Turbomachinery and multi-stage rotors

Abstract

This turbomachine comprises a casing and a multistage rotor supported by the casing. The multistage rotor includes a rotor shaft that has a stepped surface and that is constituted of one member, a plurality of impellers that are fitted onto the rotor shaft and lined up in the axial direction of the rotor shaft from the stepped surface, and a lock nut that is fitted onto the rotor shaft. The plurality of impellers are sandwiched between the stepped surface and the lock nut.

Description

Technical Field

[0001] The present disclosure relates to a multistage rotor of a turbomachine such as a compressor.

Background Art

[0002] A turbomachine continuously performs energy conversion between fluid energy and mechanical energy via a rotating impeller. Some turbomachines include a multistage rotor having a plurality of stages of impellers. Patent Document 1 discloses this type of turbomachine.

[0003] The turbomachine of Patent Document 1 is a centrifugal compressor, and includes a multistage rotor having a tie bolt, short rotor shafts (i.e., stub shafts) assembled to both ends of the tie bolt, respectively, and a plurality of impellers supported by the tie bolt and arranged in the axial direction. Adjacent impellers are interconnected by mechanical couplings and fastened by the axial force of the tie bolt.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] In the multi-stage rotor described in Patent Document 1, tie bolts are assembled to a pair of rotor shafts, which may cause misalignment between the rotor shafts and the tie bolts. Such misalignment makes it difficult to eliminate the imbalance of the multi-stage rotor during the balancing process. Furthermore, increasing the compression ratio of the rotor can be achieved by increasing the length of the rotor shafts and the rotational speed. However, this increases the risk that the eigenvalues ​​of the tie bolts will interfere with the operating speed. To detune the eigenvalues ​​of the tie bolts from the operating speed, tie bolts tend to be made larger in diameter. When tie bolts are made larger in diameter, the impact of misalignment between the rotor shafts and tie bolts on the imbalance of the multi-stage rotor becomes greater.

[0006] This disclosure has been made in view of the above circumstances, and its purpose is to provide a multi-stage rotor capable of preventing unbalance caused by misalignment between the rotor shaft and the tie bolt, and a turbomachine equipped with said multi-stage rotor. [Means for solving the problem]

[0007] To solve the above problems, a multi-stage rotor according to one aspect of this disclosure is: A rotor shaft having a stepped surface and composed of a single component, A plurality of impellers are fitted onto the rotor shaft and are arranged in the axial direction of the rotor shaft from the stepped surface, The rotor shaft is fitted with a lock nut, The plurality of impellers are sandwiched between the stepped surface and the lock nut, under pressure from the axial force of the rotor shaft.

[0008] A turbomachinery according to one aspect of the present disclosure comprises a casing and a multi-stage rotor supported by the casing.

[0009] Furthermore, a method for manufacturing a multi-stage rotor according to one aspect of this disclosure is: A rotor shaft having a stepped surface and composed of a single component, onto which multiple impellers are fitted, and This includes fitting a lock nut onto the rotor shaft and sandwiching the plurality of impellers between the stepped surface and the lock nut while being pressed by the axial force of the rotor shaft. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a multi-stage rotor capable of preventing imbalance caused by misalignment between the tie bolt and the rotor shaft, and a turbomachine equipped with the multi-stage rotor. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic cross-sectional view of a turbomachinery according to one aspect of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view of a multi-stage rotor. [Figure 3] Figure 3 is a schematic cross-sectional view of a multi-stage rotor with a straight configuration. [Figure 4] Figure 4 is a cross-sectional view of a multi-stage rotor illustrating the internal passages. [Figure 5] Figure 5 is a cross-sectional view of a multi-stage rotor illustrating a modified example of the internal passage. [Figure 6] Figure 6 illustrates a method for manufacturing a multi-stage rotor. [Figure 7] Figure 7 shows a balance piston and lock nut according to Modification 1. [Figure 8] Figure 8 shows a balance piston and lock nut according to modified example 2. [Figure 9] Figure 9 is a schematic cross-sectional view of a multi-stage rotor with impellers positioned on both sides via a second section. [Figure 10] Figure 10 is a schematic cross-sectional view of a modified multi-stage rotor. [Modes for carrying out the invention]

[0012] FIG. 1 is a schematic cross-sectional view of a turbomachine 1 according to an aspect of the present disclosure, in which the upper half relative to the rotor axis A of the turbomachine 1 is shown. FIG. 1 shows a centrifugal compressor including a multistage rotor 2 as one embodiment of the turbomachine 1. The multistage rotor 2 is a rotor that stepwise compresses fluid by multistage impellers 4. Further, the centrifugal compressor allows fluid to pass through in the radial direction of the rotating impeller 4, and compresses the fluid by centrifugal force generated at that time. However, the multistage rotor 2 according to the present disclosure is not limited to centrifugal compressors, and can be widely applied to the turbomachine 1.

[0013] The turbomachine 1 includes a casing 12, the multistage rotor 2 accommodated in the casing 12, and a drive device that rotationally drives the multistage rotor 2.

[0014] FIG. 2 is a schematic cross-sectional view of the multistage rotor 2. As shown in FIGS. 1 and 2, the multistage rotor 2 is a rotating body centered on the rotor axis A. The multistage rotor 2 includes a rotor shaft 3 extending parallel to the axial direction X about the rotor axis A, and a plurality of impellers 4 arranged along the axial direction X at a substantially central portion of the rotor shaft 3 in the axial direction X. The plurality of impellers 4 stacked in the axial direction X are also referred to as an impeller stack 40, and the multistage rotor 2 is also referred to as a stacked rotor.

[0015] The rotor shaft 3 is a stepped shaft having a stepped surface 36. The rotor shaft 3 includes a first section 31 arranged at a central portion in the axial direction X, a second section 32 arranged adjacent to the first section 31, a pair of third sections 33 sandwiching the first section 31 and the second section 32 from both sides in the axial direction X, and a pair of end sections 34 arranged at both ends in the axial direction X. The rotor shaft 3 is a rigid body made of a single member, and has no joints on the rotor shaft 3.

[0016] The first section 31 of the rotor shaft 3 has a first shaft diameter D1 smaller than the impeller bore diameter d1 of the impeller 4, and the second section 32 has a second shaft diameter D2 larger than the first shaft diameter D1 and the impeller bore diameter d1 of the impeller 4. Due to such a difference in shaft diameters, a stepped surface 36 facing the axial direction X exists at the boundary between the second section 32 and the first section 31. The fourth shaft diameter D4 of the end section 34 of the rotor shaft 3 is smaller than the first shaft diameter D1. The third shaft diameter D3 of the third section 33 of the rotor shaft 3 is larger than the fourth shaft diameter D4 of the end section 34 and smaller than the impeller bore diameter d1 of the impeller 4. The third shaft diameter D3 of the third section 33 may be larger than the first shaft diameter D1 as long as it is smaller than the impeller bore diameter d1 of the impeller 4. In this way, in the rotor shaft 3, the impeller 4 can be moved from the end section 34 through the third section 33 to the first section 31.

[0017] The first section 31 of the rotor shaft 3 is inserted through the impeller stack 40. Each impeller 4 has a known structure, and includes, for example, an impeller hub through which the rotor shaft 3 is inserted, a disk centered on the impeller hub, a plurality of blades provided on the disk, and a shroud attached to the tips of the blades. In the impeller 4, a flow path through which the fluid to be compressed passes is formed by the disk, the blades, and the shroud. The impeller 4 is of a closed type, but may be of an open type in which the shroud is omitted. Both end faces of the impeller hub of the impeller 4 in the axial direction X are toothed flanges formed with circumferential teeth. Adjacent impellers 4 in the axial direction X are coupled so as to be able to transmit power by a mechanical coupling in which the toothed flanges mesh with each other. The mechanical coupling may be a Curvic coupling or a Hirth coupling.

[0018] Increasing the amount of work that the turbomachinery 1 does to the fluid is accompanied by increasing the peripheral speed of the impeller 4. As the peripheral speed of the impeller 4 increases, the centrifugal stress acting on the impeller 4 increases. To withstand the increased centrifugal stress, the impeller 4 is preferably made of aluminum alloy, and the rotor shaft 3 is preferably made of steel. The specific strength (specific strength = tensile strength / density) of aluminum alloy is about 3 to 4 times that of steel. Therefore, an aluminum alloy impeller 4 experiences reduced centrifugal stress compared to an impeller 4 made of steel, and possesses the strength to withstand high peripheral speeds.

[0019] The impeller stack 40 may include at least one balance piston 57. The balance piston 57 autonomously adjusts the axial thrust of the rotating multi-stage rotor 2. The impeller stack 40 according to this embodiment has a balance piston 57 positioned midway along the axial direction X, and has a so-called back-to-back arrangement in which the impeller 4 positioned on the non-load side and the impeller 4 positioned on the load side are oriented differently via the balance piston 57. However, the arrangement of the impeller 4 in the impeller stack 40 is not limited to this, and as shown in Figure 3, it may have a straight-type arrangement in which all impeller 4 are aligned in the same direction. The balance piston 57 is fitted onto the rotor shaft 3 in the same way as the impeller 4. Both end faces of the balance piston 57 in the axial direction X are toothed flanges with teeth formed in the circumferential direction, and adjacent impeller 4 and balance piston 57 in the axial direction X are coupled in a way that allows power to be transmitted by a mechanical coupling in which the toothed flanges mesh with each other.

[0020] Returning to Figure 2, the impeller 4 located closest to the second section 32 in the impeller stack 40 is conveniently referred to as the "leading impeller 4L". In this embodiment, the leading impeller 4L is the first-stage impeller 4A that compresses the fluid first among the multiple impellers 4, but the leading impeller 4L is not limited to the first-stage impeller 4A. The leading impeller 4L is in contact with the stepped surface 36 of the rotor shaft 3. The surface of the leading impeller 4L facing the stepped surface 36 is flat and does not have teeth formed on it, so the leading impeller 4L and the stepped surface 36 are in flat contact. The leading impeller 4L and the stepped surface 36 are coupled by friction, and power can be transmitted from the rotor shaft 3 to the leading impeller 4L. To provide redundancy in the power transmission from the rotor shaft 3 to the leading impeller 4L, and to ensure alignment between the rotor shaft 3 and the leading impeller 4L, the leading impeller 4L may be restricted from relative rotation and radial movement with respect to the rotor shaft 3 by interference fit, spline fitting, or meshing.

[0021] In this embodiment, the leading impeller 4L is in contact with the stepped surface 36 of the rotor shaft 3, but at least one cylindrical body may be positioned between the leading impeller 4L and the stepped surface 36 in the axial direction X. In this case, as shown in the modified example in Figure 10, a cylindrical body 47 passed through the first section 31 of the rotor shaft 3 is positioned between the leading impeller 4L and the stepped surface 36, and the stepped surface 36 and the cylindrical body 47 are in contact, and the cylindrical body 47 and the leading impeller 4L are in contact. The surface of the cylindrical body 47 facing the stepped surface 36 is flat and does not have teeth formed on it, and the cylindrical body 47 and the stepped surface 36 are in contact on a flat surface. The cylindrical body 47 and the stepped surface 36 are coupled by friction, and power can be transmitted from the rotor shaft 3 to the cylindrical body 47. To provide redundancy in power transmission from the rotor shaft 3 to the cylindrical body 47, and to ensure alignment between the rotor shaft 3 and the cylindrical body 47, the cylindrical body 47 may be restricted from relative rotation and radial movement with respect to the rotor shaft 3 by interference fit, spline fitting, or meshing. The surface of the cylindrical body 47 facing the leading impeller 4L and the surface of the leading impeller 4L facing the cylindrical body 47 are toothed flanges with circumferential teeth, and the cylindrical body 47 and the leading impeller 4L are connected in a way that allows power transmission by a mechanical coupling in which the toothed flanges mesh with each other.

[0022] Returning to Figure 2, the impeller 4 located furthest from the second section 32 in the impeller stack 40 is conveniently referred to as the "tail impeller 4T". In this embodiment, the tail impeller 4T is not the final stage impeller 4E that compresses the fluid last among the multiple impellers 4, but rather the fourth stage impeller. The tail impeller 4T is in contact with a balance piston 56 fitted to the rotor shaft 3. The balance piston 56 may be fitted to the third section 33 or the first section 31 of the rotor shaft 3. The tail impeller 4T and the balance piston 56 are connected by a mechanical coupling through meshing.

[0023] A lock nut 6 is screwed onto the third section 33 of the rotor shaft 3. The lock nut 6 is in contact with the balance piston 56. The impeller stack 40 and the balance piston 56 are positioned between the stepped surface 36 of the rotor shaft 3 and the lock nut 6 in the axial direction X. Due to the axial force of the rotor shaft 3, the impeller stack 40 and the balance piston 56 are pressed and sandwiched between the stepped surface 36 and the lock nut 6 in the axial direction. As a result, the stepped surface 36 and the leading impeller 4L, adjacent impellers 4 to each other, and the tail impeller 4T and the balance piston 56 are held in close contact in the axial direction X. In addition, the lock nut 6 aligns the rotor shaft 3 and the impeller stack 40 so that the rotor axis A of the rotor shaft 3 coincides with the axis of the impeller stack 40.

[0024] As shown in Figure 1, dry gas seals 54 and 55 are positioned around the third section 33 of the rotor shaft 3 to seal the space between the casing 12 and the rotor shaft 3. The dry gas seals 54 and 55 prevent leakage of the working fluid, which is compressed and pressurized by the multi-stage rotor 2, to the outside. The dry gas seals 54 and 55 are supplied with sealing gas from the outside. The end section 34 of the rotor shaft 3 is rotatably supported by the casing 12 via journal bearings 51 and 52. The end section 34 of the rotor shaft 3 is also supported by the casing 12 via a thrust bearing 53.

[0025] The journal bearings 51 and 52 supporting the end section 34 of the rotor shaft 3 are coated with white metal bearing material on their bearing surfaces. When the impeller 4 increases in peripheral speed, the sliding speed between the end section 34 of the rotor shaft 3 and the journal bearings 52 increases, causing the temperature of the journal bearings 51 and 52 to rise. The bearing coating has a permissible temperature range, and the fourth shaft diameter D4 of the end section 34 of the rotor shaft 3 must be designed so that the temperature of the journal bearings 51 and 52 remains within that permissible temperature range. In the turbomachinery 1, once the peripheral speed of the impeller 4 is determined, the amount of work done on each stage of the impeller 4 is determined. The peripheral speed of the impeller 4 is determined by the product of the diameter of the impeller 4 and the rotational speed (revolutions per minute). The impeller hub diameter d2 (see Figure 2) is designed based on the structural strength requirements for the peripheral speed of the impeller 4. Furthermore, the fourth shaft diameter D4 of the end section 34 of the rotor shaft 3 is designed based on the rotational speed of the impeller 4. In the multi-stage rotor 2, the ratio of the impeller hub diameter d2 to the fourth shaft diameter D4 (= impeller hub diameter d2 / fourth shaft diameter D4) is preferably 2.0 or more and 2.8 or less, and more preferably 2.2 or more and 2.6 or less. By having such a ratio of impeller hub diameter d2 to the fourth shaft diameter D4 in the multi-stage rotor 2, even if the impeller 4 is increased to a high peripheral speed to obtain the amount of work required to compress a gas with a low molecular weight and high gas constant (for example, hydrogen), it is possible to keep the temperatures of the journal bearings 51 and 52 below the allowable temperature.

[0026] Figure 1 shows a portion of the casing 12. The casing 12 has connecting passages 21 that connect adjacent impellers 4. The connecting passages 21 are connected to the passages of the impellers 4. The fluid compressed by a certain stage of the impeller 4 is discharged into the connecting passages 21 and flows through the connecting passages 21 into the passage of the next stage of the impeller 4. The casing 12 is provided with an intake port 22 for introducing the fluid to be compressed into the first stage impeller 4 and an outlet port 23 for sending the fluid compressed by the final stage impeller 4 to the outside. Furthermore, the casing 12 is provided with an intermediate discharge port 27 for temporarily taking the compressed fluid from the intermediate stages outside the machine and an intermediate intake port 28 for returning it to the machine. As described above, in the turbomachinery 1 according to this embodiment, a series of compression passages W are formed by the casing 12 and the impellers 4, through which fluid drawn in from the intake port 22 is gradually compressed through multiple stages of impellers 4, temporarily removed from the machine through the intermediate discharge port 27, returned to the machine through the intermediate intake port 28, further gradually compressed through multiple impellers 4, and then discharged to the outside through the discharge port 23. However, the fluid flow path and the number of stages of the impellers 4 in the turbomachinery 1 are merely illustrative examples.

[0027] A small gap is provided between the inner surface of the impeller 4 and the outer surface of the rotor shaft 3, and this gap forms an internal passage 7. Figure 4 is a cross-sectional view of the multi-stage rotor 2 illustrating the internal passage 7. In Figure 4 and Figure 5, which will be described later, the fluid flow through the connecting passage 74, the internal passage 7, and the connecting passage 73 is shown by dashed lines, and the fluid flow through the compression passage W from the intake port 22 to the discharge port 23 is shown by a dashed line. As shown in Figure 4, an internal passage 7 is provided between the impeller stack 40 and the rotor shaft 3 through which the fluid flows in the axial direction X. The internal passage 7 is connected to the extraction position E of the compression passage W by the connecting passage 74. The internal passage 7 is also connected to the return position R upstream of the extraction position E of the compression passage W by the connecting passage 73. A portion of the fluid flowing through the extraction position E of the compression passage W is introduced into the internal passage 7 through the connecting passage 74, flows axially through the internal passage 7, and then returns to the return position R of the compression passage W through the connecting passage 73. In this way, by having a portion of the fluid circulate through the compression passage W and the internal passage 7, the pressure in the radial gap between the rotor shaft 3 and the impeller stack 40 is stabilized, preventing the accumulation of impurities in the gap and mitigating the temperature difference between the impeller stack 40 and the rotor shaft 3. The inner circumferential surface of the impeller 4 is coated with a heat-shielding coating to suppress heat transfer from the fluid passing through the internal passage 7 to the internal passage 7. Fins may be formed on the outer circumferential surface of the rotor shaft 3 that is exposed to the internal passage 7 to increase the heat transfer area.

[0028] In this embodiment, the extraction position E of the compression passage W is near the inlet of the tail impeller 4T. The connecting passage 74 passes radially through the balance piston 56 and through the rotor shaft 3 to the internal passage 7. However, the connecting passage 74 may also pass through the gap in the meshing surface of the mechanical coupling between the tail impeller 4T and the balance piston 56.

[0029] In this embodiment, the return position R of the compression passage W is near the inlet of the leading impeller 4L, which is also the first-stage impeller 4A. The connecting passage 73 runs from the internal passage 7 through the inside of the rotor shaft 3 to the compression passage W. Specifically, a passage connecting the internal passage 7 and the return position R of the compression passage W is formed inside the second section 32 of the rotor shaft 3, which is in contact with the leading impeller 4L, and this passage is used as the connecting passage 73. By having the connecting passage 73 run through the inside of the rotor shaft 3 in this way, the degree of freedom of the position of the return position R, which is the outlet of the connecting passage 73, is increased, and the return position R can be positioned at a location upstream from the inlet of the leading impeller 4L. If the return position R is located upstream from the inlet of the first-stage impeller 4A, the influence of the returned fluid on the main flow of the compression passage W can be suppressed.

[0030] As shown in Figure 5, the connecting passage 73 may pass between the rotor shaft 3 and the first stage impeller 4A. The planar stepped surface 36 of the rotor shaft 3 and the planar contact surface 48 of the leading impeller 4L are in contact in the axial direction X. A groove is formed in at least one of the stepped surface 36 and the contact surface 48, and this groove is used as part of the connecting passage 73. The connecting passage 73 may utilize a groove formed in at least one of the outer circumferential surface of the rotor shaft 3 and the inner circumferential surface of the leading impeller 4L, or the radial gap between the outer circumferential surface of the rotor shaft 3 and the inner circumferential surface of the leading impeller 4L.

[0031] Furthermore, the return position R of the compression passage W may be located downstream of the inlet of the first-stage impeller 4A. In this case, the connecting passage 73 passes through the gap in the meshing surface of the mechanical coupling between the first-stage impeller 4A and the adjacent impeller 4.

[0032] Here, we will explain how to assemble the impeller 4 to the rotor shaft 3 in the multi-stage rotor 2 with the above configuration.

[0033] First, multiple impellers 4 are fitted onto the rotor shaft 3 in order from the leading impeller 4L to the trailing impeller 4T, starting from the load-side end. In this embodiment, the second section 32 of the rotor shaft 3 is positioned on the non-load side of the center in the axial direction X of the rotor shaft 3, and the multiple impellers 4, balance pistons 56, 57, and lock nuts 6 are all inserted from the load-side end of the rotor shaft 3 toward the stepped surface 36. However, these elements may also be inserted from the non-load-side end of the rotor shaft 3 depending on the arrangement of the second section 32.

[0034] The leading impeller 4L abuts against the stepped surface 36 of the rotor shaft 3. Here, the leading impeller 4L may be precisely fitted into the first section 31 of the rotor shaft 3 to align the rotor shaft 3 with the leading impeller 4L. In addition, balance pistons 57 are positioned between the multiple impellers 4. The balance pistons 57 are also externally fitted onto the rotor shaft 3, similar to the impellers 4.

[0035] Next, the rotor shaft 3 is cooled, and as shown in the upper part of Figure 6, the balance piston 56 is fitted onto the cooled and contracted rotor shaft 3. Here, the inner surface of the balance piston 56 and the outer surface of the cooled and contracted rotor shaft 3 are spaced apart in the radial direction. Subsequently, as shown in the middle part of Figure 6, an axial force in the tensile direction is applied to the rotor shaft 3 by the tensioner, and the lock nut 6 is fitted onto the cooled and contracted rotor shaft 3. As shown in the lower part of Figure 6, when the axial force in the tensile direction is released and the rotor shaft 3 returns to room temperature, it contracts in the axial direction X and expands radially. Due to the axial force in the compressive direction of the rotor shaft 3, the stepped surface 36 and the leading impeller 4L, adjacent impellers 4 to each other, and the tail impeller 4T and the balance piston 56 are pressed against each other in the axial direction X. Furthermore, as the rotor shaft 3 expands radially, the balance piston 56 presses tightly against the rotor shaft 3, generating a clamping force, and thus aligns the rotor shaft 3 and the balance piston 56. In other words, the balance piston 56 is tightly fitted onto the rotor shaft 3. Since the multiple impellers 4 and balance pistons 56, 57 are aligned by mechanical couplings, the alignment of the rotor shaft 3 and the balance piston 56, that is, the alignment of the rotor shaft 3 and the impeller stack 40. When the balance piston 56 is tightly fitted as described above, instead of cooling the rotor shaft 3, the balance piston 56 may be heated.

[0036] Furthermore, as shown in the following modified examples 1 and 2, the rotor shaft 3 and the impeller stack 40 can be aligned without using the interference fit of the balance piston 56 with respect to the rotor shaft 3.

[0037] In the modified example 1 shown in Figure 7, the lock nut 6 has a truncated conical head 61 centered on the axis of the lock nut 6. The inner diameter of the balance piston 56 is larger than the outer diameter of the rotor shaft 3, and a tapered recess 561 centered on the axis of the balance piston 56 is formed on the end face in the axial direction X of the balance piston 56, into which the head 61 of the lock nut 6 fits. The balance piston 56 is then loosely fitted onto the rotor shaft 3, and subsequently the lock nut 6 is screwed onto the rotor shaft 3. With the head 61 of the lock nut 6 fitted into the recess 561 of the balance piston 56, the lock nut 6 is screwed in. In this way, a part of the lock nut 6 is interposed between the balance piston 56 and the rotor shaft 3 in the radial direction, and the balance piston 56 is pressed radially outward by this lock nut 6, thereby aligning the rotor shaft 3 and the balance piston 56, that is, aligning the rotor shaft 3 and the impeller stack 40. Furthermore, the balance piston 56 is pressed in the axial direction X by the lock nut 6, causing the stepped surface 36 and the leading impeller 4L, adjacent impellers 4 to press against each other, and the tail impeller 4T and the balance piston 56 to press against each other in the axial direction X.

[0038] In the modified example 2 shown in Figure 8, the inner diameter of the balance piston 56 is larger than the outer diameter of the rotor shaft 3, and the balance piston 56 is loosely fitted onto the rotor shaft 3. A cylindrical recess 562 is formed on the end face of the balance piston 56 in the axial direction X, centered on the axis of the balance piston 56. The balance piston 56 is loosely fitted onto the rotor shaft 3, and then an elastic compression ring 59 is fitted into the recess 562 of the balance piston 56, followed by the screwing of a lock nut 6 onto the rotor shaft 3. When the lock nut 6 presses against the compression ring 59, the compression ring 59 is compressed in the axial direction X and expands radially. The inner circumference of the elastically deformed compression ring 59 abuts against the rotor shaft 3, and the outer circumference abuts against the inner wall of the recess 562 of the balance piston 56. The compression ring 59 braces between the rotor shaft 3 and the balance piston 56, pushing the balance piston 56 radially outward. This aligns the rotor shaft 3 with the balance piston 56, that is, the rotor shaft 3 with the impeller stack 40. Furthermore, as the compression ring 59 is compressed in the axial direction X, the stepped surface 36 and the leading impeller 4L, adjacent impellers 4 with each other, and the tail impeller 4T and the balance piston 56 are pressed against each other in the axial direction X.

[0039] [Summary] The multi-stage rotor 2 relating to the first item of this disclosure is A rotor shaft 3 having a stepped surface 36 and composed of a single member, Multiple impellers 4 are fitted onto the rotor shaft 3 and are arranged in the axial direction X of the rotor shaft 3 from the stepped surface 36, It is equipped with a lock nut 6 fitted onto the rotor shaft 3, Multiple impellers 4 are sandwiched between a stepped surface 36 and a lock nut 6.

[0040] In the multi-stage rotor 2 with the above configuration, multiple impellers 4 are supported on a rotor shaft 3 that is directly supported by bearings 51, 52, and 53. The rotor shaft 3 is made of a single component and is not made by combining tie bolts and a stub shaft. Therefore, imbalance caused by misalignment between the rotor shaft and tie bolts, which is common in conventional designs, cannot occur. Furthermore, in the multi-stage rotor 2 with the above configuration, the shaft diameter of the portion of the rotor shaft 3 supported by bearings 51, 52, and 53, and the portion where dry gas seals 54 and 55 are located, can be reduced compared to the case where a combination of tie bolts and a stub shaft is used. This contributes to miniaturization of the bearings 51, 52, and 53 and the dry gas seals 54 and 55.

[0041] The multi-stage rotor 2 with the above configuration is suitable for centrifugal compressors that require a high compression ratio, targeting gases with low molar weight (MW), such as hydrogen. To increase the compression ratio of a centrifugal compressor, it is effective to increase the number of stages of the impeller 4 and increase the peripheral speed of the multi-stage rotor 2. Since increasing the number of stages of the impeller 4 increases the overall length of the rotor shaft 3, it is preferable to have a larger shaft diameter to suppress vibration due to rotation. In the conventional tie bolt system, the stepped surface of the stub shaft and the tie bolt is used to hold the impeller, so the shaft diameter of the tie bolt is smaller than that of the stub shaft. In contrast, in the multi-stage rotor 2 according to the present disclosure, the shaft diameter of the part of the rotor shaft 3 that supports the impeller 4 (i.e., the first section 31) can be made larger than the shaft diameter of the conventional tie bolt. Therefore, in the multi-stage rotor 2 according to the present disclosure, even if the overall length of the rotor shaft 3 is increased to accommodate the increase in the number of stages of the impeller 4, the dynamic strength against vibration of the rotor shaft 3 can be increased by increasing the shaft diameter of the part that supports the impeller 4. The increased dynamic strength of the rotor shaft 3 makes it possible to increase the peripheral speed of the multi-stage rotor 2.

[0042] The multi-stage rotor 2 relating to the second item is such that, in the multi-stage rotor 2 relating to the first item, the multiple impellers 4 are sandwiched between the stepped surface 36 and the lock nut 6 while being pressed by the axial force of the rotor shaft 3.

[0043] The multi-stage rotor 2 relating to the third item is a multi-stage rotor 2 relating to the first or second item, wherein the rotor shaft 3 has a pair of end sections 34 arranged at both ends in the axial direction X and supported by bearings 51, 52, and 53, and a first section 31 with a first shaft diameter and a second section 32 with a second shaft diameter larger than the first shaft diameter, arranged between the pair of end sections 34 in the axial direction X, the stepped surface 36 is located between the first section 31 and the second section 32, and a plurality of impellers 4 are fitted into the first section 31 of the rotor shaft 3.

[0044] According to the multi-stage rotor 2 configured as described above, the second section 32 of the rotor shaft 3 can be positioned at any position on the pair of end sections 34, and the second section 32 can be positioned appropriately depending on the configuration of the impeller stack 40.

[0045] For example, as shown in Figure 9, a second section 32 may be provided approximately in the center of the rotor shaft 3 in the axial direction X, and multiple impellers 4 may be arranged on both the non-load side and the load side via the second section 32. In this case, multiple impellers 4, balance pistons 56, and lock nuts 6 are fitted in order from the non-load side end of the rotor shaft 3, and the multiple impellers 4 and balance pistons 56 are sandwiched between the stepped surface 36 facing the non-load side of the multi-stage rotor 2 and the lock nuts 6. Similarly, multiple impellers 4, balance pistons 56, and lock nuts 6 are fitted in order from the load side end of the rotor shaft 3, and the multiple impellers 4 and balance pistons 56 are sandwiched between the stepped surface 36 facing the load side of the multi-stage rotor 2 and the lock nuts 6.

[0046] The multi-stage rotor 2 relating to the fourth item is a multi-stage rotor 2 relating to any of the first to third items, wherein among the multiple impellers 4, impellers 4 adjacent to each other in the axial direction X are concentrically connected by meshing, and among the multiple impellers 4, the first impeller (the leading impeller 4L in the above embodiment) that contacts the stepped surface 36 is connected to the stepped surface 36 by friction.

[0047] In this way, the rotor shaft 3 and the impeller stack 40, which consists of multiple impellers 4, are coupled in a way that enables power transmission.

[0048] The multi-stage rotor 2 relating to item 5 is a multi-stage rotor 2 relating to item 4 in which the inner surface of the first impeller (the leading impeller 4L in the above embodiment) and the outer surface of the rotor shaft 3 are in pressure contact, thereby arranging the first impeller 4L and the rotor shaft 3 concentrically.

[0049] In this way, by aligning the leading impeller 4L and the rotor shaft 3 so that the axis of the leading impeller 4L and the rotor axis A of the rotor shaft 3 coincide, imbalance during rotation of the multi-stage rotor 2 can be prevented.

[0050] The multi-stage rotor 2 relating to item 6 is a multi-stage rotor 2 relating to any of items 1 to 3, wherein among the multiple impellers 4, impellers 4 adjacent to each other in the axial direction X are concentrically connected by meshing, a cylindrical body 47 is positioned between the first impeller 4, which is located closest to the stepped surface 36 among the multiple impellers 4, and the stepped surface 36, the stepped surface 36 and the cylindrical body 47 are connected by friction, and the cylindrical body 47 and the first impeller 4 are concentrically connected by meshing.

[0051] In this way, the rotor shaft 3 and the impeller stack 40, which consists of multiple impellers 4, are coupled in a way that enables power transmission.

[0052] The multi-stage rotor 2 relating to item 7 is a multi-stage rotor 2 relating to any of items 1 to 6, and has a balance piston 56 that is positioned between the axial direction X of the multiple impellers 4 and the lock nut 6 and fitted onto the rotor shaft 3, and the second impeller (the tail impeller 4T in the above embodiment) that contacts the balance piston 56 among the multiple impellers 4 is concentrically coupled with the balance piston 56 by meshing.

[0053] In this way, by positioning the balance piston 56 between the tail impeller 4T and the lock nut 6, the balance piston 56 can be used to align the rotor shaft 3 and the multiple impellers 4.

[0054] The multi-stage rotor 2 relating to item 8 is a multi-stage rotor 2 relating to item 7 in which the balance piston 56 and the rotor shaft 3 are arranged concentrically by pressure contact between the inner surface of the balance piston 56 and the outer surface of the rotor shaft 3.

[0055] In this way, by aligning the balance piston 56 with the rotor shaft 3, the impeller stack 40 and the rotor shaft 3 are aligned, preventing imbalance during rotation of the multi-stage rotor 2.

[0056] The multi-stage rotor 2 relating to item 9 is the same as the multi-stage rotor 2 relating to item 7, in which the balance piston 56 is loosely fitted to the rotor shaft 3, and the balance piston 56 is pressed radially outward by a lock nut 6 or elastic body (compression ring 59 in the above embodiment) interposed between the balance piston 56 and the rotor shaft 3 in the radial direction, so that the balance piston 56 and the rotor shaft 3 are arranged concentrically.

[0057] In this way, by aligning the balance piston 56 with the rotor shaft 3, the impeller stack 40 and the rotor shaft 3 are aligned, preventing imbalance during rotation of the multi-stage rotor 2.

[0058] The multistage rotor 2 relating to item 10 of this disclosure is a multistage rotor 2 relating to any of items 1 to 9, wherein the rotor shaft 3 is made of steel and the multiple impellers 4 are made of aluminum.

[0059] By making multiple impellers 4 from aluminum, which has a higher specific strength compared to steel, the centrifugal stress acting on the impellers 4 can be reduced compared to when the impellers 4 are made of steel.

[0060] The multistage rotor 2 relating to item 11 of this disclosure is a multistage rotor 2 relating to any of items 1 to 10, wherein the ratio of the impeller hub diameter d2 of the multiple impellers 4 to the shaft diameter D4 of a pair of end sections 34 of the rotor shaft 3 (= impeller hub diameter d2 / shaft diameter D4) is 2.0 or more and 2.8 or less.

[0061] In the multi-stage rotor 2 described above, even if the impeller 4 is driven at a high enough speed to perform the work required to compress a gas with a low molecular weight and high gas constant (for example, hydrogen), it is possible to keep the temperatures of the journal bearings 51 and 52 below the allowable temperature.

[0062] The turbomachine 1 according to item 12 of this disclosure comprises a casing 12 and a multistage rotor 2 according to any of items 1 to 11 supported by the casing 12.

[0063] The multi-stage rotor 2 with the above configuration is suitable as a rotor for a turbomachinery 1, particularly a centrifugal compressor.

[0064] The turbomachinery 1 relating to item 13 of this disclosure is, in the turbomachinery 1 relating to item 12, A compression passage W through which the compressed fluid flows from the intake port 22, through multiple impellers 4 of the multi-stage rotor 2 in sequence, to the discharge port 23, The multi-stage rotor 2 comprises multiple impellers 4 and an internal passage 7 extending in the axial direction X between the rotor shaft 3 and the rotor shaft 3 in the radial direction, The compression passage W and the internal passage 7 are connected by connecting passages 73 and 74 that pass through the rotor shaft 3.

[0065] Since the connecting passages 73 and 74 are formed using the rotor shaft 3, machining for forming the connecting passages 73 and 74 is easy, and the bending rigidity of the part of the rotor shaft 3 that supports the impeller stack 40 is not affected by the connecting passages 73 and 74. In addition, because the connecting passage 73 passes through the rotor shaft 3, it is possible to position the point where the fluid is returned from the internal passage 7 further upstream than the inlet of the first-stage impeller 4A, thereby suppressing the influence of the fluid returned to the compression passage W on the main flow of the compression passage W.

[0066] The turbomachinery 1 relating to item 14 of this disclosure is the turbomachinery 1 relating to item 13, wherein the connecting passage 73 connects the internal passage 7 to a position upstream of the inlet of the first impeller 4 through which the fluid flows among the multiple impellers 4 of the compression passage W.

[0067] Because the connecting passage 73 passes through the rotor shaft 3 in this way, a configuration can be easily realized in which fluid is returned from the internal passage 7 to a position upstream of the inlet of the first-stage impeller 4A in the compression passage W. Furthermore, by returning the fluid to a position upstream of the inlet of the first-stage impeller 4A in the compression passage W, the influence of the returned fluid on the main flow in the compression passage W can be suppressed.

[0068] The turbomachinery 1 relating to item 15 of this disclosure is, in the turbomachinery 1 relating to item 12 (excluding the turbomachinery 1 referring to the multi-stage rotor 2 of item 6), A compression passage W through which the compressed fluid flows from the intake port 22, through multiple impellers 4 of the multi-stage rotor 2 in sequence, to the discharge port 23, The multi-stage rotor 2 comprises multiple impellers 4 and an internal passage 7 extending in the axial direction X between the rotor shaft 3 and the rotor shaft 3 in the radial direction, The stepped surface 36 of the rotor shaft 3 of the multi-stage rotor 2 and the planar contact surface 48 of the first impeller 4L among the multiple impellers 4 are in contact in the axial direction X, and the connecting passage 21 that connects the compression passage W and the internal passage 7 passes through a groove located on at least one of the stepped surface 36 and the contact surface 48.

[0069] The method for manufacturing the multi-stage rotor 2 relating to item 16 of this disclosure is: Multiple impellers 4 are fitted onto a rotor shaft 3, which has a stepped surface 36 and is composed of a single component, and This includes fitting a lock nut 6 onto the rotor shaft 3 and sandwiching multiple impellers 4 between the stepped surface 36 and the lock nut 6 while being pressed by the axial force of the rotor shaft 3.

[0070] According to the above-described method for manufacturing the multi-stage rotor 2, the multi-stage rotor 2 relating to the first item can be manufactured.

[0071] The discussions of this disclosure described above are presented for illustrative and explanatory purposes only and are not intended to limit the disclosure to the forms disclosed herein. For example, in the detailed description above, various features of the disclosure are grouped into a single embodiment for the purpose of streamlining the disclosure, but some of the features may be combined. Also, some of the features included in this disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0072] 1: Turbomachinery 2: Multistage rotor 3: Rotor shaft 4: Impeller 4L: Leading impeller (first impeller) 4T: Rear impeller (second impeller) 6: Lock nuts 7: Internal passage 12: Casing 21: Connecting passage 22: Inlet 23:Discharge port 31: Section 1 32: Section 2 34: End Section 36: Step surface 48: Contact surface 51: Journal bearing 52: Journal bearing 53: Thrust bearing 56: Balance Piston 57: Balance Piston 73: Connecting passage 74: Connecting passage W: Compression passage X: Axial direction

Claims

1. A rotor shaft having a stepped surface and composed of a single component, A plurality of impellers are fitted onto the rotor shaft and are arranged in the axial direction of the rotor shaft from the stepped surface, The rotor shaft is fitted with a lock nut, Each of the plurality of impellers includes an impeller hub having an impeller bore through which the rotor shaft is inserted, The rotor shaft has a pair of end sections arranged at both ends in the axial direction and supported by bearings, and a first section with a first shaft diameter smaller than the diameter of the impeller bore and a second section with a second shaft diameter larger than the diameter of the impeller bore, arranged between the pair of end sections in the axial direction. The stepped surface is a surface facing the axial direction that exists at the boundary between the first section and the second section due to the difference in shaft diameter between the first section and the second section, and the plurality of impellers are fitted into the first section of the rotor shaft. A multi-stage rotor in which the plurality of impellers are sandwiched between the stepped surface and the lock nut in the axial direction, under pressure from the axial force of the rotor shaft.

2. Among the plurality of impellers, those adjacent to each other in the axial direction are concentrically connected by meshing, and among the plurality of impellers, the first impeller that contacts the stepped surface is connected to the stepped surface by friction. The multi-stage rotor according to claim 1.

3. The inner surface of the first impeller is pressed against the outer surface of the rotor shaft, and the first impeller and the rotor shaft are arranged concentrically. The multi-stage rotor according to claim 2.

4. Among the plurality of impellers, those adjacent to each other in the axial direction are connected concentrically by meshing. A cylindrical body is positioned between the first impeller, which is located closest to the stepped surface among the plurality of impellers, and the stepped surface, and the cylindrical body and the stepped surface are coupled by friction, and the cylindrical body and the first impeller are concentrically coupled by meshing. The multi-stage rotor according to claim 1.

5. The rotor has a balance piston positioned between the plurality of impellers and the lock nut in the axial direction and fitted onto the rotor shaft, Of the plurality of impellers, the second impeller that contacts the balance piston is concentrically connected to the balance piston by meshing with it. The multi-stage rotor according to claim 1.

6. The inner surface of the balance piston is pressed against the outer surface of the rotor shaft, and the balance piston and the rotor shaft are arranged concentrically. The multi-stage rotor according to claim 5.

7. The balance piston is loosely fitted to the rotor shaft, and the balance piston is pressed radially outward by the lock nut or elastic body interposed between the balance piston and the rotor shaft in the radial direction, thereby causing the balance piston and the rotor shaft to be arranged concentrically. The multi-stage rotor according to claim 5.

8. The rotor shaft is made of steel, and the multiple impellers are made of aluminum alloy. The multi-stage rotor according to claim 1.

9. The ratio of the impeller hub diameter of the plurality of impellers to the shaft diameter of the pair of end sections of the rotor shaft is 2.0 or more and 2.8 or less. The multi-stage rotor according to claim 1.

10. Casing and, The multi-stage rotor according to claim 1, supported by the casing, Turbomachinery.

11. A compression passage through which the fluid to be compressed flows from the intake port through the multiple impellers of the multi-stage rotor in sequence to the discharge port, The multi-stage rotor comprises an internal passage extending in the axial direction between the plurality of impellers and the rotor shaft in the radial direction, The compression passage and the internal passage are connected by a connecting passage that passes through the rotor shaft. The turbomachinery according to claim 10.

12. The connecting passage connects the internal passage to a position upstream of the inlet of the impeller through which the fluid first flows among the plurality of impellers in the compression passage. The turbomachinery according to claim 11.

13. A compression passage through which the fluid to be compressed flows from the intake port through the multiple impellers of the multi-stage rotor in sequence to the discharge port, The multi-stage rotor comprises an internal passage extending in the axial direction between the plurality of impellers and the rotor shaft in the radial direction, The stepped surface of the rotor shaft of the multi-stage rotor and the planar contact surface of the first impeller among the plurality of impellers are in contact in the axial direction, and the connecting passage that connects the compression passage and the internal passage passes through a groove located on at least one of the stepped surface and the contact surface. The turbomachinery according to claim 10.

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