Integrally geared compressor with axial compressor unit and method

Abstract

To provide a compact compressor with a reduced footprint and high efficiency.SOLUTION: The integrally geared compressor comprises: a bull gear 5 supported for rotation in a casing 3; and a plurality of pinion shafts 15, 23 comprising pinions 21, 29, which meshes with the bull gear 5. A first pinion shaft 15 has a first end drivingly coupled to an axial compressor unit 31 comprising a gas inlet 43, a gas outlet 45 and an axial compression wheel 47. A second pinion shaft 23 is drivingly coupled to a centrifugal compressor arrangement.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to improvements in gas compressors. In particular, embodiments disclosed herein relate to integrally geared compressors. [Background technology]

[0002] Integral geared compressors are often used to process air, carbon dioxide, or steam. One advantage of integrally geared compressors is that they allow for multiple intercooling between compressor stages, as well as the ability to drive successively arranged compressor stages at different rotational speeds.

[0003] GB 1048966 discloses a compressor arrangement including an electric motor driving a main gear that meshes with a first pinion on a first end of a first compressor shaft and a second pinion on a first end of a second compressor shaft, the first compressor being drivingly coupled to the second end of the first compressor shaft, and the second compressor being drivingly coupled to the second end of the second compressor shaft.

[0004] U.S. Patent Application Publication No. 2016 / 0230771 discloses a bull gear compressor including a bull gear rotatably driven by a steam turbine. The steam turbine is drivingly coupled to a drive shaft coupled to the bull gear via a pinion keyed to the drive shaft. A main compressor is directly driven by the drive shaft. Further, a compressor unit is drivingly coupled to the bull gear via a driven shaft disposed around the bull gear.

[0005] Current technology integrally geared compressors still suffer from several limitations, particularly limited inlet volumetric flow rates. To improve inlet flow rates, larger impellers have been developed, but this requires a reduction in rotational speed. As an alternative, double-flow machines have been envisioned, in which the first compression stage is split into two separate impellers that operate in parallel, allowing a larger volumetric inlet flow to be processed by the same machine. Double-flow integrally geared compressors are cumbersome, particularly in terms of their footprint. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a need for improved designs of integrally geared compressors to remove or mitigate their limitations while retaining the advantages of these machines.

[0007] In accordance with one aspect, disclosed herein is a novel construction for an integrally geared compressor that includes a bull gear supported for rotation within a gear casing and a plurality of pinion shafts also supported for rotation within the gear casing, each pinion shaft including a respective pinion that meshes with the bull gear.

[0008] In accordance with a novel arrangement disclosed herein, a first pinion shaft has a first end drivingly coupled to a first axial compressor unit having a gas inlet, a gas outlet, and an axial compression wheel, the axial compression wheel being cantilevered on the first end of the first pinion shaft. A second compressor unit is cantilevered on the second end of the first pinion shaft. The gas outlet of the first axial compressor unit is fluidly coupled to the gas inlet of the second compressor unit. The second pinion shaft is drivingly coupled to a compressor arrangement including an additional compressor unit cantilevered on the first end of the second pinion shaft. The additional compressor unit is a centrifugal compressor unit.

[0009] In some embodiments, the compressor may include two or more axial compressor units, for example, two axial compressor units disposed on opposite ends of the first pinion shaft.

[0010] Further embodiments and advantageous features of the integrally geared compressor are outlined below and set forth in the accompanying claims. [Brief explanation of the drawings]

[0011] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] FIG. 1 is a cross-sectional view of an integrally geared compressor according to the present disclosure. [Figure 2] FIG. 2 is a flow chart summarizing a method of operating an integrated gear compressor according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] A novel compressor is disclosed for improving the inlet flow rate of an integrally geared compressor without increasing the overall footprint of the machine. The compressor includes a bull gear that drives and rotates two or more pinion shafts disposed around the bull gear. Each pinion shaft includes a pinion that meshes with the bull gear. The pinions may have different diameters and different numbers of teeth so that the pinion shafts rotate at different rotational speeds. A compressor driver is drivingly coupled to a central shaft that rotates the bull gear. Rotational motion is transmitted from the bull gear to the mating pinions at different transmission ratios. The compressor stages are drivingly coupled to the pinion shafts. The most upstream compressor stage is an axial compressor stage drivingly coupled to a first one of the pinion shafts. Second and subsequent compressor stages may be centrifugal compressor stages arranged in sequence to further compress the gas flow delivered by the axial compressor stage. To remove heat from the partially compressed process gas and improve the overall efficiency of the multi-stage integrally geared compressor, an intercooler may be provided between one or more pairs of sequentially arranged compressor stages.

[0013] The most upstream axial compressor stage is adapted to handle a larger inlet flow rate than a typical centrifugal compressor stage, thus resulting in a compact machine adapted to handle large volumes of inlet gas.

[0014] Referring now to the drawings, FIG. 1 shows a top view of an integrally geared compressor 1 having a compressor casing 3 cut along a horizontal plane to show the components housed within the casing 3.

[0015] A bull gear 5 is rotatably supported within the casing 3. The bull gear 5 is drivingly connected to an input shaft 7, which may be rotatably driven by a drive unit 9, for example an electric motor or any other suitable drive unit. The bull gear 5 is supported by bearings 11, 13 for rotation within the casing 3 about a main axis of rotation AA.

[0016] The bull gear 5 can rotate at the speed of the drive unit 9 or at a different speed if a speed manipulation device, such as a gearbox 8, is arranged along the shaft line between the drive unit 9 and the input shaft 7.

[0017] The compressor 1 further includes a plurality of pinion shafts. Two pinion shafts are shown in Figure 1. Nevertheless, it should be understood that a greater number of pinion shafts may be provided in the same compressor 1.

[0018] The first pinion shaft 15 is rotatably supported about the rotation axis BB by bearings 17 and 19. A first pinion 21 is keyed to or integrally formed with the first pinion shaft 15. The first pinion 21 meshes with the bull gear 5. Therefore, the first pinion shaft 15 is rotationally driven by the drive unit 9 at a rotational speed determined by the transmission ratio between the bull gear 5 and the first pinion 21.

[0019] The second pinion shaft 23 is rotatably supported about a rotation axis CC by bearings 25, 27. The second pinion 29 is keyed to or integrally formed with the second pinion shaft 23. The second pinion 29 meshes with the bull gear 5. Thus, the second pinion shaft 23 rotates at a rotational speed given by the transmission ratio between the bull gear 5 and the second pinion 29. In some embodiments, the rotational speed of the second pinion shaft 23 may be higher than the rotational speed of the first pinion shaft 15.

[0020] Generally, the integrally geared compressor 1 includes a first, most upstream axial compressor unit driven by a first pinion shaft 15 at a first rotational speed, and a centrifugal compressor arrangement driven by a second pinion shaft at a second rotational speed, the first rotational speed and the second rotational speed being higher than the rotational speed of the bull gear 5.

[0021] A centrifugal compressor arrangement can include one or more centrifugal compressor units. As mentioned above, in some embodiments not shown, a third or further pinion shaft may be provided to drive additional centrifugal compressor units belonging to the centrifugal compressor arrangement. As will be explained in detail below, in the embodiment of Figure 1, a centrifugal compressor unit is also provided on the first pinion shaft 15 opposite the axial compressor unit 31 so as to rotate at the same rotational speed as the axial compressor unit 31.

[0022] More specifically, in the embodiment of Figure 1, the compressor 1 has four compressor units. As already mentioned, the first, most upstream compressor unit 31 is disposed at a first end of the first pinion shaft 15. The second compressor unit 33 is disposed at a second end of the first pinion shaft 15. Additional third and fourth compressor units 35, 37, which form part of the centrifugal compressor arrangement, are driven by the second pinion shaft 23. Specifically, the third compressor unit 35 is disposed at a first end of the second pinion shaft 23, and the fourth compressor unit 37 is disposed at a second end of the second pinion shaft 23.

[0023] The first, second, third and fourth compressor units are arranged in sequence starting from the most upstream compressor unit 31 to the most downstream compressor unit 37, and the process gas is first compressed in the axial compressor unit 31 having a higher volumetric flow rate, and then compressed in stages in the remaining centrifugal compressor units 33, 35 and 37 in sequence.

[0024] An intercooler may be provided along the connecting line connecting each pair of consecutively arranged compressor units 31-37. By way of example, intercooler 39 is shown in FIG. 1 along connecting line 41 fluidly coupling first compressor unit 31 to second compressor unit 33.

[0025] The first compressor unit 31 includes a gas inlet 43, a gas outlet 45, and an axial compression wheel 47 therebetween. In the embodiment of FIG. 1 , the axial compressor unit 31 includes two axial compression stages, each including a circular array of rotating blades 49 keyed to the axial compression wheel 47 and a respective set of fixed blades or vanes 51 attached to a casing 52 of the axial compressor unit 31. It should be understood that the number of axial compression stages shown is merely exemplary, and that the axial compressor unit 31 can include a different number of axial compression stages, e.g., three or more. In some embodiments, the fixed blades 51 can have variable inclination. The angular position of the fixed blades 51 can be adapted to the operating conditions of the compressor 1 by a suitable control device, indicated generally by the reference numeral 53. The control device 53 is adapted to pivot each fixed blade 51 about a radial axis, i.e., an axis perpendicular to the rotation axis BB of the axial compressor unit 31.

[0026] In the embodiment of FIG. 1, the axial compression wheel 47 is cantilevered onto the first end of the first pinion shaft 15 .

[0027] In the embodiment of FIG. 1, the gas inlet 43 is an axial inlet and the gas outlet 45 is a radial outlet. The partially compressed gas flow from the axial wheel is diverted radially toward the radial outlet. The scroll 55 collects the partially compressed gas from the axial compression wheel 47 and directs the partially compressed gas flow through a diffuser 57 toward the gas outlet 45. In some embodiments, as shown in FIG. 1, the diffuser 57 is a vaned diffuser 57 to improve the efficiency of the first compressor unit 31.

[0028] Each compressor unit 33, 35 and 37 includes one or more centrifugal compressor stages. In the embodiment of Figure 1, each centrifugal compressor unit 33, 35, 37 includes a single centrifugal compressor stage with a single centrifugal compressor impeller. The possibility of having multiple centrifugal compressor stages in one, some or all of the compressor units 33, 35, 37 is not excluded.

[0029] 1, the second, third, and fourth compressor units 33, 35, 37 are similar to one another. Specifically, the second compressor unit 33 is a centrifugal compressor unit including a single centrifugal impeller 61 cantilevered to the second end of the first pinion shaft 15 and rotatably disposed within a casing 63 having a gas inlet 65 and a gas outlet 67. A vaned diffuser 69 may be disposed between the centrifugal impeller 61 and the gas outlet 67. In other embodiments, the diffuser 69 may be a vaneless diffuser.

[0030] Similarly, the third compressor unit 35 is a centrifugal compressor unit cantilevered onto a first end of the second pinion shaft 23 and includes a centrifugal impeller 61 rotatably disposed within a casing 73 having a gas inlet 75 and a gas outlet 77. A vaned or vaneless diffuser 79 may be disposed between the centrifugal impeller 61 and the gas outlet 77. The gas inlet 75 is fluidly coupled to the gas outlet 67 of the second compressor unit 33 via a connecting line (not shown) along which an intercooler may be provided, similar to the intercooler 39 along line 41.

[0031] The fourth compressor unit 37 is a centrifugal compressor unit cantilevered on the second end of the second pinion shaft 23 and includes a centrifugal impeller 81 rotatably disposed within a casing 83 having a gas inlet 85 and a gas outlet 87. A vaned or vaneless diffuser 89 may be disposed between the centrifugal impeller 81 and the gas outlet 87. The gas inlet 85 is fluidly coupled to the gas outlet 77 of the third compressor unit 35. An intercooler may be provided along a connecting line (not shown) between the third compressor unit 35 and the fourth compressor unit 37.

[0032] The compressor 1 is therefore configured to process a gas stream that first enters the first axial compressor unit 31 and is then further compressed in sequence in the second, third and fourth centrifugal compressor units 33, 35 and 37. The axial compression wheel 47 and centrifugal compressor impeller 61 of compressor unit 33 rotate at the same rotational speed. The impellers 71 and 81 of the third and fourth compressor units 35 and 37 rotate at the same rotational speed, which is preferably different from the rotational speed of the axial compression wheel 47 and centrifugal impeller 61.

[0033] In some embodiments, the rotational speed of the second pinion shaft 23, centrifugal impeller 71, and centrifugal impeller 81 is higher than the rotational speed of the first pinion shaft 15 and the axial wheel 47 and centrifugal impeller 61 keyed thereto. The ratio between the rotational speed of the first pinion shaft 15 and the rotational speed of the second pinion shaft 23 is given by the ratio between the number of teeth of the pinion 21 and the number of teeth of the pinion 29. By designing the bull gear 5 and the pinions 21, 29 with the appropriate number of teeth, the optimum rotational speed ratio for a given application of the compressor 1 can be set.

[0034] 2 summarizes the method of operation of the compressor 1. The inlet gas stream (step 100) is first compressed in the axial compressor unit 31 (step 101) and then further compressed in the second centrifugal compressor unit 33 (step 103). An intercooling step is also indicated at 102. The partially compressed gas from the second centrifugal compressor unit 33 is delivered to the third centrifugal compressor unit 35 for further compression (step 105) and finally to the fourth centrifugal compressor unit 37 for final compression to a delivery pressure (step 107). Intercooling steps 104 and 106 can be foreseen between the compression steps in the centrifugal compressor unit 33 and the centrifugal compressor unit 35 and / or between the compression steps in the centrifugal compressor unit 35 and the centrifugal compressor unit 37.

[0035] The axial compressor stage 31 can include a high Mach axial wheel to increase the maximum flow rate within the first compression unit without resorting to a double-flow architecture and excessively large impeller size, thus resulting in a compact compressor with a small footprint and high efficiency.

[0036] The presently disclosed embodiment is by way of example. In other embodiments not shown, the integrally geared compressor may include two or more axial compressor units. For example, the first pinion shaft may be drivingly coupled to axial compressor units at both its first and second ends.

[0037] Exemplary embodiments are disclosed above and shown in the accompanying drawings. Those skilled in the art will understand that various modifications, omissions, and additions may be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the claims that follow.

Claims

1. An integral gear compressor, a bull gear supported for rotation within a gear casing; a plurality of pinion shafts supported for rotation within the gear casing, each pinion shaft having a respective pinion meshing with the bull gear; a first pinion shaft of the plurality of pinion shafts having a first end drivingly coupled to a first axial compressor unit having a gas inlet, a gas outlet, and an axial compression wheel, the axial compression wheel being cantilevered at the first end of the first pinion shaft of the plurality of pinion shafts; a second compressor unit being cantilevered at a second end of the first pinion shaft of the plurality of pinion shafts, the gas outlet of the first axial compressor unit being fluidly coupled to a gas inlet of the second compressor unit; and a second pinion shaft of the plurality of pinion shafts drivingly coupled to a centrifugal compressor arrangement comprising a further compressor unit cantilevered at the first end of the second pinion shaft of the plurality of pinion shafts, the further compressor unit being a centrifugal compressor unit.

2. 2. The integrally geared compressor of claim 1, wherein the gas inlet of the first axial compressor unit is an axial gas inlet and the gas outlet of the first axial compressor unit is a radial gas outlet.

3. The integrally geared compressor of claim 2 , wherein the radial gas outlet of the first axial compressor unit comprises a vaned diffuser.

4. The integral gear compressor according to any one of claims 1 to 3, wherein the first axial compressor unit is a multi-stage axial compressor unit.

5. The integral gear compressor according to any one of claims 1 to 4, wherein the second compressor unit is an axial compressor unit.

6. The integrally geared compressor of any one of claims 1 to 4, wherein the second compressor unit comprises a first centrifugal compressor stage.

7. 7. The integrally geared compressor of claim 6, wherein a gas outlet of the first centrifugal compressor stage is fluidly coupled to a gas inlet of a second centrifugal compressor stage of the further compressor unit.

8. 8. The integrally geared compressor according to claim 1, wherein the second pinion shaft of the plurality of pinion shafts has a second end drivingly connected to a third centrifugal compressor stage cantilevered at the second end of the second pinion shaft of the plurality of pinion shafts.

9. 9. The integrally geared compressor of claim 7 or 8, wherein a gas inlet of the third centrifugal compressor stage is fluidly coupled to a gas outlet of the second centrifugal compressor stage.

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