Integrally geared compressor with a combined axial-radial compressor unit

Abstract

The integrally geared compressor includes a bull gear supported for rotation in a gear casing, a first pinion shaft, and a second pinion shaft. A first compressor unit is mounted in an overhung fashion at a first end of the first pinion shaft, and a second compressor unit is mounted in an overhung fashion at a second end of the first pinion shaft, or at a first end, or at a second end of the second pinion shaft. A third compressor unit is mounted in an overhung fashion at one of the first end and the second end of the second pinion shaft. The second compressor unit and the third compressor unit are centrifugal compressor units. The first compressor unit comprises an axial compressor section and a centrifugal compressor section combined to one another.

Description

INTEGRALLY GEARED COMPRESSOR WITH A COMBINED AXIAL- RADIAL COMPRESSOR UNITDESCRIPTIONTECHNICAL FIELD

[0001] The present disclosure concerns improvements in gas compressors. Specifically, embodiments disclosed herein concern integrally geared compressors.BACKGROUND ART

[0002] Integrally geared compressors are often use to process air, carbon dioxide or steam. One advantage of integrally geared compressors is the possibility of multiple intercooling between compressor stages or units, as well as the possibility of driving sequentially arranged compressor stages or units at different rotational speeds.

[0003] GB 1048966 discloses a compressor arrangement including an electric motor, which drives a main gear meshing with a first pinion at a first end of a first compressor shaft, and with a second pinion at a first end of a second compressor shaft. A first compressor is drivingly coupled to the second end of the first compressor shaft and a second compressor is drivingly coupled to the second end of the second compressor shaft.

[0004] US2016 / 0230771 discloses a bull gear compressor, including a bull gear driven into rotation by a steam turbine. The steam turbine is drivingly coupled to a driving shaft coupled to the bull gear through a pinion keyed on the driving shaft. A main compressor is directly driven by the driving shaft. Further compressor units are drivingly coupled to the bull gear through driven shafts arranged peripherally around the bull gear.

[0005] WO2023 / 280435 discloses an integrally geared compressor comprising a bull gear supported for rotation in a gear casing. The compressor further comprises a first pinion shaft supported for rotation in the gear casing, and comprising a first pinion, which meshes with the bull gear. A second pinion shaft of the integrally geared compressor is supported for rotation in the gear casing, and comprises a second pinion,which meshes with the bull gear. A first compressor unit is mounted in an overhung fashion at a first end of the first pinion shaft. A second compressor unit is mounted in an overhung fashion at a second end of the first pinion shaft. A third compressor unit is mounted in an overhung fashion at a first end of the second pinion shaft. The second compressor unit and the third compressor unit are centrifugal compressor units. The first compressor unit comprises an axial compressor section. This integrally geared compressor according to the current art has several advantages over the prior art mentioned above, but can be further improved for better performances.

[0006] DE102016112453 discloses an integrally geared compressor, wherein a first shaft with a central pinion meshing with a bull gear has a first end mechanically connectable to a driver, specifically a steam turbine, and a second end mechanically connectable to a first compressor unit through a detachable coupling. The first compressor unit can be a combined axial-radial turbomachine, including a first axial stage and a second radial stage. A single shaft is therefore used to transmit power from the driver directly to the first compressor unit and, through an intermediate pinion keyed on the shaft, to the bull gear.SUMMARY

[0007] According to the present disclosure, starting from an integrally geared compressor according to WO2023 / 280435, improvements in terms of pressure ratio, for instance, can be achieved by providing a first compressor unit, which includes an axial compressor section in combination with a centrifugal compressor section arranged in sequence, with the centrifugal compressor section positioned at the outlet of the axial compressor section. The centrifugal compressor section and the axial compressor section are both mounted in an overhung fashion at the first end of the first pinion shaft, with the centrifugal compressor section positioned between the axial compressor section and the gear casing.

[0008] As used herein, mounted in an overhung fashion means mounted in a cantilever fashion, as will become apparent from the following detailed description of embodiments.

[0009] The combination of an axial compressor section and a radial, i.e. centrifugalcompressor section in the same compressor unit allows to reach high pressure ratios for the first compressor unit and reduces the overall number of compressor units as well as the dimensions and specifically the footprint of the integrally geared compressor.

[0010] The integrally geared compressor includes in general at least a first pinion shaft and a second pinion shaft. The first compressor unit, featuring a combined axial- radial compressor unit comprised of the axial compressor section and the centrifugal compressor section, is mounted in an overhung fashion on a first end of the first pinion shaft. A second compressor unit, featuring a centrifugal compressor unit, is mounted in an overhung fashion either at a second end of the first pinion shaft, or at one end of the second pinion shaft. A third compressor unit, featuring a centrifugal compressor section, is mounted in an overhung fashion either at the first or second end of the second pinon shaft. Thus, in one embodiment the first pinion shaft is drivingly coupled to only the combined axial-radial compressor unit, and the second pinion shaft is drivingly coupled, at both ends, to respective second and third compressor units, both featuring a centrifugal compressor unit.

[0011] Alternatively, in another embodiment, the first pinion shaft is drivingly coupled at a first end to the combined axial-radial compressor unit, and at the second end to a second compressor unit featuring a centrifugal compressor section. The third compressor unit, featuring a centrifugal compressor section, is drivingly coupled to a first end of the second pinion shaft. A fourth compressor unit, featuring a centrifugal compressor section, can be coupled to the second end of the second pinion shaft.

[0012] Using a high Mach axial compressor section in the first compressor unit allows a substantial reduction of the overall compressor size, avoiding the need for impellers having a large flow coefficient. Impellers with large flow coefficients often have a limited peripheral speed. The use of a double flow architecture is also avoided.

[0013] In embodiments disclosed herein, the axial compressor section comprises a single annular array, or row, of rotary blades, arranged upstream of an axial inlet of the centrifugal impeller of the centrifugal compressor section.

[0014] In some embodiments, the first compressor unit further comprises: a firstannular set of stationary vanes upstream of the annular row of rotary blades of the axial compressor section; and a second annular set of stationary vanes downstream of the annular row of rotary blades of the axial compressor section and upstream of the centrifugal impeller.

[0015] One, or both the annular sets of stationary vanes can include variable inlet guide vanes, adapted to adjust the process gas flow to the operating conditions of the compressor, for instance based on the flowrate.

[0016] The first compressor unit advantageously includes an axial gas inlet and a radial gas outlet, the radial gas outlet being positioned between the axial gas inlet and the gear casing. A compact construction is thus achieved for the first compressor unit.

[0017] In some embodiments, the axial compressor section of the first compressor unit comprises a single axial stage. In some embodiments, the centrifugal compressor section of the first compressor unit comprises a single centrifugal impeller, which can be an unshrouded impeller, for instance. In other embodiments, the impeller can be a shrouded impeller.

[0018] In some embodiments, the first compressor unit comprises a compressor casing with an axial inlet aperture and a rotor core housed for rotation in the compressor casing. The rotor core can comprise a proximal end, connected in an overhung fashion to the first end of the first pinion shaft, and a distal end facing the axial inlet aperture of the compressor casing.

[0019] Furthermore, the rotor core can comprise a first core section, whereto the annular row of rotary blades of the axial compressor section are constrained. The rotary blades of the axial compressor section can be constructed as separate components and mounted on the first core section. In other embodiments, the first core section and the rotary blades can be manufactured as a single body, for instance by additive manufacturing. In this case the disk and the blades form a so-called “blisk” rotor, aka integrally bladed rotor, where the blades and the disk are monolithic.

[0020] In some embodiments, the rotor core can comprise a second core section positioned between the first core section and the first end of the of the first pinion shaft. The second core section can form a hub of the centrifugal impeller, integral with bladesof the centrifugal impeller. The second core section can be directly connected in a cantilever fashion to the first end of the first pinion shaft.

[0021] In some embodiments, the rotor core can include a third core section forming a distancing ring between the first core section and the second core section, i.e. positioned between the first core section and the second core section. The second annular set of stationary vanes of the axial compressor section, which are positioned between the rotary blades of the axial compressor section and the centrifugal impeller of the centrifugal compressor section, can surround the third core section.

[0022] The core sections forming the rotor core can be assembled to one another as separate components, for instance by screws or bolts, or other mechanical coupling devices providing a reversible coupling between the core sections of the rotor core. Each core section can be hollow, such that, once assembled, the core sections form a hollow rotor core. The hollow rotor core provides a light structure, which can be easily mounted in an overhung manner. The reversible coupling is beneficial in terms of maintenance or repair of the rotor, as components of the axial compressor section and of the centrifugal compressor section can be replaced independently from one another.

[0023] Further embodiments and advantageous features of the integrally geared compressor are outlined below and set out in the enclosed claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Reference is now made briefly to the accompanying drawings, in which:Fig. l is a sectional view of an integrally geared compressor according to the present disclosure;Fig.2 is an enlargement of the first compressor unit of the compressor shown in Fig. l; andFig.3 is an enlargement of the first compressor unit in a further embodiment.DETAILED DESCRIPTION

[0025] A novel integrally geared compressor is disclosed, to improve the inlet flowrate and the pressure ratio without increasing the overall footprint of the machine. The compressor comprises a bull gear, which drives into rotation two or more pinionshafts peripherally arranged around the bull gear. Each pinion shaft includes a respective pinion keyed thereon or formed as a single integral piece therewith. Each pinion meshes with the bull gear. The pinions may have different diameters and different number of teeth, so that the pinion shafts revolve at different rotational speeds. A compressor driver is drivingly coupled to a central shaft, which rotates the bull gear. The rotary motion is transmitted from the bull gear to the pinions meshing therewith. Compressor stages are drivingly coupled to the pinion shafts. The most upstream compressor stage, i.e. the most upstream compressor unit, is a combined compressor stage, comprising an axial compressor section and a radial compressor section, i.e. a centrifugal compressor section.

[0026] The second and subsequent compressor units can be centrifugal compressor units, arranged in sequence for further compression of the gas flow delivered by the axial-radial compressor unit. Intercoolers can be provided between one or more pairs of sequentially arranged compressor units, to remove heat from the partly compressed process gas and improve the overall efficiency of the multistage, integrally geared compressor.

[0027] The most upstream axial-radial compressor unit is adapted to process larger inlet flowrates than usual centrifugal compressor units, and reaches high pressure ratios. A compact machine is thus obtained, adapted to process large volumetric gas flowrates.

[0028] Turning now to the drawings, Fig.1 shows a sectional view of an integrally geared compressor 1 according to a plane containing a rotation axis X-X of a bull gear 5 supported for rotation in a gear casing 3.

[0029] The bull gear 5 is drivingly coupled to an input shaft 7, which can be driven into rotation by a driver schematically shown at 8, for instance an electric motor, or any other suitable driver, such as a gas or steam turbine, a reciprocating internal combustion engine, or the like. Thus, the input shaft 7 transmits power from the driver 8 centrally to the bull gear 5, which is keyed on the input shaft 7. The bull gear 5 is supported by means of bearings schematically shown at 11, 13. The bull gear 5 can rotate at the speed of the driver 8, or at a different speed, e.g., if a speed manipulation device, such as a gearbox (not shown), is arranged along the shaft line between thedriver 8 and the input shaft 7.

[0030] The compressor 1 further comprises a plurality of pinion shafts which receive power from the bull gear 5 and drive each one or more compressor units. In Fig.l two pinion shafts are shown. It shall be understood that a larger number of pinion shafts can be arranged around the bull gear 5.

[0031] A first pinion shaft 15 is supported for rotation around a rotation axis B-B by bearings 17, 19. A first pinion 21 is keyed on, or integrally formed with the first pinion shaft 15, between bearings 17, 19. The first pinion 21 meshes with the bull gear 5. The first pinion shaft 15 is therefore driven into rotation by the driver 8 at a rotational speed which is a function of the transmission ratio between the bull gear 5 and the first pinion 21.

[0032] A second pinion shaft 23 is supported for rotation around a rotation axis C-C by bearings 25, 27. A second pinion 29 is keyed on, or integrally formed with the second pinion shaft 23. The second pinion 29 meshes with the bull gear 5. The second pinion shaft 23 therefore rotates at a rotational speed which is a function of the transmission ratio between the bull gear 5 and the second pinion 29. In some embodiments, the rotation speed of the second pinion shaft 23 can be higher than the rotation speed of the first pinion shaft 15.

[0033] The first pinion shaft 15 comprises a first end 15.1 and a second end 15.2, projecting from the gear casing 3 at opposite sides thereof. I.e. the first end 15.1 and the second end 15.2 project in a cantilever fashion beyond the bearings 17, 19. The integrally geared compressor 1 includes a first, most upstream compressor unit 31 mounted in an overhung fashion from the first end 15.1 of the first pinion shaft 15, and driven by the latter at a first rotational speed. A second compressor unit 33 is mounted in an overhung fashion from the second end 15.2 of the first pinion shaft 15, and is driven at the same rotational speed as the first compressor unit 31.

[0034] As shown in the drawings, an overhung compressor unit is mounted at the end of the respective pinion shaft in a cantilever fashion. In other words, a compressor unit mounted in an overhung fashion is a compressor unit that is supported in a cantilever fashion at one end of the respective pinion shaft, said end protruding beyond therespective bearing. Thus, the compressor unit mounted in an overhung fashion is supported by the bearings of the pinion shaft.

[0035] The first compressor unit 31 is a combined axial-radial compressor unit, and will be described in more detail later with reference to Fig.2.

[0036] In this embodiment, the compressor 1 further comprises a third compressor unit 35 and a fourth compressor unit 37 connected in a overhung fashion to a first end23.1 and to a second end 23.2, respectively, of the second pinion shaft 23.

[0037] In other embodiments, not shown, only the third compressor unit 35 can be foreseen. In yet further embodiments, not shown, an additional pinion shaft or several additional pinion shafts can be supported for rotation in the gear housing 3 and each of said additional pinion shafts can include one or two compressor units at one or both respective ends, mounted in an overhung fashion.

[0038] The second compressor unit 33 can include a centrifugal compressor section, preferably comprised of a single centrifugal impeller 33.1 mounted in an overhung fashion on the second end 15.2 of the first pinion shaft 15. The centrifugal impeller33.1 can be housed in a casing 33.2 of the second compressor unit 33. Reference number 33.3 indicates an axial gas inlet of the second compressor unit 33. Gas processed through the centrifugal impeller 33.1 flows through a diffuser 33.4 into a scroll 33.5 and therefrom in a gas outlet 33.6. The gas is slowed down in the diffuser 33.4 and kinetic energy of the gas exiting the centrifugal impeller 33.1 is converted into pressure.

[0039] The gas inlet 33.3 of the second compressor unit 33 can be fluidly coupled to an outlet of the first compressor unit 31 (to be described) through a connection line 41. An intercooler 43 can be positioned along the connection line 41. The intercooler 43 and the connection line 41 are shown only schematically.

[0040] The gas outlet 33.6 of the second compressor unit 33 is fluidly coupled through a connection, as shown at A, to an inlet of the third compressor unit 35. An intercooler (not shown) can be positioned along the line connecting the gas outlet, i.e. the delivery side 33.6 of the second compressor unit 33, to the gas inlet, i.e. the suction side of the third compressor unit 35.

[0041] The third compressor unit 35, which is connected in an overhung fashion to the first end 23.1 of the second pinion shaft 23, can include a centrifugal compressor section, preferably comprised of a single centrifugal impeller 35.1, mounted in an overhung fashion on the first end 23.1 of the second pinion shaft 23. The centrifugal impeller 35.1 can be housed in a casing 35.2 of the third compressor unit 35. Reference number 35.3 indicates an axial gas inlet of the third compressor unit 35. Gas processed through the centrifugal impeller 35.1 flows through a diffuser 35.4 into a scroll 35.5 and therefrom in a gas outlet 35.6. The gas is slowed down in the diffuser 35.4 and kinetic energy of the gas exiting the centrifugal impeller 35.1 is converted into pressure.

[0042] The delivery side 35.6 of the third compressor unit 35 is fluidly coupled through a connection, shown at B, to an inlet of the fourth compressor unit 37. An intercooler (not shown) can be positioned along the line connecting the outlet, i.e. the delivery side of the third compressor unit 35, to the inlet, i.e. the suction side of the fourth compressor unit 37.

[0043] The fourth compressor unit 37 can include a centrifugal compressor section, preferably comprised of a single centrifugal impeller 37.1, mounted in an overhung fashion on the second end 23.2 of the second pinion shaft 23. The centrifugal impeller 37.1 can be housed in a casing 37.2 of the fourth compressor unit 37. Reference number 37.3 indicates an axial gas inlet of the fourth compressor unit 37. Gas from the centrifugal impeller 37.1 flows through a diffuser 37.4 into a scroll 37.5 and therefrom in a gas outlet or delivery side 37.6. The kinetic energy of the gas is converted into pressure through the diffuser 37.4.

[0044] In other embodiments, not shown, the first pinion shaft can be drivingly coupled in an overhung fashion at a first end to the first compressor unit 31, while the second and third compressor units are drivingly coupled in an overhung fashion at the first and second end of the second pinion shaft. In this embodiment, the integrally geared compressor may have only three compressor units. In other embodiments, a further pinion shaft can be provided, which can be drivingly coupled at one or at both ends with respective additional compressor units.

[0045] With continuing reference to Fig.1, an enlargement of the first compressorunit 31 is shown in Fig.2.

[0046] The first compressor unit 31 comprises an axial compressor section 51 and a radial, i.e. centrifugal compressor section 53. The axial compressor section 51 and the centrifugal compressor section 53 comprise a common rotor core 55, which is integral with rotary blades of the axial compressor section 51 and with a centrifugal impeller of the centrifugal compressor section, as further described below.

[0047] More specifically, in the illustrated embodiment, the axial compressor section 51 comprises a single annular row of rotary blades 57, which are rigidly constrained to a first core section 55.1 of the rotor core 55. In some embodiments, the blades 57 and the first core section 55.1 are formed as a single monolithic body, featuring a so- called “blisk” rotor component.

[0048] In some embodiments, the first core section 55.1 is connected to a second core section 55.2 and athird core section 55.3. The third core section 55.3 is positioned between the first core section 55.1 and the second core section 55.2.

[0049] The second core section 55.2 forms a hub 59.1 of a centrifugal impeller 59. The centrifugal impeller 59 comprises impeller blades 59.2, 59.3. The impeller blades 59.2, 59.3 and the hub 59.1 are formed as a single monolithic body. In the embodiment shown in Fig.2, the impeller 59 is an unshrouded impeller having two sets of blades 59.2, 59.3. In other embodiments, not shown, the impeller 59 can be a shrouded impeller. In some embodiments, the impeller 59 may have a single set of impeller blades.

[0050] The first core section 55.1, second core section 55.2 and third core section 55.3 can be connected to one another by a reversible coupling. As used herein “reversible coupling” is a connection that allows the core sections to be disconnected, i.e. decoupled from one another, or disassembled, for instance for maintenance or repairing purposes. A reversible coupling can include screws or bolts 61, for instance. A similar reversible coupling can be provided to connect the second core section 55.2 to the first end 15.1 of the first pinion shaft 15. The first end 15.1 of the first pinion shaft 15 can have a flange 15.3 whereto the second core section 55.2 is connected.

[0051] The core sections 55.1, 55.2, 55.3 can be decoupled, i.e. separated from one another individually. For instance the first core section 55.1 can be detached from thesecond and third core sections 55.2, 55.3 which remain attached to one another and to the flange 15.3 of the first pinion shaft 15. Alternatively, the unit formed by the first core section 55.1 and the third core section 55.3 can be detached and removed from the second core section 55.2, which can remain attached to the flange 15.3 of the first pinion shaft 15.1. Or, the entire rotor 55 can be detached from the flange 15.3 of the first pinion shaft 15. The use of individual reversible couplings 61 offers increased flexibility to address different maintenance or repairing needs.

[0052] Each core section 55.1, 55.2 and 55.3 can have an annular protrusion facing the rotation axis B-B. The annular protrusions of the core sections 55.1, 55.2, and 55.3 are labeled 55.4, 55.5 and 55.6, respectively. The annular protrusions 55.5, 55.5, and 55.6 provide a concentrated additional rotary mass, which improve the rotor-dynamic of the rotor core.

[0053] An ogival terminal portion 63 can be coupled at a distal end of the rotor core 55 and rotating therewith.

[0054] Differently from known stacked compressor disks, where a central tie rod connects all rotor disks together, the separate coupling of each rotor core section to the neighboring one enables not only partial disassembly of the rotor core, but also a stationary ogival terminal portion to be used, instead of a rotary ogival terminal portion. According to the embodiment illustrated in the drawings, the ogival terminal portion 63 is stationarily supported in an outer compressor casing 65. For example, the ogival terminal portion can be mechanically supported by radial struts 64, which connect the ogival terminal portion 63 to the outer compressor casing 65. The use of a stationary, i.e. non-rotating ogival terminal portion 63 can be advantageous in that it reduces the rotating mass of the shaft.

[0055] In the embodiment of Fig.2, as the ogival terminal portion 63 is stationary and does not form an integral part of the rotary rotor core, a closing plate 55.7 provides a front closure at the forward side the rotor core.

[0056] In the embodiment of Figs 1 and 2, the rotor core 55 forms therefore an empty, generally cylindrical core, comprised of three core sections 55.1, 55.2, and 55.3. The first core section 55.1 and the second core section 55.2 integrally form the rotary blades57 of the axial compressor section, and the blades 59.2, 59.3 of the radial compressor section 53, respectively. Both the annular row of axial rotary blades 57 and the centrifugal impeller 59 can be disassembled by removing the stationary ogival terminal portion 63 and the front closing plate 55.7, such that the peripheral screws o bolts 61 which connect the rotor core sections 55.1, 55.2, 55.3 to one another become accessible and can be unscrewed to selectively remove the whole rotor or only part thereof from the flange 15.3 of the first pinion shaft 15.

[0057] In the embodiment of Figs. 1 and 2, a set of stationary vanes 67 are positioned upstream of the annular row of rotary blades 57 of the axial compressor section 51, with respect to the direction of flow (arrow F) of the gas processed through the first compressor unit 31. In some embodiments, the stationary vanes 67 can be variable inlet guide vanes, i.e. each stationary vane 67 can be adjustable angularly around a respective rotation axis orthogonal to the rotor axis B-B. Reference number 68 indicates actuation devices adapted to adjust the angular orientation of the stationary vanes 67 around the respective radial axes.

[0058] A set of stationary vanes 69 are arranged downstream the axial rotary blades 57, between the latter and the axial inlet of the centrifugal impeller 59. In some embodiments, the stationary vanes 69 can be variable inlet guide vanes, i.e. each stationary vane 69 can be adjustable angularly around a respective rotation axis orthogonal to the rotor axis B-B. Reference number 70 indicates actuation devices adapted to adjust the angular orientation of the stationary vanes 69 around the respective radial axes orthogonal to the rotation axis B-B.

[0059] The outer compressor casing 65 has a gas inlet aperture 66, i.e a suction side, which extends in an axial direction, i.e. substantially parallel to the rotation axis B-B of the pinion shaft 15 and of the rotor core 55.

[0060] The outer compressor casing 65 forms, in combination with the rotor core 55, a flow path for the process gas, which extends in an axial and radial direction, from the suction side, i.e. inlet aperture 66 of the compressor casing 65, to a diffuser 71 of the centrifugal compressor section 53. In some embodiments, the diffuser 71 can be a bladed diffuser. Stationary blades of the diffuser 71 are schematically shown at 73.

[0061] The diffuser 71 extends radially with respect to the rotation axis B-B and receives a flow of accelerated process gas discharged at a radial outlet end of the impeller 59. The gas delivered by the impeller 59 slows down in the diffuser 71, thus converting kinetic energy thereof into pressure. Compressed process gas is collected at a scroll 75 (Fig.1), which is fluidly coupled to a discharge side, or outlet 77 of the first compressor unit 31. The outlet 77 is fluidly coupled through line 41 and intercooler 43 with the suction side of the second compressor unit 33.

[0062] Fig.3 illustrates an enlarged sectional view, similar to the sectional view of Fig.2, of a modified embodiment of the first compressor unit 31. The embodiment of Fig.3 differs from the embodiment of Figs 1 and 2 mainly in that the rotor core comprises a first core section 55.1 and a second core section 55.2, which are directly coupled to one another with reversible connection members. In both embodiments, the core sections are hollow, such that a hollow rotor core is obtained, which has a reduced weight. The reversible coupling between the core sections 55.1, 55.2 (and 55.3 if provided) allows disassembling of the rotor in components which can be repaired, subject to maintenance, or replaced, individually and independently one from the other.

[0063] The reversible coupling comprises coupling devices arranged around the rotation axis of the first pinion shaft.

[0064] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS1. An integrally geared compressor, comprising: a bull gear supported for rotation in a gear casing and coupled to an input shaft adapted to be driven into rotation by a driver; a first pinion shaft supported for rotation in the gear casing, and comprising a first pinion, which meshes with the bull gear; and a second pinion shaft supported for rotation in the gear casing, and comprising a second pinion, which meshes with the bull gear; wherein: a first compressor unit is mounted in an overhung fashion at a first end of the first pinion shaft; a second compressor unit is mounted in an overhung fashion at a second end of the first pinion shaft or at one of a first end and a second end of the second pinion shaft; a third compressor unit is mounted in an overhung fashion at the other of the first end and second end of the second pinion shaft; the second compressor unit and the third compressor unit are centrifugal compressor units; the first compressor unit comprises an axial compressor section and a centrifugal compressor section; and the axial compressor section comprises an annular row of rotary blades arranged upstream of an axial inlet of a centrifugal impeller of the centrifugal compressor section.

2. The integrally geared compressor of claim 1, wherein the first compressor unit further comprises: a first annular set of stationary vanes upstream of the annular row of rotary blades of the axial compressor section; and a second annular set of stationary vanes downstream of the annular row of rotaryblades of the axial compressor section and upstream of the centrifugal impeller.

3. The integrally geared compressor of claim 2, wherein the first annular set of stationary vanes comprises variable inlet guide vanes.

4. The integrally geared compressor of claim 2 or 3, wherein the second annular set of stationary vanes comprises variable inlet guide vanes.

5. The integrally geared compressor of claim any one of the preceding claims, wherein the first compressor unit comprises an axial gas inlet and a radial gas outlet, the radial gas outlet being positioned between the axial gas inlet and the gear casing.

6. The integrally geared compressor of any one of the preceding claims, wherein the axial compressor section of the first compressor unit comprises a single axial stage.

7. The integrally geared compressor of any one of the preceding claims, wherein the centrifugal compressor section of the first compressor unit comprises a single centrifugal impeller.

8. The integrally geared compressor of any one of the preceding claims, wherein the first compressor unit comprises a compressor casing with an axial aperture, and a rotor core housed for rotation in the compressor casing; wherein the rotor core comprises a proximal end connected in an overhung fashion to the first end of the first pinion shaft, and a distal end facing the axial aperture of the compressor casing; and wherein the rotor core comprises:- a first core section constrained to the annular row of rotary blades of the axial compressor section, and- a second core section positioned between the first core section and the first end of the of the first pinion shaft, the second core section forming a hub of the centrifugal impeller, integral to blades of thecentrifugal impeller.

9. The integrally geared compressor of claim 8, when depending upon claim 2, wherein the rotor core comprises a third core section forming a distancing ring between the first core section and the second core section; and wherein the second annular set of stationary vanes of the axial compressor section surround the third core section.

10. The integrally geared compressor of claim 8 or 9, wherein the core sections are assembled to one another with reversible connection devices.

11. The integrally geared compressor of claim 8, 9 or 10, wherein the rotor core is hollow.

12. The integrally geared compressor of any one of claims 8 to 11, wherein at least one core section, and preferably each core section comprises an annular projection oriented radially inwardly towards the rotation axis of the first pinion shaft.

13. The integrally geared compressor of any one of claims 8 to 12, wherein each core section is mechanically coupled to at least one adjacent core section by a reversible coupling comprising coupling devices arranged around the rotation axis of the first pinion shaft.

14. The integrally geared compressor of any one of the preceding claims, further comprising an ogival terminal portion coaxial to the first pinion shaft and axial compressor section.

15. The integrally geared compressor of claim 14, wherein the ogival terminal portion is stationarily coupled with an outer compressor casing of the first compressor unit.

16. The integrally geared compressor of any preceding claim, wherein the blades of the annular row of rotary blades are monolithically formed as a singlepiece with a respective core section.

17. The integrally geared compressor of any one of the preceding claims, wherein the centrifugal compressor section of the first compressor unit comprises a vaned diffuser.

18. The integrally geared compressor of any one of to the preceding claims, wherein: the second compressor unit comprises a single centrifugal compressor impeller; and the third compressor unit comprises a single centrifugal compressor impeller.

19. The integrally geared compressor of any one of the preceding claims, wherein a gas outlet of the centrifugal compressor section of the first compressor unit is fluidly coupled to a gas inlet of the second compressor unit, through an intercooler.

20. The integrally geared compressor of any one of the preceding claims, wherein a gas inlet of the third compressor unit is fluidly coupled to a gas outlet of the second compressor unit, through an intercooler.

21. The integrally geared compressor of any one of the preceding claims, comprising a fourth compressor unit supported in an overhung fashion at a second end of the second pinion shaft; wherein the fourth compressor unit comprises a centrifugal impeller; and wherein the second compressor unit is mounted at the second end of the first pinion shaft and the third compressor unit is mounted at the first end of the second pinion shaft.

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