U.S. patent application number 14/366910 was filed with the patent office on 2014-12-18 for centrifugal compressor.
The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES COMPRESSOR CORPORATION, MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Shuichi Yamashita.
Application Number | 20140369823 14/366910 |
Document ID | / |
Family ID | 48799138 |
Filed Date | 2014-12-18 |
United States Patent
Application |
20140369823 |
Kind Code |
A1 |
Yamashita; Shuichi |
December 18, 2014 |
CENTRIFUGAL COMPRESSOR
Abstract
A centrifugal compressor for which .theta.-.alpha.>0.degree.
and 0.degree.<.theta.<34.degree., when the angle formed by a
diffuser inlet hub-side line (5a) and the radial direction at a
point B in the meridian plane is .theta., and the angle formed by a
tangent line (3b) and the radial direction at a point A of an
impeller hub-side line (3a) nearest the inlet of the diffuser (5)
is .alpha.. Thus, skewing of the velocity distribution of a gas
within the diffuser of the centrifugal compressor is
eliminated.
Inventors: |
Yamashita; Shuichi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES, LTD.,
MITSUBISHI HEAVY INDUSTRIES COMPRESSOR CORPORATION |
Tokyo
Tokyo |
|
JP
JP |
|
|
Family ID: |
48799138 |
Appl. No.: |
14/366910 |
Filed: |
January 11, 2013 |
PCT Filed: |
January 11, 2013 |
PCT NO: |
PCT/JP2013/050360 |
371 Date: |
June 19, 2014 |
Current U.S.
Class: |
415/203 |
Current CPC
Class: |
F04D 29/284 20130101;
F04D 29/444 20130101; F04D 17/10 20130101; F04D 29/441
20130101 |
Class at
Publication: |
415/203 |
International
Class: |
F04D 29/44 20060101
F04D029/44; F04D 17/10 20060101 F04D017/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2012 |
JP |
2012-006714 |
Claims
1. A centrifugal compressor comprising: an impeller connected to a
rotary shaft via a hub; and a diffuser provided downstream of the
impeller, the diffuser having a flow passage which extends in a
direction away from the rotary shaft and an outlet which is
directed in a radial direction in a meridian plane, characterized
in that the centrifugal compressor satisfies
.theta.-.alpha.>0.degree. where .theta. is an angle formed by a
diffuser inlet hub-side line with the radial direction in the
meridian plane at a point closest to an outlet of the impeller in
the diffuser inlet hub-side line, the diffuser inlet hub-side line
being a line on the hub side in an inlet of the diffuser, and
.alpha. is an angle formed by a tangent line of an impeller
hub-side line with the radial direction in the meridian plane at a
point closest to the inlet of the diffuser in the impeller hub-side
line, the impeller hub-side line being a line on the hub side in
the impeller, and a rear edge of the impeller has an inclined
angle, the diffuser inlet hub-side line is a straight line, and an
angle formed by the diffuser inlet hub-side line and the rear edge
of the impeller is substantially 90.degree. or more.
2. The centrifugal compressor according to claim 1, characterized
in that the .theta. is such that
0.degree.<.theta.<34.degree..
3. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a centrifugal compressor,
and particularly to a centrifugal compressor with a large flow
rate.
BACKGROUND ART
[0002] For improving the performances of products such as
superchargers, gas turbines, and industrial compressors, it is a
critical issue to increase the flow rate. Increasing the flow rate
of a centrifugal compressor means to increase the discharge flow
rate of a compressor with the same shell size, and further of an
impeller with the same outer diameter.
[0003] One of the problems associated with the increase in flow
rate is a decrease in efficiency. For this reason, a technique of
increasing the flow rate while suppressing the decrease in
efficiency is industrially very significant.
[0004] A conventional centrifugal compressor will be described by
using FIG. 6. The centrifugal compressor mainly includes a suction
inlet 1, an impeller 2, a hub 3, a rotary shaft 4, a diffuser 5,
and a scroll 6.
[0005] The impeller 2 is connected to the rotary shaft 4 via the
hub 3. The diffuser 5 is provided downstream of the impeller 2, has
a flow passage extending in a direction away from the rotary shaft
4, and has an outlet directed in a radial direction in a meridian
plane. Moreover, the scroll 6 is provided downstream of the
diffuser 5 and communicates with the outlet of the diffuser 5.
[0006] The suction inlet 1 plays a roll of guiding a gas to the
impeller 2. The centrifugal compressor is configured such that the
gas guided to the impeller 2 is sucked into the centrifugal
compressor by the impeller 2 being rotated by the rotary shaft 4.
The velocity of the gas having passed through the impeller 2 is
decreased, and the pressure of the gas is increased, in the
diffuser 5. The gas having passed through the diffuser 5 flows into
the scroll 6, and thereafter flows into a discharge port, which is
not shown. In this way, the centrifugal compressor converts the
kinetic energy of the gas to a pressure.
[0007] FIG. 7 is a cross-sectional view of the diffuser 5 and the
impeller 2 of the conventional centrifugal compressor. The more the
velocity vector of the gas (the arrow in the figure) is directed in
a radial direction in the meridian plane, the less the energy loss
is. However, a large flow rate causes the velocity distribution of
the gas sacked through an impeller inlet 2a to be skewed to the hub
3 side at an impeller outlet 2b. As a result, the velocity vector
is inclined toward an axial direction from the radial direction. In
addition, if the gas flows further inside the diffuser 5 in this
state, the velocity distribution is further skewed to become a
cause of occurrence of shear stress, reducing the amount of static
pressure recovery, and in turn leading to a decrease in efficiency
of the entire compressor.
[0008] To solve the above-described problem, there is a method of
bringing the velocity distribution of the gas into a more uniform
distribution by providing the inside of the diffuser with a guide
blade (see Patent Document 1) or a guide flow passage to the
impeller inlet (see Patent Document 2).
PRIOR ART DOCUMENTS
Patent Documents
[0009] PATENT DOCUMENT 1: Japanese Patent No. 2569143
[0010] PATENT DOCUMENT 2: Japanese Patent No. 2703055
SUMMARY OF THE INVENTION
Problems To Be Solved by the Invention
[0011] However, the above-described apparatuses require that new
mechanisms should be provided in the diffuser, and have a
possibility that the production costs and working hours are
wasted.
[0012] In view of this, an object of the present invention is to
solve the problems of the conventional techniques and to achieve
higher efficiency in a centrifugal compressor with a large flow
rate, not by providing a new mechanism, but by changing a shape of
a diffuser.
Means for Solving the Problems
[0013] A centrifugal compressor according to a first invention for
solving the above-described problems is a centrifugal compressor
comprising:
[0014] an impeller connected to a rotary shaft via a hub; and
[0015] a diffuser provided downstream of the impeller, the diffuser
having a flow passage which extends in a direction away from the
rotary shaft and an outlet which is directed in a radial direction
in a meridian plane, characterized in that
[0016] the centrifugal compressor satisfies
.theta.-.alpha.>0.degree.
[0017] where
[0018] .theta. is an angle formed by a diffuser inlet hub-side line
with the radial direction in the meridian plane at a point closest
to an outlet of the impeller in the diffuser inlet hub-side line,
the diffuser inlet hub-side line being a line on the hub side in an
inlet of the diffuser, and
[0019] .alpha. is an angle formed by a tangent line of an impeller
hub-side line with the radial direction in the meridian plane at a
point closest to the inlet of the diffuser in the impeller hub-side
line, the impeller hub-side line being a line on the hub side in
the impeller.
[0020] A centrifugal compressor according to a second invention for
solving the above-described problems is the centrifugal compressor
according to the first invention, characterized in that the .theta.
is such that 0.degree.<.theta.<34.degree..
[0021] A centrifugal compressor according to a third invention for
solving the above-described problems is the centrifugal compressor
according to the first or second invention, characterized in
that
[0022] the diffuser inlet hub-side line is a concave curved
line.
Effect of the Invention
[0023] According to the centrifugal compressor of the first
invention, since .theta.-.alpha.>0.degree., skewing of the
velocity distribution of the gas is eliminated, and accordingly a
decrease in amount of static pressure recovery is suppressed.
Therefore, a higher efficiency of the entire compressor can be
achieved.
[0024] According to the centrifugal compressor of the second
invention, since 0.degree.<.theta.<34.degree., the skewing of
the velocity distribution of the gas can be further eliminated.
[0025] According to the centrifugal compressor of the third
invention, since the diffuser inlet hub-side line is a concave
curved line, a stagnation region inside the diffuser is reduced.
Therefore, a further higher efficiency can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a cross-sectional view of a diffuser and an
impeller of a centrifugal compressor according to Embodiment 1 of
the present invention.
[0027] FIG. 2 is a graph showing a relationship between .theta. and
an efficiency improvement rate of the centrifugal compressor
according to Embodiment 1 of the present invention.
[0028] FIG. 3 is a cross-sectional view of a diffuser and an
impeller of a centrifugal compressor according to Embodiment 2 of
the present invention.
[0029] FIG. 4 is a schematic view showing differences between the
centrifugal compressor according to Embodiment 1 of the present
invention and the centrifugal compressor according to Embodiment 2
of the present invention.
[0030] FIG. 5 is a schematic diagram showing a relationship between
.theta. and .alpha. of the centrifugal compressor according to
Embodiment 1 or 2 of the present invention.
[0031] FIG. 6 is a cross-sectional view of a conventional
centrifugal compressor.
[0032] FIG. 7 is a cross-sectional view of a diffuser and an
impeller of the conventional centrifugal compressor.
MODES FOR CARRYING OUT THE INVENTION
[0033] Hereinafter, a centrifugal compressor according to the
present invention will be described referring to embodiments by use
of the drawings.
Embodiment 1
[0034] An apparatus according to Embodiment 1 of the present
invention will be described by use of FIG. 1. The apparatus mainly
includes a suction inlet 1, an impeller 2, a hub 3, a rotary shaft
4, a diffuser 5, and a scroll 6, as in the case of the conventional
centrifugal compressor. The impeller 2 is connected to the rotary
shaft 4 via the hub 3. In addition, the diffuser 5 is provided
downstream of the impeller 2, has a flow passage directed in a
direction away from the rotary shaft 4, and has an outlet directed
in a radial direction in a meridian plane. Moreover, the scroll 6
is provided downstream of the diffuser 5, and communicates with an
outlet of the diffuser 5. Note that the rotary shaft 4 and the
scroll 6 are not shown in FIG. 1, but are assumed to be the same as
those of the conventional technical.
[0035] Furthermore, like the conventional technique, the suction
inlet 1 plays a role of guiding a gas to the impeller 2. The
centrifugal compressor is configured such that the gas guided to
the impeller 2 is sucked into the centrifugal compressor by the
impeller 2 being rotated by the rotary shaft 4. The velocity of the
gas having passed through the impeller 2 is decreased, and the
pressure of the gas is increased, in the diffuser 5. The gas having
passed through the diffuser 5 flows into the scroll 6, and
thereafter flows into a discharge port.
[0036] Here, a line on the hub 3 side in the inlet of the diffuser
5 (hereinafter, stated as a diffuser inlet hub-side line 5a) is
inclined toward an axial direction from the radial direction in the
meridian plane. At this time, an angle formed by the diffuser inlet
hub-side line 5a with the radial direction at a point B closest to
the impeller outlet 2b in the diffuser inlet hub-side line 5a is
represented by .theta..
[0037] Next, an angle formed by a tangent line 3b of a line on the
hub 3 side in the impeller 2 (hereinafter, stated as an impeller
hub-side line 3a) with the radial direction at a point A closest to
an inlet of the diffuser 5 in the impeller hub-side line 3a is
represented by .alpha..
[0038] The conventional technique is set such that .theta.=.alpha.
in order to smoothly connect the impeller hub-side line 3a and the
diffuser inlet hub-side line 5a. On the other hand, the present
apparatus is set such that .theta.-.alpha.>0.degree. as shown in
FIG. 5, and further .theta. is set such that
0.degree.<.theta.<34.degree..
[0039] In addition, an angle formed by the impeller rear edge 2c
with the axial direction is represented by .beta.. Here, .beta. has
not necessary to be limited, but is set such that
0.degree..ltoreq..beta..ltoreq.35.degree., which is a value used in
a general centrifugal compressor.
[0040] Note that a line of the shroud 7 is also inclined in
conjunction with the inclination of .theta. to confirm with a
diffuser width ratio of the conventional shape. The diffuser width
ratio is b.sub.3/b.sub.2 (see FIG. 1), and has a value set for each
impeller. In general, the value of the diffuser width ratio is set
such that b.sub.3/b.sub.2=0.6 to 1.0.
[0041] With the above-described structure, while the velocity
vector of the gas at the time when the gas has flowed from the
impeller outlet 2b to the diffuser 5 is not changed from that of
the conventional one, the skewing of the velocity distribution can
be suppressed.
[0042] FIG. 2 shows a result of simulation of the compressor
efficiency of the present apparatus, conducted under conditions
that .alpha. and .beta. are certain constant values and only
.theta. is a variable. In a graph of FIG. 2, the horizontal axis
represents .theta. and the vertical axis represents a compressor
efficiency improvement rate. The compressor efficiency improvement
rate represents a difference, expressed in percentage, between the
compressor efficiency of the present apparatus and the compressor
efficiency of the conventional technique. As becoming higher in the
graph, the compressor efficiency improvement rate indicates that
the compressor efficiency of the present apparatus is higher. It
can be understood from the graph that the compressor efficiency is
improved when 0.degree.<.theta.<34.degree..
[0043] Accordingly, in the present apparatus, the skewing of the
velocity distribution of the gas in the diffuser, which has
conventionally occurred, is eliminated, and accordingly a decrease
in the amount of static pressure recovery in the diffuser is
suppressed. Therefore, a higher efficiency of the entire compressor
can be achieved.
Embodiment 2
[0044] An apparatus according to Embodiment 2 of the present
invention is one obtained by improving the apparatus according to
Embodiment 1. FIG. 4 shows differences between the apparatus
according to Embodiment 1 and the present apparatus. In the
apparatus according to Embodiment 1, since the diffuser inlet
hub-side line 5a is a straight line, directing the outlet of the
diffuser 5 in the radial direction requires that the angle of the
diffuser 5 has to be changed at a certain portion. As a result, as
shown in FIG. 4, a stagnation region 11 where the flow of the gas
stagnates is formed. Shear stress acts between the gas stagnating
in the stagnation region 11 and the flowing gas, leading to a
possibility of occurrence of an energy loss. The present apparatus
reduces the stagnation region 11.
[0045] As in the case of the apparatus according to Embodiment 1,
as shown in FIG. 3, the present apparatus mainly includes a suction
inlet 1, an impeller 2, a hub 3, a rotary shaft 4, a diffuser 5,
and a scroll 6. The impeller 2 is connected to the rotary shaft 4
via the hub 3. The diffuser 5 is provided downstream of the
impeller 2, has a flow passage extending in a direction away from
the rotary shaft 4, and has an outlet directed in a radial
direction in a meridian plane. Moreover, the scroll 6 is provided
downstream of the diffuser 5 and communicates with the outlet of
the diffuser 5. Note that the rotary shaft 4 and the scroll 6 are
not shown in FIG. 3, but are assumed to be the same as those of the
conventional technique. Furthermore, the operation of the present
apparatus is also the same as those of the apparatus according to
Embodiment 1 and of the conventional technique, and is accordingly
omitted.
[0046] Here, in the present apparatus, the diffuser inlet hub-side
line 5b is made to be a concave curved line. An angle formed by a
tangent line 5c of the diffuser inlet hub-side line 5b with a
radial direction at a point B closest to an impeller outlet 2b in
the diffuser inlet hub-side line 5b is represented by .theta.. The
line of the shroud 7, .alpha., and .beta. are set such that
.theta.-.alpha.>0.degree. as shown in FIG. 5, and further
.theta. is set such that 0.degree.<.theta.<34.degree. as in
the case of the apparatus according to Embodiment 1. Note that the
diffuser inlet hub-side line 5b may be a single arc, or may be a
line obtained by smoothly combining a plurality of arcs or ovals,
as long as it is a curved line.
[0047] With the above-described structure, as shown in FIG. 4, the
present apparatus can reduce the stagnation region 11, which exists
in the case of the apparatus according to Embodiment 1. Therefore,
the present apparatus can reduce shear stress and makes it possible
to achieve higher efficiency.
INDUSTRIAL APPLICABILITY
[0048] The present invention is favorable as a centrifugal
compressor, and in particular a centrifugal compressor with a large
flow rate.
EXPLANATION OF REFERENCE NUMERALS
[0049] 1 suction inlet [0050] 2 impeller [0051] 2a impeller inlet
[0052] 2b impeller outlet [0053] 2c impeller rear edge [0054] 3 hub
[0055] 3a impeller hub-side line [0056] 3b tangent line [0057] 4
rotary shaft [0058] 5 diffuser [0059] 5a diffuser inlet hub-side
line (in the apparatus according to Embodiment 1 of the present
invention) [0060] 5b diffuser inlet hub-side line (in the apparatus
according to Embodiment 2 of the present invention) [0061] 5c
tangent line [0062] 6 scroll [0063] 7 shroud [0064] 11 stagnation
region
* * * * *