Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Reexamination Certificate
2001-03-27
2002-12-31
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
C416S19800R, C416S19800R, C415S199100
Reexamination Certificate
active
06499955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a centrifugal compressor capable of compressing a fluid, in particular to a centrifugal compressor structure with impellers adapted to convert kinetic energy generated from a motor into pressure energy, in which each of the impellers adjusts an axial load, thereby appropriately adjusting a load applied to a thrust bearing.
2. Description of the prior Art
Generally, compressors are adapted to convert mechanical energy generated by a motor into pressure energy, thereby increasing the pressure of a fluid. In particular, centrifugal compressors, to which the present invention relates, are adapted to conduct a compression for a fluid by use of the rotating force of an impeller while sucking the fluid in an axial direction, and discharging the sucked fluid in a centrifugal direction. Typically, such centrifugal compressors include multiple stages so that they operate in a multi-stage compression. In particular, two-stage centrifugal compressors including two stages of compression are mainly used.
Such centrifugal compressors are mainly used in air conditioners and specific military equipment. In accordance with the capacity of a fluid to be compressed, centrifugal compressors are classified into those of a large capacity and those of a small capacity.
FIG. 1
is a sectional view illustrating the structure of a conventional two-stage centrifugal compressor.
Referring to
FIG. 1
, the conventional two-stage centrifugal compressor is of a back-to-back type in which impellers face each other at their back surfaces. Now, the structure of this centrifugal compressor will be described in conjunction with FIG.
1
.
As shown in
FIG. 1
, the centrifugal compressor includes a motor case
1
having a desired shape to receive units including a motor while isolating those units from the outside. The motor, which is denoted by the reference numeral
2
, is also included in the centrifugal compressor. The motor
2
is disposed in the motor case
1
and adapted to convert electric energy into mechanical kinetic energy.
The centrifugal compressor also includes a drive shaft
3
axially coupled to the motor
2
to rotate along with the drive shaft
3
. A pair of impellers, that is, a first impeller
4
and a second impeller
5
, are coupled to opposite ends of the drive shaft
3
, respectively, and convert a rotating movement of the drive shaft
3
into kinetic energy to be applied to a fluid. The centrifugal compressor further includes thrust bearings
6
disposed at a portion of the drive shaft
3
in the vicinity of a first end of the drive shaft
3
. The thrust bearings
6
are adapted to gently support a thrust load axially applied to the drive shaft
3
.
A pair of radial bearings
7
and
8
are respectively disposed at portions of the drive shaft
3
in the vicinity of opposite ends of the drive shaft
3
. The radial bearings
7
and
8
are adapted to radially support the drive shaft
3
, thereby gently supporting a radial load. A pair of bearing plates, that is, a first bearing plate
9
and a second bearing plate
10
, each interposed between the motor case
1
and an associated one of the radial bearings
7
and
8
, are adapted to allow the associated radial bearing to be supported by the motor case
1
.
A bearing cover
11
is fitted around the first end of the drive shaft
3
installed with the trust bearings
6
while being fitted in a first end of the motor case
1
corresponding to the end of the drive shaft
3
. The bearing cover
11
seals the interior of the motor case
1
. A pair of diffusers, that is, a first diffuser
12
and a second diffuser
13
, are arranged at respective discharge ends of the impellers
4
and
5
in order to convert kinetic energy, possessed in the fluid discharged at a high velocity from the impellers
4
and
5
, into pressure energy.
A first volute case
14
is mounted to the outside of the first diffuser
12
. The first volute case
14
has a desired shape to collect the fluid discharged in a compressed state from the first diffuser
12
while reducing the pressure energy possessed in the discharged fluid. A connecting tube
15
is connected at one end thereof to the first volute case
14
to guide the fluid discharged from the first volute case
14
toward the second impeller
5
. A second volute case
16
is mounted to the outside of the second diffuser
13
. The second volute case
16
is connected to the other end of the connecting tube
15
to temporarily collect the fluid emerging from the connecting tube
15
, and then being compressed again while passing sequentially through the second impeller
5
and the second diffuser
13
.
The centrifugal compressor further includes a plurality of uniformly-spaced fluid passages
17
. The fluid passages
17
extend axially through the second bearing plate
10
and are adapted to allow the high pressure fluid collected in the second volute case
16
to be discharged from the second volute case
16
. A motor chamber
18
is defined between the first and second bearing plates
9
and
10
in the interior of the motor case
1
. The motor chamber
18
receives the fluid discharged through the fluid passages
17
and allows the received fluid to stay temporarily therein while cooling the motor
2
.
The centrifugal compressor also includes a labyrinth seal
19
formed at a surface of the bearing cover
11
contacting the drive shaft
3
. The labyrinth seal
19
is adapted to prevent the high pressure fluid filled in the motor chamber
18
from being leaked outwardly from the motor chamber
18
. A discharge tube
20
is connected at one end thereof to a desired portion of the motor case
1
, while communicating with the motor chamber
18
and adapted to discharge the high pressure fluid from the motor chamber
18
. A suction tube
21
is connected to the first volute case
14
upstream from the first impeller
4
.
The operation of the two-stage centrifugal compressor will now be described in brief. A fluid to be compressed is introduced into the centrifugal compressor via the suction tube
21
. The introduced fluid is primarily compressed by the first impeller
4
, and then forced to pass through the first diffuser
12
, so that it is highly pressurized. The high pressure fluid is then collected by the first volute case
14
without any loss of pressure. The collected fluid is introduced into the second impeller
5
which, in turn, secondarily compresses the fluid. The secondarily compressed fluid is then further compressed to a higher pressure while passing through the second diffuser
13
, and then collected in the second volute case
16
. The high pressure fluid is then introduced into the motor chamber
18
via the fluid passages
17
, so that it cools the motor
2
heated to a high temperature. After cooling the motor
2
, the fluid is outwardly discharged from the motor chamber
18
via the discharge tube
20
.
During the above operation, considerably high pressure is applied to the first and second impellers
4
and
5
. Due to such high pressure, a high load is applied to the thrust bearings
6
. Now, effects resulting from such a load will be described in detail.
FIG. 2
is a plan view illustrating one of the impellers used in the above mentioned conventional centrifugal compressor, that is, the impeller
4
.
Referring to
FIG. 2
, the impeller
4
has a structure in which a plurality of blades
4
b
are mounted around a cylindrical hub
4
a
. Once an external fluid is axially introduced into the center of the impeller
4
during a rotation of the impeller
4
, it is then forced to move in a centrifugal direction along the blades
4
b
conducting a rotation. As the fluid moves in the centrifugal direction, it possesses kinetic energy, so that it is converted into a fluid having high energy, that is, a high pressure fluid flowing at a high velocity.
FIG. 3
is a sectional view illustrating the impeller
4
used in the conventional centrifugal compressor.
As shown in FIG.
3
and mentioned above, the impeller
4
includ
Choi Moon-Chang
Ji Yoo-Chol
Kim Young-Kwan
Lee Sang-Wook
Suh Kwang-ha
LG Electronics Inc.
Look Edward K.
Nguyen Ninh
LandOfFree
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