Pump stator comprising main and secondary blades
The pump stator design with intercalated main and secondary blades addresses fluid separation and inefficiencies, enhancing performance by improving the pressure recovery coefficient and flow guidance for compressible fluids.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-08-17
- Publication Date
- 2026-03-13
AI Technical Summary
Existing pump stators experience significant performance losses due to fluid separation and inefficiencies in converting kinetic energy to potential energy, particularly with compressible fluids like CO2, caused by the geometric shape of the stator blades.
The stator design incorporates a hub and housing with a series of main and secondary blades, where secondary blades are intercalated between main blades, with specific angular and axial offsets to enhance fluid guidance and reduce separation, featuring a configuration that optimizes the pressure recovery coefficient.
The design significantly improves the pressure recovery coefficient by over 38%, maintaining flow straightening capabilities while reducing size and cost, making it suitable for compressible fluids like CO2.
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Abstract
Description
Title of the invention: Stator for a pump comprising main blades and secondary blades technical field
[0001] The invention relates to the field of fluid compression or pumping devices and more particularly to a stator of a fluid compression or pumping device.
[0002] A compression device generally comprises one or more compression stages. Each compression stage includes 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, a rectifier (also called a "stator" or "diffuser"). These elements can be housed within a casing of the compression device.
[0003] The stator is located downstream of a rotating wheel and its role is to straighten the flow of fluid exiting the wheel, the flow being driven in rotation by the rotating wheel. Its purpose is to be able to supply the next compression stage (another rotating wheel downstream of the stator) or to use the fluid flow directly. The stator serves to convert the kinetic energy of the fluid into potential energy. For this purpose, the stator generally comprises blades.
[0004] The stator is static, that is, fixed relative to the outer casing of the compression device, while the rotating wheels are free to rotate about a longitudinal axis. The purpose of these rotating wheels is to increase the kinetic and potential energy of the fluid. They are generally attached to a rotating shaft and typically include blades.
[0005] More particularly, the invention relates to a pump and a pump stator intended to pump a compressible fluid, in particular CO2. Previous technique
[0006] Figure 1 is from US patent application 2018 / 106270 AA. It shows an example of a multiphase pump comprising at least one or more compression stages (Figure 1 shows only one stage), each stage comprising a rotating impeller 1 and a stator 2. The rotating impellers are fixed to the hub 10. The rotating impellers 1 may comprise a plurality of blades 3 and the stators 2 may comprise a plurality of blades 4. In this figure, the direction of fluid flow is represented by an arrow S.
[0007] Due to the geometric shape of certain compression devices, the flow can form a very large angle with the axis of rotation of the device. The dynamic output of the rotating wheel (for example, on the order of 60 to 70 degrees). The geometry of the stators aims to limit the residual angle at the stator output with the axis of rotation of the device.
[0008] US patent application 2018 / 106270 AA relates to a pump stator. The stator may be in two successive parts, located axially one behind the other and separated by an intermediate piece forming an axial distance between these two successive parts. However, the space formed between the upstream blades of the upstream part of the stator and the downstream blades of the downstream part of the stator generates significant performance losses.
[0009] Patent application CN 115 388 038 A relates to a stator of a centrifugal compressor with a radial inlet and an axial outlet. The stator comprises two sets of blades.
[0010] The object of the invention is to improve the performance of the stator of a pump, such as a multiphase pump, where the fluid flow is directed essentially axially along the pump and the stator, by limiting, in particular, the phenomena of separation, and this more particularly for compressible fluids, such as CO2. Summary of the invention
[0011] The invention relates to a pump stator comprising a hub and a housing coaxial about a longitudinal axis, an axial inlet for the introduction of a fluid into the stator and an axial outlet for the evacuation of the fluid from the stator, a first series of main blades and a second series of secondary blades, said main and secondary blades extending radially from the hub to the housing, the generatrices of the main and secondary blades extending substantially axially, the secondary blades being intercalated circumferentially between the main blades, the leading edges of the main blades being on the same first transverse plane.In addition, the leading edges of the secondary blades are positioned on a second transverse plane parallel to the first transverse plane, the second transverse plane being positioned axially at a first predetermined distance from the first transverse plane, in the direction of said axial exit, the first predetermined distance being between 0.1 and 0.3 times, preferably between 0.15 and 0.25 times, the axial length of the main blades.
[0012] Preferably, the axial length of the secondary blades is less than or equal to said axial length of the main blades.
[0013] Advantageously, the trailing edges of the secondary blades form a third transverse plane positioned at a second predetermined distance from a fourth transverse plane formed by the trailing edges of the main blades, the second predetermined distance being between -0.3 times and +0.3 times, of preferably between -0.1 times and +0.1 times, said axial length of the main blades, preferably the second predetermined distance is zero.
[0014] Advantageously, the secondary blades are offset, in the circumferential direction, from the main blades directly preceding them in the circumferential direction, by an angle between 0.2 and 0.5 times, preferably between 0.25 and 0.35 times, the circumferential angular offset of the main blades.
[0015] Preferably, the ratio between the axial outlet section and the axial fluid inlet section is between 0.5 and 2.5, preferably between 0.5 and 1.5.
[0016] According to an advantageous configuration of the invention, the ratio between said axial length of the main blades and the external radius at the leading edge of the main blades is between 0.36 and 1.80, preferably between 0.65 and 1.64.
[0017] According to a preferred embodiment of the invention, the external diameter of the main and / or secondary blades decreases from the axial inlet to the axial outlet.
[0018] Advantageously, the internal diameter of the main and / or secondary blades decreases from the axial inlet to the axial outlet.
[0019] Preferably, the main blades are offset two by two successively in the circumferential direction by a circumferential angular deviation substantially satisfying: A / U = .Mmh
[0020] OL = cr^ALR + b
[0021] With the circumferential angular deviation of the main blades, corresponding substantially to the circumferential angular deviation generated between the leading edge and the trailing edge of each main blade; ALR: the ratio between said axial length of the main blades and the external radius at the leading edge of the main blades and a and Z? being predetermined values.
[0022] The invention also relates to a pump, preferably multiphase, the pump comprising an outer casing, an axial succession of fixed and rotating parts within the outer casing, a first axial inlet opening for the entry of a fluid into the pump, and a second axial outlet opening for the exit of the fluid from the pump. At least one fixed part comprises a stator as described above, preferably the outer casing corresponding to the stator housing.
[0023] Preferably, the outer casing comprises at least one portion with an internal surface of strictly decreasing inner diameter in the direction of the axial fluid flow through the pump, and preferably, the outer casing comprises several portions, each with an internal surface of strictly decreasing, in the direction of the axial flow of the fluid through the pump. List of figures
[0024] Other features and advantages of the stator 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]
[0025] Fig. 1 (already described) represents an example of a polyphasic pump according to the prior art. [Fig 2]
[0026] Figure 2 illustrates a first example of a pump according to the invention. [Fig 3]
[0027] Figure 3 illustrates a second example of a pump according to the invention. [Fig 4]
[0028] Figure 4 illustrates a longitudinal plane view of a pump stator according to the invention. [Fig 5]
[0029] Figure 5 illustrates a view developed along the circumferential direction of a pump stator with certain parameters according to the invention. [Fig 6]
[0030] Figure 6 illustrates a view developed along the circumferential direction of a pump stator with additional parameters to those of [Fig.5] according to the invention. [Fig 7]
[0031] Figure 7 illustrates a performance curve as a function of the axial offset of the edge attack of the secondary blades relative to the leading edge of the main blades, of a pump stator according to the invention. [Fig 8]
[0032] Figure 8 illustrates a performance curve as a function of angular offset circumferential of the leading edge of the secondary blades relative to the leading edge of the main blades, of a pump stator according to the invention. [Fig 9]
[0033] Figure 9 illustrates in diagram a) the profiles of the hubs and stator housing of the pump, along the longitudinal axis, and in diagram b) the profile of the blades, on the parts connected with the hub and with the casing. [Fig 10]
[0034] Fig. 10 illustrates a comparison of the axial velocity fields of a prior art stator (a)) and of the invention (b)) in a longitudinal plane. Description of the implementation methods
[0035] The terms "axial" and "axially" generally mean along or parallel to a longitudinal axis, while the terms "radial" and "radially" generally mean perpendicular to the longitudinal axis. For example, an axial length refers to a distance measured along or parallel to the longitudinal axis, and a radial length corresponds to a distance measured radially, that is, perpendicular to the longitudinal axis. The use of "top," "bottom," "above," "below," and variations of these terms is for convenience, with reference to the figures, without prejudice to their spatial positioning under conditions of use, and does not require any particular orientation of the components.
[0036] In this document, the term "fluid compression device" refers to compressors and pumps intended to compress or pump a fluid, respectively. These devices may be surface, subsea, or bottom-mounted (i.e., in underground formations).
[0037] The terms "upstream" and "downstream" are understood in the direction of the flow of the fluid passing through the stator or the pump.
[0038] The leading edge is the edge of the blade that faces the fluid. Thus, it separates the fluid arriving upstream of the blade into two flows, one that passes on one side of the blade (at the extrados for example) and the other that passes on the opposite side (at the intrados for example).
[0039] The trailing edge is the edge of the blade that is opposite the leading edge. At the trailing edge, the two flows separated by the leading edge can mix again to form a single flow. In other words, the leading edge is at the upstream end of the blade and the trailing edge is at the downstream end of the blade.
[0040] The generatrix of a blade is the median line of the blade, that is to say the line located equidistant from the extrados and the intrados. It is generally curved and extends substantially axially.
[0041] The extrados is the convex outer surface of a blade while the intrados is the concave inner surface of a blade.
[0042] For the purposes of this description, a transverse plane is a plane orthogonal to the longitudinal axis of the stator or pump.
[0043] The invention relates to a pump stator (also called a "rectifier" or "diffuser"), preferably multiphase, comprising: a hub (or "internal hub") and a casing (also called an "external hub") "") coaxial around a longitudinal axis, an axial inlet for introducing fluid into the stator, an axial outlet for removing fluid from the stator, a first set of main blades, and a second set of secondary blades.
[0044] Thus, in the stator of the invention, the fluid flow extends essentially axially from the axial inlet to the axial outlet. This type of stator is therefore suitable for pumps, such as so-called "multiphase" pumps, that is to say, pumps capable of pumping a multiphase fluid.
[0045] According to the invention, the main and secondary blades extend radially from the hub to the housing, and the generatrices of the main and secondary blades extend substantially axially. By "substantially axially," it is understood that the blades and their generatrices are curved, and therefore they do not extend solely in the axial direction.
[0046] The primary and secondary blades may preferably not have openings, such as holes and / or grooves, in order to limit performance losses of the stator and pump. This is especially true when the purpose of the stator is to convert kinetic energy into potential energy, as openings can generate turbulence.
[0047] Furthermore, the secondary blades are circumferentially interposed between the main blades. Thus, the stator of the invention comprises as many main blades as secondary blades and circumferentially includes an alternating pattern of main and secondary blades. The secondary blades, thus interposed, limit fluid separation between the main blades.
[0048] Furthermore, the leading edges of the main blades lie on the same first transverse plane: in other words, their projections onto the longitudinal axis form a single point on the longitudinal axis. Similarly, the leading edges of the secondary blades are positioned on a second transverse plane parallel to the first transverse plane. In other words, the projections of the leading edges of the secondary blades onto the longitudinal axis also form a single point on the longitudinal axis.
[0049] According to the invention, the second transverse plane is positioned axially at a first predetermined distance from the first transverse plane, in the direction of said axial outlet, that is to say, downstream of the first transverse plane. The first predetermined distance is between 0.1 and 0.3 times, preferably between 0.15 and 0.25 times, the axial length of the main blades. This improves the performance of the stator and therefore of the associated pump, by improving the pressure recovery coefficient Cp, defined as follows:
[0050] fu ^Pstafiifue PsjmrPsjn r 1 dynamic^ 1 im1 seen
[0051] With
[0052] Static AP: static pressure difference of the fluid between the axial outlet and the axial inlet
[0053] Dynamic pressure in: dynamic fluid pressure at the axial inlet
[0054] P s,out: static fluid pressure at the axial outlet
[0055] P s> in : static fluid pressure at the axial inlet
[0056] P, in: total fluid pressure at the axial inlet.
[0057] Thus, the pressure recovery coefficient Cp reflects the stator's ability to transform the dynamic pressure due to the kinetic energy of the fluid into static pressure.
[0058] The larger this coefficient, the higher the performance of the stator.
[0059] The position of the leading edges of the secondary blades relative to the leading edge of the main blades defines a stator collection zone located between the first and second transverse planes. Increasing this collection zone expands the stator's potential operating range by reducing its sensitivity to high angles of attack. Indeed, high angles of attack can cause fluid to separate from the upper surface of the blade, obstructing the diffuser inlet. With a large collection zone, the separated fluid can be more easily transported within the stator. Depending on the fluid's viscosity, significant separation can occur. This is particularly true when the viscosity is relatively low, such as that of CO2.
[0060] The invention also makes it possible to maintain the straightening capabilities of the stator, by reducing the tangential speed of the fluid exiting the rotor: the tangential speed of the fluid is reduced at the exit of the stator compared to its entry into the stator.
[0061] Thus, compared to a stator design without secondary blades, the stator of the invention has fewer primary blades. In other words, the stator has substantially the same total number of blades but comprises half of this number as primary blades and the other half as secondary blades. This makes it possible to increase the collection area upstream of the secondary blades and then to improve the flow guidance within the stator thanks to the secondary blades.
[0062] According to one embodiment of the invention, the axial length of the secondary blades may be less than or equal to the axial length of the main blades. This makes it possible to limit the size of the stator and to obtain a good compromise between the expected performance of the stator, its compactness, and therefore its cost.
[0063] Preferably, the trailing edges of the secondary blades can form a third transverse plane positioned at a second predetermined distance from a fourth transverse plane formed by the trailing edges of the main blades, and the second predetermined distance can then be between -0.3 times and +0.3 times, preferably between -0.1 times and +0.1 times, said axial length of the main blades. With the trailing edges of the main and secondary blades close together, the overall size can be reduced and good performance obtained.
[0064] Preferably, the second predetermined distance can be zero. In other words, the trailing edges of the main and secondary blades are on the same transverse plane so as to limit the size of the stator while maximizing its performance.
[0065] According to one configuration of the invention, the secondary blades can be angularly offset, in the circumferential direction, from the main blades directly preceding them in the circumferential direction (the circumferential direction being defined from the lower surface to the upper surface, the orientation of the lower and upper surfaces being the same for all main and secondary blades), by an angle of between 0.2 and 0.5 times, preferably between 0.25 and 0.35 times, the circumferential angular offset of the main blades. In other words, the secondary blades are angularly closer to the upper surface of the preceding main blade than to the lower surface of the following main blade. This configuration also makes it possible to increase the pressure recovery coefficient Cp defined previously, in particular by limiting the potential separation located on the upper surface of the main blade.
[0066] Advantageously, the ratio between the axial outlet cross-section and the axial inlet cross-section of the fluid can be between 0.5 and 2.5, preferably between 0.5 and 1.5. Indeed, too large an increase in the outlet cross-section would lead to separations and therefore performance losses, while too large a reduction in the outlet cross-section reduces the diffusion potential.
[0067] Advantageously, the ratio between the axial length of the main blades and the external radius at the leading edge of the main blades can be between 0.36 and 1.80, preferably between 0.65 and 1.64, so as to ensure a good compromise between performance and compactness. Indeed, too large a ratio reduces compactness and also leads to significant friction losses on the blades. Conversely, too small a ratio improves compactness but requires excessive deflection over a short distance (with significant curvature), which generates separation.
[0068] According to one embodiment of the invention, the external diameter of the main and / or secondary blades can decrease from the axial inlet to the axial outlet. By decreasing the diameter, the outlet cross-section is reduced, which allows for better compression of the fluid. This is particularly advantageous with compressible fluids such as CO2.
[0069] Advantageously, the internal diameter of the main and / or secondary blades can decrease from the axial inlet to the axial outlet, so that the internal diameter on the axial outlet side is compatible, i.e. substantially equal to the internal diameter of the impeller downstream of the stator so as to limit the pressure losses that could be generated by abrupt changes in cross-section.
[0070] Preferably, the main blades can be offset two by two successively in the circumferential direction by a circumferential angular deviation ^mis satisfying substantially: A^=(lO£)-Ad„,fc
[0071] OL- a*ALR + b
[0072] With A^ the circumferential angular deviation of each main blade, corresponding substantially to the circumferential angular deviation generated between the leading edge and the trailing edge of the blade in question (the main blade here). ; ALR: the ratio between the axial length of the main blades and the outer radius at the leading edge of the main blades Given that a and Z are predetermined values, a and b can be determined from numerical simulations or experimental tests. For example, we might have a = 1.16 and b = 0.57.
[0073] The terminology "approximately verifying" means "as close as possible". Indeed, the number of blades is necessarily an integer and consequently, the preceding equations can only be determined as close as possible, taking into account this integer.
[0074] Indeed, surprisingly, this formulation based on the linearization of the OL parameter as a function of the ALR ratio makes it possible to obtain an optimal position, despite numerous possible parameters for optimization and complex numerical simulations and phenomena involved.
[0075] Advantageously, the main blades can have similar generatrices, that is to say that the generatrices of the different main blades can overlap. Preferably, the secondary blades can also have similar generatrices to each other, i.e. the generatrices of the different secondary blades can overlap.
[0076] Preferably, the main and secondary blades may have at least partially similar generatrices: for example, when the trailing edge of the secondary blades is upstream of the trailing edge of the main blades, the generatrice of the secondary blades then overlaps a part of the generatrice of the blades main. Conversely, when the trailing edge of the secondary blades is downstream of the trailing edge of the main blades, the part of the secondary blade generatrix located between the second transverse plane and the fourth transverse plane then overlaps a part of the main blade generatrix.
[0077] With generators that have similar curvatures (between main and / or secondary blades), we limit the disturbances of the flow and therefore the energy losses.
[0078] The invention also relates to a pump, preferably multiphase, comprising an outer casing and an axial succession of compression stages within this outer casing. Each compression stage comprises a fixed portion and a rotating portion. The pump also includes a first axial inlet opening for the entry of fluid into the pump and a second axial outlet opening for the exit of fluid from the pump. Furthermore, at least one fixed portion (preferably each fixed portion) comprises a stator as described above.
[0079] The pump of the invention allows for the pumping of both multiphase and single-phase fluids, including compressible fluids, notably CO2. The use of a stator as described above improves the pump's performance.
[0080] The pump's outer casing can serve as the stator housing. In other words, the pump's outer casing can advantageously correspond to the stator housing described above to reduce the number of parts and simplify assembly.
[0081] Preferably, the outer casing may include at least one portion with an internal surface area whose inner diameter decreases strictly in the direction of the axial fluid flow through the pump (i.e., the portion has an inner diameter that decreases strictly between the first axial inlet opening and the second axial outlet opening). This portion of the outer casing may, in particular, be located opposite the stator of the invention so as to improve compression performance. This is particularly advantageous when the fluid is compressible, such as CO2.
[0082] Preferably, the outer casing may comprise several portions, each with an internal surface area of strictly decreasing inner diameter in the direction of the axial fluid flow through the pump (i.e., the portion has a strictly decreasing internal diameter between the first axial inlet opening and the second axial outlet opening). These portions of the outer casing may, in particular, be located opposite each of the pump stators so as to improve compression performance. This is particularly advantageous when the fluid is compressible, such as CO2.
[0083] For example, the outer casing may comprise a series of cylinders, opposite each rotating part, and portions, each with an internal surface area of strictly decreasing inner diameter (i.e., the portion has a strictly decreasing internal diameter between the first axial inlet opening and the second axial outlet opening), opposite each stator. This configuration is preferred for efficiently compressing compressible gases such as CO2.
[0084] Fig. 2 illustrates, schematically and not in a limiting manner, a first example of a polyphase pump according to the invention.
[0085] The polyphase pump 100, thus represented in a longitudinal plane with Z(m), the position along the longitudinal axis of the pump and R(m) the radial position, comprises several movable rotors Roi, Ro2 and Ro3 and several fixed stators St1, St2 and St3. Thus, the polyphase pump 100 has here three compression stages (but could comprise a different number of compression stages), each compression stage comprising a rotor followed by a stator.
[0086] The multiphase pump 100 also includes an outer casing 101 (into which are inserted the various rotors Roi, Ro2 and Ro3 and the various stators Stl, St2 and St3), which can also serve as a stator housing. In this example, the outer casing is formed by a cylinder of constant internal diameter.
[0087] Figure 3 illustrates, schematically and not in a limiting manner, a second example of a polyphase pump according to the invention.
[0088] The polyphase pump 100, thus represented in a longitudinal plane with Z(m), the position along the longitudinal axis of the pump and R(m) the radial position, comprises several movable rotors Roi, Ro2 and Ro3 and several fixed stators St1, St2 and St3. Thus, the polyphase pump 100 has here three compression stages (but could comprise a different number of compression stages), each compression stage comprising a rotor followed by a stator.
[0089] The flow through the pump begins with rotor Roi, then with stator St1, followed by rotor Ro2 and then stator St2. The fluid then passes through rotor Ro3 and then stator St3. In the figure, the flow therefore occurs from left to right.
[0090] The multiphase pump 100 also includes an outer casing 101 (into which are inserted the various rotors Roi, Ro2, and Ro3 and the various stators Stl, St2, and St3), which can also serve as a stator housing. In this example, the outer casing is formed by a cylinder with an internal diameter that decreases between the pump inlet and outlet. The outer casing includes, in particular, portions 102, opposite each stator Stl, St2, and St3, in which the internal diameter decreases along the longitudinal axis, in the direction of fluid flow through the pump. This configuration is particularly advantageous for highly compressible fluids, such as CO2. Indeed, this large Compressibility generates a decrease in volume which necessitates a decrease in cross-section. The Roi, Ro2 and Ro3 rotors are therefore adapted to the decrease in the volumetric flow rate of the fluid.
[0091] Figure 4 schematically and non-limitingly illustrates a longitudinal view of a stator according to the invention. Z(m) represents the position along the longitudinal axis.
[0092] The leading edges 10 of the main blades are positioned upstream of the leading edges 20 of the secondary blades (the fluid flowing from left to right) and the trailing edges 30 of the secondary blades are positioned upstream of the trailing edges 40 of the main blades (alternatively, the trailing edges 30 of the secondary blades could be downstream of the trailing edges 40 of the main blades or be positioned on the same transverse plane as the trailing edges 40 of the main blades).
[0093] The stator comprises an input section A1 and an output section A2.
[0094] ri*' and respectively represent the radius at the hub at the stator input, the radius at the housing at the stator input, the radius at the hub at the stator output, and the radius at the housing at the stator output.
[0095] Ld represents the axial length of the stator.
[0096] Figure 5 illustrates, schematically and without limitation, a developed view of a stator according to the invention. Z(m) represents the position along the longitudinal axis and G represents the azimuthal evolution of the stator.
[0097] The capture zone ZC is the area located between the first transverse plane defined by the leading edges of the main blades 50 and the second transverse plane defined by the leading edges of the secondary blades 60. It therefore corresponds to the grey area.
[0098] The first transverse plane is defined by the position zLEm which corresponds to the position along the longitudinal axis of the leading edges of the main blades 50.
[0099] The second transverse plane is defined by the position zLEs which corresponds to the position along the longitudinal axis of the leading edges of the secondary blades 60.
[0100] The trailing edges of the secondary blades 60 define a third transverse plane corresponding to the position zTEs along the longitudinal axis.
[0101] The trailing edges of the main blades 50 define a fourth transverse plane corresponding to the position zTEm along the longitudinal axis.
[0102] The stator shown therefore comprises a circumferential succession of main blades 50 and secondary blades 60 (only part of the blades is shown; of course, the stator comprises as many main blades 50 as secondary blades 60 and the number of main blades 50 and secondary blades 60 depends on the application chosen.
[0103] The main blades 50 have an axial length Lm and the secondary blades 60 have an axial length Ls, which is here strictly less than the axial length Lm of the main blades 50.
[0104] The generatrices (represented by the curved dashed lines) of the main blades 50 are similar: they can overlap. The generatrices of the secondary blades 60 can overlap the generatrices of the main blades 50 along their axial length Ls between the second transverse plane and the third transverse plane defined by the trailing edges of the secondary blades 60.
[0105] In addition, the main blades are defined by the angular gap between the leading edge and the trailing edge of each main blade 50 and the stator is defined by the angular overlap, which is the gap between the trailing edge of one main blade 50 and the leading edge of the next main blade 50 (directly in the circumferential direction, from the lower surface of the blades to the upper surface).
[0106] This angular overlap is defined, surprisingly, by a linear equation as a function of the ALR parameter, which is the ratio between the axial length of the main blades and the external radius at the leading edge of the main blades, as expressed below: [01 ° 7] o L ~ ~ a ^ALR + b
[0108] With, for example, a = 1.16 and Z = -0.57
[0109] ^OL can be positive when directed towards (+): in this case, there is indeed a partial overlap of the main blades 50. It can also be negative when directed towards (-): in this case, there is no overlap of the main blades but on the contrary an offset.
[0110] Indeed, numerical simulations have shown that this linearization makes it possible to obtain an optimum, despite the presence of many influential parameters for these complex multi-parameter simulations.
[0111] The angular distance Adtnis between two directly successive main blades (distance between the generatrices of these two blades) can be defined as follows:
[0112] = MOL + A9mh = (l-OL) Mmh
[0113] Figure 6 illustrates, schematically and without limitation, a developed view of a stator according to the invention with other parameters. Z(m) represents the position along the longitudinal axis and X=r^ represents the azimuthal evolution of the stator, r being the radial position and 0 the circumferential angle.
[0114] The first transverse plane is defined by the position zLEm which corresponds to the position along the longitudinal axis of the leading edges of the main blades 50.
[0115] The second transverse plane is defined by the position zLEs which corresponds to the position along the longitudinal axis of the leading edges of the secondary blades 60.
[0116] The trailing edges of the secondary blades 60 define a third transverse plane corresponding to the position zTEs along the longitudinal axis.
[0117] The trailing edges of the main blades 50 define a fourth transverse plane corresponding to the position zTEm along the longitudinal axis.
[0118] The stator shown therefore comprises a circumferential succession of main blades 50 and secondary blades 60 (only a part of the blades is shown; of course, the stator comprises as many main blades 50 as secondary blades 60 and the number of main blades 50 and secondary blades 60 depends on the application chosen).
[0119] The main blades 50 have an axial length Lm and the secondary blades 60 have an axial length Ls, which is here strictly less than the axial length Lm of the main blades 50 (but this axial length Ls of the secondary blades could be greater than or equal to the axial length Lm of the main blades).
[0120] The generatrices (represented by the curved dashed lines) of the main blades 50 are similar: they can overlap. The generatrices of the secondary blades 60 can overlap the generatrices of the main blades 50 along their axial length Ls between the second transverse plane and the third transverse plane defined by the trailing edges of the secondary blades 60.
[0121] Furthermore, the secondary blades 60 are defined by the axial offsets of the leading edges ÔZjp and the trailing edges ^^ respectively with respect to the leading and trailing edges of the main blades 50. Thus, these axial offsets ÔZjE and ÔZTE can be defined by
[0122] ÔZLF - zLEs - zLEm
[0123] 5zTE = zTEs-zTEm
[0124] In addition, the secondary blades 60 are also defined by the offset of the circumferential distance between the extrados of the main blade and the intrados of the intermediate blade ôA^ and the main blades are also defined by the inter-main-blade circumferential distance AX,„.
[0125] Numerical studies have shown that optimal results are obtained for the following criteria: 0.1 <SLES = ^<0,25 - 0.3 S STES = > 5 0.3 and Preference. qj < STES = < 0.1 0.2 < SCP = ^ < 0.5 and preferably 0.25 < SCP = < 0.35
[0126] Fig. 7 illustrates, schematically and not in a limiting way, the curve of the pressure recovery coefficient Cp as a function of the SLES parameter defined previously in the description of Fig. 6.
[0127] The Ref curve represents the recovery coefficient curve Cp for a prior art stator (without secondary blades, with only main blades). The characteristics of the main blades are identical to those used for the invention (except for the number of blades, which is twice the number of main blades).
[0128] The Sim points represent the results from the numerical simulations of the stator of the invention and the FC curve represents the curve that best passes through the Sim points.
[0129] The dashed Ref+10 curve represents a 10% increase in the pressure recovery coefficient Cp of the Ref curve. It is observed that this increase of at least 10% is obtained when the SLES parameter is between 0.1 and 0.3 and that the increase is maximum when the SLES parameter is between 0.15 and 0.25.
[0130] This increase has little or no impact on the fluid outlet angle, which means that the fluid flow straightening performance is maintained.
[0131] [Fig.8] illustrates, schematically and not in a limiting way, the curve of the pressure recovery coefficient Cp as a function of the parameter SCP defined previously in the description of [Fig.6].
[0132] The Ref curve represents the recovery coefficient curve for a prior art stator (without secondary blades, with only main blades). The characteristics of the main blades are identical to those used for the invention (except for the number of blades, which is twice the number of main blades).
[0133] The CFD_Values points represent the results from the numerical simulations of the stator of the invention and the black curve represents the curve that best passes through the CFD_Values points.
[0134] This figure shows a gain obtained when the SCP parameter is less than 0.5 and a more interesting gain when it is between 0.25 and 0.35.
[0135] Fig. 9 illustrates, schematically and not in a limiting manner, examples of hub and housing profiles and blade profiles of a stator according to the invention.
[0136] Diagram a) illustrates the profiles of the hub PI (curve in black) and of the housing P2 (in lighter grey) as a function of the position Z(m) along the longitudinal axis and as a function of the radial position R(m).
[0137] Diagram b) illustrates the profile of the main blades at the level of the hub PI and at the level of the housing P2, as a function of the position Z(m) along the longitudinal axis and as a function of the circumferential position X(m) which depends on the azimuth angle and the radial position.
[0138] The geometric data of the different parameters defined in this description and fixed by these main blade profiles are grouped in the following table. (rad) Ct (m) ^m(m) ALR PI 0.840 0.143 0.110 0.77 P2 0.604 0.143 0.110 0.77
[0139]
[0140]
[0141]
[0142]
[0143]
[0144]
[0145] The stator of the invention comprises, for example, 13 main blades and 13 secondary blades. The secondary blades are defined by the following parameters, also defined previously in this description. SLES STES SCP 0.2 0. 0.3 Examples The stator of the invention, in particular with the parameters described above for [Fig.9] was compared to a prior art stator in which the main blades are identical in their characteristics and in which the number of main blades is twice that of the number of main blades of the stator of the invention. The numerical simulations have the following input conditions: - The fluid is CO2; - The inlet pressure in the stator is 23 bar (i.e., 2.3 x 106 Pa); - The density of the fluid is: 1061.89 kg { m3; - The viscosity of the fluid is: 1.5567 1Q4 Pas; - The angle of the flow at the inlet of the stator is: 71.14°; - The mass flow rate at the stator inlet is: 31.7 kg I s- The pressure coefficient represents the stator's ability to transform the dynamic flow pressure into static pressure. The outlet angle provides information about its ability to straighten the flow (return it to the axial direction) for the next stage of the pump. The addition of secondary blades increases the pressure recovery coefficient (Cp) by more than 38%, from 0.52 to 0.72, thus demonstrating the stator's ability to convert dynamic flow pressure into static pressure. The fluid outlet angle remains within a range of + / -10% compared to the prior art version without secondary blades, ensuring sufficient flow straightening. The significant gain obtained for the pressure recovery coefficient Cp is directly attributable to a modification of the flow topology in the stator of the invention through the offset of the leading edges of the secondary blades, downstream of the leading edges of the main blades.
[0146] The [Fig. 10] illustrates views in a longitudinal plane of the axial velocity field for the prior art stator (diagram (a)) and for the stator of the invention (diagram (b)).
[0147] In the diagram (a), we observe zones 210 and 220 with low velocity linked to flow separations.
[0148] Diagram b) shows a massive reduction in low-speed zones (and therefore a reduction in flow separation) thanks to the use of secondary blades according to the invention.
Claims
Demands
1. Pump stator (St1, St2, St3) comprising a hub and a housing coaxial about a longitudinal axis, an axial inlet (A1) for introducing a fluid into the stator and an axial outlet (A2) for evacuating the fluid from the stator, a first set of main blades (50) and a second set of secondary blades (60), said main (50) and secondary (60) blades extending radially from the hub to the housing, the generatrices of the main (50) and secondary (60) blades extending substantially axially, the secondary (60) blades being intercalated circumferentially between the main (50) blades, the leading edges (10) of the main (50) blades being on the same first transverse plane, characterized in that the leading edges (20) of the secondary (60) blades are positioned on a second transverse plane parallel to the first transverse plane,the second transverse plane being positioned axially at a first predetermined distance (ôzLE) from the first transverse plane, in the direction of said axial outlet (A2), the first predetermined distance (ôzLE) being between 0.15 and 0.25 times the axial length (Lm) of the main blades (50).
2. Pump stator (Stl,St2, St3) according to claim 1, wherein the axial length (Ls) of the secondary blades (60) is less than or equal to said axial length (Lm) of the main blades (50).
3. Pump stator (St1,St2, St3) according to any one of the preceding claims, wherein the trailing edges (30) of the secondary blades (60) form a third transverse plane positioned at a second predetermined distance (ôzTE) from a fourth transverse plane formed by the trailing edges (40) of the main blades (50), the second predetermined distance (ôzTE) being between -0.3 times and +0.3 times, preferably between -0.1 times and +0.1 times, said axial length (Lm) of the main blades (50), preferably, the second predetermined distance (ôzTE) is zero.
4. Pump stator (St1, St2, St3) according to any one of the preceding claims, wherein the secondary blades (60) are offset, in the circumferential direction, from the main blades (50) directly preceding them in the circumferential direction, by an angle between 0.2 and 0.5 times, preferably between 0.25 and 0.35 times, the circumferential angular offset (A0mis) of the main blades (50).
5. Pump stator (Stl,St2, St3) according to any one of the preceding claims, wherein the ratio between the axial outlet area (A2) and the axial inlet area (Al) of fluid is between 0.5 and 2.5, preferably between 0.5 and 1.
5.
6. Pump stator (Stl,St2, St3) according to any one of the preceding claims, wherein the ratio between said axial length (Lm) of the main blades (50) and the external radius at the leading edge of the main blades is between 0.36 and 1.80, preferably between 0.65 and 1.
64.
7. Pump stator (Stl,St2, St3) according to any one of the preceding claims, wherein the external diameter of the main (50) and / or secondary (60) blades decreases from the axial inlet (A1) to the axial outlet (A2).
8. Pump stator (Stl,St2, St3) according to any one of the preceding claims, wherein the internal diameter of the main (50) and / or secondary (60) blades decreases from the axial inlet (A1) to the axial outlet (A2).
9. Pump stator (St1, St2, St3) according to any one of the preceding claims, wherein the main blades (50) are offset two by two successively in the circumferential direction by a circumferential angular deviation Aé / ^, satisfying substantially: etOL^ a^ALR + b With A0^ the circumferential angular deviation of the main blades, corresponding substantially to the circumferential angular deviation generated between the leading edge and the trailing edge of each main blade (50); ALR: the ratio between said axial length (Lm) of the main blades (50) and the external radius at the leading edge of the main blades (50) and a and b being predetermined values.
10. A pump (100), preferably multiphase, comprising an outer casing (101), an axial succession of fixed and rotating parts (Ro1, Ro2, Ro3) inside the outer casing (101), a first axial inlet opening for the entry of a fluid into the pump and a second axial outlet opening for the exit of the fluid from the pump, wherein at least one fixed part comprises a stator (St1, St2, St3) according to any one of the claims previous, preferably the outer envelope (101) corresponding to the stator housing.
11. Pump (100) according to the preceding claim, wherein the outer casing (101) comprises at least one portion (102) with an internal surface of strictly decreasing inner diameter, in the direction of the axial flow of the fluid through the pump (100), preferably the outer casing (101) comprises several portions (102) each with an internal surface of strictly decreasing inner diameter, in the direction of the axial flow of the fluid through the pump (100).