Integrally geared turbomachinery system with at least two impellers having different rotating speeds

Abstract

Integrally geared turbomachinery system (200, 300) comprising a wheel gear (90) configured to rotate around a rotating axis (R) and at least a couple of pinion shafts (10, 20) which are mechanically coupled to the wheel gear (90) and which have respectively a first axis (X) and a second axis (Y) coincident with each other and parallel to the rotating axis (R). The wheel gear (90) comprises a first portion (91) having a first diameter and a second portion (92) having a second diameter which is smaller than the first diameter. A first pinion shaft (10) is mechanically coupled to the first portion (91) of the wheel gear (90) and is configured to rotate around the first axis (X) at a first rotational speed. A second pinion shaft (20) is mechanically coupled to the second portion (92) of the wheel gear (90) and is configured to rotate around the second axis (Y) at a second rotational speed which is different from the first rotational speed.

Description

TITLEIntegrally geared turbomachinery system with at least two impellers having different rotating speedsDESCRIPTIONTECHNICAL FIELD

[0001] The subject-matter disclosed herein relates to an integrally geared turbomachinery system with at least a couple of impellers having different rotating speeds.BACKGROUND ART

[0002] Known integrally geared turbomachinery systems consist of a central low-speed wheel (known as “bull gear”) and multiple pinion gears on the outside of it driving plurality of high-speed shafts, in particular pinion shafts. By changing each of the gear ratios, it is possible to operate each shaft at different speed. It is to be noted that, nowadays, the gear ratio allowed by the bull gear is technologically limited, typically around 16-17.

[0003] In order to reduce the footprint of the system, one known configuration is to have two impellers mounted on a single shaft (i.e. provide the shaft with two impellers located at the opposite ends of the shaft). However, since the shaft is rotating at one specific rotational speed, it implies that at least one (or even both) of the two impellers is not fully optimized. For example, if the turbomachinery system is a double-stage compressor system which is driven by the same shaft (i.e. the stages are running at the same rotational speed m) the downstream stage has a reduced flow coefficient (which is calculated asm / pMD3 w^ere m / p is the volumetric flow V) with respect to the upstream stage since the volumetric flow at the downstream stage is less than the volumetric flow at the upstream stage (Vdown< Vup) due to the fact that the flow processed by the downstream stage has already been processed (i.e. compressed) by the first stage. It is to be noted that the difference between the volumetric flow processed by the stages is particularly evident in case the fluid has good compressibility (e.g. CO2). In any case, since the rotational speed is the same for both impellers, the flow coefficientof the first impeller and / or the flow coefficientof the second impeller may not be the optimal flow coefficientbut instead an unoptimized flow coefficient , thus resulting in a poorly optimized efficiency.

[0004] The same is true also, for example, if an intercooler or a fluid extract! on / inj ection is provided between the upstream stage and the downstream stage. In particular, if the temperature of the processed flow is decreased between the upstream stage and the downstream stage, the same applies to the volumetric flow (Vdown< Vup) as p depends on temperature.

[0005] Therefore, it would be desirable to have an integrally geared turbomachinery system with reduced footprint and which has all the impellers operating at the optimal rotating speed without the standard bull gear technological limitations, in order to achieve a higher efficiency.SUMMARY

[0006] According to an aspect, the subject-matter disclosed herein relates to an integrally geared turbomachinery system comprising a wheel gear configured to rotate around a rotating axis and at least a couple of pinion shafts mechanically coupled to the wheel gear. The pinion shafts have a first and a second axis respectively, the first and second axes being coincident with each other and parallel to the rotating axis. The wheel gear comprises a first portionhaving a first diameter and a second portion having a second diameter which is smaller than the first diameter. A first pinion shaft is mechanically coupled to the first portion of the wheel gear and is configured to rotate around a first axis at a first rotational speed. A second pinion shaft is mechanically coupled to the second portion of the wheel gear and is configured to rotate around a second axis at a second rotational speed which is different from the first rotational speed.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:Fig. 1 shows a (partial) schematic diagram of an integrally geared turbomachinery system of the prior art,Fig. 2 shows a (partial) schematic diagram of a first embodiment of an innovative integrally geared turbomachinery system with at least a couple of coaxial impellers having different rotating speeds, andFig. 3 shows a (partial) schematic diagram of a second embodiment of an innovative integrally geared turbomachinery system with at least a couple of coaxial impellers having different rotating speeds.DETAILED DESCRIPTION OF EMBODIMENTS

[0008] According to an aspect, the subject-matter disclosed herein relates to an innovative integrally geared turbomachinery system, i.e. a turbomachinery system which has several impellers (compressors and / or expanders) driven by a main gear. In other word, the main gear is used to mechanically transmit themotion to several pinion shafts in which the pinion engages the teeth of the wheel of the main gear. In order to minimize the footprint, the main gear drives several couple of pinion shafts which have an axis of rotation parallel to the axis of rotation of the main hear, each pinion shaft being coupled to an overhung impeller. Therefore, each couple of pinion shaft has a pair of impellers which have a parallel axis of rotation. The innovative turbomachinery system has a main gear with two portions: a first portion having a first diameter and being coupled to a first pinion shaft of the couple, so to rotate a first impeller at a first rotational speed, and a second portion having a second diameter smaller than the first diameter and being coupled to a second pinion shaft of the couple, so to rotate a second impeller at a second rotational speed different from the first rotational speed. In other words, the innovative system allows to rotate each impeller of the system at a different rotational speed so to rotate each impeller at its optimal speed and therefore to maximize the efficiency of the machines.

[0009] Reference now will be made in detail to embodiments of the disclosure, examples of which are illustrated in the drawings. The examples and drawing figures are provided by way of explanation of the disclosure and should not be construed as a limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. In the following description, similar reference numerals are used for the illustration of figures of the embodiments to indicate elements performing the same or similar functions. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0010] Referring now to the drawings, Fig. l is a partial schematic diagram of a known integrally geared turbomachinery system 100, Fig. 2 and Fig. 3 are respectively partial schematic diagrams of a first embodiment 200 and a second embodiment 300 of an innovative integrally geared turbomachinery systemwith at least two impellers having different rotating speeds.

[0011] The innovative integrally geared turbomachinery systems herein disclosed essentially differ from the prior-art integrally geared turbomachinery system 100 of Fig. 1 in that at least a couple of impellers of the system having coincident rotation axes (or “coaxial”) can rotate at different rotating speeds, thus allowing each impeller to rotate at its optimal speed and therefore to maximize the efficiency of the machines without increasing the footprint. In particular, innovative integrally geared turbomachinery systems comprise a stepped wheel gear, i.e. a wheel gear having two portions with different diameters, each portion being mechanically coupled to a different pinion shaft of at least a couple of pinion shafts which have coincident rotation axes (or “coaxial”), so that the impellers driven by each couple of pinion shafts may rotate at different rotating speeds.

[0012] In Figure 2 there is shown, for example and without limitation, a first embodiment of an innovative integrally geared turbomachinery system generally indicated with reference numeral 200. The system 200 comprises a wheel gear 90 and a couple of pinion shafts 10 and 20, in particular a couple of pinion shafts 10 and 20 which are mechanically coupled to the wheel gear 90 and mechanically coupled to each other, as it will be apparent from the following. However, it should be noted that the pinion shafts 10 and 20 can be mechanically coupled to the wheel gear 90 and mechanically decoupled from each other, as shown for example and without limitation in a second embodiment of an innovative integrally geared turbomachinery system generally indicated with reference numeral 300 in Figure 3.

[0013] Firstly, it is to be clarified that Fig. 2 and Fig. 3 and their relationship with Fig. 1 should not be construed restrictively. Many other embodiments are possible without exiting from the scope of the present disclosure. Furthermore, for the sake of clarity, it is to be noted that Figures 1-3 show only a partialschematic diagram of a system: in fact, Figs. 1-3 are partial longitudinal views (i.e. longitudinal views of an upper half of the system) in which only the rotating parts of the system are shown.

[0014] With non-limiting reference to Fig. 2, the wheel gear 90 is typically driven by a drive shaft 80 which rotates around a rotation axis R. The wheel gear comprises a first portion 91 which has a first diameter and a second portion 92 which has a second diameter, the first diameter being greater than the second diameter It is to be noted that in Fig. 2 only the radius of the first portion 91 and the radius of the second portion 92 of the wheel gear 90 are shown.

[0015] The first pinion shaft 10 is configured to be mechanically coupled to the first portion 91 of the wheel gear 90 and to rotate around a first axis X (i.e. the rotation axis X of the first pinion shaft) at a first rotational speed. In particular, the first pinion shaft 10 has a pinion portion 11 which is configured to cooperate with the first portion 91 of wheel gear 90, more in particular the pinion portion 11 engages a toothing of the first portion 91 of wheel gear 90.

[0016] The second pinion shaft 20 is configured to be mechanically coupled to the second portion 92 of the wheel gear 90 and to rotate around a second axis Y (i.e. the rotation axis Y of the second pinion shaft) at a second rotational speed different from the first rotational speed. In particular, the second pinion shaft 20 has a pinion portion 22 which is configured to cooperate with the second portion 92 of wheel gear 90, more in particular the pinion portion 22 engages a toothing of the second portion 92 of wheel gear 90.

[0017] With non-limiting reference to Fig. 2, the first axis X and the second axis Y are parallel to the rotating axis R of the wheel gear 90. Additionally, according to the embodiment shown in Fig. 2, the first axis X and the second axis Y are coincident. In other words, the first pinion shaft 10 and the secondpinion shaft 20 may be defined as “coaxial”, as they rotate around two coincident axes.

[0018] Advantageously, the first pinion shaft 10 comprises a first impeller 31 mechanically coupled at a first end of the first pinion shaft 10. It is to be noted that the fist impeller 31 may be a compressor or an expander configured to respectively compress a fluid flow or expand a fluid flow, as it will better described in the following. Advantageously, the first impeller 31 is configured to rotate at the first rotational speed; even more advantageously, the first rotational speed is an optimal rotating speed of the first impeller 31 (i.e. a rotating speed adapted to maximize the efficiency of the first impeller).

[0019] Advantageously, the second pinion shaft 20 comprises a second impeller 32 mechanically coupled at a first end of the second pinion shaft 20. It is to be noted that the second impeller 32 may be a compressor or an expander configured to respectively compress a fluid flow or expand a fluid flow, as it will better described in the following. Advantageously, the second impeller 32 is configured to rotate at the second rotational speed; even more advantageously, the second rotational speed is an optimal rotating speed of the second impeller 32 (i.e. a rotating speed adapted to maximize the efficiency of the second impeller).

[0020] As already mentioned, the first impeller 31 and the second impeller 32 are configured to process a fluid flow, in particular compress or expand a fluid flow; it is to be noted that the fluid flow processed by the first impeller 31 and the fluid flow processed by the second impeller 32 may be the same fluid flow or different fluid flows. It is also to be noted that, for the purpose of the present disclosure, “different fluid flows” means fluids which may have different compositions and / or different mass flow, for example due to fluid extractions or fluid injections.

[0021] In particular, with non-limiting reference to Fig. 2, there are four possible configurations:1) the first impeller 31 and the second impeller 32 are both compressors;2) the first impeller 31 is a compressor and the second impeller 32 is an expander;3) the first impeller 31 is an expander and the second impeller 32 is a compressor;4) the first impeller 31 and the second impeller 32 are both expanders.In other words, the first impeller 31 and the second impeller 32 may be fluidly coupled or fluidly decoupled.

[0022] For example, with non-limiting reference to the first configuration in which the first impeller 31 and the second impeller 32 are both compressors, the first impeller 31 may receive a fluid flow at a compressor inlet and may be configured to compress it and to discharge a compressed fluid flow at a compressor outlet which is received from the second impeller 32 at a compressor inlet. The second impeller 32 may be configured to further compress the compressed fluid flow from the first impeller 31 and to discharge a more compressed fluid flow at a compressor outlet. In other words, according to this example, the first impeller 31 and the second impeller 32 are fluidly coupled.

[0023] According to another example, with non-limiting reference to the first configuration in which the first impeller 31 and the second impeller 32 are both compressors, the first impeller 31 may receive a first fluid flow at a compressor inlet and may be configured to compress it and to discharge a compressed first fluid flow at a compressor outlet. The second impeller 32 may be configured to receive a second fluid flow, to compress it and to discharge a compressed second fluid flow at a compressor outlet. In other words, according to this example, the first impeller 31 and the second impeller 32 are fluidly decoupled.

[0024] According to a possibility (not shown in any figure), the system 200 or 300, may further comprise a heat exchanger located downstream the first impeller 31 and upstream the second impeller 32. Advantageously, the heat exchanger is configured to remove heat from the compressed fluid flow (i.e. the heat exchanger is an “intercooler”). Alternatively, the heat exchanger is configured to provide heat to the expanded fluid flow.

[0025] With non-limiting reference to Fig. 2, the first pinion shaft 10 and the second pinion shaft 20 are mechanically coupled; in particular, a second end of the first pinion shaft 10 and a second end of the second pinion shaft 20 are interpenetrated. For example, the second end of the second pinion shaft 20 may comprise a suitable cavity configured to accommodate the second end of the first pinion shaft 10.

[0026] Advantageously, the system 200 comprises at least one bearing 45, in particular a roller bearing, which is configured to mechanically couple the first end of the first pinion shaft 10 and the first end of the second pinion shaft 20 and to allow the rotation of the first pinion shaft 10 at the first rotational speed and the rotation of the second pinion shaft 20 at the second rotational speed. In particular, the roller bearing 45 is located in the cavity of the second pinion shaft 20.

[0027] With non-limiting reference to Fig. 2, the system 200 further comprises at least one bearing 41 and 42 for each pinion shaft 10 and 20. In particular, a first bearing 41 is mechanically coupled to the first pinion shaft 10 and is configured to axially support the first pinion shaft 10 and a second bearing 42 is mechanically coupled to the second pinion shaft 20 and is configured to axially support the second pinion shaft 20. It is to be noted that also the roller bearing 45 may be further configured to axially support the first and the second pinion shafts 10 and 20.

[0028] A second embodiment 300 of an integrally geared turbomachinery system will be described in the following with the aid of Fig. 3. It is to be noted that elements in Fig. 3 which have the same reference number of elements in Fig. 2 may be identical or similar to the ones in Fig. 2 and perform the same or similar functions. However, as already mentioned before, the pinion shafts 10 and 20 of the system 300 are mechanically decoupled from each other. In particular, with non-limiting reference to Fig. 3, the first end of the first pinion shaft 10 and the first end of the second pinion shaft 20 are mechanically decoupled.

[0029] According but non limiting to the example shown in Fig. 3, the pinion portion 11 of the first pinion shaft 10 is located at the first end of the first pinion shaft 10, so that the first end of the first pinion shaft 10 is mechanically coupled to the first portion 91 of the wheel gear 90. Similarly, the pinion portion 22 of the second pinion shaft 20 is located at the first end of the second pinion shaft 20, so that the first end of the second pinion shaft 20 is mechanically coupled to the second portion 92 of the wheel gear 90. It is to be noted that the first end of the first pinion shaft 10 and the first end of the second pinion shaft 20 are spaced apart so that there is a (small) gap between them.

[0030] It is to be noted that, according to the embodiment shown in Fig. 3, the first axis X and the second axis Y are coincident. In other words, according to this embodiment, the first pinion shaft 10 and the second pinion shaft 20 may be defined as “coaxial”, as they rotate around a coincident axis. However, according to another possibility not shown in any figure, the first axis X and the second axis Y may not be coincident. In particular, depending on the diameter of the first portion 91 and the second portion 92 of the wheel gear 90, the first axis X and the second axis Y may be at different distance from the rotating axis R of the wheel gear 90; in other words, the first axis X and the second axis Y may be parallel to the rotating axis R of the wheel gear 90 butnot coincident between each other.

[0030] Advantageously, the system 300 further comprises at least two bearings 41, 42, 43 and 44 for each pinion shaft 10 and 20. In particular, a first bearing 41 and a third bearing 43 are mechanically coupled to the first pinion shaft 10 and are configured to axially support the first pinion shaft 10 and a second bearing 42 and a fourth bearing 44 are mechanically coupled to the second pinion shaft 20 and are configured to axially support the second pinion shaft 20.

[0031] As already mentioned, the Figures 2 and 3 show only (and partially) the rotary parts of the system 200 and 300. Advantageously, the system 200 and 300 further comprises a casing (not shown in any figure) configured to enclose at least the wheel gear 90, the pinion shafts 10 and 20 and the first and second impeller 31 and 32. In particular, the casing is configured to allow the flowing of fluid to and from the first impeller 31 and the second impeller 32. In other words, the casing may comprise one of more of volute, inlet guide vane unit, vaned or vaneless diffuser, flange and duct, in order to supply a fluid flow to the first impeller 31 and the second impeller 32 and to discharge a fluid flow from the first impeller 31 and the second impeller 32. As already mentioned, the fluid flow of the first impeller 31 and the second impeller 32 may be the same fluid or different fluids.

[0032] Advantageously, the system 200 and 300 comprises a plurality of couples of pinion shafts 10 and 20 which are mechanically coupled to the wheel gear 90. In particular, the first axis X of the first pinion shaft 10 and the second axis Y of the second pinion shaft 20 are parallel to the rotating axis R of the wheel gear 90 an are located at different angular positions with respect to the wheel gear 90. Advantageously, the different angular positions of the first and second axes X and Y are equally spaced around the wheel gear 90, so that the interferences between the elements of the system, in particular between impellers, are avoided.

Claims

CLAIMS1. Integrally geared turbomachinery system (200, 300) comprising a wheel gear (90) configured to rotate around a rotating axis (R) and a couple of pinion shafts (10, 20) mechanically coupled to the wheel gear (90), wherein the wheel gear (90) comprises a first portion (91) and a second portion (92), the first portion (91) of the wheel gear (90) having a diameter greater than the second portion (92) of the wheel gear, wherein a first pinion shaft (10) is configured to be mechanically coupled to the first portion (91) of the wheel gear (90) and to rotate around a first axis (X) at a first rotational speed, wherein a second pinion shaft (20) is configured to be mechanically coupled to the second portion (92) of the wheel gear (90) and to rotate around a second axis (Y) at a second rotational speed different from the first rotational speed, the first axis (X) and the second axis (Y) being coincident with each other and parallel to the rotating axis (R).

2. The integrally geared turbomachinery system (200, 300) of claim 1, further comprising a first impeller (31) and a second impeller (32), wherein the first impeller (31) is mechanically coupled at a first end of the first pinion shaft (10) and rotates at the first rotational speed, and wherein the second impeller (32) is mechanically coupled at a first end of the second pinion shaft (20) and rotates at the second rotational speed.

3. The integrally geared turbomachinery system (200, 300) of claim 2, wherein the first impeller (31) is configured to receive a fluid flow, to compress / expand it and to discharge a compressed / expanded fluid flow and the second impeller (32) is configured to receive the compressed / expanded fluid flow from the first impeller (31).

4. The integrally geared turbomachinery system (200, 300) of claim 2, wherein the first impeller (31) is configured to receive a first fluid flow, to compress / expand it and to discharge a compressed / expanded first fluid flow, and wherein the second impeller (32) is configured to receive a second fluid flow, to compress / expand it and to discharge a compressed / expanded second fluid flow.

5. The integrally geared turbomachinery system (200, 300) of claim 4, wherein the first fluid flow and the second fluid flow are the same fluid.

6. The integrally geared turbomachinery system (200, 300) of claim 4, wherein the first fluid flow and the second fluid flow are different fluids.

7. The integrally geared turbomachinery system (200, 300) of claim 3, further comprising a heat exchanger, wherein the heat exchanger is located downstream the first impeller (31) and upstream the second impeller (32), wherein the heat exchanger is configured to remove / provide heat from / to the compressed / expanded fluid flow.

8. The integrally geared turbomachinery system (300) of claim 1, wherein the first pinion shaft (10) and the second pinion shaft (20) are mechanically decoupled.

9. The integrally geared turbomachinery system (300) of claim 8, further comprising at least two bearings (41, 42, 43, 44) for each pinion shaft (10, 20), the bearings (41, 42, 43, 44) being mechanically coupled to the pinion shafts (10, 20) and being configured to axially support the pinion shafts (10, 20).

10. The integrally geared turbomachinery system (300) of claim 1, wherein the first pinion shaft (10) and the second pinion shaft (20) are mechanically coupled.

11. The integrally geared turbomachinery system (200) of claim 10, wherein a second end of the first pinion shaft (10) and a second end of the second pinion shaft (20) are interpenetrated.

12. The integrally geared turbomachinery system (200) of claim 11, further comprising at least one bearing (45), in particular a roller bearing, wherein the bearing (45) is configured to mechanically couple the second end of the first pinion shaft (10) and the first end of the second pinion shaft (20) and to allow the rotation of the first pinion shaft (10) at the first rotational speed and the rotation of the second pinion shaft (20) at the second rotational speed.

13. The integrally geared turbomachinery system (200) of claim 9, further comprising at least one bearing (41, 42) for each pinion shaft (10, 20), the bearings (41, 42) being mechanically coupled to the pinion shafts (10, 20) and being configured to axially support the pinion shafts (10, 20).

14. Integrally geared turbomachinery system (200, 300) of claim 1, comprising a plurality of couples of pinion shafts (10, 20) mechanically coupled to the wheel gear (90), wherein the first axis (X) and the second axis (Y) of each couple of pinion shafts (10, 20) are at different angular positions with respect to the wheel gear (90).

15. Integrally geared turbomachinery system (200, 300) of claim 11, wherein the different angular positions are equally spaced.

16. Integrally geared turbomachinery system (200, 300) of claim 2, further comprising a casing configured to enclose at least the wheel gear (90), the pinion shafts (10, 20) and the first and second impeller (31, 32), wherein the casing is configured to allow the flowing of fluid to and from the first impeller (31) and the second impeller (32).

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