JP2001123997A - Centrifugal compressor with magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the consumption of cooling air and to improve economics by preventing high-temperature gas from leaking from an impeller to a magnetic bearing, in a centrifugal compressor mounted with a magnetic bearing. SOLUTION: Compressed gas downstream of an inter-cooler 11a is introduced to a magnetic bearing 6a of a first stage impeller side, and compressed gas downstream of an after-cooler 11b is introduced to a magnetic bearing 6b on a second stage impeller side. Therefore, high-temperature gas is prevented from leaking from impellers 4a, 4b to the magnetic bearings 6a, 6b, the consumption of cooling air is reduced, and the economics is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for supplying magnetic bearing cooling gas in a two-stage centrifugal compressor in which a rotating shaft is supported by magnetic bearings.

[0002]

2. Description of the Related Art A two-stage centrifugal compressor equipped with a magnetic bearing and having a structure in which the magnetic bearing is cooled by ventilating gas is disclosed in Japanese Patent Application Laid-Open No. 10-89296. Machines are known.

[0003] This multi-stage compressor extracts a cooling gas of a magnetic bearing from an extraction unit located downstream of a gas cooler downstream of a first stage compressor and an extraction unit located in an air discharge passage downstream of an air release valve. Then, these extraction paths are switched and supplied to the magnetic bearing according to the load operation and the no-load operation of the compressor.

Further, in this multi-stage compressor, the pressure is reduced to such an extent that a required amount of cooling air can be ensured before the supply.
For this reason, the pressure on the back surface of the impeller becomes higher than the pressure of the cooling air, and high-temperature gas compressed by the impeller leaks from the impeller side to the magnetic bearing side. Therefore, this compressor is provided with a discharge port for discharging the compressed gas leaking from the impeller side to the magnetic bearing side to the outside of the compressor.

[0005]

In the conventional two-stage centrifugal compressor, the pressure of the magnetic bearing cooling gas is lower than the pressure at the back of the impeller, and the high-temperature gas compressed by the impeller leaks to the magnetic bearing. Therefore, in order to sufficiently cool the magnetic bearing portion, it was necessary to increase the flow rate of the cooling gas. This increases the power of the compressor, especially when a part of the gas handled by the compressor is used for cooling the magnetic bearings, which is uneconomical.

In order to prevent insufficient cooling of the magnetic bearing due to such leakage, it is necessary to provide a discharge port for discharging the high-temperature compressed gas leaking from the impeller to the outside of the machine. In this case, the structure of the compressor is complicated, the processing cost is increased, and it is necessary to manage the discharge passage.

Therefore, a first object of the present invention is to provide an electric motor substantially at the center of a rotating shaft supported by a magnetic bearing,
A two-stage centrifugal compressor having a first-stage impeller at one end of the rotating shaft and a second-stage impeller at the other end, wherein an intercooler is provided downstream of the first-stage compression stage, and an aftercooler is provided downstream of the second-stage compressor. In the centrifugal compressor equipped with a magnetic bearing, which extracts a part of the compressed gas from the downstream of the cooler and supplies the compressed gas to the vicinity of the magnetic bearing, the magnetic bearing on the first stage impeller side has the compression downstream of the intercooler. By introducing compressed gas downstream of the aftercooler to the magnetic bearing on the side of the second stage impeller, the gas is prevented from leaking high-temperature gas from the impeller to the magnetic bearing, and cooling air consumption is reduced. An object of the present invention is to provide a magnetic bearing-mounted centrifugal compressor with improved economic efficiency.

A second object of the present invention is to provide an electric motor substantially at the center of a rotating shaft supported by a magnetic bearing, a first-stage impeller at one end of the rotating shaft, and a second-stage blade at the other end. In a two-stage centrifugal compressor having a wheel, a magnetic bearing mounted centrifugal compressor having a supply port for supplying a magnetic bearing cooling gas to the vicinity of the magnetic bearing, wherein a supply port and a space behind the impeller are separated by a labyrinth. , The pressure of the magnetic bearing cooling gas introduced into the supply port is higher than the gas pressure on the labyrinth impeller side, preventing high-temperature gas from leaking from the impeller to the magnetic bearing and reducing cooling air consumption Another object of the present invention is to provide a magnetic bearing-mounted centrifugal compressor with improved economic efficiency.

[0009]

According to the present invention, there is provided, in accordance with the present invention, an electric motor substantially at the center of a rotating shaft supported by a magnetic bearing, and a first stage provided at one end of the rotating shaft. A two-stage centrifugal compressor having an impeller and a second-stage impeller at the other end, wherein an intercooler and a second
In a magnetic bearing-mounted centrifugal compressor that has an aftercooler downstream of the stage compressor and extracts a part of the compressed gas from downstream of these coolers and supplies the compressed gas to the vicinity of the magnetic bearing, the first stage impeller side magnet By introducing compressed gas downstream of the intercooler to the bearing and compressed gas downstream of the aftercooler to the magnetic bearing on the second stage impeller side, high-temperature gas is prevented from leaking from the impeller to the magnetic bearing, and cooling is performed. 2. Description of the Related Art A centrifugal compressor equipped with a magnetic bearing that has reduced air consumption and improved economic efficiency has been proposed.

According to the present invention, in order to achieve the above object, an electric motor is provided at a substantially central portion of a rotating shaft supported by a magnetic bearing, and a first-stage impeller is provided at one end of the rotating shaft. A two-stage centrifugal compressor having a second-stage impeller at an end, the magnetic bearing-mounted centrifugal compressor having a supply port for supplying a magnetic bearing cooling gas to a vicinity of the magnetic bearing, wherein a space between the supply port and a back surface of the impeller is provided. And with a labyrinth,
By setting the pressure of the magnetic bearing cooling gas introduced into the supply port higher than the gas pressure on the labyrinth impeller side, high temperature gas is prevented from leaking from the impeller to the magnetic bearing, and cooling air consumption is reduced. A centrifugal compressor equipped with a magnetic bearing with improved economic efficiency has been proposed.

That is, according to the centrifugal compressor equipped with a magnetic bearing according to the present invention, an electric motor is provided substantially at the center of the rotating shaft supported by the magnetic bearing, and the first end is provided at one end of the rotating shaft.
A two-stage centrifugal compressor having a stage impeller and a second stage impeller at the other end, comprising an intercooler downstream of the first stage compression stage, an aftercooler downstream of the second stage compressor, and downstream of these coolers. In the magnetic bearing-mounted centrifugal compressor that extracts a part of the compressed gas from and supplies it to the vicinity of the magnetic bearing, the first stage impeller side magnetic bearing is provided with the compressed gas downstream of the intercooler,
By introducing the compressed gas downstream of the aftercooler to the magnetic bearing on the second stage impeller side, high temperature gas is prevented from leaking from the impeller to the magnetic bearing, and cooling air consumption is reduced.
Economy can be improved.

Further, according to the centrifugal compressor equipped with a magnetic bearing according to the present invention, an electric motor is provided substantially at the center of the rotating shaft supported by the magnetic bearing, and the first shaft is provided at one end of the rotating shaft.
A stepped impeller, a two-stage centrifugal compressor having a second-stage impeller at the other end, wherein the magnetic bearing mounted centrifugal compressor has a supply port for supplying a magnetic bearing cooling gas to the vicinity of the magnetic bearing.
The supply port and the space behind the impeller are separated by a labyrinth, and the pressure of the magnetic bearing cooling gas introduced into the supply port is made higher than the gas pressure on the labyrinth impeller side. To prevent leakage,
Cooling air consumption can be reduced and economy can be improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a first embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention. In the first embodiment, the rotating shaft is supported by a magnetic bearing.
FIG. 1 shows a schematic flow chart of a single-stage centrifugal air compressor. FIG. 2 shows a schematic structure near the first stage impeller and the first stage impeller side magnetic bearing of the first embodiment shown in FIG.

1 and 2, a two-stage centrifugal compressor 1
The compressors 1a and 1b constituting the first and second stages have impellers 4a and 4b, respectively, and are driven by a motor 2 having output shafts at both shaft ends via a rotating shaft 3. . The electric motor 2 is a high-speed electric motor in which the rotating shaft 3 is supported by radial magnetic bearings 6a and 6b and an axial magnetic bearing 7.

The impeller 4a and the magnetic bearing 6a are separated by labyrinths 22a and 23a.
The impeller 4b and the magnetic bearing 6b are partitioned by labyrinths 22b and 23b. The space between the labyrinths 22a and 23a is in communication with the outside via the supply port 27a. Similarly, the space between the labyrinths 22b and 23b is also in communication with the outside via the supply port. Note that FIG.
1 shows an auxiliary bearing 25a and a displacement sensor 26a between the labyrinth 22a and the magnetic bearing 6a, but they are not shown in FIG. 1 for simplicity because they do not relate to the essence of the present invention.

The suction air 8 of the first stage compressor 1a is introduced from the outside atmosphere through a required device such as a suction filter (not shown). The air pressurized by the first stage compressor 1a is cooled by the intercooler 11a and then cooled by the second stage compressor 1b.
Will be introduced. The air further pressurized by the second stage compressor 1b is cooled by the aftercooler 11b,
2 and is supplied to each device on the downstream side of the compressor 1.

During normal load operation, the first stage compressor 1a
The pressure of the suction air at room temperature and atmospheric pressure is increased to about 3ata, and at this time, the outlet temperature of the impeller 4a rises to about 200 ° C.
In addition, the second stage compressor 1b is provided at about 40 downstream of the intercooler.
The temperature of the air cooled to 0 ° C. is increased to about 8 ata. At this time, the outlet temperature of the impeller 4b also increases to about 200 ° C.

The electric motor 2 for driving the compressor generates heat due to copper loss and iron loss of the electric motor stator 5 and the magnetic bearings 6 and 7 and wind loss around the rotating shaft 3 rotating at high speed. During normal load operation, the control valve 14 is closed. To cool this heat, cooling air 17 extracted from the downstream of the intercooler 11a is supplied to the electric motor stator and the magnetic bearing 6a on the first stage compressor side. Magnetic bearing 6b on the second stage compressor side
Is supplied with the cooling air 18 extracted from the downstream of the aftercooler 11b. The cooling air supplied to the motor 2 is
After cooling around the motor stator 5 and the magnetic bearings 6 and 7, the air is exhausted outside the machine.

In the first stage compressor 1a, a part of the dynamic pressure corresponding to the circumferential component of the flow of the compressed air is collected as static pressure by a diffuser (not shown) provided downstream of the impeller 4a. I have. Further, a swirling flow is generated at the back surface portion 20a of the impeller 4a with the rotation of the impeller, and the pressure is lower than the static pressure at the exit portion of the impeller. Thus, by setting the extraction unit downstream of the intercooler 11a, the cooling air 17 has a pressure higher than the static pressure of the impeller back part 20a even if the pressure loss of the intercooler 11a and the pipeline is included.

Similarly, in the second stage compressor 1b, the impeller 4
b A part of the dynamic pressure corresponding to the circumferential component of the flow of the compressed air is collected as a static pressure by a diffuser (not shown) provided downstream. Further, a swirling flow is generated at the back surface portion 20b of the impeller 4b with the rotation of the impeller, and the pressure is lower than the static pressure at the impeller outlet.
Thus, by setting the extraction unit downstream of the aftercooler 11b, the cooling air 18 has a pressure higher than the static pressure of the impeller rear surface 20b, even if the pressure loss of the aftercooler 11a and the pipeline is included.

The cooling air 17 is supplied to labyrinths 22a and 23
a is introduced into the space formed by a. At this time, the cooling air 17 flows through the labyrinth 23a to the magnetic bearing 6a due to the above-mentioned pressure relationship, is used for cooling the magnetic bearing, and also leaks to the impeller 4a side via the labyrinth 22a.

The cooling air 18 is supplied to the labyrinth 22b
And 23b. At this time, the cooling air 18 flows through the labyrinth 23b to the magnetic bearing 6b due to the above-mentioned pressure relationship, is used for cooling the magnetic bearing, and also leaks to the impeller 4b through the labyrinth 22b.

At this time, since the exhaust of the cooling air that has cooled the magnetic bearing is released to the atmosphere outside the machine, the differential pressure between the labyrinths 23a and 23b is sufficiently large, and the amount of cooling air for the magnetic bearing is secured. In addition, by appropriately selecting the gap between the labyrinths 23a and 23b and the number of teeth, it is possible to prevent the cooling of the magnetic bearing from consuming more air than necessary. On the other hand, since the pressure difference between the labyrinths 22a and 22b is relatively small, the flow rate of the compressed air leaking to the impeller side can be minimized by appropriately selecting the labyrinth gap and the number of teeth.

As described above, the magnetic bearing 6 on the first stage impeller side is used.
The compressed air 17 downstream of the intercooler 11a is
By introducing compressed air 18 downstream of the aftercooler 11b into the magnetic bearing 6b on the step impeller side, the magnetic bearing cooling air leaks to the impeller side, and high-temperature compressed air from the impellers 4a and 4b flows into the magnetic bearing portion. Leakage can be prevented. Therefore, the air amount of the cooling air can be suppressed to a minimum necessary for cooling the heat generation amount of the magnetic bearing portion,
Economics can be improved in a compressor that uses its own compressed air for cooling. In addition, there is no need for a discharge port for discharging the high-temperature compressed air leaking from the impeller to the outside of the machine, so that the economic efficiency can be improved.

On the other hand, when the compressor 1 is operating under no load, by opening the control valve 14, the aftercooler 11 is used as cooling air for the first-stage compressor-side magnetic bearing 6 a and the electric motor 2.
b. Cooling air 18 extracted from the compressed air downstream is introduced. In this case, too, the cooling air flows to the magnetic bearing side and leaks to the impeller side as in the case of the load operation described above because of the relationship between the pressure of the impeller rear portions 20a and 20b and the pressure of the cooling air 18. However, it is possible to prevent high-temperature compressed air from leaking from the impeller into the magnetic bearing portion.

In this embodiment and FIGS. 1 and 2, components not directly related to the present invention are not shown, but an air filter, a pressure gauge and the like may be appropriately provided.

As described above, according to the first embodiment of the present invention, the intercooler 1 is mounted on the magnetic bearing 6a on the first stage impeller side.
1a to the second stage impeller side magnetic bearing 6b
By introducing the compressed gas downstream of the aftercooler 11b, it is possible to prevent high-temperature compressed air from leaking from the impellers 4a and 4b, thereby improving the economy.

Next, a second embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention will be described with reference to FIGS. The second embodiment is a two-stage centrifugal air compressor in which a rotating shaft is supported by magnetic bearings, and FIG. 3 shows a schematic flowchart thereof. FIG. 4 shows a schematic structure near the first stage impeller and the first stage impeller side magnetic bearing of the first embodiment shown in FIG.

In the second embodiment, the structure of the compressor 1 is the same as that of the first embodiment, except for the arrangement of the labyrinths of the magnetic bearing cooling air 17 and 18 introduction portions.

As in the first embodiment, the motor stator 5 is used to cool the heat generated by the copper loss and iron loss of the motor stator 5 and the magnetic bearings 6 and 7 and the wind loss around the rotating shaft 3 rotating at high speed. The cooling air 17 extracted from the downstream of the intercooler 11a is supplied to the section and the magnetic bearing 6a on the first stage compressor side,
An aftercooler 11 is provided on the magnetic bearing 6b on the second stage compressor side.
b The cooling air 18 extracted from the downstream is supplied. The cooling air supplied to the electric motor 2 cools the periphery of the electric motor stator 5 and the magnetic bearings 6 and 7 and is then exhausted outside the machine.

In the second embodiment, a labyrinth 22a separates the impeller 4a from the magnetic bearing 6a, and a labyrinth 22b separates the impeller 4b from the magnetic bearing 6b. The magnetic bearing 6a and the motor stator 5 are separated by a labyrinth 24a, and the magnetic bearing 6b and the axial magnetic bearing 7 are separated by a labyrinth 24b. FIG. 4 shows the labyrinth 22a and the magnetic bearing 6a.
Although the auxiliary bearing 25a and the displacement sensor 26a are shown between them, they are not shown in FIG. 3 for simplicity because they do not relate to the essence of the present invention.

The space between the labyrinth 22a and the magnetic bearing 6a (the auxiliary bearing 25a in FIG. 4) is electrically connected to the outside via the supply port 27a. Similarly, the space between the labyrinth 22b and the magnetic bearing 6b is also electrically connected to the outside via the supply port.

Similarly to the first embodiment, the cooling air 17 and 18 are extracted from the downstream side of the intercooler 11a and the aftercooler 11b, respectively, so that the backside of the impeller is formed.
It has a pressure higher than the static pressure of 20a and 20b.

The cooling air 17 is introduced into a space between the labyrinth 22a and the magnetic bearing 6a (auxiliary bearing 25a). The introduced cooling air passes through the gap between the auxiliary bearing 25a and the displacement sensor 26a and the rotary shaft 3, and then cools the magnetic bearing 6a, passes through the labyrinth 24a, and cools the motor stator 5a.
Is discharged into the space containing Therefore, in the present embodiment, the cooling air 17 maintains a pressure close to the discharge pressure of the first stage compressor up to the magnetic bearing 6a, and after cooling the magnetic bearing, reduces the pressure to almost the atmospheric pressure when passing through the labyrinth 24a. Is done. The cooling air 17 flows into the magnetic bearing 6a to be used for cooling the magnetic bearing, and the labyrinth 22a
And leaks also to the impeller 4a side.

Similarly, the cooling air 18 is supplied to the labyrinth 22
b and the magnetic bearing side 6b. The introduced cooling air passes through the gap between the auxiliary bearing and the displacement sensor (not shown) and the rotating shaft 3, cools the magnetic bearing 6b, and is discharged to the space of the axial magnetic bearing 7 via the labyrinth 24b. . Therefore, in the present embodiment, the cooling air 18 maintains a pressure close to the discharge pressure of the first stage compressor up to the magnetic bearing 6b, and becomes almost atmospheric pressure when the magnetic bearing passes through the labyrinth 24b after cooling. The pressure is reduced.
The cooling air 18 flows into the magnetic bearing 6b to be used for cooling the magnetic bearing, and also leaks to the impeller 4b through the labyrinth 22b.

At this time, since the exhaust of the cooling air that has cooled the magnetic bearing is released to the outside of the machine, the differential pressure between the labyrinths 24a and 24b is sufficiently large, and the amount of cooling air for the magnetic bearing is secured. In addition, by appropriately selecting the gap between the labyrinths 24a and 24b and the number of teeth, it is possible to prevent unnecessary air consumption for cooling the magnetic bearing. On the other hand, since the pressure difference between the labyrinths 22a and 22b is relatively small, the flow rate of the compressed air leaking to the impeller side can be minimized by appropriately selecting the labyrinth gap and the number of teeth.

As described above, the magnetic bearing 6 on the first stage impeller side is used.
The compressed air 17 downstream of the intercooler 11a is
By introducing compressed air 18 downstream of the aftercooler 11b into the magnetic bearing 6b on the step impeller side, the magnetic bearing cooling air leaks to the impeller side, and high-temperature compressed air from the impellers 4a and 4b flows into the magnetic bearing portion. Leakage can be prevented. Therefore, the air amount of the cooling air can be suppressed to a minimum necessary for cooling the heat generation amount of the magnetic bearing portion,
Economics can be improved in a compressor that uses its own compressed air for cooling. In addition, there is no need for a discharge port for discharging the high-temperature compressed air leaking from the impeller to the outside of the machine, so that the economic efficiency can be improved.

[0039]

As is clear from the above detailed description, according to the centrifugal compressor equipped with a magnetic bearing according to the present invention,
A two-stage centrifugal compressor having an electric motor at a substantially central portion of a rotating shaft supported by a magnetic bearing, a first-stage impeller at one end of the rotating shaft, and a second-stage impeller at the other end. A magnetic bearing mounted centrifugal compressor that has an intercooler downstream of the first stage compression stage and an aftercooler downstream of the second stage compressor, and extracts a part of the compressed gas from downstream of these coolers and supplies it to the vicinity of the magnetic bearing. In this machine, the compressed gas downstream of the intercooler is introduced into the magnetic bearing on the first stage impeller side, and the compressed gas downstream of the aftercooler is introduced into the magnetic bearing on the second stage impeller. This has the effect of preventing gas from leaking, reducing the consumption of cooling air and improving economic efficiency.

Further, according to the centrifugal compressor mounted with a magnetic bearing according to the present invention, a motor is provided at a substantially central portion of a rotating shaft supported by the magnetic bearing, and a first-stage impeller is provided at one end of the rotating shaft. A two-stage centrifugal compressor having a second-stage impeller at an end, the magnetic bearing-mounted centrifugal compressor having a supply port for supplying a magnetic bearing cooling gas to a vicinity of the magnetic bearing, wherein a space between the supply port and a back surface of the impeller is provided. By separating the labyrinth with the labyrinth, and making the pressure of the magnetic bearing cooling gas introduced into the supply port higher than the gas pressure on the labyrinth impeller side, it prevents the high-temperature gas from leaking from the impeller to the magnetic bearing, This has the effect of reducing cooling air consumption and improving economics.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention.
It is a schematic structure figure of an example.

FIG. 2 shows a first embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention.
It is a partial structure figure of an example.

FIG. 3 shows a second embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention.
It is a schematic structure figure of an example.

FIG. 4 shows a second embodiment of a centrifugal compressor equipped with a magnetic bearing according to the present invention.
It is a partial structure figure of an example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 1a ... First stage compressor, 1b ... Second stage compressor, 2 ... Electric motor, 3 ... Rotating shaft, 4a, 4b ... Impeller, 5
... Motor stator, 6a, 6b ... Radial magnetic bearing, 7 ...
Axial magnetic bearings, 8: compressor suction air, 9: compressor discharge air, 11a: intercooler, 11b: aftercooler, 12: compressor discharge check valve, 13: blow-off valve, 14
... Control valve, 15 ... Check valve, 16 ... Blow-off passage, 17,
18: motor and magnetic bearing cooling air; 19: motor and magnetic bearing cooling air exhaust; 22a, 22b: labyrinth;
23a, 23b: labyrinth, 24a, 24b: labyrinth, 25a: auxiliary bearing, 26a: displacement sensor, 27a
... Cooling air supply port.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) (72) Inventor Hideo Nishida 603, Kandamachi, Tsuchiura-shi, Ibaraki Pref. Naohiko Takahashi 603, Kandamachi, Tsuchiura-shi, Ibaraki Pref. In the Tsuchiura Works of Hitachi Ltd.

Claims (1)

[Claims] 1. A two-stage centrifugal compressor having an electric motor substantially at the center of a rotating shaft supported by a magnetic bearing, a first-stage impeller at one end of the rotating shaft, and a second-stage impeller at the other end. Wherein an intercooler is provided downstream of the first stage compression stage and an aftercooler is provided downstream of the second stage compressor, and a portion of the compressed gas is extracted from downstream of these coolers and supplied to the vicinity of the magnetic bearing. In the centrifugal compressor equipped with a magnetic bearing, compressed gas downstream of the intercooler is introduced into the magnetic bearing on the first stage impeller side, and compressed gas downstream of the aftercooler is introduced into the magnetic bearing on the second stage impeller side. Centrifugal compressor with magnetic bearing.