow towards an impeller chamber 410 of the pump assembly 400 and block passage of fish. In this way, fish may be blocked from entering the input chamber 460 via the fine openings 472a, and therefore the fish 10 are forced to enter the input chamber 460 via the coarse openings 471 such that the fish 10 are guided by the fence 440 towardsthe inner radial region 411 of the impeller chamber 410. Therefore, the second portion 472 of the screen 470 may provide the guide grating. In this way, the input chamber 460 can guide fish towards the inner radial region 411 of the impeller chamber 410 without significantly affecting the flow of fluid towards the impeller chamber 420.

[0085] The screen 470 may be arranged such that the second portion 472 covers a greater area of the screen 470 than the first portion 471. The first portion 471 may be surrounded by the second portion 472. In the arrangement shown, the first portion 471 is surrounded on three edges (e.g. the top and the two sides) by the second portion 472. The first portion 471 is arranged to extend upwards from a bottom or base section 460a of the input chamber 460. It will be appreciated that this configuration is only an example, and that other arrangements may comprise the first portion 471 in a corner or on the side of the screen 470, for example.

[0086] At the entrance 431 of the guide device 430, the fence 440 may have a portion having a rectangular (e.g. square), as best seen in Figure 6B. Moving along the fence 440, this portion may transition to a pipe section having a circular cross section. This may be achieved by a rectangular-based truncated pyramid connected to a cylindrical pipe, although other shapes may be envisaged. The base of the truncated pyramid may define the entrance 431 and be arranged on the screen 470 so as to align with the first portion 471. In this respect, the first portion 471 may comprise a rectangular portion of the screen 470.

[0087] As shown schematically in Figure 6B, the screen 470 may comprise a plurality of regularly-spaced parallel bars extending upwards from the base portion 460a of the input chamber 460. The spacing between adjacent bars in the second portion 472 may be half the spacing between adjacent bars in the first portion 471. This may be achieved by forming the first portion 471 from alternate bars of the second portion 472. In other words, every other bar which defines the second portion 472 may be truncated such that only alternating bars of the second portion 472 extend towards the base portion 460a to define the first portion 471.

[0088] Additionally or alternatively to using a screen 470, the input chamber 460 may comprise abubble generator assembly 480. The bubble generator assembly 480 is configured to provide a bubble curtain 481 to prevent fish 10 passing through the bubble curtain 481. In particular, the bubble curtain 481 is arranged to block fish from accessing the second fluid channel (i.e. around the fence 440). In particular the bubble generator assembly 480 can be provided adjacent to the entrance 431. In the example shown, the bubble generator assembly 480 is configured to generate a curtain 481 of bubbles to the side of the entrance 431 of the guide device 430 and above the entrance 431 to the guide device 430, such that fish 10 swimming towards the impeller 420 may only avoid the bubble curtain 481 by swimming through the entrance 431 of the guide device 430, thereby entering the fence 440 and being guided towards the inner radial region 411 of the impeller chamber 410. It will be appreciated that, since the pump assembly is submersed, bubbles generated by the bubble generator assembly 480 will float vertically upwards. As such, by placing at least part of the bubble generator assembly 480 above the entrance 431, it will be appreciated that the bubble curtain 481 will be produced upwards from a top edge of the entrance 431.

[0089] Aspects of the input chamber 460 may be combined with other examples of pump assemblies 100, 200, 300 as described above. For example, the screen 470 may be arranged in an input chamber upstream of the guide device (such as any of the guide devices 130, 230, 330).

[0090] It will be appreciated from the above description that many features of the different examples are interchangeable and combinable. The disclosure extends to further examples comprising features from different examples combined together in ways not specifically mentioned. Indeed, there are many features presented in the above examples and it will be apparent to the skilled person that these may be advantageously combined with one another.

Claims

- 24 -CLAIMS:

1. A pump assembly comprising:an impeller chamber;an impeller configured to rotate in the impeller chamber about a rotational axis to transfer fluid through the impeller chamber, wherein the impeller comprises:a central hub; andat least one impeller blade extending radially outward from an outer surface of the central hub; anda guide device located upstream of the impeller and configured to guide fish towards an inner radial region of the impeller chamber outside the central hub, wherein the guide device comprises a guide grating configured to permit fluid to pass therethrough.

2. The pump assembly of claim 1, wherein the at least one impeller blade is forward swept with respect to a rotation direction.

3. The pump assembly of any preceding claim, wherein the guide device comprises an entrance configured to receive fish and an exit configured to deliver fish to the inner radial region, optionally wherein a diameter of the exit is at least 20% smaller than a diameter of the impeller chamber.

4. The pump assembly of claim 3, wherein a first axial distance is defined along the rotational axis between the exit and a leading edge of the at least one impeller blade, and wherein the first axial distance is no more than the diameter of the exit.

5. The pump assembly of any preceding claim, wherein the guide device comprises:a support provided around the rotational axis; anda fence extending from the support towards the impeller.

6. The pump assembly of claim 5 as dependent on claim 3, wherein the support defines the entrance to the guide device.

7. The pump assembly of any preceding claim, wherein the guide grating is configured to guide the fish towards the inner radial region.

8. The pump assembly of claim 5 as dependent on claim 3, wherein the fence is configured to guide fish through the exit while permitting fluid in the impeller chamber to flow through the exit and around the exit.

9. The pump assembly of claim 5, wherein the fence is permeable to fluid and impermeable to fish.

10. The pump assembly of claim 5, wherein the fence comprises the guide grating.

11. The pump assembly of claim 5, wherein the fence comprises a plurality of fingers extending from the support towards the impeller;optionally wherein the plurality of fingers is evenly distributed around the rotational axis;optionally wherein the plurality of fingers comprises at least 20 fingers, preferably at least 40 fingers, preferably at least 60 fingers;optionally wherein a gap between adjacent fingers of the plurality of fingers is configured to be less than 50 mm.

12. The pump assembly of claim 11, wherein the plurality of fingers are arranged to provide a funnel to guide the fish towards the inner radial region.

13. The pump assembly of claim 11 or claim 12, wherein the plurality of fingers comprises an alternating array of first fingers having a first length and second fingers having a second length, wherein the first length is greater than the second length; optionally wherein the first length is approximately double the second length.

14. The pump assembly of any of claims 11 to 13, wherein the plurality of fingers is arranged in a conical frustum.

15. The pump assembly of claim 14, wherein a longitudinal axis of the conical frustumis co-axial with the rotational axis of the impeller.

16. The pump assembly of claim 5, wherein the fence comprises a fluid barrier configured to guide fish and fluid towards the inner radial region, and wherein the support comprises the guide grating.

17. The pump assembly of claim 16, wherein the guide grating comprises a plurality of fingers;optionally wherein the plurality of fingers comprise round fingers and / or curved plate fingers.

18. The pump assembly of claim 17, wherein the plurality of fingers are connected to the fence by a plurality of plate ribs, the plurality of plate ribs being located downstream of the plurality of fingers.

19. The pump assembly of claim 17 or claim 18, wherein the plurality of fingers extend at least partially over the fluid barrier.

20. The pump assembly of any preceding claim, further comprising an input chamber upstream of the guide device and a screen configured to permit fluid to flow from the input chamber towards the impeller chamber, and wherein the screen comprises a plurality of fine openings to permit fluid to pass through the screen.

21. The pump assembly of claim 20 as dependent on claim 3, wherein the screen comprises a first portion having a plurality of coarse openings to permit the passage offish through the first portion of the screen, wherein the first portion is provided at the entrance of the guide device such that fish passing through the first portion of the screen enter the guide device.

22. The pump assembly of claim 21, further comprising a bubble generator, wherein the bubble generator is positioned above and / or next to the entrance of the guide device.

23. The pump assembly of any preceding claim, further comprising an impeller shaft- 27 -configured to transfer rotational drive to the impeller, wherein the impeller shaft is configured to rotate about the rotational axis.

24. An input chamber for a pump assembly, the input chamber comprising:a guide device comprising an entrance and an exit; anda screen comprising a first portion and a second portion;wherein the first portion comprises a plurality of coarse openings configured to permit the passage of fish through the first portion of the screen, the first portion being provided at the entrance of the guide device such that fish passing through the first portion enter the guide device;wherein the second portion comprises a plurality of fine openings configured to permit fluid to flow towards an impeller chamber of the pump assembly; and wherein the guide device is configured to guide fish from the entrance to the exit to guide fish towards an inner radial region of the impeller chamber.

25. An input chamber for a pump assembly, the input chamber comprising:a guide device comprising an entrance and an exit, wherein the guide device is configured to guide fish from the entrance to the exit to guide fish towards an inner radial region of an impeller chamber of the pump assembly; anda bubble generator assembly provided adjacent to the entrance and configured to provide a bubble curtain to prevent fish passing through the bubble curtain.

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