Centrifugal compressor

Abstract

To reduce constraints in the rotor manufacturing process. [Solution] The centrifugal compressor includes a stacked rotor 8 having a plurality of impellers 83, tie rods 86 that penetrate the hollow portions of the plurality of impellers 83, shaft ends 82 provided at the ends of the plurality of impellers 83, and a coupling drum 85 interposed between the shaft ends 82 and the impellers 83. The impeller 83 has a boss portion 83f with a hollow portion formed therein and a disc 83a with a plurality of blades 83c formed thereon, and the maximum outer diameter of the boss portion 83f of the impeller 83 on the gas intake side is smaller than the minimum inner diameter of the blades 83c.

Description

Technical Field

[0001] The present invention relates to a centrifugal compressor.

Background Art

[0002] The rotor of Patent Document 1 has a shaft end fixing portion that connects the first shaft end member to the first impeller. This shaft end fixing portion connects the first flange portion of the first shaft end member and the first enlarged diameter portion of the first impeller (see paragraph 0068 and FIG. 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the rotor of Patent Document 1, the outer diameter of the first enlarged diameter portion of the first impeller is larger than the outer diameter of the shaft portion (first disk extension portion) of the first impeller. When the first impeller is viewed axially from the side of the first shaft end member, the inner peripheral side end portion of the blade formed on the first impeller is hidden by the first enlarged diameter portion. In this case, for example, when trying to form an R-shaped portion (see FIG. 4) at the inner peripheral side end portion of the blade, when it is necessary to apply a machining tool axially from the side of the first enlarged diameter portion toward the inner peripheral side end portion of the blade, the first enlarged diameter portion gets in the way, making it difficult to apply the machining tool to the inner peripheral side end portion of the blade, and thus there are many restrictions in the manufacturing process of the rotor.

[0005] An object of the present invention is to provide a centrifugal compressor capable of reducing restrictions in the manufacturing process of the rotor.

Means for Solving the Problems

[0006] To solve the above problems, the centrifugal compressor of the present invention comprises a stacked rotor having a plurality of impellers, tie rods passing through the hollow portions of the plurality of impellers, and shaft ends provided at both ends of the plurality of impellers, and a coupling drum interposed between the shaft ends and the impellers. [Effects of the Invention]

[0007] According to the present invention, the constraints in the manufacturing process of the rotor in a centrifugal compressor can be reduced.

[0008] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a longitudinal cross-sectional view of a stack rotor according to one embodiment of the centrifugal compressor of the present invention. [Figure 2] This is a cross-sectional view showing the vicinity of the coupling drum used in the stack trodder according to the present invention. [Figure 3] This is a plan view showing the blade-forming surface of an impeller. [Figure 4] This is a cross-sectional view showing the radial direction of the impeller disc and the cross-section along the blades. [Figure 5] This is a longitudinal cross-sectional view showing the overall configuration of a centrifugal compressor (single-screw multi-stage centrifugal compressor) that serves as a comparative example of the present invention. [Figure 6] This is an enlarged cross-sectional view of the vicinity of the spigot structure between the coupling drum and tie rod used in the stack trodder according to the present invention. [Modes for carrying out the invention]

[0010] Before describing embodiments of the centrifugal compressor according to the present invention, a comparative example of a centrifugal compressor of the present invention will be described with reference to Figure 5. Figure 5 is a longitudinal cross-sectional view showing the overall configuration of a comparative example of a centrifugal compressor (single-shaft multi-stage centrifugal compressor) 1 of the present invention.

[0011] The centrifugal compressor 1 of the comparative example described below is used, for example, in multi-stage centrifugal compressors for ammonia, methanol, and other synthetic plants where stable operation is required over a wide flow rate range from the rated flow rate to the low flow rate side while maintaining the rated discharge pressure.

[0012] The centrifugal compressor 1 shown in Figure 5 is a single-shaft multi-stage centrifugal compressor in which impellers 7 are mounted in multiple stages on a single rotating shaft 6. The centrifugal compressor 1 has a casing 2 which is formed in a cylindrical shape or the like and serves as a stationary part. The casing 2 houses inside a rotating shaft 6 which is rotatably mounted by a radial bearing 3 on the non-driver side, a radial bearing 4 and a thrust bearing 5 on the drive side, and multiple stages (five stages in this example) of centrifugal impellers 7 which are shrink-fitted to the rotating shaft 6. The rotating shaft 6 and the centrifugal impellers 7 constitute the rotor (rotating body) 8' of the centrifugal compressor 1. Hereafter, the centrifugal impellers 7 will be referred to as "impellers" in the explanation.

[0013] The casing 2 is provided with an intake passage 9 for introducing the working fluid gas to the first stage impeller 7, a diffuser 10 for converting the kinetic energy of the gas exiting each stage impeller 7 into pressure energy, a return passage 11 for introducing the compressed gas from the diffuser 10 to the next stage impeller 7, and a discharge passage 12 for discharging the gas exiting the final stage impeller 7 to the outside of the casing 2.

[0014] The rotating shaft 6 of the rotor 8' is rotatably supported by a non-driver side radial bearing 3 and a drive-side radial bearing 4, which are provided at the gas intake side (left side in Figure 5) and gas discharge side (right side in Figure 5) ends of the casing 2. In addition, a thrust bearing 5 that receives thrust loads is provided at the gas intake side end of the rotating shaft 6, and a balance piston 13 that counteracts thrust loads is provided on the gas discharge side of the final stage impeller 7 on the rotating shaft 6.

[0015] Furthermore, a driving machine (not shown) such as a motor is connected to the gas discharge side end of the rotating shaft 6, and the rotor 8' is rotationally driven by this driving machine. Also, when the rotor 8' rotates, gas is sucked from the suction passage 9, sequentially compressed by the plurality of stages of impellers 7, and finally discharged from the discharge passage 12.

[0016] Also, a mouse labyrinth seal is provided in the gap between the shroud of each stage of the impeller 7 and the casing 2, and the mouse labyrinth seal suppresses the gas exiting the impeller 7 from returning to the inlet side of the impeller 7. Furthermore, an intermediate stage seal is provided in the gap between the rotor 8' and the casing 2 between the previous stage impeller 7 and the next subsequent stage impeller 7, and the intermediate stage seal suppresses the gas in the return passage 11 from returning to the outlet side of the previous stage impeller 7.

[0017] Also, a balance piston part labyrinth seal 14 is provided in the gap between the balance piston 13 of the rotor 8' and the casing 2, and the balance piston part labyrinth seal 14 suppresses the high-pressure gas (fluid) exiting the final stage impeller 7 from leaking to the low-pressure part.

[0018] In the centrifugal compressor 1 of the comparative example, the rotating shaft 6 is composed of a solid cylindrical member, and the impeller 7 is fixedly fitted to the rotating shaft 6 by shrink fitting. Therefore, when the rotational speed (rotational frequency) of the impeller 7 increases and it rotates at high speed, due to centrifugal force, the impeller 7 elastically deformes in the radial direction and moves away from the rotating shaft 6, or the surface pressure due to shrink fitting decreases. Thus, it was difficult for the centrifugal compressor 1 as in the comparative example to achieve sufficient high-speed operation.

[0019] Therefore, in order to achieve further high-speed operation of the centrifugal compressor 1, instead of the rotor 8' shown in FIG. 5, the rotor 8 as shown in FIG. 1 was considered. The rotor 8 in FIG. 1 is configured such that the rotating shaft 6 and the impeller 7 are laminated in the direction along the rotational axis of the rotor 8 (hereinafter, the rotational axis direction). For this reason, the rotor 8 is sometimes called a'stacked rotor'.

[0020] Referring to FIG. 1, an embodiment of the stack rotor 8 according to the present invention will be described. For the configuration other than the stack rotor 8, the same configuration as that described in the comparative example can be adopted. Therefore, for the same configuration as that in the comparative example, the same reference numerals as those used in FIG. 5 will be used for description.

[0021] FIG. 1 is a longitudinal sectional view of the stack rotor 8 according to an embodiment of the centrifugal compressor 1 of the present invention. The centrifugal compressor of the present embodiment can be configured in the same manner as the centrifugal compressor 1 in FIG. 5 except for the rotor 8'. For example, it can be used in a multi-stage centrifugal compressor for a synthesis plant such as ammonia or methanol that requires stable operation in a wide flow rate range from the rated flow rate to the small flow rate side while maintaining the rated discharge pressure. The rotor 8 in FIG. 1 can be applied to a multi-stage centrifugal compressor in which impellers 7 are provided in multiple stages with respect to one rotation axis Ax. In the following description, the stack rotor will be simply referred to as the "rotor" for explanation. Also, similar to FIG. 5, the right side of FIG. 1 is defined as the drive machine side.

[0022] The rotor 8 includes a first shaft end 81 disposed on the side opposite to the drive machine side (anti-drive machine side), a second shaft end 82 disposed on the drive machine side, impellers 83 (83A to 83D) disposed in a plurality of stages (four stages in this embodiment) between the first shaft end 81 and the second shaft end 82, a first coupling drum 84 interposed between the first shaft end 81 and the impeller 83A, a second coupling drum 85 interposed between the second shaft end 82 and the impeller 83D, a tie rod 86 inserted into the internal spaces of the first coupling drum 84, the impellers 83A to 83D, and the second coupling drum 85, a first tie rod nut 87 disposed at the anti-drive machine side end of the tie rod 86, and a second tie rod nut 88 disposed at the drive machine side end of the tie rod 86.

[0023] The impellers are arranged in a back-to-back configuration, with impellers 83A and 83D on the gas intake side and impellers 83B and 83C on the gas discharge side. In the comparative example in Figure 5, the five impellers are arranged in a straight-through configuration with the same orientation, and the intake passage 9 is located at one end of the row formed by the five impellers. In this embodiment, the intake passages 9a and 9b are located at both ends of the row formed by the four impellers 83A to 83D.

[0024] A coupling drum is positioned between the impeller and the shaft end of the first stage gas intake. Specifically, a first coupling drum 84 is positioned between the impeller 83A and the first shaft end 81, and a second coupling drum 85 is positioned between the impeller 83D and the second shaft end 82.

[0025] The first shaft end 81 is located on one end of the rotor 8. Specifically, the first shaft end 81 is located on the side of one end 86a of the tie rod 86, and is located on the opposite side from the second shaft end 82 with respect to the multiple impellers 83A to 83D. In this case, the first shaft end 81 is located on the gas intake side (intake passage 9a side) of the impeller 83A.

[0026] The end of the first shaft end 81 on the side opposite to the drive motor (first end) 81a is supported by bearings (the radial bearing 3 and thrust bearing 5 on the side opposite to the drive motor in Figure 5). At the radial center of the end of the first shaft end 811 on the impeller side (drive motor side) (second end) 81b, a space 81c is formed to accommodate the first threaded portion 86c of the tie rod 86 and the first tie rod nut 87. The second shaft end 82 is located on the other end side of the rotor 8. Specifically, the second shaft end 82 is located on the other end 86b side of the tie rod 86, and is located on the opposite side from the first shaft end 81 relative to the multiple impellers 83A to 83D. In this case, the second shaft end 82 is located on the gas intake side (intake passage 9b side) of the impeller 83D.

[0027] The drive-side end (first end) 82a of the second shaft end 82 is supported by a bearing (drive-side radial bearing 4 in Figure 5). At the radial center of the impeller-side (non-drive-side) end (second end) 82b of the second shaft end 82, a space 82c is formed to accommodate the second threaded portion 86d of the tie rod 86 and the second tie rod nut 88.

[0028] The tie rod 86 is positioned to pass through the internal spaces (hollow portions) 83e, 84e, and 85e provided in the impellers 83A to 83D, the first coupling drum 84, and the second coupling drum 85. The end 86a of the tie rod 86 on the first shaft end 81 side is provided with a first threaded portion 86c onto which a first tie rod nut 87 is screwed. The first tie rod nut 87 has a screw hole 87a that engages with the first threaded portion 86c. The end 86b of the tie rod 86 on the second shaft end 82 side is provided with a second threaded portion 86d onto which a second tie rod nut 88 is screwed. The second tie rod nut 88 has a screw hole 88a that engages with the second threaded portion 86d.

[0029] The first coupling drum 84 and the impeller 83A, the impellers 83A to 83D, and the impeller 83D and the second coupling drum 85 are each connected via a first connecting means 89a to transmit torque. The first connecting means 89a can be a joint, a pressure fit, a pin fastening, etc., and examples of joints include hearth joints and kervic joints.

[0030] A Haas joint is a joint in which radial teeth on the end face are formed either straight or tapered towards the inside. A Curvic joint is a joint in which convex teeth and concave teeth on the end face interlock.

[0031] The first shaft end 81 and the first coupling drum 84, and the second shaft end 82 and the second coupling drum 85 are connected via second connecting means 89b to transmit torque and secure the connection. The second connecting means 89b can be bolted, screw-fitted, or interlocking. Bolt fastening may also be used in conjunction with a joint.

[0032] The first tie rod nut 87 is screwed onto the first threaded portion 86c of the tie rod 86, and when screwed in, the end on the drive side (impeller side) contacts the nut receiving surface 84a of the first coupling drum 84. The second tie rod nut 88 is screwed onto the second threaded portion 86d of the tie rod 86, and when screwed in, the end on the opposite drive side (impeller side) contacts the nut receiving surface 85a of the second coupling drum 85. By pressing the first tie rod nut 87 and the second tie rod nut 88 against the first coupling drum 84 and the second coupling drum 85, respectively, with a predetermined preload, the impellers 83A to 83D and the first coupling drum 84 and the second coupling drum 85 are tightened and fixed in the direction of the rotation axis. This tightening and fixing process also fixes the connection between the first coupling drum 84 and the impeller 83A, between the multiple impellers 83A to 83D, and between the impeller 83D and the second coupling drum 85 in the circumferential direction via the first connecting means 89a, thereby integrating the impellers 83A to 83D, the coupling drums 84 and 85, the tie rod 86, and the tie rod nuts 87 and 88.

[0033] After tightening the first tie rod nut 87 and the second tie rod nut 88, the first shaft end 81 is connected to the end of the first coupling drum 84 on the side opposite the drive unit via the second connecting means 89b, and the second shaft end 82 is connected to the end of the second coupling drum 85 on the drive unit side via the second connecting means 89b, thereby assembling the stack rotor 8 of the centrifugal compressor 1.

[0034] By configuring the rotor 8 as a stacked rotor, the impeller 83 is not fixed to the rotating shaft 6 by being compressed and fitted, as shown in rotor 8' in Figure 5, thus enabling the centrifugal compressor 1 to operate at a higher speed.

[0035] The impeller 83 (83A to 83D) will be described with reference to Figures 2 to 4. In this embodiment, the first connecting means 89a connecting impeller 83B and impeller 83C has a similar configuration on both the drive side and the non-drive side, with the first connecting means 89a being the plane of symmetry. Therefore, the structure on the drive side will be described here. Figure 2 is a cross-sectional view showing the vicinity of the second coupling drum 85 used in the stack trotor 8 according to the present invention. Note that impellers 83A to 83D have similar configurations and will be described as "impeller 83". The impeller 83 has a disc 83a, a shroud 83b, and a plurality of blades 83c. The disc 83a and the shroud 83b are arranged opposite each other, and the plurality of blades 83c are positioned between the disc 83a and the shroud 83b.

[0036] Figure 3 is a plan view showing the blade-forming surface 83d of the impeller 83 (83A-83D). Figure 4 is a cross-sectional view showing the radial direction of the disk 83a of impeller 83D and a cross section along the blade 83c. As shown in Figure 3, the disk 83a is composed of a hollow disc-shaped member with a space (hollow portion) 83e formed in the radial center. Multiple blades 83c are arranged at intervals in the circumferential direction centered on the rotation axis Ax. As shown in Figure 4, the multiple blades 83c are formed on one end face (blade-forming surface) 83d of the disk 83a in the axial direction.

[0037] The disc 83a has a boss portion 83f on the inner diameter side of the blade-forming surface 83d. The boss portion 83f is formed in a cylindrical shape with a hollow portion 83e. In addition, to improve the efficiency of the centrifugal compressor 1, the blade 83c has an R-shaped portion 83c1 at its inner circumferential end.

[0038] If a flange 83f' is provided on the boss portion 83f of the impeller 83D, which is the first stage of gas intake, as shown by the dotted line, in order to provide a labyrinth seal 90, to form part of the suction passage 9b, or to connect to the second shaft end 82, then when the impeller 83D is viewed from the direction of the rotation axis, the R-shaped portion 83c1 will be hidden behind the flange 83f'. When forming the R-shaped portion 83c1, if the machining tool TL is applied from a direction along the rotation axis Ax (see Figure 2) as shown in Figure 4, it becomes impossible to apply the machining tool TL to the R-shaped portion 83c1.

[0039] The centrifugal compressor 1 of this embodiment includes a stacked rotor 8 having a plurality of impellers 83 (83A to 83D) having a hollow portion 83e, a tie rod 86 passing through the plurality of impellers 83, a first shaft end 81 provided on one end of the plurality of impellers 83, a second shaft end 82 provided on the other end of the plurality of impellers 83, a first coupling drum 84 interposed between the first shaft end 81 and impeller 83A, and a second coupling drum 85 interposed between the second shaft end 82 and impeller 83D. The impeller 83 has a boss portion 83f in which a hollow portion 83e is formed, a disk 83a having a blade forming surface 83d on which a plurality of blades 83c are formed, and a shroud 83b arranged opposite the disk 83a. The first coupling drum 84 has connecting means 89b and 89a on the side of the first shaft end 81 and the side of the impeller 83A, respectively, and is connected to the first shaft end 81 and the impeller 83A. The second coupling drum 85 has connecting means 89b and 89a on the side of the second shaft end 82 and the side of the impeller 83D, respectively, and is connected to the second shaft end 82 and the impeller 83D.

[0040] This allows the stack rotor 8 to be assembled without the need for flange 83f'. Furthermore, it reduces constraints in the manufacturing process of the rotor 8.

[0041] As described above, the fixing structure of the first shaft end 81, the first coupling drum 84, the impellers 83A to 83D, the second coupling drum 85, and the second shaft end 82 is adopted, so the impeller 83 (83A, 83D) which is the first stage of gas intake in this embodiment does not need to have a flange 83f'. For this reason, the maximum radius R83f of the boss portion 83f on the gas intake side (coupling drum side) of the impeller 83 in this embodiment can be made smaller than the radius R83f' when a flange 83f' is present. The boss portion 83f in this embodiment is configured such that its maximum radius R83f is smaller than the minimum radius R83c1 of the R-shaped portion 83c1. Note that the maximum radius R83f of the boss portion is made smaller than the minimum radius R83c1 of the R-shaped portion 83c1, taking into account the radial thickness of the machining tool TL.

[0042] If the first connecting means 89a is a joint, in order to process the joint, the position 83g (see Figure 2) in the rotational axis direction of the end face of the boss portion 83f of the impeller 83D on the side of the second coupling drum 85 (gas intake side) is positioned on the gas intake side of the tip position 83b1 (see Figure 2) in the rotational axis direction of the gas intake side of the shroud 83b.

[0043] The shape characteristics of the fixed structure of the impellers 83A to 83D using coupling drums 84 and 85 will be explained with reference to Figure 2. In this embodiment, the centrifugal compressor 1 transmits the torque of the drive unit from the second shaft end 82 to the impellers 83A to 83D. In this case, the impellers 83A to 83D are integrated by receiving the pressing force (fastening force) from the first tie rod nut 87 and the second tie rod nut 88, respectively, via the first coupling drum 84 and the second coupling drum 85, and receive the torque of the drive unit from the second shaft end 82 via the second coupling drum 85.

[0044] The second coupling drum 85 is formed in an annular (cylindrical) shape, with a first connecting means 89a positioned on the impeller 83D side of the second coupling drum 85 and a second connecting means 89b positioned on the second shaft end 82 side. The maximum outer diameter D85 of the second coupling drum 85 is larger than the maximum outer diameter (maximum diameter) D83f (=R83f×2) of the boss portion 83f on the second coupling drum 82 side of the impeller 83D, and is formed to be equivalent to (the same size as in this embodiment) the outer diameter D82b of the flange 82b of the second shaft end 82. When the second coupling drum 85 is connected to the flange 82b of the second shaft end 82 by bolt fastening, it is reasonable to make the maximum outer diameter (maximum diameter) D85 of the second coupling drum 85 the same size as the outer diameter D82b of the flange 82b. Furthermore, when arranging the labyrinth seal 90, it is also preferable to make the maximum outer diameter D85 of the second coupling drum 85 the same size as the outer diameter D82b of the flange 82b.

[0045] The second coupling drum 85 has an inclined surface (tapered surface) 85d that widens in diameter from the outer peripheral edge of the first end face 85b on the impeller 83D side toward the second end face 85c on the second shaft end 82 side. When the inclined surface 85d is present in this way, the outer diameter D85b of the first end face 85b on the impeller 83D side of the second coupling drum 85 is smaller than the outer diameter D85c of the second end face 85c on the second shaft end 82 side. Here, the outer diameter D85c of the second end face 85c is the same as the maximum outer diameter D85 of the second coupling drum 85. The inclined surface 85d constitutes part of the suction passage 9b for the fluid drawn into the impeller 83D. By constituting part of the suction passage 9b with the second coupling drum 85, the second coupling drum 85 can be effectively utilized as space for the suction passage 9b, and the enlargement of the rotor 8 caused by the placement of the second coupling drum 85 can be suppressed.

[0046] The second coupling drum 85 has a nut receiving surface 85a for receiving the second tie rod nut 88. The nut receiving surface 85a is provided on the end face of the second coupling drum 85 on the side of the second shaft end 82.

[0047] The second coupling drum 85 and the tie rod 86 are fitted together in a spigot structure, where the protrusion 85f on the inner diameter side of the second coupling drum 85 and the protrusion 86e on the outer diameter side of the tie rod 86 are facing each other. As a result, the tie rod 86 is centered when fitted into the second coupling drum 85.

[0048] Figure 6 shows an enlarged view of the area near the spigot structure of the second coupling drum 85 and tie rod 86 described above. The convex portion 86e of the tie rod 86 has a recess 86f on the spigot surface (outer diameter side surface), and an O-ring 91 is installed in this recess 86f. By the O-ring 91 contacting the second coupling drum 85 and tie rod 86, that is, by installing a sealing structure in the space between the second coupling drum 85 and tie rod 86, high-pressure gas leaking from the first connecting means 89a is prevented from leaking into the space 82c side (low-pressure part) of the second shaft end 82 that houses the second tie rod nut 88. In this embodiment, a recess is provided on the spigot surface of the tie rod and an O-ring 91 is installed therein, but a recess may also be provided on the spigot surface of the second coupling drum and an O-ring may be installed therein. In addition, a sealing structure such as an O-ring may be installed in a place other than the spigot surface.

[0049] The centrifugal compressor 1 of this embodiment described above has the following features. (1) A centrifugal compressor 1 comprising a stacked rotor 8 having a plurality of impellers 83 (83A to 83D), tie rods 86 that pass through the hollow portions 83e of the plurality of impellers 83, a first shaft end 81 provided on one end of the plurality of impellers 83, and a second shaft end 82 provided on the other end of the plurality of impellers 83, The rotor has a first coupling drum 84 interposed between the first shaft end 81 and the impeller 83A, and a second coupling drum 85 interposed between the second shaft end 82 and the impeller 83D. In this embodiment, there are coupling drums on both the drive side and the non-drive side, but depending on the structure of the stack trotor, there may be a coupling drum on only one side. In addition, the impeller arrangement is back-to-back, but it may also be straight-through, and the impeller and coupling drum are integrated by tightening from both sides with tie rod nuts screwed onto both ends of the tie rod, but the structure is not limited to this, and a structure in which one end of the tie rod is screwed into the shaft end and the other end of the tie rod is tightened with a tie rod nut may also be used to integrate them.

[0050] In the centrifugal compressor 1 described above, the impeller 83 has the following characteristics. The description is for impeller 83D, but it applies to all impellers 83. (2) The impeller 83 has a boss portion 83f with a hollow portion 83e formed thereon, a disc 83a having a blade-forming surface 83d with a plurality of blades 83c formed thereon, and a shroud 83b positioned opposite the disc 83a, wherein the maximum radius R83f on the gas intake side of the boss portion 83f is smaller than the minimum radius R83c1 of the R-shaped portion 83c1 at the inner diameter end of the blade 83c. That is, the maximum outer diameter (R83f × 2) on the gas intake side of the boss portion 83f of the impeller 83 is smaller than the minimum inner diameter (R83c1 × 2) of the blade 83c. In this embodiment, the impeller 83 is a closed type impeller with a shroud 83b, but an open type impeller without a shroud 83b may also be used.

[0051] (3) When the impeller 83 has a shroud 83b and is connected by a coupling as the first connecting means 89a, the rotational axis position 83g of the gas intake side end face of the boss portion 83f of the impeller 83D is on the gas intake side than the rotational axis position 83b1 of the gas intake side tip of the shroud 83b.

[0052] In the centrifugal compressor 1 described above, the first coupling drum 84 and the second coupling drum 85 have the following characteristics. Since the first coupling drum 84 and the second coupling drum have similar structures, the description is for the second coupling drum 85, but it also applies to the first coupling drum 84.

[0053] (4) The outer diameter D85 of the second coupling drum 85 is larger than the maximum outer diameter D83f of the gas intake side of the boss portion 83f of the impeller 83D.

[0054] (5) The second coupling drum 85 has an outer diameter D85b of the first end face 85b on the side of the impeller 83D that is smaller than the outer diameter D85c of the second end face 85c on the side of the second shaft end 82.

[0055] (6) The second coupling drum 85 has an inclined surface 85d that widens in diameter from the first end face 85b on the impeller 83D side toward the second end face 85c on the second shaft end 82 side.

[0056] (7) The second coupling drum 85 has a nut receiving surface 85a for a second tie rod nut 88 that is screwed onto the tie rod 86 and tightens the second coupling drum 85 in the direction of the rotation axis.

[0057] (8) The second coupling drum 85 has a labyrinth seal 90 positioned on its outer diameter side.

[0058] (9) The second coupling drum 85 has a protrusion 85f on the inner diameter side that has a spigot surface for centering the tie rod 86.

[0059] (10) A seal is provided in the space between the second coupling drum 85 and the tie rod 86, and as an example, an O-ring 91 is installed on the aforementioned spigot surface.

[0060] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are explained in detail to make the present invention easier to understand, and are not necessarily limited to those having all of the above configurations. Furthermore, it is possible to add, delete, or replace some of the configurations in each embodiment with other configurations. [Explanation of Symbols]

[0061] 1...Centrifugal compressor, 8...Stack rotor (rotor), 81...First shaft end, 82...Second shaft end, 83 (83A~83D)...Impeller, 83a...Disc, 83b...Shroud, 83c...Blade, 83d...Blade forming surface, 83e...Hollow section, 83f...Boss section, 84...First coupling drum, 85...Second coupling drum, 85a...Nut receiving surface, 85b...First end face of second coupling drum 85, 85c...Second end face of second coupling drum 85, 85d...Inclined surface, 86...Tie rod, 87...First tie rod nut, 88...Second tie rod nut, 89a...First connecting means, 89b...Second connecting means, 90...Labyrinth seal, 91...O-ring.

Claims

1. A centrifugal compressor comprising a stack trotor having a plurality of impellers, tie rods passing through the hollow portions of the plurality of impellers, and shaft ends provided at both ends of the plurality of impellers, A centrifugal compressor having a coupling drum interposed between the shaft end and the impeller.

2. In the centrifugal compressor according to claim 1, The impeller has a boss portion in which the hollow portion is formed and a disk in which a plurality of blades are formed, wherein the boss portion of the impeller has a maximum outer diameter on the gas intake side that is smaller than the minimum inner diameter of the blades, making it a centrifugal compressor.

3. In the centrifugal compressor according to claim 1, The impeller comprises a boss portion in which the hollow portion is formed, a disc in which a plurality of blades are formed, and a shroud positioned opposite the disc, wherein the boss portion of the impeller is a centrifugal compressor in which the maximum outer diameter on the gas intake side is smaller than the minimum inner diameter of the blades.

4. In the centrifugal compressor according to claim 3, The impeller is a centrifugal compressor in which the rotational axis position of the gas intake end face of the boss portion is on the gas intake side than the rotational axis position of the gas intake tip of the shroud.

5. In the centrifugal compressor according to claim 2 or 3, A centrifugal compressor in which the outer diameter of the coupling drum is larger than the maximum outer diameter of the gas intake side of the boss portion of the impeller.

6. In the centrifugal compressor according to claim 2 or 3, The coupling drum is a centrifugal compressor in which the outer diameter of the first end face on the impeller side is smaller than the outer diameter of the second end face on the shaft end side.

7. In the centrifugal compressor according to claim 6, The coupling drum is a centrifugal compressor having an inclined surface that widens in diameter from the first end face toward the second end face on the shaft end side.

8. In the centrifugal compressor according to claim 2 or 3, The coupling drum is a centrifugal compressor having a nut receiving surface that connects to a tie rod nut which is screwed onto the tie rod and tightens the coupling drum in the direction of the rotation axis.

9. In the centrifugal compressor according to claim 2 or 3, A centrifugal compressor in which a labyrinth seal is positioned on the outer diameter side of the coupling drum.

10. In the centrifugal compressor according to claim 2 or 3, A centrifugal compressor having a spigot surface on the inner diameter side of the coupling drum for centering the tie rod.

11. In the centrifugal compressor according to claim 10, A centrifugal compressor in which an O-ring is installed on the aforementioned spigot surface.

12. In the centrifugal compressor according to claim 2 or 3, A centrifugal compressor having a seal in the space between the coupling drum and the tie rod.

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