JPH09273495A - Multistage centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an energy loss accompanying interstage extraction of pressure rising gas. SOLUTION: A collecting pipe 15 is arranged on the diameter directional outer circumference side beyond a bend part 11 of a return passage, and the collecting pipe 15 is connected to an extraction port 13 via a ring type extraction passage 14. In this constitution, an extraction flow 18 diverges from a main flow 19 in an outlet part of a diffuser 10 and flows into the collecting pipe after its speed is sufficiently reduced in the extraction passage 14. Therefore, a confluence loss with a flow inside the collecting pipe 15 and a friction loss inside the collecting pipe 15 can be reduced, so that performance of the multistage centrifugal compressor can be greatly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage centrifugal compressor, and more particularly to a high-performance multi-stage centrifugal compressor which is used for pressurization in a refrigeration process of plant equipment or the like, and in which gas is extracted from between stages. It is a thing.

[0002]

2. Description of the Related Art Generally, there is a demand for supplying gas having a plurality of kinds of discharge pressures in plant equipment and the like. As a multi-stage centrifugal compressor to deal with this, a casing having a suction port, a discharge port, and an intermediate discharge port, a rotary shaft provided in the casing, and a multi-stage impeller fixed to the rotary shaft, Each of the impellers, each having a diffuser arranged on the outer circumference in the radial direction of the impeller, and a return flow passage provided downstream of the diffuser, and a gas pressurized by the impeller is passed through the diffuser and the return flow passage. It is designed to lead to the next stage impeller. Each stage is composed of an impeller, a diffuser arranged downstream of the impeller, and a return flow passage including a curved portion (hereinafter referred to as a bend portion) that moves from the diffuser to the return passage and a blade portion (channel portion). There is.

In the multistage centrifugal compressor having such a structure, when a part of the gas flowing in the intermediate stage is extracted from the compressor, it is conventionally disclosed, for example, in Japanese Utility Model Laid-Open No. 64-51794. At the outlet of the diffuser, that is, at the inlet of the bend, a circumferential slit-shaped extraction port is provided, and immediately after that, a collecting pipe is configured to guide the extracted gas to the intermediate discharge nozzle. Here, the branch portion between the main flow and the extraction flow is formed in a wedge shape with an acute angle, and the collecting pipe is located between the diffuser at the stage for performing extraction and the return flow passage at the preceding stage.

[0004]

However, in the multistage centrifugal compressor for performing the interstage extraction as in the above-mentioned prior art,
Since the collecting pipe is arranged immediately after the diffuser, the gas flowing into the collecting pipe is not yet sufficiently decelerated,
When the flow merges with the flow in the collecting pipe, there is a problem that the kinetic energy of the flow, that is, a large energy loss proportional to the square of the inflow velocity, occurs, and the performance of the compressor deteriorates.

Further, in the multistage centrifugal compressor for performing the interstage extraction as in the above-mentioned prior art, the branch portion between the main flow and the extraction flow is formed in a wedge shape with an acute angle, and it has a certain specific point (design point). In (), smooth extraction was possible. However, in reality, the flow rate ratio between the main flow and the extraction flow may change depending on the operating conditions of the plant, etc., and the flow rate and the passage area do not match at the branching point, and either the main flow or the extraction flow undergoes rapid acceleration. , The other undergoes a sudden slowdown. In such a case, if there is a sharp corner at the branch portion, there is a problem that a contraction flow or separation occurs, which causes a large loss, which deteriorates the performance of the compressor.

The present invention has been made to solve the above-mentioned problems of the prior art. The first object of the present invention is to extract a part of the gas pressurized by the centrifugal impeller from the interstage. In a multi-stage centrifugal compressor provided with an extraction port and a collecting pipe that collects the flow of the extracted gas and guides it to an intermediate discharge nozzle, it is possible to reduce energy loss due to the inter-stage extraction of the boosted gas,
It is to provide a high-performance multistage centrifugal compressor.

A second object of the present invention is to collect an annular extraction port for extracting a part of the gas pressurized by the centrifugal impeller from between the stages and a flow for the extracted pressurized gas to guide it to the intermediate discharge nozzle. In a multi-stage centrifugal compressor equipped with a pipe, high performance in which no contraction or separation occurs at a portion where the flow of the boosted gas collides with a branch portion between the extraction flow and a main flow guided to the centrifugal impeller of the next stage. To provide a simple multi-stage centrifugal compressor.

[0008]

In order to achieve the above first object, the structure of the first invention relating to the multistage centrifugal compressor of the present invention is a casing having a suction port, a discharge port and an intermediate discharge port. And a rotating shaft provided in the casing,
The multistage impeller fixed to the rotating shaft, a diffuser arranged on the outer circumference in the radial direction of the impeller for each of the impellers, and a return flow passage provided downstream of the diffuser, the impeller An annular extraction port for extracting a part of the gas boosted by the impeller from between the stages, which guides the gas boosted by the gas to the impeller of the next stage through the diffuser and the return flow path; In the multistage centrifugal compressor having a collecting pipe for collecting the flow of the pressurized gas and guiding it to the intermediate discharge port, an annular extraction flow path is provided between the diffuser and the collecting pipe.

More specifically, the collecting pipe is provided on the outer peripheral side in the radial direction with respect to the curved portion that moves from the diffuser to the return flow path, and the collecting pipe is seen in the direction of the rotation axis thereof. It is formed so as to be located between the return flow passage and the next-stage diffuser or between the diffuser and the previous return flow passage. Further, the extraction passage is formed so that the passage width increases from the inlet to the outlet. Furthermore, a plurality of guide vanes are provided in the extraction flow path.

That is, according to the multistage centrifugal compressor according to the first aspect of the present invention, the annular extraction port for extracting a part of the gas pressurized by the centrifugal impeller from between the stages and the flow of the extracted gas are collected. In the structure provided with the collecting pipe leading to the intermediate discharge nozzle, the means for decelerating the extraction flow, which is composed of an annular extraction flow path or the like, is provided between the extraction port and the collecting pipe, so that it flows into the collecting pipe. It is possible to sufficiently decelerate the gas and then combine it with the flow in the collecting pipe, which reduces energy loss at the time of merging, and thus
It is possible to realize a high-performance multistage centrifugal compressor.

Further, in order to achieve the second object,
The configuration of the second invention relating to the multi-stage centrifugal compressor of the present invention is a casing having a suction port, a discharge port, and an intermediate discharge port, a rotary shaft provided in the casing, and fixed to the rotary shaft. A multistage impeller, a diffuser arranged for each of these impellers on the outer circumference in the radial direction of the impeller, and a return passage provided downstream of the diffuser, and the gas pressurized by the impeller is provided in the diffuser. And an annular extraction port for guiding a part of the gas boosted by the impeller from between the stages and a flow of the extracted boosted gas, which guides the impeller of the next stage through the return flow path. In a multi-stage centrifugal compressor provided with a collecting pipe leading to an intermediate discharge port, a portion where the flow of the boosted gas collides in a branch portion between an extraction flow extracted from between stages and a main flow introduced to an impeller of the next stage. Rounded It is obtained by forming a blunt shape to.

According to the multistage centrifugal compressor according to the second aspect of the present invention, the annular extraction port for extracting a part of the gas pressurized by the centrifugal impeller from between the stages, and the flow of the extracted gas are collected and the intermediate discharge is performed. In the structure with the collecting pipe leading to the nozzle, the portion where the flow of the boosting gas collides with the branch of the extraction flow and the main flow guided to the centrifugal impeller of the next stage has a rounded and blunt shape. Due to the configuration, even if the flow rate ratio of the main flow and the extraction flow changes due to the operating conditions of the plant, contraction or separation does not occur, thereby reducing the energy loss at the time of branching, and thus achieving high performance. It is possible to realize a multi-stage centrifugal compressor.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS.
First, an embodiment of the first invention will be described with reference to FIGS. [Embodiment 1] FIG. 1 is a schematic configuration diagram in a first embodiment of a multistage centrifugal compressor adopting an interstage extraction flow channel structure to which the present invention is applied, and FIG. 2 is a multistage shown in FIG. It is a principal part longitudinal cross-sectional view which shows the internal structure of 1st Embodiment of a centrifugal compressor.

A multistage centrifugal compressor 100 shown in FIG. 1 includes a casing 1, a rotating shaft 2 provided in the casing, and five stages of impellers 3a, 3b, 3 attached to the rotating shaft.
c, 3d, 3e. In addition, the casing 1 has 1
A suction nozzle 5 relating to a suction port for supplying gas to the impeller 3a of the second stage, and an impeller 3b of the second stage via the impeller 3a.
An intermediate discharge nozzle 6 related to an intermediate discharge port that extracts a part of the gas whose pressure has been increased by the step from the outlet of the impeller 3b to the inlet of the third-stage impeller 3c and discharges it to the outside of the casing.
A final discharge nozzle 7 is provided which is a discharge port that guides the boosted pressure discharged from the final stage impeller 3e through the third and fourth stage impellers 3c and 3d to the outside of the compressor.

Next, referring to FIG. 2, the impellers 3b and 3c and the intermediate discharge nozzle 6 in the first embodiment shown in FIG.
The internal structure of the compressor in the vicinity is shown. In FIG. 2, the rotary shaft 2
The rotary sleeve 4 and the impeller 3 are fitted and fixed to the. A diffuser 10 is arranged on the outer circumference of the impeller 3 in the circumferential direction, and a curved portion, that is, U, which moves from the diffuser 10 to the channel portion 12 is provided downstream of the diffuser 10.
A return flow passage 21 is provided, which is composed of a bend portion 11 curved in a V shape and a channel portion 12 provided with a guide blade 20 having a circular blade row shape.

An extraction port 13 for extracting a part of the gas pressurized by the impeller 3b is provided in the vicinity of the connection between the diffuser 10 and the bend section 11, and the extraction port 13 is provided downstream of the extraction port 13. An annular extraction flow path 14 for guiding the extracted extraction flow 18 to the collecting pipe 15 and an intermediate discharge nozzle 6 for discharging the extracted flow collected by the collecting pipe 15 to the outside of the casing 1 are provided.

Here, the flow 17 of the working gas supplied from the suction nozzle 5 passes through the pre-stage impeller 3a, the pre-stage diffuser and the return flow passage, and then is pressurized by the impeller 3b, and is extracted downstream of the diffuser 10. It is branched into an extraction flow 18 flowing into the flow passage 14 and a main flow 19 flowing into the return flow passage 21.

In general, the flow immediately after the impeller has not only a meridional velocity component but also a large circumferential velocity component, which is still large even after being subjected to the deceleration action by the diffuser, and the gas is still present. It has a large flow rate. Therefore, in the conventional technology in which the collecting pipe is arranged immediately after the diffuser, in order to match the extraction flow and the flow in the collecting pipe, it is necessary to increase the swirling flow velocity in the collecting pipe, and therefore, the friction loss in the collecting pipe is increased. There was a big problem. Further, since the absolute value of the flow velocity is large, there is a problem that a large mixing loss occurs at the time of merging even if the flow velocity in the collecting pipe is mismatched at a small rate.

On the other hand, as shown in FIG. 2, in the first embodiment, the collecting pipe 15 is arranged on the radially outer side of the bend portion 11 of the return flow passage 21, and the collecting pipe 15 and the extraction port are arranged. An annular extraction flow path 14 is connected between the three. With such a configuration, the extraction flow is branched from the main flow 19 at the outlet portion of the diffuser 10, and is further subjected to the same deceleration action as the diffuser in the extraction flow path 14, and thus, to the collecting pipe 15. At the time of inflow, the speed is sufficiently reduced. Therefore, the swirling flow velocity in the collecting pipe 15 can be reduced, and the friction loss in the collecting pipe 15 can be reduced. At this time, in order to reduce the flow velocity in the collecting pipe 15, it is necessary to increase the cross-sectional area of the collecting pipe 15. However, in the present embodiment, the collecting pipe 15 has the bend portion 11 of the return passage 21.
Since it is located on the outer peripheral side in the radial direction, the collecting pipe having a large cross-sectional area can be arranged without increasing the axial length of the compressor.

Further, according to the present embodiment, the collecting pipe 15
Since the absolute value of the flow velocity flowing out to is small, even if there is some mismatch with the flow velocity in the collecting pipe 15, the mixing loss at the time of merging is small. From this, further, as the structure of the collecting pipe 15,
Not only a scroll structure that changes the cross-sectional area in the circumferential direction to make the flow velocity in the collecting pipe 15 constant, but also a collector structure having a constant cross-sectional area in the circumferential direction can be adopted. In this case, the shape of the casing is simple. And the manufacturing cost can be reduced.

In this embodiment, the collecting pipe 1
Although the cross-sectional shape of 5 is rectangular, it may have a circular shape or an arbitrary cross-sectional shape, and a scroll structure or a collector structure can be adopted for any of these cross-sectional shapes. Is.

In the present embodiment, the configuration is shown in which extraction is performed from the stage from the outlet of the second-stage impeller 3b to the inlet of the third-stage impeller 3c. Any stage of the first stage impeller can be used. Especially, when performing extraction between the first stage and the second stage, by arranging the collecting pipe radially outside the bend part, There is also an advantage that it is possible to avoid interference with the suction flow path occupying a large space.

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of an essential part showing the internal structure of the multistage centrifugal compressor according to the embodiment of FIG. FIG. 3 is an enlarged view particularly showing the branch portion of the extraction flow and the main flow and the vicinity of the collecting pipe.
2 that are the same as those in FIG. 2 are the same as those in the previous embodiment, and therefore their explanations are omitted. Also in the embodiment shown in FIG. 3, the collecting pipe 15 is arranged radially outward of the bend portion 11 of the return flow passage, and the collecting pipe 15 and the extraction port 13 are connected by an annular extraction flow passage 14A. There is. Here, the extraction flow passage 14A is formed so that the flow passage width gradually increases from the inlet portion toward the outlet portion.

With the structure of the embodiment shown in FIG. 3, the extraction flow 18 is branched from the main flow 19 at the outlet of the diffuser 10 and then in the extraction passage 14A in the first embodiment. Receives the same deceleration action as
Since the flow passage width increases from the inlet portion to the outlet portion of the extraction passage, the deceleration is further performed particularly with respect to the meridional velocity component. Generally, most of the kinetic energy due to the meridional velocity component of the flow that flows into the collecting pipe 15 is lost. Therefore, as in the present embodiment, the meridional velocity component must be decelerated and converted into pressure energy. Has a large effect of reducing energy loss accompanying extraction.

In the present embodiment, as a means for expanding the flow passage width of the extraction flow passage, among the flow passage walls constituting the extraction flow passage 14A, the front wall is inclined in a taper shape. This may be such that the wall on the next stage side is tilted, or the walls on both sides are tilted, and further, it may have an arbitrary curved surface shape. Also,
In FIG. 3, components such as an impeller, which are not shown, are
It may be the same as in the first embodiment.

[Third Embodiment] FIG. 4 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a third embodiment of the present invention. FIG. 4 is an enlarged view particularly showing the branch portion of the extraction flow and the main flow and the vicinity of the collecting pipe,
In the figure, those having the same reference numerals as those in FIG. 2 are the same parts as those in the previous embodiment, and therefore their explanations are omitted. Further, FIG. 5 is a transverse sectional view taken along the arrow A in FIG.

Also in the embodiment shown in FIGS. 4 and 5, the collecting pipe 1
5B is arranged on the outer peripheral side in the radial direction from the bend portion 11 of the return passage, and the annular extraction passage 14 is provided between the collecting pipe and the extraction port 13.
B is connected, but further, in the extraction flow path 14B,
Circular blade-like guide blades 22 having the cross-sectional structure shown in FIG.
Is equipped. In the present embodiment, the guide blade 22 is a straight blade having a constant plate thickness and having no warp, and is attached so that the angles formed by the front and rear edges with the circumferential direction are β1 and β2, respectively. There is. At this time, β1 <β2 is always geometrically maintained. Also, the collecting pipe 15B
Is formed in a scroll structure in which the cross-sectional area is changed so that the flow velocity in the collecting pipe 15B is constant in the circumferential direction.

By adopting the structure of the embodiment shown in FIGS. 4 and 5, the extraction flow 18 is branched from the main flow 19 at the outlet of the diffuser 10 and then in the extraction flow path 14B. Although it receives the same deceleration action as that of the embodiment, in addition to the guide blades 22 provided in the extraction flow passage 14B.
As a result, the circumferential velocity component of the extraction flow is reduced, so that the inflow velocity into the collecting pipe 15B can be further reduced. Therefore, the swirling flow velocity in the collecting pipe 15B can be reduced, and the friction loss in the collecting pipe 15B is reduced.

In the present embodiment, the collecting pipe 1
Although 5B has a scroll structure, it may have a collector structure as in the case of the first embodiment. The constituent elements not shown in FIGS. 4 and 5 may be the same as those in the first embodiment.

[Fourth Embodiment] FIG. 6 shows a fourth embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view of an essential part showing the internal structure of the multi-stage centrifugal compressor according to the embodiment of FIG. In the figure, those having the same reference numerals as those in FIG. 5 are the same parts as those in the embodiments of FIGS. The embodiment shown in FIG. 6 is, in particular, different from the third embodiment shown in FIG.
The shape of the guide blades 22A provided on the
As shown in FIG. 6, the guide blade 22A has an arc shape with a warp. The mounting angles of the front and rear edges of the guide blade 22A are formed so as to be β1 <β2 as in the third embodiment. The front and rear edge radii of the guide blades 22A are R1 and R2, respectively. Further, the front edge portion of the guide blade 22A is formed so that its cross section has an arc shape.

Since the guide blade 22A is not limited to the straight blade by adopting the structure of the embodiment shown in FIG. 6, the guide blade 22A is not limited to the straight blade.
There is an advantage that the degree of freedom of configuration is high. That is, in the straight blade according to the third embodiment, if any three of the blade mounting angles β1 and β2 of the front and rear edges and the front and rear edge radii R1 and R2 are determined, the remaining one is geometric. Uniquely, and therefore, it is not always possible to form the optimum shape. On the other hand, in the arcuate blade as in the present embodiment, all of the above four parameters can be independently determined, so that a more desirable blade shape can be formed. Further, in the present embodiment, the leading edge portion of the blade is formed so that the cross section has an arc shape, and thus it is possible to reduce the loss when the extraction flow flows into the circular blade row.

[Fifth Embodiment] FIG. 7 shows a fifth embodiment of the present invention.
FIG. 3 is an enlarged cross-sectional view of an essential part showing the internal structure of the multi-stage centrifugal compressor according to the embodiment of FIG. In the figure, those having the same reference numerals as those in FIG. 5 are the same parts as those in the embodiments of FIGS. The embodiment shown in FIG. 7 is different from the third embodiment shown in FIG. 5 in the shape of the guide blade 22B provided in the extraction flow passage 14B, and here, as shown in FIG. 22B has a blade cross-sectional shape in which the blade thickness changes from its leading edge to its trailing edge. The mounting angles of the front and rear edges of the guide blade 22B are formed so as to be β1 <β2 as in the third embodiment. Also,
The front and rear edge radii of the guide blades 22B are R1 and R2, respectively. Further, in the present embodiment, the guide blades 22B in the form of a circular blade row are arranged so that they do not overlap in the circumferential direction, that is, there is no throat between the blades.

By adopting the structure of the embodiment shown in FIG. 7, as in the fourth embodiment, the guide blades 22B are not limited to the straight blades, and the degree of freedom of the structure is high. There is an advantage. In addition, such an arrangement of blade rows with no throat between the blades is often used in the diffuser section of a centrifugal compressor, does not cause blockage even at large flow rates, and does not stall even at small flow rates, so it has a wide flow rate. It is known that effective deceleration is obtained in the range. Therefore, even when the extraction flow rate changes due to the operating conditions of the plant or the like, the loss associated with the extraction can be effectively reduced.

[Sixth Embodiment] FIG. 8 shows a sixth embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of an essential part showing the internal structure of the multistage centrifugal compressor according to the embodiment of FIG. FIG. 8 is an enlarged view of the vicinity of the branch portion of the extraction flow and the main flow and the collecting pipe.
The same reference numerals as those in FIG. 2 are the same as those in the first embodiment, and therefore the description thereof will be omitted. In the embodiment shown in FIG. 8, the collecting pipe 15C is located radially outward of the bend portion 11 of the return passage and between the diffuser 10 and the preceding return passage 21a (see FIG. 2) in the rotation axis direction. It is provided. Further, the collecting pipe 15C and the extraction port 13 are connected by an annular extraction flow passage 14C.

The extraction flow channel 14C is formed so that the flow channel width gradually increases from the inlet to the outlet. Further, guide vanes 22 in the form of a circular blade row are installed in the extraction flow passage 14C. The cross-sectional shape and arrangement method of the guide vanes may be any of those shown in the third to fifth embodiments (embodiments of FIGS. 5, 6 and 7). By adopting the configuration of the embodiment shown in FIG. 8, the same effects as those of the first to third or the fourth and fifth embodiments can be obtained.

In the present embodiment, as a means for expanding the flow passage width of the extraction flow passage 14C, the front wall of the flow passage walls forming the extraction flow passage 14C is tapered.
This may be such that the wall on the next stage side is tilted, or the walls on both sides are tilted, and further, it may have an arbitrary curved surface shape. Further, the constituent elements not shown in FIG. 8 may be the same as those in the first embodiment.

[Embodiment 7] FIG. 9 shows a seventh embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of an essential part showing the internal structure of the multistage centrifugal compressor according to the embodiment of FIG. FIG. 9 is an enlarged view especially showing the vicinity of the branch portion of the extraction flow and the main flow and the collecting pipe.
The same reference numerals as those in FIG. 2 are the same as those in the first embodiment, and therefore the description thereof will be omitted. In addition, FIG. 10 is a development view of the cylinder taken along the line AA of FIG.

In the embodiment shown in FIGS. 9 and 10, the collecting pipe 15D is provided between the return flow passage 21 and the next-stage diffuser 10a (see FIG. 2) in the rotation axis direction. Further, the extraction port 13 is provided in the middle of the bend portion 11 of the return flow channel 21, and the extraction port 13 and the collecting pipe 15D are connected by an annular extraction flow channel 14D extending substantially in the rotation axis direction. Here, the extraction flow passage 14D is formed so that the flow passage width gradually increases from the inlet portion toward the outlet portion thereof.
A plurality of guide blades 22A are provided in the circumferential direction as shown in FIG. The guide blade 22A is an arc-shaped blade having a constant plate thickness, and has an angle β with the circumferential direction at its front and rear edges.
1 and β2 are formed such that β1 <β2.

By adopting the structure of the embodiment shown in FIGS. 9 and 10, the same effects as those of the first to third or sixth embodiments can be obtained, but in particular, this embodiment In the above, since the extraction port 13 is provided in the middle of the bend part 11, the speed is already reduced at the inlet part of the extraction flow path 14D as compared with the case of the above-mentioned embodiment, and the flow velocity into the collecting pipe 15D can be further reduced. Therefore, the swirling flow velocity in the collecting pipe 15D, and thus the friction loss, can be reduced. Alternatively, if the flow velocity in the collecting pipe 15D is set to the same level as in the above embodiment, the deceleration load in the extraction flow passage 14D can be reduced, and the flow rate of the extraction flow 18 changes to a flow rate smaller than the design value.
Even if the inflow angle into the guide blade 22A becomes smaller than β1, it is possible to make it difficult to stall.

Further, in the present embodiment, the collecting pipe 15D is provided between the return flow passage 21 and the next stage diffuser 10a in the rotation axis direction, and the bend portion 1 is provided.
Since the outer diameter of the collecting pipe 15D can be suppressed to the same size as the outer diameter of 1, the outer diameter of the casing 1 can be reduced. Such an arrangement is particularly effective when a large space for arranging the collecting pipe can be secured, such as when the impeller 3c of the next stage has a large axial pitch between the stages.

In the embodiment shown in FIGS. 9 and 10,
The guide blades 22A provided in the extraction flow passage 14D are arc-shaped blades having a constant plate thickness as shown in FIG. 10, but may have the blade cross-sectional shape used in the fifth embodiment. In this case, an effect similar to that in the fifth embodiment can be obtained. Further, as a means for expanding the flow channel width of the extraction flow channel 14D, in the present embodiment, among the flow channel walls forming the extraction flow channel 14D, the wall on the outer peripheral side is inclined in a tapered shape. The wall on the inner peripheral side may be tilted, or both may be tilted, and further, an arbitrary curved surface shape may be used.
Further, the constituent elements not shown in FIGS.
It may be the same as in the first embodiment.

Next, an embodiment of the second invention will be described with reference to FIGS. 11 to 14. [Embodiment 8] FIG. 11 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to an eighth embodiment of the present invention. FIG. 11 particularly shows an enlarged view of the branch portion of the extraction flow and the main flow and the vicinity of the collecting pipe. In the figure, the same reference numerals as those in FIG. 2 are the same parts as those in the first embodiment. Therefore, the description is omitted.

The embodiment shown in FIG.
It is an improved version of the device disclosed in Japanese Patent No. 51794. That is, the shapes of the branch portions of the extraction flow 18 and the main flow 19 are improved, and the portion 16 with which the flow 17 of the working gas from the impeller collides is formed in a rounded and blunt shape. The collecting pipe 15E is formed so as to be located between the diffuser 10 and the pre-stage return flow passage 21a (see FIG. 2) when viewed in the rotation axis direction.

As described above, in the prior art, in order to ensure the performance at a certain specification point (design point), the branch portion of the main stream and the extraction stream is divided into two parts so that the smoothest extraction is possible at this time. For example, as shown in FIG. 2, it is formed in a wedge shape with an acute angle. However, an actual compressor may be operated at a point different from the design point due to the operating conditions of the plant, etc., and the flow rate ratio of the main flow and the extraction flow may change. If they do not match, one of the main flow and the extraction flow undergoes rapid acceleration and the other undergoes rapid deceleration.
This is similar to abrupt reduction or abrupt expansion of the flow path area. At this time, if there is a sharp corner at the branching portion, contraction or separation will occur, resulting in a large loss, resulting in deterioration of compressor performance. Was there.

Therefore, as in this embodiment, the extraction stream 1
8 and the main flow 19 have a rounded portion at which the flow 17 of the working gas from the impeller collides to form a blunt shape, so that the main flow 19 and the extraction flow 1
Even when the flow rate ratio to 8 changes, it is possible to mitigate the rapid expansion and contraction of the flow path, and to suppress the occurrence of contraction and separation. Therefore, even at an operating point different from the design point,
The performance deterioration of the compressor can be minimized. The components not shown in FIG. 11 may be the same as those in the first embodiment.

[Ninth Embodiment] FIG. 12 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a ninth embodiment of the present invention. In particular, FIG. 12 is an enlarged view of the vicinity of the branch portion of the extraction flow and the main flow and the collecting pipe. In the figure, the same reference numerals as those in FIG. 2 are equivalent to those of the first embodiment. Therefore, the description is omitted. The embodiment shown in FIG. 12 has a configuration similar to that of the first embodiment shown in FIG. 2, but the shapes of the branch portions of the extraction flow 18 and the main flow 19 are different, and here, the eighth embodiment is described. Similar to the form of
Portion 16 against which flow 17 of working gas from the impeller collides
Is formed into a rounded and blunt shape.

[Embodiment 10] FIG. 13 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a tenth embodiment of the present invention. FIG. 13 particularly shows an enlarged view of the branch portion of the extraction flow and the main flow and the vicinity of the collecting pipe. In the figure, the same reference numerals as those in FIG. 2 are the same parts as those in the first embodiment. Therefore, the description is omitted. In the embodiment shown in FIG. 13, the branch portions of the extraction flow 18 and the main flow 19 are formed in a blunt shape, as in the eighth embodiment. In addition, in the present embodiment, the extraction port 1
3 is formed in the middle of the bend portion 11 of the return flow path or near the outlet of the bend portion 11. The collecting pipe 15F is located on the radially outer side of the bend portion 11.

According to the embodiment shown in FIG. 13, by forming the branch portions of the extraction flow 18 and the main flow 19 into a rounded and blunt shape, the same effect as that of the eighth embodiment can be obtained. Therefore, even when the flow rate ratio between the main flow and the extraction flow changes due to changes in the operating conditions of the plant, it is possible to suppress the occurrence of contraction and separation at the branching portion.

Further, in the present embodiment, the extraction port 13 is used in the middle of the bend portion 11 of the return flow path, and further, the bend portion 11.
Since it is formed in the vicinity of the outlet, the flow 17 of the boosted gas, that is, the working gas is decelerated until reaching the branch portion, and the loss due to the branch is further reduced. Therefore, even at an operating point that is different from the design point, it is possible to minimize the performance degradation of the compressor. Note that constituent elements not shown in FIG. 13 may be the same as those in the first embodiment.

[Embodiment 11] FIG. 14 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to an eleventh embodiment of the present invention. In particular, FIG. 14 is an enlarged view showing the vicinity of the branch portion and the collecting pipe of the extraction flow and the main flow. In the figure, the same reference numerals as those in FIG. Therefore, the description is omitted. In the embodiment shown in FIG. 14, the branch portions of the extraction flow 18 and the main flow 19 are formed in a blunt shape, as in the eighth embodiment. In addition, in the present embodiment, the extraction port 1
3 is formed near the exit of the bend part 11 of the return flow path. The collecting pipe 15G is located between the return flow passage 21 and the next-stage diffuser 10a (see FIG. 2) when viewed in the rotation axis direction.

According to the embodiment shown in FIG. 14, the branch portions of the extraction flow 18 and the main flow 19 are formed in a blunted shape with roundness, and the same effect as that of the eighth embodiment can be obtained. Therefore, even when the flow rate ratio between the main flow and the extraction flow changes due to changes in the operating conditions of the plant, it is possible to suppress the occurrence of contraction and separation at the branching portion.

Further, in this embodiment, since the extraction port 13 is formed near the exit of the bend section 11 of the return flow path,
The flow 17 of the working gas is slowed down to reach the branch portion, and the loss due to the branch is further reduced. Therefore,
Even at an operating point that is different from the design point, it is possible to minimize the performance degradation of the compressor. Note that constituent elements not shown in FIG. 14 may be the same as those in the first embodiment.

[0053]

As described above in detail, according to the present invention, an annular extraction port for extracting a part of the gas pressurized by the centrifugal impeller from between the stages, and the flow of the extracted gas are collected and the intermediate discharge is performed. In a multi-stage centrifugal compressor having a collecting pipe leading to a nozzle, it is possible to provide a high-performance multi-stage centrifugal compressor by reducing energy loss due to extraction of boosted gas from the diffuser to the collecting pipe.

Further, according to the present invention, an annular extraction port for extracting a part of the gas pressurized by the centrifugal impeller from between the stages, and a collecting pipe for collecting the flow of the extracted pressurized gas and guiding it to the intermediate discharge nozzle are provided. In the multi-stage centrifugal compressor, a high-performance multi-stage centrifuge that does not cause contraction or separation at the branch of the extraction flow and the main flow guided to the centrifugal impeller of the next stage where the flow of the pressurized gas collides. A compressor can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram in a first embodiment of a multistage centrifugal compressor that adopts an interstage extraction flow channel structure to which the present invention is applied.

FIG. 2 is a longitudinal sectional view of an essential part showing the internal structure of the first embodiment of the multi-stage centrifugal compressor shown in FIG.

FIG. 3 is a longitudinal sectional view of an essential part showing the internal structure of a multi-stage centrifugal compressor according to a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of an essential part showing the internal structure of a multi-stage centrifugal compressor according to a third embodiment of the present invention.

5 is a transverse sectional view taken along the arrow A in FIG.

FIG. 6 is an enlarged transverse cross-sectional view of an essential part showing the internal structure of a multi-stage centrifugal compressor according to a fourth embodiment of the present invention.

FIG. 7 is an enlarged transverse cross-sectional view of essential parts showing the internal structure of a multi-stage centrifugal compressor according to a fifth embodiment of the present invention.

FIG. 8 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a sixth embodiment of the present invention.

FIG. 9 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a seventh embodiment of the present invention.

FIG. 10 is a development view of a cylinder taken along the line AA of FIG.

FIG. 11 is a longitudinal sectional view of an essential part showing the internal structure of a multi-stage centrifugal compressor according to an eighth embodiment of the present invention.

FIG. 12 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a ninth embodiment of the present invention.

FIG. 13 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to a tenth embodiment of the present invention.

FIG. 14 is a longitudinal sectional view of an essential part showing the internal structure of a multistage centrifugal compressor according to an eleventh embodiment of the present invention.

[Explanation of symbols]

1 ... Casing, 2 ... Rotating shaft, 3 ... Impeller, 3a ... 1st stage impeller, 3b ... 2nd stage impeller, 3c ... 3rd stage impeller,
3d ... 4th-stage impeller, 3e ... 5th-stage impeller, 5 ... suction nozzle, 6 ... intermediate discharge nozzle, 7 ... final discharge nozzle, 10
... Diffuser, 10a ... Next-stage diffuser, 11 ... Bend part, 12 ... Channel part, 13 ... Extraction port, 14, 14
A, 14B, 14C, 14D ... Extraction channel, 15, 15
B, 15C, 15D, 15E, 15F, 15G ... Collecting pipe, 16 ... Colliding part of boosted gas, 17 ... Flow of working gas,
18 ... Extraction flow, 19 ... Main flow, 20 ... Guide vane, 21 ... Return flow passage, 21a ... Previous return flow passage, 22 ... Guide vane.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Haruo Miura Inventor Haruo Miura 603 Jinritsu-cho, Tsuchiura-shi, Ibaraki Hiritsu Manufacturing Co., Ltd. Tsuchiura factory (72) Takashi Eno 603 Hiritsu-machi, Tsuchiura-shi, Ibaraki Hiritsu Manufacturing Co., Ltd. Tsuchiura factory

Claims (13)

[Claims] 1. A casing having a suction port, a discharge port, and an intermediate discharge port, a rotating shaft provided in the casing, a multistage impeller fixed to the rotating shaft, and each of these impellers. A diffuser arranged on the outer circumference in the radial direction of the impeller and a return flow passage provided downstream of the diffuser are provided, and the gas pressurized by the impeller is passed through the diffuser and the return flow passage to the next stage blade. A multi-stage system for guiding a vehicle, comprising an annular extraction port for extracting a part of the gas pressurized by the impeller from between the stages, and a collecting pipe for collecting the flow of the extracted pressurized gas and guiding it to an intermediate discharge port. In the centrifugal compressor, an annular extraction flow path is provided between the diffuser and the collecting pipe, the multi-stage centrifugal compressor. 2. The multi-stage centrifugal compressor according to claim 1, wherein the collecting pipe is provided on an outer peripheral side in a radial direction with respect to a curved portion that moves from the diffuser to the return flow passage. 3. The multistage according to claim 1, wherein the collecting pipe is formed so as to be located between the return flow passage and the next-stage diffuser when viewed in the rotation axis direction. Centrifugal compressor. 4. The multi-stage centrifuge according to claim 1, wherein the collecting pipe is formed so as to be located between the diffuser and the preceding-stage return flow passage as viewed in the direction of the rotation axis thereof. Compressor. 5. The multi-stage centrifugal compressor according to claim 1, wherein the flow passage width of the extraction flow passage is formed so as to increase from its inlet to its outlet. 6. The multistage centrifugal compressor according to claim 1, wherein a plurality of guide vanes are provided in the extraction flow path. 7. The multi-stage centrifugal compressor according to claim 6, wherein a blade having a constant blade thickness from the front edge to the rear edge is used as the guide blade. 8. The multi-stage centrifugal compressor according to claim 7, wherein at least one of a front edge portion and a rear edge portion of the guide vane is formed in an arc-shaped cross section. 9. The multi-stage centrifugal compressor according to claim 6, wherein the guide vanes are vanes having a blade cross-section whose blade thickness is changed from its leading edge to its trailing edge. . 10. A casing having a suction port, a discharge port, and an intermediate discharge port, a rotary shaft provided in the casing, a multistage impeller fixed to the rotary shaft, and each of these impellers. A diffuser arranged on the outer circumference in the radial direction of the impeller and a return flow passage provided downstream of the diffuser are provided, and the gas pressurized by the impeller is passed through the diffuser and the return flow passage to the next stage blade. A multi-stage centrifuge equipped with an annular extraction port that guides a part of the gas pressurized by the impeller from between the stages and a collecting pipe that collects the flow of the extracted pressurized gas and guides it to an intermediate discharge port. In the compressor, the part where the flow of the boosting gas collides with the branch of the extraction flow extracted from between the stages and the main flow guided to the impeller of the next stage is formed into a rounded and blunt shape. That Multi-stage centrifugal compressor and butterflies. 11. The multi-stage centrifugal compressor according to claim 10, wherein the collecting pipe is provided on an outer peripheral side in a radial direction with respect to a curved portion that moves from the diffuser to the return flow passage. 12. The multi-stage according to claim 10, wherein the collecting pipe is formed so as to be located between the return flow passage and the next-stage diffuser when viewed in the rotation axis direction. Centrifugal compressor. 13. The multi-stage centrifuge according to claim 10, wherein the collecting pipe is formed so as to be located between the diffuser and the pre-return flow passage as viewed in the direction of the rotation axis thereof. Compressor.