Multiphase pump

Abstract

A multiphase pump for conveying multiphase process fluids is proposed, comprising a pump housing and a rotor disposed within the pump housing and configured for rotation about an axial direction, wherein the rotor includes a pump shaft and at least one impeller fixedly mounted on the pump shaft, wherein a stationary diffuser is adjacent to the impeller and disposed downstream of the impeller, wherein the impeller includes at least one blade, wherein each blade has a radially outer tip, and wherein the impeller includes a ring surrounding the impeller and disposed at the radially outer tips of the blades, wherein a passage is provided between the ring and a stationary portion configured to be stationary relative to the pump housing, the passage extending axially from an inlet to a outlet, wherein at least one vortex suppressor is provided at the passage, and wherein the vortex suppressor is configured and arranged to suppress vortices of the process fluid passing through the passage.

Description

Technical Field

[0001] This invention relates to a multiphase pump for conveying multiphase process fluids, as described in the preamble of the independent claim. Background Technology

[0002] Multiphase pumps are used in many different industries where it is necessary to transport multiphase process fluids, which are mixtures of multiple phases, such as liquid and gas phases. An important example is the oil and gas processing industry, where multiphase pumps are used to transport hydrocarbon fluids, such as for extracting crude oil from oil fields or for transporting oil / gas through pipelines or within refineries.

[0003] Fossil fuels typically do not exist in pure form in oil or gas fields, but rather as multiphase mixtures containing liquid, gaseous, and possibly solid components. For example, this multiphase mixture of crude oil, natural gas, chemicals, seawater, and sand must be pumped out of the oil or gas field. For this fossil fuel transport, multiphase pumps are used, which are capable of pumping liquid-gas mixtures that may also contain solid components (such as sand).

[0004] One challenge in designing multiphase pumps lies in the fact that, in many applications, the composition of the multiphase process fluid changes significantly during pump operation. For example, during oilfield extraction, the ratio of the gas phase (e.g., natural gas) to the liquid phase (e.g., crude oil) changes dramatically. These changes can occur very abruptly and can lead to decreased pump efficiency, pump vibration, or other problems. The proportion of the gas phase in a multiphase mixture is typically measured by the dimensionless gas volume fraction (GVF), which specifies the volume ratio of gas in the multiphase process fluid. In oil and gas industry applications, GVF can vary from 0% to 100%.

[0005] Given the need for efficient oil and gas field extraction, there is an increasing demand for pumps that can be installed directly on the seabed, particularly at depths of 500 m, 1000 m, or even over 2000 m below the surface. Not to mention, designing such pumps is challenging, especially since they must operate for extended periods in harsh underwater environments with minimal maintenance and repair. This necessitates specific measures to minimize the amount of equipment involved and optimize pump reliability.

[0006] It is well known in the art that multiphase pumps are prone to rotor vibration. The pump rotor comprises a pump shaft and an impeller fixed to the pump shaft in a torsional manner. Several reasons make rotor vibration a problem, particularly in multiphase pumps. Typical single-phase centrifugal pumps have significant internal damping due to leakage of the single-phase process fluid along the pump rotor through internal seals or gaps. Examples of such seals or gaps are impeller inlet seals, impeller hub seals, wear rings, throttling bushings, and balancing drums. The leakage flow of the process fluid through these seals or gaps counteracts vibration and produces rotor damping. The physical phenomenon upon which this damping is based is the Lomakine effect. The Lomakine effect is the force generated at small gaps (e.g., at wear rings, throttling bushings, or balancing devices in a centrifugal pump). This force is a result of uneven pressure distribution around the circumference of the pump shaft during the period of rotor eccentricity or pump shaft deflection. Due to rotor eccentricity, the clearance (i.e., the gap between the rotor and the stationary portion surrounding the rotor) is larger on one side of the rotor than on the other. This results in differences in the local velocities of the fluid. The local velocities of the fluid are higher in locations with larger gaps. Higher local velocities lead to lower pressures, and lower local velocities lead to higher pressures. This produces a net corrective force that always acts in the opposite direction to shaft deflection or eccentricity. Therefore, the Lomakin effect supports the centering of the pump shaft and consequently produces rotor damping.

[0007] Multiphase pumps can be designed to transport multiphase process fluids with a GVF ranging from 0% to 100%, i.e., all process fluids from pure liquid (GVF = 0%) to pure gas (GVF = 100%). At high GVF values, the pressure rise generated by a multiphase pump is significantly smaller than at low GVF values. For example, multiphase pumps constructed with helical axial flow impellers typically have only a balance drum and diffuser clearance as voids. These voids are designed to allow liquid leakage and are therefore quite large for applications or operating conditions with high GVF. Therefore, the problem with multiphase pumps is that, for operating conditions particularly with high GVF values, there is only minimal rotor damping due to the Lomazing effect, because multiphase pumps have only a small amount of clearance or voids along the pump shaft, and these clearances and voids are quite large for process fluids with high gas content or near-pure gaseous state. Furthermore, as already explained, at high GVF values, the pressure rise generated by the pump is significantly reduced. Therefore, the pressure drop across the voids and gaps is significantly reduced, resulting in a significant reduction in the stabilizing force generated by the Lomakin effect.

[0008] To address the problem of rotor vibration, for example, caused by high hydraulic excitation within a multiphase pump, a hydrodynamic stabilization device for the rotor has been proposed in US 9,234,529. This device is constructed as a Lomakin damper lubricated by the process fluid, i.e., a damper operating based on the Lomakin effect. The damper includes a cover ring extending radially outward from the tip of the blades of a helical axial flow impeller. The cover ring is fixed to the impeller blades. This design is also known as a shrouded impeller. Therefore, a gap is formed between the rotating cover ring and the stationary portion of the pump housing surrounding the cover ring. The shrouded impeller can be fully shrouded or partially shrouded. A fully shrouded impeller has a cover ring that completely covers the impeller blades. A partially shrouded impeller has a cover ring that only covers a portion of the impeller (relative to the axial direction). The most efficient design is the fully shrouded impeller because it allows two-phase flow disturbances to be maintained within the impeller flow passages without generating varying radial forces on the rotor, as is the case with open impellers.

[0009] Because the local pressure on the high-pressure side or discharge side of a single impeller is higher than the local pressure on the low-pressure side or suction side, a portion of the process fluid is recirculated from the high-pressure side to the low-pressure side through the gap. Particularly for high pressure differentials across the gap, this fluid generates a hydrodynamic stabilizing layer that dampens the rotor based on the Lomakin effect. The forces generated by the Lomakin effect are directed to center the pump shaft and thus reduce rotor vibration. However, especially for small pressure differentials across the gap, the hydrodynamic forces can become unstable. In the extreme case of zero pressure differential across the gap, the unstable hydrodynamic flow mode in the gap is called Taylor-Couette flow.

[0010] For high pressure differentials across the gap, the rotor dynamics coefficients quantifying the hydrodynamic behavior of the fluid within the gap have direct rotor dynamics coefficients, which are significantly larger than indirect rotor dynamics coefficients. For small pressure differentials, the indirect rotor dynamics coefficients tend to become as large as or larger than the direct rotor dynamics coefficients. These indirect rotor dynamics coefficients represent unstable hydrodynamic fluid effects.

[0011] The hydrodynamic stabilizing device proposed in US 9,234,529 has proven to be very effective in practice, particularly for given operating conditions (e.g., low GVF operating conditions); however, room for improvement remains. It has been noted that, regarding rotor damping in multiphase pumps, as in the case of high GVF operating conditions, a small pressure difference across the gap between the cover ring and the stationary portion of the pump housing can have a significant negative impact on rotor dynamics. These instability effects increase as the gap (i.e., the width of the gap) is further reduced. This instability behavior occurs under high GVF operating conditions and for certain regions of the pump's operating envelope, resulting in a small pressure difference across the gap. However, increasing the gap reduces pump efficiency.

[0012] Therefore, there is a conflict between excessively reducing hydraulic efficiency by widening the gap and excessively reducing rotor dynamic stability by narrowing the gap, which may exceed the vibration acceptance criteria, especially for the aforementioned operating conditions.

[0013] Therefore, a solution is needed that allows for both: a design that, on the one hand, results in a small leakage flow above the cover ring, and on the other hand, does not degrade the pump's rotor dynamics stability, particularly in certain regions of the operating envelope. The ideal design provides rotor dynamics stabilization effects throughout the entire operating range, not just a portion of it. This entire operating range extends from low to high GVF values ​​and covers the entire operating envelope from low speed to high speed and from partial load to overload. Summary of the Invention

[0014] Therefore, the object of the present invention is to provide a multiphase pump with improved rotor damping, which significantly reduces rotor vibration without significantly reducing the hydraulic efficiency of the multiphase pump.

[0015] The subject matter of the invention that achieves this purpose is characterized by the features of the independent claims.

[0016] Therefore, according to the present invention, a multiphase pump for conveying multiphase process fluids is proposed, comprising a pump housing and a rotor disposed in the pump housing and configured for rotation about an axial direction, wherein the rotor includes a pump shaft and at least one impeller fixedly mounted on the pump shaft, wherein a stationary diffuser is adjacent to the impeller and disposed downstream of the impeller, wherein the impeller includes at least one blade, wherein each blade has a radially outer tip, and wherein the impeller includes a ring surrounding the impeller and disposed at the radially outer tip of the blade, wherein a passage is provided between the ring and a stationary portion configured to be stationary relative to the pump housing, the passage extending axially from an inlet to an outlet, wherein at least one vortex suppressor is provided at the passage, and wherein the vortex suppressor is configured and arranged to suppress vortices of the process fluid passing through the passage.

[0017] It has been found that the process fluid flowing in the passage between the stationary section and the rotating ring surrounding the impeller begins to swirl increasingly due to the entrainment effect of the rotating impeller. This has a negative impact on rotor dynamics. Particularly for small pressure differences in the passage, the flow through the passage between the stationary section and the rotating impeller tends to become unstable due to the formation of strong vortices. Impellers with rings are particularly sensitive to this vortex effect.

[0018] Therefore, according to the present invention, vortices in the passage are limited by providing at least one vortex suppressor to suppress vortices in the process fluid passing through the passage. This can be achieved by reducing inlet vortices (i.e., vortices present at the inlet of the passage) or by reducing vortex accumulation in the passage. Of course, both inlet vortices and vortex accumulation in the passage can also be reduced.

[0019] The fluid flowing into the passage has a high initial vortex because it is the fluid leaving the rotating impeller that has deflected into the passage. Therefore, the inlet vortex at the passage is roughly equivalent to the vortex of the fluid at the impeller outlet.

[0020] Inlet vortexes can be reduced by installing vortex suppressors at the inlet of the gap, and vortex accumulation in the gap can be prevented by installing grooves with vortex suppressors along the length of the gap. By placing at least one vortex suppressor at the passage, the clearance of the passage (i.e., the width of the passage in the radial direction) can be significantly reduced without affecting the rotor dynamic stability of the pump. Reducing the width of the passage in the radial direction reduces the flow through the passage and thereby improves the hydraulic efficiency of the multiphase pump.

[0021] According to a first embodiment of the present invention, the vortex suppressor is arranged at the inlet of the passage. Therefore, inlet vortices, which are vortices of process fluid already present at the inlet of the passage, can be significantly reduced.

[0022] In such embodiments where the vortex suppressor is arranged at the inlet of the passage, the vortex suppressor may also be arranged at the diffuser. Alternatively, the vortex suppressor may also be arranged at the stationary portion.

[0023] According to a second embodiment of the invention, the stationary portion includes a radially inner surface defining a passage relative to a radial direction perpendicular to the axial direction, wherein the radially inner surface is provided with a groove surrounding the pump shaft in a circumferential direction, and wherein the vortex suppressor is arranged in the groove. Preferably, the vortex suppressor extends over the entire length of the groove. The vortex suppressor arranged in the groove can significantly reduce vortex accumulation in the passage.

[0024] According to a third embodiment of the invention, a plurality of vortex suppressors are provided, namely a first vortex suppressor arranged at the inlet of the passage and at least one second vortex suppressor arranged in a groove surrounding the pump shaft in the circumferential direction, wherein the groove is arranged in the radially inner surface of the stationary portion, thereby defining the passage relative to a radial direction perpendicular to the axial direction. The third embodiment, including the first vortex suppressor and at least one second vortex suppressor, has the advantage of significantly reducing both inlet vortices at the inlet of the passage and vortex accumulation in the passage.

[0025] In the third embodiment, the first vortex suppressor is preferably arranged at the diffuser or at the stationary portion.

[0026] In a variation of the third embodiment, a plurality of second vortex suppressors are provided, each of which is arranged in a different trench.

[0027] According to a fourth embodiment of the invention, the ring surrounding the impeller includes a protrusion extending along the circumference of the ring, wherein the protrusion is configured to deflect at least a portion of the process fluid into the vortex suppressor in the groove. Because the protrusion deflects at least a portion of the flow through the passage into the groove with the vortex suppressor, the efficiency of the vortex suppressor is enhanced.

[0028] As a preferred embodiment, the protrusion is aligned with the groove relative to the axial direction. Therefore, the protrusion is completely surrounded or covered by the groove. The protrusion may also extend into the groove relative to the radial direction.

[0029] According to another variation that can be combined with all embodiments, the ring is configured to form a labyrinth seal between the impeller and the stationary portion.

[0030] Furthermore, a preferred design is that the multiphase pump comprises multiple stages, each stage including an impeller and a diffuser, wherein at least one of the impellers includes a ring surrounding the impeller, and wherein the vortex suppressor is disposed at the passage defined by the ring. Therefore, for embodiments where the multiphase pump is designed as a multistage pump, it is unnecessary, but certainly possible, for all impellers to be configured as shrouded impellers with rings surrounding the impellers. In some embodiments, only one of the impellers is provided with a ring; in other embodiments, all impellers are surrounded by corresponding rings; and in still other embodiments, more than one, but fewer than all, impellers are surrounded by corresponding rings. Preferably, for each impeller provided with a ring surrounding the impeller, at least one vortex suppressor is disposed at the passage defined by the corresponding ring.

[0031] As another particularly preferred measure applicable to all embodiments, the multiphase pump is configured as a helical axial flow pump with a helical axial flow impeller.

[0032] The multiphase pump according to the invention may further include a drive unit disposed in a pump housing and configured to drive a rotor, wherein the multiphase pump is preferably configured as a vertical pump with the pump shaft extending in the direction of gravity.

[0033] In other configurations, the multiphase pump according to the invention can be configured as a horizontal pump with the pump shaft extending perpendicular to the direction of gravity. Such embodiments of horizontal pumps can be used, for example, at the top side of an offshore platform, on a floating production storage and offloading unit (FPSO), or on shore.

[0034] In particular, the multiphase pump according to the invention can be configured as a submersible pump and is preferably configured for installation on the seabed.

[0035] In view of another preferred application, the multiphase pump according to the invention can be configured as a helical axial flow multistage horizontal pump with an external drive unit, i.e., the drive unit is not arranged inside the pump housing.

[0036] Furthermore, it is particularly preferred that the multiphase pump according to the invention is configured to transport multiphase process fluids having a gas volume fraction of 0% to 100%, i.e., the multiphase fluid is configured to operate at all GVF values ​​from 0% (pure liquid) to 100% (pure gas).

[0037] Other advantageous features and embodiments of the invention will become apparent from the dependent claims. Attached Figure Description

[0038] The invention will be explained in more detail below with reference to embodiments thereof and the accompanying drawings. As illustrated in the schematic diagrams:

[0039] Figure 1 A schematic cross-sectional view of a first embodiment of the multiphase pump according to the present invention.

[0040] Figure 2 Perspective view of a helical axial flow impeller (without rings).

[0041] Figure 3 :picture Figure 2 Same, but it's a cross-sectional view and includes a ring.

[0042] Figure 4 : Schematic illustration of the impeller and diffuser of the first embodiment.

[0043] Figure 5 :picture Figure 4 It is the same, but it is a variation of the first embodiment.

[0044] Figure 6 : Figure 4 The embodiments shown follow Figure 4 The cross-sectional view perpendicular to the pump shaft, showing the cutting line VI-VI.

[0045] Figure 7 :picture Figure 4 The same applies, but specifically to a second embodiment of the multiphase pump according to the present invention.

[0046] Figure 8 : Figure 7 The second embodiment shown follows Figure 7 A cross-sectional view perpendicular to the pump shaft, showing the cutting lines VIII-VIII.

[0047] Figure 9 :picture Figure 4 The same applies, but specifically to a third embodiment of the multiphase pump according to the present invention.

[0048] Figure 10 :picture Figure 9 It is the same, but it is a first variation of the third embodiment.

[0049] Figure 11 :picture Figure 9 It is the same, but it is a second variation of the third embodiment.

[0050] Figure 12 :picture Figure 4 The same applies, but specifically to the fourth embodiment of the multiphase pump according to the present invention.

[0051] Figures 13-15 :picture Figure 4 The same applies, but other measures applicable to all embodiments are shown, and

[0052] Figure 16Cross-sectional view of the construction of a multiphase pump according to the present invention, having a back-to-back design. Detailed Implementation

[0053] Figure 1 A schematic cross-sectional view of a first embodiment of a multiphase pump according to the present invention is shown, generally indicated by reference numeral 1. The pump 1 is designed as a centrifugal pump for conveying multiphase process fluids. The pump 1 has a pump housing 2, and a rotor 3 is arranged within the pump housing 2. The rotor 3 is configured to rotate about an axial direction A. A drive unit 4 is provided to rotate the rotor 3. Figure 1 In the embodiment shown, the drive unit 4 is also arranged inside the pump housing 2. It goes without saying that in other embodiments of the multiphase pump, the drive unit is arranged outside the pump housing 2, for example, in a separate motor housing.

[0054] exist Figure 1 In the first embodiment shown, both the rotor 3 and the drive unit 4 are arranged within the pump housing 2. The pump housing 2 is designed as a pressure housing, configured to withstand pressure generated by the multiphase pump 1 and pressure applied to the pump 1 by the environment. The pump housing 2 may include several housing sections connected to each other to form a pump housing 2 surrounding the rotor 3 and the drive unit 4. Alternatively, both the rotor housing and a separate motor housing may be inserted into the pump housing 2. Figure 1 In the embodiment shown, the pump housing 2 is constructed as an airtight pressure housing to prevent any leakage to the external environment.

[0055] In the following description, reference is made by way of example to a multiphase pump 1 designed and adapted for important applications in the oil and gas industry as a subsea multiphase pump 1. Specifically, the multiphase pump 1 is configured for installation on the seabed, i.e., for use below the water surface, particularly to depths of 500 m, 1000 m, or even more than 2000 m below the ocean surface. In such applications, the multiphase process fluid is typically a mixture containing hydrocarbons that must be pumped from an oil field, for example, to a processing unit below or above the water surface or on shore. The multiphase mixture constituting the multiphase process fluid to be transported may include a liquid phase, a gas phase, and a solid phase, wherein the liquid phase may include crude oil, seawater, and chemicals; the gas phase may include methane, natural gas, etc.; and the solid phase may include sand, silt, and small stones, while the multiphase pump 1 remains undamaged during the pumping of the multiphase mixture.

[0056] It must be understood that the present invention is not limited to this specific example, but generally relates to multiphase pumps. The multiphase pump 1 can also be configured for top-side applications, such as for onshore installation or mounting on oil platforms, particularly unmanned platforms. Furthermore, the pump 1 according to the invention can also be used in applications outside the oil and gas industry.

[0057] The pump housing 2 of the multiphase pump 1 includes: a pump inlet 21 through which the multiphase process fluid enters the pump 1; and a pump outlet 22 for discharging process fluid at a pressure increased compared to the pressure of the process fluid at the pump inlet 21. Typically, the pump outlet 22 is connected to a conduit (not shown) for delivering the pressurized process fluid to another location. The pressure of the process fluid at the pump outlet 22 is referred to as the "high pressure," while the pressure of the process fluid at the pump inlet 21 is referred to as the "low pressure." A typical value for the difference between the high and low pressures is, for example, 100 to 200 bar (10–20 MPa), particularly for low GVF conditions.

[0058] The rotor 3 of the multiphase pump 1 includes a pump shaft 5 extending from the drive end 51 of the pump shaft 5 to the non-drive end 52. The pump shaft 5 is configured to rotate about an axial direction A, which is defined by the longitudinal axis of the pump shaft 5.

[0059] The rotor 3 further includes at least one impeller 31, which is fixedly mounted on the pump shaft 5 in an anti-torsional manner. Figure 1 In the embodiment shown, multiple impellers 31 (i.e., five impellers 31) are arranged in series on the pump shaft 5, that is, the multiphase pump 1 is configured as a five-stage pump. Of course, the number of five stages is merely exemplary. In other embodiments, the multiphase pump 1 may include more than five stages (e.g., ten or twelve stages) or less than five stages (e.g., four or two stages) or a single stage with only one impeller 31.

[0060] Multiple impellers 31 are arranged in series and configured to increase the pressure of the fluid from low pressure to high pressure.

[0061] The drive unit 4 is configured to apply torque to the drive end 51 of the pump shaft 5 so as to drive the pump shaft 5 and the impeller 31 to rotate about the axial direction A.

[0062] The multiphase pump 1 is constructed as a vertical pump 1, which means that during operation, the pump shaft 5 extends in a vertical direction, which is the direction of gravity. Therefore, the axial direction A is consistent with the vertical direction.

[0063] In other embodiments (see Figure 16 The multistage pump 1 can be constructed as a horizontal pump, which means that during operation, the pump shaft 5 extends horizontally, i.e., the axial direction A is perpendicular to the direction of gravity.

[0064] The direction perpendicular to the axial direction A is called the radial direction. The term "axial" or "axially" is used in the general sense of "along the axial direction" or "relative to the axial direction." Similarly, the term "radial" or "radially" is used in the general sense of "along the radial direction" or "relative to the radial direction." In the following text, relative terms concerning position (such as "above," "below," "upper," "lower," "top," or "bottom") refer to the normal operating position of pump 1. Figure 1 The multiphase pump 1 is shown in its normal operating position.

[0065] Refer to this usual orientation during operation, and as Figure 1 As shown, the drive unit 4 is located above the rotor 3. However, in other embodiments, the rotor 3 may be located on top of the drive unit 4.

[0066] like Figure 1 As can be seen, the multiphase pump 1 is designed with all impellers 31 arranged in a straight line. In this straight-line arrangement, all impellers 31 are arranged such that the axial thrust generated by each individual rotating impeller 31 is guided entirely in the same direction; that is, in Figure 1 In the axial direction A, downwards. The flow of fluid from pump inlet 21 (low pressure) to pump outlet 22 (high pressure) is always guided in the same direction (i.e., upwards), and not as, for example, in a back-to-back arrangement (see...). Figure 16 The process flow changes in that manner. In each case, a stationary diffuser 32 exists between the impellers 31 of adjacent stages to guide the flow of process fluid discharged from a particular impeller 31 to the impeller 31 of the next stage. Thus, viewed in the axial direction A, in each case, a diffuser 32 is arranged between two adjacent impellers 31, the diffuser 32 being stationary relative to the pump housing 2. Each stage of the multiphase pump 1 includes an impeller 31 and a diffuser 32, wherein the diffuser 32 of the corresponding stage is adjacent to the impeller 31 relative to the axial direction A and is arranged downstream of the impeller 31 of the corresponding stage.

[0067] According to a preferred design, the multiphase pump 1 is configured as a helical axial flow pump with a helical axial flow impeller 31. Both the helical axial flow impeller 31 and the helical axial flow multiphase pump 1 are known in the art. Figure 2 A perspective view of two helical axial flow impellers 31 is shown, with a diffuser 32 inserted between the two impellers 31. Figure 2 In this section, half of the pump housing 2 has been removed to make the helical axial flow impeller 31 visible. Furthermore, in... Figure 2 In order to better observe the impeller 31, the ring 30 surrounding the impeller 31 is not shown (see [reference]). Figure 3The helical axial flow impeller 31 has at least one blade 38 that extends helically around the hub of the impeller 31 or the pump shaft 5. In many embodiments, each helical axial flow impeller 31 includes a plurality of blades 38 (e.g., five blades 38), each of which extends helically around the pump shaft 5 or the hub of the impeller 31. Each blade 38 has a radially outward tip 381.

[0068] in addition, Figure 3 A cross-sectional view shows two impellers 31 and a diffuser 32 between the two impellers 31, with a cut line extending in the axial direction A and passing through the pump shaft 5. Figure 3 As best seen in the image, the impeller 31 is fixed to the pump shaft 5 in an anti-torsional manner, for example by means of a key lock, and the diffuser 32 is fixed to the pump housing 2 or to a portion stationary relative to the pump housing 2. Furthermore, as... Figure 3 As shown, each impeller includes a ring 30 surrounding the corresponding impeller 31. The ring 30 is arranged at the radially outer tip 381 of the blade 38, such that the ring 30 forms the radially outer surface of the impeller 31. The ring 30 is fixed relative to the outer tip 381, such that the ring 30 is connected to the impeller 31 in a torsion-resistant manner. The design of the impeller 31 with the ring 30 arranged along the radially outer tip 381 of the blade 38 is also referred to as a "shroud-type impeller" 31.

[0069] Ring 30 has an axial length AL, which is the extension of ring 30 in the axial direction A. For example, regarding... Figure 3 As shown in the example, the axial length AL of the ring 30 can be at least approximately equal to the extension of the impeller blade 38 in the axial direction A, such that the impeller blade 38 is completely covered by the ring 30. It must be noted that in other embodiments, the axial length AL of the ring 30 can be less than the extension of the impeller blade 38 in the axial direction A, such that the blade 38 is not completely covered by the ring 30, but rather protrudes from the ring 30 relative to the axial direction A. The ring 30 can be designed as a wear ring 30.

[0070] A ring 30 is surrounded by a stationary portion 39, forming a passage 10 between the radially outer surface of the ring 30 and the stationary portion 39. The stationary portion 39 is configured to be stationary relative to the pump housing 2. The passage 10 forms an annular gap between the radially outer surface of the ring 30 and the stationary portion 39. The passage 10 extends axially from an inlet 11 to a outlet 12. The inlet 11 is located on the outlet side of the impeller 31, where higher pressure dominates, and the outlet 12 is located on the suction side of the impeller 31, where lower pressure dominates during pump 1 operation. Therefore, a leakage flow of the process fluid enters the passage 10 at the inlet 11, passes through the passage 10, and exits the passage 10 at the outlet 12. Thus, this leakage flow flows in the opposite direction to the main flow of the process fluid through the pump 1.

[0071] According to the invention, at least one vortex suppressor 6 is provided at the passage 10, wherein the vortex suppressor 6 is constructed and arranged to suppress vortices or pre-rotation of the process fluid 10 passing through the passage 10. The vortex suppressor 6 may be arranged to suppress inlet vortices of the process fluid at the inlet 11 of the passage 10, or to suppress vortex accumulation in the passage 10. As will be explained later, in embodiments including more than one vortex suppressor 6, both inlet vortices at the inlet 11 of the passage 10 and vortex accumulation in the passage 10 may also be reduced.

[0072] At least one vortex suppressor 6 may be arranged at the inlet 11 of the passage 10 or in the stationary portion 39 between the inlet 11 and the outlet 12 of the passage. If at least one vortex suppressor 6 is arranged at the inlet 11 of the passage 10, the vortex suppressor 6 may be located at the diffuser 32, more specifically at the axial end of the diffuser 32 facing the impeller 31, or the vortex suppressor 6 may be located at the stationary portion 39. Different embodiments regarding the arrangement of at least one vortex suppressor 6 will be explained below.

[0073] In other embodiments of the multiphase pump 1, the impeller 31 may not be configured as a helical axial flow impeller, but rather as, for example, a semi-axial flow impeller.

[0074] To at least partially balance the axial thrust generated by the impeller 31 during the operation of the multiphase pump 1, it is preferable that the multiphase pump 1 includes at least one balancing device. Figure 1 In the illustrated embodiment, the balancing device includes a balancing drum 7 (also referred to as a throttling bushing). The balancing drum 7 is fixedly connected to the pump shaft 5 in an anti-torsional manner, i.e., the balancing drum 7 is part of the rotor 3. Viewed along the flow direction of the process fluid, the balancing drum 7 is positioned behind the diffuser 32, the final stage that guides the process fluid to the pump outlet 22, i.e., between the final stage diffuser 32 and the drive end 51 of the pump shaft 5. The balancing drum 7 defines a front side and a rear side. The front side is the side facing the final stage diffuser 32. The rear side is the side facing the drive unit 4. The balancing drum 7 is surrounded by a stationary balancing portion 26, such that a pressure relief passage 73 is formed between the radially outer surface of the balancing drum 7 and the stationary balancing portion 26. The stationary balancing portion 26 is configured to be stationary relative to the pump housing 2. The pressure relief passage 73 forms an annular gap between the outer surface of the balancing drum 7 and the stationary balancing portion 26 and extends from the front side to the rear side.

[0075] A balancing line 9 is provided to recirculate the process fluid from the rear side of the balancing drum 7 to the low-pressure side at the pump inlet 21. Specifically, the balancing line 9 connects the rear side to the low-pressure side of the multiphase pump 1, where low pressure (i.e., the pressure at the pump inlet 21) is dominant. Therefore, a portion of the pressurized fluid is transferred from the substantially high-pressure-dominated front side through the pressure relief passage 73 to the rear side, enters the balancing line 9, and is recirculated to the low-pressure side of the multiphase pump 1. The balancing line 9 forms a flow connection between the rear side of the balancing drum 7 and the low-pressure side at the pump inlet 21. The balancing line 9 can be configured as follows: Figure 1 The arrangement shown is outside the pump housing 2. In other embodiments, the balancing line 9 can be designed as an internal line extending entirely within the pump housing 2.

[0076] Due to the balancing line 9, except for the small pressure drop caused by the balancing line 9, the dominant pressure at the rear is basically the same as the low pressure that dominates at the pump inlet 21.

[0077] The forward-facing axial surface of the balancing drum 7 is exposed to a pressure substantially equal to the high pressure at pump outlet 22. At the rear of the balancing drum 7, a low pressure predominates primarily during pump 1 operation. Therefore, the pressure drop across the balancing drum 7 is essentially the difference between the high and low pressures.

[0078] The pressure drop on the balancing drum 7 results in an upward force directed along the axial direction A, which in turn counteracts the downward axial thrust generated by the impeller 31.

[0079] The multiphase pump 1 further includes multiple bearings. A first radial bearing 53, a second radial bearing 54, and an axial bearing 55 are provided to support the pump shaft 5. The first radial bearing 53 (which is...) Figure 1 The upper bearing (the one in the middle) is located adjacent to the drive end 51 of the pump shaft 5 and is positioned between the balance drum 7 and the drive unit 4. The second radial bearing 54 (which is...) Figure 1 The lower bearing (of the first stage) is arranged between the impeller 31 of the first stage and the non-drive end 52 of the pump shaft 5, or at the non-drive end 52. An axial bearing 55 is arranged between the impeller 31 of the last stage and the first radial bearing 53. Bearings 53, 54, and 55 are configured to support the pump shaft 5 in both the axial and radial directions. Radial bearings 53 and 54 support the pump shaft 5 radially, and axial bearing 55 supports the pump shaft 5 axially. The first radial bearing 53 and axial bearing 55 are arranged such that the first radial bearing 53 is closer to the drive unit 4, and the axial bearing 55 faces the balance drum 7. Alternatively, the positions of the first radial bearing 53 and the axial bearing 55 can be interchanged, i.e., the first radial bearing 53 can be arranged between the axial pump bearing 55 and the balance drum, such that the axial bearing 55 is closer to the drive unit 4.

[0080] The configuration of radial bearing 53 at the drive end 51 of shaft 5 and radial bearing 54 at the non-drive end 52 of pump shaft is called bearing arrangement because all impellers 31 are arranged between the two radial bearings 53 and 54.

[0081] It should be noted that in other embodiments, the multiphase pump 1 may be configured, for example, in a cantilever configuration with only one radial bearing.

[0082] Radial bearings (e.g., first or second radial bearings 53 or 54) are also called “journal bearings”, and axial bearings (e.g., axial bearing 55) are also called “thrust bearings”. The first radial bearing 53 and the axial bearing 55 can be constructed as separate bearings, but the first radial bearing 53 and the axial bearing 55 can also be constructed as a single combined radial and axial bearing that supports the pump shaft 5 in both the radial and axial directions.

[0083] The second radial bearing 54 supports the pump shaft 5 in the radial direction. Figure 1 In the embodiment shown, no axial bearing is provided at the non-drive end 52 of the pump shaft 5. Of course, in other embodiments, an axial bearing for the pump shaft 5 may be provided at the non-drive end 52. In embodiments where an axial bearing is provided at the non-drive end 52 of the pump shaft 5, a second axial bearing may be provided at the drive end 51, or the drive end 51 may be configured without an axial bearing.

[0084] Preferably, at least radial bearings 53 and 54 are configured as hydrodynamic bearings, and even more preferably as tilting bearings 53 and 54. Additionally, axial bearing 55 can also be configured as a hydrodynamic bearing, and even more preferably as a tilting bearing. Of course, the first radial bearing 53 and the second radial bearing 54 can each be configured as a fixed multi-bladed hydrodynamic bearing.

[0085] The drive unit 4 includes an electric motor 41 and a drive shaft 42 extending along the axial direction A. To support the drive shaft 42, a first radial drive bearing 43, a second radial drive bearing 44, and an axial drive bearing 45 are provided, wherein the second radial drive bearing 44 and the axial drive bearing 45 are arranged above the electric motor 41 relative to the axial direction A, and the first radial drive bearing 43 is arranged below the electric motor 41. The electric motor 41, arranged between the first and second radial drive bearings 43 and 44, is configured to rotate the drive shaft 42 about the axial direction A. The drive shaft 42 is connected to the drive end 51 of the pump shaft 5 by means of a coupling 8 for transmitting torque to the pump shaft 5.

[0086] The electric motor 41 of the drive unit 4 can be configured as a cable-wound motor. In a cable-wound motor, the individual wires of the motor stator forming the coils for generating the electromagnetic field driving the motor rotor are each insulated, allowing the motor stator to be submerged, for example, by a barrier fluid. Alternatively, the electric motor 41 can be configured as a closed motor. When the electric drive 41 is configured as a closed motor, the annular gap between the motor rotor and the motor stator of the electric motor 41 is radially outwardly defined by a can that hermetically seals the motor stator relative to the motor rotor and the annular gap. Therefore, any fluid flowing through the gap between the motor rotor and the motor stator cannot enter the motor stator. When the electric motor 41 is designed as a closed motor, a dielectric cooling fluid can circulate through the hermetically sealed motor stator to cool it.

[0087] Preferably, the electric motor 41 is configured as a permanent magnet motor or an induction motor. To supply energy to the electric motor 41, a generator (not shown) is provided at the pump housing 2 for receiving the power cable, which supplies power to the electric motor 41.

[0088] The electric motor 41 can be designed to operate in conjunction with a variable frequency drive (VFD), wherein the speed (i.e., rotational frequency) of the motor 41 can be adjusted by changing said frequency and / or the voltage supplied to the electric motor 41. However, the electric motor 41 can also be constructed differently, for example, as a single-speed or single-frequency drive.

[0089] Drive shaft 42 is connected to drive end 51 of pump shaft 5 by means of coupling 8 to transmit torque to pump shaft 5. Preferably, coupling 8 is configured as a flexible coupling 8 that connects drive shaft 42 to pump shaft 5 in a torsional manner, but allows relative lateral (radial) and / or axial movement between drive shaft 42 and pump shaft 5. Thus, flexible coupling 8 transmits torque, but transmits little or no lateral vibration. Preferably, flexible coupling 8 is configured as a mechanical coupling 8. In other embodiments, the flexible coupling may be designed as a magnetic coupling, a hydrodynamic coupling, or any other coupling suitable for transmitting torque from drive shaft 42 to pump shaft 5.

[0090] As already described, in other embodiments, the drive unit 4 may be housed in a separate motor housing, which, for example, is located outside the pump housing 2.

[0091] The multiphase pump 1 further includes two sealing units 50 for sealing the pump shaft 5 to prevent leakage of process fluid along the pump shaft 5. The sealing units 50 prevent process fluid from entering the drive unit 4 and the bearings 53, 54, and 55. One of the sealing units 50 is arranged between the balance drum 7 and the axial bearing 55, and the other sealing unit 50 is arranged between the impeller 31 of the first stage and the second radial bearing 54. Preferably, each sealing unit 50 includes a mechanical seal. Mechanical seals are well known in the art in many different embodiments and therefore do not require detailed explanation. In principle, a mechanical seal is a seal for a rotating shaft and includes a rotor fixed to and rotating with the pump shaft 5 and a stationary stator fixed relative to the pump housing 2. During operation, the rotor and stator slide along each other (typically with liquid between them) to provide a sealing effect to prevent process fluid from escaping to the environment or entering the drive unit 4 of the pump 1.

[0092] In other embodiments, the multiphase pump 1 may be configured as an unsealed pump, for example, without any mechanical seals.

[0093] The arrangement of at least one vortex suppressor 6 will now be explained in more detail with the aid of several embodiments and variations. In this explanation, only the construction of the ring 30 and the arrangement of the vortex suppressor 6 will be discussed in more detail. The previous description of the first embodiment of the multiphase pump 1 applies in the same or similar manner to all these embodiments and variations.

[0094] Figure 4 The first embodiment shows two impellers 31 and two diffusers 32 in a schematic cross-sectional view, with the cut line extending along the axial direction A and passing through the pump shaft 5. In this embodiment, only one vortex suppressor 6 exists in each stage, arranged in the stationary portion 39 surrounding the impeller 31. The vortex suppressor 6 is arranged at the inlet 11 of the passage 10 relative to the axial direction A. It is possible that the vortex suppressor 6 is arranged aligned with the axial end of the ring 30 defining the inlet 11, or the vortex suppressor 6 is arranged adjacent to said axial end of the ring 30.

[0095] The vortex suppressor can be designed, for example, in any manner known in the art. Figure 6 Press along Figure 4 The cross-sectional view perpendicular to the pump shaft 5, shown by the cutting line VI-VI in the figure, is illustrated. Figure 4An example of the design of the vortex suppressor 6 is provided. The vortex suppressor 7 includes a plurality of notches 63 disposed on the radially inner surface of the stationary portion 39. Each notch 63 extends in the radial direction. The notches 63 are preferably distributed equidistantly on a circle along the entire radially inner surface of the stationary portion 39. Thus, in each case, there is a rod 64 between two adjacent notches 63, which also extends in the radial direction. The notches 63 and the rod 64 can be produced, for example, by drilling holes in the radially inner surface of the stationary portion 39 or by providing notches 63 at the axial ends of the stationary portion 39. Of course, Figure 6 The geometry of the notch 63 and rod 64 shown is merely exemplary. The rod 64 may also have, for example, a cuboid or cube shape. All suitable methods, such as machining, can be used to manufacture the vortex suppressor 6 with the notch 63 and rod 64.

[0096] Figure 5 Similar to Figure 4 The illustration shows a variation of the first embodiment. According to this variation, the vortex suppressor 6 is arranged at the diffuser 32. More specifically, the vortex suppressor 6 is arranged at the axial end of the diffuser shroud 321 forming the radial outer surface of the diffuser 32. The vortex suppressor 6 is disposed in the axial end of the diffuser shroud 321 located at the inlet 11 of the passage 10.

[0097] Figure 7 Similar to Figure 4 The illustration shows a second embodiment. The second embodiment also includes only one vortex suppressor 6. The vortex suppressor 6 is arranged in a groove 60, which is disposed in the radially inner surface of the stationary portion 39. The groove 60 is configured as an annular groove 60 that completely surrounds the pump shaft 5 in the circumferential direction. The groove 60 has a depth T, which is the radial extension of the groove 60. The groove 60 has a width GL, which is the axial extension of the groove 60 in the axial direction A. A notch 63 and a rod 64 of the vortex suppressor 6 are arranged inside the groove 60, particularly at the wall of the groove 60 relative to the axial direction A. The rod 64 is arranged such that it is flush with the radially inner surface of the stationary portion 39. Regarding its radial extension, the rod 64 is shorter than the depth T of the groove 60, such that the rod 64 does not extend to the bottom of the groove 60. Regarding its extension in the axial direction, the rod 64 is shorter than the width GL of the groove 60, such that the rod 64 does not extend into the other walls of the groove 60 that define the groove 60 relative to the axial direction A.

[0098] In other embodiments, the rod 64 extends radially to a depth T of the groove 60, such that the rod 64 extends to the bottom of the groove 60.

[0099] To better understand, Figure 8 Show along Figure 7A cross-sectional view perpendicular to pump shaft 5, showing cutting lines VIII-VIII. (See diagram below.) Figure 8 As best seen, rod 64 has a cuboid, particularly a cubic, shape. This shape is merely exemplary. In other embodiments, the rod may have different shapes, such as tapered shapes, like trapezoids.

[0100] Now for reference Figure 9 – Figure 12 Other embodiments including more than one vortex suppressor 6 will be described. It should be noted that the explanation of embodiments having only one vortex suppressor 6 is also adapted in a similar manner to embodiments having more than one vortex suppressor.

[0101] Figure 9 Similar to Figure 4 The illustration shows a third embodiment. Each stage of the third embodiment includes multiple vortex suppressors, specifically two vortex suppressors: a first vortex suppressor 61 arranged at the inlet 11 of the passage 10 and a second vortex suppressor 62 arranged in a groove 60 surrounding the pump shaft 5 in the circumferential direction, wherein the groove 60 is disposed in the radial inner surface of the stationary portion 39 between the inlet 11 and the outlet 12 of the passage 10.

[0102] A first vortex suppressor 61 is disposed at the diffuser 32. More specifically, the first vortex suppressor 61 is disposed at the axial end of the diffuser shroud 321 forming the radial outer surface of the diffuser 32. The first vortex suppressor 61 is disposed in the axial end of the diffuser shroud 321 located at the inlet 11 of the passage 10.

[0103] The second vortex suppressor 62 has been referenced. Figure 7 A similar arrangement is provided in trench 60.

[0104] Figure 10 Press and Figure 9 A similar illustration shows a first variation of the third embodiment. According to this variation, the first vortex suppressor 61 is aligned with the previously referenced... Figure 4 A similar arrangement is described in the static section 39.

[0105] Figure 11 Press and Figure 9 A similar illustration shows a second variation of the third embodiment. According to this variation, two second vortex suppressors 62 are provided in each stage, each of the second vortex suppressors 62 being arranged in a different groove 60. Thus, two grooves 60 spaced apart from each other relative to the axial direction A are provided, wherein each groove 60 is arranged in the radially inner surface of the stationary portion 39 between the inlet 11 and the outlet 12 of the passage 10. In each of the grooves 60, one of the second vortex suppressors 62 is provided, each of the second vortex suppressors 62 being as already referenced... Figure 7 Designed as explained. In other embodiments (e.g.) Figure 14 More than two second vortex suppressors 62 can be set.

[0106] Figure 12 Similar to Figure 4 The illustration shows the fourth embodiment. Regarding the vortex suppressors 61 and 62, the fourth embodiment is similar to... Figure 10 The first variation of the third embodiment shown. The fourth embodiment also includes a first vortex suppressor 61 arranged in the stationary portion 39 at the inlet 11 of the passage 10 and a second vortex suppressor 62 arranged in a groove 60 surrounding the pump shaft 5 in the circumferential direction, wherein the groove 60 is provided in the radial inner surface of the stationary portion 39 between the inlet 11 and the outlet 12 of the passage 10.

[0107] In the fourth embodiment, the ring 30 surrounding the impeller at the radially outer tip 381 of the blade 38 includes a protrusion 301 extending along the circumference of the ring 30, wherein the protrusion 301 is configured to at least partially deflect the process fluid into the groove 60 where the second vortex suppressor 62 is arranged. By deflecting at least a portion of the process fluid from the passage 10 into the groove 60 where the second vortex suppressor 62 is arranged, the reduction of vortices or the reduction of vortex accumulation in the passage 10 can be further increased.

[0108] In such Figure 12 In the axial cross-sectional view shown, the protrusion 301 may have a quadrilateral cross-section. In other embodiments, the protrusion may have other cross-sections, such as a circular cross-section, a trapezoidal cross-section, or a square cross-section.

[0109] As another advantageous measure, such as Figure 12 As shown, the protrusion 301 is aligned with the groove 60 relative to the axial direction A. Preferably, as viewed in the radial direction, the groove 60 completely covers the protrusion 301. For this purpose, the width GL of the groove 60 (see...) Figure 7 It is at least as large as, and preferably larger than, the extension of the protrusion 301 in the axial direction A. Furthermore, it is preferred that the protrusion 301 has an extension in the radial direction, which is as large as the extension of the protrusion 301 into the groove 60.

[0110] In other embodiments, with Figure 11 Similarly shown, multiple grooves 60 with a second vortex suppressor 62 are provided. In such embodiments, for more than one of the grooves 60, they can be arranged as shown in the reference. Figure 12 The protrusion 301 at the ring 30 is set in a similar manner. For each groove 60, a specific protrusion 301 may also be provided at the ring 30.

[0111] Now for reference Figures 13-15 Other advantageous measures are explained, which apply to all embodiments and variations explained above. Figures 13-15 Each of them shows something similar to Figure 4 The illustration in the diagram.

[0112] like Figure 13 As shown, only a first vortex suppressor 61 is provided, which is arranged in the stationary portion 39 at the inlet 11 leading to the passage 10. The ring 30 covering the impeller 31 at the radially outer end 381 of the blade 38 is constructed as a labyrinth seal with bosses 302 and channels 303. As is known from the design of labyrinth seals, each boss 302 is designed as an annular ring extending circumferentially around the ring 30 on the radially outer surface and protruding in the radial direction, such that a channel 303 is formed between each pair of adjacent bosses 302. Through this labyrinth design of the ring 30, the passage 10 is divided into a tight-sealed area between each of the bosses 302 and the stationary portion 39, and a wider area between each channel 303 and the stationary portion 39. By this measure, the total tight length of the passage 10 (which is the sum of the extensions of all tight areas in the axial direction A) can be reduced, thereby significantly reducing the resistance in the passage 10. Reducing the resistance in the passage 10 improves the efficiency of the pump 1, especially the hydraulic efficiency.

[0113] Figure 14 A design with a first vortex suppressor 61 and three second vortex suppressors 62 is shown. The first vortex suppressor 61 is arranged in the stationary portion 39 at the inlet 11 leading to the passage 10, and each of the three second vortex suppressors 62 is arranged in a different groove of three grooves 60. The ring 30 is designed as a labyrinth seal with bosses 302 and channels 303 arranged on the radially outer surface of the ring 30. Figure 13 In comparison, the extension of the boss 302 in the axial direction A is significantly smaller than the extension of the channel 303 in the axial direction. Therefore, further reducing the total compact length of the passage 10 (which is the sum of the extensions of all compact regions in the axial direction A) results in even lower resistance in the passage 10.

[0114] according to Figure 15 As shown in the figure, the second vortex suppressor 62 (three second vortex suppressors 62 in each stage) is not arranged in the groove 60, but is disposed in the radial inner surface of the stationary portion 39 which does not have any grooves. The second vortex suppressor 62 can be manufactured, for example, by machining.

[0115] Figure 16A cross-sectional view of the construction of a multiphase pump 1 according to the invention, having a back-to-back design, is shown. In the following description of the back-to-back construction, the differences from the first embodiment of the multiphase pump 1 are explained in more detail only. Reference is made to the explanation of the first embodiment of the multiphase pump 1 and to... Figure 2 – Figure 15 The explanation applies in the same or similar manner to the back-to-back design of the multiphase pump 1. The same reference numerals denote the same features or functionally equivalent features explained with reference to the first embodiment.

[0116] It is important to note that, Figure 16 In the middle, the passage 10 between the ring 30 and the stationary part 39, as well as the vortex suppressor 6 and / or the first vortex suppressor 61 and / or the second vortex suppressor 62, are not obvious due to their large proportion; however, these components 10, 30, 39, 6, 61, 62 can be constructed in any manner described herein.

[0117] The multiphase pump 1 with a back-to-back design is also constructed as a helical axial flow multistage pump 1 with multiple helical axial flow impellers 31 (see also...) Figure 2 and Figure 3 Furthermore, the multiphase pump 1 is constructed as a horizontal pump 1, which means that during operation, the pump shaft 5 extends horizontally, i.e., the axial direction A is perpendicular to the direction of gravity. The drive unit 4 is not arranged inside the pump housing 2, but is arranged in a separate motor housing (details not shown).

[0118] A first radial bearing 53 at the drive end 51 of the pump shaft 5 is arranged in a first bearing housing 531, which is fixedly mounted to the pump housing 2 and can therefore also be considered part of the pump housing 2. A second radial bearing 54 at the non-drive end 52 of the pump shaft 5 is arranged in a second bearing housing 541, which is fixedly mounted to the pump housing 2 and can therefore also be considered part of the pump housing 2. An axial bearing 55 is arranged at the non-drive end 52 of the pump shaft 2 and can be arranged within the second bearing housing 541.

[0119] Figure 16 The multistage multiphase pump 1 shown has eight stages, each stage including an impeller 31 and a diffuser 32, as described above. Figure 16 The figure is indicated by the reference numeral K in the attached diagram.

[0120] like Figure 16As can be seen, the multiple impellers 31 include a first group of impellers 33 and a second group of impellers 34, wherein the first group of impellers 33 and the second group of impellers 34 are arranged back-to-back. The first group of impellers 33 includes the first stage impeller 31 (the first stage is the stage immediately adjacent to the pump inlet 2) and the second, third, and fourth stage impellers 31. The second group of impellers 34 includes the last stage impeller 31 (the last stage is the stage immediately adjacent to the pump outlet 22) and the fifth, sixth, and seventh stage impellers 31.

[0121] In other embodiments, the first set of impellers may include a different number of impellers than the second set of impellers. Of course, eight stages are exemplary. In other embodiments, there may be more or fewer than eight stages.

[0122] In a back-to-back arrangement, the first set of impellers 33 and the second set of impellers 34 are arranged such that the axial thrust generated by the action of the rotating first set of impellers 33 is guided in the opposite direction to the axial thrust generated by the action of the rotating second set of impellers 34. Figure 16 In the diagram, the multiphase process fluid enters the multistage pump 1 through pump inlet 21 located on the left, passes through stage one (first stage), stage two, stage three, and stage four, and is then guided to the suction side of the fifth-stage impeller through cross-pipeline 35 (the fifth-stage impeller is...). Figure 16 The rightmost impeller 31 passes through stages five, six, seven, and eight (the last stage), and is then discharged through pump outlet 22. Therefore, the multiphase process fluid flowing through the first set of impellers 33 is guided substantially in the opposite direction to the flow flowing through the second set of impellers 34.

[0123] For many applications, the back-to-back arrangement is preferred because the axial thrust acting on the pump shaft 5 generated by the first set of impellers 33 counteracts the axial thrust generated by the second set of impellers 34. Therefore, the two axial thrusts at least partially compensate for each other.

[0124] As another balancing device to reduce the total axial thrust acting on the pump shaft 5, a central bushing 36 is arranged between the first set of impellers 33 and the second set of impellers 34. The central bushing 35 is fixedly connected to the pump shaft 5 in an anti-torsional manner and rotates with the pump shaft 5. When viewed in the direction of increasing pressure, the central bushing 35 is arranged on the pump shaft 5 between the last stage impeller 31 (which is the last impeller in the second set of impellers 34) and the fourth stage impeller 31 (which is the last impeller in the first set of impellers 33). The central bushing 35 is surrounded by a stationary throttling portion that is stationary relative to the pump housing 2. An annular balancing passage is formed between the outer surface of the central bushing 35 and the stationary throttling portion.

[0125] The function of the center bushing 35 between the first and second sets of impellers 33, 34 is to balance the axial thrust and the damping of the pump shaft 5 based on the Lomakin effect. At the axial surface of the center bushing 35 facing the last-stage impeller 31, high pressure dominates, while at the other axial surface facing the fourth-stage impeller 31, lower pressure dominates; this lower pressure is an intermediate pressure between high and low pressure. Therefore, process fluid can be transferred from the last-stage impeller 31 along the center bushing 36 through a balancing passage to the fourth-stage impeller 31.

[0126] The pressure drop across the center bushing 36 is substantially equal to the difference between the high pressure and the intermediate pressure. This pressure drop across the center bushing 36 leads to... Figure 16 The diagram shows a force directed to the left, which subsequently counteracts the axial thrust generated by the second set of impellers 34, the axial thrust being determined according to... Figure 16 The illustration in the image guides the viewer to the right.

[0127] As another balancing device for reducing the total axial thrust acting on the pump shaft 5, the multiphase pump 1 may also include a balancing drum 7 with balancing lines 9 in a manner similar to that described with reference to the first embodiment of the multistage pump 1.

[0128] Of course, the back-to-back design can also be used in embodiments of a vertical multiphase pump 1 configured such that the pump shaft 5 extends along the direction of gravity and / or in embodiments where the drive unit 4 is arranged within the pump housing 2.

Claims

1. A multiphase pump for conveying multiphase process fluids, comprising a pump housing (2) and a rotor (3) disposed within the pump housing (2) and configured for rotation about an axial direction (A), wherein, The rotor (3) includes a pump shaft (5) and at least one impeller (31) fixedly mounted on the pump shaft (5), wherein a stationary diffuser (32) is adjacent to the impeller (31) and arranged downstream of the impeller (31), wherein the impeller includes at least one blade (38), wherein each blade (38) has a radially outer tip (381), and wherein the impeller (31) includes a ring (30) surrounding the impeller (31) and arranged at the radially outer tip (381) of the blade (38), wherein a passage (10) is provided between the ring (30) and a stationary portion (39) configured to be stationary relative to the pump housing (2), the passage (10) extending axially (A) from the inlet (11) to the outlet (12), characterized in that: at least one vortex suppressor is provided at the passage (10), wherein the vortex suppressor is configured and arranged to suppress vortices of the process fluid passing through the passage (10); The stationary portion (39) includes a radially inner surface that defines the passage (10) relative to a radial direction perpendicular to the axial direction (A), wherein the radially inner surface is provided with a groove (60) surrounding the pump shaft (5) in the circumferential direction, and wherein the vortex suppressor is arranged in the groove (60).

2. The multiphase pump according to claim 1, wherein, Multiple vortex suppressors are provided, namely a first vortex suppressor (61) arranged at the inlet (11) of the passage (10) and at least one second vortex suppressor (62) arranged in a groove (60) surrounding the pump shaft (5) in the circumferential direction, wherein the groove (60) is provided in the radial inner surface of the stationary portion (39) to define the passage (10) relative to the radial direction perpendicular to the axial direction (A).

3. The multiphase pump according to claim 2, wherein, The first vortex suppressor (61) is arranged at the diffuser (32) or at the stationary part (39).

4. The multiphase pump according to any one of claims 2 to 3, wherein, Multiple second vortex suppressors (62) are provided, each of which is arranged in a different trench (60).

5. The multiphase pump according to any one of claims 2 to 4, wherein, The ring (30) surrounding the impeller (31) includes a protrusion (301) extending along the circumference of the ring (30), wherein the protrusion (301) is configured to deflect the process fluid at least partially into a vortex suppressor in the groove (60).

6. The multiphase pump according to claim 5, wherein, The protrusion (301) is aligned with the groove (60) relative to the axial direction (A).

7. The multiphase pump according to any one of the preceding claims, wherein, The ring (30) is configured to form a labyrinth seal (302, 303) between the impeller (31) and the stationary portion (39).

8. The multiphase pump according to any one of the preceding claims, comprising multiple stages, wherein, Each stage includes an impeller (31) and a diffuser (32), wherein at least one of the impellers (31) includes a ring (30) surrounding the impeller (31), and wherein the vortex suppressor is disposed at the passage (10) defined by the ring (30).

9. The multiphase pump according to any one of the preceding claims, which is configured as a helical axial flow pump with a helical axial flow impeller (31).

10. The multiphase pump according to any one of the preceding claims, further comprising a drive unit (4) disposed in the pump housing (2) and configured to drive the rotor (3).

11. The multiphase pump according to any one of the preceding claims, wherein, The multiphase pump is configured as a vertical pump in which the pump shaft (5) extends along the direction of gravity.

12. The multiphase pump according to any one of the preceding claims is configured as a submersible pump.

13. The multiphase pump according to any one of the preceding claims, configured for installation on the seabed.

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