Multi-stage turbomachine

Abstract

This multi-stage turbomachine comprises: – a central part (2) having at least two bearings (6) from which part there extends at least on one side a shaft (4) guided by said bearings (6) and on which shaft there are mounted, in cantilever fashion, two radial wheels (22, 34), the two radial wheels (22, 34) are separated from one another by a leak-tight partition (32), and each of the two radial wheels (22, 34) is mounted in its casing (24, 32, 40), each casing having a dedicated fluid inlet (24a, 42) and a dedicated fluid outlet (24b, 44).

Description

[0001] The present invention relates to a multi-stage turbomachine. It relates more particularly to the structure of such a machine.

[0002] A turbomachine may comprise several compression stages or several expansion stages or even one or more compression stages associated with one or more expansion stages.

[0003] It is particularly known to have a compressor-turbine type machine, also called compander (word obtained from the English words compress for compressor and expander for turbine or expander), in which there are one or more centrifugal compressor(s) and one or more turbine(s). These various stages are mechanically connected to a common motor (possibly a common generator) by means of a set of gears called gearbox (or its English equivalent, gearbox).

[0004] Such a machine provides excellent performance for fluid processing. It is modular and the same machine can work with one or more fluids: for example, it is possible to recover energy contained in one fluid to transmit it to another fluid.

[0005] One disadvantage of the known companders, however, is their relatively large footprint.

[0006] Another disadvantage of known companders is their structure, which requires a large number of bearings. There is one bearing for each turbine wheel or compressor, as well as four bearings for the engine and gearbox. This structure also has several shafts that must be sealed. All of this makes the resulting turbomachine relatively heavy.

[0007] Finally, due to the presence of the gearbox, it is most often necessary to have oil to lubricate the gearbox. For some applications, it is preferable not to have oil and the presence of the gearbox is then a disadvantage.

[0008] Document US 5,599,164 A discloses a centrifugal pump comprising an assembly of two centrifugal impellers each provided with a fluid inlet and outlet, the assembly being located cantilevered on one side of a central portion. Document DE 1,122,375 B discloses a centrifugal pump comprising an assembly of two centrifugal impellers separated by a wall.

[0009] Document EP 3 249 234 A1 discloses a turbocharger comprising on one side of an electric motor an assembly of two centrifugal wheels and on the other side a turbine. The two centrifugal wheels are arranged back to back and each mounted in their own housing, and a separating wall partially separates the two wheels.

[0010] Document JP 2012 / 251528 A discloses a turbomachine comprising on either side of a central part an assembly of two centrifugal wheels. The present invention then aims to provide a multi-stage turbomachine capable, like companders, of processing different fluids - for example a gas and a liquid - not having all the aforementioned drawbacks.

[0011] Thus, the new turbomachine will preferably have a more compact structure. This turbomachine, for equivalent performance, will also preferably be lighter than a compander. Advantageously, this turbomachine will operate without oil.

[0012] To this end, the present invention according to claim 1 proposes a multi-stage turbomachine comprising a central part having at least two bearings from which extends at least on one side a shaft guided by said bearings and on which two radial wheels are mounted in a cantilevered manner.

[0013] According to the present invention, the two radial wheels are separated from each other by a watertight partition, and in which each of the two radial wheels is mounted in its casing, each casing having a clean fluid inlet and a clean fluid outlet.

[0014] This structure makes it possible to obtain a turbomachine comparable to a compander with four stages with a smaller footprint while allowing it to work with several fluids (at least two fluids since at least two casings each have their own inlet and outlet, i.e. not common with another stage.

[0015] To facilitate the feeding of the two radial wheels and to have a compact structure, the two radial wheels mounted on the same cantilever are for example mounted back to back. Thus one wheel is fed from one side and the other from the opposite side.

[0016] To limit the number of parts and have a compact structure, it is possible to plan for the watertight bulkhead to form a wall common to each of the two housings.

[0017] To allow the use of fluids at significantly different temperatures, the watertight bulkhead has thermal insulation.

[0018] A multi-stage turbomachine as described above is intended to be used within a thermodynamic process. For better control of this process, it is advantageous for the central part to also include an electrical group chosen from the set of electric motors and electric generators.

[0019] According to the present invention, the casing corresponding to the distal wheel comprises the watertight partition as a proximal part common with the casing of the proximal wheel and a distal part in the form of a plate fixed on the casing of the proximal wheel

[0020] To obtain a structure equivalent to a compander, a multi-stage turbomachine as described above may comprise on either side of its central part a set of two radial wheels separated from each other by a watertight partition, and for each set each of the radial wheels is mounted in its casing, each casing having a clean fluid inlet and a clean fluid outlet.

[0021] Details and advantages of the present invention will appear more clearly from the following description, given with reference to the attached schematic drawing in which: There figure 1 is a cross-sectional view of a multi-stage turbomachine, and the figure 2 is an enlarged partial cross-sectional view of an alternative embodiment of the turbomachine of the figure 1 . This variant is not in accordance with the invention.

[0022] In the embodiment illustrated in the figure 1 , we have a turbomachine with four independent stages. The overall structure of this machine is described below. An electrical group 2, which can be a motor or a generator, is arranged in a central position. It is crossed by a shaft 4 supported by bearings 6 and having cantilevered shaft ends. Each shaft end carries two radial wheels.

[0023] The electrical group 2 is mounted in a housing 8. A magnet 10 is shrunk onto the shaft 4 and forms the rotor of the electrical group 2. A stator 12, separated from the rotor by an air gap and having windings, is mounted fixed in the housing 8. A connection box 14 makes it possible to electrically connect the electrical group 2.

[0024] The housing 8 is closed on each side by a cover 16 which incorporates a bearing 6 which is here a hydrodynamic bearing. The housing 8 incorporates an oil collector 18. To prevent any migration of oil towards the electrical group 2, seals 22 are provided inside each cover 16.

[0025] The bearings 6 of the shaft 4 are thus integrated into the covers 16. The parts of the shaft 4 extending outside the housing 8 (or more precisely its covers 16) are arranged cantilevered relative to the support of this shaft 4.

[0026] We notice on the figure 1 that the two sets of radial wheels arranged on either side of the electrical group 2 are symmetrical. Thus, in the following description, only one set, the one on the right on the figure 1 , will be described.

[0027] A first compressor is mounted adjacent to the cover 16 located on the right on the figure 1 This compressor comprises a first compressor wheel 22 and a first compression body in several pieces.

[0028] The first compressor wheel 22 is mounted on the shaft 4 and driven by it. The fluid (in gaseous or liquid phase) enters the first compressor wheel 22 in an axial direction (given by the axis of the shaft 4), from left to right on the figure 1 . In the preferred embodiment illustrated in the figure 1 , the shaft 4 has a section of so-called polygonal shape at the level of the first compressor wheel 22. The section of the shaft 4 is here of triangular shape (with slightly convex faces and rounded tops).

[0029] The first compression body guides the fluid supplying the first compressor wheel 22 upstream and downstream thereof. A casing 24 has an inlet 24a which channels the fluid supplying the first compressor wheel 22 in a radial direction as well as an outlet 24b which guides the compressed fluid downstream of the first compressor wheel 22. The casing 24 is fixed on a support 26 mounted on the corresponding cover 16. This support 26 has an inner wall which also participates in guiding the fluid to lead it towards the first compressor wheel 22. A sealing part 28 is arranged between the support 26 and the shaft 4 to seal the compressor. In the illustrated embodiment, the sealing part 28 has a labyrinth on the side of the shaft 4.On the inside of the casing 24, the sealing part guides the fluid to make it pass from a radial direction to its axial direction to supply the first compressor wheel 22. Finally, inside the casing 24, a deflector 30 guides the fluid upstream of the first compressor wheel 22 and opposite it.

[0030] After the first compressor wheel 22, that is to say moving away from the central part of the turbomachine which integrates the electrical group 2, a transverse wall 32 separates the first compressor from a second compressor. This second compressor comprises a second compressor wheel 34 as well as a compression body also in several parts.

[0031] The transverse wall 32, as suggested by its name, extends perpendicular to the axis of the shaft 4. It has an annular shape and houses in its center a sealing device 36. At this level, the shaft 4 also has a polygonal (triangular) shaped section. To achieve sealing, a ring having an inner surface matching the polygonal shape of the shaft 4 and a circular cylindrical outer surface is placed around the shaft 4. The sealing is then for example achieved on said ring by a labyrinth sealing system.

[0032] The transverse wall 32 has a face receiving the rear face of the first compressor wheel 22 and a face receiving the rear face of the second compressor wheel 34. Here, the rear face of a wheel is called its face with the largest diameter. As can be seen here, the two compressor wheels (first compressor wheel 22 and second compressor wheel 34) are thus mounted back-to-back. Each face of the transverse wall 32 has a housing for receiving the rear face of the corresponding compressor wheel. Beyond this housing, each face of the transverse wall 32 forms a wall for the diffuser of the corresponding compressor.

[0033] The casing 24 is configured on the rear side of the first compressor wheel 22 to receive the transverse wall 32. For this purpose, it has a hollow housing, preferably with a shoulder 38, to receive the transverse wall 32. The housing at the bottom of which the transverse wall 32 is placed is closed by a plate 40 carrying a fluid inlet pipe 42 and an outlet pipe 44. The plate 40 is fixed to the casing 24.

[0034] The inlet pipe 42 is arranged in a central position and it guides fluid towards the second compressor wheel 34 in such a way that this fluid is oriented axially by heading towards the figure 1 , for the second compressor wheel 34 on the right, from right to left. Inside the housing, a guide 46 ensures the guidance of the fluid towards the second compressor wheel 34 and in this wheel. At the wheel outlet, the compressed fluid is guided by a diffuser 48 (and by the transverse plate 32).

[0035] The second compressor wheel 34 is also mounted on a section of the shaft 4 having a polygonal section. However, it should be noted that the second compressor wheel 34 is mounted on a section of smaller dimensions (“diameter”) than the section of the shaft 4 receiving the first compressor wheel 22. A screw 50 fixes the second compressor wheel 34 at the end of the shaft 4. By this fixing, the fixing of the various elements arranged on the shaft 4, such as the sealing devices and the first compressor wheel 22, is ensured by stacking.

[0036] We note here that the two compression bodies are both nested within each other, with common elements, and at the same time independent since two distinct fluid circuits are created.

[0037] This creates two completely independent stages on the same end of a turbomachine shaft.

[0038] There figure 2 illustrates a variant embodiment of the figure 1 not in accordance with the invention. It uses the references of the figure 1 to designate similar parts. Here we find two radial wheels separated by a partition and mounted back to back, the two wheels being mounted on the same overhang of a shaft. We also find on the figure 2 , which is a partial section on an enlarged scale, a bearing (which in this example is also a hydrodynamic bearing but which could be of any other type, "classic" with bearings or magnetic, air, ...). In addition, the compressor body corresponding to the first compressor wheel or proximal wheel (closest to the bearing) is of suitable shape and has a housing for partially receiving the compressor body corresponding to the second compressor wheel. In the following, only the differences between the embodiment of the figure 2 and that of the figure 1 will be highlighted.

[0039] On the side of the central part, the cover 16 and the support 26 of the figure 1 are both grouped into a single part on which the casing 24 is mounted. The structure of the hydrodynamic bearing and the seal is revised. The sealing part therefore has a different shape.

[0040] The form of realization of the figure 2 corresponds for example to a turbomachine intended to work with two fluids at very different temperatures. We then recognize an insulating layer 52 which is arranged in the second compression body opposite the first compression body. Here, for example, it is possible to compress a cryogenic fluid and another fluid at “normal” temperature, for example close to ambient temperature.

[0041] The pressure in the second compression body in this other embodiment is relatively high. Therefore, the plate 40 closing this body and separating it from the outside is curved. The fluid supply is then adapted.

[0042] The embodiments described above therefore have multi-stage turbomachines, said stages being able to be independent of each other.

[0043] There figure 1illustrates a four-stage machine that is symmetrical. This symmetry is for illustrative purposes only. Two distinct sets can be found on either side of the central part of the machine.

[0044] The turbomachine proposed here has a single shaft and no gearbox. It can therefore have a limited footprint compared to a "compander" type machine described in the preamble. The number of bearings and seals to be produced is reduced compared to a "compander".

[0045] The turbomachine, in its proposed four-stage version (for example, we could have only two or three stages, i.e. two stages on one side and one or zero on the other) or, on the contrary, a greater number of stages.

[0046] The proposed turbomachine can also include one or more expansion wheels (and not only compression stages). It then takes place in a thermodynamic installation. It can be a driving force in the case where an engine is placed in the central part, or a generator if a generator is provided in the central part. It can also be an exchange between fluids, one or more expanders then transmitting energy to one or more compressors via the central shaft. For a four-stage machine, we can have several configurations depending on whether we have compressors or expansion turbines (or "expanders"). We can thus have the following configurations with an engine: Turbine-turbine / engine / compressor-compressor Turbine-turbine / engine / turbine-compressor Turbine-turbine / engine / compressor-turbine Turbine-compressor / engine / compressor-compressor Turbine-compressor / engine / compressor-compressor Turbine-compressor / engine / compressor-turbine Compressor-turbine / engine / compressor-compressor Compressor-turbine / engine / compressor-turbine Compressor-turbine / engine / turbine-turbine Compressor-compressor / engine / compressor-compressor

[0047] Similarly, with a generator in the central part, we can have all possible combinations of turbine and compressor on either side of the generator (except having only compressors which cannot then drive the generator).

[0048] Likewise, all combinations of turbines and compressors (except only turbines or only compressors) can be considered without an electrical unit in the central part to carry out energy exchanges between fluids only via the central shaft.

[0049] Each time, at least on one side of the central part, there is an assembly of two radial wheels, preferably mounted back-to-back, on the same overhang of a common shaft, a sealing device between the two radial wheels. The compression or expansion bodies corresponding to these two radial wheels are made so as to each receive a different fluid. Each body thus has a fluid inlet and outlet and there are two completely separate circuits: the inlet and outlet of one body and the inlet and outlet of the other body.

[0050] In the purely descriptive and non-limiting description, the radial wheels shown are mounted on the shaft by "polygon" type zones. Of course, other assemblies are possible: keys, teeth, Hirth type teeth, etc.

[0051] The outermost wheel is preferably, but not necessarily, mounted on a smaller shaft section. Mounting on two identical sections can also be considered. Wheels can be mounted using any means: thrust washers, bushings, labyrinth seals or others, etc.

[0052] The compression or expansion body corresponding to the outermost wheel, or distal wheel, is preferably fixed to the body (compression or expansion) corresponding to the innermost wheel. Thermal insulation may be provided between the two bodies.

[0053] The present invention is not limited to the embodiments described above and to the variants envisaged. It also relates to the variant embodiments within the reach of those skilled in the art within the scope of the following claims.

Claims

1. A multi-stage turbomachine comprising a central part (2) having at least two bearings (6) from which part there extends at least on one side a shaft (4) guided by said bearings (6) and on which shaft there are mounted, in cantilever fashion, two radial wheels (22, 34), wherein the two radial wheels (22, 34) are separated from one another by a leak-tight partition (32), the leak-tight partition (32) having thermal insulation (52), wherein each of the two radial wheels (22, 34) is mounted in its casing (24, 32, 40), each casing having a dedicated fluid inlet (24a, 42) and a dedicated fluid outlet (24b, 44), and the casing (32, 40) corresponding to the distal wheel (34) has the leak-tight partition(32) as a common proximal part with the proximal wheel casing (22) and a distal part (40) in the form of a plate attached to the casing (24) of the proximal wheel (22).

2. The multi-stage turbomachine according to claim 1, characterized in that the two radial wheels (22, 34) mounted on the same cantilever are mounted back to back.

3. The multi-stage turbomachine according to one of claims 1 or 2, characterized in that the leak-tight partition (32) forms a common wall with each of the two casings (24, 32, 40).

4. The multi-stage turbomachine according to one of claims 1 to 3, characterized in that the central part (2) further comprises an electric group selected from the set of electric motors and electric generators.

5. The multi-stage turbomachine according to one of claims 1 to 4, characterized in that it comprises on either side of its central part (2) an assembly of two radial wheels (22, 34), separated from one another by a leak-tight partition (32), and in that, for each assembly, each of the radial wheels (22, 34) is mounted in its casing (24, 32, 40), each casing having a dedicated fluid inlet (24a, 42) and a dedicated fluid outlet (24b, 44).

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