U.S. patent application number 15/108488 was filed with the patent office on 2016-11-10 for diaphragm and centrifugal rotating machine.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES COMPRESSOR CORPORATION, MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Shinji IWAMOTO, Akihiro NAKANIWA.
Application Number | 20160327050 15/108488 |
Document ID | / |
Family ID | 53777944 |
Filed Date | 2016-11-10 |
United States Patent
Application |
20160327050 |
Kind Code |
A1 |
NAKANIWA; Akihiro ; et
al. |
November 10, 2016 |
DIAPHRAGM AND CENTRIFUGAL ROTATING MACHINE
Abstract
A diaphragm rotatably covers an impeller around an axis. A
diaphragm has a suction flow channel configured to supply a gas
toward an inlet of an impeller, a diffuser flow channel through
which the gas discharged from the impeller outward in a radial
direction flows, and a communication section configured to bring
the suction flow channel and the diffuser flow channel in constant
communication with each other.
Inventors: |
NAKANIWA; Akihiro; (Tokyo,
JP) ; IWAMOTO; Shinji; (Hiroshima-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD.
MITSUBISHI HEAVY INDUSTRIES COMPRESSOR CORPORATION |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
MITSUBISHI HEAVY INDUSTRIES COMPRESSOR CORPORATION
Tokyo
JP
|
Family ID: |
53777944 |
Appl. No.: |
15/108488 |
Filed: |
February 4, 2015 |
PCT Filed: |
February 4, 2015 |
PCT NO: |
PCT/JP2015/053074 |
371 Date: |
June 27, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 17/122 20130101;
F04D 27/02 20130101; F04D 29/682 20130101; F04D 29/441 20130101;
F04D 29/286 20130101 |
International
Class: |
F04D 17/12 20060101
F04D017/12; F04D 29/28 20060101 F04D029/28; F04D 29/44 20060101
F04D029/44; F04D 27/02 20060101 F04D027/02; F04D 29/68 20060101
F04D029/68 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2014 |
JP |
2014-020490 |
Claims
1. (canceled)
2. A diaphragm configured to rotatably cover an impeller about an
axis, the diaphragm having: an inlet-side flow channel configured
to supply a fluid toward an inlet of the impeller; an outlet-side
flow channel through which the fluid discharged from the impeller
outward in the radial direction flows; a communication section
configured to bring the inlet-side flow channel and the outlet-side
flow channel in constant communication with each other; a first
vane disposed in the inlet-side flow channel and configured to
guide the fluid in a desired direction; and a second vane disposed
in the outlet-side flow channel and configured to guide the fluid
in a desired direction, wherein the communication section is
disposed between a position closer to an upstream side than the
first vane and a position closer to a downstream side than the
second vane.
3. A centrifugal rotating machine comprising: the diaphragm
according to claim 2; and an impeller configured to be supported by
the diaphragm to be relatively rotatable around the axis with
respect to the diaphragm.
4. The centrifugal rotating machine according to claim 3,
comprising a plurality of impellers arranged in a direction of the
axis and rotated around the axis, wherein the diaphragm supports at
least one impeller, among the plurality of impellers, in which a
surge flow rate is designed to be mostly increased.
5. The centrifugal rotating machine according to claim 3,
comprising a plurality of impellers arranged in a direction of the
axis and rotated around the axis, wherein a plurality of diaphragms
are arranged in the direction of the axis to support the plurality
of impellers, respectively, and flow channel areas of the fluid in
the communication sections are different in each of the diaphragms.
Description
TECHNICAL FIELD
[0001] The present invention relates to a diaphragm, and a
centrifugal rotating machine including the same.
[0002] Priority is claimed on Japanese Patent Application No.
2014-020490, filed Feb. 5, 2014, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] For example, a centrifugal compressor is known as a type of
centrifugal rotating machine. In the centrifugal compressor, a gas
flows in a radial direction of a rotating impeller, and the gas is
compressed using a centrifugal force. In this kind of centrifugal
compressor, a multi-stage centrifugal compressor in which impellers
are provided in multiple stages in an axial direction to compress
the gas in stages is known.
[0004] Incidentally, in the above-mentioned multi-stage centrifugal
compressor, a phenomenon known as surging occurs, in which a gas
flows backward from a downstream side toward an upstream side in
the impellers, occurs. A method is known in which the occurrence of
surging is suppressed by forming a bypass line configured to return
some of a main stream from a downstream side to an upstream side of
a flow of the main stream, and achieving the enlargement of an
operation range, when a flow rate of the entire system is smaller
than a flow rate at which such surging occurs, i.e., a surge flow
rate.
[0005] For example, in Patent Literature 1, an example of such a
bypass line is disclosed. The bypass line is formed to recirculate
some of the fluid from a discharge side toward a suction side of
the impeller of each stage when the impeller of each stage
approaches a surging state.
CITATION LIST
Patent Literature
[0006] [Patent Literature 1]
[0007] Japanese Patent No. 2637144
SUMMARY OF INVENTION
Technical Problem
[0008] However, in the case of the bypass line of Patent Literature
1, only when the bypass line approaches the surging stage, the
bypass line is opened to recirculate the fluid.
[0009] For this reason, when the system flow rate is slightly
larger than the flow rate in which the surging occurs, or the like,
recirculation of the fluid is not performed. Accordingly, since the
bypass line can reach a state extremely close to the occurrence of
the surging without surging occuring, the flow may become instable
and cause shaft vibrations. In addition, in the bypass line of
Patent Literature 1, since a structure such as a spring or the like
configured to open and close the bypass line is installed, a
pressure drop when the fluid flows into the bypass line is
increased, and compression efficiency is decreased.
[0010] In consideration of the above-mentioned circumstances, an
object of the present invention is to provide a diaphragm and a
centrifugal compressor capable of suppressing the occurrence of
surging and enlarging an operation range while maintaining
compression efficiency.
Solution to Problem
[0011] In order to solve the aforementioned problems, the present
invention employs the following means.
[0012] That is, a diaphragm of an aspect of the present invention
is a diaphragm configured to rotatably cover an impeller about an
axis, the diaphragm having: an inlet-side flow channel configured
to supply a fluid toward an inlet of the impeller; an outlet-side
flow channel through which the fluid discharged from the impeller
outward in the radial direction flows; and a communication section
configured to bring the inlet-side flow channel and the outlet-side
flow channel in constant communication with each other.
[0013] According to the above-mentioned diaphragm, as the
communication section is formed, the fluid compressed or pumped by
the impeller can be constantly recirculated from the outlet-side
flow channel to the inlet-side flow channel.
[0014] Accordingly, the occurrence of surging can be suppressed by
smoothly recirculating the fluid from a downstream side of the
impeller to an upstream side of the impeller through the
communication section.
[0015] In addition, the diaphragm may further include a first vane
disposed in the inlet-side flow channel and configured to guide the
fluid in a desired direction; and a second vane disposed in the
outlet-side flow channel and configured to guide the fluid in a
desired direction, wherein the communication section is disposed
between a position closer to an upstream side than the first vane
and a position closer to a downstream side than the second
vane.
[0016] As the communication section is disposed at the
above-mentioned position, the communication section is disposed at
a position spaced apart from the impeller. Accordingly, the fluid
recirculated through the communication section is less susceptible
to an influence of rotation of the impeller. Accordingly, the fluid
can be smoothly recirculated.
[0017] Further, a centrifugal rotating machine as another aspect of
the present invention includes the above-mentioned diaphragm; and
an impeller configured to be supported by the diaphragm to be
relatively rotatable around the axis with respect to the
diaphragm.
[0018] According to the above-mentioned centrifugal rotating
machine, as the diaphragm is provided, the fluid can be smoothly
circulated from the downstream side of the impeller to the upstream
side of the impeller through the communication section for constant
communication, and a flow rate of the entire system of the
centrifugal rotating machine can be suppressed from approaching a
surge flow rate.
[0019] In addition, the centrifugal rotating machine may include a
plurality of impellers arranged in a direction of the axis and
rotated around the axis, wherein the diaphragm supports at least
one impeller, among the plurality of impellers, in which a surge
flow rate is designed to be mostly increased.
[0020] In this way, as the communication section is selectively
applied to the impeller in which the surge flow rate is designed to
be mostly increased, a stage of the impeller in which recirculation
occurs can be limited. Accordingly, since the flow rate of the
entire system of the centrifugal rotating machine can be suppressed
to reduce power, the occurrence of the surging can be effectively
suppressed.
[0021] Further, the centrifugal rotating machine may include a
plurality of impellers arranged in a direction of the axis and
rotated around the axis, wherein a plurality of diaphragms are
arranged in the direction of the axis to support the plurality of
impellers, respectively, and flow channel areas of the fluid in the
communication sections are different in each of the diaphragms.
[0022] Since the flow channel areas of the communication sections
are different in each of the diaphragms in this way, in combination
with the surge flow rates different for each of the impellers of
the stages, flow rates of the fluid recirculated from the
downstream sides to the upstream sides of the impellers through the
communication sections can be adjusted. That is, the flow rate of
the recirculated fluid can be adjusted according to specifications
of the stages, and the occurrence of the surging can be more
effectively suppressed.
Advantageous Effects of Invention
[0023] According to the aspect of the present invention, as a
communication section in a constant communication state is
installed, the occurrence of surging can be suppressed while
maintaining compression efficiency and the enlargement of an
operation range is possible.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a longitudinal cross-sectional view including an
axis of a multi-stage centrifugal compressor according to an
embodiment of the present invention.
[0025] FIG. 2 is a graph showing a difference between surge lines
of a multi-stage centrifugal compressor according to the embodiment
of the present invention and a multi-stage centrifugal compressor
when a communication section is not provisionally installed and
showing a relation between a flow rate and a compression ratio of a
gas required for a system represented by a horizontal axis.
[0026] FIG. 3 is a longitudinal cross-sectional view including an
axis of a multi-stage centrifugal compressor according to a first
variant of the embodiment of the present invention.
[0027] FIG. 4 is a longitudinal cross-sectional view including an
axis of a multi-stage centrifugal compressor according to a second
variant of the embodiment of the present invention.
[0028] FIG. 5 is a longitudinal cross-sectional view including an
axis of a multi-stage centrifugal compressor according to a third
variant of the embodiment of the present invention.
[0029] FIG. 6 is a longitudinal cross-sectional view including an
axis of a multi-stage centrifugal compressor according to a fourth
variant of the embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0030] Hereinafter, an embodiment of a multi-stage centrifugal
compressor 1 (a centrifugal rotating machine) according to the
present invention will be described with reference to the
accompanying drawings.
[0031] As shown in FIG. 1, the multi-stage centrifugal compressor 1
includes a rotary shaft 2 that rotates around an axis O, a
plurality of impellers 3 attached to the rotary shaft 2, and a
casing 4 configured to rotatably support the rotary shaft 2 and
having a casing flow channel FC through which a gas G (a fluid)
such as air or the like flows.
[0032] The rotary shaft 2 has a columnar shape extending along the
axis O and formed about the axis O. The rotary shaft 2 is
relatively rotated with respect to the casing 4 around the axis O
by a power source such as an electric motor or the like (not
shown).
[0033] The plurality of impellers 3 are disposed at intervals in
the axis O direction in which the axis O extends. In the
multi-stage centrifugal compressor 1 of the embodiment, five
impellers 3 are arranged.
[0034] Hereinafter, the impellers 3 are a first stage impeller 3a,
a second stage impeller 3b, a third stage impeller 3c, a fourth
stage impeller 3d and a fifth stage impeller 3e that are disposed
from the upstream side to the downstream side through which the gas
G flows (from one side to the other side in the axis O
direction).
[0035] Each of the impellers 3 has a disk-shaped hub 11 having a
diameter that is gradually increased toward the downstream side in
the axis O direction, a plurality of blades 12 radially attached to
the hub 11 and lined up spaced apart from each other in a
circumferential direction with respect to the axis O, and a shroud
13 attached to cover the plurality of blades 12 from the upstream
side in the axis O direction.
[0036] A region surrounded by the blades 12 neighboring in the
circumferential direction, the hub 11 and the shroud 13 is an
impeller flow channel FC0 through which the gas G flows. An inlet
into which a gas is suctioned and an outlet through which the gas
is discharged are formed at the impeller flow channel FC0. The
inlet is formed at an upstream end in the axis O direction of the
impeller flow channel FC0. The outlet is formed at an outer end in
the radial direction that is a portion of a downstream side in the
axis O direction of the impeller flow channel FC0.
[0037] Further, the impeller 3 may be a closed impeller at which
the shroud 13 is installed as in the embodiment, or may be an open
impeller at which the shroud 13 is not installed unlike the
embodiment.
[0038] The casing flow channel FC through which the gas G flows is
formed in the casing 4. The gas G is compressed by a centrifugal
force as the gas G flows from the impeller flow channel FC0 of the
first stage impeller 3a to the impeller flow channel FC0 of the
fifth stage impeller 3e via the casing flow channel FC in
stages.
[0039] The casing 4 has journal bearings 7 installed at both ends
in the axis O direction of the rotary shaft 2, and a thrust bearing
8 installed at an end portion of one side. The casing 4 supports
the rotary shaft 2 using the journal bearings 7 and the thrust
bearing 8. The rotary shaft 2 is relatively rotatably supported
with respect to the casing 4.
[0040] The casing flow channel FC of the casing 4 is formed in the
casing 4 in an annular shape about the axis O.
[0041] The casing flow channel FC has a suction flow channel FC1
(an inlet-side flow channel) configured to bring the inlet of the
impeller flow channel FC0 in the first stage impeller 3a and the
outside of the multi-stage centrifugal compressor 1 in
communication with each other, a discharge flow channel FC2 (an
outlet-side flow channel) configured to bring the outlet of the
impeller flow channel FC0 of the fifth stage impeller 3e and the
outside of the multi-stage centrifugal compressor 1 in
communication with each other, and intermediate flow channels FC3
respectively formed between the impellers 3 of the stages.
[0042] The suction flow channel FC1 is formed in the casing 4 at a
position closer to the upstream side in the axis O direction than
the first stage impeller 3a. The suction flow channel FC1 is opened
outward in the radial direction at a portion in the circumferential
direction of the casing 4 and extends inward in the radial
direction, and the gas G is supplied to the inlet of the impeller
flow channel FC0 in the first stage impeller 3a.
[0043] An inlet guide vane 21 (a first vane) configured to turn the
gas G suctioned from the outside of the multi-stage centrifugal
compressor 1 to a desired direction to guide the gas G into the
impeller flow channel FC0 is installed in the suction flow channel
FC1. The inlet guide vane 21 can adjust an inclination in the
circumferential direction with respect to the radial direction
using an operation mechanism (not shown). The desired direction is,
for example, a direction inclined forward in a rotational direction
of the impeller 3 with respect to the radial direction to apply
prerotation to the gas G suctioned from the outside.
[0044] The discharge flow channel FC2 is formed in the casing 4 to
extend from the outlet of the impeller flow channel FC0 in the
fifth stage impeller 3e outward in the radial direction. An outlet
configured to discharge the gas G is formed at the discharge flow
channel FC2. An outlet of the discharge flow channel FC2 is opened
at a portion in the circumferential direction of the casing 4
outward in the radial direction. The discharge flow channel FC2
allows the gas discharged from the outlet of the impeller flow
channel FC0 in the fifth stage impeller 3e to flow therethrough to
be discharged to the outside.
[0045] A discharge scroll S serving as a space extending in an
annular shape in the circumferential direction is formed at the
discharge flow channel FC2 at a position in front of the outlet of
the discharge flow channel FC2. The discharge scroll S increases a
pressure of the gas G discharged from the outlet of the impeller
flow channel FC0 of the fifth stage impeller 3e.
[0046] Here, in the embodiment, as shown by a broken line of FIG.
1, a diffuser vane 22 (a second vane) may be formed between the
discharge scroll S and the impeller 3 in the discharge flow channel
FC2. The diffuser vane 22 turns the gas G discharged from the
impeller flow channel FC0 to a desired direction to guide the gas G
to the discharge scroll S and converts a dynamic pressure of the
flowing gas G into a static pressure. The desired direction is a
direction in which conversion to the static pressure is performed,
i.e., a direction inclined in the circumferential direction with
respect to the radial direction.
[0047] The intermediate flow channels FC3 are formed in the casing
4 at a position between the first stage impeller 3a and the second
stage impeller 3b, a position between the second stage impeller 3b
and the third stage impeller 3c, a position between the third stage
impeller 3c and the fourth stage impeller 3d, and a position
between the fourth stage impeller 3d and the fifth stage impeller
3e.
[0048] Since all of the intermediate flow channels FC3 between the
stages have substantially the same configuration, the intermediate
flow channel FC3 between the first stage impeller 3a and the second
stage impeller 3b will be representatively described.
[0049] The intermediate flow channel FC3 is formed in the casing 4
without communication with the outside of the casing 4. The
intermediate flow channel FC3 has a diffuser flow channel FC4 (an
outlet-side flow channel) extending outward in the radial direction
from the outlet of the impeller flow channel FC0 in the first stage
impeller 3a, and a return flow channel FC5 connected to the
diffuser flow channel FC4 and extending toward the inlet of the
impeller flow channel FC0 of the second stage impeller 3b.
[0050] The gas G discharged from the impeller flow channel FC0 of
the first stage impeller 3a outward in the radial direction flows
through the diffuser flow channel FC4. The above-mentioned diffuser
vane 22 (the second vane) may be installed in the diffuser flow
channel FC4.
[0051] The return flow channel FC5 is constituted by a first
bending flow channel section FC6 connected to an end portion
outside in the radial direction of the diffuser flow channel FC4, a
linear flow channel section FC7 connected to an end portion of the
first bending flow channel section FC6, and a second bending flow
channel section FC8 connected to an end portion of the linear flow
channel section FC7.
[0052] The first bending flow channel section FC6 extends from the
diffuser flow channel FC4 outward in the radial direction and then
is curved inward in the radial direction. The first bending flow
channel section FC6 turns a flow of the gas G from the impeller
flow channel FC0 of the first stage impeller 3a outward in the
radial direction into a flow inward in the radial direction.
[0053] The linear flow channel section FC7 is connected to a
radially inner end of the first bending flow channel section FC6,
which is an end opposite to a connecting portion between the
diffuser flow channel FC4 and the first bending flow channel
section FC6. The linear flow channel section FC7 extends from the
first bending flow channel section FC6 inward in the radial
direction.
[0054] A return vane 23 (a first vane) configured to turn the gas G
from the impeller flow channel FC0 of the first stage impeller 3a
into a desired direction and guide the gas G to the impeller flow
channel FC0 of the second stage impeller 3b is formed in the linear
flow channel section FC7. The desired direction is, for example, a
direction in which a swirling component of the gas G from the
impeller flow channel FC0 of the first stage impeller 3a is
removed, i.e., a direction inclined rearward in the rotational
direction of the impeller 3 with respect to the radial
direction.
[0055] The second bending flow channel section FC8 is connected to
a radially inner end portion of the linear flow channel section FC7
and is curved from the end portion along the other side (a
downstream side) of the axis O. The second bending flow channel
section FC8 turns a flow of the gas G from the linear flow channel
section FC7 into a flow toward the impeller flow channel FC0 of the
second stage impeller 3b.
[0056] Here, in the embodiment, the casing flow channel FC further
includes a communication section 24 configured to bring the
diffuser flow channel FC4 extending outward in the radial direction
from the impeller flow channel FC0 of the first stage impeller 3a
and the suction flow channel FC1 in constant communication with
each other.
[0057] In the embodiment, the communication section 24 is
constituted by a plurality of communication holes formed at
intervals in the circumferential direction.
[0058] Further, a shape of the communication hole is not
particularly limited but may be a circular cross-sectional shape or
a polygonal cross-sectional shape. In addition, the communication
hole may have a slit shape. That is, the communication hole may
have any shape as long as the communication hole brings the
diffuser flow channel FC4 and the suction flow channel FC1 in
constant communication with each other, or may be formed at only
one place in the circumferential direction.
[0059] Further, when the diffuser vane 22 is formed in the diffuser
flow channel FC4, the communication section 24 may come in
communication with an outer side further in the radial direction
than the diffuser vane 22, i.e., a downstream side of a flow of the
gas G, and an outer side further in the radial direction than the
inlet guide vane 21, i.e., an upstream side of the flow of the gas
G.
[0060] Here, the suction flow channel FC1 and a portion of the
casing 4 in which the diffuser flow channel FC4 formed at the
outlet side of the impeller flow channel FC0 of the first stage
impeller 3a is formed constitute a first stage diaphragm 4a.
[0061] In addition, the return flow channel FC5 between the first
stage impeller 3a and the second stage impeller 3b, and a portion
of the casing 4 in which the diffuser flow channel FC4 formed at
the outlet side of the impeller flow channel FC0 of the second
stage impeller 3b is formed constitute a second stage diaphragm
4b.
[0062] As with the second stage diaphragm 4b, a third stage
diaphragm 4c and a fourth stage diaphragm 4d are similarly
defined.
[0063] Further, the return flow channel FC5 between the fourth
stage impeller 3d and the fifth stage impeller 3e, and a portion of
the casing 4 in which the discharge flow channel FC2 is formed
constitute a fifth stage diaphragm 4e.
[0064] In the embodiment, the communication section 24 is formed at
the first stage diaphragm 4a, and in the embodiment, a surge flow
rate when the surging occurs is designed to have a maximum value at
the first stage impeller 3a.
[0065] According to the above-mentioned multi-stage centrifugal
compressor 1, the communication section 24 is formed at the first
stage diaphragm 4a. For this reason, some of the gas G compressed
by the first stage impeller 3a can be constantly recirculated from
the diffuser flow channel FC4 to the suction flow channel FC1,
i.e., the gas G can be constantly recirculated from a downstream
side of the first stage impeller 3a at a high pressure to an
upstream side at a low pressure by differential pressure.
[0066] Here, provided that a flow rate of the gas G flowing through
the impellers 3 of the stages is 100 when some of the gas G is not
recirculated without forming the communication section 24, a total
flow rate of the gas G flowing through the impellers 3 of the
stages is 500.
[0067] In addition, when some of the gas G is not circulated
without forming the communication section 24, provided that a surge
line L0 is assumed to be as shown by a broken line of FIG. 2, an
operating point A is disposed closer to a small flow rate side than
the surge line.
[0068] In such a circumstance, as the surging occurs when an
operation of the multi-stage centrifugal compressor 1 is performed
at the operating point A, a stable operation cannot be
performed.
[0069] Meanwhile, when the communication section 24 is formed as in
the embodiment and a flow rate of the gas G recirculated through
the communication section 24 is 10, the surge line L0 appears to be
shifted 10% to the small flow rate side, and becomes a surge line L
(a solid line of FIG. 2). Accordingly, as shown in FIG. 2, when a
flow rate of the operating point A is larger than that of the surge
line L, a stable operation becomes possible.
[0070] Further, when a flow rate of 10 of the gas G for a
recirculation amount is added, since a total flow rate of the gas G
flowing through the impellers 3 of the stages is 500, power is
increased by the amount of the flow rate of 10 of the gas G in
comparison with the case in which the recirculation is not
performed. However, in the system of provisionally recirculating
the gas G through all of the stages of the system from the
downstream side of the fifth stage impeller 3e to the upstream side
of the first stage impeller 3a, a flow rate of the gas G flowing
through the impellers 3 of the stages is 110. Accordingly, power
for allowing an amount of a total flow rate of 550 of the gas G to
flow through the impellers 3 of the stages is required.
[0071] Accordingly, as in the embodiment, as the communication
section 24 is selectively applied to the impeller 3 designed to
have a largest surge flow rate and some of the gas G is circulated
through the downstream side and the upstream side of the impeller 3
of the stage in which the surge flow rate is largest upon design,
since the flow rate of the gas G of the entire system of the
multi-stage centrifugal compressor 1 can be suppressed to reduce
the power, occurrence of the surging can be effectively
suppressed.
[0072] In addition, in the case in which the diffuser vane 22 is
provisionally installed, when the communication section 24 brings
an outer side further in the radial direction than the diffuser
vane 22 in communication with an outer side further in the radial
direction than the inlet guide vane 21, the communication section
24 is disposed at a position spaced apart farther from the first
stage impeller 3a. Accordingly, the gas G recirculated through the
communication section 24 is less susceptible to an influence of
rotation of the first stage impeller 3a. Accordingly, the gas G can
be smoothly recirculated.
[0073] In addition, when the diffuser vane 22 is provisionally
installed in this way, after the gas G passing through the first
stage impeller 3a is restored to the static pressure by the
diffuser vane 22, some of the gas G can flow into the communication
section 24. Accordingly, the gas G can easily enter the
communication section 24, and the fluid can be stably and smoothly
circulated to the upstream side of the impeller 3 through the
communication section 24.
[0074] Further, since the communication section 24 is a simple
communication hole or slit, there is no member to block the flow of
the gas G in the communication section 24, a pressure drop upon
recirculation can be suppressed to a low level, and the gas G can
be smoothly recirculated.
[0075] According to the multi-stage centrifugal compressor 1 of the
embodiment, as the communication section 24 for constant
communication is provided, the occurrence of surging can be
suppressed while suppressing an increase in power of the entire
system of the multi-stage centrifugal compressor 1 to a minimum
level.
[0076] Further, the communication section 24 of the embodiment may
not bring an outer side further in the radial direction than the
diffuser vane 22 in communication with an outer side further in the
radial direction than the inlet guide vane 21.
[0077] That is, the communication section 24 may be formed to bring
at least the downstream side and the upstream side of the first
stage impeller 3a in communication with each other.
[0078] Here, when the surge flow rate is provisionally designed to
be maximally increased at the second stage impeller 3b, as shown in
FIG. 3, the communication section 24 is formed at the second stage
diaphragm 4b and may bring the downstream side and the upstream
side of the second stage impeller 3b in communication with each
other. Even in this case, the occurrence of surging can be
suppressed while suppressing an increase in power of the entire
system of the multi-stage centrifugal compressor 1 to a minimum
level.
[0079] Similarly, when the surge flow rate is provisionally
designed to be maximally increased at the third stage impeller 3c,
the communication section 24 may be formed at the third stage
diaphragm 4c.
[0080] In addition, when the surge flow rate is designed to be
maximally increased at the fourth stage impeller 3d, the
communication section 24 may be formed at the fourth stage
diaphragm 4d.
[0081] Further, when the surge flow rate is provisionally designed
to be maximally increased at the fifth stage impeller 3e, the
communication section 24 may be configured as shown in FIG. 4.
Specifically, the communication section 24 may be formed to bring
an outer side further in the radial direction than the diffuser
vane 22 of the outlet side of the flow rate of the impeller 3 of
the fifth stage impeller 3e and an outer side further in the radial
direction than the return vane 23 of the inlet side of the flow
rate of the impeller 3 of the fifth stage impeller 3e in
communication with each other. Then, as shown in FIG. 4, the
communication section 24 may come in communication with the
discharge scroll S.
[0082] In addition, when the surge flow rate is provisionally
designed to be maximally increased at the fourth stage impeller 3d
and the fifth stage impeller 3e, as shown in FIG. 5, the
communication section 24 may be configured as shown in FIG. 5.
Specifically, the communication section 24 is formed to bring an
outer side further in the radial direction than the diffuser vane
22 of the outlet side of the flow rate of the impeller 3 of the
fifth stage impeller 3e and an outer side further in the radial
direction than the return vane 23 of the inlet side of the flow
rate of the impeller 3 of the fourth stage impeller 3d in
communication with each other. That is, in this case, it is also
considered that the fourth stage diaphragm 4d and the fifth stage
diaphragm 4e constitute a diaphragm of the first stage.
[0083] Further, FIG. 6 shows another variant of the embodiment. In
the variant, communication sections 24 are formed at the diaphragms
4a to 4e of all of the stages. That is, the communication section
24 is formed to bring the downstream sides and upstream sides of
the impellers 3 of all of the stages in communication with each
other.
[0084] In addition, the communication sections 24 have different
flow channel areas, through which the gas G flows, according to the
diaphragms 4a to 4e of the stages. For example, while hole
diameters are different from each other according to the diaphragms
4a to 4e when the communication sections 24 are the communication
holes, the number of communication holes can be different.
[0085] According to the above-mentioned multi-stage centrifugal
compressor 1, as the flow channel areas of the communication
sections 24 are different in each of the diaphragms 4a to 4e, in
combination with the surge flow rates that are different according
to the impellers 3 of the stages, a flow rate of the gas G
recirculated from the downstream sides to the upstream sides of the
impellers 3 through the communication sections 24 can be
adjusted.
[0086] That is, the flow rate of the gas G recirculated according
to specifications of the stages can be adjusted, and it is possible
to approach a state in which surge occurring at all of the stages
is eliminated. Accordingly, the occurrence of the surging can be
more effectively suppressed.
[0087] Hereinabove, while the embodiments of the present invention
have been described in detail, some design modifications may be
made without departing from the technical spirit of the present
invention.
[0088] For example, in the above-mentioned embodiment, while the
multi-stage centrifugal compressor 1 has been described as an
example of the centrifugal rotating machine, the diaphragm of the
above-mentioned embodiment may be applied to another centrifugal
rotating machine such as a multi-stage centrifugal pump or the like
configured to pump a liquid instead of the gas G.
INDUSTRIAL APPLICABILITY
[0089] According to the aspects of the present invention,
occurrence of surging can be suppressed while maintaining
compression efficiency.
REFERENCE SIGNS LIST
[0090] 1 Multi-stage centrifugal compressor (rotating machine)
[0091] 2 Rotary shaft
[0092] 3 Impeller
[0093] G Gas (fluid)
[0094] 3a First stage impeller
[0095] 3b Second stage impeller
[0096] 3c Third stage impeller
[0097] 3d Fourth stage impeller
[0098] 3e Fifth stage impeller
[0099] 4 Casing
[0100] 4a First stage diaphragm
[0101] 4b Second stage diaphragm
[0102] 4c Third stage diaphragm
[0103] 4d Fourth stage diaphragm
[0104] 4e Fifth stage diaphragm
[0105] 7 Journal bearing
[0106] 8 Thrust bearing
[0107] 11 Hub
[0108] 12 Blade
[0109] 13 Shroud
[0110] 21 Inlet guide vane (first vane)
[0111] 22 Diffuser vane
[0112] 23 Return vane (first vane)
[0113] 24 Communication section
[0114] FC Casing flow channel
[0115] FC0 Impeller flow channel
[0116] FC1 Suction flow channel (inlet-side flow channel)
[0117] FC2 Discharge flow channel (outlet-side flow channel)
[0118] FC3 Intermediate flow channel
[0119] FC4 Diffuser flow channel (outlet-side flow channel)
[0120] FC5 Return flow channel (inlet-side flow channel)
[0121] FC6 First bending flow channel section
[0122] FC7 Linear flow channel section
[0123] FC8 Second bending flow channel section
[0124] S Discharge scroll
[0125] O Axis
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