EP3121450A1 - Pump for conveying a fluid with varying viscosity - Google Patents

Abstract

There is proposed a pump for conveying a fluid of varying viscosity, comprising a housing (2) with an inlet (3) and an outlet (4) for the fluid to be conveyed, and at least one impeller (7) for conveying the fluid from Inlet (3) to the outlet (4), which is arranged on a rotatable shaft (5) and a discharge piston (6) for Axialschubentlastung, wherein the discharge piston (6) rotatably connected to the shaft (5) rotor (61) a high - pressure side (65) and a low - pressure side (64), a stator (62) stationary with respect to the housing (2), and a relief channel (63) extending between the rotor (61) and the stator (62) of the High pressure side (65) to the low pressure side (64) of the rotor (61) and further comprising a return channel (8) is provided, which connects the low pressure side (63) of the rotor (61) with the inlet (3), wherein at least one intermediate channel (9, 9 ') is provided, which z between the high pressure side (65) and the low pressure side (64) of the rotor (61) into the discharge channel (63) opens, and wherein a blocking member (10, 10 ') for influencing the flow through the intermediate channel (9, 9') is provided ,

Description

The invention relates to a pump for conveying a fluid with varying viscosity according to the preamble of the independent claim.

In single-stage or multi-stage centrifugal pumps, very large hydraulic forces are often generated which act in the axial direction, that is to say in the direction of the longitudinal axis of the shaft of the pump. These forces must be absorbed by the thrust bearing of the shaft. However, these thrust bearings are to be kept as small as possible for practical and technical reasons, it is a well-known measure to provide on the shaft of the pump a balance piston (balance drum) for Axialschubausgleich. This includes a rotatably connected to the shaft, typically substantially cylindrical rotor and a coaxially arranged stator which is stationary with respect to the pump housing. The stator can be configured for example as a separate sleeve or formed by the housing itself. The rotor is dimensioned such that a narrow, annular relief gap is formed between the rotor and the stator. This is the high pressure side connected to the space behind the impeller or in multi-stage pumps the space behind the last impeller so that a leakage flow of the funded fluid can flow through the discharge gap to the low pressure side of the rotor. From there, the fluid is then returned to the inlet of the pump. As a result of the pressure drop across the rotor, a force is generated in the axial direction which is directed opposite to the hydraulic axial forces generated by the impeller, and thus considerably reduces the forces to be absorbed by the axial bearing.

In the design of the relief piston, the geometric dimensions of a very important importance, in particular the diameter and the axial length of the rotor and the clearance between the rotor and stator, which determines the width of the discharge channel in the radial direction.

The leakage flow through the discharge channel causes a volume loss of the pumped fluid, which of course is to be kept as low as possible, the leakage flow on the other hand also has to be so large that the desired technical effects are realized. As a further effect - and this applies in particular to highly viscous fluids - causes the fluid flow in the discharge channel friction, which can lead to a considerable and undesirable increase in temperature in the discharge channel.

In addition to the function of the axial thrust relief, the fluid flowing through the relief channel can also contribute to the stabilization or stability of the pump rotor dynamics. By virtue of the effect known as the lomakin effect, the fluid flowing in the discharge channel generates the shaft centering forces, which have a positive effect on both the damping and the stiffness of the shaft bearing.

Other important parameters to consider when designing the unloading piston are the rotational speed at which the pump is operated, the generated pressure differential, the density of the fluid and the internal friction, ie the viscosity, of the delivered fluid.

It is the design of the pump hydraulics strives to achieve the best possible compromise between all these effects, the fluid properties are usually not influenced and not sufficiently known and therefore can only be estimated.

There are numerous applications in which the properties of the pumped fluid are not constant, but can change more or less quickly.

With multiphase pumps, for example, fluids are conveyed which contain a mixture of several phases, for example one or more liquid phases and one or more gaseous phases. Such pumps have long been well known and are made in numerous embodiments. The range of application of these pumps is very wide, they are used for example in the oil and gas industry for conveying or transporting petroleum or petroleum-natural gas mixtures. The fluid properties can change over time, z. B. the phase composition or phase distribution of the multiphase fluid to be delivered. The relative volume fractions of the liquid and the gaseous phase - for example in the oil extraction - are subject to very large fluctuations, which is partly due to the natural source.

Especially in oil and gas production but also very strong changes in the viscosity of the fluid can occur, which will be explained below by way of example. During the utilization or the skimming off of oil fields the naturally existing pressure in an oil field decreases with time - thus with increasing skimming. It is a known technology to press water into the oil field with decreasing natural pressure in the oil field by means of so-called injection pumps in order to increase the pressure at the borehole. However, this has the consequence that the pump, with which the oil is transported from the borehole, is confronted with a fluid of varying viscosity or internal friction over the period of the skimming: at the beginning of the skimming it is usually the natural oil or oil. Gas mixture being extracted. With increasing water input into the oil field, the fluid eventually changes to a water-oil emulsion, which has a much higher internal friction, which can be orders of magnitude higher than that of the initially extracted oil. With further skimming the proportion of water in the pumped fluid is so large that it comes again to a sharp drop in viscosity.

This pronounced maximum, which occurs during the skimming of an oil field in the time course of the viscosity - usually only after a few years - sometimes makes it necessary to pump the oil from the well or transported by pipelines, or at least to replace their hydraulics. This is of course not desirable for the operator of the oil production for economic reasons, he has the need that the pumps used to promote the oil / natural gas efficient over the entire period of skimming the oil field without replacement of the pump or exchange the pump hydraulics are operated efficiently ,

This is particularly true for such applications in which the pumps are very difficult or accessible only with considerable effort. As an example, subsea applications are mentioned here. Nowadays, more and more oil fields are being siphoned off, which are located under the seafloor and which are no longer or economically attainable with conventional drilling platforms. Therefore, one has begun to place parts of the production equipment, such as pumps, on the seabed near the exit of the wellbore. From there, the extracted oil is then transported to processing or storage facilities on land, on a drilling platform or on a ship as FPSO (Floating Production Storage and Offloading Unit). Especially in those cases where the pump is designed as a subsea pump for operation on the seabed, it is of course desirable to have available a pump that can efficiently and economically deliver even fluids of highly variable viscosity without requiring replacement For example, the pump hydraulics is necessary.

A possible solution is to provide in the return line, with which the fluid flowing through the discharge channel from the low pressure side of the rotor of the discharge piston to the inlet of the pump is provided with an adjustable valve so as to be able to throttle the feedback more or less , Thus, at least in principle, it is also possible to influence the flow through the relief gap between the rotor and the stator. However, throttling in the return line can lead to a significant reduction of the axial thrust balance generated by the relief piston because the pressure drop across the relief piston is significantly smaller. However, this means that the axial thrust of the shaft to be absorbed hydraulic thrust forces greater be, for which this must be designed, otherwise there is a risk that the thrust bearing is overloaded or subject to significantly higher wear.

It is therefore an object of the invention to provide a pump which is suitable for the efficient and economic delivery of fluids with greatly varying viscosity, without requiring an exchange of the pump hydraulics, so the impeller or impellers and / or the relief piston must be made.

The object of the invention solving this object is characterized by the features of the independent claim.

Thus, according to the invention, a pump is proposed for conveying a fluid of varying viscosity, which has a housing with an inlet and an outlet for the fluid to be delivered, and at least one impeller for conveying the fluid from the inlet to the outlet, which is arranged on a rotatable shaft and a relief piston for axial thrust relief, the relief piston comprising a rotatably connected to the shaft rotor having a high pressure side and a low pressure side, a housing stationary stator, and a discharge channel extending between the rotor and the stator from the high pressure side to Low pressure side of the rotor extends and further wherein a return passage is provided, which connects the low pressure side of the rotor with the inlet, wherein at least one intermediate channel is provided which opens between the high pressure side and the low pressure side of the rotor in the discharge channel, u nd wherein a blocking member is provided for influencing the flow through the intermediate channel.

Through the intermediate channel and the locking member, the length of the discharge channel can be changed and thus also the effective length of the rotor of the discharge piston. Since, as already mentioned, the diameter and length of the rotor of the relief piston has a decisive influence both on the flow rate through the relief piston and on the temperature increase caused by friction in the discharge channel, can thus be made by the intermediate channel in a very simple manner to adapt to major changes in the viscosity of the fluid. Functionally, one has now virtually the opportunity to operate the pump with at least two different discharge piston of different lengths. With comparatively lower viscosity of the fluid - that is, for example, at the beginning of the skimming of an oil field, when essentially only oil or an oil-gas mixture is promoted - you can shut off the intermediate channel with the blocking member, so that the leakage flow over the entire length of the discharge piston is guided to the low pressure side of the rotor and discharged from there through the return channel. If there is a strong increase in viscosity - for example, to the described peak in the internal friction of the fluid, which is based on the formation of the oil-water emulsion - so the obturator and thus the intermediate channel is fully opened, so now essentially the entire leakage current is discharged from the discharge channel into the intermediate channel. Since thus the effective length, that is, the flow-through part of the discharge channel is shortened, also significantly reduces the generated in the relief gap by friction increase in temperature. This is proportional to the relationship between friction and leakage rate. In this way, the pump and in particular the discharge piston in a simple manner also adaptable to strong changes in the viscosity of the fluid. It is particularly advantageous that the discharge piston generated by the axial thrust relief, if any, undergoes at least no significant reduction, so no greater burden must be absorbed by the thrust bearing of the shaft.

Preferably, the discharge channel comprises an annular space which surrounds the shaft and into which the intermediate channel opens. This ensures that, when the intermediate channel is open, the fluid can flow out of the discharge channel into the intermediate channel particularly well and evenly.

According to a preferred embodiment, the discharge channel outside the annulus has a constant width in the radial direction. Through the intermediate channel of the discharge channel is divided into a first sub-channel and a second sub-channel, which are arranged in the axial direction one behind the other. Preferably, the relief channel outside the annulus in the first sub-channel or in the second sub-channel - particularly preferably in both sub-channels - a constant width in the radial direction. The width of the first sub-channel may be the same size as the width of the second channel or the first and the second sub-channel have different widths. Due to the different widths of the two sub-channels, the leakage rate through the discharge channel can be increased or reduced in a simple manner.

Preferably, the intermediate channel is connected to the inlet, so that also the effluent via the intermediate channel fluid is returned to the inlet of the pump.

In a preferred embodiment, the intermediate channel opens into the return channel, because in this way the structural design is simpler.

An advantageous measure is that the locking member is designed as an adjustable flow control valve. Thus, the flow in the intermediate channel can also be set to values between zero and the maximum flow.

Depending on the application, it may also be advantageous if a second blocking member is provided for influencing the flow through the return channel. Thus, the flow rate can also be actively influenced in the return channel.

According to a preferred embodiment, the blocking member is designed as a three-way valve, which is flow-connected to the inlet, to the return channel and to the intermediate channel. As a result of this measure, the return channel or the intermediate channel can be fluidly connected to the inlet of the pump in a particularly simple manner in terms of apparatus.

In a likewise preferred embodiment, a switching device is provided, with which the return channel is selectively connectable to the inlet of the pump or to a source of a second fluid, so that the second fluid can be fed through the return channel of the low pressure side of the rotor. Thus, it is possible, for example, to supply a second fluid through the return channel, which can serve as a barrier fluid, for example.

It is of course also possible that the blocking member is arranged and configured such that the intermediate channel is connectable to a source of a second fluid, so that the second fluid can be introduced through the intermediate channel in the discharge channel. The second fluid may, for. B. may be a demulsifier, with which the viscosity of the fluid can be reduced in the relief gap. This is also a possibility to introduce a second fluid into the discharge channel in order to reduce the viscosity of the fluid.

Depending on the application, it may also be advantageous if a plurality of intermediate channels are provided, each of which opens into the discharge channel between the high-pressure side and the low-pressure side. By this measure, even more different lengths of the discharge channel can be realized.

In particular, in applications in hard to reach places - for example, on the seabed, it is an advantageous measure if the locking member or the second locking member or the switching means are remotely operated. For this purpose, these organs may be configured, for example, as electrically or hydraulically or electrically-hydraulically actuated organs, which can then be controlled remotely, for example via a signal line or depending on the application.

In particular, the pump according to the invention can also be configured as a multi-stage pump which has at least one second impeller arranged on the shaft for conveying the fluid.

It is also possible to design the inventive pump as a multi-phase pump.

Particularly preferably, the pump according to the invention can also be designed as a centrifugal pump for oil and gas production, in particular as a subsea pump for undersea oil and gas production.

Further advantageous measures and embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

ein schematische Darstellung eines ersten Ausführungsbeispiels einer erfindungsgemässen Pumpe mit Ausbruch,

Fig. 2:

eine vergrösserte Schnittdarstellung des Entlastungskolbens des ersten Ausführungsbeispiels in einem ersten Betriebszustand,

Fig. 3:

eine vergrösserte Schnittdarstellung des Entlastungskolbens des ersten Ausführungsbeispiels in einem zweiten Betriebszustand,

Fig. 4:

wie Fig. 1, jedoch für eine erste Variante,

Fig. 5:

wie Fig. 1, jedoch für eine zweite Variante,

Fig. 6:

wie Fig. 1, jedoch für eine dritte Variante,

Fig. 7:

eine vergrösserte Schnittdarstellung des Entlastungskolbens in einem Betriebszustand der dritten Variante aus Fig. 6,

Fig. 8:

wie Fig. 1, jedoch für eine vierte Variante,

Fig. 9:

eine vergrösserte Schnittdarstellung des Entlastungskolbens in einem Betriebszustand der vierten Variante aus Fig. 8, und

Fig. 10:

wie Fig. 2 jedoch für ein zweites Ausführungsbeispiels einer erfindungsgemässen Pumpe.

In the following the invention will be explained in more detail by means of embodiments and with reference to the drawing. In the drawing show, partly in section:

Fig. 1:

1 is a schematic representation of a first embodiment of a pump according to the invention with an outbreak,

Fig. 2:

an enlarged sectional view of the discharge piston of the first embodiment in a first operating state,

3:

an enlarged sectional view of the discharge piston of the first embodiment in a second operating state,

4:

as Fig. 1 but for a first variant,

Fig. 5:

as Fig. 1 but for a second variant,

Fig. 6:

as Fig. 1 but for a third variant,

Fig. 7:

an enlarged sectional view of the relief piston in an operating state of the third variant Fig. 6 .

Fig. 8:

as Fig. 1 but for a fourth variant,

Fig. 9:

an enlarged sectional view of the relief piston in an operating state of the fourth variant Fig. 8 , and

Fig. 10:

as Fig. 2 however, for a second embodiment of a pump according to the invention.

Fig. 1 shows a schematic representation of a first embodiment of an inventive pump, which is generally designated by the reference numeral 1 and is designed as a centrifugal pump or centrifugal pump. In Fig. 1 some parts of the pump 1 are shown in the outbreak. Fig. 2 shows some parts of the pump 1 in an enlarged sectional view.

The pump 1 has a housing 2 with an inlet 3, through which a fluid to be conveyed into the pump 1 can be introduced, as the arrow E in Fig. 1 symbolizes. Further, the housing 2 has an outlet 4, through which the fluid to be pumped leaves the pump 1, as the arrow O in Fig. 1 symbolizes. In addition, the pump has a rotatable shaft 5 whose longitudinal axis A defines an axial direction. In the following, therefore, the direction of the longitudinal axis A of the shaft 5 is always meant for references to the axial direction. By the radial direction is meant a direction perpendicular to the axial direction.

On the shaft 5, at least one impeller 7 is provided for conveying the fluid, of which in Fig. 2 only the upper half is shown. The inventive pump 1 can be designed both as a single-stage pump with only one impeller 7, as well as a multi-stage pump with at least two wheels 7, which are arranged axially spaced one behind the other on the shaft 5 in a conventional manner. References to the impeller 7 in the following either the only impeller of a single-stage pump meant or the last impeller 7 of a multi-stage pump, which is the impeller 7 which generates the highest pressure. Preferably, the inventive pump 1 is designed as a multi-stage centrifugal pump.

Furthermore, the inventive pump 1 can be configured as a single-phase pump or as a multi-phase pump. Multiphase pumps are designed to deliver multiphase fluids, so they can deliver fluids containing a mixture of multiple phases, such as one or more several liquid phases, eg. In the form of an emulsion, and one or more gaseous phases. Preferably, the inventive pump 1 is designed as a multi-phase pump.

The pump according to the invention is preferably a pump 1 for conveying highly viscous fluids, such as oil or petroleum. For the purposes of this application, high-viscosity fluids mean fluids whose dynamic viscosity is at least 65 cP (centipoise), which corresponds to 0.065 Pa · s (pascal-seconds) in SI units.

In the following, reference is made by way of example to the case of application which is important for practical application in that the pump according to the invention is used in the extraction of oil and gas, for example as a feed pump with which the oil or oil-gas mixture is conveyed out of the borehole of an oilfield or as a transport pump, with which the oil or the oil-gas mixture is conveyed through a pipeline. In particular, the pump 1 according to the invention can be designed as a subsea pump, which is operated on the seabed, for example, during subsea oil and gas production. It is understood, however, that the invention is not limited to such embodiments and applications.

The first embodiment of the inventive pump 1 (see Fig. 1 and Fig. 2 ) has a discharge piston 6 for axial thrust relief. With the relief piston 6, a force is generated in the axial direction, which is directed opposite to the axial hydraulic force generated by the wheels 7 during the delivery of the fluid.

The relief piston 6 has a substantially cylindrical rotor 61 which is rotatably connected to the shaft 5 and a stationary relative to the housing 2 stator 62. The stator 62 may be configured for example as a cylindrical sleeve which is fixedly connected to the housing 2 or parts of the housing 2 itself may form the stator 62. The rotor 61 has a diameter D. It has a high pressure side 65 and a low pressure side 64. The end face on the high pressure side 65 of the rotor 61 is subjected to a high pressure. This is typically done by pressurizing the high pressure side 65 of the rotor 61 standing fluid behind the impeller 7 and behind the last impeller 7 acted upon. The high-pressure side 65 is then subjected essentially to the pressure which comprises the fluid at the outlet 4 of the pump 1. The low-pressure side 64 is subjected to a significantly lower pressure, typically with the pressure that the fluid has at the inlet 3 of the pump. This can for example be realized so that the low-pressure side 64 of the rotor 61 is flow-connected via a return channel 8 with the inlet 3 of the pump.

The diameter D of the rotor 61 and the inner diameter of the cylindrical stator 62 are dimensioned such that between the lateral surface of the rotor 61 and the inner circumferential surface of the stator 62, an annular discharge channel 63 is formed which extends between the rotor 61 and the stator 62 of the High pressure side 65 extends in the axial direction to the low pressure side 64. The width B1 or B2 of the discharge channel 63 in the radial direction corresponds to the difference between the inner diameter of the stator 62 and the diameter D of the rotor.

• Zum ersten bedeutet die Leckageströmung Q einen Volumenverlust des von der Pumpe geförderten Fluids. Es ist daher wünschenswert, dass diese Leckageverluste nicht zu gross werden.

The leakage flow Q through the discharge passage 63 causes, inter alia, the following three effects:

• First, the leakage flow Q means a volume loss of the fluid delivered by the pump. It is therefore desirable that these leakage losses do not become too large.

Secondly - and this is especially true for highly viscous fluids - the fluid generated when flowing through the discharge channel 63 by adhering or rubbing in particular on the stator 62 and the rotor 61, to a considerable extent heat, the significant temperature increases in the discharge gap 63 and the can lead him surrounding components. These temperature increases can be so strong, for very high viscosity fluids z. B. 100 ° C and more that the system can not be operated safely or that they can lead to damage to components of the pump 1.

Thirdly, besides the axial thrust relief, the leakage flow Q flowing through the relief channel 63, due to the lomakin effect, causes forces which center the shaft 5 to stablise and dampen vibrations. This effect therefore has a positive effect on the damping and the rigidity of the shaft bearing.

The leakage flow Q and its effects depend on very many parameters, on the one hand of the geometric dimensions of the relief piston 6, which are for a given inner diameter of the stator 63 mainly the diameter D of the rotor 61, which determines the width B1, B2 of the discharge channel 63, and the length L of the rotor 63 in the axial direction, which determines the axial length of the discharge channel 63. These parameters must be determined in the design of the pump 1 for their later use, which often extends over an operating life of many years, and can then be changed later only by replacing the hydraulic components of the pump 1.

The leakage flow Q also depends on the pressure difference falling across the rotor 61 from the rotational speed, i. the rotational speed of the pump 1, and of course the properties of the fluid to be delivered, such as its density or its viscosity.

It is therefore desirable in the design of a pump 1, to consider all these effects and to design the pump so that it can be operated for many years for the particular application, if possible without replacing the hydraulic components.

So that the pump 1 is suitable in particular for the continuous delivery of a fluid having a greatly varying viscosity, it is proposed according to the invention to provide at least one intermediate channel 9, which opens into the discharge channel between the high-pressure side 65 and the low-pressure side 64 of the rotor 61, and a blocking element 10 (FIG. please refer Fig. 1 ) for influencing the flow through the intermediate channel. 9

By this measure, the length of the relief gap 63 can be varied, resulting in a particularly good adaptability to variations in the viscosity of the fluid.

In the first embodiment of the pump 1 described here, the relief channel 63 comprises an annular space 66, which surrounds the shaft 5, and in which the intermediate channel 9 opens. The annular space 66 has in the radial direction a width greater than the width B1, B2 of the discharge channel 63. Outside the annular space 66, the discharge channel 63 seen over its axial length has a constant width B1 or B2 in the radial direction. Of course, embodiments are possible in which these widths B1 or B2 vary.

The intermediate channel is as in Fig. 1 shown connected to the inlet 3 of the pump. The blocking member 10 is configured at least as an on-off valve which completely blocks the flow connection through the intermediate channel 9 to the inlet 3 in a first position, and which completely opens the flow connection through the intermediate channel 9 in a second position.

Fig. 2 shows the first embodiment of the pump 1 in a first operating state in which the locking member 10 is in the first position, that closes the flow connection through the intermediate channel 9, while Fig. 3 shows the first embodiment of the pump 1 in a second operating state in which the locking member 10 is in the second position, so the flow connection through the intermediate channel 9 opens completely.

Preferably, the blocking member 10 is configured as an adjustable flow valve 10, with which the leakage flow Q is adjustable through the intermediate channel 9 to values between zero and the maximum flow.

Both the return channel 8 and the intermediate channel 9 are each configured, in particular with respect to their diameter, that they have at least no significant throttling effect on the leakage flow Q, ie the respective flow resistance of the return channel 8 and the intermediate channel 9 is dimensioned so that it is much smaller is as the As a result, it is possible to ensure that essentially the entire pressure difference across the rotor 61 drops and this therefore generates the greatest possible axial thrust relief.

In the following, the function of the pump 1 and in particular the adaptation to the varying viscosity of the fluid will be described using the example of skimming an oil field with the pump 1.

At the beginning of the withdrawal of an oil field this is still under its original natural pressure and the oil or the oil-gas mixture can often be promoted without additional measures with the pump 1. A typical value for the viscosity of the oil in this phase is for example 100-200 cP.

In this phase, the pump 1 is in the in Fig. 2 operated shown first operating state. With the blocking member 10, the flow connection is blocked by the intermediate channel 9 for the leakage flow Q. The discharge channel 63, which has the total length L in the axial direction, is now the flow connection of a first sub-channel 631 of the axial length L1, which extends from the high-pressure side to the beginning of the annular space 66 and has a radial width B1, and a second Partial channel 632 of the axial length L2, which extends in the flow direction from the axial end of the annular space 66 to the low pressure side 64 and has a radial width B2. The effective length of the discharge channel 63 is thus the sum of L1 + L2, where natural L1 + L2 is smaller than the total length L. The leakage flow Q thus flows completely from the high pressure side 65 through the discharge channel 63 to the low pressure side 64 and from there through the return channel 8 back to the inlet 3 of the pump.

The width B1 of the first sub-channel 631 in the radial direction and the width B2 of the second sub-channel 632 in the radial direction are preferably each constant over the axial length L1 of the first or L2 of the second sub-channel. The widths B1 and B2 may be the same or different. If the widths B1 and B2 are designed differently, this results additionally the possibility of changing the width of the discharge channel, whereby one has another parameter for influencing the leakage flow Q available.

Different widths B1 and B2 can be realized, for example, in that the rotor 61 has a different diameter D in the region in which it forms the first part-channel 631 than in the region in which it forms the second part-channel 632. Of course, it is also possible to make the diameter D of the rotor 61 constant over its entire axial length L and to design the stator 62 in the region of the first sub-channel 631 with a different inner diameter than in the region of the second sub-channel 632. Further, a combination of the two measures possible, so both the inner diameter of the stator 62 and the diameter D of the rotor over the respective axial length L to design differently.

As described above, as the skimming of the oil field progresses, the natural pressure in the oil field decreases and, for example, water begins to be forced into the oil field, thereby increasing the pressure in the oil field or compensating for the pressure drop. As a result of this injection of water, the formation of an emulsion of the oil and the water increases with increasing time, and this emulsion must now be conveyed by the pump 1. Forming the emulsion can be associated with a drastic increase in internal friction or viscosity, which can vary in the order of magnitude. This peak in viscosity over time in the withdrawal of the oil field is known and it can occur, for example, only after a few years of levy.

If, however, the viscosity of the fluid rises sharply, this reduces the leakage flow Q on the one hand, and on the other hand leads to a drastic increase in the heat generated in the relief gap 63 and thus to a significant increase in temperature. In order to avoid this temperature increase in particular, the pump is now switched to the second operating state, the in Fig. 3 is shown.

The blocking member 10 is now brought into the position in which it completely opens the flow connection through the intermediate channel 9 for the leakage flow Q. Since the intermediate channel 9 is now for the leakage flow Q considerably less resistance than the second sub-channel 632 of the discharge channel 63, the majority of the leakage flow Q flows from the high-pressure side 65 through the first sub-channel 631 of length L1 in the annular space 66 and from there the intermediate channel 9 to the inlet 3 of the pump 1. Thus, the effective length of the discharge channel 63 is now only the length L1 of the first sub-channel 631 and thus significantly smaller than in the first operating state. Hereby it can be achieved that the leakage rate is increased and the heat generated in the discharge channel 63 is considerably smaller and thus also the resulting increase in temperature. In addition, if the first sub-channel 631 is designed with a larger radial width B1, as the second sub-channel 632, so does the effective width of the discharge channel 63, thereby additionally increasing the leakage flow Q increases.

As the oil field is further skimmed off, the proportion of water in the pumped fluid is always greater, as a result of which the viscosity drops drastically again after passing through the maximum due to the formation of the emulsion. Now, the pump 1 can be brought back by closing the locking member 10 in the first operating state, the in Fig. 2 is shown.

The appropriate choice of the ratios of the lengths L1 to L2 or L1 to L or L2 to L and the widths B1 and B2 in the radial direction depends on the particular application. Typically, prior to skimming a new oil field, calculations are made regarding the long-term behavior of the skimming. By means of such calculations, for example, a suitable value for L, L1, L2 as well as the widths B1, B2 of the discharge channel 63 or the diameter D of the rotor 61 can be determined by means of model calculations or simulations.

It is understood that differing from the illustration in Fig. 1 Embodiments are also possible in which the intermediate channel 9 opens downstream of the blocking member 10 in the return channel 8.

Fig. 4 shows a first variant of the embodiment of the pump 1. In this variant, a second locking member 12 for influencing the flow through the return channel 8 is provided. The blocking member 12 may also be configured as an open-close valve 12 or as an adjustable flow valve, with which the leakage flow Q is adjustable by the return channel 3.

Fig. 5 shows a second variant of the embodiment of the pump 1. In this second variant, the intermediate channel 9 opens into the return channel 8 a. At this junction, the locking member 10 is provided, wherein the locking member is designed as a three-way valve 10 which is fluidly connected to the inlet 3, with the return channel 8 and with the intermediate channel 9. For the realization of the first operating state ( Fig. 2 ), the three-way valve 10 is switched to connect the return passage 8 to the inlet 3 so that the leakage flow Q can flow through the return passage 8 to the inlet 3. In this position, the intermediate channel 9 is blocked so that no leakage flow Q can flow through it. For the realization of the second operating state ( Fig. 3 ), the three-way valve 10 is switched so that it connects the intermediate channel 9 with the inlet 3, so that the leakage flow Q can flow from the annular space 66 through the intermediate channel 9 to the inlet 3. In this position, the return channel 8 is blocked, so that no leakage flow Q can flow through it.

Fig. 6 illustrates a third variant of the embodiment of the pump 1. In this third variant, a switching device 13 is provided in the return channel 8, with which the return channel 8 is selectively connectable to the inlet 3 of the pump 1 or with a source 15 for a second fluid, so the second fluid can be supplied through the return channel 8 to the low-pressure side 64 of the rotor.

Fig. 7 shows in one too Fig. 2 respectively. Fig. 3 analog representation of an operating state of the third variant Fig. 6 , In this operating state, the switching member 13 is set to connect the return passage 8 to the second fluid source 15, and the flow communication to the inlet 3 of the pump 1 is shut off. The second fluid is, for example, a barrier fluid such as water or another suitable medium or a Cooling fluid with which in the second sub-channel 632 of the discharge channel 63, a back pressure can be generated. In Fig. 7 the flow of the second fluid is indicated by dotted, arrowed lines. The second fluid flows through the return channel 8 to the low pressure side 64 of the rotor and from there through the second sub-channel 632 of the discharge channel 63 of the leakage flow Q against. In the region of the annular space 66, the two fluids combine and are discharged together through the intermediate channel. The second fluid can be used, for example, to generate a backpressure in the discharge channel 63 in order to reduce the flow rate of the leakage flow Q or to remove heat from the relief gap 63.

Fig. 8 shows a fourth variant of the first embodiment of the pump 1. In this fourth variant, the blocking member 10 is arranged and configured so that the intermediate channel 9 is connectable to a source 16 for a second fluid, so that the second fluid through the intermediate channel in the discharge channel 63rd can be introduced. Preferably, the locking member 10 is configured here as a three-way valve 10, which connects the intermediate channel 9 selectively with the inlet 3 of the pump 1 or with the source of the second fluid.

Fig. 9 shows in one too Fig. 2 respectively. Fig. 3 analog representation of an operating state of the fourth variant Fig. 8 , In this mode of operation, the three-way valve 10 is set to connect the intermediate channel 9 to the second fluid source 16 and block the flow connection to the inlet 3 of the pump 1. The second fluid is for example a demulsifier, with which the viscosity of the leakage flow Q can be reduced, or water for diluting the leakage flow Q, or a cooling fluid, with which heat can be removed from the relief gap 63. In Fig. 9 the flow of the second fluid is indicated by dotted, arrowed lines. The second fluid flows through the intermediate channel 9 into the annular space 66, where it connects to the leakage flow Q and flows together with it through the second sub-channel 632 of the discharge channel 63 to the low-pressure side 64. From there, the leakage flow Q is discharged together with the second fluid through the return channel 8.

It is understood that the four variants described here or the measures explained can be combined with one another in any desired manner.

Fig. 10 Indicates in one Fig. 2 analogous representation of a second embodiment of a pump according to the invention 1. In the following, only the differences from the first embodiment will be discussed. The reference numerals have the same meaning as they have already been explained in connection with the ersaten embodiment. The explanations regarding the first embodiment and all of its variants apply in the same or analogous manner to the second embodiment.

In the second embodiment of the inventive pump 1 is still a second intermediate channel 9 'is provided, which also opens between the high pressure side 65 and the low pressure side 64 in the discharge channel 63. For this second intermediate channel 9 ', a further blocking member 10' is provided, with which the leakage flow Q in the second intermediate channel 9 'can be influenced. In particular, the second intermediate channel 9 'can be blocked by means of the further blocking member 10', so that no leakage flow Q can flow through it and the second intermediate channel 9 'can be fluidly connected to the inlet 3 of the pump 1 by means of the further blocking member 10', so that the Leakage flow Q can flow through the second intermediate channel 9 'to the inlet of the pump 1.

Furthermore, the discharge channel 63 has a second annular space 66 'on which the shaft surrounds and in which the second intermediate channel 9' opens.

In this embodiment with the two intermediate channels 9, 9 'corresponds to the discharge channel 63 fluidly connected in series of three sub-channels, namely a first sub-channel 631 of the axial length L1, which extends from the high-pressure side 65 to the beginning of the annular space 66, a second sub-channel 632 the axial length L2 extending from the end of the annulus 66 to the beginning of the second annulus 66 'and a third subchannel 633 of axial length L3 extending from the end of the second annulus 66' to the low pressure side 64 of the rotor 61. The respective width B of the subchannels 631, 632, 633 is in Fig. 10 for the sake of clarity, in summary only designated B. It is understood, however, that in mutually identical manner as in the first embodiment, each sub-channel 631, 632, 633 may have a different width in the radial direction, or that the same width is selected in the radial direction for two of the sub-channels and for the remaining sub-channel 631 or 632 or 633 one of them different width. Of course, the same width B in the radial direction can also be counted for all three subchannels 631, 632, 633. Within a subchannel, the width B is preferably constant but may vary.

With this embodiment, a total of three discharge channels of different lengths can be realized in the operating state. If the leakage flow Q is allowed to flow out through the return channel 8, the effective length of the discharge channel 63 in the axial direction is L1 + L2 + L3, this effective length being naturally smaller than the total length L.

If the leakage flow Q is allowed to flow out through the second intermediate channel 9 ', as in FIG FIG. 10 is shown, then the effective length of the discharge channel 63 in the axial direction L1 + L2.

Letting the leakage flow Q flow through the first intermediate channel 9, then the effective length of the discharge channel 63 is only L1.

In this way, therefore, several relief channels 63 can be realized, all of which have different lengths in the axial direction and can also have different widths B in the radial direction.

Of course, here too the intermediate channels 9, 9 'or the return channel 8 can be used for supplying a second fluid.

It is understood that in an analogous manner also more than two intermediate channels 9, 9 'can be provided, each of which opens into the discharge channel 63.

In the case of the pump 1 according to the invention, it is also possible to assemble the rotor 61 and / or the stator 62 from a plurality of parts. It is therefore by no means necessary that the rotor 61 or the stator 62 is designed in one piece. Furthermore, it is possible to configure the rotor 61 or the stator 62 in such a way that the relief gap 63 also has no constant width B1, B2, B outside the annular spaces 66, 66 ', but tapers or widens, for example, in the axial direction. Furthermore, it is possible to coat or to structure the lateral surface of the rotor 61 or the inner circumferential surface of the stator 62. Furthermore, it is possible to provide on the high-pressure side 65 in the region of the inlet in the discharge channel 63 and / or in the discharge channel 63, for example at the entrances to the respective partial channels 631, 632, 633, one or more swirl brakes, with which flows of the fluid be deflected in the circumferential direction about the shaft 5 in the axial direction.

The locking member 10, 10 'and the second locking member 12 may be configured as open-close valves, with which the flow through the respective channel is either completely released or completely blocked. But it is also possible to design the blocking member 10, 10 'or the second locking member 12 as an adjustable flow valve, with which the flow in the respective channel to any values between zero and a maximum value can be adjusted.

The blocking member 10, 10 'or the second locking member 12 or the switching member 13 may be configured so that they can be operated remotely, for example in undersea applications via a signal line through which a preferably electrical or hydraulic signal is passed, which the respective blocking member or Change-over in the respectively desired state switches or regulates. The remote-controlled operability can also be designed signal line free.

Of course, such embodiments of the locking members 10, 10 ', 12 or the switching member 13 are possible in which the respective member 10, 10', 12 and 13 is manually, that is, operated by hand. In submarine applications, this manual adjustment can also be made with the help of diving robots.

Claims (15)

A pump for delivering a fluid of varying viscosity, comprising a housing (2) having an inlet (3) and an outlet (4) for the fluid to be delivered, and at least one impeller (7) for conveying the fluid from the inlet (3) to the outlet (4), which is arranged on a rotatable shaft (5), and a relief piston (6) for Axialschubentlastung, wherein the discharge piston (6) rotatably connected to the shaft (5) rotor (61) having a high pressure side (65 ) and having a low pressure side (64), a stator (62) stationary with respect to the housing (2), and a relief channel (63) extending between the rotor (61) and the stator (62) from the high pressure side (65). to the low-pressure side (64) of the rotor (61) and further comprising a return channel (8) connecting the low-pressure side (63) of the rotor (61) to the inlet (3), characterized in that at least one intermediate channel ( 9, 9 ') is provided, which zwisc hen the high pressure side (65) and the low pressure side (64) of the rotor (61) into the discharge channel (63) opens, and that a blocking member (10, 10 ') for influencing the flow through the intermediate channel (9, 9') is provided , Pump according to claim 1, in which the relief channel (63) comprises an annular space (66, 66 ') surrounding the shaft (5) and into which the intermediate channel (9, 9') opens. Pump according to one of the preceding claims, wherein the discharge channel (63) outside the annular space (9, 9 ') in a first part of channel (631) of the discharge channel (63) or in a second sub-channel (632) of the discharge channel (63) has a constant Width (B1, B2, B) in the radial direction. Pump according to one of the preceding claims, wherein the intermediate channel (9) is connected to the inlet (3). Pump according to one of the preceding claims, wherein the intermediate channel (9) opens into the return channel (8). Pump according to one of the preceding claims, wherein the blocking member (10) is designed as an adjustable flow control valve. Pump according to one of the preceding claims, wherein a second blocking member (12) for influencing the flow through the return channel (8) is provided. Pump according to one of the preceding claims, wherein the blocking member (10) is designed as a three-way valve which is connected in flow communication with the inlet (3), with the return duct (8) and with the intermediate duct (9). Pump according to one of the preceding claims, wherein a switching member (13) is provided, with which the return duct (8) is selectively connectable to the inlet (3) of the pump (1) or to a source (15) for a second fluid, so the second fluid can be fed through the return channel (8) of the low-pressure side (64) of the rotor (61). Pump according to one of the preceding claims, wherein the blocking member (10) is arranged and configured so that the intermediate channel (9) is connectable to a source (16) for a second fluid so that the second fluid flows through the intermediate channel (9) the discharge channel (63) can be introduced. Pump according to one of the preceding claims, wherein a plurality of intermediate channels (9, 9 ') are provided, each of which between the high pressure side (65) and the low pressure side (64) opens into the discharge channel (63). Pump according to one of the preceding claims, in which the blocking element (10, 10 ') or the second blocking element (12) or the switching element (13) can be operated remotely. Pump according to one of the preceding claims, designed as a multi-stage pump having at least a second, arranged on the shaft impeller (7) for conveying the fluid. Pump according to one of the preceding claims, designed as a multi-phase pump. Pump according to one of the preceding claims, designed as a centrifugal pump for the oil and gas production, in particular as a subsea pump for subsea oil and gas production.

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