Seal structures and rotating machinery

Abstract

Even when an inclined surface is formed, sealing performance is ensured. [Solution] The seal structure comprises a plurality of step portions that protrude to form a base surface facing radially and a stepped surface facing upstream, and a seal fin that forms a minute gap between the base surface of the corresponding step portion. The step portion has an inclined surface that connects the base surface and the stepped surface. The seal fin has a seal-facing surface. On the upstream side of the seal-facing surface, a cavity connected to the minute gap is formed. The step portion is formed such that when the first length is L, which is the length from the seal-facing surface to the stepped surface in the axial direction, and the second length is W, which is the length of the cavity in the axial direction, it satisfies 0.3W ≤ L ≤ 0.9W, and when the third length is C, which is the length of the inclined surface in the axial direction, it satisfies 4C ≤ L.

Description

Technical Field

[0001] The present disclosure relates to a seal structure and a rotating machine.

Background Art

[0002] In a rotating machine such as a compressor or a steam turbine, it includes a casing and a rotor rotatably disposed inside the casing. The rotor has, for example, a rotor shaft and an impeller fixed to the rotor shaft. In such a rotating machine, a gap is formed between the rotor and the casing which is a stator. However, the fluid passing through such a gap does not impart a rotational force to the rotor including the impeller. Therefore, in order to improve the performance of the rotating machine, it is important to reduce the flow rate of the fluid leaking through the gap.

[0003] On the other hand, for example, Patent Document 1 describes a seal structure provided in a steam turbine which is one of the rotating machines. The seal structure described in Patent Document 1 has a step portion having a stepped surface and a seal fin forming a minute gap with respect to the step portion. Further, in this seal structure, a space called a cavity is formed on the upstream side with respect to the seal fin. And by defining the relationship between the size of the cavity, the size of the step portion, and the minute gap, the leakage flow rate is further reduced to improve the sealing performance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when actually forming a seal structure having a step portion and a seal fin on a rotating machine, the corners formed on the step portion are chamfered to form an inclined surface such as a C-face (square face) or R-face (round face). However, when the rotating machine is small, the step portion also becomes small, so the area on which the inclined surface is formed relative to the step portion becomes larger. As a result, the influence of the area on which the inclined surface is formed becomes larger, leading to an increase in the leakage flow rate in the seal structure. For this reason, a structure that can ensure sealing performance even when an inclined surface is formed is desired.

[0006] This disclosure is made to address the above-mentioned needs and aims to provide a sealing structure and a rotating machine that can ensure sealing performance even when an inclined surface is formed. [Means for solving the problem]

[0007] To solve the above problems, the seal structure according to the present disclosure is formed between the outer circumferential surface of a rotor that rotates around an axis and the inner circumferential surface of a stator that is arranged to surround the rotor from the radially outside, and seals a gap through which fluid flows from the upstream side to the downstream side in the axial direction along the axis, and comprises a plurality of step portions formed on one of the outer circumferential surface of the rotor and the inner circumferential surface of the stator, projecting radially toward the other of the outer circumferential surface of the rotor and the inner circumferential surface of the stator, forming a base surface facing the radial direction and a stepped surface facing the upstream side, and arranged in the axial direction, and a seal formed on the other, projecting radially toward each of the step portions, and forming a minute gap between the base surface of the corresponding step portion. The rotor comprises a seal fin and a step portion having an inclined surface connecting the base surface and the stepped surface, the seal fin extends radially and has a seal-facing surface facing the upstream side in the axial direction, and in the axial direction, on the upstream side of the seal-facing surface, a cavity is formed which is the space between the outer circumferential surface of the rotor and the inner circumferential surface of the stator in the radial direction and is connected to the minute gap, and the step portion is formed such that when the first length is the length from the seal-facing surface to the stepped surface in the axial direction, which is L, and the second length is the length of the cavity in the axial direction, it satisfies 0.3W ≤ L ≤ 0.9W, and when the third length is the length of the inclined surface in the axial direction, which is C, it satisfies 4C ≤ L.

[0008] Furthermore, the rotating machine relating to this disclosure is equipped with the aforementioned sealing structure. [Effects of the Invention]

[0009] According to the seal structure and rotating machine of this disclosure, sealing performance can be ensured even if an inclined surface is formed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the turbo chiller according to this embodiment. [Figure 2]This is a schematic cross-sectional view of the turbo compressor according to this embodiment. [Figure 3] This figure details the seal structure according to this embodiment, and is an enlarged view of the main part I shown in Figure 2. [Figure 4] This figure details the seal fin according to this embodiment, and is an enlarged view of the main part II shown in Figure 3. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the rotating machinery and sealing structure according to this disclosure will be described with reference to the attached drawings. However, this disclosure is not limited to these embodiments.

[0012] (Turbo chiller) A turbo chiller 100 according to an embodiment of the present invention will be described with reference to Figure 1. As shown in Figure 1, the turbo chiller 100 includes a turbo compressor 1 that compresses a refrigerant W as a fluid, a condenser 2 that condenses the refrigerant W compressed by the turbo compressor 1 with cooling water, a first expansion valve 3 which is an expansion section that reduces the pressure of the refrigerant W from the condenser 2, and an economizer 4 that separates the refrigerant W from the first expansion valve 3 into two phases: gas and liquid.

[0013] Furthermore, the turbo chiller 100 includes an inlet passage that guides the gas phase of the refrigerant W from the economizer 4 to the turbo compressor 1, a second expansion valve 6 which serves as an expansion section to reduce the pressure of the liquid phase from the economizer 4 again, and an evaporator 7 which evaporates the refrigerant W from the second expansion valve 6.

[0014] The turbo chiller 100 has a refrigeration cycle in which a turbo compressor 1, a condenser 2, a first expansion valve 3, a second expansion valve 6, and an evaporator 7 are sequentially connected by piping.

[0015] The condenser 2 is a device that cools the refrigerant W compressed by the turbo compressor 1 by exchanging heat with cooling water or the like and makes it into a liquid state. For example, the condenser 2 is a shell-and-tube heat exchanger. The condenser 2 is connected to the discharge port of the turbo compressor 1 by a pipe. The gas phase part of the condenser 2 and the gas phase part of the evaporator 7 are connected by a pipe.

[0016] The first expansion valve 3 adiabatically expands and reduces the pressure of the liquid refrigerant W from the condenser 2, and evaporates a part of the liquid, thereby making the refrigerant W into a gas-liquid two-phase state. The first expansion valve 3 is connected to the condenser 2 by a pipe. The first expansion valve 3 is arranged between the condenser 2 and the economizer 4.

[0017] The economizer 4 is a device that separates the refrigerant W made into a gas-liquid two-phase state in the first expansion valve 3 into a gas phase and a liquid phase. The economizer 4 is connected to the first expansion valve 3 by a pipe. The gas phase separated from the gas-liquid two-phase refrigerant W by the economizer 4 flows into the turbo compressor 1 through a pipe. The liquid phase separated from the gas-liquid two-phase refrigerant W by the economizer 4 flows into the second expansion valve 6 through a pipe.

[0018] The second expansion valve 6 adiabatically expands and reduces the pressure of the refrigerant W from which the gas phase W has been separated by the economizer 4 and only the liquid phase remains. In the turbo refrigerator 100 of the present embodiment, a configuration is adopted in which the refrigerant W is decompressed using expansion valves such as the first expansion valve 3 and the second expansion valve 6, but it is not limited to this, and other expansion parts may be used to decompress the refrigerant W. The second expansion valve 6 is connected to the evaporator 7 by a pipe.

[0019] The evaporator 7 exchanges heat between the refrigerant W from the second expansion valve 6 and water or the like and evaporates it to make it into a saturated vapor state. The refrigerant W made into a saturated vapor state in the evaporator 7 flows into the turbo compressor 1 through a pipe.

[0020] (Turbo Compressor) Next, the turbo compressor 1, which is a rotating machine of the present embodiment, will be described in detail with reference to FIG. 2. The turbo compressor 1 includes a rotor 10, a stator 20, a bearing portion 40, and a seal structure 50.

[0021] The rotor 10 is rotatable with respect to the stator 20 about the axis O. The rotor 10 extends in the axial direction Da along which the axis O extends. The rotor 10 of the present embodiment has a rotor body 11, a first impeller 12, a second impeller 13, and a rotor core 14.

[0022] The rotor body 11 has a rod shape extending along the axis O1. The rotor body 11 extends straight in the axial direction Da about the axis O. A thrust collar 11a that projects outward in the radial direction from the outer peripheral surface of the rotor body 11 is formed on a part of the outer peripheral surface of the rotor body 11 in the axial direction Da.

[0023] The first impeller 12 is integrally fixed to one end (the left side in FIG. 2) of the rotor body 11 in the direction of the axis O. By rotating about the axis O together with the rotor body 11, the first impeller 12 pumps the refrigerant W flowing in from one side in the axial direction Da toward the outer side Dro in the radial direction Dr.

[0024] The second impeller 13 is integrally fixed to the other end (the right side in FIG. 2) of the rotor body 11 in the axial direction Da. That is, the second impeller 13 is arranged on the opposite side of the first impeller 12 in the axial direction Da with respect to the rotor body 11. By rotating about the axis O together with the rotor body 11, the second impeller 13 pumps the refrigerant W flowing in from the other side in the axial direction Da toward the outer side Dro in the radial direction Dr. The turbo compressor 1 having the first impeller 12 and the second impeller 13 thus has a two-stage compression structure in which the refrigerant W compressed by the first impeller 12 is further compressed by the second impeller 13. In addition to the refrigerant W compressed by the first impeller 12, the gas phase of the refrigerant W introduced from the economizer 4 is introduced into the second impeller 13.

[0025] The rotor core 14 is integrally fixed to the outer circumferential surface of the rotor body 11. The rotor core 14 has a laminated steel plate structure fitted onto the outer circumferential surface of the rotor body 11. Multiple permanent magnets are arranged in the laminated steel plate structure at intervals in the circumferential direction of the rotor 10 centered on axis O.

[0026] The stator 20 is positioned to surround the rotor 10 from the outer radial direction Dr. In this embodiment, the stator 20 has a housing 21 and a stator core 22.

[0027] The housing 21 is positioned to surround the rotor body 11 from the outside in the radial direction Dr. The ends of the rotor body 11 in the axial direction Da are exposed through openings at both ends of the housing 21.

[0028] The stator core 22 is positioned to surround the rotor core 14 from the outer edge in the radial direction Dr. The stator core 22 is positioned with a radial distance Dr from the rotor core 14. The stator core 22 is fixed to the housing 21. The stator core 22, together with the rotor core 14, constitutes the motor 30. In such a motor 30, current is supplied to the stator core 22 from an external source, and each permanent magnet follows the rotating magnetic field generated by this current, causing the rotor core 14 and the rotor body 11, which is integrally fixed to the rotor core 14, to rotate about axis O relative to the stator core 22.

[0029] The bearing section 40 is fixed to the housing 21. The bearing section 40 rotatably supports the rotor body 11. The bearing section 40 includes a pair of radial bearings 41 and a thrust bearing 42.

[0030] A pair of radial bearings 41 are positioned to sandwich the motor 30 from the axial direction Da. Within the housing 21, the pair of radial bearings 41 are spaced apart in the axial direction Da, with the rotor core 14 sandwiched between them. The radial bearings 41 restrict the movement of the rotor body 11 in the radial direction Dr.

[0031] The thrust bearing 42 is positioned to sandwich the thrust collar 11a of the rotor body 11 from the axial direction Da. The thrust bearing 42 is positioned between a pair of radial bearings 41 in the axial direction Da. The thrust bearing 42 is positioned between the radial bearing 41 located near the second impeller 13 and the rotor core 14 in the axial direction Da. The thrust bearing 42 supports the rotor body 11 from the axial direction Da without contact, so that the position of the rotor body 11 in the axial direction Da is in a predetermined position. The thrust bearing 42 restricts the movement of the rotor body 11 in the axial direction Da.

[0032] (Configuration of the sealing structure) The seal structure 50 is formed between the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20. In this embodiment, the seal structure 50 seals the gap between the rotor body 11 and the casing around its entire circumference. The seal structure 50 seals the gap through which the refrigerant W (fluid) flows from the upstream side to the downstream side in the axial direction Da. Here, the upstream side is the inflow side in the flow direction in the axial direction Da of the fluid flowing through the gap between the rotor body 11 and the casing that the seal structure 50 seals. Furthermore, the upstream side of the seal structure 50 is a position with high pressure in the axial direction Da relative to the seal structure 50. Therefore, in this embodiment, the upstream side of the seal structure 50 is the side closer to the impeller relative to the seal structure 50. Furthermore, the downstream side is the outflow side in the flow direction in the axial direction Da of the fluid flowing through the gap between the rotor body 11 and the casing that the seal structure 50 seals. Furthermore, the downstream side of the seal structure 50 is a position with low pressure in the axial direction Da relative to the seal structure 50. Therefore, in this embodiment, the downstream side of the seal structure 50 is the side closer to the motor 30 relative to the seal structure 50.

[0033] The seal structure 50 is arranged in pairs. The pair of seal structures 50 prevents the refrigerant W compressed by the first impeller 12 and the second impeller 13 from leaking to the locations where the motor 30 and bearing section 40 are located inside the casing. The pair of seal structures 50 are positioned in the axial direction Da between the first impeller 12 and the radial bearing 41, and between the second impeller 13 and the radial bearing 41, respectively. The pair of seal structures 50 are positioned in the axial direction Da so as to be aligned with the first impeller 12 and the second impeller 13.

[0034] Here, as an example, we will describe a seal structure 50 located near the second impeller 13. However, the seal structure 50 located near the first impeller 12 has the same structure as the seal structure 50 located near the second impeller 13, except that the orientation of the axial direction Da is different. As shown in Figures 3 and 4, the seal structure 50 of this embodiment has a plurality of step portions 51 and a plurality of seal fins 52.

[0035] The step portion 51 is formed on one of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20. In this embodiment, the step portion 51 is formed on the outer circumferential surface of the rotor body 11, which is the rotor 10. The step portion 51 protrudes radially Dr toward the other of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20. Therefore, in this embodiment, the step portion 51 protrudes from the outer circumferential surface of the rotor body 11 toward the inner circumferential surface of the casing, which is the stator 20. The step portions 51 are arranged in a row in the axial direction Da. The multiple step portions 51 are formed in a stepped shape by gradually increasing the amount of protrusion from the outer circumferential surface of the rotor body 11 toward the outer circumferential surface Dr in the radial direction Dr toward the outer circumferential surface, so that they approach the inner circumferential surface of the casing from the upstream side toward the downstream side in the axial direction Da. In this embodiment, the seal structure 50 has, for example, three step portions 51. The step portion 51 has a base surface 511, a stepped surface 512, and an inclined surface 513.

[0036] The base surface 511 is a surface facing the radial direction Dr. In this embodiment, the base surface 511 is a smooth surface facing outward from the radial direction Dr. The base surface 511 is formed parallel to the outer circumferential surface of the rotor body 11.

[0037] The stepped surface 512 is a surface facing the upstream side in the axial direction Da. The stepped surface 512 extends radially Dr perpendicular to the base surface 511. In other words, the step portion 51 protrudes from the outer circumferential surface of the rotor body 11 so as to form the base surface 511 and the stepped surface 512. The stepped surfaces 512 of each step portion 51 extend radially Dr parallel to each other. The heights of the multiple stepped surfaces 512 are formed to be the same.

[0038] The inclined surface 513 connects the base surface 511 and the stepped surface 512. The inclined surface 513 is a plane facing upstream in the axial direction Da and outward in the radial direction Dr. The inclined surface 513 is formed as a chamfered surface by cutting off the corner where the base surface 511 and the stepped surface 512 intersect. In other words, the radial inclined surface in this embodiment is inclined at 45° with respect to the base surface 511 and the stepped surface 512. Therefore, because the inclined surface 513 is formed, there is no sharp corner connecting the base surface 511 and the stepped surface 512 in the step portion 51.

[0039] Furthermore, the inclined surface 513 is not limited to being a flat surface. The inclined surface 513 may be a curved surface formed by R-chamfering. Also, even if the inclined surface 513 is a flat surface, it is not limited to being inclined at a 45° angle with respect to the base surface 511 and the step surface 512. The inclined surface 513 may be inclined at different angles with respect to the base surface 511 and the step surface 512.

[0040] Furthermore, an annular groove 57 is formed in the casing so as to face the step portion 51 in the axial direction Da. The annular groove 57 is formed to extend in the circumferential direction. The annular groove 57 is recessed from the inner circumferential surface of the casing toward the outer side Dro in the radial direction Dr. Multiple annular recesses 571 are formed in the annular groove 57 in the axial direction Da so as to face the multiple step portions 51. The multiple annular recesses 571 are formed in a stepped manner so as to gradually widen toward the outer side Dro in the radial direction Dr from the upstream side toward the downstream side in the axial direction Da. In this embodiment, for example, the annular groove 57 has three annular recesses 571 so as to be the same number as the step portions 51.

[0041] The seal fins 52 are formed on the other of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20. In other words, the seal fins 52 are formed on the side of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20 where no steps are formed. In this embodiment, the seal fins 52 are formed on the inner circumferential surface of the casing. Specifically, the seal fins 52 are formed on the inner circumferential surface of the annular recess 571 facing the inner Dri in the radial direction Dr. The seal fins 52 protrude radially Dr toward each step portion 51. In other words, one seal fin 52 is formed for each annular recess 571, so one seal fin 52 is positioned for each step portion 51. Therefore, the multiple seal fins 52 are positioned apart from each other in the axial direction Da. The seal fins 52 form a small gap 70 between themselves and the base surface 511 of the corresponding step portion 51. The dimensions of the small gap 70 are set to be the smallest possible while maintaining a safe range where the two do not come into contact, taking into account the thermal expansion of the casing and the rotor 10 axis. In other words, the seal fin 52 and the base surface 511 are formed so that they do not come into contact with each other during the operation of the turbo compressor 1. Furthermore, the seal fin 52 is shaped so that its axial length Da is smaller than that of the base surface 511. In other words, the seal fin 52 is shaped so that its radial length Dr is larger than its axial length Da. The seal fin 52 has a seal-facing surface 521.

[0042] The seal-facing surface 521 is a plane extending in the radial direction Dr. The seal-facing surface 521 faces upstream in the axial direction Da.

[0043] Furthermore, because multiple seal fins 52 are formed, multiple cavities 60 are formed in the space between the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20. The number of cavities 60 is the same as the number of seal fins 52 and steps. Each cavity 60 is formed between a seal fin 52 corresponding to each step portion 51 and a casing wall portion (or another seal fin 52) facing the axial direction Da upstream of this seal fin 52. The cavity 60 is a space that communicates with a minute gap 70.

[0044] Furthermore, let L be the first length, which is the length from the seal-facing surface 521 to the stepped surface 512 in the axial direction Da. Furthermore, let W be the second length, which is the length of the cavity 60 in the axial direction Da. Furthermore, let C be the third length, which is the length of the inclined surface 513 in the axial direction Da. Furthermore, let H be the fourth length, which is the length of the minute gap 70 in the radial direction Dr. Furthermore, let h1 be the fifth length, which is the protruding length of the seal fin 52 in the radial direction Dr (the length of the seal-facing surface 521 in the radial direction Dr). Furthermore, let h2 be the protruding length of the step portion 51 in the radial direction Dr.

[0045] In this case, the step portion 51 is formed such that 0.3W ≤ L ≤ 0.9W. In addition, the step portion 51 is formed such that 4C ≤ L. Furthermore, the step portion 51 is formed such that 3H ≤ L.

[0046] Furthermore, it is preferable that the first length L is formed to be large enough to ensure the second length W (the range in which the cavity 60 can be formed). In other words, it is preferable that the first length L is smaller than the second length W. Also, the third length C is smaller than the sixth length h2. It is preferable that the third length C is, for example, 0.1 mm or more and within 5.0 mm. It is preferable that the fourth length H is smaller than the fifth length h1 and the sixth length h2. It is preferable that the fifth length h1 is larger than the first length L and the sixth length h2.

[0047] (Effects and Benefits) In the seal structure 50 of this embodiment as described above, a portion of the refrigerant W compressed by the first impeller 12 and the second impeller 13 (for example, a few percent) flows out from the first impeller 12 and the second impeller 13, then flows around the back of the first impeller 12 and the second impeller 13 and into the annular groove 57. The refrigerant W that flows into the annular groove 57 reaches the step portion 51. The refrigerant W that leaks from upstream positions such as the first impeller 12 and the second impeller 13 rides up onto the step portion 51 via the stepped surface 512. At this time, separation occurs, and a vortex-like constricted flow is generated in the space upstream of the minute gap 70 in the axial direction Da and outside the base surface 511 in the radial direction Dr. In the seal structure 50, this constricted flow creates a downflow just before the minute gap 70, suppressing the flow rate of refrigerant W passing through the minute gap 70. However, the step portion 51 of this embodiment has an inclined surface 513 that connects the base surface 511 and the stepped surface 512. In the seal structure 50 of this embodiment, the first length L, which is the length of the base surface 511, is shortened by the formation of the inclined surface 513. Furthermore, when the refrigerant W flows over the step portion 51, it flows along the inclined surface 513 and the base surface 511, so separation does not occur and the flow contraction becomes small. As a result, there was a possibility that sufficient sealing performance could not be ensured in the seal structure 50. In contrast, the seal structure 50 of this embodiment is formed to satisfy both 0.3W ≤ L ≤ 0.9W and 4C ≤ L. Therefore, even if the inclined surface 513 is formed, a step portion 51 can be formed that has a base surface 511 with sufficient length in the axial direction Da. As a result, separation can be caused in the flow of refrigerant W that has flowed over the step portion 51, and flow contraction can be generated with high precision. Therefore, the leakage flow rate in the minute gap 70 can be stably reduced. This ensures stable sealing performance even when an inclined surface 513 is formed.

[0048] Furthermore, the step portion 51 is formed such that 3H ≤ L is satisfied. Therefore, even if an inclined surface 513 is formed, the step portion 51 having a base surface 511 with sufficient length in the axial direction Da can be formed more reliably. As a result, separation can be caused in the flow of refrigerant W that has risen onto the step portion 51, and flow contraction can be generated with higher precision. Therefore, the leakage flow rate in the minute gap 70 can be reduced more stably. This ensures more stable sealing performance even if an inclined surface 513 is formed.

[0049] Furthermore, the inclined surface 513 is formed as a flat surface. Therefore, the inclined surface 513 can be formed on the step portion 51 by a simple process such as chamfering.

[0050] Furthermore, by equipping the rotating machine with the seal structure 50 described above, the sealing performance can be improved. In particular, when the rotating machine is the turbo compressor 1 of the turbo chiller 100, as in this embodiment, the rotating machine is a very small device. As a result, the seal structure 50 installed on the small rotating machine is also very small. Therefore, when an inclined surface 513 is formed on the step portion 51, it is greatly affected by the shape of the step portion 51, such as the length of the base surface 511. However, by applying the seal structure 50 of this embodiment, even when an inclined surface 513 is formed, the sealing performance can be stably ensured.

[0051] (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.

[0052] The shape of the seal structure 50 is not limited to that of this embodiment. For example, the number of step portions 51, seal fins 52, and annular recesses 571 is not limited to three, as in this embodiment. The number of step portions 51, seal fins 52, and annular recesses 571 can be determined according to the sealing performance required in the rotating machine in which the seal structure 50 is installed. Therefore, the number of step portions 51, seal fins 52, and annular recesses 571 may be four or more, or two or fewer.

[0053] Furthermore, the rotating machine is not limited to a turbo compressor 1. The rotating machine can be any device that circulates fluid internally and has a rotor 10 and a stator 20. Therefore, the rotating machine may be a multi-shaft centrifugal compressor, an axial flow compressor, a steam turbine, a gas turbine, or a pump.

[0054] Furthermore, the step portion 51 is not limited to being formed on the rotor 10, as in the rotor body 11 of this embodiment. In other words, contrary to this embodiment, the seal fins 52 may be arranged on the rotor 10 and the step portion 51 may be formed on the stator 20.

[0055] <Note> The seal structure 50 and rotating machine described in each embodiment can be understood, for example, as follows.

[0056] (1) The seal structure 50 according to the first embodiment is formed between the outer circumferential surface of a rotor 10 that rotates about an axis O and the inner circumferential surface of a stator 20 that is arranged to surround the rotor 10 from the outside in the radial direction Dr, and seals a gap through which fluid flows from the upstream side to the downstream side in the axial direction Da extending from the axis O, and comprises a plurality of step portions 51 formed on one of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20, projecting in the radial direction Dr toward the other of the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20, and arranged in line in the axial direction Da, forming a base surface 511 facing the radial direction Dr and a stepped surface 512 facing the upstream side, and a seal fin 52 formed on the other, projecting in the radial direction Dr toward each of the step portions 51, and forming a minute gap 70 between the base surface 511 of the corresponding step portion 51 The step portion 51 has an inclined surface 513 connecting the base surface 511 and the stepped surface 512, the seal fin 52 has a seal-facing surface 521 that extends in the radial direction Dr and faces the upstream side in the axial direction Da, and in the axial direction Da, on the upstream side of the seal-facing surface 521, a cavity 60 is formed which is the space between the outer circumferential surface of the rotor 10 and the inner circumferential surface of the stator 20 in the radial direction Dr and is connected to the minute gap 70, and the step portion 51 is formed such that when the first length is the length from the seal-facing surface 521 to the stepped surface 512 in the axial direction Da and the second length is the length of the cavity 60 in the axial direction Da, it satisfies 0.3W ≤ L ≤ 0.9W, and when the third length is the length of the inclined surface 513 in the axial direction Da, it satisfies 4C ≤ L.

[0057] With this configuration, the seal structure 50 is formed to satisfy both 0.3W ≤ L ≤ 0.9W and 4C ≤ L. Therefore, even if an inclined surface 513 is formed, a step portion 51 having a base surface 511 with sufficient length in the axial direction Da can be formed. As a result, separation can be caused in the flow of refrigerant W that has risen onto the step portion 51, and flow contraction can be generated with high precision. Therefore, the leakage flow rate in the minute gap 70 can be stably reduced. This ensures stable sealing performance even if an inclined surface 513 is formed.

[0058] (2) The seal structure 50 according to the second embodiment is the seal structure 50 of (1), wherein the step portion 51 is formed such that 3H ≤ L when the fourth length, which is the length of the minute gap 70 in the radial direction Dr, is H.

[0059] With this configuration, even if an inclined surface 513 is formed, a step portion 51 having a base surface 511 with sufficient length in the axial direction Da can be formed more reliably. As a result, separation can be caused in the flow of refrigerant W that has risen onto the step portion 51, and flow contraction can be generated with higher precision. Therefore, the leakage flow rate in the minute gap 70 can be reduced more stably. This ensures that sealing performance can be secured more stably even if an inclined surface 513 is formed.

[0060] (3) The seal structure 50 according to the third embodiment is the seal structure 50 of (1) or (2), wherein the inclined surface 513 is a plane.

[0061] With this configuration, the inclined surface 513 can be formed on the step portion 51 by a simple process such as chamfering.

[0062] (4) The rotating machine according to the fourth embodiment comprises the seal structure 50 described in (1) to (3).

[0063] This configuration allows for improved sealing performance. [Explanation of Symbols]

[0064] 100 Turbo chiller 1. Turbo compressor 2. Condenser 3 First expansion valve 4. Economizer 6 Second expansion valve 7 Evaporator W refrigerant O axis 10 rotors 11 Rotor body 11a Thrust Collar 12 First Impeller 13. Second impeller 14 Rotor Core 20 stata 21 Housing 22 Stator Cores 30 motors 40 Bearing section 41 Radial bearing 42 Thrust bearings 50 sealing structure 51 Step section 511 Base surface 512 Step surface 513 Slope 52 Seal Fins 521 Seal opposing surface 57 Ring groove 571 Annular recess 60 Cavity 70 tiny gaps Da axis Dr radial direction Dro Outer (Radial) Dri (inner side, radial direction)

Claims

1. A seal structure formed between the outer circumferential surface of a rotor that rotates around an axis and the inner circumferential surface of a stator arranged to surround the rotor from the radially outside, which seals a gap through which fluid flows from the upstream side to the downstream side in the axial direction along the axis, A plurality of stepped portions are formed on one of the outer circumferential surface of the rotor and the inner circumferential surface of the stator, projecting radially toward the other of the outer circumferential surface of the rotor and the inner circumferential surface of the stator, and arranged in the axial direction, forming a base surface facing the radial direction and a stepped surface facing the upstream side. The other side is formed and protrudes radially toward each of the step portions, forming a seal fin between the corresponding step portion and the base surface, The step portion has an inclined surface that connects the base surface and the stepped surface, The seal fin extends radially and has a seal-facing surface that faces the upstream side in the axial direction. In the axial direction, on the upstream side with respect to the seal-facing surface, a cavity is formed in the radial direction between the outer circumferential surface of the rotor and the inner circumferential surface of the stator, which is connected to the minute gap. The aforementioned step portion is Let L be the first length, which is the length from the seal-facing surface to the stepped surface in the axial direction, and let W be the second length, which is the length of the cavity in the axial direction. Then, satisfy 0.3W ≤ L ≤ 0.9W. A seal structure is formed such that 4C ≤ L, where C is the third length, which is the length of the inclined surface in the axial direction.

2. The seal structure according to claim 1, wherein the step portion is formed such that 3H ≤ L is satisfied when the fourth length, which is the length of the minute gap in the radial direction, is H.

3. The seal structure according to claim 1 or claim 2, wherein the inclined surface is a flat surface.

4. A rotating machine comprising the seal structure according to any one of claims 1 to 3.

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