JP2016008537A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of easily machining a channel shape which has high aerodynamic performance.SOLUTION: A centrifugal compressor is equipped with an impeller 5 journaled to a rotary shaft 4, and a housing 3 which rotatably stores the impeller. The impeller has hub 28 and 34 with which the rotary shaft is fitted, a plurality of blades 29 and 17 provided on the hubs 28 and 34, and a crown plate 31 provided on the blades, opposing to the hubs over the whole circumference, and forming an impeller inner channel 21 between the hubs and the crown plate 31. The impeller is divided into a first impeller portion 26 on a downstream side in an axial direction, and a second impeller portion 27 on an upstream side. The dividing is carried out so as to make the first impeller portion and the second impeller portion respectively include the hubs and the blades. The first impeller portion and the second impeller portion are integrated through the rotary shaft.

Description

  The present invention relates to a centrifugal compressor that is used in a supercharger, a gas turbine, an industrial air facility, and the like and compresses a gas fluid using centrifugal force.

  As an impeller used for a single-shaft multistage centrifugal compressor, an open impeller in which a blade formed on a disk and a shroud formed on a housing side are not in contact with each other, a crown plate is provided integrally with the blade, the disk and the blade, There is a closed impeller in which a closed channel is formed between the crown plate and the crown plate. When a fluid other than air is used as a working fluid such as liquefied natural gas, a closed impeller is mainly applied from the viewpoint of safety.

  One of the conventional methods for manufacturing a closed impeller is a method of cutting a disk, a blade, and a crown plate from a single material by machining. Since the size of a cutting tool that can be used for cutting is generally limited, the smaller the size of the closed impeller, the more difficult it is to manufacture. This is because the smaller the size of the closed impeller, the larger the size of the tool that occupies the region to be cut, and the easier the interference between the tool and the material. In this way, since the difficulty of processing may become a constraint for impeller design, even if there is a closed impeller shape that should be aimed from the viewpoint of aerodynamic performance such as compression efficiency, it is manufactured because its size is small There was a technical problem that could not be done.

  In this case, if the impeller for a low load with a high radial position (ie, a large opening surrounded by the crown plate) as seen from the rotation axis of the blade leading edge is used, the size of the cutting tool for machining is large. Production is possible because of On the other hand, when the flow rate of the working fluid is large, in order to improve aerodynamic performance, it is desirable to lower the radial position of the front edge of the blade and to provide an axial inflow blade (inducer) on the upstream side of the blade. Because of the above-described constraint conditions, it has been difficult to process a channel shape that is ideal in aerodynamic design.

  Patent Document 1 includes a disk in which an impeller and a blade are integrally cut, and a cover that faces the disk, and a plurality of spacers that protrude toward the cover are formed on the edge of the cover blade. When the brazing material is disposed on the cover side blade edge and brazing is performed by overlapping the disk and the cover, the cover side blade edge and the cover blade are attached by the spacer. An impeller manufacturing method is disclosed in which a distance from a surface is maintained and brazing material is prevented from flowing out.

JP 2012-102678 A

  As described above, in the prior art, even if there is a closed impeller shape that should be aimed at from the viewpoint of aerodynamic performance such as compression efficiency, it may not be possible to process due to the high degree of processing difficulty. There was a technical problem to be solved that the closed impeller had to be compromised with a shape that could be processed, and as a result, the aerodynamic performance of the impeller had to be sacrificed depending on the processing difficulty.

  The present invention includes an impeller that is pivotally attached to a rotating shaft, and a housing that rotatably accommodates the impeller. The impeller includes a hub on which the rotating shaft is fitted, and a plurality of sheets provided on the hub. And a crown plate that is provided on the blade and is opposed to the hub over the entire circumference and forms a flow path in the impeller between the hub and the impeller, which is downstream in the axial direction. The first impeller portion and the upstream second impeller portion are divided so that the first impeller portion and the second impeller portion include the hub and the blade, respectively. The impeller portion and the second impeller portion relate to a centrifugal compressor integrated via the rotating shaft.

  According to the present invention, the division is divided so that the second impeller portion does not include the crown plate, and the upstream end of the crown plate is located downstream of the upstream end of the blade of the second impeller portion. The working fluid that flows between the housing and the crown plate is related to the centrifugal compressor configured to join the flow path in the impeller downstream from the upstream end of the blade of the second impeller portion. Is.

  In the present invention, the division may be performed such that the first impeller portion and the second impeller portion include the hub, the blade, and the crown plate, respectively, and the crown plate of the first impeller portion and the crown plate A gap is formed between the second impeller portion and the crown plate, and the working fluid that flows between the housing and the crown plate flows through the gap and merges with the flow path in the impeller. This relates to a centrifugal compressor.

  In the present invention, a convex portion is formed at the central portion of one of the hub of the first impeller portion and the hub of the second impeller portion, and a concave portion is formed on the other, and the convex portion and the The present invention relates to a centrifugal compressor in which a concave portion can be fitted and the first impeller portion and the second impeller portion are integrated by fitting the convex portion and the concave portion.

  According to the present invention, first and second key grooves communicating with the hub of the first impeller portion and the hub of the second impeller portion are engraved, and a third key groove is engraved on the rotating shaft. The key piece is fitted over the first, second, and third key grooves, and the rotary shaft, the first impeller portion, and the second impeller portion are integrated through the key piece. This relates to a centrifugal compressor.

  Furthermore, the present invention relates to a centrifugal compressor in which the blade of the first impeller portion and the blade of the second impeller portion are parallel to the dividing surface of the hub.

  According to the present invention, an impeller that is pivotally attached to a rotating shaft and a housing that rotatably accommodates the impeller are provided, and the impeller is provided on the hub and the hub on which the rotating shaft is fitted. A plurality of blades, and a crown plate provided on the blade, facing the hub over the entire circumference and forming a flow path in the impeller between the hub and the impeller in the axial direction The first impeller portion on the downstream side and the second impeller portion on the upstream side are divided, and the division is divided so that the first impeller portion and the second impeller portion include the hub and the blade, respectively. Since the first impeller portion and the second impeller portion are integrated via the rotating shaft, the first impeller portion and the second impeller portion can be individually manufactured. Therefore, it is possible to manufacture a closed impeller having a smaller size and a smaller shape than those of the prior art, and the size and shape of the closed impeller to be manufactured are less compromised. As a result, the aerodynamic performance of the impeller is sacrificed depending on the degree of processing difficulty, and the problems of the prior art can be solved.

It is a sectional side view which shows the centrifugal compressor which concerns on 1st Example of this invention. It is a sectional side view which shows the impeller of the most upstream side of the centrifugal compressor which concerns on 1st Example of this invention, and its peripheral part. It is a sectional side view which shows the most upstream impeller of the centrifugal compressor which concerns on 2nd Example of this invention, and its peripheral part.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, referring to FIG. 1, an outline of a multistage centrifugal compressor according to a first embodiment of the present invention will be described.

  The centrifugal compressor 1 is connected to a driving source, for example, a turbine via a rotating shaft 4. The centrifugal compressor 1 passes through the outer housing 2 and the inner housing 3 through rotation of a turbine wheel or the like through a box-shaped outer housing 2, an inner housing 3 provided inside the outer housing 2, The rotating shaft 4 and a plurality (three in FIG. 1) of impellers 5a to 5c that are rotatably accommodated in the inner housing 3 are provided.

  A flow path 6 is formed in the inner housing 3, and a scroll 7 is formed at the downstream end of the flow path 6. The flow path 6 is formed such that the working fluid 9 flows from the central portion toward the outer peripheral side, and further bends alternately at the outer peripheral side and the central side so as to be reversed and flow toward the center. The impellers 5a to 5c are arranged in multiple stages at portions extending from the central portion to the outer peripheral side.

  The impellers 5 a to 5 c are attached to the rotary shaft 4, and the impellers 5 a to 5 c rotate integrally with the rotary shaft 4. A labyrinth seal 8 is provided between the rotary shaft 4 and the inner housing 3 to seal between the flow path 6 and the outside of the centrifugal compressor 1.

  One end of the upper surface of the outer housing 2 is connected to the upstream end of the flow path 6, and a suction nozzle 11 for sucking the working fluid 9 is provided in the flow path 6. The part is provided with a discharge nozzle 13 which is connected to the scroll 7 and discharges the compressed working fluid 12 compressed by the centrifugal compressor 1.

  Further, a side stream channel 14 communicating with the middle of the channel 6, for example, between the impellers 5 a and 5 b, is formed in the inner housing 3, and the side stream channel 14 is formed on the upper surface of the outer housing 2. The side stream nozzle 15 connected to is provided. The side stream flow path 14 and the side stream nozzle 15 are formed in the middle of the flow path 6 in the middle of the flow path 6 according to processing requirements when, for example, a polymer weight gas is used as the working fluid 9. Take out and supply.

  A guide vane 16 for rectifying the working fluid 9 sucked from the suction nozzle 11 and flowing into the impeller 5a is provided on the upstream side of the impeller 5a in the flow path 6, and the upstream side of the impeller 5a. An upstream blade 17 (axial inflow blade) is formed for improving aerodynamic performance when the flow rate of the working fluid 9 is large.

  Next, referring to FIG. 2, the details of the first stage impeller 5a on the most upstream side where the flow rate of the working fluid 9 flowing through the flow path 6 is large and the periphery thereof will be described. In FIG. 2, the guide vane 16 is omitted. In the following description, the impeller 5 a is described as the impeller 5, and the inner housing 3 is described as the housing 3.

  The flow path 6 includes a working fluid flow path 18 that circulates the working fluid 9 toward the impeller 5, a compressed working fluid flow path 19 that circulates the working fluid 9 after being compressed by the impeller 5, and It is comprised from the impeller flow path 21 mentioned later.

  The impeller 5 is provided in the middle of the flow path 6, that is, between the working fluid flow path 18 and the compression working fluid flow path 19, and the working fluid flow path 18 and the compression are provided in the impeller 5. The impeller channel 21 communicating with the working fluid channel 19 is formed. The downstream end of the working fluid channel 18, that is, the vicinity of the inlet of the impeller channel 21 serves as a suction port 22 for the working fluid 9, and the impeller channel 21 extends from the suction port 22 to a discharge port. The cross-sectional area of the flow path gradually decreases toward the center.

  A diffuser 23, a crossover vent 24, and a return guide vane 25 are provided in the compressed working fluid flow path 19 from the upstream side. The diffuser 23 converts the speed of the working fluid 9 accelerated by the centrifugal force of rotation of the impeller 5 into pressure, and increases the pressure of the working fluid 9.

  The crossover vent 24 bends the compressed working fluid flow path 19 by 180 ° to invert the working fluid 9. The return guide vane 25 is inverted by the crossover vent 24. The working fluid 9 is supplied with an appropriate inflow angle and supplied to the next stage.

  The impeller 5 has a two-part structure in which a first impeller portion 26 on the downstream side and a second impeller portion 27 on the upstream side are divided in the axial direction. The first impeller portion 26 on the downstream side is provided with a downstream hub 28 having a through hole (not shown) into which the rotary shaft 4 can be fitted, and an outer peripheral surface of the downstream hub 28 at equal intervals in the circumferential direction. The plurality of downstream blades 29 and a crown plate 31 fixed to the downstream blades 29 and facing the downstream hub 28 over the entire circumference. The crown plate 31 protrudes upstream from the front edge (upstream edge) of the downstream blade 29, and the lower surface of the protrusion is parallel to the axis of the rotary shaft 4. Further, in order to secure a joining line between the downstream blade 29 and the crown plate 31 and improve the strength, the front edge portion of the downstream blade 29 is inclined with respect to the upstream end surface of the downstream hub 28. doing.

   An upstream end surface of the downstream hub 28, which is a split surface of the first impeller portion 26, is orthogonal to the axis of the rotating shaft 4, and an annular recess 32 is formed around the through hole. . A first key groove 33 having an upstream end face of the downstream hub 28 opened is formed in the through hole.

  The downstream hub 28, the downstream blade 29, and the crown plate 31 form the impeller flow path 21 that is closed in the impeller 5.

  The second impeller portion 27 on the upstream side of the impeller 5 includes an upstream hub 34 having a through hole (not shown) into which the rotary shaft 4 can be fitted, and an outer peripheral surface of the upstream hub 34. The plurality of upstream blades 17 are provided at equal intervals in the circumferential direction. The upper end of the upstream blade 17 is parallel to the axis of the rotary shaft 4, and the number and interval of the upstream blade 17 are equal to the number and interval of the downstream blade 29. Further, the rear edge portion (downstream edge portion) of the upstream blade 17 is inclined with respect to the downstream end surface of the upstream hub 34 in accordance with the inclination of the front edge portion of the downstream blade 29.

  A downstream end surface of the upstream hub 34 that is a dividing surface of the second impeller portion 27 is orthogonal to the axis of the rotating shaft 4, and an annular convex portion 36 is formed around the through hole. Yes. The convex portion 36 can be fitted to the concave portion 32. The length of the convex portion 36 in the axial direction is shorter than the depth of the concave portion 32 in the axial direction. The through hole is provided with a second key groove 37 in which the upstream end face and the downstream end face of the upstream hub 34 are opened.

  With the first key groove 33 and the second key groove 37 aligned, the convex portion 36 is fitted into the concave portion 32, so that the downstream end surface of the convex portion 36 and the upstream of the concave portion 32 are arranged. The first impeller portion 26 and the second impeller portion 27 are integrated in a state where a slight gap is formed between the side end surfaces.

  In this state, the upstream end surface of the downstream hub 28 and the downstream end surface of the upstream hub 34 are in close contact with each other, and the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are in close contact with each other. The lower surface of the projecting portion of the crown plate 31 and a part of the upper end of the upstream blade 17 are in close contact with each other, and the first key groove 33 and the second key groove 37 are arranged on the same communication line. Communicate with. At this time, the upstream blade 17 is located at the suction port 22, and the front edge portion of the upstream blade 17 protrudes upstream from the crown plate 31.

  A third key groove 38 is also formed on the rotary shaft 4, and the first key groove 33, the first key groove 33, and the second key groove 37 are aligned with each other. A key piece 39 is fitted over the key groove 33, the second key groove 37, and the third key groove 38. The first impeller portion 26, the second impeller portion 27, and the rotating shaft 4 are connected by the key piece 39, and the first impeller portion 26, the second impeller portion 27, and the rotating shaft 4 are relative to each other. The rotation is constrained and the relative rotation between the first impeller portion 26 and the second impeller portion 27 is constrained.

  The housing 3 is provided with a labyrinth seal 41 that seals between the crown plate 31 and the housing 3. The labyrinth seal 41 is provided so as to face the upstream end portion of the outer peripheral surface of the crown plate 31, and the compressed working fluid 9 is supplied from the outlet portion of the flow path 21 in the impeller to the crown plate 31 and the housing. 3 and the flow into the suction port 22 is suppressed.

  A labyrinth seal 42 is also provided between the housing 3 and the downstream hub 28, and the working fluid 9, which has been pressurized by the diffuser 23 and rectified by the return guide vane 25, flows between the housing 3 and the downstream side. It is prevented from flowing into between the side hub 28 and flowing into the outlet of the in-impeller channel 21.

  Next, the operation of the centrifugal compressor 1 will be described.

  The impeller 5 is integrally rotated by rotating the rotating shaft 4 by rotation of a motor, a turbine wheel, or the like. The suction port 22 has a flow passage cross-sectional area that gradually decreases toward the impeller 5, and the upstream blade 17 is disposed, and is sucked from the suction nozzle 11 and flows through the working fluid flow passage 18. The working fluid 9 is contracted and rectified by the upstream blade 17 in the course of flowing into the impeller channel 21.

  The working fluid 9 that has flowed into the in-impeller channel 21 is compressed by the centrifugal force generated by the rotation of the impeller 5, is pressurized, and is discharged from the in-impeller channel 21.

  The working fluid 9 discharged from the flow path 21 in the impeller is decelerated and increased in pressure in the process of passing through the diffuser 23, and after being reversed by the crossover vent 24, the working fluid 9 is appropriately supplied by the return guide vane 25. The working fluid 9 provided with the inflow angle flows into the next stage impeller 5b (see FIG. 1).

  The working fluid 9 is further compressed in the course of flowing through the impeller flow paths 21b and 21c (see FIG. 1) of the impellers 5b and 5c in the downstream stage, and is compressed by the discharge nozzle 13 via the scroll 7. The fluid 12 is discharged.

  During the processing, a part of the working fluid 9 compressed by the impeller 5 flows between the crown plate 31 and the housing 3, passes through the labyrinth seal 41, and slightly returns as the return flow 43. It flows into the suction port 22.

  In the first embodiment, the impeller 5 is divided into the first impeller portion 26 and the second impeller portion 27 in the axial direction, and the first impeller portion 26 and the second impeller portion 27 are individually separated. Can be produced. Therefore, for example, when the first impeller portion 26 is manufactured individually by machining, the curved shape of the shape from the front edge portion to the rear edge portion of the downstream blade 29 in the region surrounded by the crown plate 31 is obtained. As a result, the blade portion of the cutting tool can easily reach from the front edge portion to the rear edge portion in the region surrounded by the crown plate 31. Therefore, compared to a conventional closed impeller that cuts a disk, blade, and crown plate from a single material, the difficulty of processing is reduced, and it is possible to manufacture an impeller with a smaller size and a smaller shape. Further, when the second impeller portion 27 is manufactured by machining, the second impeller portion 27 can be processed without being restricted by the diameter of the opening portion by the crown plate 31, so that it is easier to process than the conventional technique. The degree is relaxed. Therefore, by dividing the impeller 5 into the first impeller portion 26 and the second impeller portion 27 in the axial direction, it becomes possible to manufacture a closed impeller having a smaller size and a smaller shape than those of the prior art. The compromised dimensions and shape of the closed impeller should be reduced. As a result, the aerodynamic performance of the impeller is sacrificed depending on the degree of processing difficulty, and the problems of the prior art can be solved. Further, the technical restrictions based on the difficulty of processing are reduced, and the impeller 5 having a small channel shape or an ideal flow channel shape (the channel 21 in the impeller) can be easily manufactured. be able to.

  Further, the convex portion 36 of the second impeller portion 27 may be press-fitted into the concave portion 32 of the first impeller portion 26, and the first impeller portion 26, the second impeller portion 27, Are integrated, and welding for integrating the first impeller portion 26 and the second impeller portion 27 becomes unnecessary, and the manufacturing cost can be reduced.

  In addition, the first key groove 33 and the second key groove 37 formed on the first impeller portion 26 and the second impeller portion 27 are aligned with each other, and the first key groove 33 and the second key groove 37 are aligned. The key piece 39 is fitted into the third key groove 38 formed on the rotary shaft 4, and the first impeller portion 26, the second impeller portion 27, and the rotary shaft are inserted through the key piece 39. 4, the first impeller portion 26, the second impeller portion 27 and the rotation shaft 4 can be prevented from rotating relative to each other, and the first impeller portion 26 and the second impeller portion 27 can be prevented from rotating relative to each other. Relative rotation can be prevented. Further, if the rotary shaft 4, the first impeller portion 26, and the second impeller portion 27 can be completely integrated with the key piece 39 without rattling, the fitting of the concave portion 32 and the convex portion 36 can be omitted.

  Further, since the front edge portion of the upstream blade 17 protrudes upstream from the front edge portion of the crown plate 31, the front edge of the upstream blade 17 of the return flow 43 that has flowed into the suction port 22. Interference with the part is suppressed. Therefore, the turbulence of the flow when the return flow 43 joins the working fluid 9 is suppressed, the pressure loss is reduced, and the efficiency of the centrifugal compressor 1 can be improved.

  In addition, the upstream end of the crown plate 31 is inclined so that the return flow 43 flows into the suction port 22 toward the downstream side. Since the pressure difference with the inflow part can be reduced, the flow rate of the return flow 43 can be reduced, the pressure loss can be further reduced, and the efficiency of the centrifugal compressor 1 can be improved.

  The first impeller portion 26 and the second impeller portion 27 have split surfaces orthogonal to the axis of the rotary shaft 4 and the rotational stress values of the members constituting the impeller 5 are within the limit values. If there is, it can be divided at an arbitrary position.

  In the first embodiment, the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are inclined with respect to the dividing surface of the first impeller portion 26 and the second impeller portion 27. However, the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 may be parallel or flush with the dividing surfaces of the first impeller portion 26 and the second impeller portion 27. Good. With this configuration, the first impeller portion 26 and the second impeller portion 27 can be easily manufactured, and the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 can be provided. It can be easily adhered.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment, the first impeller portion 26 includes a downstream hub 28, a downstream blade 29, and a downstream crown plate 45, and the second impeller portion 27 includes the upstream hub 34, the upstream blade 17, and the upstream side. A crown plate 46 is used. The upstream crown plate 46 is fixed to the upstream blade 17 and faces the upstream hub 34 over the entire circumference.

  A front edge portion of the downstream blade 29 protrudes slightly upstream from a front edge portion of the downstream crown plate 45, and a rear edge portion of the upstream blade 17 is a rear edge of the upstream crown plate 46. It protrudes slightly downstream from the part.

  When the convex portion 36 of the second impeller portion 27 is fitted into the concave portion 32 of the first impeller portion 26 and the first impeller portion 26 and the second impeller portion 27 are integrated, the downstream side The upstream end surface of the hub 28 and the downstream end surface of the upstream hub 34 are in close contact with each other, and the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are in close contact with each other. A slight gap is formed between the front edge portion of the downstream crown plate 45 and the rear edge portion of the upstream crown plate 46, and a return flow path 47 is formed by the gap.

  The return channel 47 may be a groove formed over the entire circumference, or may be a hole that is formed radially at equal intervals in the circumferential direction. Further, a plurality of holes may be formed so as to be point symmetric.

  When the centrifugal compressor 1 is operated, a part of the working fluid 9 compressed by the impeller 5 circulates between the downstream crown plate 45 and the housing 3 and returns as the return flow 43 to the return flow path. 47 flows into the impeller channel 21.

  In the second embodiment, the return flow 43 flows into the impeller channel 21, so that the return flow 43 does not interfere with the front edge of the upstream blade 17. Therefore, the turbulence of the flow when the return flow 43 joins the working fluid 9 is suppressed, the pressure loss is reduced, and the efficiency of the centrifugal compressor 1 can be improved.

  Further, by allowing the return flow 43 to flow into the impeller internal passage 21 via the return passage 47, the pressure difference with the working fluid 9 at the outlet of the impeller internal passage 21 is reduced. The flow rate of the return flow 43 can be reduced.

  Further, by changing the dividing position of the upstream crown plate 46 and the downstream crown plate 45, the protruding amount of the front edge portion of the downstream blade 29, the protruding amount of the rear edge portion of the upstream blade 17, and the like. The position and size of the return channel 47 can be freely adjusted, and the performance of the centrifugal compressor 1 can be further improved.

  In the second embodiment, the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are formed on the dividing surface of the first impeller portion 26 and the second impeller portion 27. However, as in the first embodiment, the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are connected to the first impeller portion 26 and the second impeller portion 27, respectively. The first impeller portion 26 and the second impeller portion 27 are easily manufactured in parallel with or in a plane with the dividing surface, and the front edge portion of the downstream blade 29 and the rear edge portion of the upstream blade 17 are formed. It may be possible to make contact easily.

  In the first embodiment and the second embodiment, the concave portion 32 is formed in the downstream hub 28 and the convex portion 36 is formed in the upstream hub 34. A convex portion may be formed on the upstream hub 34, and a concave portion may be formed on the upstream hub 34.

  In the first embodiment and the second embodiment, only the most upstream impeller 5 is divided and the upstream blade 17 is provided. However, the number of the impellers 5 provided is large. When the flow rate of the working fluid 9 flowing through the flow path 6 is large in the second and subsequent stages, the impeller 5 in the second and subsequent stages may also be divided and the upstream blade 17 may be provided. Needless to say.

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Inner housing 4 Rotating shaft 5 Impeller 9 Working fluid 17 Upstream blade 18 Working fluid flow path 19 Compressed working fluid flow path 21 Impeller internal flow path 22 Suction port 26 First impeller part 27 Second impeller part 28 Downstream Side Hub 29 Downstream Blade 31 Crown Plate 32 Concave 33 First Key Groove 34 Upstream Hub 36 Convex 37 Second Key Groove 38 Third Key Groove 39 Key Piece 43 Return Flow 45 Downstream Crown Plate 46 Upstream Crown Plate 47 Return flow path

Claims (6)

  An impeller pivotally attached to a rotating shaft; and a housing that rotatably accommodates the impeller, wherein the impeller has a hub on which the rotating shaft is fitted, a plurality of blades provided on the hub, A crown plate provided on the blade, facing the hub over the entire circumference and forming a flow path in the impeller between the hub, and the impeller is a first impeller downstream in the axial direction. And the second impeller portion on the upstream side, the division is divided so that the first impeller portion and the second impeller portion include the hub and the blade, respectively, the first impeller portion and the second impeller portion A centrifugal compressor characterized in that the second impeller portion is integrated via the rotating shaft.   The division is performed such that the second impeller portion does not include the crown plate, and the upstream end of the crown plate is located downstream of the upstream end of the blade of the second impeller portion, 2. The centrifugal compressor according to claim 1, wherein the working fluid that has flowed between the crown plate and the second impeller portion is joined to the impeller flow path downstream from an upstream end of a blade of the second impeller portion.   The division is performed such that the first impeller portion and the second impeller portion include the hub, the blade, and the crown plate, respectively, and the crown plate of the first impeller portion and the second impeller portion of the first impeller portion are divided. The gap is formed between the crown plate, and the working fluid that flows between the housing and the crown plate flows through the gap and merges with the flow path in the impeller. Centrifugal compressor.   A convex portion is formed at the central portion of one of the hub of the first impeller portion and the hub of the second impeller portion, and a concave portion is formed at the other, and the convex portion and the concave portion can be fitted. The centrifugal compressor according to any one of claims 1 to 3, wherein the first impeller portion and the second impeller portion are integrated by fitting the convex portion and the concave portion.   First and second key grooves communicating with the hub of the first impeller portion and the hub of the second impeller portion are engraved, and a third key groove is engraved on the rotary shaft, The key piece is fitted over the second and third key grooves, and the rotary shaft, the first impeller portion, and the second impeller portion are integrated through the key piece. Item 5. The centrifugal compressor according to any one of Items 4 above.   The centrifugal compressor according to any one of claims 1 to 5, wherein the blade of the first impeller portion and the blade of the second impeller portion are parallel to a split surface of the hub.

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