Casing of multistage centrifugal compressor, and the multistage centrifugal compressor

Abstract

To enable a purpose-shape flow path to be formed in a casing while preventing an increase in workload when casting the casing of a multistage centrifugal compressor.SOLUTION: The casing of the multistage centrifugal compressor which stores a rotor including a rotary shaft and a plurality of impellers arranged on the rotary shaft so as to be driven rotationally around the axis line of the rotary shaft, includes a casing body as an integral cast body including a rotor storage space, a casing piece detachably mounted to the casing body, and a volute for distributing fluid passing through a diffuser which is arranged in the rotor storage space for distributing the fluid from the impellers to the radial outward direction of the rotary shaft, around the axis line of the rotor. The flow path of the volute is defined by the casing body and the casing piece.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a casing for a multi-stage centrifugal compressor and a multi-stage centrifugal compressor. [Background technology]

[0002] As disclosed in Patent Document 1, there is known a multi-stage centrifugal compressor having a casing, a rotating shaft provided in the casing, and an impeller fixed to the rotating shaft. Patent Document 1 describes that a partition wall separating a main flow and an injection flow is integrally formed with the casing by casting or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-144698 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a casing for a multi-stage centrifugal compressor by casting, for example, a tool is inserted from the outside into the cast casing to machine the flow passages inside the casing. However, for example, it may be difficult to insert a tool from the outside into the narrow opening of the flow passage of the casing integrally formed by casting and machine the flow passage at the desired position. This increases the workload when performing this machining. To address this problem, for example, if an attempt is made to widen the opening of the flow passage of the casing in advance, there is a risk that the flow passage formed in the casing will have a shape different from the desired shape.

[0005] Therefore, an object of the present disclosure is to enable the formation of a flow path of a desired shape inside a casing of a multi-stage centrifugal compressor while preventing an increase in the workload when the casing is formed by casting. [Means for solving the problem]

[0006] One aspect of the present disclosure is a casing for a multi-stage centrifugal compressor that houses a rotor including a rotating shaft and a plurality of impellers that are arranged on the rotating shaft and are driven to rotate around the axis of the rotating shaft, the casing comprising: a casing main body that includes a rotor accommodating space and is an integral casting; casing pieces that are detachably attached to the casing main body; and a volute that circulates a fluid around the axis of the rotor after passing through a diffuser that is arranged in the rotor accommodating space and that circulates the fluid from the impellers radially outward of the rotating shaft, wherein a flow path of the volute is defined by the casing main body and the casing pieces. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, when a casing of a multi-stage centrifugal compressor is formed by casting, a flow path of a desired shape can be formed inside the casing while preventing an increase in the workload. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a partial cross-sectional view of a centrifugal compressor according to an embodiment. [Figure 2] 2 is an enlarged cross-sectional view showing the first volute of the casing and the surrounding structure as viewed from the radial direction of the rotary shaft in FIG. [Figure 3] 3 is an enlarged cross-sectional view showing the second volute of the casing and the surrounding structure as viewed from the radial direction of the rotary shaft in FIG. [Figure 4] 4 is an enlarged cross-sectional view showing the configuration of the third volute of the casing and its surroundings as viewed from the radial direction of the rotary shaft in FIG. [Figure 5] 5 is a partial cross-sectional view showing the first volute of the centrifugal compressor and the surrounding structure as seen from the axial direction of the rotary shaft in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a casing seen from the radial direction of the rotary shaft, showing a casing piece according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings. In the following, the term "axial direction" refers to the direction of the axis X of the rotation axis P of the rotor 3, and the term "radial direction" refers to the radial direction of the rotation axis P. In addition, the term "volute" in the following description will also be referred to as "scroll." (Embodiment) FIG. 1 is a partial cross-sectional view of a centrifugal compressor 1 according to a first embodiment. FIG. 1 shows a cross section of the centrifugal compressor 1 as seen from the radial direction of a rotation axis P. The centrifugal compressor 1 of this embodiment is, for example, a single-shaft multi-stage centrifugal compressor. The centrifugal compressor 1 of this embodiment compresses a fluid supplied from the outside by centrifugal force, discharges the fluid, and then supplies it to a predetermined nozzle. The fluid supplied to the centrifugal compressor 1 is, for example, a gas. An example of the gas is a hydrogen-containing gas. The type of fluid supplied to the centrifugal compressor 1 is not limited.

[0010] As will be described later, the centrifugal compressor 1 includes first to third diffusers C1 to C3 that compress the fluid that has passed through the first to sixth impellers I1 to I6 and cause the fluid to flow radially outward from the first to sixth impellers I1 to I6 about the rotary shaft P, and first to third volutes V1 to V3 that cause the fluid that has passed through the first to third diffusers C1 to C3 to flow around the axis of the rotor 3. The flow paths of the first to third volutes V1 to V3, which are part of the fluid flow path formed in the casing 2, are defined by the casing main body 20 and casing sections 21 to 23. In other words, the flow path shapes of the first to third volutes V1 to V3 are set by the surface shapes of the casing main body 20 and casing sections 21 to 23.

[0011] When the casing sections 21-23 are detached from the casing body 20, openings 20d-20f of the flow passages constituting the first to third volutes V1-V3 of the casing body 20 are enlarged. Therefore, with the casing sections 21-23 detached from the casing body 20, a tool can be easily inserted into the flow passages of the casing body 20 from the outside, and desired portions of the flow passages constituting the first to third volutes V1-V3 of the casing body 20 can be easily machined. Therefore, even when the casing body 20 is an integrally cast body and the flow passages inside the casing body 20 are shaped after the casing body 20 is manufactured, it is possible to form flow passages of the desired shape inside the casing 2 without increasing the workload.

[0012] As shown in FIG. 1, as a specific configuration example, a centrifugal compressor 1 includes a cylindrical casing 2 including a rotor accommodating space 2a, a rotor 3 rotatably supported in the rotor accommodating space 2a, and a diaphragm 4 disposed in the rotor accommodating space 2a, surrounding the rotor 3, and including a stationary flow path for a fluid.

[0013] The casing 2 also includes first to third volutes V1 to V3. The diaphragm 4 includes first to third diffusers C1 to C3. The first to third volutes V1 to V3 are arranged spaced apart in the direction of the axis X. The first to third diffusers C1 to C3 are arranged spaced apart in the direction of the axis X. The first to third diffusers C1 to C3 are arranged in the rotor accommodating space 2a. The first to third diffusers C1 to C3 may have a plurality of ribs that guide the fluid. In this case, each rib may extend radially of the rotation axis P.

[0014] The casing 2 includes a first inlet F1, a second inlet F2, and a third inlet F3 that introduce fluid into the diaphragm 4. The casing 2 also includes a first outlet E1, a second outlet E2, and a third outlet E3 that discharge gas that has passed through a first volute V1, a second volute V2, and a third volute V3, which will be described later.

[0015] The rotor 3 includes a rotation axis P, which is a rotor shaft, and a plurality of impellers I1 to I6 arranged on the rotation axis P. The centrifugal compressor 1 of this embodiment includes, as an example, a single rotation axis P. The plurality of impellers I1 to I6 are arranged on the rotation axis P and are rotationally driven around an axis X of the rotation axis P. The plurality of impellers I1 to I6 are arranged at intervals in the direction of the axis X. When the centrifugal compressor 1 is operating, the rotational driving force of the rotation axis P is transmitted to the plurality of impellers I1 to I6. As an example, the rotor 3 includes first to sixth impellers I1 to I6 arranged in this order from the front to the rear of the centrifugal compressor 1. The number of impellers is not limited as long as it is two or more. Furthermore, the number of volutes is not limited.

[0016] The diaphragm 4 includes flow paths S1, S2, and S3 as stationary flow paths of the centrifugal compressor 1 that guide the fluid to the multiple impellers I1 to I6. In this embodiment, the flow paths S1 to S3 partially include the flow paths of the diffusers C1 to C3. In the flow path S1, the fluid introduced through the first inlet F1 of the casing 2 is guided sequentially to the first impeller I1 and the second impeller I2, and then to the first diffuser C1. In the flow path S2, the fluid introduced through the second inlet F2 of the casing 2 is guided sequentially to the sixth impeller I6 and the fifth impeller I5, and then to the second diffuser C2. In the flow path S3, the fluid introduced through the third inlet F3 of the casing 2 is guided sequentially to the fourth impeller I4 and the third impeller I3, and then to the third diffuser C3. The diaphragm 4 may include multiple diaphragm pieces arranged side by side in the direction of the axis X.

[0017] The centrifugal compressor 1 further includes, as an example, at least one gas seal 51, 52 arranged on the axis X of the rotating shaft P to prevent fluid leakage from the flow paths S1 to S3 of the diaphragm 4, and a plurality of bearings B that support the rotating shaft P.

[0018] The casing 2 is a casing of the centrifugal compressor 1, which is a multi-stage centrifugal compressor, and houses the rotor 3 and the diaphragm 4. The casing 2 is a cylindrical body extending in the direction of the axis X, with the axis X being the cylindrical axis direction. The casing 2 includes a casing main body 20 and at least one casing section 21-23. The casing main body 20 includes a rotor accommodating space 2a extending in the direction of the axis X of the rotation shaft P. The casing main body 20 is an integral casting. The term "integral casting" used here refers to a casting in which at least the portions of the casing main body 20 exposed to the flow paths of the volutes V1-V3 are integrally continuous. The casing sections 21-23 are detachably attached to the casing main body 20.

[0019] The casing 2 also includes volutes V1-V3 that circulate the fluid that has passed through the diffusers C1-C3 around the axis X. The volutes V1-V3 have a spiral flow path whose outer diameter increases from the upstream side to the downstream side in the direction of the fluid flow when viewed from the direction of the axis X (see FIG. 5). The volutes also have connection regions D1-D3 that are connected to the diffusers C1-C3. Each volute V1-V3 has a maximum flow path cross-section that is larger than the maximum flow path cross-section of the connection regions D1-D3 that are directly connected to the volute V1-V3.

[0020] In the centrifugal compressor 1 of this embodiment, the flow paths of the volutes V1 to V3 are defined by the casing body 20 and the casing sections 21 to 23. As an example, the flow paths of the connection regions D1 to D3 are defined by the casing body 20 and the casing section 21.

[0021] As shown in FIG. 1, the casing body 20 includes an inner wall 20a that defines the shape of the rotor accommodating space 2a. The casing sections 21 to 23 are plate bodies and are attached by fastening members 50 arranged on the inner wall 20a. As an example, the fastening members 50 are bolts, and the casing body 20 has tapped holes that engage with the threads of the bolts. The type of fastening members 50 is not limited thereto. When the casing sections 21 to 23 are attached to the casing body 20, there are no significant steps between the surfaces of the casing body 20 and the casing sections 21 to 23 that are exposed to the rotor accommodating space 2a of the casing body 20. Therefore, attaching the casing sections 21 to 23 to the casing body 20 does not affect the shapes of the flow paths S1 to S3 included in the diaphragm 4.

[0022] Fig. 2 is an enlarged cross-sectional view showing the first volute V1 of the casing 2 and the surrounding configuration as viewed from the radial direction of the rotating shaft P in Fig. 1. Fig. 3 is an enlarged cross-sectional view showing the second volute V2 of the casing 2 and the surrounding configuration as viewed from the radial direction of the rotating shaft P in Fig. 1. Fig. 4 is an enlarged cross-sectional view showing the third volute V3 of the casing 2 and the surrounding configuration as viewed from the radial direction of the rotating shaft P in Fig. 1. Fig. 2 shows a cross section passing through the counterbore 21c of the casing section 21, and shows a schematic appearance of the fastening member 50.

[0023] As shown in Figure 2, the casing body 20 includes a curved inner wall 20b that defines a portion of the flow path of the first volute V1. The surface of the inner wall 20b of the casing body 20 is exposed within the first volute V1, along with the first surface 21a of the casing section 21. The casing section 21 includes a counterbore 21c that accommodates the head 50a of the fastening member 50, which is a bolt, so that the head 50a does not protrude into the rotor accommodating space 2a. The counterbore 21c is located on a second surface 21b of the casing section 21 that is located opposite the first surface 21a. The casing sections 22 and 23 have a structure similar to that of the casing section 21.

[0024] When the casing sections 21-23 are removed from the casing body 20, the sizes of the openings 20d-20f in the spaces forming the volutes V1-V3 of the casing body 20 are enlarged. Therefore, when the casing sections 21-23 are removed from the casing body 20, tools and the like can be easily inserted from the outside into the spaces in the casing body 20 through the openings 20d-20f. In this manner, the surfaces of the casing body 20 and the casing sections 21-23 are exposed to the flow paths of the volutes V1-V3. Furthermore, in this embodiment, the surfaces of the casing body 20 and the casing sections 21-23 are exposed to the flow paths of the connection regions D1-D3.

[0025] As shown in Fig. 2, of the multiple volutes V1 to V3 included in the centrifugal compressor 1 of this embodiment, the first volute V1 has the largest maximum flow path cross-sectional area. As shown in Fig. 3, the second volute V2 has a maximum flow path cross-sectional area that is smaller than the maximum flow path cross-sectional area of ​​the first volute V1 and larger than the maximum flow path cross-sectional area of ​​the third volute V3. As shown in Fig. 4, of the multiple volutes V1 to V3 included in the centrifugal compressor 1, the third volute V3 has the smallest maximum flow path cross-sectional area. As a result, for example, the flow velocity of the fluid increases as the fluid flows through the volutes V1 to V3 of the centrifugal compressor 1 in order. By setting the maximum flow path cross-sectional areas of the volutes V1 to V3 in this way, the compression efficiency of the fluid by the centrifugal compressor 1 is optimized.

[0026] FIG. 5 is a partial cross-sectional view showing the first volute V1 of the centrifugal compressor 1 and its surrounding configuration as seen from the direction of the axis X of the rotating shaft P in FIG. 1. As shown in FIG. 5, the inner wall 20a of the casing 2 has a circular surface that defines a flow path in the cylindrical rotor accommodating space 2a. The first surface 21a of the casing section 21 is a curved surface that extends in the circumferential direction of the rotating shaft P in accordance with the shape of the inner wall of the casing 2. In the centrifugal compressor 1, as an example, multiple casing sections 21 are arranged side by side in the circumferential direction of the inner wall 20a of the casing 2 to define a part of the flow path of the volute V1. As shown in FIG. 5, multiple casing sections 21 may be arranged corresponding to one volute V1. In the centrifugal compressor 1, the casing sections 22 and 23 are also arranged in the same manner as the casing sections 21.

[0027] Here, the centrifugal compressor 1 includes multiple compression sections, each including a pair of an inlet and an outlet. The centrifugal compressor 1 compresses the fluid in stages by introducing a fluid compressed in one compression section into another compression section and further compressing the fluid. As shown in FIG. 1 , the centrifugal compressor 1 includes, for example, a first compression section 10, a second compression section 11, and a third compression section 12 aligned along the axial line X. The first compression section 10 includes a first inlet F1 and a first outlet E1. The second compression section 11 includes a second inlet F2 and a second outlet E2. The third compression section 12 includes a third inlet F3 and a third outlet E3. As shown in FIG. 1 , the centrifugal compressor 1 of this embodiment includes, for example, the third compression section 12 disposed between the first compression section 10 and the second compression section 11 along the axial line X.

[0028] When the centrifugal compressor 1 having the above configuration is operating, the rotor 3 is rotationally driven in the rotor accommodating space 2a, and a fluid is introduced into the centrifugal compressor 1 from the first inlet F1 of the casing 2. The fluid is compressed by the first impeller I1 and the second impeller I2 while flowing through the flow path S1. The fluid then passes through the first diffuser C1 and is introduced into the first volute V1 via the connection region D1. The fluid is guided by the first volute V1, flows in the circumferential direction of the rotor 3, and is discharged from the first outlet E1 of the casing 2. In this manner, the fluid is compressed in the first compression section 10 of the centrifugal compressor 1.

[0029] The fluid then flows through piping provided outside the centrifugal compressor 1 and is introduced back into the centrifugal compressor 1 from the second inlet F2 of the casing 2. The fluid is further compressed by the sixth impeller I6 and the fifth impeller I5 while flowing through the flow path S2. The fluid then passes through the second diffuser C2 and is introduced into the second volute V2 via the connection region D2. The fluid is guided by the second volute V2, flows in the circumferential direction of the rotor 3, and is discharged from the second outlet E2 of the casing 2. In this way, the fluid is compressed in the second compression section 11 of the centrifugal compressor 1.

[0030] The fluid then flows through piping provided outside the centrifugal compressor 1, and is again introduced into the centrifugal compressor 1 from the third inlet F3 of the casing 2. The fluid is further compressed by the fourth impeller I4 and the third impeller I3 while flowing through the flow path S3. The fluid then passes through the third diffuser C3 and is introduced into the third volute V3 via the connection region D3. The fluid is guided by the third volute V3, flows in the circumferential direction of the rotor 3, and is discharged from the third outlet E3 of the casing 2. This completes the compression of the fluid in the third stage, which is the final stage of the centrifugal compressor 1. The compressed fluid discharged from the third outlet E3 is supplied, for example, to a nozzle arranged outside the centrifugal compressor 1.

[0031] As described above, according to this embodiment, the flow paths of the volutes V1 to V3 are defined by the casing body 20 and the casing sections 21 to 23. Therefore, when manufacturing the centrifugal compressor 1, in a state in which the casing sections 21 to 23 are detached from the casing body 20, a tool can be easily inserted from the outside into the flow paths inside the casing body 20, and the casing body 20 can be easily machined with the tool. Therefore, even if the casing body 20 is an integrally cast body, it is possible to form flow paths of a desired shape inside the casing 2 by shaping the casing body 20 while preventing an increase in the workload.

[0032] As shown in FIG. 1, in the centrifugal compressor 1, which is a multi-stage centrifugal compressor, volutes V1 to V3 are arranged inside the casing 2, which is located toward the center of the rotation axis P in the direction of the axis X. Conventionally, volutes arranged in such positions are difficult to reach with a tool from outside the casing. Therefore, it may be extremely difficult to insert a tool from outside the casing into the inside and process the desired processing position. Even in such cases, according to this embodiment, by removing the casing pieces 21 to 23 from the casing main body 20, it is possible to easily insert a tool into the processing position. Therefore, a flow path of the desired shape can be formed inside the casing 2 while preventing an increase in the workload.

[0033] Here, when the fluid supplied to the centrifugal compressor 1 is a hydrogen-containing gas, as in this embodiment, the flow velocity of the fluid inside the centrifugal compressor 1 is relatively high. Therefore, if the shape of the flow passage inside the casing is inappropriate, the flow of the fluid may be disturbed, and the compression efficiency may decrease. In contrast, according to this embodiment, by combining the casing main body 20 and the casing sections 21 to 23, the flow passages of the volutes V1 to V3 can be set to the desired shape, making it easy to manufacture an appropriately aerodynamically designed centrifugal compressor 1. Therefore, even when the fluid introduced into the centrifugal compressor 1 is a hydrogen-containing gas, it is possible to prevent a decrease in the compression efficiency of the centrifugal compressor 1. As a result, it is possible to ensure the aerodynamic performance of the centrifugal compressor 1 while improving manufacturing efficiency.

[0034] In this embodiment, the flow paths of the connection regions D1-D3 connecting the volutes V1-V3 to the diffusers C1-C3 are defined by the casing body 20 and the casing sections 21-23. Typically, the cross-sectional area of ​​the connection regions connecting the volutes to the diffuser flow paths is relatively small. For this reason, it may be difficult to machine the volutes from the outside of the cast casing. In contrast, in this embodiment, the flow paths of the connection regions D1-D3 are defined by the casing body 20 and the casing sections 21-23. Therefore, when the casing sections 21-23 are removed from the casing body 20, the interior of the casing body 20 can be easily accessed from the outside. Therefore, even when the casing body 20 is formed as, for example, an integral casting, the volutes V1-V3 can be easily machined from the outside of the cast casing body 20. Therefore, flow paths of a desired shape, including the volutes V1-V3, can be formed inside the casing 2.

[0035] Furthermore, in this embodiment, when the casing sections 21-23 are attached to the casing body 20, the maximum flow path cross-sectional area of ​​the connection region D1 is smaller than that of the volute V1, the maximum flow path cross-sectional area of ​​the connection region D2 is smaller than that of the volute V2, and the maximum flow path cross-sectional area of ​​the connection region D3 is smaller than that of the volute V3. Even in such a case, in this embodiment, when the casing sections 21-23 are removed from the casing body 20, the interior of the casing body 20 can be easily accessed from the outside, making it easy to form the flow paths of the volutes V1-V3 into the desired shape.

[0036] Furthermore, in this embodiment, the casing body 20 includes an inner wall 20a that defines the shape of the rotor accommodating space 2a, and the casing sections 21 to 23 are detachably attached to the inner wall 20a, for example, by fastening members 50. With this configuration, the casing sections 21 to 23 can be easily attached to the inner wall 20a of the casing body 20 using the fastening members 50. Therefore, even when attaching multiple casing sections 21 to 23 to multiple locations on the casing body 20, for example, work efficiency can be improved.

[0037] Once attached, the casing sections 21 to 23 can be easily replaced. Furthermore, by attaching casing sections 21 to 23 of different shapes to the casing body 20, the flow path shapes of the volutes V1 to V3 and diffusers C1 to C3 can be easily adjusted.

[0038] Furthermore, the centrifugal compressor 1 of this embodiment is equipped with a diaphragm 4 that is accommodated in the rotor accommodating space 2a and allows fluid to circulate among the multiple impellers I1 to I6, the casing body 20 includes an inner wall 20a that defines the shape of the rotor accommodating space 2a, and the casing sections 21 to 23 are attached to the inner wall 20a between the casing body 20 and the diaphragm 4 in the radial direction of the rotation axis P. This allows the casing sections 21 to 23 to be attached to the inner wall 20a between the casing body 20 and the diaphragm 4 in the radial direction of the rotation axis P. This allows the casing sections 21 to 23 to be stably arranged. Below, modifications of the present disclosure will be described, focusing on the differences from the embodiment.

[0039] (Variation) FIG. 6 is an enlarged cross-sectional view of the casing 2, seen from the radial direction of the rotation axis P, showing a casing section 24 according to a modified example. In FIG. 6, the contour L1 of the casing body 20, which defines the cross section of the volute V1 on the upstream side in the fluid flow direction, is shown by a solid line, and contours L2 to L11 of the casing body 20, which define the cross section of the volute V1 at multiple locations on the downstream side in the fluid flow direction, are shown by two-dot chain lines. The contours L1 to L11, in the same order, schematically represent partial contours of the casing body 20 at multiple locations located from the upstream side to the downstream side in the fluid flow direction of the volute V1. As shown in FIG. 6, the casing section 24 of this modified example includes a first surface 24a that defines a portion of the flow path of the volute V1. The first surface 24a has a shape that smoothly connects with the surface of the inner wall 20b of the casing body 20, which defines the remaining portion of the flow path of the volute V1. There is no step that would affect the flow of fluid at the boundary between first surface 24a of casing section 24 and the surface of inner wall 20b. As shown by contour lines L1 to L11, the flow path cross section of volute V1 increases from the upstream side to the downstream side in the direction of fluid flow. As shown by these contour lines L1 to L11, there is no step that would affect the flow of fluid at the boundary between first surface 24a of casing section 24 and the surface of inner wall 20b at any position in the flow path cross section of volute V1.

[0040] In this way, if the surfaces of the casing body 20 and the casing section 24 that define the cross-sectional shape of the volute V1 when viewed from the radial direction of the rotation axis P have smoothly curved shapes, the fluid that has passed through the diffuser C1 and the connection region D1 can be efficiently collected in the volute V1 and easily guided to the nozzle. Note that although the casing section 24 in Figure 6 is arranged to correspond to the first volute V1, it may also be arranged to correspond to the other volutes V2 and V3.

[0041] This modification also makes it possible to form flow paths of a desired shape inside the casing 2 when forming the casing 2 of the centrifugal compressor 1 by casting, while preventing an increase in the workload. Furthermore, the casing section 24 further improves the design freedom of the flow paths of the volutes V1 to V3, thereby further smoothing the flow of gas inside the volutes V1 to V3.

[0042] (Disclosure items) Each of the following sections is a disclosure of a preferred embodiment. [Item 1] A casing for a multi-stage centrifugal compressor that houses a rotor including a rotating shaft and a plurality of impellers that are arranged on the rotating shaft and are driven to rotate around an axis of the rotating shaft, a casing body that includes a rotor accommodating space and is an integral casting; a casing piece detachably attached to the casing body; a volute that is disposed in the rotor accommodating space and causes the fluid that has passed through a diffuser that causes the fluid to flow from the impeller radially outwardly of the rotary shaft to flow around the axis of the rotor, A casing for a multi-stage centrifugal compressor, wherein the flow path of the volute is defined by the casing body and the casing section.

[0043] According to the above configuration, the flow path of the volute is defined by the casing body and the casing sections. Therefore, when the casing sections are detached from the casing body, a tool can be easily inserted from the outside into the flow path inside the casing body, and the casing body can be easily machined. Therefore, even if the casing body is a one-piece cast body, an increase in the workload can be prevented and a flow path of the desired shape can be formed inside the casing.

[0044] Furthermore, in a multi-stage centrifugal compressor, the volute is disposed inside the casing located toward the center of the rotating shaft in the axial direction, and it may be difficult to process the casing portion that defines the volute flow path from the outside of the casing. Even in such cases, by defining the volute flow path with the casing main body and the casing pieces, it is possible to form a flow path of the desired shape inside the casing.

[0045] [Item 2] Item 2. A casing for a multi-stage centrifugal compressor according to item 1, wherein a flow path in a connection region of the volute connected to the diffuser is defined by the casing body and the casing piece.

[0046] Typically, the cross-sectional area of ​​the volute connection region where it connects to the flow path of the diffuser is relatively small, and it can be difficult to machine the volute from the outside of the cast casing. In contrast, with the above-described configuration, the flow path in the connection region is defined by the casing body and the casing pieces. Therefore, when the casing pieces are removed from the casing body, the interior of the casing body can be easily accessed from the outside. Therefore, even when the casing body is constructed as, for example, an integral casting, the volute can be easily machined from the outside of the cast casing body. This makes it possible to form a flow path of the desired shape, including the volute, inside the casing.

[0047] [Item 3] 3. The casing of a multi-stage centrifugal compressor according to item 2, wherein, in a state in which the casing piece is attached to the casing body, a maximum flow path cross-sectional area of ​​the connection region is smaller than a maximum flow path cross-sectional area of ​​the volute.

[0048] According to the above configuration, even if the maximum flow path cross-sectional area of ​​the connection region is smaller than the maximum flow path cross-sectional area of ​​the volute, when the casing piece is removed from the casing body, the inside of the casing body can be easily accessed from the outside, making it easy to form the flow path of the volute into the desired shape.

[0049] [Item 4] the casing body includes an inner wall that defines the shape of the rotor accommodating space, 4. The casing for a multi-stage centrifugal compressor according to any one of items 1 to 3, wherein the casing piece is detachably attached to the inner wall.

[0050] According to the above configuration, the casing pieces can be easily attached to the inner wall of the casing main body using the fastening members. This improves the efficiency of attaching multiple casing pieces to multiple locations on the casing main body, and also makes it easy to replace the casing pieces.

[0051] [Item 5] a rotor including a rotating shaft and a plurality of impellers disposed on the rotating shaft and driven to rotate about an axis of the rotating shaft; a diffuser disposed in the rotor accommodating space and allowing air to flow from the impeller radially outwardly of the rotary shaft; A multi-stage centrifugal compressor comprising the casing according to any one of items 1 to 4.

[0052] According to the above configuration, the flow path of the volute is defined by the casing body and the casing sections. Therefore, even when the casing body is formed as, for example, an integral casting, the shape of the flow path of the volute can be prevented from being restricted by the shape of the casting mold. As a result, a multi-stage centrifugal compressor can be obtained in which a flow path of a desired shape is formed inside the casing.

[0053] [Item 6] a diaphragm accommodated in the rotor accommodating space and allowing the fluid to flow between the plurality of impellers; the casing body includes an inner wall that defines the shape of the rotor accommodating space, 6. The multi-stage centrifugal compressor according to item 5, wherein the casing piece is attached to the inner wall between the casing body and the diaphragm in the radial direction of the rotation shaft.

[0054] According to the above configuration, the casing piece is attached to the inner wall between the casing body and the diaphragm in the radial direction of the rotation shaft, thereby preventing interference between the casing piece and the diaphragm and enabling stable positioning of the casing piece.

[0055] As described above, the above embodiment and the above modified examples have been described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited to these and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above embodiment and the modified examples can be combined to create new embodiments. For example, some configurations in one embodiment may be applied to other configurations, and some configurations in one embodiment can be separated and arbitrarily extracted from other configurations in that embodiment. Furthermore, the components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem, and are used to illustrate the technology.

[0056] The diaphragm 4 may include multiple diaphragm pieces. In this case, the multiple diaphragm pieces are arranged, for example, in the direction of the axis X. The rotating shaft P may also include multiple shafts. In other words, the centrifugal compressor 1 does not have to be a single-shaft type. In this case, for example, the multiple shafts may be meshed with each other and connected together. Furthermore, when multiple casing sections 21-24 are arranged corresponding to one volute V1-V3, the casing sections 21-24 may be arranged overlapping each other in the radial direction of the rotating shaft. This makes it easier to set the flow path shape of the volutes V1-V3 using the multiple casing sections 21-24, and simplifies the shape of the casing sections 21-24, making it easier to manufacture the casing sections 21-24. [Explanation of symbols]

[0057] C1~C3 Diffuser D1~D3 Connection area where the volute is connected to the diffuser I1~I6 impellers P rotation axis V1~V3 Volute (Scroll) 1. Centrifugal compressor 2 Casing 2a Rotor housing space 3 rotors 20 Casing body 20a Inner wall of casing body 21~23 Casing pieces

Claims

1. A casing for a multi-stage centrifugal compressor that houses a rotor including a rotating shaft and a plurality of impellers that are arranged on the rotating shaft and are driven to rotate around an axis of the rotating shaft, a casing body that includes a rotor accommodating space and is an integral casting; a casing piece detachably attached to the casing body; a volute that is disposed in the rotor accommodating space and causes the fluid that has passed through a diffuser that causes the fluid to flow from the impeller radially outwardly of the rotary shaft to flow around the axis of the rotor, A casing for a multi-stage centrifugal compressor, wherein the flow path of the volute is defined by the casing body and the casing section.

2. 2. A casing for a multi-stage centrifugal compressor according to claim 1, wherein a flow path in a connection region of said volute connected to said diffuser is defined by said casing body and said casing section.

3. 3. The casing for a multi-stage centrifugal compressor according to claim 2, wherein, in a state in which the casing section is attached to the casing body, a maximum flow passage cross-sectional area of ​​the connection region is smaller than a maximum flow passage cross-sectional area of ​​the volute.

4. the casing body includes an inner wall that defines the shape of the rotor accommodating space, 2. The casing of a multi-stage centrifugal compressor according to claim 1, wherein said casing section is removably attached to said inner wall.

5. a rotor including a rotating shaft and a plurality of impellers disposed on the rotating shaft and driven to rotate about an axis of the rotating shaft; a diffuser disposed in the rotor accommodating space and allowing air to flow from the impeller radially outwardly of the rotary shaft; A multi-stage centrifugal compressor comprising: a casing according to claim 1.

6. a diaphragm accommodated in the rotor accommodating space and allowing the fluid to flow between the plurality of impellers; the casing body includes an inner wall that defines the shape of the rotor accommodating space, The multi-stage centrifugal compressor according to claim 5 , wherein the casing piece is attached to the inner wall between the casing body and the diaphragm in the radial direction of the rotary shaft.

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