Centrifugal compressor

Abstract

The present invention reduces restrictions on a rotor manufacturing process. This centrifugal compressor is provided with a stacked rotor 8 having a plurality of impellers 83, a tie rod 86 penetrating hollow parts of the plurality of impellers 83, a shaft end 82 provided at an end part of the plurality of impellers 83, and a coupling drum 85 interposed between the shaft end 82 and the impellers 83. The impellers 83 have a boss part 83f having a hollow part therein, and a disk 83a having a plurality of blades 83c. The maximum outside diameter of the boss part 83f of the impellers 83 on the gas suction side is smaller than the minimum inside diameter of the blades 83c.

Description

Centrifugal compressor 【0001】 The present invention relates to a centrifugal compressor. 【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). 【0003】 WO2024 / 043269A1 【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 viewing the first impeller axially from the side of the first shaft end member, the inner peripheral side end portion of the blades 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 and it becomes difficult to apply the machining tool to the inner peripheral side end portion of the blade, etc., and 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. 【0006】 To solve the above problems, the centrifugal compressor of the present invention includes a stacked rotor having a plurality of impellers, a tie rod penetrating the hollow portions of the plurality of impellers, and shaft ends provided at both ends of the plurality of impellers, and has a coupling drum interposed between the shaft ends and the impellers. 【0007】 According to the present invention, in a centrifugal compressor, restrictions in the manufacturing process of the rotor can be reduced. 【0008】 Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments. 【0009】This is a longitudinal cross-sectional view of a stacked rotor according to one embodiment of the centrifugal compressor of the present invention. This is a cross-sectional view showing the vicinity of the coupling drum used in the stacked rotor according to the present invention. This is a plan view showing the blade forming surface of the impeller. This is a cross-sectional view showing the radial direction of the impeller disk and the cross section along the blades. This is a longitudinal cross-sectional view showing the overall configuration of a centrifugal compressor (single-shaft multi-stage centrifugal compressor) that is a comparative example of the present invention. This is an enlarged cross-sectional view of the vicinity of the spigot structure between the coupling drum and tie rod used in the stacked rotor according to the present 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 synthesis plants of ammonia, methanol, etc., 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 on the driver side, and a thrust bearing 5, and multiple stages (five stages in this example) of centrifugal impellers 7 which are shrink-fitted onto 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 that converts 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 drive unit (not shown), such as a motor, is connected to the gas discharge end of the rotating shaft 6, and this drive unit rotates the rotor 8'. As the rotor 8' rotates, gas is drawn in from the intake passage 9, sequentially compressed by the multiple impellers 7, and finally discharged from the discharge passage 12. 【0016】 Furthermore, a mouth labyrinth seal is provided in the gap between the shroud of each impeller 7 and the casing 2, which prevents the gas exiting the impeller 7 from returning to the inlet side of the impeller 7. In addition, an intermediate stage seal is provided in the gap between the rotor 8' and the casing 2 between the preceding impeller 7 and the following succeeding impeller 7, which prevents the gas in the return passage 11 from returning to the outlet side of the preceding impeller 7. 【0017】 Furthermore, a balance piston labyrinth seal 14 is provided in the gap between the balance piston 13 of the rotor 8' and the casing 2. The balance piston labyrinth seal 14 prevents high-pressure gas (fluid) from the final stage impeller 7 from leaking into the low-pressure area. 【0018】 In the comparative example centrifugal compressor 1, the rotating shaft 6 is made of a solid cylindrical member, and the impeller 7 is fitted to the rotating shaft 6 by shrink fitting. Therefore, when the rotational speed (rotational speed) of the impeller 7 increases and it rotates at high speed, the impeller 7 elastically deforms radially due to centrifugal force and moves away from the rotating shaft 6, or the surface pressure due to the interference fit decreases, making it difficult for a centrifugal compressor 1 like the comparative example to achieve sufficient high speed. 【0019】Therefore, in order to further increase the speed of the centrifugal compressor 1, a rotor 8 as shown in Figure 1 was considered as an alternative to the rotor 8' shown in Figure 5. The rotor 8 in Figure 1 is constructed by stacking the rotating shaft 6 and the impeller 7 in a direction along the rotation axis of the rotor 8 (hereinafter referred to as the rotation axis direction). For this reason, the rotor 8 is sometimes called a "stacked rotor". 【0020】 Referring to Figure 1, an embodiment of the stack trotor 8 according to the present invention will be described. The components other than the stack trotor 8 can be configured in the same way as those described in the comparative example. Therefore, components similar to those in the comparative example will be described using the same reference numerals as those used in Figure 5. 【0021】 Figure 1 is a longitudinal cross-sectional view of a stack rotor 8 according to one embodiment of the centrifugal compressor 1 of the present invention. The centrifugal compressor of this embodiment can be configured in the same way as the centrifugal compressor 1 of Figure 5, except for the rotor 8', and can be used, for example, as a multi-stage centrifugal compressor for synthesis plants of ammonia, methanol, etc., 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. The rotor 8 of Figure 1 can be applied to a multi-stage centrifugal compressor in which impellers 7 are arranged in multiple stages around a single rotation axis Ax. In the following description, the stack rotor will be simply referred to as the "rotor". Also, as in Figure 5, the right side of Figure 1 is the drive side. 【0022】 The rotor 8 comprises a first shaft end 81 located on the opposite side from the drive motor (non-drive motor side), a second shaft end 82 located on the drive motor side, impellers 83 (83A to 83D) arranged in multiple 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 through the internal space of the first coupling drum 84, the impellers 83A to 83D, and the second coupling drum 85, a first tie rod nut 87 located at the end of the tie rod 86 on the non-drive motor side, and a second tie rod nut 88 located at the end of the tie rod 86 on the drive motor side. 【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 provided on one end of the rotor 8. Specifically, the first shaft end 81 is provided on one end 86a of the tie rod 86 and is provided 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 a bearing (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 provided on the other end side of the rotor 8. Specifically, the second shaft end 82 is provided on the other end 86b side of the tie rod 86 and is provided on the side opposite to the first shaft end 81 with respect to the plurality of 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 penetrate 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 connected via 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 to 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 impellers 83 (83A to 83D) will be described with reference to Figures 2 to 4. In this embodiment, the first connecting means 89a connecting impellers 83B and impellers 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 trodder 8 according to the present invention. Since the impellers 83A to 83D have a similar configuration, they will be described as "impeller 83". The impeller 83 has a disk 83a, a shroud 83b, and a plurality of blades 83c. The disk 83a and the shroud 83b are arranged opposite each other, and the plurality of blades 83c are arranged between the disk 83a and the shroud 83b. 【0036】 Figure 3 is a plan view showing the blade-forming surface 83d of the impeller 83 (83A to 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 blades 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. The 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 circumference 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 to face 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 that the impellers 83 (83A, 83D) that form the first stage of gas intake in this embodiment do 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) 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) of the shroud 83b on the gas intake side. 【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 shape (cylindrical shape). On the side of the impeller 83D of the second coupling drum 85, a first connecting means 89a is arranged, and on the side of the second shaft end 82, a second connecting means 89b is arranged. 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 side of the second coupling drum 82 of the impeller 83D, and is formed to be equal (the same size in this embodiment) to the outer diameter D82b of the flange 82b of the second shaft end 82. When connecting the second coupling drum 85 to the flange 82b of the second shaft end 82 by bolt fastening, it is reasonable that the maximum outer diameter (maximum diameter) D85 of the second coupling drum 85 is the same size as the outer diameter D82b of the flange 82b. Also, in terms of arranging the labyrinth seal 90, it is preferable that the maximum outer diameter D85 of the second coupling drum 85 is the same size as the outer diameter D82b of the flange 82b. 【0045】 The second coupling drum 85 has an inclined surface (taper surface) 85d that expands in diameter from the outer peripheral edge of the first end surface 85b on the side of the impeller 83D toward the side of the second end surface 85c on the side of the second shaft end 82. When having such an inclined surface 85d, the outer diameter D85b of the first end surface 85b of the second coupling drum 85 on the side of the impeller 83D is smaller than the outer diameter D85c of the second end surface 85c on the side of the second shaft end 82. Here, the outer diameter D85c of the second end surface 85c is the same as the maximum outer diameter D85 of the second coupling drum 85. The inclined surface 85d constitutes a part of the suction flow path 9b of the fluid sucked into the impeller 83D. By configuring a part of the suction flow path 9b in the second coupling drum 85, the second coupling drum 85 can be effectively utilized as the arrangement space of the suction flow path 9b, and the enlargement of the rotor 8 due to the arrangement 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 surface 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 have an in-rolling structure that fits on the opposing surfaces of the convex portion 85f on the inner diameter side of the second coupling drum 85 and the convex portion 86e on the outer diameter side of the tie rod 86. As a result, the tie rod 86 is centered by being fitted to the second coupling drum 85. 【0048】 An enlarged view of the vicinity of the in-rolling structure of the second coupling drum 85 and the tie rod 86 described above is shown in FIG. 6. The in-rolling surface (outer diameter side surface) of the convex portion 86e of the tie rod 86 has a recess 86f, and an O-ring 91 is installed in the recess 86f. When the O-ring 91 contacts the second coupling drum 85 and the tie rod 86, that is, when a seal structure is installed in the space between the second coupling drum 85 and the tie rod 86, high-pressure gas leaking from the first connecting means 89a is prevented from leaking into the space portion 82c side (low-pressure portion) of the second shaft end 82 that houses the second tie rod nut 88. In this embodiment, a recess is provided on the in-rolling surface of the tie rod and the O-ring 91 is installed, but a recess may be provided on the in-rolling surface of the second coupling drum and the O-ring may be installed. Also, a seal structure such as an O-ring may be installed other than the in-rolling surface. 【0049】The centrifugal compressor 1 of the above-described embodiment has the following features: (1) A centrifugal compressor 1 comprising a stack trotor 8 having a plurality of impellers 83 (83A to 83D), tie rods 86 that penetrate the hollow portions 83e of the plurality of impellers 83, a first shaft end 81 provided on one end side of the plurality of impellers 83, and a second shaft end 82 provided on the other end side of the plurality of impellers 83, wherein the centrifugal compressor 1 comprises 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. 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. Furthermore, while the impeller arrangement is back-to-back, it may also be straight-through. The impeller and coupling drum are integrated by being tightened from both sides with tie rod nuts screwed onto both ends of the tie rod, but the design is not limited to this structure. Other designs, such as screwing one end of the tie rod into the shaft end and tightening the other end of the tie rod with a tie rod nut, are also acceptable. 【0050】 In the centrifugal compressor 1 described above, the impeller 83 has the following characteristics. The description is for impeller 83D, but applies to all impellers 83. (2) 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, 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 boss portion 83f of the impeller 83D on the gas intake side. 【0054】 (5) The second coupling drum 85 has an outer diameter D85b on the side of the first end face 85b facing the impeller 83D that is smaller than the outer diameter D85c on the side of the second end face 85c facing 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 the outer diameter side of the second coupling drum 85. 【0058】 (9) The second coupling drum 85 has a spigot surface on the inner diameter side of the protrusion 85f 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 spigot surface described above. 【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. In addition, it is possible to add, delete, or replace some of the configurations in each embodiment with other configurations. 【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, wherein the centrifugal compressor has a coupling drum interposed between the shaft ends and the impellers.

2. A centrifugal compressor according to claim 1, wherein the impeller has a boss portion in which the hollow portion is formed and a disk in which a plurality of blades are formed, and 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.

3. A centrifugal compressor according to claim 1, wherein the impeller has a boss portion in which the hollow portion is formed, a disk in which a plurality of blades are formed, and a shroud arranged opposite to the disk, and 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.

4. A centrifugal compressor according to claim 3, wherein the impeller is such that the rotational axis position of the gas intake side end face of the boss portion is on the gas intake side than the rotational axis position of the gas intake side tip of the shroud.

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

6. A centrifugal compressor according to claim 2 or 3, wherein the coupling drum has an outer diameter smaller than the outer diameter of the first end face on the impeller side than the outer diameter of the second end face on the shaft end side.

7. A centrifugal compressor according to claim 6, wherein the coupling drum has an inclined surface that widens in diameter from the first end face toward the second end face on the shaft end side.

8. A centrifugal compressor according to claim 2 or 3, wherein the coupling drum has a nut receiving surface that connects to a tie rod nut that is screwed onto the tie rod and tightens the coupling drum in the rotational axis direction.

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

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

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

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

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