Patent Application
20110280741
The invention relates to a helico-axial pump for conveying multiphase mixtures, to a rotor for a helico-axial pump, to a hybrid pump having a helico-axial pump as well as to a method for journalling a rotor in a helico-axial pump in accordance with the preamble of independent claims 1, 10, 13 and 14.
The problem occurs in the conveying of multiphase mixtures such as crude oil, which also contains natural gas and frequently also water and solid portions such as sand in addition to oil, that the efficiency of the pump apparatus used falls as the gas portion in the multiphase mixture rises. The use of pump apparatus having radial impellers is, for example, already no longer possible or no longer economic at low gas densities from a volumetric gas/liquid ratio of more than 0.04 to 0.06. In conventional conveying plants, with a higher gas portion, the gaseous phase of the multiphase mixtures is therefore first separated from the liquid phase and the two phases are then conveyed separately at respectively different conveying conditions. Such a separation of the liquid phase and the gaseous phase of the multiphase mixture is not always possible or economic in dependence on the specific conditions of use at the site of conveying. Special pumping apparatus or compression apparatus were therefore developed to reduce the volumetric gas-to-liquid ratio of the multiphase mixtures to be conveyed so much that subsequently a conventional pump apparatus can be used for the further conveying, for example a displacement pump, a rotary pump or a jet pump.
Such pumping apparatus or compression apparatus for multiphase mixtures having an increased gas portion are already known, for example, from GB-A-1 561 454, EP 0 486 877 or U.S. Pat. No. 5,961,282.
The hybrid pump in accordance with U.S. Pat. No. 5,961,282, for example, is a system for the compression of a multiphase mixture which can in particular include a substantial gas portion in addition to a liquid phase. The pump in this respect includes a multistage axial flow pump for reducing the relative gas portion, i.e. the axial flow pump serves for increasing the density of the multiphase mixture so that it can finally be pumped by a further customary centrifugal pump from a lower level to a higher level, for example from the bottom of the sea to an oil platform, a ship or to a land-based plant.
As already mentioned, the helico-axial pump acting as a compressor includes a rotor having a plurality of compression stages, in practice, for example, having up to sixteen or more stages, so that the multiphase mixture can be compressed step-wise from a relatively low density having a high relative volume portion of gas up to a highly compressed multiphase mixture having such a high density that the highly compressed mixture can be conveyed onward using a conventional pump.
A compression stage K′ know per se of a rotor 2′ of a helico-axial pump 1′ is shown schematically in
Each compression stage K′ in this respect includes a rotating impeller 3′ having a screw 31′, wherein the rotating impeller 3′ is similar to a short Archimedean screw, and includes a stator 4′ adjacent thereto which is made up of a plurality of static, that is not rotating, blades 41′. The impeller 3′ and the stator 4′ are in this respect mounted with respect to a common pump shaft 5′ such that the impeller 3′ is set into rotation by the pump shaft 5′ in the operating state while the stator 4′ is decoupled from the rotary movement of the pump shaft 5′ and therefore does not rotate with respect to the impeller 3′. The pump shaft 5′ in this respect extends along a longitudinal axis A′. The plurality of the compression stages L′ are in this respect arranged in series behind one another in a substantially tubular pump housing 6′.
The rotating screws 31′ conveys the multiphase mixture M′ in the direction of the arrow e.g. from a preceding compression stage K′ not shown in
To obtain a sufficiently high compression of the multiphase mixture M′, a larger number of compression stages K′, for example up to sixteen or even more, has to be provided in series in practice, as already mentioned, each compression stage being made up of an impeller 3′ and a stator 4′ in series, which necessarily results in a considerable construction length of the helico-axial pump 1′.
The decisive disadvantage of such long rotors 2′ formed from a plurality of compression stages K′ is therefore that they can only be controlled with great difficulty vibration-wise. These long rotors 2′ namely form a vibration-capable system in the interior of the tubular pump housing 6′, said vibration-capable system in particular being able to form different transverse vibration modes which can be so intensive that the pump can no longer be operated at a preset number of revolutions or in a specific revolution field. Furthermore, the efficiency of the pumps 1′ can also be reduced and in the worst case even damage to the pump 1′ is to be feared if the rotor 2′, for example, starts to vibrate so strongly and in such an uncontrolled manner that parts of the rotor 2′, such as the impeller 3′, come into contact with the pump housing, for example, due to the vibration movement. In this respect, the kind and the intensity of the vibrations of the rotor 2′ do not only depend on the specific geometry, but rather also on the operating condition of the pump 1′, of the multiphase mixture M′ to be pumped, of the speed of the pump 1′ and of further known, and in some cases not exactly known parameters so that it is hardly possible to cope with the problems with the damaging vibrations of the rotor 2′ solely by an adaptation of the geometrical relationships of known pumps 1′ or by using new materials.
In this respect, there is a clear desire for pumps having an ever higher number of compression stages so that multiphase mixtures with ever higher gas portions can be compressed better and better, that is to ever higher pressures, so that the multiphase mixture compressed in this manner can be pumped onward more reliably and over larger and larger pressure differences or height differences.
It is therefore the object of the invention to provide a helico-axial pump for the conveying of multiphase mixtures, in which the damaging vibrations of the rotor are largely avoided and the vibrations of the rotor are reduced or damped to a presettable degree so that, on the one hand, an improved running of the rotor can be achieved in the operating state and, on the other hand, the pump can be operated at speeds or in a revolution field in which the helico-axial pumps known from the prior art cannot be operated due to the above-described damaging vibrations of the rotor. In addition, the new pump should alternatively or simultaneously be equipped with more compression stages than in the pumps previously known in the prior art in which the length of the pump and thus the maximum number of compression stages is limited by the vibrations of the rotor in the operating state.
The subjects of the invention satisfying this object are characterized by the features of the independent claims of the respective category.
The dependent claims relate to particularly advantageous embodiments of the invention.
The invention thus relates to a helico-axial pump for conveying a multiphase mixture, which helico-axial pump includes a rotor rotatably journalled about a longitudinal axis in a pump housing and having a first part rotor and a second part rotor, wherein the first part rotor and the second part rotor include a compression stage having a helico-axial impeller and a stator for the compression of the multiphase mixture. In accordance with the invention, a hydrodynamic stabilization bush having a stabilization surface is provided and designed between the first part rotor and the second part rotor such that a stabilization gap is formed before the stabilization surface so that a hydrodynamic stabilization layer is formed from a stabilization medium in the stabilization gap in the operating state.
It is thus important for the invention that a hydrodynamic stabilization bush having a stabilization surface is provided in the pump housing so that a stabilization gap is formed before the stabilization surface, in which stabilization gap a hydrodynamic stabilization layer is formed in the operating state of the pump.
The rotor dynamics are thus decisively improved by the present invention because the damping and stiffness of the vibration-capable rotor system are decisively increased by the stabilization layer.
The damaging vibrations of the rotor are largely avoided by the formation of the stabilization layer in the stabilization gap before the stabilization surface of the stabilization bush and are reduced or damped to at least a presettable tolerable degree so that the pump can also be operated at a revolution speed or in a specific revolution field where this is no longer possible to date without using the stabilization layer in accordance with the invention. An even higher efficiency of the pump and a smoother, improved running of the rotor in the operating state can furthermore possibly be achieved. Which ultimately has the result that not only energy for the operation of the pump can be saved, but also the service intervals can be extended, whereby the costs associated therewith can be dramatically cut and the service life of the pump is simultaneously also substantially increased.
A further particular advantage is that it is possible for the first time by the invention to construct pumps with a much higher number of compression stages than was previously possible. The possible number of compression stages was previously restricted simply by the vibrations of the rotor which increase hugely as the number of compression stages increases. The rotor can be reliably stabilized over practically any desired length by the invention.
In this respect, in a helico-axial pump in accordance with the invention, the stabilization layer forms quasi-automatically in the stabilization gap before the stabilization surface of the hydrodynamic stabilization bush so that, in a simple embodiment which is, however, of particular importance in practice, no further construction measures have to be taken except for a suitable setting of the size or shape of the stabilization gap or of the stabilization bush and/or its stabilization area.
If the geometry of the stabilization gap is set in accordance with the demands in a helico-axial pump in accordance with the invention, a pressure difference is formed above the stabilization gap in the operating state between the multiphase mixture which is located in the first part rotor and the one which is located in the second part rotor such that a presettable flow of multiphase mixture is automatically adopted from the second part rotor over the stabilization gap back to the first part rotor, whereby a stabilization layer is automatically formed for the stabilization or damping of the damaging vibrations of the rotor.
In this respect, the degree, that this the amount of the damping, can be adapted in a simple manner in dependence on the technical demands or specifications in a helico-axial pump in accordance with the invention. This can take place, for example, by a suitable selection of the geometry, for example of the geometrical shape or width of the stabilization gap.
A helico-axial pump in accordance with the invention is in this respect particularly preferably configured in the form of a so-called back-to-back arrangement. A back-to-back arrangement is understood by the skilled person as an arrangement of two pump rotors in series which thus forms a pump with two pressure stages. The medium to be pumped is in this respect supplied via an intake opening of the pump to the first pressure stage, wherein the medium passes through the first pressure stage in a first axial direction, wherein in this respect the pressure of the medium to be pumped is increased to a first intermediate pressure. The medium is then supplied from the first pressure stage via a passage system to the second pressure stage such that the medium passes through the second pressure stage in a second axial direction which is opposite to the first axial direction of the first pressure stage. In the second pressure stage, the medium is then brought to the desired end pressure and is led off from the pump via a pressure opening for further use.
It is important in this respect for the back-to-back arrangement of the pumps known from the prior art, which are all not helico-axial pumps, that the direction of flow of the medium in the first pressure stage is opposite to the direction of flow in the second pressure stage. In the known pumps, the back-to-back arrangement namely serves only to at least partly compensate the huge thrust forces which act on the bearings of the pump shaft in the axial direction and thus to relieve the bearings. The huge axial thrust forces are in this respect due to the fact that very high pressures with very large components in the axial direction are produced in these pumps known from the prior art. Vibrations of the pump rotor play a very subordinate role here because the rotors as a rule do not have any great extent and/or are only made up of a respective one compression stage and/or an additional mechanical bearing, for example a ball bearing, is provided between the first pressure stage and the second pressure stage and additionally mechanically journals the pump rotor in the middle.
Since the axial pressure components in helico-axial pumps are rather small in comparison with other conventional pumps, the thrust forces which act on the bearings of the helico-axial pump in the axial direction do not play a decisive role. A back-to-back arrangement for helico-axial pumps was therefore also previously never taken into consideration because the known advantage of the back-to-back arrangement can actually not be exploited in helico-axial pumps.
The material recognition of the invention is therefore that the back-to-back arrangement can be used successfully in the case of helico-axial pumps when a stabilization bush in accordance with the invention is provided between the first part rotor and the second part rotor so that a stabilization layer of the stabilization medium can be formed in the stabilization gap due to the pressure drop between the first part rotor and the second part rotor, with the stabilization medium particularly preferably being the actual multiphase mixture to be pumped so that the vibrations of the rotor can be damped to a presettable non-damaging degree by the stabilization layer.
In a particularly preferred embodiment, the first part rotor and the second part rotor are thus provided in a back-to-back arrangement in the pump housing so that the multiphase mixture can be supplied via an intake opening to a first input compression stage of the first part rotor and can be led off again from the first part rotor into a first cross-passage via a first output compression stage. The multiphase mixture can then be supplied from the first cross-passage to a second input compression stage of the second part rotor and can be led off again via a second output compression stage from the second part rotor via a second cross-passage and a pressure opening from the helico-axial pump. In this respect, the first output compression stage and the second output compression stage are each arranged adjacent to the stabilization bush.
As will be explained later more exactly in the drawings, the stabilization bush is designed and arranged at the rotor in this respect such that the stabilization gap is formed between the stabilization bush and the pump housing. Simultaneously or alternatively, the stabilization bush can, however, be designed and arranged at the rotor such that the stabilization gap is formed between the stabilization bush and the rotor.
In an embodiment likewise important for practice, a hydrodynamic stabilization element having a stabilization surface is additionally provided and designed such that the stabilization gap is formed before the stabilization surface so that a hydrodynamic stabilization layer can be formed from the stabilization medium in the stabilization gap in the operating state, wherein the additional stabilization element is preferably a cover ring which surrounds the helico-axial impeller in the peripheral direction so that the stabilization gap is formed between the cover ring and the pump housing. In this respect, such a cover ring can be provided at all the helico-axial impellers of a rotor or only at selected individual impellers, whereby the manufacture of the rotor naturally becomes much less complex and less expensive.
In another important embodiment of the present invention, the additional stabilization element is provided in the form of a stabilization sleeve between two adjacent compression stages at the rotor, wherein a stabilization sleeve can be provided between all the adjacent compressor stages of a rotor, whereby a particularly good damping of the vibrations of the rotor can above all be achieved at very high loads or, however, also only between individual selected pairs of compression stages, whereby the manufacture of the rotor naturally becomes much less complex and less expensive.
The stabilization sleeve can in this respect be designed and arranged at the rotor such that the stabilization gap is formed between the stabilization sleeve and the pump housing and/or the stabilization sleeve can also be designed and arranged at the rotor such that the stabilization gap is formed between the stabilization sleeve and the rotor. Specifically, both variants can be realized at one and the same rotor, whereby a particularly smooth running and a particularly good damping of the rotor vibrations can be achieved in specific cases.
If the geometry of the stabilization gap of the additional hydrodynamic stabilization element is set in accordance with the demands in a helico-axial pump in accordance with the invention, a pressure difference is formed over the stabilization gap in the operating state between the multiphase mixture which is at a higher pressure level and that which is at a lower pressure level such that a presettable flow of multiphase mixture is automatically adopted over the stabilization gap from the higher pressure level back to the lower pressure level, whereby a stabilization layer is automatically formed for the additional stabilization or damping of the damaging vibrations of the rotor.
However, additional measures can also be taken for the formation of the hydrodynamic stabilization layer, in particular when the vibrations which occur are very high or when the damping should be set in dependence on specific operating parameters, such as the load at which the pump is operated, or in dependent on the number of revolutions.
A multiphase mixture can thus particularly preferably be used which is already more highly compressed and which is taken from a compression stage in which the multiphase mixture is already more greatly compressed than it is compressed in the stage in which it is used for the formation of the stabilization layer. Alternatively or simultaneously, however, a multiphase mixture compressed in the same compression stage can be used for the formation of the hydrodynamic stabilization layer, which will be explained in detail with reference to
It is understood in this respect that the stabilization medium for the formation of the stabilization layer can also be provided by other external sources in specific cases, for example by a pressure reservoir or by a pump which provides the medium for the formation of the stabilization layer for introduction into the stabilization gap at a presettable pressure, specifically at a pressure which can be controlled and/or regulated. The stabilization medium for the formation of the stabilization layer also does not necessarily have to be the multiphase mixture to be pumped, but can also be another stabilization medium, e.g. an oil, water or another liquid or gaseous stabilization medium or a fluid.
It is furthermore possible, for example, that the pressure of the multiphase mixture introduced into the stabilization gap is controlled and/or regulated by means of a valve known per se. It is also possible, for example, to supply the multiphase mixture to the stabilization gap simultaneously or alternatively from different compression stages, whereby the pressure in the stabilization gap and thus the degree of damping or of stiffness of the vibration-capable rotor can therefore be set in a very simple manner and can be adapted very flexibly to different demands and changing operating conditions.
As will be explained later with reference to the drawings by way of example for particularly preferred embodiments, the stabilization gap can be provided at the additional stabilization element and naturally also at the stabilization bush, for example between the stabilization surface and the pump housing and/or also between the stabilization surface and the rotor.
In this respect, in a particularly preferred embodiment of the present invention, a supply passage can be provided which is made and arranged such that a multiphase mixture at a presettable pressure and, resulting therefrom, a presettable quantity of multiphase mixture, can be supplied through the supply passage to the stabilization gap, with the supply passage preferably being provided in a gap ring, for the formation of the hydrodynamic stabilization layer in the stabilization gap.
The stabilization element can thus, for example, be designed as a stator having a supply passage, wherein the supply passage is formed and arranged at the stator such that a presettable quantity of a stabilization medium, in particular of a multiphase mixture, can be supplied at a presettable pressure through the supply passage to the stabilization gap for the formation of the hydrodynamic stabilization layer in the stabilization gap.
In a further embodiment variant, the supply passage can be arranged and formed at the pump housing such that a presettable quantity of stabilization medium, in particular of multiphase mixture, can be supplied through the supply passage to the stabilization gap for the formation of the hydrodynamic stabilization layer in the stabilization gap.
Or, however, a supply passage is arranged and formed at the rotor such that a presettable quantity of stabilization medium, in particular of multiphase mixture, can be supplied through the supply passage to the stabilization gap for the formation of the hydrodynamic stabilization layer in the stabilization gap.
As already mentioned, in a helico-axial pump in accordance with the invention, the stabilization medium, in particular the multiphase mixture can in particular be supplied to the supply passage, particularly preferably from a compression stage, at which a higher pressure level is present than at that compression stage to which it is supplied as the stabilization medium. Alternatively or simultaneously, however, a multiphase mixture compressed in the same compression stage can also be used for the formation of the hydrodynamic stabilization layer.
The invention furthermore relates to a rotor for arrangement in a pump housing of a helico-axial pump for conveying a multiphase mixture. In this respect, the rotor, which is rotatably journallable about a longitudinal axis, includes a first part rotor and a second part rotor; and the first part rotor and the second part rotor include a compression stage having a helico-axial impeller and a stator for the compression of the multiphase mixture. In accordance with the invention, a hydrodynamic stabilization bush having a stabilization surface is provided and designed between the first part rotor and the second part rotor such that a stabilization gap can be formed before the stabilization surface so that a hydrodynamic stabilization layer can be formed from a stabilization medium in the stabilization gap in the operating state.
In a special embodiment, an additional hydrodynamic stabilization element having a stabilization surface can be provided in the form of a cover ring which surrounds the helico-axial impeller in the peripheral direction so that the stabilization gap can be formed between the cover ring and a pump housing of the helico-axial pump. Alternatively or simultaneously, the hydrodynamic stabilization element can, however, also be a stabilization sleeve which is provided, for example, between two adjacent compression stages so that the stabilization gap is formed between the stabilization sleeve and the pump housing.
A supply passage can specifically be provided which is made and arranged so that a presettable quantity of stabilization medium, in particular of multiphase medium, can be supplied through the supply passage to the stabilization gap for the formation of the hydrodynamic stabilization layer.
The invention further relates to a hybrid pump having a rotor in accordance with the invention for a helico-axial pump of the present invention for the conveying of a multiphase mixture.
Finally, the invention also relates to a method for the hydrodynamic journalling of a rotor in accordance with the invention in a helico-axial pump or in a hybrid pump in accordance with the present invention, wherein the rotor is rotatably journalled about a longitudinal axis in a pump housing and the rotor includes a compression stage having a helico-axial impeller and a stator for the compression of the multiphase mixture. In accordance with the invention, a hydrodynamic stabilization bush having a stabilization surface is provided and designed in the pump housing such that a stabilization gap is formed before the stabilization surface so that a hydrodynamic stabilization layer is formed from a stabilization medium in the stabilization gap for the hydrodynamic journalling of the rotor in the operating state.
The invention will be explained in more detail in the following with reference to the drawing. There are shown in a schematic representation:
a a compression stage of a helico-axial pump known from the prior art;
b a pump in accordance with
a an embodiment of
b the embodiment of
a a third embodiment in accordance with
b another embodiment in accordance with
c a further embodiment in accordance with
a a fourth embodiment in accordance with
b another embodiment in accordance with
The prior art described with reference to
it must be pointed out in another respect at this point that, for the better distinguishing of the invention from the prior art in the drawings, those reference numerals which relate to features or embodiments of the prior art are provided with a dash, whereas reference numerals for features of embodiments in accordance with the invention do not have a dash.
A first embodiment of a helico-axial pump in accordance with the invention in a back-to-back arrangement will be explained schematically with reference to
The helico-axial pump 1 for conveying a multiphase mixture M in accordance with
In the example of
An embodiment having an additional stabilization element in the form of a cover ring will be briefly discussed with reference to
The rotor 2 of the helico-axial pump 1 is rotatably journalled about a longitudinal axis A in the pump housing 6. The rotor 2 in this respect includes, for the compression of the multiphase mixture M in a manner known per se, the compression stages K having an helico-axial impeller 3 and a stator 4.
In accordance with the present invention, in addition to the stabilization bush 70 not explicitly shown in
In the present example of
For reasons of clarity, in each case only one or two compression stages K are in this respect shown in all the following Figures. Even if it is possible in principle that a helico-axial pump 1 in accordance with the invention only includes one single compression stage K, a helico-axial pump 1 in accordance with the invention, i.e. the first part rotor 21 and the second part rotor 22, will in practice include a plurality of compression stages K, for example up to sixteen compression stages K or even many more compression stages K, which are preferably arranged in series behind one another along the longitudinal axis A, so that a sufficient total compression of the multiphase mixture M can be produced in a manner known per se and the multiphase mixture M compressed in this manner can then, for example, be conveyed by a downstream pressure pump to a higher level and/or over long distances for further processing.
In the embodiment in accordance with
Due to the pressure difference ΔP, multiphase mixture M is pressed, as indicated by the small curved arrows M, from the higher pressure level shown at the right in accordance with the drawing into the stabilization gap 8, whereby the hydrodynamic stabilization level S is automatically formed between the stabilization surface 700 of the cover ring 7 and the pump housing 6, whereby the vibrations of the rotor 2 or of the part rotors 21, 22 are damped and the running of the rotor 2 is stabilized.
It is understood in this respect that, with a rotor 2 of the present invention, the cover ring 71 can be formed either at all helico-axial impellers 3 of the rotor or only at specific selected helico-axial impellers 3. In another respect, depending on the application or on the specific requirements, the cover ring 71 can completely cover a helico-axial impeller or a specific predeterminable region of the periphery of the helico-axial impeller 3.
A second embodiment in accordance with
In principle, an additional injection of stabilization medium can also take place into the stabilization gap S of the stabilization bush 70.
The embodiment of
In contrast, in the example of
The stabilization medium M can in this respect, as already described, be provided by an external pressure reservoir or by an external pump; it, however, preferably provided by another compression stage K which has a higher pressure level.
A third embodiment in accordance with
Another embodiment in accordance with
c shows a further variant of the embodiment in accordance with
In contrast,
In this respect, it is naturally also possible in specific cases that, alternatively or additionally to the stabilization sleeve 72 between two respective adjacent compression stages K, a stabilization sleeve 72 can also be provided within a compression stage K between the helico-axial impeller 3 and the stator 4. In this respect, the skilled person immediately understands that a stabilization sleeve 72 does not have to be provided at each compression stage or between each pair of compression stages K.
It is understood that all the above-described embodiments of the invention are only to be understood as examples or by way of example and that the invention in particular, but not only, includes all suitable combinations of the described embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 162 520.0 | May 2010 | EP | regional |
