JP2010265784A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor broadening an operation range and enhancing compression efficiency by sending a gas to impellers in a state in which the gas flow is uniformized as much as possible. <P>SOLUTION: The centrifugal compressor 1 includes a shaft 2, the plurality of impellers 3 compressing gas G by centrifugal force, and a casing 5 formed with a flow path 4 for letting the gas G flow from an upstream side to a downstream side. The flow path includes return passages 13 reversing the gas, which flows from a radially inward to a radially outward by the upstream impellers, to the radially inward, straight passages 20 letting the gas from the return passages flow from the radially outward to the radially inward, and induction passages 21 letting the gas from the straight passages go to the downstream impellers. The straight passage is provided with a return vane 25 dividing the same in a circumferential direction of the shaft, and a partition straightening plate 26 extending along an inner surface 20a of the straight passage continuing with an inner curved surface 13b of the return passage to divide the straight passage in an axial direction of the shaft. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor that compresses gas using centrifugal force.

  As is well known, a centrifugal compressor allows gas to pass through in the radial direction of a rotating impeller and compresses the gas using centrifugal force generated at that time. In this type of centrifugal compressor, there is known a multistage centrifugal compressor that includes multiple stages of impellers in the axial direction and compresses gas in stages (see Patent Document 1). The multistage centrifugal compressor will be briefly described with reference to the drawings.

As shown in FIG. 10, the centrifugal compressor 100 includes a casing 101 in which a suction port and a discharge port (not shown) are formed, a shaft 102 rotatably supported on the casing 101 via a bearing portion (not shown), A plurality of impellers 103 attached at predetermined intervals along the axial direction of the shaft 102, and a flow path 104 that connects the impellers 103 and distributes gas that is compressed in stages are provided.
In FIG. 10, the periphery of the first-stage and second-stage impellers 103 is illustrated.

  Each impeller 103 mainly includes a disk-shaped hub 103a that gradually increases in diameter toward one side (rear side) in the axial direction, a plurality of blades 103b that are radially attached to the hub 103a, and tips of the plurality of blades 103b. And a shroud 103c attached so as to cover the side in the circumferential direction.

The flow path 104 is mainly configured by a suction path 104a, a compression path 104b, a diffuser path 104c, and a return path 104d.
The suction passage 104 a converts the flow direction of the gas flowing from the straight passage into the axial direction of the shaft 102 and guides it toward the impeller 103. And a curved corner passage. The compression passage 104b is a passage defined by the blade mounting surface of the hub 103a and the inner wall surface of the shroud 103c facing the hub attachment surface. The diffuser passage 104c is a passage extending outward in the radial direction, and flows the gas compressed by the impeller 103 outward in the radial direction. The return passage 104d is a curved passage that changes the flow direction of the gas that has passed through the diffuser passage 104c to the inside in the radial direction and sends it to the suction passage 104a.

  Therefore, the gas flows in order of the second-stage suction passage 104a, the compression passage 104b, and the like after flowing in order through the first-stage suction passage 104a, the compression passage 104b, the diffuser passage 104c, and the return passage 104d. It is compressed in stages. In general, the diffuser passage 104c is provided with a plurality of diffuser vanes 105 that are arranged radially about the axis of the shaft 102 and divide the diffuser passage 104c in the circumferential direction. The straight passage of the suction passage 104a is provided with a plurality of return vanes 106 that are arranged radially and divide the straight passage in the circumferential direction, like the diffuser vane 105.

Japanese Patent Laid-Open No. 9-4599

However, in the return passage 104d of the centrifugal compressor 100, since it is necessary to rapidly change the gas flow direction, these curvatures are set large, and as a result, the gas flow in the flow path 104 is reduced. There is a problem of being easily disturbed.
That is, when the gas flows through the return path 104d having a large curvature, as shown in FIG. 11, a secondary flow such as separation occurs in the gas flow inside the return path 104d. Will be swung from the inside to the outside. As a result, at the outlet of the return passage 104d located on the straight passage side, the gas flow velocity distribution FR from the inside to the outside becomes non-uniform. Specifically, with respect to the flow velocity distribution FR at the exit of the return passage 104d, a low speed region having an extremely low flow velocity is generated inside the return passage 104d as compared with the outside.

Furthermore, as shown by the broken line arrow in FIG. 11, the gas enters the straight passage of the suction passage 104a while being swung from the inside to the outside of the return passage 104d. The non-uniformity of the flow velocity distribution FR increases, and the performance at the return vane 106 is degraded.
When the gas flows from the corner passage to the impeller 103 in such a non-uniform flow velocity distribution, the loss due to the secondary flow inside the impeller 103 increases and the compression efficiency decreases. It will lead to an unstable flow. This leads to the occurrence of surging, resulting in a disadvantage that the operating range of centrifugal compression becomes narrow as a result.

  The present invention has been made in view of such circumstances, and its purpose is to allow the gas flow to be sent to the impeller in a state where it is as uniform as possible, and to increase the operating range and increase the compression efficiency. It is intended to provide a high performance centrifugal compressor.

The present invention provides the following means in order to solve the problems and achieve the object.
A centrifugal compressor according to the present invention includes a shaft that is rotated around an axis, a plurality of impellers that are attached to the shaft so as to be arranged in an axial direction of the shaft, and compress gas by centrifugal force, and the shaft. And a casing formed with a flow path for allowing the gas to flow from the upstream side to the downstream side. The flow path flows from the radially inner side to the radially outer side by the upstream impeller. A curved return passage for reversing the gas flow direction radially inward, a straight passage through which the gas flowing from the return passage flows from radially outward to radially inward, and the straight passage A guide passage for directing the gas flowing from the downstream to the impeller, and the straight passage is arranged radially with the axis as the center. A plurality of return vanes that divide the trait passage in the circumferential direction of the shaft, and supported by the return vane so as to divide at least an upstream end portion of the straight passage located on the return passage side in the axial direction. A partition baffle plate extending radially inward from an upstream end portion of the straight passage is provided along an inner surface of the straight passage that is continuous with the inner curved surface of the return passage.

Note that the inner surface of the straight passage and the facing surface of the partition rectifying plate facing the straight passage do not have to be completely parallel, and may be inclined with respect to each other as long as the angle is minute. That is, the extending direction of the partition rectifying plate extending radially inward is slightly longer as the distance between the inner surface along the axial direction and the opposing surface is increased from the upstream end portion to the downstream end portion of the straight passage. It may be set to be shorter.
In the above configuration, at least the upstream end portion of the straight passage is divided into an inner passage connected to the inner portion of the return passage and an outer passage connected to the outer portion by the partition rectifying plate.

  In the above centrifugal compressor, since the impeller rotates with the rotation of the shaft, the gas flowing in the flow path can be compressed by centrifugal force. The gas compressed by the rotating upstream impeller flows from the radially inward side to the radially outward side, and then is converted into a radially inward flow by the return passage, and further, the straight passage and the guide passage To reach the impeller on the downstream side. The gas that has reached the downstream impeller is compressed by the downstream impeller and flows radially outward as described above. That is, in this centrifugal compressor, gas is compressed stepwise by a plurality of impellers.

According to the above centrifugal compressor, the secondary flow is generated in the gas flow inside the return passage, so that the gas flow swung from the inside of the return passage to the outside is caused by the partition rectifying plate at the stage of entering the straight passage. Shielded. That is, excessive gas can be prevented from flowing into the outer passage of the straight passage.
Furthermore, according to the centrifugal compressor, the width dimension of the inner passage along the axial direction does not change significantly over the longitudinal direction of the straight passage extending radially inward. For this reason, even if the gas flow velocity distribution at the upstream end of the straight passage becomes non-uniform based on the secondary flow of the gas inside the return passage, the flow of the gas flowing radially inward in the inner passage is rectified. Can be easily achieved. That is, the gas flow velocity distribution can be made uniform in the inner passage.
From the above, it is possible to make the flow velocity distribution of the gas guided from the straight passage to the impeller through the guide passage uniform. Therefore, the secondary flow loss can be reduced and the compression efficiency of the gas by the impeller can be increased. Further, it is possible to suppress the occurrence of surging in the impeller and widen the operation range of centrifugal compression.

In the centrifugal compressor, the partition rectifying plate is extended to the downstream end of the straight passage located on the induction passage side, and the straight passage is extended from the upstream end to the downstream end by the partition rectifying plate. It may be divided in the axial direction over the part.
According to this centrifugal compressor, the straight passage is divided into the inner passage and the outer passage from the upstream end portion to the downstream end portion by the partition baffle plate so as to rectify the gas flowing radially inward. The length of the inner passage is sufficiently secured so that the flow velocity of the gas entering the induction passage from the inner passage is large even if the flow velocity distribution of the gas entering the inner passage located at the upstream end of the straight passage is large. The distribution can be sufficiently uniformed and the secondary flow loss can be further reduced.

Further, when the partition current plate is extended to the downstream end of the straight passage, the guide passage converts the flow direction of the gas flowing from the straight passage from a radially inward direction to an axial direction. A curved corner passage that faces the impeller, and the partition rectifying plate is formed with a downstream extension extending from the downstream end of the straight passage into the corner passage, and the downstream extension is The curved shape of the corner passage may be curved.
According to this centrifugal compressor, the curved corner passage is divided into the inner side and the outer side by the downstream extension portion, so that the gas flow in the corner passage can be prevented from being disturbed by being shaken outside the corner passage. . That is, the gas passing through the curved corner passage from the downstream end portion of the straight passage can reach the impeller in a state where the flow velocity distribution is uniformed by being rectified by the downstream extension portion. As a result, the secondary flow loss can be further reduced, the gas compression efficiency in the impeller can be further increased, and the operation range of centrifugal compression can be further expanded.

Further, in the centrifugal compressor, an upstream extension extending from the upstream end of the straight passage into the return passage is formed on the partition rectifying plate, and the upstream extension is connected to the return passage. It may be curved following the curved shape.
According to this centrifugal compressor, since the curved return passage is divided into the inner side and the outer side by the upstream extension, it is possible to suppress the generation of a secondary flow in the gas flow in the return passage, and It is possible to prevent the gas flow from being swung from the inside to the outside of the return passage. Therefore, it is possible to further reduce the non-uniformity of the gas flow velocity distribution at the upstream end portion of the straight passage and further rectify the gas in the inner passage of the straight passage.

  According to the centrifugal compressor according to the present invention, since the gas flow can be sent to the impeller in a uniform state, it is possible to widen the operating range and increase the compression efficiency. Therefore, it is possible to provide a higher performance centrifugal compressor.

It is a simplified lineblock diagram of a centrifugal compressor showing a 1st embodiment concerning the present invention. It is the figure which expanded the impeller of the 1st step | paragraph and the 2nd step | paragraph impeller shown in FIG. It is the figure which looked at the return vane and partition rectification | straightening board which were shown in FIG. 2 from the upstream edge part side of a straight channel | path. It is a figure which shows the relationship between the flow-velocity distribution in the upstream edge part of the straight channel | path shown in FIG. 2, and arrangement | positioning of a partition baffle plate. FIG. 3 is a diagram showing the relationship between the cross-sectional area ratio of the inner passage and the cross-sectional area ratio of the outer passage in the straight passage shown in FIG. 2. It is a modification of the partition baffle plate shown in FIG. 2, and is a figure which shows the partition baffle plate extended in the return channel | path from the upstream edge part of a straight channel | path. It is a modification of the partition baffle plate shown in FIG. 2, and is a figure which shows the partition baffle plate extended in the corner channel | path from the downstream end part of the straight channel | path. It is a modification of the partition rectifying plate shown in FIG. 2, and is a view showing the partition rectifying plate extended from the upstream end portion and the downstream end portion of the straight passage into the return passage and the corner passage, respectively. It is a modification of the partition baffle plate shown in FIG. 2, and is a figure which shows the relationship between arrangement | positioning of the partition baffle plate in an upstream edge part, and the length of a partition baffle plate. It is a figure which shows an example of the conventional centrifugal compressor, Comprising: It is the figure which expanded the periphery of two impellers. It is a figure which shows the flow-velocity distribution of the process gas in the return path | pass exit shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Hereinafter, an embodiment according to the present invention will be described with reference to FIGS. 1 to 5. In the present embodiment, a multistage centrifugal compressor including a plurality of impellers will be described as an example of the centrifugal compressor.

  As shown in FIG. 1, the centrifugal compressor 1 of the present embodiment mainly compresses a process gas (gas) G using a shaft 2 that is rotated around an axis O and a centrifugal force that is attached to the shaft 2. The impeller 3 that supports the shaft 2 and a casing 5 that is formed with a flow path 4 that allows the process gas G to flow from the upstream side to the downstream side.

The casing 5 is formed so as to form a substantially cylindrical outline, and the shaft 2 is disposed so as to penetrate the center. Journal bearings 5a are provided at both ends of the casing 5 in the axial direction of the casing 5, and thrust bearings 5b are provided at one end. The journal bearing 5a and the thrust bearing 5b support the shaft 2 in a rotatable manner. That is, the shaft 2 is supported by the casing 5 via the journal bearing 5a and the thrust bearing 5b.
Further, a suction port 5c through which the process gas G flows from the outside is provided on one end side in the axial direction of the casing 5, and a discharge port 5d through which the process gas G flows out to the outside is provided at the other end side. In the casing 5, an internal space that communicates with each of the suction port 5 c and the discharge port 5 d and repeats the diameter reduction and the diameter expansion is provided. This internal space functions as a space for accommodating the impeller 3 and also functions as the flow path 4. That is, the suction port 5 c and the discharge port 5 d communicate with each other via the impeller 3 and the flow path 4.

A plurality of impellers 3 are arranged at intervals in the axial direction of the shaft 2. In the illustrated example, six impellers 3 are provided, but it is sufficient that at least two impellers 3 are provided. As shown in FIGS. 1 and 2, each impeller 3 mainly includes a substantially disc-shaped hub 3a that gradually expands in diameter toward the discharge port 5d side, and a plurality of the impellers 3 that are radially attached to the hub 3a and arranged in the circumferential direction. Blades 3b and a shroud 3c attached so as to cover the tip ends of the plurality of blades 3b in the circumferential direction.
FIG. 2 illustrates the periphery of the fourth stage impeller 3.

  The flow path 4 is formed so as to advance in the axial direction while meandering in the radial direction of the shaft 2 and to connect the impellers 3 so that the process gas G is compressed stepwise by the plurality of impellers 3. . More specifically, the flow path 4 is mainly configured by a suction passage 10, a compression passage 11, a diffuser passage 12, and a return passage 13.

  The suction passage 10 is a passage that changes the direction of the process gas G to the axial direction of the shaft 2 immediately before the impeller 3 after flowing the process gas G from the radially outer side to the radially inner side. Specifically, a straight straight passage 20 through which the process gas G flows from the radially outer side toward the radially inner side, and the flow direction of the process gas G flowing from the straight passage 20 is axially directed from the radially inner side. A curved corner passage (guide passage) 21 that changes the direction and directs the process gas G toward the impeller 3 is formed.

  The straight passage 20 includes an inner surface 20a of a substantially disc-shaped partition wall member 5e integrally attached to the casing 5, and an outer surface 20b of the extending portion 5f integrally attached to the casing 5 and extending radially inward. It is defined by being surrounded by. Here, in the straight passage 20 of the suction passage 10 that directs the process gas G to the first stage impeller 3, the radially outer side thereof is communicated with the suction port 5c.

On the other hand, the radially outer side of the straight passage 20 of the suction passage 10 located between the two impellers 3 along the flow direction of the process gas G communicates with the return passage 13. Further, the width dimension of the straight passage 20 along the axial direction of the shaft 2 is set so as to gradually increase from the radially outer side toward the radially inner side.
Further, the straight passage 20 positioned between the two impellers 3 is provided with a plurality of return vanes 25 that are arranged radially about the axis O and divide the straight passage 20 in the circumferential direction of the shaft 2. The return vane 25 shown in FIG. 2 is formed from the upstream end of the straight passage 20 located on the return passage 13 side to the downstream end of the straight passage 20 located on the corner passage 21 side.

Further, as shown in FIGS. 2 and 3, the straight passage 20 provided with the return vane 25 is provided with a partition rectifying plate 26 that is supported by the return vane 25 and divides the straight passage 20 in the axial direction of the shaft 2. It has been.
The partition current plate 26 extends radially inward from the upstream end portion of the straight passage 20 along the inner surface 20a of the straight passage 20 and extends to the downstream end portion of the straight passage 20 located on the corner passage 21 side. Has been. The position of the front edge of the partition current plate 26 coincides with the front edge of the return vane 25 located on the return passage 13 side, and the position of the rear edge is on the rear edge of the return vane 25 located on the corner passage 21 side. Match.

In FIG. 2, the inner surface 20a of the straight passage 20 and the facing surface 26a of the partition rectifying plate 26 facing the straight passage 20 are parallel to each other. Good. That is, the extending direction of the partition rectifying plate 26 extending radially inward is such that the distance between the inner surface 20a and the opposing surface 26a along the axial direction increases from the upstream end portion to the downstream end portion of the straight passage 20. Alternatively, it may be set to be slightly longer or shorter.
Therefore, the partition current plate 26 divides the straight passage 20 in the axial direction of the shaft 2 from the upstream end portion to the downstream end portion. The straight passage 20 is divided into an inner passage 27 between the inner surface 20 a and the partition rectifying plate 26, and an outer passage 28 between the outer surface 20 b and the partition rectifying plate 26.

  The corner passage 21 is a passage continuously provided at the downstream end portion of the straight passage 20, and is surrounded by the curved wall surface 21a of the partition wall member 5e connected to the inner side surface 20a and the distal end curved wall surface 21b of the extending portion 5f connected to the outer side surface 20b. Is defined. The corner passage 21 is curved so as to be parallel to the axial direction of the shaft 2 from the entrance side to the exit side. The corner passage 21 plays a role of sending out to the impeller 3 (downstream impeller) after changing the flow direction of the process gas G as described above. Further, the corner passage 21 is designed to be curved in an arc shape or an ellipse shape, and to be curved with a curvature equal to or less than a specified value. Thereby, when the process gas G passes through the corner passage 21, the direction does not change suddenly but changes gradually.

The compression passage 11 is a passage for compressing the process gas G sent from the suction passage 10 in the impeller 3, and is defined by being surrounded by the blade mounting surface of the hub 3a and the inner wall surface of the shroud 3c. ing.
The radially inner side of the diffuser passage 12 communicates with the compression passage 11 and is defined by being surrounded by the diffuser front wall 12a of the casing 5 and the diffuser rear wall 12b of the partition wall member 5e. The diffuser passage 12 serves to flow the process gas G compressed by the impeller 3 outward in the radial direction. The radially outer side of the diffuser passage 12 communicates with the return passage 13, but the diameter of the impeller 3 (sixth stage impeller 3 in FIG. 1) located on the most downstream side of the flow path 4. The diffuser passage 12 that extends outward in the direction communicates with the discharge port 5d.
The diffuser passage 12 is provided with a plurality of diffuser vanes 29 that are arranged radially about the axis O and divide the diffuser passage 12 in the circumferential direction of the shaft 2.

The return passage 13 is formed in a substantially U-shaped cross section, and is surrounded by an inverted wall surface 13a of the casing 5 positioned between adjacent extending portions 5f and an outer peripheral wall surface (inner curved surface) 13b of the partition wall member 5e. It is made. That is, the reverse wall surface 13 a of the partition wall member 5 e forms the outer curved surface of the return passage 13, and the outer peripheral wall surface 13 b forms the inner curved surface of the return passage 13. The upstream end side of the return passage 13 communicates with the diffuser passage 12, and the downstream end side communicates with the straight passage 20 of the suction passage 10. In addition, the inner side surface 20a which defines the straight path 20 mentioned above is continued to the outer peripheral wall surface 13b of the return path 13, and the outer side surface 20b is continued to the inversion wall surface 13a. Further, the inner passage 27 of the straight passage 20 divided by the partition rectifying plate 26 is continuous with the inner portion of the return passage 13, and the outer passage 28 of the straight passage 20 is continuous with the outer portion of the return passage 13.
The return passage 13 reverses the flow direction of the process gas G that has flowed radially outward through the diffuser passage 12 by the impeller 3 (upstream impeller 3) to the straight passage 20. Sending out.

Next, the compression of the process gas G by the centrifugal compressor 1 configured as described above will be described.
When each impeller 3 rotates together with the shaft 2, the process gas G that has flowed into the flow path 4 from the suction port 5c, the suction passage 10, the compression passage 11, the diffuser passage 12, and the return passage of the first stage impeller 3 from the suction port 5c. After flowing in the order of 13, the suction passage 10 and the compression passage 11 of the second stage impeller 3 flow in this order. And the process gas G which flowed to the diffuser channel | path 12 immediately after the impeller 3 located in the most downstream side of the flow path 4 flows outside from the discharge port 5d.
The process gas G is compressed by each impeller 3 while flowing through the flow path 4 in the order described above. That is, in the centrifugal compressor 1, the process gas G is compressed stepwise by the plurality of impellers 3, and thereby a large compression ratio can be easily obtained.

By the way, when the process gas G flows through the return passage 13 having a large curvature, a secondary flow is generated in the flow of the process gas G inside the return passage 13 so that the process gas G flows from the inside of the return passage 13. It is swung outward.
Here, since the straight passage 20 is provided with the partition rectifying plate 26, the flow of the process gas G swung from the inside of the return passage 13 to the outside enters the upstream end portion of the straight passage 20 from the return passage 13. In FIG. That is, the partition baffle plate 26 prevents excessive process gas G from flowing into the outer passage 28 of the straight passage 20.

Further, when the process gas G flows through the return passage 13, a secondary flow is generated in the flow of the process gas G inside the return passage 13, so that the flow velocity distribution of the process gas G at the upstream end of the straight passage 20 is increased. It becomes non-uniform.
Specifically, as shown in FIG. 4, the flow velocity distribution of the process gas G is not uniform between the vicinity of the inner surface 20 a and the vicinity of the outer surface 20 b at the upstream end of the straight passage 20. The flow rate of the process gas G on the inner surface 20a side is extremely low. Note that the region where the flow rate of the process gas G is extremely low (low-speed region) is indicated by the symbol FR1 in FIG. Also, the two-point difference line indicated by the reference symbol FR2 in FIG. 4 shows the flow velocity distribution in the vicinity of the inner side surface 20a that is assumed to be uniform between the vicinity of the inner side surface 20a and the vicinity of the outer side surface 20b. Yes.

  Thus, the process gas G having a non-uniform flow velocity distribution enters the inner passage 27 of the straight passage 20, but the width dimension of the inner passage 27 along the axial direction is the longitudinal direction of the straight passage 20 extending radially inward. Therefore, the process gas G flowing inward in the radial direction in the inner passage 27 can be easily rectified. That is, the flow velocity distribution of the process gas G in the inner passage 27 can be made uniform.

As described above, according to the centrifugal compressor 1, the corner passage 21 is formed from the downstream end portion of the straight passage 20 by equalizing the flow velocity distribution of the process gas G that flows radially inward in the inner passage 27. Thus, the flow velocity distribution of the process gas G guided to the impeller 3 can be made uniform. In particular, the partition rectifying plate 26 divides the straight passage 20 into an inner passage 27 and an outer passage 28 from the upstream end portion to the downstream end portion thereof, so that the inner passage 27 located at the upstream end portion of the straight passage 20 Even if the non-uniformity of the flow velocity distribution of the process gas G entering is large, the flow velocity distribution of the process gas G entering the corner passage from the inner passage 27 can be sufficiently uniform.
For this reason, it is possible to increase the compression efficiency to reduce the secondary flow loss and increase the compression efficiency of the process gas G by the impeller 3. Furthermore, it is possible to suppress the occurrence of surging in the impeller 3 and to widen the operating range of the centrifugal compression. Therefore, it is possible to provide a higher-performance centrifugal compressor 1.

The arrangement of the partition rectifying plate 26 at the upstream end portion of the straight passage 20 is more preferably in consideration of the flow velocity distribution of the process gas G at the upstream end portion of the straight passage 20. Specifically, as shown in FIG. 4, in addition to the process gas G in the low speed region FR1, the partition rectification is performed so that part of the process gas G flowing on the outer surface 20b side from the low speed region FR1 also enters the inner passage 27. It is preferable to arrange the leading edge of the plate 26.
In this case, when the process gas G flowing out from the inner passage 27 and the outer passage 28 joins at the rear edge of the partition rectifying plate 26, the difference in flow velocity of the process gas G flowing out from the inner passage 27 and the outer passage 28 is reduced. Alternatively, it can be eliminated. Therefore, the flow of the process gas G can be prevented from being disturbed in the passage on the downstream side of the partition rectifying plate 26 such as the corner passage 21.

Further, the arrangement of the partition rectifying plate 26 with respect to the straight passage 20 is preferably set so that the rate of increase of the process gas G in the inner passage 27 is larger than the rate of increase of the process gas G in the outer passage 28.
Specifically, as shown in FIG. 5, the process gas G flows from the radially outer side to the radially inner side in the inner passage 27 and the outer passage 28 of the straight passage 20, and therefore flows into the straight passage 20. The flow rate of the processed gas G increases in the inner passage 27 and the outer passage 28, respectively. The speed increase rate described above is represented by the ratio of the flow rate of the process gas G at the upstream end of the straight passage 20 and the flow rate of the process gas G at the downstream end in each of the inner passage 27 and the outer passage 28. Is.

Further, the rate of increase of the process gas G flowing inward in the radial direction in the inner passage 27 is such that the inlet side sectional area A1 of the inner passage 27 at the upstream end of the straight passage 20 and the inner passage 27 at the downstream end of the straight passage 20 Is proportional to the cross-sectional area ratio (A1 / A2) to the outlet side cross-sectional area A2. Further, the rate of acceleration of the process gas G flowing radially inward in the outer passage 28 is also the same as in the case of the inner passage 27, and the inlet-side sectional area B1 of the outer passage 28 and the outlet-side sectional area B2 of the outer passage 28. And the cross-sectional area ratio (B1 / B2).
Therefore, it is preferable to arrange the partition rectifying plate 26 so that the cross-sectional area ratio (A1 / A2) of the inner passage 27 is set larger than the cross-sectional area ratio (B1 / B2) of the outer passage 28.

  When the arrangement of the partition rectifying plate 26 is set in this way, the average flow velocity of the process gas G flowing into the inner passage 27 at the upstream end of the straight passage 20 is higher than the average flow velocity of the process gas G flowing into the outer passage 28. Even if it is smaller, the flow of the process gas G in the inner passage 27 is increased more rapidly than in the outer passage 28. Thereby, when the process gas G flowing out from the inner passage 27 and the outer passage 28 joins at the rear edge of the partition rectifying plate 26, the difference in flow velocity of the process gas G flowing out from the inner passage 27 and the outer passage 28 is reduced, or It can be eliminated. Therefore, the flow of the process gas G can be prevented from being disturbed on the downstream side of the partition rectifying plate 26 such as the corner passage 21.

  In the above-described embodiment, the partition rectifying plate 26 that facilitates rectification of the process gas G is disposed only in the straight passage 20, but for example, as shown in FIG. 26 may be formed with an upstream extension 33 extending from the upstream end of the straight passage 20 into the return passage 13. The upstream extension 33 is curved following the curved shape of the return passage 13. That is, the upstream extension 33 has a curved shape centered on the same center of curvature as the return passage 13.

  According to the centrifugal compressor 31 having this configuration, the curved return passage 13 is divided into the inner side and the outer side by the upstream extension portion 33, and the process gas G flows along the curve of the corner passage 21 to rectify. Therefore, it is possible to suppress the generation of the secondary flow in the flow of the process gas G in the return passage 13 and to suppress the flow of the process gas G in the return passage 13 from being swung from the inside of the return passage 13 to the outside. . Therefore, the non-uniformity in the flow velocity distribution of the process gas G at the upstream end of the straight passage 20 can be kept low, and the process gas G in the inner passage 27 of the straight passage 20 can be further rectified.

  Further, for example, as shown in FIG. 7, a downstream rectification portion 43 extending from the downstream end portion of the straight passage 20 into the corner passage 21 may be formed on the same partition rectifying plate 26 as in the above embodiment. . The downstream extension 43 is curved following the curved shape of the corner passage 21. That is, the downstream extension 43 has a curved shape with the same center of curvature as the corner passage 21.

According to the centrifugal compressor 41 having this configuration, the curved corner passage 21 is divided into the inner side and the outer side by the downstream extension 43, and the process gas G flows along the curvature of the corner passage 21 to rectify. Therefore, the flow of the process gas G in the corner passage 21 can be prevented from being disturbed by being swung to the outside of the corner passage 21. That is, even if the corner passage 21 from the downstream end portion of the straight passage 20 to the impeller 3 is curved, the process gas G passing through the corner passage 21 is rectified by the downstream extension 43 so that its flow velocity distribution is The impeller 3 can be reached in a uniform state. Thereby, the compression efficiency of the process gas G in the impeller 3 can be further increased, and the operation range of centrifugal compression can be further expanded.
Note that the partition rectifying plate 26 is not limited to the formation of only one of the upstream extension 33 shown in FIG. 6 and the downstream extension 43 shown in FIG. 7. For example, the centrifugal compressor shown in FIG. Like 51, both the upstream extension part 33 and the downstream extension part 43 may be formed.

  Further, the partition rectifying plate 26 is not limited to dividing the straight passage 20 from the upstream end portion to the downstream end portion, and as shown in FIG. 9, at least the upstream end portion of the straight passage 20 located on the return passage 13 side. Is required to extend radially inward from the upstream end portion of the straight passage 20 along the inner surface 20a of the straight passage 20 so as to be divided. That is, the rear edge of the partition rectifying plate 26 may not reach the downstream end of the straight passage 20.

In this case, the extending length L1 of the partition rectifying plate 26 extending radially inward from the upstream end portion of the straight passage 20 is equal to the inner side surface 20a along the axial direction at the upstream end portion of the straight passage 20 and the partition rectifying plate. It is more preferable that the distance L2 between the opposing surface 26a of the 26 and the width L2 of the inner passage 27 at the upstream end of the straight passage 20 is three times or more. Even if the flow velocity distribution of the process gas G entering the inner passage 27 is not uniform, the extension length L1 of the partition rectifying plate 26 is three times or more the width dimension L2 of the inner passage 27. The flow is sufficiently rectified while passing through the inner passage 27, and the flow velocity distribution of the process gas G can be sufficiently uniformed in the inner passage 27.
9 is formed with the upstream extension 33 shown in FIG. 6, for example, the non-uniformity in the flow velocity distribution of the process gas G entering the inner passage 27 can be kept low. Therefore, even if the extension length L1 of the partition rectifying plate 26 is set to be three times or less the width dimension L2 of the inner passage 27, the flow velocity distribution of the process gas G in the inner passage 27 can be sufficiently uniformed.

  In addition, in the said embodiment and all the modifications, although the upstream edge part of the straight channel | path 20 divided | segmented into the axial direction by the partition current plate 26 has shown the boundary with the downstream edge of the return channel | path 13, it is restricted to this. In other words, the centrifugal compressor of the present invention includes a region spaced radially inward from the downstream end of the return passage 13. Therefore, for example, when the front edge of the return vane 25 located on the return passage 13 side is located radially inward from the downstream end of the return passage 13, the front edge of the partition rectifying plate 26 located on the return passage 13 side. May be arranged at the boundary between the straight passage 20 and the return passage 13 as in the above embodiment, but may coincide with the front edge of the return vane 25, for example.

  Further, the downstream end portion of the straight passage 20 divided in the axial direction by the partition rectifying plate 26 is not limited to the boundary with the upstream end of the corner passage 21 as in the case of the upstream end portion. The compressor includes a region spaced radially outward from the upstream end of the corner passage 21. Therefore, for example, when the trailing edge of the return vane 25 located on the corner passage 21 side is located radially outward from the upstream end of the corner passage 21, the trailing edge of the partition rectifying plate 26 located on the corner passage 21 side. May be arranged at the boundary between the straight passage 20 and the corner passage 21 as in the above embodiment, but may coincide with the rear edge of the return vane 25, for example.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

G ... Process gas (gas)
O ... axis 1, 31, 41, 51 ... centrifugal compressor 2 ... shaft 3 ... impeller 4 ... flow path 5 ... casing 13 ... return passage 13b ... outer peripheral wall surface (inner curved surface)
20 ... Straight passage 20a ... Inner side 21 ... Corner passage (guidance passage)
25 ... Return vane 26 ... Partition current plate 33 ... Upstream extension 43 ... Downstream extension

Claims (4)

A shaft that is rotated about an axis, a plurality of impellers that are attached to the shaft so as to be arranged in the axial direction of the shaft, and compresses the gas by centrifugal force; And a casing formed with a flow path for flowing from the upstream side to the downstream side,
The flow path flows from the return path having a curved shape that reverses the flow direction of the gas flowing radially inward from the radially inward by the upstream impeller and radially inward. A straight passage that allows the gas to flow from radially outward to radially inward, and a guide passage that directs the gas flowing from the straight passage toward a downstream impeller, and
In the straight passage, a plurality of return vanes that are arranged radially about the axis and divide the straight passage in the circumferential direction of the shaft, and an upstream end portion of the straight passage that is located at least on the return passage side Extending inward in the radial direction from the upstream end of the straight passage along the inner surface of the straight passage that is supported by the return vane and continues to the inner curved surface of the return passage. A centrifugal compressor characterized in that a partition rectifying plate is provided. The partition current plate is extended to the downstream end of the straight passage located on the guide passage side,
The centrifugal compressor according to claim 1, wherein the straight passage is divided in the axial direction from the upstream end portion to the downstream end portion by the partition rectifying plate. The guide passage is composed of a curved corner passage that changes the flow direction of the gas flowing from the straight passage from a radially inward to an axial direction and directs it toward the impeller,
The partition rectifier plate is formed with a downstream extension extending from the downstream end of the straight passage into the corner passage,
The centrifugal compressor according to claim 2, wherein the downstream extension portion is curved following the curved shape of the corner passage. An upstream extension extending from the upstream end of the straight passage into the return passage is formed on the partition rectifying plate,
The centrifugal compressor according to any one of claims 1 to 3, wherein the upstream extension portion is curved following the curved shape of the return passage.

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