Bearing cooling system

Abstract

A bearing cooling system (2, fig.1) for use with a fluid, the system comprising: one or more blades 24 mounted by a bearing 30 for rotation around an axis; a fluid inlet 20 ; a fluid outlet 22; a mai

Description

TECHNICAL FIELD The present disclosure relates to a system for use with a fluid including but not limited to pump systems including a cooling arrangement. BACKGROUND In the field of subsea oil and gas production, well fluid is commonly produced and communicated from a well. To increase or boost oil and gas production and recovery, a subsea pump may be used to add energy to the well fluid. Similar subsea pumps may also be used for subsea seawater injection to inject seawater into a subsea reservoir, thus increasing the pressure in the reservoir so as to enhance oil and gas recovery. Similar subsea pumps may also be used for subsea sCO2 re-injection to inject CO2 into a subsea reservoir, primarily for storage thereof. In any of these applications, a subsea pump typically includes parts which generate heat and so benefit from cooling. The cooling may be provided by pumping a suitable fluid to those parts requiring cooling, for example by pumping a fluid around the parts requiring cooling so as to remove heat from those parts via the fluid. The present disclosure provides an improved system, for example a pump system suitable for use subsea in any of the applications outlined above. SUMMARY From an aspect of the invention, there is provided a system for use with a fluid, the system comprising: a rotary component mounted by a bearing for rotation around an axis, the rotary component comprising one or more rotor blades; a fluid inlet; a fluid outlet axially spaced from the fluid inlet; a main fluid flow path for fluid to flow from the fluid inlet to the fluid outlet, the one or more rotor blades extending radially into the main fluid flow path; a chamber extending radially outwardly from the main fluid flow path and housing power features to cause the rotary component to rotate such that the one or more rotor blades impart a force to the fluid in the main flow path; and a conduit with an inlet positioned radially outward of the main fluid flow path and in fluid communication with the chamber, the conduit configured to direct fluid which has escaped into the chamber from the main fluid flow path to the bearing to cool the bearing. In any example of the disclosure, the system may comprise one or more static diffuser blades extending across the main fluid flow path. In any example of the disclosure, the one or more static diffuser blades may be axially spaced from the one or more rotor blades. In any example of the disclosure, the conduit may extend through one of the diffuser blades. In any example of the disclosure, the chamber may comprise a radially outer wall. In any example of the disclosure, the chamber may comprise a downstream wall. In any example of the disclosure, the downstream wall and the radially outer wall may define a gap which fluidly communicates the chamber with the conduit. In any example of the disclosure, the chamber may be configured such that a portion of the fluid in the chamber is directed radially inwards within the chamber. In any example of the disclosure, the chamber may be configured such that a portion of the fluid in the chamber is directed away from the gap to be recirculated within the chamber. ln any example of the disclosure, the system may further comprise a baffle. In any example of the disclosure, the baffle and the downstream wall may define radially extending fluid passages for the recirculation of fluid within the chamber. In any example of the disclosure, the baffle may be configured to reduce the annular component of the fluid flow at a radially outer end of the baffle. In any example of the disclosure, the fluid may be a multiphase fluid. In any example of the disclosure, centrifugal forces may cause the escaped fluid to be separated. In any example of the disclosure, centrifugal forces may cause the escaped fluid to be separated into at least a heavier stream, comprising a dense phase of the multiphase fluid, and a lighter stream comprising a phase of the multiphase fluid that is less dense than the dense phase. In any example of the disclosure, the heavier stream may be extracted from the chamber, through the gap. In any example of the disclosure, the heavier stream extracted from the chamber, through the gap may be directed to the bearing via the conduit. In any example of the disclosure, the bearing may be located in a bearing chamber. In any example of the disclosure, a conduit outlet of the conduit may be in communication with the bearing chamber. In any example of the disclosure, rotation of the bearing may cause a portion of the fluid supplied to the bearing to move radially outwardly. In any example of the disclosure, the system may further comprise a recycling system configured to direct at least a portion of the cooling fluid radially inwardly back to the bearing to cool the bearing. From a further aspect of the invention, there is provided a system for use with a fluid, the system comprising: one or more blades mounted by a bearing for rotation around an axis; a fluid inlet; a fluid outlet axially spaced from the fluid inlet; a main fluid flow path for fluid to flow from the fluid inlet to the fluid outlet, the one or more blades extending radially into the main fluid flow path; a cooling conduit configured to direct cooling fluid to the bearing to cool the bearing, wherein rotation of the bearing causes a portion of the cooling fluid to move radially outwardly, the system further comprising a recycling system configured to direct at least a portion of the cooling fluid radially inwardly back to the bearing to cool the bearing. In any example of the disclosure, the bearing may be housed in a bearing chamber to which the cooling fluid is supplied. In any example of the disclosure, one or more vanes may be provided in the bearing chamber. In any example of the disclosure, the vanes may be configured to form one or more fluid channels through which fluid may flow from a radially outer part of the bearing chamber back to the bearing. In any example of the disclosure, the system may be a pump system. From a further aspect of the invention, there is provided a multi-stage pump system comprising a plurality of pump stages, wherein each stage of the multi-stage pump system comprises the pump system of any of the various examples described above, wherein the plurality of pump stages are configured for fluid to flow sequentially through the pump stages. BRIEF DESCRIPTION OF DRAWINGS One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which: Figure 1 is a schematic representation of a pump system in which a system according to an example of the disclosure may be used; Figure 2 is a schematic representation of a part of a pump system according to an example of the disclosure; Figure 3 is a schematic radial cross section through a part of a pump system according to an example of the disclosure; Figure 4 is an enlarged view of a part of Figure 3; Figure 5 is a schematic radial cross section through a part of a pump system according to Figure 3 demonstrating the locations of axial cross sections shown in Figures 6 to 9; Figure 6 is a schematic axial cross section through a pump system according to Figures 3 and 5; Figure 7 is a schematic axial cross section through a pump system according to Figures 3 and 5; Figure 8 is a schematic axial cross section through a pump system according to Figures 3 and 5; Figure 9 is a schematic axial cross section through a pump system according to Figures 3 and 5; and Figure 10 is an enlarged view of a part of the pump system according to Figure 9. DETAILED DESCRIPTION Referring to Figure 1, an example pump system 2 suitable for use in a subsea environment is schematically shown. The pump system 2 forms a housing 4 having a longitudinal axis X-X. A plurality of pump stages (which may each include a system according to an example of the disclosure) are provided. In the example shown in Figure 1, three pump stages 6, 8, and 10 are shown. It will be understood however that any suitable number of two or more pump stages for a required pumping function could be provided. As described in further detail below, each pump stage comprises a rotary component mounted for rotation about the longitudinal axis X-X. It will be understood that, if so desired, any suitable number of rotary components may be provided in each pump stage such that each pump stage may include two or more rotary components. Each pump stage also has a fluid inlet, a fluid outlet, and a main fluid flow path (as described further below) for fluid to flow from the fluid inlet to the fluid outlet. The rotary component includes a plurality of rotor blades that extend radially into the main fluid flow path. The rotary component is configured to rotate about the longitudinal axis such that the plurality of rotor blades impart a force to fluid in the main flow path. In any example of the disclosure, the force may be a centrifugal force. Further, the rotary components of each of the plurality of pump stages can be separately controllable so as to be able to rotate at a different speed from the rotary components of the other pump stages. In the example of Figure 1, the three pump stages 6, 8, 10 comprise respective bodies which are mounted together to form a housing 4. The housing 4 has a longitudinal axis X-X and the three pump stages 6, 8, 10 are mounted sequentially along the axis X-X. It will be understood that in other examples of the disclosure which are not shown here, the plurality of pump stages could be positioned differently for fluid to flow sequentially between the pump stages. Thus, the pump stages could for example be mounted sequentially in a radial direction. Each of the pump stages 6, 8, 10 are mounted in series forming a row along the longitudinal axis X-X such that the fluid outlet 14a of a first pump stage 6 of the other pump stages is fluidly connected to the fluid inlet 12b of a second pump stage 8 of the other pump stages, and the fluid outlet 14b of the second pump stage 8 is fluidly connected to the fluid inlet 12c of a third pump stage 10 of the other pump stages such that a continuous main fluid flow path 18 is formed by the main fluid flow paths 16a-c of each of the other pump stages and extends along the longitudinal axis from the fluid inlet 12a of the first pump stage 6 of the other pump stages to the fluid outlet 14c of the third pump stage 10. The housing 4 includes a process fluid inlet 20 through which process fluid may enter the housing 4 and flow into the main fluid flow path 18 via the fluid inlet 12a of the first pump stage 6. The housing 4 further includes a process fluid outlet 22 through which process fluid may exit the housing 4 after flowing out from the fluid outlet 14c of the third pump stage 10. In any example of the disclosure, such as in the example of Figure 1, each pump stage may comprise a separate modular component. Each pump stage may therefore comprise a distinct body (or housing) in which the pump components of the pump stage are provided as will become more apparent from the description below. When assembled within the pump system 2, the body of the first pump stage 6 may be connected to the body of the second pump stage 8 which may be connected to the body of the third pump stage 10. In one example, the bodies of the respective pump stages may be connected together by bolting. In further examples of the disclosure, one or more seals may be provided between each of the pump stage bodies such that the pump stages are sealed against fluid entering between the respective pump stages via the joints between the pump stage bodies. The seals may also limit or stop leakage of process fluid from the main flow path 18 to the external environment at the joins between respective pump stages. ln any example of the disclosure, including that of the pump system of Figures 1 and 2, each pump stage has a rotary component 23 mounted for rotation about the longitudinal axis X-X. In the example of Figure 1, each rotary component 23 comprises a number of rotor blades 24 which are circumferentially distributed about the longitudinal axis X-X and which extend radially into the main fluid flow path 18 and are configured to rotate about the longitudinal axis so as to impart a force to the fluid in the main flow path. The rotor blades 24 can be mounted on a body 25 of the rotary component 23 for rotation about a static longitudinal shaft 26 by bearings (see below). In examples, the rotor blades 24 are impeller blades configured to impart a force to the process fluid. In various examples including the pump system of Figure 1, a static diffuser 28 can be provided in each pump stage which is upstream of the static shaft 26 in the intended direction of flow of fluid in the main fluid flow path. The rotary component(s) 23 can be mounted on the static shaft 26 downstream of the static diffuser 28 by radial bearings 30 extending between an annular base 32 of the body 25 of the rotary component 23 on which the rotor blades 24 are mounted and the static shaft 26. Thrust bearings 34a, 34b may also be provided extending radially between the rotary components 23 and the static diffuser 28 both upstream and downstream of the rotary components 23. In examples and as shown in Figure 2, the static diffuser 28 may comprise diffuser blades 29 downstream of the static shaft 26 that are disposed along a radially outer annular surface 27 of the static diffuser 28 and extend in a generally axial direction. In examples, each of the diffuser blades 29 are spaced apart to allow the process fluid to pass between them. Each rotary component 23 in the example of Figure 1 is shown to have three associated bearings; however, it can be appreciated that in other examples, the number of bearings associated with each rotary component may be greater or fewer. The radial bearing 30 is shown at a radially inner surface of the rotary component. An upstream axial thrust bearing 34a is shown between upstream surfaces of the rotary component and a bearing chamber 56, and a downstream axial thrust bearing 34b is shown between downstream surfaces of the rotary component and the bearing chamber 56. Significant heat is generated at these bearings, which may for example be Poly Crystalline Diamond bearings, and so it is desirable to provide additional cooling for them. The rotary components 23 can be caused to rotate about the longitudinal axis by any suitable means. In various examples, power features are provided in each pump stage to cause the rotary components 23 to rotate in use so as to impart a centrifugal force to the fluid in the main flow path 18. In the example shown in Figure 1, the power features for each pump stage are provided in respective chambers 42 formed within the housing 4 and positioned radially outward of the rotary components 23. In any one of the pump stages, for example in the first pump stage 6, the power features may comprise an electromagnetic motor stator 36 positioned radially outward of a permanent magnet which forms a motor rotor 38 and is positioned on a radially outward location of the rotary components 23 so as to rotate with and to drive the rotation thereof when the electromagnetic motor stator 36 is activated. It will be understood that in any example of the disclosure, each electromagnetic motor stator 36 can be driven separately from the electromagnetic motor stators of the other pump stages. In some examples, a variable frequency drive (not shown) may be positioned externally of the housing 4 and may be configured to drive each of the two or more pump stages 6, 8, 10 separately. The variable frequency drive can be provided in a separate housing. The housing 4 within which the pump stages are located forms a casing enclosing the pump stages. The housing 4 can be sealed against sea water ingress and can be internally pressurised relative to atmospheric pressure if required for use in a subsea environment. In a similar manner, the separate housing forms a casing enclosing the variable frequency drive. It can be sealed against sea water ingress and can be internally pressurised relative to atmospheric pressure if required for use in a subsea environment. In any example, the process fluid may comprise any fluid to be pumped through the pump system 2 and in some examples may comprise a multiphase fluid such as a mixture of oil and water and gas. The process fluid may flow into the housing 4 through the process fluid inlet 20 which is positioned upstream of the rotor blades 24 of the first pump stage 6. The main flow path 18 of the example shown is substantially annular in cross section and is formed between a radially inner surface 43 provided by the static shaft and diffusers of each pump stage and a radially outer surface 45 formed in the housing 4. The process fluid will in use flow along the main flow path 18 in an approximately axial direction through each of the other pump stages in turn before exiting the housing 4 via the process fluid outlet 22 which may form an axial extension of the main flow path 18. Figure 2 shows a side view of a part of one pump stage of a pump system of a type similar to that shown in Figure 1. Although only the rotor blades 24 and diffuser are shown, it will be appreciated that the arrangement of Figure 2 is suitable for use in any of the pump stages used in the pump system of Figures 1 to 10. In the example shown in Figure 2, the pump stage also includes a number of conduits. The conduits 40 extend through each of the static diffuser blades 29 and into the static diffuser 28. In the example shown, each static diffuser blade 29 may comprise a conduit 40 however in other examples it can be appreciated that any number of the static diffuser blades 29 can comprise a conduit 40, including just one. In examples, the conduit 40 acts as a cooling passage, directing fluid from a radially outer region of the pump stage towards parts of the pump stage that require cooling. In examples, the conduit 40 directs fluid radially inward within the pump stage towards the bearings that need to be cooled. This has the advantage of eliminating the need for a separate cooling system. In any example of the disclosure, the cooling fluid communicated through the conduit 40 can be a separated component part of the process fluid. The cooling system described herein separates a component part of the process fluid that is suitable for cooling using the centrifugal forces provided by the pump system 2, and then communicates this component part of the process fluid as a cooling fluid to the bearings. Figure 3 is a schematic enlarged sectional view through a part of one of the pump stages of Figure 1. The pump stage shown includes a system according to an example of the disclosure which provides a means of cooling a bearing in the pump stage as will be described in further detail below. The structural features of the pump stage 100 of Figure 3 are as described above in relation to Figures 1 and 2 and will not be described here again where they are given the same reference number. The rotor, or impeller, blades 24 of the pump stage shown in Figure 3 are configured to drive the process fluid in an axial direction within the main fluid flow path 18. Due to the rotation of the rotor blades 24 during operation of the pump stage 100, high centrifugal forces within the pump stage 100 cause a small portion of the process fluid within the main fluid flow path 18 to be forced radially outward through one or more gaps G formed in the radially outer surface 45 of the main fluid flow path 18. These gaps G may for example be formed at a junction between the motor rotor 38 of the rotary component 23 and the housing 4 as an axial play is provided that allows the rotary component 23 to rotate freely. The portion of the process fluid which escapes from the main fluid flow path 18 may become trapped in a space (as defined below), through which the motor rotor 38 moves in use, that is radially outward of the main fluid flow path 18. As seen in Figure 3, the space in the pump stage 100 and other examples is a chamber 42 that is radially outward of the main fluid flow path 18. The chamber 42 may be annular. The chamber 42 is configured to house the motor rotor 38. The radially outer surface 45 of the main fluid flow path 18 is at least partially defined by a radially inner surface of an axially extending partition 47. The chamber 42 may be formed between a radially outer surface of the axially extending partition 47 and a radially outer wall 44 of the chamber 42. At least in some examples, the radially outer wall 44 of the chamber 42 may have a radially outer surface which forms part of a radially outer surface of the housing 4. An opening 49 is formed in the axially extending partition 47, through which the rotary component 23 may extend. In examples, the multiphase process fluid that is forced radially outward of the main fluid flow path 18 becomes trapped within this chamber 42. In examples, the motor rotor 38 rotates within the chamber 42 such that centrifugal forces are applied to the multiphase process fluid in the chamber 42. The process fluid will become separated into its constituent components, or phases, as a result of these centrifugal forces. In examples, each of the constituent components can be otherwise known as a respective stream. The higher density fluid is separated to be radially outward of the lower density fluid. In examples, the higher density fluid forms a heavier fluid stream, or heavier stream, and the lighter fluid forms a lighter fluid stream, or lighter stream. In examples, the heavier stream comprises a fluid suitable for cooling, for example water, oil or a mixture of the two. In examples, the lighter stream comprises a fluid suitable for reducing windage losses, for example a gas such as natural gas, methane, carbon dioxide or a mixture of gases. In examples, the heavier stream is forced radially outward such that it is in contact with a radially outer wall 44 of the chamber 42. In examples, the direction of travel of the heavier stream is split at a radially outer, downstream region of the chamber 42. In examples, a portion of the heavier stream is extracted from the chamber 42 to act as a cooling fluid. The remainder of the heavier stream is directed radially inward to be recirculated. The recirculated fluid may be considered to be recycled. In examples, the recirculated fluid may be known as a recycled portion of the heavier stream. In examples, the recycled portion may be recycled within the chamber 42. In examples, the recycled portion may also be recycled into the main fluid flow path 18. Continued reference is made to Figure 3, as well as additional reference to Figure 4 which shows an enlarged view of part of the schematic section of pump stage 100. In examples of the pump stage 100, the chamber 42 comprises a downstream wall 46 that defines the downstream end of the chamber 42 that is configured such that a portion of the heavier stream can be extracted from the chamber 42. The downstream wall 46 extends radially from a radially inner surface 48 of the chamber 42, towards the radially outer wall 44. In examples, the downstream wall 46 comprises a radially outer surface 50 opposite the radially outer wall 44 of the chamber 42. A gap 52 (for example a radial gap) is defined between the radially outer surface 50 of the downstream wall 46 and the outer wall 44 of the chamber 42. In examples, a portion of the heavier stream is able to traverse the gap 52 to enter an annular cavity 54 that is axially downstream of the chamber 42. In examples, the annular cavity 54 is in fluid communication with the conduit 40 which communicates the cooling fluid with a bearing chamber 56, in the example of Figure 3, a bearing chamber 56 in which the radial bearing 30 is located. In examples, the gap 52 fluidly communicates the chamber 42 with the conduit 40. In examples, the portion of the heavier stream which flows through the gap 52 can be said to have been siphoned out of the chamber 42 for use as a cooling fluid. In examples, this portion of the heavier stream is communicated to the conduit 40. Details of the pump stage 100 shown in Figure 3 will now be described with reference to Figures 5 to 10. The structural features of the pump stage of Figures 5 to 10 are substantially as described above in relation to Figure 3 and will not be described here again where they are given the same reference number. Figure 5 is a sectional view through a pump stage similar to that of Figure 3, wherein a larger radial extent of the pump stage is shown. Figures 5 displays the location of the axial sections shown in Figures 6 to 9. With continued reference to Figure 3 as well as additional reference to Figures 5, 6 and 7, in examples of the pump stage 100, the chamber 42 comprises a baffle 58 proximate the downstream wall 46. The baffle 58 and the downstream wall 46 are configured to direct a portion of the heavier stream radially inwardly to be recycled. In examples, the downstream wall 46 of the chamber 42 comprises radially extending recesses 60. The baffle 58 is in contact with downstream wall 46 such that an annular surface of the baffle 58 and the recesses 60 define fluid passages. In examples, the fluid passages are configured to provide a downstream flow path for a portion of the heavier stream to be recycled back to a radially inward region within the chamber 42. In examples, the baffle 158 is a fixed wall that extends annularly around the longitudinal axis X-X of the pump stage 100. The baffle 158 may extend over the full radial extent of the chamber 142. In examples, the chamber 42 further comprises an upstream wall 62 that comprises recesses (not shown) similar to those in the downstream wall 46. A second baffle 66 is in contact with the upstream wall 62 such that an annular surface of the baffle 66 and the recesses 64 of the upstream wall 62 define upstream fluid passages. In examples, the upstream fluid passages are configured to provide an upstream flow path for the recycled portion of the heavier stream to be recycled back to a radially inward area of the chamber 42. The second baffle 66 extends annularly around the longitudinal axis X-X of the pump stage 100. In examples, the flow of the fluid within the chamber 42 has a substantial annular component imparted to the fluid by the rotation of the rotary components 23. This annular component is disadvantageous for extracting the cooling fluid portion and for recycling the recycled portion of the heavier stream. In examples, the baffle 58 comprises de-swirler features on the reverse side of the baffle(not shown). De-swirler features are objects with geometries, such as directional surfaces, blades or vanes, that are configured to reduce or remove the annular component of the fluid flow proximate the baffle 58. In examples, the baffle 58 may comprise de-swirler features towards the radially outer portion of the baffle 58 in order to particularly reduce the annular component of the fluid flow proximate the gap 52. In examples, the de-swirler features may be located at any point along the radial extent of the baffle. The de-swirler features are configured to reduce the annular component of the flow of the heavier stream such that when the stream is split into the cooling fluid portion and the recycled portion, a substantial portion of the annular component of the flow has been removed to provide conditions suitable for the fluid to pass through the gap 52. In examples, the lighter stream of the process fluid remains radially inward of the heavier stream. In examples, the chamber 42 is configured such that the area through which the motor rotor 38 rotates during operation of the pump generally comprises the lighter stream. In examples, the composition of the lighter stream reduces windage loss. Windage loss is the reduction in efficiency due to windage forces, for example losses caused by friction between the rotor and the medium the rotor is moving through. In examples, the lighter stream is a less dense medium than water, oil or air, such that the windage losses within the pump are lower than if the chamber contained primarily any one of these example media. With continued reference to Figure 3 as well as additional reference to Figure 8. In examples, the cooling fluid is communicated from the annular cavity 54 to the conduit through the conduit inlet 68. The conduit 40 defines a flow path from a region of the pump stage 100 that is radially outward of the main fluid flow path 18 to a region of the pump stage 100 that is radially inward of the main fluid flow path 18. The conduit 40 extends through a diffuser blade 29 of the static diffuser 28. The conduit 40 through the diffuser blade 29 allows the cooling fluid to radially traverse the main fluid flow path 18 without the inclusion of further apparatus. This is advantageous, as use of the multiphase process fluid as a cooling fluid for the bearings does not require the inclusion of further apparatus other than what already exists within the pump. The pump is therefore more efficient in that no additional apparatus is required across the main fluid flow path that would otherwise reduce the efficiency of the pump. The pump therefore utilises otherwise wasted process fluid for an advantageous use (cooling) without reducing the efficiency of the pump system. With continued reference to Figure 3 as well as additional reference to Figure 9, in examples a conduit outlet 70 is located in a downstream surface 72 of the bearing chamber. In examples, the conduit outlet 70 is disposed radially inward of the downstream axial thrust bearing 34b. In examples, the conduit outlet 70 may be positioned in any suitable location within the bearing chamber 56 such that the cooling fluid is regularly distributed around the bearing chamber 56 to cool each of the bearings. The bearing chamber 56 contains bearing fluid. In examples, the cooling fluid is introduced to the bearing chamber 56 through the conduit outlet 70 into a fluid mixing region 74 of the bearing chamber 56 in which the cooling fluid and the existing bearing fluid are blended together. Heat transfer occurs between the cooling fluid and the bearing fluid such that the bearing fluid is cooled. The bearing fluid is able to more effectively transfer heat away from the bearings as it is being cooled using the cooling fluid. The bearing chamber 56 in the example shown in Figure 3 is similar to the bearing chamber 56 shown in the example of Figure 1. The bearing chamber of Figure 3 differs from that of Figure 1 in that the bearing chamber 56 comprises a radially outer wall 76 with an annular opening 78. In examples, the rotor comprises a complimentary neck portion 80 that extends through the annular opening 78 and into the main fluid flow path 18. The bearing chamber 56 of the example of Figure 3 therefore has a generally square-like cross section. It can be appreciated that, in accordance with the disclosure, the bearing chamber 56 can have a cross section of any suitable shape and dimensions. The rotation of the rotary component 23 during operation causes the fluid to flow in an annular direction. In examples, the rotation of the rotary component 23 also drives the fluid in the bearing chamber 56 in a radial direction, due to the centrifugal forces created by the rotor blades. In examples, the fluid flows radially such that fluid is forced through gaps between the neck portion 80 of the rotary component 23 and the radially outer wall 76 of the bearing chamber. Some fluid from the bearing chamber 56 may then enter the main fluid flow path 18. In examples, fluid within the bearing chamber can become trapped against the radially outer wall 76 of the bearing chamber 56 during operation. This fluid can become radially stagnant and heat up due to its close proximity to the hot bearings. In examples, a recycling system may be provided to mitigate the effects of this. Thus, in examples, to stimulate movement of this stagnant fluid, a vane assembly, similar to the recesses 60 previously described can be used. In examples, the bearing chamber can include bearing chamber vanes 82 that are arranged such that they extend from the downstream wall of the bearing chamber 72 into the bearing chamber 56. The vanes 82 extend radially and are disposed around the longitudinal axis of the pump stage 100. The vanes 82 are arranged such that a fluid channel 84 is formed between each of the vanes 82. With reference to Figure 10, in examples, a gap 86 is formed between a radially outer surface 88 of each vane 82 and the radially outer wall 76 of the bearing chamber 56. Fluid trapped against the radially outer wall 76 of the bearing chamber 56 can move axially into the gap 86. In examples, the gap 86 is configured to reduce the annular motion of the fluid. The fluid is then split, at a radially outer inlet 90 of a fluid channel 84, between the vanes 82, into an annular portion and a radial portion. The annular portion continues to flow in the annular direction. In examples, the annular portion annularly traverses the fluid channel inlet 90 to the annularly adjacent gap. In examples, the radial portion enters the fluid channel 84 and flows in a radially inward direction. The fluid channel 84 is configured to have an outlet proximate the fluid mixing region 74. The radial portion of the fluid exits the fluid channel 84 into the fluid mixing region 74 of the bearing chamber 56 to be recycled within the bearing chamber 56. Thus, a stagnant region of fluid is reduced or eliminated. Cooling of the bearings is improved by the recycling of the bearing fluid in this manner as constant and consistent fluid flow within the bearing chamber avoids hotspots that may cause degradation of the bearings. The heat from the bearings is also better distributed around the bearing chamber, thereby reducing the likelihood of bearing degradation due to uneven environmental conditions. The lifetime of the bearings, as well as the lifetime of the pump system are improved. This is useful for a pump system comprised of pump stages as it is advantageous that the rate of degradation of the bearings in an individual pump stage be even such that each of the bearings in the pump stage require replacement at a similar time. It will further be understood that the conduit 40 forms a closed loop in which process fluid is returned to the main fluid flow path after passing through the conduit 40. In alternative examples, the bearing chamber 56 may be formed to expel cooling fluid to the environment after passing through the bearing chamber. It will be appreciated that the example pump systems shown and described herein have a number of advantages over the prior art systems. Specifically, the hot bearings are cooled without the need for an additional cooling pump or external cooling circuit. This reduces the costs associated with the manufacture of the pump as fewer components are required. Further, an advantage specific to a pump comprising pump stages is that each pump stage comprises its own cooling circuit. The cooling circuit of each pump stage is not required to be externally connectable. Therefore, adding or subtracting pump stages from a pump system requires fewer modifications. As there are fewer moving parts in the proposed pump system compared to traditional cooling circuits in pump systems, the pump may have a greater longevity and reduce maintenance costs. Further, by using the process fluid to cool the bearings, the need for a separate cooling fluid is reduced or perhaps eliminated. Thus, when used in a subsea or other hostile environment, no additional pump external to the sealed and / or pressurised housing formed by the pump stages or within which the pump stages are housed need be provided. This may improve reliability and efficacy of the pump system according to the disclosure. It may also reduce manufacturing and material costs of the pump system. Further, it may avoid a potential reduction in pressure rating of the pump system which could be caused by the need to connect an additional external cooling fluid pump into the pump system. While the disclosure has been described in detail in connection with only a limited number of examples, it should be readily understood that the disclosure is not limited to such disclosed examples. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of disclosure. Additionally, while various examples of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described examples. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A system for use with a fluid, the system comprising:one or more blades mounted by a bearing for rotation around an axis; a fluid inlet;a fluid outlet axially spaced from the fluid inlet;a main fluid flow path for fluid to flow from the fluid inlet to the fluid outlet, the one or more blades extending radially into the main fluid flow path;a cooling conduit configured to direct cooling fluid to the bearing to cool the bearing, wherein rotation of the bearing causes a portion of the cooling fluid to move radially outwardly,the system further comprising a recycling system configured to direct at least a portion of the cooling fluid radially inwardly back to the bearing to cool the bearing.

2. The system of claim 1, wherein the bearing is housed in a bearing chamber to which the cooling fluid is supplied.

3. The system of claim 2, wherein in use the cooling fluid is introduced to the bearing chamber through a conduit outlet into a fluid mixing region of the bearing chamber.

4. The system of claim 2 or 3, wherein one or more vanes are provided in the bearing chamber, wherein the vanes are configured to form one or more fluid channels through which fluid may flow from a radially outer part of the bearing chamber back to the bearing.

5. The system of claim 4, wherein a gap is formed between a radially outer surface of each of the one or more vanes and a radially outer wall of the bearing chamber.

6. The system of claim 4 or 5, wherein in use fluid is split at a radially outer inlet of the one or more fluid channels into an annular portion and a radial portion.

7. The system of claim 6, wherein in use the radial portion enters the one or more fluid channels and flows in a radially inward direction.

8. The system of any of claims 1 to 7, wherein the fluid is a multiphase fluid.

9. The system of any preceding claim, wherein the system is a pump system.

10. A multi-stage pump system comprising a plurality of pump stages, wherein each stage of the multi-stage pump system comprises a pump system as claimed in claim 9, wherein the plurality of pump stages are configured for fluid to flow sequentially through the pump stages.

11. The system of claim 10 when dependent on claim 4, wherein the one or more vanes extend radially and are disposed around the longitudinal axis of the pump stage.

12. The system of claim 3, wherein the conduit outlet is located in a downstream surface of the bearing chamber.

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