JPH04246299A - Multistage compressor - Google Patents

Abstract

PURPOSE:To obviate the need of a step-up gear and reduce the dimension by reducing the number of couplings by supporting the rotor of each compressor by an electromagnetic bearing, and increasing the revolution speed of the rotor of a low pressure stage to the revolution speed of the rotor of a high pressure stage. CONSTITUTION:Each of high pressure stage compressor and low pressure stage compressor is constituted of a casing 5, rotor 6, multistage vane wheel 7, thrust collar 15, radial direction electromagnetic bearing 18, auxiliary bearing 23, and a sleeve 24. The bearing of a rotor is used as electromagnetic bearing, and the revolution speed is increased, and an impeller is made small-sized, and since the number of revolution of the low pressure stage is increased to the number of revolution of the high pressure stage, the need of a step-up gear is obviated, and the compression ratio is increased by increasing the number of impellers, and the number of couplings is reduced, and the reduction of dimension is achieved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage compressor, and more particularly to a multistage compressor suitable for downsizing.

0002

5 and 6, a conventional multi-stage compressor is, for example, a centrifugal carbon dioxide gas compressor (hereinafter referred to as a CO2 gas centrifugal compressor) that produces urea used as fertilizer by reacting ammonia and carbon dioxide. As shown in the figure, a single-shaft multi-stage centrifugal compressor is usually rarely used alone, and consists of a high-pressure stage compressor 1, 2 consisting of two casings 5, and a low-pressure stage consisting of one casing 5. Compressor 3
, speed increaser 4, couplings 11, 12, 13, 14
It is often used as a tandem type, directly connected through a . The high-pressure stage compressors 1, 2 and the low-pressure stage compressor 3 are each provided with a rotor 6 within a casing 5, and impellers 7 mounted on the rotor 6 in multiple stages. The rotor 6 of the low-pressure compressor 3 is connected to a drive machine 10 via a coupling 11. In addition, the low pressure stage compressor 3
The rotor 6 is connected to the speed increaser 4 via a coupling 12. The speed increaser 4 includes the high pressure stage compressor 1,
2 via a coupling, and the speed increaser 4 connects the rotor 6 of the high pressure stage compressor 1, 2 to the rotor 6 of the high pressure stage compressor 1, 2.
The rotational speed of the rotor 6 of the low-pressure compressor 3 is set higher than that of the rotor 6 of the low-pressure compressor 3. Further, the rotor 6 of the high-pressure stage compressor 3 is connected via a coupling 14. Further, the rotors 6 of the high-pressure compressors 1 and 2 and the rotor 6 of the low-pressure compressor 3 are rotatably supported by a radial bearing 8 and a thrust bearing 9, respectively. The radial bearings 8 are installed at both ends of each rotor 6. The thrust bearings 9 are installed at one end of each rotor 6 on both sides of the radial bearing 8, sandwiching the radial bearing 8 therebetween. The radial bearing 8 and the thrust bearing 9 are both tilting type bearings.

[0003] Regarding this type of multi-stage compressor, for example, ``Hitachi Hyoron, V
oL. 60, NO. 3, P183 to P188).

0004

The above-mentioned conventional CO2 gas compressor for urea synthesis is used to increase the pressure from atmospheric pressure to 150 to 250 atmospheres, which is the reaction pressure. In the case of the configuration shown in FIG. 5, the low-pressure stage compressor 3 compresses from atmospheric pressure to approximately 25 atm, one high-pressure stage compressor 1 compresses from 25 atm to 100 atm, and then the other high-pressure stage compressor 1 compresses from 25 atm to 100 atm. A compressor compresses from 100 atm to a final pressure of 250 atm.

[0005] When trying to downsize the structure and reduce the occupied volume of the CO2 gas compressor for urea synthesis, it goes without saying that the rotational speed of the rotor 6 of each compressor 1, 2, and 3 should be increased. It is possible to increase the speed. For example, by increasing the rotational speed of the rotor 6 of the low-pressure stage compressor 3 to be the same as the rotational speed of the rotor 6 of the high-pressure stage compressors 1 and 2, the speed increaser 4 and the coupling 12 are no longer necessary. The structure of the low-pressure stage compressor 3 can be downsized. Furthermore, by increasing the number of impellers 7 attached to each rotor 6 and increasing the number of compressors per casing 5, the high-pressure stage compressor 2 and the coupling 14 become unnecessary.

However, by increasing the rotational speed of the rotor 6, the bearings 8 and 9 that support the rotor 6 can pass through the natural frequency of the rotor 6, which occurs until the target rotational speed is reached. Sufficient stiffness and damping capacity are required. On the other hand, tilting pad type bearings 8 and 9, which are often used in conventional multi-stage compressors, do not have enough bearing capacity to pass through the third critical speed (first bending mode) of the rotor 6. However, there was a limit to the speed increase of conventional multi-stage compressors, which was limited to below the tertiary critical speed. Furthermore, when designing the rotor 6 at a speed below the tertiary critical speed, the number of impellers 7 that can be attached to the rotor 6 is also limited. As a result, in the conventional technology, not only cannot the low-pressure stage compressor 3 be made high-speed and compact, but also the casing mechanism of the high-pressure stage compressors 1, 2, the speed increaser 4, the couplings 12, 13, There was a problem that it was not possible to reduce 14.

A first object of the present invention is to provide a multistage compressor that can stably pass through the tertiary critical speed of the rotor.

A second object of the present invention is to eliminate the speed increaser,
It is an object of the present invention to provide a multistage compressor that can reduce the number of couplings and downsize the entire configuration.

A third object of the present invention is to provide a multi-stage compressor that can reduce the number of casings in the high-pressure stage compressor and downsize the entire configuration.

A fourth object of the present invention is to provide a multi-stage compression system that can prevent the rotor from falling onto the electromagnet of the electromagnetic bearing and damaging the outer surface of the rotor and the multi-stage compressor even if the electromagnetic bearing is demagnetized. The aim is to provide the opportunity.

[0011] Examples of materials related to this type of electromagnetic bearing include the JMB Company Catalog (Active Magnetic Bearings: Application to Industrial Rotating Machines) and the JMB Company Symposium Materials (Active Magnetic Bearings).

0012

[Means for Solving the Problems] In order to achieve the first object, the first invention includes a drive machine, a low pressure stage compressor,
A multi-stage compressor comprising a speed increaser that adjusts the rotational speed of a rotor of the low-pressure compressor and a high-pressure compressor,
The bearings that support the rotors of each of the compressors mentioned above are constituted by electromagnetic bearings.

In order to achieve the second object, the second invention includes a drive machine, a low-pressure stage compressor, a speed increaser for adjusting the rotational speed of a rotor of the low-pressure stage compressor, and a high-pressure stage compressor. In a multi-stage compressor comprising a compressor, a coupling connecting the high-pressure stage compressor, the speed increaser, and the low-pressure stage compressor, a bearing supporting the rotor of each compressor is provided with an electromagnetic bearing. The rotational speed of the rotor of the high-pressure compressor is increased by increasing the rotational speed of the low-pressure compressor.

In order to achieve the third object, the third invention includes a drive machine, a low-pressure compressor having one casing, and a speed increaser for adjusting the rotational speed of the rotor of the low-pressure compressor. a high pressure stage compressor having a plurality of casings;
A multi-stage compressor comprising the high-pressure stage compressor, the speed increaser, and a coupling connecting the low-pressure stage compressor, wherein the bearings supporting the rotors of each of the compressors are constituted by electromagnetic bearings, and The number of impellers installed in each of the casings is increased to increase the compression ratio.

[0015] In order to more reliably achieve the first to third objects, a fourth invention provides a fourth invention, in which at least two electromagnetic bearings are arranged around the rotor, and the rotor is levitated by magnetic force so as to be non-contact. an electromagnet that is moved by the rotor, a displacement sensor that is arranged around the rotor and detects the amount of displacement of the rotor with respect to the electromagnet, and a control means that controls the current to the electromagnet based on the detection result of the displacement sensor. It is constructed.

[0016] In order to achieve the fourth object, a fifth invention is such that the electromagnetic bearing is provided with an auxiliary bearing having a gap smaller than the gap between the electromagnetic bearing and the rotor.

[0017]

[Operation] The first invention is a multi-stage compressor in which the bearings that support the rotors of each compressor are constituted by electromagnetic bearings. Unlike conventional tailing pad bearings, electromagnetic bearings essentially do not require lubricating oil, and use the magnetic force of electromagnets to levitate the rotor and support the rotor in a non-contact movable manner. Therefore, the rotor can be held in as accurate a position as possible, and a high bearing damping force can be obtained at the rotor's third critical speed. As a result, the rotational speed of the rotor of each compressor can be increased, and the shape of the impeller attached to the rotor can be made smaller, so that the entire multistage compressor can be made smaller.

[0018] In a second invention, since the rotational speed of the rotor of each compressor can be increased according to the first invention, the rotational speed of the rotor of the low-pressure stage compressor is increased to the rotational speed of the rotor of the high-pressure stage compressor. It is something. Therefore, it is possible to eliminate the need for a speed increaser and reduce the number of couplings.
Thereby, the axial length of the entire multistage compressor can be further reduced.

[0019] The third invention is that the shape of the impeller attached to the rotor of the high-pressure stage compressor can be reduced in size according to the first invention, and the supporting weight of the rotor can thereby be reduced. The number of impellers installed in one casing is increased to increase the compression ratio. therefore,
The number of casings and couplings of the high-pressure stage compressor can be reduced, which allows the overall multi-stage compressor to be further miniaturized.

[0020] In a fourth aspect of the invention, the amount of displacement of the rotor with respect to the electromagnet is detected by a displacement sensor, and the current to the electromagnet is controlled by a control means based on the detection result. Therefore, the rigidity of the bearing and the high bearing damping force at the tertiary critical speed of the rotor can be further improved.

In a fifth aspect of the invention, the electromagnetic bearing is provided with an auxiliary bearing having a gap smaller than the gap between the electromagnetic bearing and the rotor. Therefore, it is possible to prevent damage to the outer surface of the rotor and each compressor caused by the rotor falling onto the electromagnetic bearing by itself due to failure of the electromagnetic bearing or interruption of current supply.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Below, drawings showing embodiments of the present invention will be described.

1 and 2 are conceptual diagrams showing one embodiment of the present invention, FIG. 3 is an enlarged longitudinal cross-sectional view of a single-shaft multistage centrifugal compressor used in the embodiment shown in FIG. 1, and FIG. 3 is a schematic diagram of an electromagnetic bearing used in the embodiment shown in FIG. 2. FIG.

In the fluid machine of the embodiment shown in FIG. 1, a high-pressure stage compressor 1, a low-pressure stage compressor 3, and a drive unit 10 are connected in series via couplings 11 and 12. Furthermore, if a double-shaft drive machine 22 is used as shown in FIG. You can also do that.

[0025] The high pressure stage compressor 1 and the low pressure stage compressor 3
As shown in FIG. 3, the rotor 6 includes a casing 5, a rotor 6, an impeller 7 mounted on the rotor 6 in more stages than the conventional machine shown in FIG. It includes an electromagnetic bearing 17 that supports the rotor 6 in the thrust direction, an electromagnetic bearing 18 that supports the thrust direction of the rotor 6, an auxiliary bearing 23, and a sleeve 24.

The rotor 6 and drive unit 1 of the low-pressure stage compressor 3
0 are connected to each other by a coupling 11.

The rotor 6 of the low-pressure compressor 3 and the rotor 6 of the high-pressure compressor 1 are connected to each other by a coupling 12.

The double-shaft drive machine 22 and the rotor 6 of the low-pressure stage compressor 3 are connected to each other by a coupling 11.

The double-shaft drive machine 22 and the rotor 6 of the high-pressure stage compressor 1 are connected to each other by a coupling 12.

[0030] The high pressure stage compressor 1 and the low pressure stage compressor 3
The rotors 6 are each supported by an electromagnetic radial bearing 17 or an auxiliary bearing 23 when the electromagnetic bearing is demagnetized. This electromagnetic radial bearing 17 and the auxiliary bearing 2
3 are provided at both ends of the rotor 6.

[0031] The high pressure stage compressor 1 and the low pressure stage compressor 3
A thrust collar 15 is attached to one end of the rotor 6, and an electromagnetic thrust bearing 18 is attached to the rotor 6.
are provided on both sides of the thrust collar 15.

Sleeves made of silicon steel plates laminated in the axial direction of the rotor 6 are provided on both ends of the rotor 6 on the outer periphery of the rotor 6 at the position where the electromagnetic radial bearing is installed. ing.

As schematically shown in FIG. 3, the electromagnetic bearings 17 and 18 are composed of electromagnets 20 having coils 20a. The coil 20a is connected to the control means 19, and uses direct current as a power source.

A position sensor 21 is arranged near each of the electromagnetic bearings 17 and 18. This position sensor 21 is connected to the control means 19, and the control means 19 controls the radial direction of the rotor 6 detected by the position sensor 21,
Alternatively, each electromagnetic bearing 17, 1 may be displaced in the thrust direction.
8 electromagnets 20 are PID-controlled.

As shown in FIG. 3, the auxiliary bearing 23 is provided near the electromagnetic bearing 17, which is a radial bearing. Each auxiliary bearing 23 is configured to receive the rotor 6 when the electromagnet 20 of the electromagnetic bearings 17 and 18 is demagnetized and the rotor 6 falls due to its own weight.

[0036] In the fluid machine of this practical example, the drive machine 10,
Alternatively, the couplings 11 and 12 can be
By rotating the rotor 6, the high pressure stage compressor 1
and drives the low pressure stage compressor 3.

When the rotor 6 rotates, the electromagnetic bearing 17,
18, the rotor 6 is not lubricated by the attraction force of the electromagnet 20;
Float and support without contact. These electromagnetic bearings 17, 18
While supporting the rotor 6, the position sensor 21 detects displacement of the rotor 6 in the radial and thrust directions, and sends the detection results to the control means 19, which controls the current supplied to the coil 20a of the electromagnet 20. P based on the amount of displacement of the rotor 6 in the radial direction and the thrust direction.
The rotor 6 is stably supported by ID control.

In the PID control in the control means 19, the tertiary critical speed of the rotor 6 is adjusted so that it can pass stably. This allows the rotor 6 to increase its rotational speed to a frequency range higher than the tertiary critical speed.
The outer diameter and inner diameter of the impeller 7 can be made smaller than the conventional machines shown in FIGS. 5 and 6, and by making the outer diameter and inner diameter of the impeller 7 smaller, the weight applied to the rotor 6 is reduced. As a result, as shown in FIG. 3, the number of impellers 7 can be increased, and as shown in FIG.
, the couplings 13 and 14 can be made unnecessary.

Further, in this embodiment, electromagnetic bearings 17 and 18 are used as bearings for the rotor 6. therefore,
When the electromagnets 20 of the electromagnetic bearings 17 and 18 are demagnetized, the rotor 6 falls under its own weight. At this time, in this embodiment, the rotor 6 is received near each electromagnetic bearing 17 by an auxiliary bearing 23 having a gap smaller than the gap between the electromagnetic bearings 17, 18 and the rotor 6. As a result, the outer surface of the rotor 6 itself due to the fall of the rotor 6, the high pressure stage compressor 1
Also, damage to the low pressure stage compressor 3 can be prevented.

[0040]

[Effects of the Invention] According to the first invention, in a multi-stage compressor, the bearings that support the rotor of each compressor are constituted by electromagnetic bearings, so that the rotor can be held in as accurate a position as possible, and A high bearing damping force can be obtained above the tertiary critical speed of the rotor, and as a result, the rotational speed of the rotor of each compressor can be increased. Therefore, since the shape of the impeller attached to the rotor can be made smaller, the entire multistage compressor can be made smaller.

According to the second invention, in the multi-stage compressor, the bearing supporting the rotor of each compressor is constituted by an electromagnetic bearing, and the rotational speed of the rotor of the low-pressure stage compressor is controlled by the rotor of the high-pressure stage compressor. Since the rotation speed has been increased, a speed increaser is no longer required.
In addition, the number of couplings can be reduced, thereby making it possible to further reduce the axial length of the entire multistage compressor.

According to the third invention, in the multi-stage compressor, the bearings that support the rotor of each compressor are constituted by electromagnetic bearings, and the number of impellers installed in one casing of the high-pressure stage compressor is As the compression ratio is increased, the number of casings and couplings of the high-pressure stage compressor can be reduced, thereby making it possible to further downsize the entire multi-stage compressor.

According to the fourth invention, at least two electromagnetic bearings are arranged around the rotor, and include an electromagnet that levitates the rotor using magnetic force and moves it without contact; It is composed of a displacement sensor that detects the amount of displacement of the rotor with respect to the electromagnet, and a control means that controls the current to the electromagnet based on the detection result of the external displacement sensor. Bearing damping force at critical speeds can be further improved.

According to the fifth invention, since the electromagnetic bearing is provided with an auxiliary bearing having a gap smaller than the gap between the electromagnetic bearing and the rotor, there is no possibility that the electromagnetic bearing will malfunction or the current supply will stop. This prevents the rotor from falling onto the electromagnetic bearing by itself and damaging the outer surface of the rotor and each compressor.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing one embodiment of the present invention.

FIG. 2 is a conceptual diagram showing one embodiment of the present invention.

FIG. 3 is an enlarged longitudinal sectional view of the single-shaft multistage centrifugal compressor used in the embodiment shown in FIG. 1.

FIG. 4 is a schematic diagram of an electromagnetic bearing used in the embodiment shown in FIGS. 1 and 3.

FIG. 5 is a conceptual diagram showing a prior art.

FIG. 6 is an enlarged vertical cross-sectional view showing a conventional single-shaft multistage centrifugal compressor used in FIG. 5;

[Explanation of symbols]

1 High pressure stage compressor 2 High pressure stage compressor 3. Low pressure stage compressor 4 Speed increaser 5 Casing 6 Rotor 7 Impeller 8 Radial bearing 9 Thrust bearing 10 Drive machine 11 Coupling 12 Coupling 13 Coupling 14 Coupling 15 Thrust collar 17 Electromagnetic radial bearing 18 Electromagnetic thrust bearing 19 Control means 20 Electromagnet 20a coil 21 Position sensor 22 Double shaft drive machine 23 Auxiliary bearing

Claims (5)

[Claims] Claim 1. A multi-stage compressor comprising a drive machine, a low-pressure stage compressor, a speed increaser for adjusting the rotational speed of a rotor of the low-pressure stage compressor, and a high-pressure stage compressor, in which each compression A multi-stage compressor characterized in that the bearing that supports the rotor of the machine is composed of an electromagnetic bearing. 2. A drive machine, a low-pressure compressor, a speed increaser for adjusting the rotational speed of a rotor of the low-pressure compressor, a high-pressure compressor, the high-pressure compressor, the speed increaser, and In a multi-stage compressor comprising the above-mentioned low-pressure stage compressor and a connecting coupling, the bearing supporting the rotor of each of the above-mentioned compressors is constituted by an electromagnetic bearing, and the rotational speed of the rotor of the above-mentioned low-pressure stage compressor is controlled as above. A multi-stage compressor characterized by increasing the rotational speed to the rotor speed of a high-pressure stage compressor. 3. A drive machine, a low-pressure compressor having one casing, a speed increaser for adjusting the rotation speed of a rotor of the low-pressure compressor, a high-pressure compressor having a plurality of casings, and a high-pressure compressor having a plurality of casings. A multi-stage compressor comprising a high-pressure compressor, a speed increaser, and a coupling connecting the low-pressure compressor, wherein a bearing supporting a rotor of each compressor is an electromagnetic bearing; A multi-stage compressor characterized by increasing the number of impellers installed in each casing to increase the compression ratio. 4. At least two of the electromagnetic bearings are arranged around the rotor, and include an electromagnet that levitates the rotor using magnetic force and moves it without contact; The multi-stage compressor according to claim 1, 2 or 3, characterized in that it is comprised of a displacement sensor that detects the amount of displacement, and a control means that controls the current to the electromagnet based on the detection result of the displacement sensor. . 5. The electromagnetic bearing includes an auxiliary bearing having a gap smaller than a gap between the electromagnetic bearing and the rotor.
Or the multistage compressor described in 3.