EP2499376A1

EP2499376A1 - Gas compressor assembly

Info

Publication number: EP2499376A1
Application number: EP10779528A
Authority: EP
Inventors: Patrick Van Der Span
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG
Priority date: 2009-11-11
Filing date: 2010-11-10
Publication date: 2012-09-19
Also published as: WO2011058037A1; EP2322805A1; US20120251351A1; CN102725534A

Abstract

A gas compressor assembly (10) for compressing a gas (11) comprising a rotor (12) having a rotational axis (13), a motor section (15) and a compressor section (16) arranged along the rotational axis (13) of the rotor (12) and further comprising an inlet (20) to supply the gas (11) characterized in that the gas compressor assembly (10) further comprising a first motor passageway (22) to direct the gas (11) from the inlet (20) to the motor section (15) for cooling the motor section (15) and a compressor passageway (24) to direct the gas (11) from the motor section (15) to the compressor section (16). The inlet (20) is positioned adjacent to the side of the motor section (15) distant from the compressor section (16).

Description

Gas Compressor Assembly The present invention relates to a gas compressor assembly according to the preamble of claim 1; such a gas compressor is known from US Pat. No. 7,156,627 B2.

It is frequently necessary to compress a gas to a great extent, for example to store a large quantity of gas in a tank or the like, or to urge a significant quantity of gas through a pipeline or other industrial applications.

Generally motors are provided for driving the compression mechanism to compress the gas. Conventionally, the motor in such compression mechanism produces significant heat during operation. Providing adequate motor cooling, without

sacrificing energy efficiency of the compression system, continues to challenge designers of gas compression systems. US Pat. No. 7,156,627 B2 discloses a gas compressor assembly for such gas compression which usually comprises a rotor with an axis of rotation, a centrifugal compressor for compressing a gas, and an electric motor arranged on a common rotor shaft, a first bearing section and a second bearing section including bearings arranged in the vicinity of both ends of the rotor shaft to support the rotor. The gas compressor assembly herein includes an inlet positioned between the motor and the compressor to supply the gas to the compressor. The compressor compresses the gas and the compressed gas is passed through a filter to remove the impurities present in the gas and is then provided to the motor, the first bearing section and the second bearing section through separate passageways running from the compressor for cooling these sections. Disadvantageously, the temperature of the

compressed gas herein may be high which decreases the

capacity of the cooling gas to cool the motor and the bearing sections . It is an object of the invention to improve motor cooling efficiency of the gas compressor assemblies. This problem is solved by a gas compressor assembly according to claim 1.

The underlying idea of the invention is to increase the cooling of the motor section by supplying the gas directly to the motor section before getting compressed. The compression of the gas increases the pressure of the gas by expending energy leading to an increase in the temperature of the gas. Thus providing the uncompressed gas helps to improve the cooling of the motor section as the uncompressed gas has higher capacity to carry-over the heat away from the motor section .

According to a preferred embodiment, the inlet is positioned adjacent to the side of the motor section distant from the compressor section. This reduces the length of the motor passageway thereby making the design compact.

According to a preferred embodiment, the gas compressor assembly further includes a bearing section arranged along the rotational axis of the rotor at the side of the motor section distant from the compressor section, wherein the inlet is connected to the bearing section through a first bearing passageway to supply the gas for cooling the bearing section. This helps to provide a gas with relatively lesser temperature to the bearing such that the gas takes in more heat to provide increased cooling to the bearings, which in turn prevents the degradation of bearings due to extra heat.

According to a preferred embodiment, the bearing section includes a second bearing passageway to direct the gas from the bearing section to the motor section. This helps to provide additional gas flow to increase the rate of gas flowing through the motor section for cooling of the motor. According to a preferred embodiment herein, the inlet is arranged such that the main flow of the gas is directed to the motor section. The increased gas flow through the motor section helps to carry away a higher amount of heat, thereby improving cooling of the motor during compressor operation.

According to another preferred embodiment, the gas compressor assembly further comprising a second motor passageway to direct the gas to a motor gap between the rotor and a stator for cooling the motor section. The passageway provides for supplying the cooling gas to the space between the rotor and the stator so as to effectively cool the motor. According to a preferred embodiment, the first motor

passageway supplies the gas radially outside the stator for cooling the motor section. This helps to establish direct gas contact with the stator to transfer heat from the stator to ensure desired cooling of the motor section.

According to a preferred embodiment, the inlet is arranged so as to channel the gas to the compressor section through the motor section. This helps to cool the motor section before compression of the gas, thereby providing increased cooling of the motor and stator.

According to a preferred embodiment, all the gas supplied through the inlet is used for cooling the motor section. This provides for increased cooling of the motor section and eliminates the need for additional cooling devices such as fans, radiators or the like.

According to a preferred embodiment, the inlet is connected to a separation unit to separate at least one of a liquid and solid particle from the gas before providing for cooling.

This helps to prevent any damage of the motor or bearings due to the presence of corrosive particles. Also it increases the efficiency of the compressor as the gas supplied to the compressor section is substantially free of impurities.

According to another preferred embodiment, the separation unit comprises an annular chamber positioned

circumferentially around the axis of the rotor for the passage of the gas, wherein the gas is rotated inside the chamber such that at least one of the liquid and solid particles is separated from the gas. The annular chamber is simple in design with a big radius which yields high

centrifugal forces leading to a good separation of the impurities from the gas. Also, this does not require any auxiliary device for operation, which in turn provides for cleaning the gas in a cost-effective manner.

According to another preferred embodiment, the annular chamber includes an outer section and an inner section for the passage of the gas, wherein the outer section is

connected to receive the gas from the inlet to and the inner section is adapted to supply the purified gas to the motor section. This helps to separate the impurities from the gas at the outer section itself, thereby helps to supply the gas substantially free of impurities to the motor section, , which in turn prevents the damage of the motor and also increases its efficiency.

According to another preferred embodiment, the annular chamber further includes a barrier element positioned between the outer section and the inner section, wherein the barrier element deflects the liquid and solid particles from the outer section to the inner section. By this deflection liquid and other solid particles can be separated from the gas to be provided for cooling. According to yet another preferred embodiment, the separation unit further includes a drain line extending out of the compressor to expel the separated liquid and solid particle from the gas. This drain line isolates the separated particles and liquid from the assembly, thereby preventing the back-mixing of the particles with the gas.

According to yet another preferred embodiment, the separation unit is positioned on the inlet side in the compressor assembly between the inlet and the motor section. This provides a compact design and helps to reduce the length of the flow path of the gas. According to yet another preferred embodiment, the assembly further includes a gas-tight housing enclosing all the components of the assembly.

The present invention is further described hereinafter with reference to illustrated embodiments shown in the

accompanying drawings, in which:

FIG 1 shows a schematic overview in a cross-section of a gas compressor assembly according to an embodiment of the invention; and

FIG 2 illustrates a schematic top view of a separation unit according to an embodiment herein. Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

FIG 1 shows a schematic overview in a cross-section of a gas compressor assembly 10 according to an embodiment of the invention. The gas compressor assembly 10 comprises of a rotor 12 having an axis 13 of rotation, a bearing section 14, a motor section 15, and a compressor section 16. These sections are arranged in the order referred herein along the axis 13 of the rotor 12.

Here, the bearing section 14 is arranged along the rotational axis 13 of the rotor 12 at the side of the motor section 15 distant from the compressor section 16. The bearing section 14 includes a plurality of active magnetic bearings 18 for supporting the rotor 12. The assembly 10 herein further includes a common gas-tight housing 17 enclosing the rotor 12, the bearing section 14, the motor section 15, and the compressor section 16. The assembly 10 further includes another bearing section 38 enclosed with the gas tight housing 17. The bearing sections 14, 38 are generally disposed at the axial end sections of the rotor 12.

The gas compressor assembly 10 herein further includes an inlet 20 designed to provide an unregulated gas input to the assembly. The inlet 20 is positioned adjacent to the side of the motor section 15 distant from the compressor section 16. The gas 11 is drawn through the inlet 20 and is directed through various passages to cool the internal components of the gas compressor assembly 10 in a predetermined sequence to optimize the cooling efficiency and operating life of the assembly 10.

The inlet 20 through which the gas 11 enters the gas

compressor assembly 10 is placed adjacent to the bearing section 14 for providing the gas 11 to the different sections in the assembly 10. The inlet 20 can be an aperture formed on the compressor housing 17 or can be a line extending from external components to provide gas 11 to the compressor assembly 10.

The inlet 20 is connected to the motor section 15 through a first motor passageway 22 to provide the main flow of gas 11 to the motor section 15 for cooling the motor section 15. The gas 11 supplied through the first motor passageway 22 is directed radially outside a stator 19 in the motor section 15. The motor section 15 further includes a motor gap 26 that extends longitudinally between the stator 19 and the rotor 12. Here, the gas 11 from the inlet 20 is supplied to the motor gap 26 through a second motor passageway 23 radially extending from the first motor passageway 22 to cool the motor section 15 to an acceptable operation temperature. In addition, the inlet 20 herein is connected to the bearing section 14 through a bearing passageway 21 for guiding the gas 11 from the gas flow path to the bearing section 14. The gas 11 supplied to the bearing section 14 is directed through the bearing gaps 25 between the active magnetic bearings 18 for cooling the active magnetic bearings 18. The gas 11 from the bearing section 14 is further directed to the motor section 15.

The inlet 20 is arranged such that majority of the gas 11, for instance 60% to 90%, supplied through the inlet 20 is passed to the motor section 15 for cooling the motor section 15. The gas 11 is supplied directly to the motor section 15, before getting compressed at the compressor section 17. The heat carrying capacity of the uncompressed gas is more, which helps to effectively carry a substantial amount of heat from the motor section 15, thereby reducing the recycling flows. Here, the gas 11 supplied through the inlet 20 has a pressure sufficient enough to provide the required flow rate through the assembly 10.

As shown in the FIG.l, the gas compressor 10 includes a separation unit 27 placed at the inlet 20 side between the inlet 20 and motor section 15. The separation unit 27 removes the liquid or other solid particles present in the gas 11 before providing it for cooling. The inlet 20 is connected to an annular chamber 28 of the separation unit 27. The gas 11 to be filtered enters through the inlet 20 into the annular chamber 28 where it is rotated at a high speed around the axis 13 of the rotor 12. This provides for separating the liquid, solid particle or other impurities which may present in the gas 12 before supplying for cooling to the motor section 15 and bearing section 14. The separated liquid and solid particles are discharged from the annular chamber 28 by a drain line 29 extending out of the gas compressor assembly

10.

In the embodiment of FIG.l, the motor section 15 and the compressor section 16 are arranged in a fluid-connecting manner in the assembly 10. Thus the gas 11 from the motor section 15 is directed to the compressor section 16 through a compressor passageway 24 for compression. The compressor section 16 includes a compressor 30 which may be a compressor known in the art that is used for gas compression

applications, such as axial compressors, radial compressors, and the like. The compressor 30 is connected to a gas outlet 31, through which compressed gas 11 exits the gas compressor assembly 10.

For ease of installation and retrieval, the motor section 15 and the compressor section 16 can be accommodated in a single housing. Such an arrangement is particularly useful for subsea applications in which easy installation and retrieval are important.

The first and second motor passageways 23, 24 provide

sufficient space for the gas 11 to flow through such that the gas streaming through the motor section 15 is not

significantly restricted by the passageways 23, 24. That is the passageways are large enough to handle the stream of gas

11 without producing pressure build up on the inlet 20 side or a pressure drop on the side of the motor section providing gas to the compressor section 16. This provides the benefit of a continuous and relatively uniform supply of gas 11 to the compressor section 16 for compression. FIG 2 illustrates a schematic top view of a separation unit 27 according to an embodiment herein. The separation unit 27 herein is an accessorial unit which can be positioned in the assembly 10 to remove the liquid or solid particles from the incoming gas flow before the gas 11 is directed for cooling the motor section 15 or other internal components.

In the separation unit 27 of FIG.2, inlet 20 of the gas compressor 10 is connected to the separation unit 27 to provide the gas 11. The gas 11 from the inlet 20 is then fed to an annular chamber 28 in the separation unit 27. The gas 11 flowing through the chamber 28 may include traces of liquid, air or other type of gases containing dust or other particle impurities suspended therein with the impurities to be cleansed from the gas.

The annular chamber 29 herein is divided to an outer section 32 and an inner section 33. Here both sections 32, 33 are separated from each other by a barrier element 34 placed between the inner and outer sections 32, 33. The barrier element 34 herein is preferably in the shape of an annular ring. This geometry is aligned with the flow of gas and thereby reduces the pressure loss of the gas flow. Once the gas 11 is fed to the annular chamber 28, it is brought into rapid rotation in a direction along the

rotational axis of the rotor 12 in the outer section 32.

During this rotational movement, a large part of the liquid or other solid particles are flung out against the inner wall 35 of the annular chamber 28 owing to the centrifugal force where they gets collected and consequently drains out by gravity. The collected liquid or particles can be drained off via a drain line 29 without gas being mixed into an

appreciable extent. The gas 11 is rotated preferably at a rotational speed of 20,000 to 35,000 revolutions per minute. The gas 11 which is substantially free of the impurities is then passed on the inner section 33 to be circulated to the motor section 15. The separation unit 27 further includes bearing passageway 21 and motor passageways 22, 23 extending from the annular chamber 28 to supply the filtered gas 11 to the bearing section 14 and motor section 15 for cooling. The annular chamber 28 herein combines the function of separation of liquid or other solid particles and distribution of the gas to be compressed over the circumference of the rotation axis 10 in one compact component.

The separation unit 27 of FIG. 2 can be placed

circumferentially around the axis 13 of rotation of the rotor 12 and can be secured thereto by a securing means 36 such as nuts or the like. The separation unit 27 is simple in design with no moving parts to operate and is substantially easy to install in the gas compressor assembly 10. Also it requires no power to operate and starts working as soon as the gas to be treated is introduced. Moreover, it provides a minimum maintenance operation where the solid deposits can be removed by washing the annular chamber 28 with water or by running a liquid capable of dissolving the solid.

The dimensions of the annular chamber 28 determine the gas flow rate and the residence time required for the given separation process. The dimensions of the annular chamber 28 can be determined experimentally so that the higher

separation efficiency can be obtained.

The separation unit 27 design herein provides for preventing gas turbulence and back-mixing, which in turn prevents re^¬ entering of liquid or other particles and results in very high separation efficiencies for most industrial

applications. The separation unit 27 is suitable for use with additional pressurization, vacuuming, cooling condensation, etc with little or no design modifications.

In the embodiment herein, the inlet is arranged prior to the motor section. This helps to provide for filtering the gas before providing for cooling, thereby avoiding the need for separate scrubber and additional gas/fluid systems.

The gas compressor according to the invention finds extensive applications where higher pressure or lower volumes of gas is required. For instance, in pipeline transport of purified natural gas to move the gas from the production site to the consumer, in submarines, to store air for later use in displacing water from buoyancy chambers, for adjustment of depth, in petroleum refineries, natural gas processing plants, petrochemical and chemical plants, and similar large industrial plants for compressing intermediate and end product gases, in turbochargers and superchargers to increase the performance of internal combustion engines by increasing mass flow and the like.

Claims

Patent Claims

1. A gas compressor assembly (10) for compressing a gas (11) comprising a rotor (12) having a rotational axis (13), a motor section (15) and a compressor section (16) arranged along the rotational axis (13) of the rotor (12) and further comprising an inlet (20) to supply the gas (11),

characterized in that

the gas compressor assembly (10) further comprises:

- a first motor passageway (22) to direct the gas (11) from the inlet (20) to the motor section (15) for cooling the motor section (15); and

- a compressor passageway (24) to direct the gas (11) from the motor section (15) to the compressor section (16).

2. A gas compressor assembly (10) according to claim 1, characterized in that the inlet (20) is positioned adjacent to the side of the motor section (15) distant from the compressor section (16).

3. The gas compressor assembly (10) according to claim 1 or 2, characterized in that gas compressor assembly further includes a bearing section (14) arranged along the rotational axis (13) of the rotor (12) at the side of the motor section (15) distant from the compressor section (16), wherein the inlet (20) is connected to the bearing section (14) through a first bearing passageway (21) to supply the gas (11) for cooling the bearing section (14) .

4. The gas compressor assembly (10) according to claim 3, characterized in that the bearing section (14) includes a second bearing passageway (37) to direct the gas (11) from the bearing section (14) to the motor section (15) .

5. The gas compressor assembly (10) according to any of the claims 1 to 4, characterized in that the inlet (20) is arranged such that the main flow of the gas (11) is directed to the motor section (15) .

6. The gas compressor assembly (10) according to any of the claims 1 to 5, characterized in that all the gas (11) supplied through the inlet (20) is used for cooling the motor section (15) .

7. The gas compressor assembly (10) according to any of the claims 1 to 6, characterized in that the gas compressor assembly further comprising a second motor passageway (23) to supply the gas to a motor gap (26) between the rotor (12) and a stator (19) for cooling the motor section (15) .

8. The gas compressor assembly (10) according to any of the claims 1 to 7, characterized in that the first motor

passageway (22) provides the gas (11) radially outside of the stator (19) for cooling the stator (19) of the motor section (15) .

9. The gas compressor assembly (10) according to any of the claims 1 to 8, characterized in that the inlet (20) is connected to supply gas to a separation unit (27) adapted to separate at least one of a liquid and solid particle from the gas (11) before providing it for cooling.

10. The gas compressor assembly (10) according to claim 9, characterized in that the separation unit (27) comprises an annular chamber (28) positioned circumferentially around the axis (13) of the rotor (12), wherein the gas (11) is rotated inside the chamber (28) such that at least one of the liquid and solid particle is separated from the gas (11) .

11. The gas compressor assembly (10) according to claim 10, characterized in that the annular chamber (28) includes a outer section (32) and an inner section (33) for the passage of the gas (11), wherein the outer section (32) receives the gas (11) from the inlet (20) and the inner section (33) is adapted to supply the gas (11) received from the outer section (32) to the motor section (15) .

12. The gas compressor assembly (10) according to claim 10 or 11, characterized in that the annular chamber (28) further includes a barrier element (34) positioned between the outer section (32) and inner section (33), wherein the barrier element (34) deflects at least of the liquid and solid particles from the outer section (32) to the inner section (33) around the barrier element (34) .

13. The gas compressor assembly (10) according to any of the claims 9 to 12, characterized in that the separation unit (27) further includes a drain line (29) extending out of the compressor assembly (10) to expel the separated liquid and solid particle from the gas (11) .

14. The gas compressor assembly (10) according to any of the claims 9 to 13, characterized in that the separation unit (27) is positioned on the inlet (20) side between the inlet (20) and the motor section (15) in the compressor assembly (10) .

15. The gas compressor assembly (10) according to any of the claims 1 to 14, characterized in that the assembly (10) further comprising a gas-tight housing (17) to enclose the rotor (12), the bearing section (14), the motor section (15), and the compressor section (16).