Compression or pumping device comprising a means for reducing the tangential velocity of the clearance flow

Abstract

The present invention relates to a fluid compression or pumping device, preferably for multiphase fluids, comprising a stator, a rotor, and a rotor shaft, each rotor being fixed to the rotor shaft, each rotor comprising blades extending substantially radially with respect to the longitudinal axis, and at least one being a shrouded rotor. The pump includes a gap between a shroud of the shrouded rotor and the housing, allowing flow through the gap in a direction opposite to the fluid flow through the shrouded rotor. Furthermore, the stator includes at least one means (35) for reducing the tangential velocity of the fluid arriving from the gap flow, positioned axially opposite the shroud of the shrouded rotor and / or said gap, upstream of the shrouded rotor. Figure 7 to be published

Description

Title of the invention: Compression or pumping device comprising a means for reducing the tangential velocity of the clearance flow. Technical field

[0001] The invention relates to the field of fluid compression or pumping devices, more particularly to the compression or pumping of multiphase fluids. The invention relates more particularly to a multiphase pump which can be used, in particular, in petroleum applications or for injecting and / or storing fluid in a geological reservoir.

[0002] A fluid compression or pumping device generally comprises a or several compression stages. Each compression stage comprises at least one moving part with a rotating wheel (this moving part is also called a "rotor" or "impeller") and at least one stationary part. The stationary part may include a rectifier (also called a "stator" or "diffuser"). These components may be housed within a compression device casing, the stationary part also comprising the casing. The stator may be integrated into the casing.

[0003] The stator can be positioned upstream and / or downstream of a rotating wheel. When positioned downstream, its role is to straighten the fluid flow exiting the wheel, the flow being driven in rotation by the rotating wheel. Its purpose is to supply the next compression stage (another rotating wheel downstream of the stator) or to use the fluid flow directly. Such a stator serves to convert the kinetic energy of the fluid into potential energy. For this purpose, the stator generally includes blades.

[0004] The stator is static, while the rotating wheels are mobile, rotating about a longitudinal axis. The purpose of these rotating wheels is to increase the kinetic and potential energy of the fluid. They are generally fixed to a rotating shaft and include blades.

[0005] More particularly, the invention relates to a pump intended to pump a fluid, for example a multiphase fluid. Previous technique

[0006] In the field of multiphase pumps, the "shrouded rotor" technology has been under development for several years. For example, US patent applications 2011 / 0 280 706 A1 and EP 3 536 975 A1 relate to multiphase pumps with shrouded rotors. This technology consists of adding an external shroud that encloses the rotor blades. This rotor shroud improves stability. assembly mechanics. Indeed, the friction forces induced by the flow passing between this fairing and the external casing help to dampen the vibrations.

[0007] However, the fluid flowing in the gap between the fairing and the housing moves in the opposite direction to the fluid passing through the rotor blades, constituting a secondary flow. Furthermore, this secondary flow, also called the gap flow between the fairing and the housing, has a high tangential velocity, known as "swirl," which disrupts the main flow of fluid entering the rotor. In other words, "gap flow" refers to flow within the gap between two assembled mechanical parts, in this case, between the fairing and the housing.

[0008] Indeed, the fluid exiting the gap flow is mixed with the fluid arriving elsewhere towards the rotor inlet (passing through the blades). This mixing therefore directly impacts the angle of incidence of the fluid entering the rotor and generates a reduction in performance.

[0009] Fig. 1 illustrates the impact of the tangential velocity resulting from the clearance flow on the fluid arriving at the level of the leading edge of the blades 20. Fig. 1 represents a developed view in a longitudinal plane of the rotor.

[0010] Ui represents the speed of the blade at the leading edge, U2 the speed of the blade at the trailing edge. Vj represents the absolute fluid velocity at the leading edge and V2 the absolute fluid velocity at the trailing edge.

[0011] Q corresponds to the rotational speed of the rotor.

[0012] The vector Wi is the relative velocity vector resulting from the velocities Vj and Ui at the leading edge; the vector W2 is the relative velocity vector resulting from the velocities V2 and U2 at the trailing edge. The angle is the angle formed between the vector W2 and the transverse plane shown in dashed lines at the trailing edge.

[0013] The work w per unit mass generated by such a machine can be written, using Euler's equation, in the form:

[0014] w = - ü\V\ = U2V^_ - Ux

[0015] With

[0016] F# the absolute tangential velocity at the leading edge

[0017] the absolute tangential velocity at the trailing edge

[0018] rb r2 the rays considered at the level of the leading edge and the trailing edge respectively.

[0019] If the fluid arriving at the leading edge were perpendicular to the transverse plane (represented by the dashed line), the velocity Vi would be horizontal in the figure (as represented by the dashed arrow). However, here, the velocity Vi forms a non-zero angle with the horizontal, as represented by the dashed arrow. continuous. This is due to the angle <5 / 5 caused by the tangential velocity of the fluid arriving from the clearance flow, as explained previously. This fluid exiting the clearance flow disturbs the fluid arriving at the blades. This phenomenon is known as "pre-swirl," meaning "pre-vortex" or "pre-rotation." Thus, the angle of incidence of the fluid relative to the transverse plane (orthogonal to the longitudinal axis), which would be π / 5 without the impact of the clearance flow, is modified to π + 5π. The change in the angle of incidence of the fluid directly impacts the performance of the turbomachine.

[0020] US patent application 2014 / 0 205 444 A1 proposes anti-vortex devices positioned within the gap to limit dynamic instabilities of the rotor. However, this does not prevent a tangential velocity at the outlet of the fluid from the gap flow.

[0021] US patent application 2015 / 211543 A1 is also known, which proposes anti-vortex devices, positioned at the flow level between the fairing and the casing, to reduce tangential velocity and rotor instabilities. However, this does not prevent a tangential velocity at the outlet of the backflow fluid.

[0022] Patent application WO 2014 / 153 345 A1 relates to a pump with a balancing piston, which does not include impellers. This balancing piston serves to counteract the thrust force for multiphase pumps with a high differential pressure. An anti-vortex device is positioned between the balancing piston and the housing to stabilize the pressure field, particularly when the pump has a significant differential pressure.

[0023] EP patent application 3 913 227 A1 relates to a multiphase pump with a shrouded rotor. Anti-vortex devices are provided on the stator at the clearance flow or at the fluid inlet to the clearance flow to dampen vortices. However, this does not prevent a tangential velocity at the fluid outlet of the clearance flow.

[0024] The object of the invention is to reduce or eliminate the tangential velocity of the fluid exiting the clearance flow of a shrouded rotor in order to increase the performance of the device, while ensuring mechanical stability and reducing the vibrations of the device. Summary of the invention

[0025] The invention relates to a fluid compression or pumping device, preferably for multiphase fluids, comprising a fixed part, at least one rotor and a rotor shaft, each rotor being fixed to the rotor shaft, the rotor shaft being configured to be driven in rotation about a longitudinal axis, each rotor comprising blades extending substantially radially with respect to the axis longitudinal and at least one of the at least one rotor being a shrouded rotor comprising a circumferential shroud connecting the peripheral radial ends of the blades, the fixed part comprising at least one stator and at least one external portion surrounding each rotor, the device comprising a clearance between the external surface of each circumferential shroud of the shrouded rotor and the internal surface of the external portion surrounding this shrouded rotor, allowing clearance flow in a direction opposite to the fluid flow through this shrouded rotor. In addition, the stator upstream of the shrouded rotor comprises a means for reducing the tangential velocity of the fluid arriving from the clearance flow, each reduction means being positioned axially opposite the shroud of the shrouded rotor and / or said clearance, upstream of the shrouded rotor in the direction of the flow through the shrouded rotor.

[0026] Preferably, the device comprises several stators and / or several rotors, preferably with the stators and rotors succeeding each other alternately along the longitudinal axis.

[0027] Advantageously, each rotor comprises at least one set of blades, each set of blades comprising blades regularly distributed around the rotor shaft, preferably each rotor comprises at least two sets of blades following each other longitudinally.

[0028] Preferably, the device comprises several shrouded rotors.

[0029] Advantageously, the circumferential fairing of the shrouded rotor extends longitudinally over a length that covers at least one of the sets of blades, preferably all the sets of blades, and even more preferably, the length of the fairing is equal to the length of the rotor concerned.

[0030] Preferably, the circumferential fairing is circumferentially complete or circumferentially incomplete with at least one opening.

[0031] According to one embodiment of the invention, the reduction means is formed by cavities in the stator to reduce the tangential velocity of the fluid arriving from the play flow, the cavities being opposite the outlet of the fluid from the play flow, the cavities being distributed circumferentially on the stator and separated from each other by interfaces, preferably some of the interfaces comprising extensions of stator blades.

[0032] Preferably, the cavities include crenellated or triangular section grooves developed in the circumferential direction.

[0033] Advantageously, the number of cavities between two successive rotor blades opposite the reduction means is between 3 and 10.

[0034] Advantageously, the ratio between the height of the cavities and the height of the blades is between 10% and 40%, preferably between 15% and 25%.

[0035] Preferably, the ratio between the depth of the cavities and the longitudinal length of the rotor is between 2% and 20%, preferably between 5% and 10%.

[0036] The invention also relates to a multiphase pump comprising a device according to one of the variants or combinations of variants described above.

[0037] The invention also relates to the use of the device as described according to one of the variants or combinations of variants described above, or of the multiphase pump described above, for the extraction of oil or gas from a geological reservoir and / or for the injection of a fluid into a geological reservoir. List of figures

[0038] Other features and advantages of the device and / or pump according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below. [Fig 1]

[0039] Fig. 1 (already described) represents the composition of the velocity components of the fluid arriving on the rotor blades of the device according to the prior art. [Fig 2]

[0040] Figure [Fig.2] represents an embodiment of a compression or pumping device according to the invention. [Fig 3]

[0041] Fig. 3 represents different compositions of the shrouded rotor of the compression or pumping device according to the invention. [Fig 4]

[0042] Fig. 4 represents the effect of the fluid arriving from the clearance flow in the means for reducing the tangential velocity of a compression or pumping device according to the invention. [Fig 5]

[0043] Figure 5 represents different variants of means for reducing the tangential velocity of a compression or pumping device according to the invention. [Fig 6]

[0044] Figure 6 shows a first example of a stator with a means for reducing the tangential speed of a compression or pumping device according to the invention. [Figure 7]

[0045] Figure 7 shows a second example of a stator with a means for reducing the tangential speed of a compression or pumping device according to the invention. [Figure 8]

[0046] Figure 8 represents a comparison of fluid velocities via CFD simulations around an unshod rotor according to the prior art (a)), around a shod rotor according to the prior art (b)) and around a shod rotor and a stator comprising a means for reducing the tangential velocity of a compression or pumping device according to the invention (c)). [Fig 9]

[0047] Fig. 9 shows photographs of a prior art stator (a) and a stator comprising a means for reducing tangential velocity (b). [Fig 10]

[0048] Fig. 10 represents the composition of the velocity components of the fluid arriving on the rotor blades. [Fig 11]

[0049] Fig. 11 represents an example of an incomplete circumferential fairing of a compression or pumping device according to the invention. Description of the implementation methods

[0050] The invention relates to a device for compressing or pumping fluid, preferably multiphase fluid. A "multiphase fluid" is defined as a fluid comprising at least two phases: for example, two separable liquid phases, a gaseous phase and a liquid phase, or a liquid phase and a solid phase. Of course, a multiphase fluid may comprise more than two phases.

[0051] The device of the invention comprises at least one stator, at least one rotor, and a rotor shaft. Each rotor is integral with the rotor shaft, which is itself configured to be driven in rotation about a longitudinal axis. As a result, the rotor shaft can drive each rotor in rotation, to enable the pumping or compression of the fluid.

[0052] Each rotor comprises blades extending substantially radially with respect to the longitudinal axis. Thus, the fluid arrives substantially along the longitudinal axis and is pumped or compressed as it passes through the rotor, passing between the rotor blades.

[0053] Furthermore, at least one rotor is a shrouded rotor comprising a circumferential shroud connecting the peripheral radial ends of the blades. In other words, the circumferential shroud forms an outer casing of a shrouded rotor, integral with it. This outer casing surrounds the outer ends of the blades. This circumferential shroud may, in particular, be formed by a cylindrical shroud with an annular cross-section or a tubular shroud.

[0054] For the purposes of this description, the internal and external ends are relative to each other, the internal end being relatively closer to the longitudinal axis than the external end (also called the peripheral end).

[0055] The circumferential fairing can be circumferentially complete or incomplete (a partial ring is thus stretched). A complete circumferential fairing means a circumferential fairing that extends circumferentially all around the rotor in a single piece, without any openings, whereas an incomplete circumferential fairing does not extend circumferentially all around the rotor: an incomplete circumferential fairing may have at least one opening (preferably a small opening) in the fairing. When the incomplete circumferential fairing has only one opening, it can be in a single piece. When the incomplete circumferential fairing has at least two openings, it can be in at least two separate parts separated by the openings.

[0056] The fixed part includes at least one external portion (a part of the housing) surrounding each rotor. This external portion protects the user from the rotating parts on the one hand, and also contains the fluid flowing through the device on the other.

[0057] The device according to the invention also includes a gap between the outer surface of the circumferential shroud of the shrouded rotor (of each shrouded rotor when several rotors are shrouded) and the inner surface of the outer portion of the stator surrounding each shrouded rotor. This gap forms a substantially annular space between the shrouded rotor and the housing. This gap allows the rotor to rotate even when the housing is fixed. However, it results in a flow of fluid in the opposite direction to the main flow of fluid through each shrouded rotor (i.e., the flow of fluid passing through the blades of the shrouded rotor).

[0058] The fixed part may include a housing (with the various external portions surrounding each rotor) and at least one stator.

[0059] In addition, the stator upstream of the shrouded rotor (of each shrouded rotor when the device includes several shrouded rotors), in the direction of the main flow of the fluid in the shrouded rotor, includes a means for reducing the tangential velocity of the fluid arriving from the gap flow, each reduction means being positioned axially opposite the circumferential shroud of the shrouded rotor concerned and / or said gap, upstream of the shrouded rotor in the direction of the flow through the rotor concerned (i.e. through the blades of the rotor).

[0060] By "the stator upstream of the shrouded rotor, in the direction of the main flow of the fluid in the shrouded rotor", we mean the stator which precedes the rotor in the direction of the main flow, that which is just in front of the rotor concerned.

[0061] By reducing the tangential velocity of the fluid exiting the clearance flow and mixing with the fluid entering the rotor, the impact of this velocity on the fluid entering the rotor can be limited. This therefore improves the performance of the compression or pumping device according to the invention.

[0062] Furthermore, by positioning the reduction means opposite the fairing and / or the clearance, disturbances to the fluid entering the rotor are limited, and vibrations can thus also be reduced. This therefore also improves the service life of the device.

[0063] Advantageously, the device may comprise several stators and / or several rotors, preferably with the stators and rotors arranged alternately along the longitudinal axis. Thus, it is possible to provide several compression or pumping stages to improve the performance of the device.

[0064] According to one embodiment of the invention, each rotor may comprise at least one series of blades, each series of blades comprising blades regularly distributed around the rotor shaft on the same transverse plane.

[0065] According to one aspect of the invention, each rotor may comprise at least two sets of blades, said at least two sets of blades following one another longitudinally. By using at least two sets of blades for each rotor, the compression or pumping performance can be improved.

[0066] By "transverse plane", we mean a plane substantially perpendicular to the longitudinal axis.

[0067] At least one of the rotor blade sets may be helical in shape, and preferably the blade sets of each rotor are helical in shape.

[0068] The device may include several shrouded rotors. In this case, each stator preceding just upstream of each shrouded rotor in the direction of the main flow of the fluid in the shrouded rotor concerned may include a means for reducing the tangential velocity of the fluid arriving from the gap flow, each reduction means being positioned axially opposite the circumferential shroud of the shrouded rotor concerned and / or said gap, upstream of the shrouded rotor concerned in the direction of the main flow through the shrouded rotor concerned.

[0069] According to one aspect of the invention, the circumferential fairing of the shrouded rotor can extend longitudinally over a length sufficient to cover at least one of the blade sets, preferably all the blade sets, and, even more preferably, the length of the fairing is equal to the length of the rotor in question. In other words, the fairing can be total when its length is equal to that of the rotor in question, or partial when its length is strictly less than that of the rotor in question. A partial fairing allows for the maintenance of end-clearance flow within the rotor, generating mixing and enabling the homogenization of a liquid / gas. This is done at the cost of a reduction in the damping generated by the fairing, as the area of ​​high fluid friction (fairing / crankcase) is reduced.

[0070] Preferably, each reduction means can be formed by cavities in the stator to reduce the tangential velocity of the fluid arriving from the clearance flow. These cavities can be located opposite the outlet of the fluid from the clearance flow (i.e., opposite the clearance and / or the shroud, upstream of the rotor in the direction of the flow within the rotor). The cavities are thus as close as possible to the outlet of the fluid from the clearance flow. This positioning minimizes fluid disturbances caused by the fluid exiting the clearance flow. The cavities allow the fluid to be recovered and the tangential velocity of the fluid exiting the clearance flow to be stopped (or limited).

[0071] The cavities can be distributed circumferentially around the stator to ensure homogeneous efficiency in reducing the tangential velocity all around the rotor and thus limit vibrations. The cavities can be separated from each other by interfaces. The interfaces can, for example, form radial walls between the cavities. The multiplication of cavities and interfaces makes it possible to generate fluid vortices within the cavities, which makes it possible to considerably reduce the tangential velocity of the fluid exiting the clearance flow before it mixes with the fluid entering the rotor.

[0072] Preferably, some of the interfaces may include extensions of stator blades (more precisely, stator wheel blades).

[0073] Preferably, the cavities may include slotted grooves (with a rectangular cross-section in a developed plane) or triangular cross-sections developed in the circumferential direction. Thus, opposite and upstream (in the direction of fluid flow in the rotor blades) of the gap and / or the shroud, the stator may include an annular portion comprising slotted or triangular grooves, separated by interfaces such as radial walls. This arrangement makes it possible to reduce the tangential velocity of the fluid exiting the gap flow.

[0074] When the cavities include triangular grooves, preferably right-angled, the depth dsB and the spacing w sB can be defined so as to comply with the following equation where y corresponds to the angle formed by the fluid exiting the clearance flow with respect to a plane orthogonal to the longitudinal direction:

[0075] =

[0076] This allows for optimization of the reduction of the tangential velocity.

[0077] If it is desired to fix the depth dsB, the spacing wsB between the cavities can be determined as a function of the number of cavities N su around the stator and as a function of the The number of stator blades Ns and the outer radius Rext of the stator (radius of the fluid passage section in the stator) are derived from the following equation:

[0078] v _ II ™ SB ~ J

[0079] Alternatively, if it is desired to fix the spacing wsB between the cavities, the depth dsB can be calculated.

[0080] Advantageously, the number of cavities between two successive rotor blades opposite the reduction means can be between 3 and 10. This configuration allows a sufficient reduction of the tangential speed.

[0081] According to one aspect of the invention, the ratio between the height of the cavities and the height of the blades can be between 10% and 40%, preferably between 15% and 25%.

[0082] Advantageously, the ratio between the depth of the cavities and the longitudinal length of the rotor can be between 2% and 20%, preferably between 5% and 10%.

[0083] These different configurations offer a good compromise between sufficient reduction of tangential velocity and complexity of realization.

[0084] The invention also relates to a multiphase pump for a multiphase fluid, comprising a device as described according to one of the variants or combinations of variants of the present description.

[0085] The invention further relates to the use of the device as described according to one of the variants or combinations of variants described in this description or of the polyphase pump described above, for the extraction of oil or gas from a geological reservoir and / or for the injection and / or storage of a fluid in a geological reservoir.

[0086] Fig. 2 illustrates, schematically and not in a limiting manner, an example of a fluid compression or pumping device according to the invention.

[0087] Diagram a) represents an overview and diagram b) represents a zoom at the level of the play flow and the fairing.

[0088] The fluid compression or pumping device according to the invention comprises a rotor 22, which is a shrouded rotor, and a fixed part. The fixed part comprises an external portion 30 (which forms part of the housing) surrounding the shrouded rotor 22 and a stator with a stator wheel 31 (the stator wheel 31 comprising stator blades).

[0089] The shrouded rotor 22 here comprises a series of helical blades 20, but could comprise several series without departing from the scope of the invention. The shrouded rotor 22 also comprises a circumferential shroud 21a surrounding the blades. Here, the shroud 21a is a full shroud surrounding the series of blades, and its axial length is equal to the axial length of the rotor. However, the shroud could alternatively be a partial shroud.

[0090] The device includes a gap between the external surface of the fairing 21a and the internal surface of the external portion 30. This gap results in a flow through the gap 23a. Indeed, a portion of the fluid exiting the shrouded rotor 22 (having passed through the blades 20 of the rotor 22) is drawn into the gap and flows in the opposite direction to the main flow 24 of the fluid passing through the rotor 22.

[0091] The stator here includes, opposite the shroud 21a and the gap, a means 35 for reducing the tangential velocity to reduce the velocity of the fluid exiting the gap flow. This reduction means is positioned just upstream of the shrouded rotor 22, in the direction of the main fluid flow in the shrouded rotor 22, that is to say, in the blades 20 of the shrouded rotor.

[0092] The fluid exiting the clearance flow 23a enters the tangential velocity reduction means 35, which limits the tangential velocity of this fluid. Through this means, the fluid entering the rotor via the flow 24 is less disturbed by the fluid exiting the clearance flow.

[0093] Fig. 3 illustrates, schematically and without limitation, three variants of a fluid compression or pumping device according to the invention.

[0094] In each of the three variants, the fluid compression or pumping device comprises a shrouded rotor 22 and a fixed part. The fixed part comprises an external portion 30 (forming part of the housing) which surrounds the rotor 22 and a stator with a stator wheel 31 (which includes stator blades).

[0095] The shrouded rotor 22 here comprises a series of helical blades 20, but could comprise several series of blades without departing from the scope of the invention.

[0096] In diagram a), the rotor also includes a circumferential fairing 21a that surrounds the blades. The fairing 21a is a full fairing that surrounds the blade assembly and whose axial length is equal to the axial length of the rotor. The fairing 21a generates a clearance flow 23a between the fairing 21a and the outer portion 30.

[0097] In diagram b), the shrouded rotor 22 also includes a circumferential shroud 21b that surrounds the blades. The shroud 21b is a partial shroud that surrounds the blade assembly but whose axial length is strictly less than the axial length of the rotor 22. The shroud 21b generates a clearance flow 23b between the shroud 21b and the outer portion 30.

[0098] In diagram c), the shrouded rotor 22 also includes a partial circumferential shroud 21c whose axial length is strictly less than the axial length of the rotor 22 and which is located in the main flow section. The shroud 21c generates a clearance flow 23c between the shroud 21c and the external portion 30.

[0099] Fig. 4 illustrates, schematically and without limitation, a view developed in a horizontal plane of a compression and pumping device according to the invention.

[0100] The device includes a shrouded rotor with a shroud 21.

[0101] Q illustrates the rotational speed of the rotor.

[0102] The fluid passing through the clearance flow has an absolute velocity VTL composed of a tangential velocity Vq and an axial velocity VzT[.

[0103] The stator just upstream of the shrouded rotor includes a tangential velocity reduction means 35 positioned to capture the fluid exiting the clearance flow (i.e., upstream of the shrouded rotor, the fluid circulating in the clearance flow having a flow opposite to that of the fluid passing through the rotor, and the "upstream" direction being understood as the direction of fluid circulation in the shrouded rotor). This reduction means 35 is opposite the shroud 21 and the clearance. Furthermore, this reduction means 35 includes slotted cavities 36, so that the fluid exiting the clearance flow 25 enters these cavities 36 to dissipate the tangential velocity.

[0104] For this purpose, as can be seen in the figure, the cavities 36 are separated by radial walls 37 which reduce the tangential velocity of the fluid.

[0105] The cavities 36 extend in the longitudinal and radial direction.

[0106] Fig. 5 illustrates, schematically and without limitation, different types of means for reducing the compression and pumping device according to the invention.

[0107] The different reduction means 35 of the diagrams a) to c) show developed views of these reduction means.

[0108] Scheme a) includes a reduction means 35 with crenellated grooves 36 (of rectangular section); scheme b) includes a reduction means 35 with triangular grooves 37; scheme c) includes a reduction means 35 with grooves with curved portions 38.

[0109] Each reduction means 35 can include cavities (crenellated, triangular or complex shapes according to diagrams a) to c)) of height hsB, the height being understood as the length in the radial direction, of depth dsB, the depth being understood as the longitudinal direction (along the longitudinal axis of the compression or pumping device), and the spacing between the cavities wsB.

[0110] For rectangular cavities corresponding to the crenellated grooves of diagram a), the depth dsB corresponds to the longitudinal length of the rectangle and the spacing wsB can correspond to twice (but a different value could be used) the circumferential length of the cavities.

[0111] For the triangular cavities in diagram b), the depth dsB corresponds to the maximum depth of the triangle's cross-section. When the triangle is a right triangle where the right angle forms a substantially longitudinal surface, this surface is positioned such that the fluid exiting the clearance flow strikes this surface in such a way as to significantly reduce the tangential velocity, the The depth dsB corresponds to the length of the side of the right triangle oriented in the longitudinal direction. The spacing wsB can correspond to the side located in the circumferential direction of the cavities.

[0112] For complex-shaped cavities (here curved) in diagram c), the depth dsB corresponds to the maximum depth of the cavity. This complex-shaped cavity may include a substantially longitudinal surface, this longitudinal surface being positioned such that the fluid exiting the flow path arrives against this surface in such a way as to significantly reduce the tangential velocity. The depth dsB may, in particular, correspond to the longitudinal length of this longitudinal surface.

[0113] [Fig.6] illustrates, schematically and without limitation, a portion of the fixed part of a compression or pumping device according to the invention.

[0114] This fixed part comprises a housing with an outer portion 30 and a stator with a stator wheel 31. Furthermore, the stator includes a tangential speed reduction means 35 comprising slotted grooves positioned just upstream of the shrouded rotor (in the direction of fluid flow through the shrouded rotor), so as to capture the fluid exiting the clearance flow (flow in the opposite direction to the flow through the shrouded rotor). These grooves are opposite the shroud of the shrouded rotor and / or the clearance between the shroud and the outer portion 30 of the housing.

[0115] The crenellated grooves are here separated by radial walls forming an interface between the crenellated grooves.

[0116] [Fig.7] illustrates, schematically and not in a limiting manner, another portion of the fixed part of a compression or pumping device according to the invention.

[0117] This fixed part comprises a housing with an outer portion 30 and a stator with a stator wheel 31. Furthermore, the stator includes a tangential speed reduction means 35 comprising triangular grooves positioned just upstream of the shrouded rotor (in the direction of fluid flow through the shrouded rotor) so as to capture the fluid exiting the clearance flow (flow in the opposite direction to the flow through the shrouded rotor). These grooves are opposite the rotor shroud and / or the clearance between the shroud and the outer portion 30 of the housing.

[0118] The triangular grooves are here separated by interfaces (radial walls) forming an interface between the crenellated grooves.

[0119] In figures 6 and 7, it can be observed that the reduction means 35 also includes continuities of the stator wheel blades which thus form interfaces.

[0120] Fig. 11 illustrates, schematically and not in a limiting manner, a section in a plane perpendicular to the longitudinal axis of the device according to the invention.

[0121] The device includes a rotor 22 with several blades 20 (four blades in the figure but the rotor could include a different number of blades) and a stator which includes the external part 30.

[0122] The rotor 20 includes a circumferential fairing 21a around the blades to form a shrouded rotor. This circumferential fairing 21a is circumferentially incomplete because it comprises different parts separated by openings 60. In this example, the incomplete circumferential fairing comprises four distinct parts separated by four openings, but another number of parts / openings could be used. The incomplete circumferential fairing is partially open or shrouded around its circumference. Alternatively, the circumferential fairing 21a could also consist of a single part whose circumferential ends are separated by a single opening.

[0123] In another alternative, the circumferential fairing 21a could be a complete circumferential fairing: this means that the circumferential fairing is then a single piece which covers the entire circumference around the rotor 22, without any opening. Examples

[0124] Figure 8 illustrates comparisons of the tangential velocity at the rotor inlet (in the direction of fluid flow through the rotor) in meters per second for devices according to the prior art and according to the invention, derived from modeling. Figure 8 is a cross-sectional view in a longitudinal plane.

[0125] Diagram a) illustrates an unshod (without shroud) rotor of the prior art. Diagram b) illustrates a shod rotor of the prior art and diagram c) illustrates a shod rotor with a stator comprising a tangential speed reduction means 35 positioned upstream of the shod rotor and opposite the shroud and the gap between the shroud and the outer portion of the housing.

[0126] A significant reduction in tangential velocity is observed thanks to the tangential velocity reduction means in diagram c) compared to diagram b).

[0127] Furthermore, with a reduction means comprising slotted grooves according to the invention, an increase in pressure of 2.9% and an increase in hydraulic efficiency of 2.1% were observed compared with the prior art shrouded rotor solution (without reduction means opposite the shroud and / or clearance and upstream of the rotor).

[0128] With a reduction means comprising triangular-shaped grooves according to the invention, an 8% increase in pressure and a 1.2% increase in hydraulic efficiency were observed compared to the shrouded rotor solution of the prior art (without means of reduction opposite the fairing 21 and / or the play and upstream of the rotor).

[0129] In addition, experimental tests were carried out to compare a shrouded rotor of a prior art device (without reduction means opposite the shroud and / or the play and upstream of the rotor) and a shrouded rotor with reduction means opposite the shroud and / or the play and upstream of the rotor of a device according to the invention.

[0130] Figure 9 illustrates schematically a) a stator of a prior art device comprising a stator wheel 31, without a reduction means opposite the shroud and / or the clearance and upstream of the shrouded rotor, and schematically b) a stator of a device according to the invention comprising a stator wheel 31, and a reduction means 35 opposite the shroud and / or the clearance and upstream of the shrouded rotor. The reduction means 35 here comprises triangular (right-angled) grooves.

[0131] Diagrams a) and b) are photographs of the two stators tested.

[0132] Of course, the other parameters of the two devices are substantially identical (in particular the geometric data). The two devices therefore differ only with regard to the reduction means 35 present in the device of the invention and absent in the prior art device.

[0133] Figure 10 illustrates images taken during tests performed on a device according to the invention with a reduction means comprising triangular grooves. A small quantity of gas (approximately 5% gas volume fraction) was injected to serve as a tracer for the photos and videos taken during the tests. Diagram a) is an image at a flow rate representing 60% of the nominal flow rate of the device according to the invention, which corresponds substantially to the numerical value of 59.3° found by numerical simulations, and diagram b) is an image at a flow rate representing 100% of the nominal flow rate of the device according to the invention. The rotor rotation speed is 2,000 revolutions per minute for both images in diagrams a) and b).

[0134] Arrows 40a and 40b, as well as vortices 41, have been added to these images for clarity. Arrows 40a and 40b represent the direction of flow in the clearance flow, respectively. Arrows 40a are inclined at approximately 41% to the longitudinal axis, and arrows 40b are inclined at approximately 60% to the longitudinal axis. This shows that the fluid exiting the clearance flow has a non-zero tangential velocity (resulting from the rotation of the rotor and the flow through the rotor).

[0135] The vortices 41 in the triangular-shaped grooves of the reduction means show how the tangential velocity is reduced by the effect of the generated vortices.

Claims

Demands

1. Fluid compression or pumping device, preferably for multiphase fluid, comprising a fixed part, at least one rotor (22) and a rotor shaft, each rotor (22) being integral with the rotor shaft, the rotor shaft being configured to be driven in rotation about a longitudinal axis, each rotor (22) comprising blades (20) extending substantially radially with respect to the longitudinal axis and at least one of the at least one rotor being a shrouded rotor comprising a circumferential shroud (21, 21a, 21b, 21c) connecting the peripheral radial ends of the blades (20), the fixed part comprising at least one stator and at least one external portion (30) surrounding each rotor (22), the device comprising a clearance between the external surface of each circumferential shroud (21, 21a, 21b, 21c) of the shrouded rotor and the internal surface of the external portion (30) surrounding this shrouded rotor, allowing clearance flow (23a, 23b,23c) in the opposite direction to the flow of the fluid through this shrouded rotor, characterized in that the stator upstream of the shrouded rotor comprises a means for reducing the tangential velocity of the fluid arriving from the clearance flow, each reduction means (35) being positioned axially opposite the shroud (21, 21a, 21b, 21c) of the shrouded rotor (22) and / or said clearance, upstream of the shrouded rotor (22) in the direction of the flow through the shrouded rotor.

2. Device according to claim 1, comprising several stators and / or several rotors, preferably the stators and rotors succeeding each other alternately along the longitudinal axis.

3. Device according to any one of the preceding claims, wherein each rotor (22) comprises at least one series of blades (20), each series of blades comprising blades (20) regularly distributed around the rotor shaft, preferably each rotor comprises at least two series of blades following each other longitudinally.

4. Device according to any one of the preceding claims, comprising several shrouded rotors.

5. A device according to the preceding claim, wherein the circumferential fairing (21, 21a, 21b, 21c) of the shrouded rotor extends longitudinally over a length sufficient to cover the series or at least one series of blades, preferably all the series blade length and preferably, the length of the fairing (21, 21a, 21b, 21c) is equal to the length of the rotor concerned.

6. Device according to any one of the preceding claims, wherein the circumferential fairing is circumferentially complete or circumferentially incomplete with at least one opening.

7. A device according to any one of the preceding claims, wherein each reduction means (35) is formed by cavities in the stator to reduce the tangential velocity of the fluid arriving from the clearance flow (23a, 23b, 23c), the cavities being opposite the outlet of the fluid from the clearance flow, the cavities being distributed circumferentially on the stator and separated from each other by interfaces, preferably some of the interfaces comprising extensions of the stator blades.

8. Device according to the preceding claim, wherein the cavities comprise crenellated (36) or triangular (37) shaped grooves developed in the circumferential direction.

9. Device according to any one of claims 7 or 8, wherein the number of cavities between two successive rotor blades opposite the reduction means is between 3 and 10.

10. Device according to any one of claims 7 to 9, wherein the ratio between the height of the cavities and the height of the blades is between 10% and 40%, preferably between 15% and 25%.

11. Device according to any one of claims 7 to 10, wherein the ratio between the depth of the cavities and the longitudinal length of the rotor is between 2% and 20%, preferably between 5% and 10%.

12. A multiphase pump comprising a device according to one of the preceding claims.

13. Use of the device according to any one of claims 1 to 11 or of the multiphase pump according to claim 12, for the extraction of oil or gas from a geological reservoir and / or for the injection of a fluid into a geological reservoir.

Images