Centrifugal compressor

Abstract

The discharge scroll is formed compactly while suppressing flow separation when the working fluid enters. [Solution] The centrifugal compressor comprises a rotating shaft and a casing having an inlet and a discharge port. The rotating shaft has an impeller. The casing has a diaphragm, an outer casing covering the diaphragm, a diffuser passage for guiding the working fluid, and a discharge scroll for guiding the working fluid discharged from the impeller to the discharge port, and has a plurality of compression sections. The discharge scroll is connected radially outward to the diffuser passage and positioned radially inward to the outer casing, extending circumferentially around its central axis, with a constant radial spacing when viewed from the axial direction, and the axial spacing gradually narrows as it moves away from the discharge port in the circumferential direction. The outer casing is formed in a circular shape with a constant radial inner diameter at the position where it overlaps with the discharge scroll in the axial direction.

Description

Technical Field

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

Background Art

[0002] As a type of centrifugal rotating machine, a multistage centrifugal compressor having a plurality of stages of impellers for compressing gas is known. The multistage centrifugal compressor successively compresses the gas sucked into the casing from the suction port with a plurality of stages of impellers and discharges it out of the casing from the discharge port. A discharge scroll is connected to the discharge port to keep the flow velocity of the gas discharged from the impeller through the diffuser flow path constant and reduce the pressure loss.

[0003] For example, Patent Document 1 describes a discharge volute (discharge scroll) formed such that the radial interval gradually widens as it goes downstream in the gas flow direction in the circumferential direction. This discharge volute is formed by fixing a volute piece whose radial wall thickness dimension gradually decreases to the casing as it goes downstream in the gas flow direction in the circumferential direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when forming a discharge scroll, it can be formed in a shape that changes the flow direction of the working fluid, such as gas discharged radially outward from the diffuser flow path, so that it flows radially inward before entering, or in a shape that allows it to flow in without changing its flow direction. In a discharge scroll with a shape that changes the flow direction before entering, separation is likely to occur when the working fluid flows into the discharge scroll. On the other hand, in a discharge scroll with a shape that allows it to flow in without changing its flow direction, the discharge scroll is formed radially outward relative to the diffuser flow path, resulting in an excessively large outer diameter for a centrifugal compressor. There is a need to form a compact discharge scroll while suppressing flow separation when the working fluid enters.

[0006] This disclosure was made to solve the above problems and aims to provide a centrifugal compressor that can form a compact discharge scroll while suppressing flow separation when the working fluid flows in. [Means for solving the problem]

[0007] To solve the above problems, the centrifugal compressor according to the present disclosure comprises a rotating shaft extending in the axial direction over which a central axis extends, and a casing having an intake port formed on the first side in the axial direction and an outlet port formed on the second side in the axial direction, wherein the rotating shaft has an impeller disposed within the casing that compresses and discharges a working fluid supplied from the first side in the axial direction radially outward with respect to the central axis, the casing comprises a diaphragm formed in the axial direction so as to cover the impeller and a cylindrical outer casing formed in the axial direction so as to cover the diaphragm, a diffuser passage that guides the working fluid discharged from the impeller toward the radially outward direction, and the working fluid discharged from the impeller The device has a discharge scroll that leads to a discharge port, and has a plurality of compression sections for compressing the working fluid at different pressures, each compression section having an inlet, a discharge port, a plurality of impellers, a plurality of diaphragms, a diffuser passage, and a discharge scroll, each discharge scroll being connected radially outward to the corresponding diffuser passage, positioned radially inward to the outer casing, extending circumferentially about the central axis, with a constant radial spacing when viewed from the axial direction, and the axial spacing gradually narrowing as it moves away from the discharge port in the circumferential direction, and the outer casing being formed in a circular shape with a constant radial inner diameter at the position where it overlaps with the discharge scroll in the axial direction. [Effects of the Invention]

[0008] According to the centrifugal compressor of this disclosure, it is possible to form a compact discharge scroll while suppressing flow separation when the working fluid is introduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of a centrifugal compressor according to an embodiment of the present disclosure. [Figure 2] This is a cross-sectional view of the centrifugal compressor described above, but at a different cross-section than that shown in Figure 1. [Figure 3]This is a cross-sectional view taken along line III-III in Figure 1, showing the discharge scroll of the centrifugal compressor described above, viewed from the axial direction. [Figure 4] This is a magnified view of the main part at IV-IV in Figure 3, showing the change in the axial width of the discharge scroll of the centrifugal compressor described above. [Figure 5] Figure 3 is a magnified view of the main part at VV, showing the change in the axial width of the discharge scroll of the centrifugal compressor described above. [Figure 6] This is a magnified view of the main part at VI-VI in Figure 3, showing the change in the axial width of the discharge scroll of the centrifugal compressor described above. [Figure 7] Figure 3, section VII-VII, is a magnified view of the main part showing the change in the axial width of the discharge scroll of the centrifugal compressor described above. [Modes for carrying out the invention]

[0010] The following describes embodiments for implementing the centrifugal compressor according to the present invention with reference to the attached drawings. However, the present invention is not limited to these embodiments.

[0011] (Configuration of a centrifugal compressor) As shown in Figure 1, the centrifugal compressor 1 in this embodiment is a single-shaft multi-stage centrifugal compressor. The centrifugal compressor 1 mainly comprises a rotating shaft 2 that rotates around a central axis O, and a casing 10 formed to surround the rotating shaft 2.

[0012] (Configuration of the rotation axis) The rotating shaft 2 extends in the axial direction Da. The rotating shaft 2 extends through the inside of the casing 10 along the central axis O. The rotating shaft 2 has a rotating shaft body 21 and an impeller 22.

[0013] In this embodiment, the direction in which the central axis O extends is defined as the axial direction Da. The axial direction Da of the rotation axis 2 lies along the horizontal plane. That is, the central axis O extends horizontally. The radial direction relative to the central axis O is simply defined as the radial direction Dr. The direction around the rotation axis 2 centered on the central axis O is defined as the circumferential direction Dc. Figure 1 shows a cross-sectional view of the axial direction Da and the vertical direction Dv. The direction intersecting the axial direction Da and the vertical direction Dv is sometimes referred to as the horizontal direction.

[0014] The rotating shaft body 21 is formed in a cylindrical shape extending in the axial direction Da. The first end Da1 of the rotating shaft body 21 in the axial direction Da is supported by the casing 10 so as to be rotatable around the central axis O by a journal bearing 32A and a thrust bearing 31. The second end Da2 of the rotating shaft body 21 in the axial direction Da is supported by the casing 10 so as to be rotatable around the central axis O by a journal bearing 32B.

[0015] The impeller 22 is positioned on the outer side Dro in the radial direction Dr with respect to the central axis O relative to the rotating shaft body 21. Multiple impellers 22 are arranged spaced apart in the axial direction Da within the casing 10. In this embodiment, for example, six impellers 22 are arranged spaced apart in the axial direction Da. These impellers 22 constitute two sets of three-stage impeller groups (first impeller group 22A and second impeller group 22B) facing opposite directions in the axial direction Da. As a result, the centrifugal compressor 1 of this embodiment is a so-called back-to-back single-shaft multi-stage centrifugal compressor. The centrifugal compressor 1 has a first compression section 20A having the first impeller group 22A and a second compression section 20B having the second impeller group 22B. In the centrifugal compressor 1, the working fluid compressed in the first compression section 20A is further compressed in the second compression section 20B. In other words, each compression section compresses working fluid at different pressures. The first compression section 20A compresses the working fluid by circulating it from the first side Da1 to the second side Da2 in the axial direction Da. The second compression section 20B further compresses the working fluid compressed in the first compression section 20A. The second compression section 20B compresses the working fluid by circulating it from the second side Da2 to the first side Da1 in the axial direction Da. In other words, the second compression section 20B compresses the working fluid by circulating it in the opposite direction to the first compression section 20A in the axial direction Da.

[0016] Each impeller 22 compresses and discharges working fluid (e.g., gas) supplied from the first side Da1 in the axial direction Da to the outer side Dro in the radial direction Dr. Each impeller 22 has an impeller flow path 23 formed inside. The cross-sectional area of ​​the impeller flow path 23 gradually decreases from the inner side Dri in the radial direction Dr to the outer side Dro in the radial direction Dr. As a result, the working fluid flowing through the impeller flow path 23 while the impeller 22 is rotating is gradually compressed and becomes high pressure. Each impeller 22 may be a closed impeller with a cover or an open impeller without a cover.

[0017] (Casing configuration) The casing 10 is formed to surround the rotary shaft body 21 and the plurality of impellers 22 from the outside Dro in the radial direction Dr. The casing 10 includes an outer casing 11, a suction port 111, a discharge port 112, an intermediate suction port 113, an intermediate discharge port 114, a plurality of diaphragms 15, and an intermediate partition plate 16.

[0018] The outer casing 11 is formed in a cylindrical shape extending in the axial direction Da. The outer casing 11 is formed to cover the rotary shaft 2 and the plurality of diaphragms 15 from the outside Dro in the radial direction Dr. The outer casing 11 forms a suction port 111, a discharge port 112, an intermediate suction port 113, and an intermediate discharge port 114. Further, the outer casing 11 has a first outer wall portion 12A, a second outer wall portion 12B, a first side wall portion 13A, a second side wall portion 13B, and a horizontal flange 17.

[0019] The first outer wall portion 12A and the second outer wall portion 12B are cylindrical portions extending in the axial direction Da. The first outer wall portion 12A covers, from the outside Dro in the radial direction Dr, a region that overlaps (corresponds to) the first compression portion 20A in the axial direction Da. The second outer wall portion 12B covers, from the outside Dro in the radial direction Dr, a region that overlaps (corresponds to) the second compression portion 20B in the axial direction Da.

[0020] The first outer wall portion 12A has a first inner peripheral surface 121 and a first outer peripheral surface 122. The first inner peripheral surface 121 faces the plurality of diaphragms 15 corresponding to the first compression portion 20A in the radial direction Dr. The first outer peripheral surface 122 forms the outer shape of the first outer wall portion 12A. The first inner peripheral surface 121 and the first outer peripheral surface 122 are formed in a perfect circular shape with a constant distance in the radial direction Dr from the central axis О over the axial direction Da.

[0021] The second outer wall portion 12B has a second inner peripheral surface 123 and a second outer peripheral surface 124. The second inner peripheral surface 123 faces the plurality of diaphragms 15 corresponding to the second compression portion 20B in the radial direction Dr. The second outer peripheral surface 124 forms the outer shape of the second outer wall portion 12B. The second inner peripheral surface 123 and the second outer peripheral surface 124 are formed in a perfect circular shape with a constant distance in the radial direction Dr from the central axis О over the axial direction Da.

[0022] The second outer wall portion 12B is formed with a smaller outer diameter than the first outer wall portion 12A. In other words, the second outer peripheral surface 124 is formed to be located radially inward Dri from the first outer peripheral surface 122. Note that bolt holes and horizontal flanges 17, which are appropriately formed in the first outer wall portion 12A and the second outer wall portion 12B, are not considered in their inner and outer diameters.

[0023] The first side wall portion 13A and the second side wall portion 13B are arranged to close the openings at both ends of the cylindrical first outer wall portion 12A and the second outer wall portion 12B in the axial direction Da. The first side wall portion 13A and the second side wall portion 13B are annular portions centered on the central axis O. The first side wall portion 13A covers the first outer wall portion 12A from the first side Da1 in the axial direction Da. That is, the first side wall portion 13A is connected to the end of the first side Da1 of the first outer wall portion 12A. The first side wall portion 13A is formed so as not to protrude radially outward Dr Dro from the first outer wall portion 12A when viewed from the axial direction Da. The second side wall portion 13B covers the second outer wall portion 12B from the second side Da2 in the axial direction Da. That is, the second side wall portion 13B is connected to the end of the second side Da2 of the second outer wall portion 12B. The second side wall portion 13B is formed so as not to protrude radially outward in the direction Dr beyond the second outer wall portion 12B when viewed from the axial direction Da.

[0024] The external casing 11 of this embodiment is formed to be separable into upper and lower sections in the vertical direction Dv. The horizontal flange 17 is formed to connect the upper and lower sections of the external casing 11. Figure 2 shows a cross-sectional view along the plane on which the external casing 11 is divided into upper and lower sections. The horizontal flange 17 is formed on both the upper and lower sections of the external casing 11. The horizontal flange 17 extends horizontally from the outer surface Dro in the radial direction Dr of the first outer wall section 12A and the second outer wall section 12B. The horizontal flange 17 also extends axially Da from the first side wall section 13A and the second side wall section 13B. Furthermore, the horizontal flange 17 also extends horizontally from the outer surface Dro in the radial direction Dr of the intermediate partition plate 16, which will be described later. The horizontal flange 17 has, for example, a plurality of through holes 17a that penetrate in the vertical direction Dv. The outer casing 11 is assembled by inserting bolts or the like through the through holes 17a and fixing the two halves of the outer casing 11 together while they are in contact with each other.

[0025] The suction port 111 is formed on the first side Da1 in the axial direction Da of the outer casing 11. The suction port 111 allows working fluid to flow into the outer casing 11 from the outside.

[0026] The intermediate discharge port 114 is formed near the center of the axial direction Da of the outer casing 11. The intermediate discharge port 114 is formed at a distance of Da2 on the second side of the axial direction Da from the suction port 111. The intermediate discharge port 114 is the discharge port in the first compression section 20A. The intermediate discharge port 114 is connected to the impeller 22 located at the second-to-last Da2 on the axial direction Da within the first compression section 20A. The intermediate discharge port 114 discharges the working fluid, which has been compressed within the outer casing 11 through the three impellers 22 of the first compression section 20A, to the outside of the outer casing 11.

[0027] The intermediate suction port 113 is formed on the second side Da2 in the axial direction Da of the outer casing 11. The intermediate suction port 113 is formed separately from the intermediate discharge port 114 on the second side Da2 in the axial direction Da. The intermediate suction port 113 is the suction port in the second compression section 20B. The intermediate suction port 113 is connected to the impeller 22 located on the second side Da2 in the axial direction Da within the second compression section 20B. The intermediate suction port 113 allows the working fluid discharged from the intermediate discharge port 114 through the three impellers 22 of the first compression section 20A within the outer casing 11 to flow into the impeller 22 of the second compression section 20B.

[0028] The discharge port 112 is formed near the center of the outer casing 11 in the axial direction Da. The discharge port 112 is formed at a distance of Da2 on the second side of the axial direction Da from the suction port 111. Also, the discharge port 112 is formed at a distance of Da1 on the first side of the axial direction Da from the intermediate suction port 113. The discharge port 112 is connected to the impeller 22 located at the first side Da1 in the axial direction Da within the second compression section 20B. Therefore, the discharge port 112 discharges the working fluid, which has been compressed through all the impellers 22 within the outer casing 11, to the outside of the outer casing 11.

[0029] Multiple diaphragms 15 are positioned on the inner side Dri of the radial Dr of the outer casing 11. The multiple diaphragms 15 are formed as a whole into a cylindrical shape extending in the axial direction Da so as to cover each stage of the impeller 22. Each diaphragm 15 is formed into a disc shape with a central axis O at its center. The multiple diaphragms 15 are stacked in the axial direction Da, and adjacent diaphragms 15 are fixed to each other by welding or bolts. The multiple diaphragms 15, fixed to each other, cover the circumference of the rotating shaft 2 and form a casing flow path 40 inside that connects the multiple impellers 22.

[0030] The multiple diaphragms 15 include a first diaphragm group 15A and a second diaphragm group 15B. The first diaphragm group 15A covers the first impeller group 22A. The first diaphragm group 15A is covered from the outside radially in the direction of Dr by a first outer wall portion 12A. The second diaphragm group 15B covers the second impeller group 22B. The second diaphragm group 15B is covered from the outside radially in the direction of Dr by a second outer wall portion 12B. Furthermore, the multiple diaphragms 15 have casing passages 40, which include an introduction passage 41, a diffuser passage 42, and a return passage 43. That is, the first compression section 20A and the second compression section 20B each have casing passages 40 formed therein.

[0031] The introduction channel 41 guides the working fluid from the outer Dro in the radial direction Dr towards the inner Dri in the radial direction Dr. The introduction channel 41 changes the flow of the working fluid, which is moving towards the inner Dri in the radial direction Dr, to a flow towards the second side Da2 in the axial direction Da, and guides it to the impeller 22. In this way, the introduction channel 41 changes the flow direction of the working fluid to the second side Da2 in the axial direction Da and guides it to the impeller channel 23 of the impeller 22.

[0032] The diffuser channel 42 extends from the inner Dri to the outer Dro in the radial direction Dr. The inner Dri end of the diffuser channel 42 in the radial direction Dr is in communication with the outer Dro end of the impeller channel 23 in the radial direction Dr. The diffuser channel 42 guides the working fluid compressed by the impeller 22 from the inner Dri in the radial direction Dr to the outer Dro in the radial direction Dr.

[0033] The return channel 43 reverses the flow direction of the working fluid that has flowed from the inner Dri in the radial direction Dr towards the outer Dro in the radial direction Dr via the diffuser channel 42. The return channel 43 guides the working fluid flowing towards the outer Dro in the radial direction Dr back to the inner Dri in the radial direction Dr. One end of the return channel 43 (the first side Da1 in the axial direction Da), which is upstream in the flow direction of the working fluid, is in communication with the diffuser channel 42. The other end of the return channel 43 (the second side Da2 in the axial direction Da), which is downstream in the flow direction of the working fluid, is in communication with the next inlet channel 41.

[0034] Furthermore, in this embodiment, the casing flow path 40 has different radial dimensions (Dr) for each diaphragm 15 in each diaphragm group. In the first diaphragm group 15A, the casing flow path 40 decreases in the radial direction (Dr) as you move from the suction port 111 to the intermediate discharge port 114. Specifically, in the first diaphragm group 15A, the return flow path 43 is positioned on the inner side of the radial direction (Dr) as you move from the suction port 111 to the intermediate discharge port 114. The second diaphragm group 15B is similar to the first diaphragm group 15A. In the second diaphragm group 15B, the casing flow path 40 decreases in the radial direction (Dr) as you move from the intermediate suction port 113 to the discharge port 112. Note that the casing flow path 40 is not limited to these configurations.

[0035] The intermediate partition plate 16 is positioned to separate the first compression section 20A and the second compression section 20B. The intermediate partition plate 16 is positioned between the first diaphragm group 15A and the second diaphragm group 15B in the axial direction Da. The intermediate partition plate 16 covers the rotating shaft body 21. In this embodiment, the outer diameter of the intermediate partition plate 16 in the radial direction Dr is larger than the outer diameter of the first outer wall portion 12A. However, the embodiment is not limited to this. For example, the outer diameter of the intermediate partition plate 16 in the radial direction Dr may be the same as the outer diameter of the first outer wall portion 12A. The intermediate partition plate 16 has a first surface 16a facing the first side Da1 in the axial direction Da, and a second surface 16b facing the second side Da2. That is, the intermediate partition plate 16 faces the first diaphragm group 15A with its first surface 16a and faces the second diaphragm group 15B with its second surface 16b. Furthermore, the intermediate partition plate 16 is fixed to the first outer wall portion 12A on its first surface 16a by welding or by a detachable fastening member. The intermediate partition plate 16 is also fixed to the second outer wall portion 12B on its second surface 16b by welding or by a detachable fastening member.

[0036] (Discharge scroll configuration) Furthermore, the casing 10 of the centrifugal compressor 1 has a discharge scroll 50 formed therein. The discharge scroll 50 guides the working fluid discharged from the final stage impeller 22 of the multiple impellers 22 to the discharge port 112. The discharge scroll 50 is formed in both the first impeller group 22A and the second impeller group 22B. The discharge scroll 50 is positioned radially inward (Dri) relative to the outer casing 11. The discharge scroll 50 is also connected radially outward (Dro) to the diffuser flow path 42.

[0037] As shown in Figure 3, the discharge scroll 50 extends in the circumferential direction Dc around the central axis O. The discharge scroll 50 is a flow path formed in a spiral shape over a full circumference in the circumferential direction Dc around the central axis O. The discharge scroll 50 is connected to the diffuser flow path 42 at the inner Dri of the radial direction Dr over its entire circumference. The discharge scroll 50 is connected to the discharge port 112 (intermediate discharge port 114) at the outer Dro of the radial direction Dr in a portion of the circumferential direction Dc. The discharge scroll 50 is formed with a constant spacing of radial Dr when viewed from the axial direction Da.

[0038] Furthermore, the radial inner diameter Dr of the outer casing 11 is constant at the position where it overlaps with the discharge scroll 50 in the axial direction Da. In other words, the inner diameter of the outer casing 11 is formed in a circular shape at the position where it overlaps with the discharge scroll 50 in the axial direction Da. That is, the portions of the first inner surface 121 and the second inner surface 123 that overlap with the discharge scroll 50 in the axial direction Da are formed in a circular shape with a constant radial inner diameter Dr.

[0039] A discharge scroll 50 connected to the first impeller group 22A is designated as the first discharge scroll 50A. Another discharge scroll 50 connected to the second impeller group 22B is designated as the second discharge scroll 50B. In this embodiment, the first discharge scroll 50A and the second discharge scroll 50B are formed in a position that overlaps with at least one return passage 43 in the axial direction Da. Furthermore, the first discharge scroll 50A and the second discharge scroll 50B are formed in a state that they do not communicate with the return passage 43 in the radial direction Dr. In this embodiment, the first discharge scroll 50A and the second discharge scroll 50B are positioned outside the radial direction Dr with respect to at least some of the return passages 43. The first discharge scroll 50A will be described in detail below.

[0040] As shown in Figures 4 to 7, the first discharge scroll 50A is formed such that the axial spacing Da gradually narrows as it moves away from the intermediate discharge port 114 in the circumferential direction Dc. In other words, as shown in Figure 4, the axial spacing Da of the first discharge scroll 50A is widest at the position closest to the intermediate discharge port 114 in the circumferential direction Dc. Then, as shown in Figures 5 to 7, the axial spacing Da of the first discharge scroll 50A gradually narrows as it moves away from the intermediate discharge port 114 in the circumferential direction Dc. In this embodiment, the axial spacing Da of the first discharge scroll 50A gradually narrows so that the flow velocity of the working fluid circulating inside remains constant in the circumferential direction Dc.

[0041] Furthermore, as shown in Figures 4 to 7, the first discharge scroll 50A is formed by an external casing 11, a diaphragm 15, an intermediate partition plate 16, and an adjustment piece 60. The first discharge scroll 50A is surrounded by an inner scroll surface 51 of the inner Dri in the radial direction Dr, an outer scroll surface 52 of the outer Dro in the radial direction Dr, a first flow path forming surface 53 located on the second side Da2 in the axial direction Da, and a second flow path forming surface 54 located on the second side Da2 in the axial direction Da.

[0042] The inner circumferential surface 51 of the scroll is located inward Dri in the radial direction Dr in the first discharge scroll 50A. The inner circumferential surface 51 of the scroll is a surface facing outward Dr in the radial direction Dr. The inner circumferential surface 51 of the scroll is formed by the diaphragm 15. The inner circumferential surface 51 of the scroll is formed by a part of the outer surface of the diaphragm 15 being reduced in diameter in the radial direction Dr. In other words, the inner circumferential surface 51 of the scroll is formed by the outer shape of the diaphragm 15. When viewed from the circumferential direction Dc, the inner circumferential surface 51 of the scroll is located outward Dri in the radial direction Dr relative to the diffuser flow path 42. When viewed from the circumferential direction Dc, the inner circumferential surface 51 of the scroll is located inward Dri in the radial direction Dr relative to the boundary between the diaphragm 15 and the outer casing 11. The inner circumferential surface 51 of the scroll is formed at a constant distance in the radial direction Dr from the central axis O.

[0043] The outer circumferential surface 52 of the scroll is located on the outer side of the radial direction Dr in the first discharge scroll 50A. The outer circumferential surface 52 is the surface facing the inner side of the radial direction Dr. The outer circumferential surface 52 of the scroll faces the inner circumferential surface 51 in the radial direction Dr. The distance between the outer circumferential surface 52 and the inner circumferential surface 51 in the radial direction Dr is constant at both the axial direction Da and the circumferential direction Dc. In other words, the outer circumferential surface 52 of the scroll is formed at a constant distance in the radial direction Dr from the central axis O. The outer circumferential surface 52 of the scroll is formed by the outer casing 11. That is, the outer circumferential surface 52 of the scroll is formed by the first inner circumferential surface 121.

[0044] The second flow path forming surface 54 is located on the second side Da2 in the axial direction Da of the first discharge scroll 50A. The second flow path forming surface 54 is the surface facing the first side Da1 in the axial direction Da. The second flow path forming surface 54 is formed by the first surface 16a of the intermediate partition plate 16. The second flow path forming surface 54 is formed in a planar shape so as to be integrally connected at the same position as the surface forming the diffuser flow path 42 in the axial direction Da. That is, the portion of the diffuser flow path 42 that communicates with the first discharge scroll 50A has its second side Da2 surface in the axial direction Da formed by the first surface 16a of the intermediate partition plate 16. In other words, one side of the first discharge scroll 50A in the axial direction Da is formed by the intermediate partition plate 16.

[0045] The first flow path forming surface 53 is located on the first side Da1 in the axial direction Da of the first discharge scroll 50A. The first flow path forming surface 53 faces the second flow path forming surface 54 in the axial direction Da. The distance between the first flow path forming surface 53 and the second flow path forming surface 54 in the axial direction Da gradually increases in the circumferential direction Dc as it approaches the discharge port 112. The first flow path forming surface 53 is the surface facing the second side Da2 in the axial direction Da. The first flow path forming surface 53 is formed by the adjustment piece 60.

[0046] (Adjustment piece) The adjustment piece 60 forms at least a portion of the first flow path forming surface 53. That is, the adjustment piece 60 adjusts the axial spacing Da of the first discharge scroll 50A. One adjustment piece 60 is provided for each discharge scroll 50. The adjustment piece 60 is positioned radially inward Dr relative to the outer casing 11. The adjustment piece 60 is also positioned in contact with the inner circumferential surface 51 of the scroll. That is, the adjustment piece 60 is positioned between the outer casing 11 and the diaphragm 15 radially in Dr. At this time, the adjustment piece 60 is positioned so that there is no gap between it and the outer casing 11 and the diaphragm 15 radially in Dr. In this state, the adjustment piece 60 is fixed to the diaphragm 15.

[0047] The adjustment piece 60 is positioned away from the intermediate partition plate 16 in the axial direction Da. Furthermore, the adjustment piece 60 is positioned in contact with the diaphragm 15 on the first side Da1 in the axial direction Da. That is, the diaphragm 15 has a contact surface 15c that contacts the adjustment piece 60 in the axial direction Da. The contact surface 15c is the surface that faces the second flow path forming surface 54 in the axial direction Da when the adjustment piece 60 is not positioned. The distance between the contact surface 15c and the second flow path forming surface 54 in the axial direction Da is constant at both radial Dr and circumferential Dc positions. That is, the first flow path forming surface 53 has its axial distance Da of the first discharge scroll 50A adjusted by the adjustment piece 60. As shown in Figures 4 to 7, the first flow path forming surface 53 is formed such that the axial distance Da gradually widens as it moves away from the intermediate discharge port 114 in the circumferential direction Dc. In other words, the adjustment piece 60 is formed such that it gradually becomes thicker in the axial direction Da as it moves away from the intermediate discharge port 114 in the circumferential direction Dc. Furthermore, a portion of the first flow path forming surface 53 (the position closest to the intermediate discharge port 114 in the circumferential direction Dc) may be composed of a contact surface 15c.

[0048] (Configuration of each compression section) As described above, each compression section, namely the first compression section 20A and the second compression section 20B, has an inlet, a discharge port, a plurality of impellers 22, a plurality of diaphragms 15, a diffuser flow path 42, and a discharge scroll 50, respectively. Specifically, the first compression section 20A has an inlet 111, an intermediate discharge port 114, a first impeller group 22A, a first diaphragm group 15A, a diffuser flow path 42, and a first discharge scroll 50A.

[0049] The second compression section 20B includes an intermediate suction port 113, a discharge port 112, a second impeller group 22B, a second diaphragm group 15B, a diffuser flow path 42, and a second discharge scroll 50B. The second discharge scroll 50B is the same as the discharge scroll 50.

[0050] The second discharge scroll 50B, when viewed from the radial direction Dr, is formed to be recessed in the axial direction Da toward the opposite side from the first discharge scroll 50A relative to the intermediate partition plate 16. The basic configuration of the second discharge scroll 50B is the same as that of the first discharge scroll 50A described above. Below, only the parts that differ from the first discharge scroll 50A will be explained.

[0051] The second discharge scroll 50B is formed such that the axial distance Da gradually narrows as it moves away from the discharge port 112 in the circumferential direction Dc. The second discharge scroll 50B is formed by an external casing 11, a diaphragm 15, an intermediate partition plate 16, and a second adjustment piece 60B. The second adjustment piece 60B is positioned separately from the adjustment piece 60, but has the same shape as the adjustment piece 60 except for its size. The first side Da1 surface of the axial direction Da in the second discharge scroll 50B is formed by the second surface 16b of the intermediate partition plate 16. The second side Da2 surface of the axial direction Da in the second discharge scroll 50B is formed by the second adjustment piece 60B. The second adjustment piece 60B is formed such that it gradually becomes thicker in the axial direction Da as it moves away from the discharge port 112 in the circumferential direction Dc.

[0052] (Effects and Benefits) In the centrifugal compressor 1 with the above configuration, the working fluid discharged from the final stage impeller 22 passes through the final stage diffuser passage 42 and flows into the discharge scroll 50. The discharge scroll 50 is connected to the final stage diffuser passage 42 at the outer radial Dr. Therefore, when the working fluid flows from the diffuser passage 42 to the discharge scroll 50, its flow direction is not changed. As a result, separation of the working fluid when it flows from the diffuser passage 42 to the discharge scroll 50 can be suppressed. Furthermore, the discharge scroll 50 has a constant radial Dr spacing when viewed from the axial direction Da. In other words, the discharge scroll 50 has a constant radial Dr spacing regardless of its position in the circumferential direction Dc. In addition, the discharge scroll 50 is formed such that the axial Da spacing gradually narrows as it moves away from the discharge port 112 (intermediate discharge port 114) in the circumferential direction Dc. Therefore, in the discharge scroll 50, the flow area for the working fluid from the diffuser flow path 42 to the discharge port 112 (intermediate discharge port 114) can be secured by changing the spacing in the axial direction Da. As a result, the required performance can be ensured in the discharge scroll 50 while suppressing expansion of the discharge scroll 50 in the radial direction Dr. In this way, the discharge scroll 50 can be formed compactly while suppressing flow separation when the working fluid flows in.

[0053] In particular, the inner surface 51 of the scroll is positioned radially outward (Dro) relative to the diffuser flow path 42. Therefore, when the working fluid flows from the diffuser flow path 42 into the discharge scroll 50, there is no need to change the flow direction of the working fluid from radially outward (Dro) to radially inward (Dri). As a result, flow separation when the working fluid flows into the discharge scroll 50 can be suppressed with high precision.

[0054] Furthermore, the outer casing 11 is formed in a circular shape with a constant inner diameter in the radial direction Dr at the position where it overlaps with the discharge scroll 50 in the axial direction Da. In other words, the discharge scroll 50 in this embodiment is formed without changing the inner diameter of the outer casing 11. That is, according to this embodiment, the discharge scroll 50 can be formed without eccentricating the outer casing 11. Therefore, it is composed of concentric members, which makes it easier to assemble the centrifugal compressor 1.

[0055] Furthermore, the discharge scroll 50 has a gradually narrowing axial spacing Da such that the flow velocity of the working fluid circulating inside remains constant in the circumferential direction Dc. Therefore, while suppressing the expansion of the discharge scroll 50 in the radial direction Dr, stall and pressure loss of the working fluid circulating through the discharge scroll 50 can be reduced. In this way, stable performance can be ensured even with a compact discharge scroll 50.

[0056] Furthermore, the outer circumferential surface 52 of the discharge scroll 50 is formed by the inner circumferential surface of the outer casing 11. Therefore, the space in the inner radial Dr of the discharge scroll 50 is formed in the diaphragm 15. Thus, the discharge scroll 50 can be formed by a relatively simple process, such as reducing the diameter of a part of the diaphragm 15 in the radial direction Dr. In other words, the discharge scroll 50 can be formed while making the processing of the diaphragm 15 easier. In addition, the size of the radial Dr can be reduced while ensuring sufficient thickness of the outer casing 11. As a result, it is possible to form a discharge scroll 50 that can ensure stable performance while reducing the size of the radial Dr of the centrifugal compressor 1.

[0057] Furthermore, the axial distance Da between the discharge scrolls 50 (first discharge scroll 50A and second discharge scroll 50B) is adjusted by a single adjustment piece 60 (second adjustment piece 60B). In this embodiment, the size of the space between the discharge scrolls 50 is adjusted only by the adjustment piece 60 (second adjustment piece 60B). Therefore, it is possible to easily process components other than the adjustment piece 60 (second adjustment piece 60B). Also, the discharge scrolls 50 can be adjusted by adjusting the processing of only the adjustment piece 60 (second adjustment piece 60B). Since the adjustment piece 60 (second adjustment piece 60B) is a smaller component than the external casing 11 and diaphragm 15, it is easier to process. Therefore, it is possible to easily adjust the discharge scrolls 50 and improve the adjustment accuracy.

[0058] Furthermore, the adjustment piece 60 (second adjustment piece 60B) is positioned radially inward (Dr) relative to the outer casing 11. In other words, the adjustment piece 60 (second adjustment piece 60B) is housed inside the outer casing 11. Therefore, the expansion of the outer casing 11 in the radial direction (Dr) can be suppressed.

[0059] Furthermore, the outer diameter of the region overlapping with the second compression section 20B (second outer wall section 12B) is smaller than the outer diameter of the region overlapping with the first compression section 20A (first outer wall section 12A) in the axial direction Da. This allows for a compact design while ensuring the required radial size of the outer casing 11 for each compression section. Reducing the size of the outer casing 11 also helps to reduce costs.

[0060] Furthermore, the region overlapping with the first compression section 20A in the axial direction Da (first outer wall section 12A) and the region overlapping with the second compression section 20B in the axial direction Da (second outer wall section 12B) are formed in a circular shape with a constant outer diameter in the radial direction Dr over the entire axial direction Da. Therefore, the outer shape of the external casing 11 can be simplified. The external casing 11 of this embodiment has a horizontal flange 17. Because the first outer wall section 12A and the second outer wall section 12B are formed in a circular shape over the entire axial direction Da, the number of welding points between them and the horizontal flange 17 is reduced. As a specific example, in an external casing where the diameter is increased in the radial direction Dr over the axial direction Da corresponding to the discharge scroll, there are many places where the outer diameter changes. In such a complex external casing, there are more welding points with the horizontal flange 17 than in the external casing 11 of this embodiment. Therefore, by simplifying the structure of the external casing 11, the number of welding points with the horizontal flange 17 and the like can be reduced. This reduces the manufacturing cost of the centrifugal compressor 1 and shortens the manufacturing period. Furthermore, the overall manufacturing precision of the centrifugal compressor 1 can also be improved.

[0061] Furthermore, the number of welds between the first outer wall section 12A and the second outer wall section 12B and the horizontal flange 17 is reduced, which simplifies the shape of the horizontal flange 17. Specifically, the number of corner-like parts formed on the horizontal flange 17 can be reduced. This suppresses the stress and deformation that occurs in the horizontal flange 17 (casing 10) when internal pressure is applied or when temperature changes occur. Therefore, the pressure resistance strength and airtightness reliability of the casing 10 can be improved.

[0062] Furthermore, the intermediate partition plate 16 is positioned to separate the first compression section 20A and the second compression section 20B. The adjustment piece 60 and the second adjustment piece 60B are positioned away from the intermediate partition plate 16 in the axial direction Da. Therefore, it is easier to secure space for installing the adjustment piece 60 and the second adjustment piece 60B. In addition, it is possible to easily install the adjustment piece 60 and the second adjustment piece 60B.

[0063] Furthermore, the intermediate partition plate 16 is connected to the first outer wall portion 12A and the second outer wall portion 12B on surfaces facing the axial direction Da (first surface 16a and second surface 16b). Specifically, the intermediate partition plate 16 is connected to the first outer wall portion 12A on the first surface 16a and to the second outer wall portion 12B on the second surface 16b. This allows the connection (such as welding) between the intermediate partition plate 16 and the first outer wall portion 12A and the second outer wall portion 12B to be performed from the outer surface Dr in the radial direction Dr. Therefore, the welding assembly work of the outer casing 11 can be made easier. In addition, this structure can strengthen the connection strength between the intermediate partition plate 16 and the outer casing 11. This makes it easier to withstand the differential pressure caused by the difference in working fluid pressure between the first compression section 20A and the second compression section 20B. Furthermore, the outer diameter in the radial direction Dr of the intermediate partition plate 16 is formed to be larger than the outer diameter of the first outer wall portion 12A. This ensures a secure connection between the first surface 16a and the first outer wall portion 12A. In other words, it prevents a structure in which a portion of the end face of the second side Da2 of the first outer wall portion 12A does not come into contact with the first surface 16a (does not overlap in the axial direction Da). Therefore, the connection strength between the intermediate partition plate 16 and the outer casing 11 can be reliably ensured.

[0064] Furthermore, the discharge scrolls 50 (first discharge scroll 50A and second discharge scroll 50B) have one side in the axial direction Da formed by the intermediate partition plate 16. Therefore, the discharge scrolls 50 can be formed by a relatively simple machining process, such as machining the diaphragm 15 in the axial direction Da. Thus, the discharge scrolls 50 can be formed while facilitating the machining of the diaphragm 15.

[0065] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure.

[0066] For example, the centrifugal compressor 1 according to this embodiment may have three or more compression sections. In other words, the centrifugal compressor 1 according to this embodiment is not limited in the number of compression sections formed.

[0067] Furthermore, the centrifugal compressor 1 according to this embodiment is not limited to a so-called back-to-back type single-screw multi-stage centrifugal compressor. As a specific example, the second compression section 20B may be configured to compress the working fluid by circulating it from the first side Da1 to the second side Da2 in the axial direction Da.

[0068] Furthermore, the discharge scroll 50 according to the embodiment is not limited to being formed in a position that overlaps with at least one return flow path 43 in the axial direction Da. In other words, the discharge scroll 50 according to the embodiment may be formed in a position that does not overlap with the return flow path 43 in the axial direction Da.

[0069] Furthermore, the adjustment piece 60 and the second adjustment piece 60B may have any structure as long as they can form at least a part of the first flow path forming surface 53. In other words, the adjustment piece 60 and the second adjustment piece 60B may be formed as a solid block structure, or they may be formed as a hollow structure. When the adjustment piece 60 and the second adjustment piece 60B are formed as a hollow shape, for example, they may have a structure that includes a plate material that forms a part of the first flow path forming surface 53 and a support member that supports this plate material.

[0070] <Note> The centrifugal compressor 1 described in the embodiment can be understood, for example, as follows:

[0071] (1) The centrifugal compressor 1 according to the first embodiment comprises a rotating shaft 2 extending in the axial direction Da to which the central axis O extends, and a casing 10 having a suction port 111 formed on the first side Da1 of the axial direction Da and a discharge port 112 formed on the second side Da2 of the axial direction Da, wherein the rotating shaft 2 is disposed within the casing 10 and an impeller 22 compresses and discharges the working fluid supplied from the first side Da1 of the axial direction Da to the outer side Dro in the radial direction Dr with respect to the central axis O. The casing 10 comprises a diaphragm 15 formed in a cylindrical shape extending in the axial direction Da so as to cover the impeller 22, an outer casing 11 formed in a cylindrical shape extending in the axial direction Da so as to cover the diaphragm 15, a diffuser flow path 42 that guides the working fluid discharged from the impeller 22 toward the outer side Dro in the radial direction Dr, and a discharge scroll 50 that guides the working fluid discharged from the impeller 22 to the discharge port 112. It has a plurality of compression sections (20A, 20B) for compressing the working fluid at different pressures, each compression section (20A, 20B) having the suction ports (111, 113), the discharge ports (112, 114), a plurality of the impellers 22, a plurality of the diaphragms 15, the diffuser passage 42, and the discharge scroll 50, each of the discharge scrolls 50 connected to the corresponding diffuser passage 42 at the radial Dr outside Dr, and the external casing The outer casing 11 is positioned on the inner side of the radial Dr relative to the 11, extends in the circumferential direction Dc around the central axis O, and is formed such that the distance in the radial Dr when viewed from the axial direction Da is constant, and the distance in the axial direction Da gradually narrows as it moves away from the discharge ports (112, 114) in the circumferential direction Dc, and the outer casing 11 is formed in a circular shape such that the inner diameter of the radial Dr is constant at the position where it overlaps with the discharge scroll 50 in the axial direction Da.

[0072] With this configuration, the working fluid discharged from the final stage impeller 22 passes through the diffuser flow path 42 and flows into the discharge scroll 50. The discharge scroll 50 is connected to the diffuser flow path 42 at the outer radial Dr. Therefore, separation of the working fluid when it flows from the diffuser flow path 42 to the discharge scroll 50 can be suppressed. Furthermore, the radial Dr spacing of the discharge scroll 50 is constant when viewed from the axial Da. In other words, the radial Dr spacing of the discharge scroll 50 is constant regardless of the position in the circumferential Dc. In addition, the discharge scroll 50 is formed such that the axial Da spacing gradually narrows as it moves away from the discharge ports (112, 114) in the circumferential Dc. Therefore, the discharge scroll 50 can secure a flow area for the working fluid to flow from the diffuser flow path 42 to the discharge ports (112, 114) by changing the axial Da spacing. As a result, the required performance can be ensured for the discharge scroll 50 while suppressing its expansion in the radial direction Dr. In this way, the discharge scroll 50 can be formed compactly while suppressing flow separation when the working fluid flows in.

[0073] (2) The centrifugal compressor 1 according to the second embodiment is the centrifugal compressor 1 of (1), wherein the distance between the discharge scrolls 50 in the axial direction Da gradually narrows so that the flow velocity of the working fluid flowing inside in the circumferential direction Dc is constant.

[0074] This configuration suppresses the radial expansion of the discharge scroll 50 (Dr) while reducing stall and pressure loss of the working fluid flowing through the discharge scroll 50. In this way, stable performance can be ensured even with a compact discharge scroll 50.

[0075] (3) The centrifugal compressor 1 according to the third embodiment is the centrifugal compressor 1 of (1) or (2), wherein the discharge scroll 50 has an inner scroll surface 51 in the radial direction Dr that is formed by the outer shape of the diaphragm 15, and an outer scroll surface 52 in the radial direction Dr that is opposite to the inner scroll surface 51 that is formed by the inner surface of the outer casing 11, the distance in the radial direction Dr from the central axis O is constant.

[0076] With this configuration, the discharge scroll 50 has its outer peripheral surface 52 formed by the inner peripheral surface of the outer casing 11. Therefore, the discharge scroll 50 can be formed while facilitating the machining of the diaphragm 15.

[0077] (4) The centrifugal compressor 1 according to the fourth embodiment is the centrifugal compressor 1 according to any one of (1) to (3), wherein the casing 10 further has adjustment pieces 60, 60B for adjusting the spacing of the axial Da of the discharge scrolls 50 (50A, 50B) such that the spacing of the axial Da gradually widens as the circumferential Dc approaches the discharge ports (112, 114), and each of the plurality of discharge scrolls 50A, 50B has one of the adjustment pieces 60, 60B.

[0078] With this configuration, the axial spacing Da of the discharge scrolls 50 (50A, 50B) is adjusted by a single adjustment piece 60, 60B, respectively. Therefore, the spacing of each discharge scroll 50 (50A, 50B) can be adjusted using only the adjustment pieces 60, 60B, making machining easier. Furthermore, the adjustment accuracy of the spacing of the discharge scrolls 50 (50A, 50B) can be improved.

[0079] (5) The centrifugal compressor 1 according to the fifth embodiment is the centrifugal compressor 1 of (4), wherein the adjustment pieces 60, 60B are positioned in the inner Dri in the radial direction Dr with respect to the outer casing 11 and are fixed to the diaphragm 15.

[0080] With this configuration, the adjustment pieces 60 and 60B are housed inside the outer casing 11. Therefore, the radial expansion of the outer casing 11 in the Dr direction can be suppressed.

[0081] (6) The centrifugal compressor 1 according to the sixth embodiment is the centrifugal compressor 1 of (4) or (5), wherein the plurality of compression sections (20A, 20B) have a first compression section 20A and a second compression section 20B that compresses the working fluid at a pressure higher than that of the first compression section 20A, and the outer casing 11 is formed such that the outer diameter of the region overlapping with the second compression section 20B is smaller than the outer diameter of the region overlapping with the first compression section 20A in the axial direction Da.

[0082] With this configuration, the outer casing 11 is formed with a smaller outer diameter in the region corresponding to the second compression section 20B than in the region corresponding to the first compression section 20A. Therefore, the radial expansion of the outer casing 11 in Dr can be suppressed.

[0083] (7) The centrifugal compressor 1 according to the seventh embodiment is the centrifugal compressor 1 according to any one of (4) to (6), wherein the plurality of compression sections (20A, 20B) have a first compression section 20A and a second compression section 20B that compresses the working fluid at a pressure higher than that of the first compression section 20A, and the outer casing 11 is formed in a circular shape in the region that overlaps with the first compression section 20A in the axial direction Da, with a constant outer diameter in the radial direction Dr throughout the entire region, and the region that overlaps with the second compression section 20B in the axial direction Da is formed in a circular shape with a constant outer diameter in the radial direction throughout the entire region.

[0084] With this configuration, the outer casing 11 is formed in a circular shape with a constant outer diameter in the radial direction Dr over the entire axial direction Da for both the region corresponding to the first compression section 20A and the region corresponding to the second compression section 20B. Therefore, the outer shape of the outer casing 11 can be simplified. This also reduces the number of welding points when attaching components to the outer Dro of the radial direction Dr of the outer casing 11.

[0085] (8) The centrifugal compressor 1 according to the eighth embodiment is the centrifugal compressor 1 of (6) or (7), wherein the casing 10 further has an intermediate partition plate 16 that covers the rotating shaft 2 and is positioned between the first compression section 20A and the second compression section 20B in the axial direction Da so as to separate the first compression section 20A and the second compression section 20B, and the adjustment pieces 60, 60B are positioned apart from the intermediate partition plate 16 in the axial direction Da.

[0086] With this configuration, the adjustment pieces 60 and 60B are connected to the parts that are not the intermediate partition plate 16. Therefore, the adjustment pieces 60 and 60B can be easily installed.

[0087] (9) The centrifugal compressor 1 according to the ninth embodiment is the centrifugal compressor 1 of (8), wherein the outer casing 11 has a first outer wall portion 12A located in a region overlapping with the first compression portion 20A in the axial direction Da, and a second outer wall portion 12B located in a region overlapping with the second compression portion 20B in the axial direction Da, and the intermediate partition plate 16 has a surface facing the first side Da1 in the axial direction Da that is connected to the first outer wall portion 12A, and a surface facing the second side Da2 in the axial direction Da that is connected to the second outer wall portion 12B.

[0088] With this configuration, the intermediate partition plate 16 is connected to the first outer wall portion 12A and the second outer wall portion 12B on a surface facing the axial direction Da. This allows the connection (such as welding) between the intermediate partition plate 16 and the first outer wall portion 12A and the second outer wall portion 12B to be performed from the outer side Dro in the radial direction Dr. Therefore, the welding assembly work of the outer casing 11 can be made easier.

[0089] (10) The centrifugal compressor 1 according to the tenth embodiment is the centrifugal compressor 1 of (8) or (9), wherein one side of the discharge scroll 50 (50A, 50B) in the axial direction Da is formed by the intermediate partition plate 16.

[0090] With this configuration, one side of the discharge scroll 50 (50A, 50B) in the axial direction Da is formed by the intermediate partition plate 16. Therefore, the discharge scroll 50 (50A, 50B) can be formed while facilitating processing of the diaphragm 15. [Explanation of symbols]

[0091] 1…Centrifugal compressor O…Central axis 2…Rotation axis 21…Rotating shaft body 22... Impeller 22A...First impeller group 22B...Second impeller group 23... Impeller flow path 10…Casing 11…External casing 12A…First outer wall part 12B…Second outer wall part 121...First inner peripheral surface 122...First outer peripheral surface 123...Second inner peripheral surface 124…Second outer peripheral surface 13A…First side wall part 13B…Second side wall part 17…Horizontal flange 111... Inlet 112...Discharge port 113...Intermediate suction port 114…Intermediate discharge port 15…Diaphragm 15A...First diaphragm group 15B...Second diaphragm group 15c…Contact surface 40…Casing flow path 41…Introductory channel 42... Diffuser channel 43…Return channel 16…Intermediate partition 16a...front page 16b…Second side 50…Discharge scroll 50A...First discharge scroll 50B...Second discharge scroll 51...Scroll inner surface 52…Scroll outer surface 53...First flow path forming surface 54…Second flow path forming surface 60... Adjustment piece 60B... Second adjustment piece 20A...First Compression Section 20B...Second compression section 31…Thrust bearing 32A, 32B… Journal bearings Da... Axis Da1…first side Da2…Second side Dr…Radial direction Dro... outside Dri…inside Dc…Circumferential direction Dv…Vertical direction

Claims

1. A rotational axis extending in the axial direction from which the central axis extends, The casing comprises a suction port formed on the first side in the axial direction and a discharge port formed on the second side in the axial direction, The rotating shaft has an impeller located within the casing that compresses and discharges the working fluid supplied from the first side in the axial direction radially outward with respect to the central axis. The aforementioned casing is A diaphragm formed in a cylindrical shape extending in the axial direction so as to cover the impeller, An external casing formed in a cylindrical shape extending in the axial direction so as to cover the diaphragm, A diffuser channel that guides the working fluid discharged from the impeller toward the radially outward direction, A discharge scroll that guides the working fluid discharged from the impeller to the discharge port, It has, It has multiple compression sections for compressing the working fluid at different pressures, Each compression section has the suction port, the discharge port, a plurality of impellers, a plurality of diaphragms, the diffuser flow path, and the discharge scroll. Each of the discharge scrolls is Connected radially outward to the corresponding diffuser flow path, Displaced radially inward from the outer casing, Extending in the circumferential direction around the aforementioned central axis, The radial spacing when viewed from the axial direction is constant, and the axial spacing gradually narrows as it moves away from the discharge port in the circumferential direction. The external casing is formed in a circular shape with a constant radial inner diameter at a position where it overlaps with the discharge scroll in the axial direction. Centrifugal compressor.

2. The discharge scroll has a gradually narrowing axial spacing such that the flow velocity of the working fluid circulating inside it remains constant in the circumferential direction. The centrifugal compressor according to claim 1.

3. The aforementioned discharge scroll is The inner surface of the scroll in the radial direction is formed by the outer shape of the diaphragm. The radially outer scroll surface facing the radially inner surface of the scroll is formed by the inner surface of the outer casing, which has a constant radial distance from the central axis. The centrifugal compressor according to claim 1.

4. The casing further includes an adjustment piece for adjusting the axial spacing of the discharge scrolls such that the axial spacing gradually increases as it approaches the discharge port in the circumferential direction. Each of the multiple discharge scrolls has one of the adjustment pieces. A centrifugal compressor according to any one of claims 1 to 3.

5. The adjustment piece is positioned radially inward relative to the outer casing and is fixed to the diaphragm. The centrifugal compressor according to claim 4.

6. Each of the multiple compression units comprises a first compression unit and a second compression unit that compresses the working fluid at a pressure higher than that of the first compression unit. The outer casing is formed such that the outer diameter of the region overlapping the second compression portion is smaller than the outer diameter of the region overlapping the first compression portion in the axial direction. The centrifugal compressor according to claim 4.

7. Each of the multiple compression units comprises a first compression unit and a second compression unit that compresses the working fluid at a pressure higher than that of the first compression unit. The aforementioned external casing is The region that overlaps with the first compression portion in the axial direction is formed in a circular shape with a constant radial outer diameter throughout its entirety. The region that overlaps with the second compression portion in the axial direction is formed in a circular shape with a constant outer diameter in the radial direction throughout its entirety. The centrifugal compressor according to claim 4.

8. The casing further includes an intermediate partition plate that is positioned between the first compression section and the second compression section in the axial direction, so as to separate the first compression section and the second compression section, and covers the rotating shaft. The adjustment piece is positioned axially away from the intermediate partition plate. The centrifugal compressor according to claim 6.

9. The outer casing has a first outer wall portion located in a region overlapping with the first compression portion in the axial direction, and a second outer wall portion located in a region overlapping with the second compression portion in the axial direction. In the aforementioned intermediate partition plate, The surface facing the first side in the axial direction is connected to the first outer wall portion. The surface facing the second side in the axial direction is connected to the second outer wall portion. The centrifugal compressor according to claim 8.

10. The discharge scroll has one side in the axial direction formed by the intermediate partition plate. The centrifugal compressor according to claim 8.

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