CN118328022A - Low-temperature oil-free centrifugal compressor placed in heat insulation environment - Google Patents

Abstract

The invention discloses a low-temperature oil-free centrifugal compressor placed in an adiabatic environment, which comprises an adiabatic cold box, a centrifugal compressor set, a connecting pipeline and a vacuum pump. The centrifugal compressor is arranged in the heat-insulating cold box and comprises a motor, an impeller, a volute and a bearing; the impellers at two ends of the centrifugal compressor and the motor are arranged in different chambers of the heat-insulating cold box; the centrifugal compressor can adopt a rotor structure with the same two ends; the motor does not need to be cooled; the centrifugal compressor is provided with a motor heat-insulation loop; the bearing adopts a gas bearing or a gas-magnetic hybrid bearing, and the gas bearing is in the form of full dynamic pressure, dynamic static pressure or full static pressure. The low-temperature oil-free centrifugal compressor placed in the adiabatic environment can greatly reduce the power consumption and the cold leakage loss of the compressor; the compressors with the same structures at the two sides do not need to consider axial force; by arranging different heat insulation chambers, heat preservation loops and other measures, the compressor can be operated at the inlet temperature of minus 268 to minus 20 ℃; the low-temperature centrifugal compressor runs in a pure oil-free mode, and the volume and the weight of the system are greatly reduced.

Description

Low-temperature oil-free centrifugal compressor placed in heat insulation environment

Technical Field

The invention relates to the technical field of centrifugal compressors for the low-temperature field, in particular to a low-temperature oil-free centrifugal compressor placed in an adiabatic environment.

Background

Centrifugal compressors play a critical role in the field of gas liquefaction of helium, air, nitrogen, neon, hydrogen, and the like, which typically involves cooling the gas to a very low temperature to convert it from a gaseous state to a liquid state. In the gas liquefaction process, the centrifugal compressor compresses working gas to high pressure to provide necessary pressure and energy for refrigeration circulation, and the high pressure gas releases heat in the expansion process, so that cooling is realized. The centrifugal compressor has higher energy efficiency ratio, can provide larger flow and higher pressure, is beneficial to reducing the energy consumption in the working gas liquefaction process, improves the overall energy efficiency, and meets the requirement of mass production.

The conventional compressor needs to heat the gas to normal temperature and then compress the gas, the compressed gas is subjected to cooling expansion after oil removal and filtration, and the system needs to be provided with devices such as a temperature emptier, a heat regenerator and the like, so that the system cost and the occupied area are greatly increased, and meanwhile, the process of cooling after the prior temperature rise extremely causes larger energy loss.

Meanwhile, the conventional compressor cannot work at a lower environment temperature due to the adoption of the oil bearing support, and the compressor has higher power consumption when working in a normal-temperature environment. Since the compression work of a compressor has a very close relationship with the inlet temperature of its working medium, an effective way to reduce the power consumption of a compressor is to reduce the inlet temperature of the compressor. When the centrifugal compressor operates in an extremely low temperature environment, the inlet temperature of the centrifugal compressor is extremely low, the centrifugal compressor is required to reduce heat exchange with the outside, and meanwhile, the motor of the compressor is required to normally operate, so that high requirements are provided for the structure and the rotor supporting mode of the compressor.

Disclosure of Invention

In order to solve the technical problem, the invention provides the low-temperature oil-free centrifugal compressor in an adiabatic environment, which can operate at an inlet temperature of-268 ℃, and the existence of an adiabatic cold box and a plurality of chambers arranged in the cold box greatly reduces the cold leakage of the compressor, and simultaneously, the compressors in a plurality of different structural forms meet different use requirements of industrial production.

In order to achieve the above object, the present invention provides a low temperature oil-free centrifugal compressor placed in an adiabatic environment, comprising:

the centrifugal compressor unit is arranged in the heat-insulating cold box and can operate within the inlet temperature range of-268 ℃ to-20 ℃;

a plurality of chambers are arranged in the heat-insulating cold box;

the centrifugal compressor comprises a motor, an impeller, a volute and an air bearing;

When the centrifugal compressors with the same structures at two sides are adopted, the same impellers are adopted at two ends of the centrifugal compressor, the motor rotors are identical in structure and symmetrically distributed, axial force is not required to be considered, at the moment, the compressor can be not only provided with a thrust disc, the structure is simpler, at the moment, the thrust surface is a vertical surface perpendicular to the main shaft on the main shaft of the rotor or an inclined surface forming a certain included angle with the main shaft of the rotor, when the inclined surface is adopted as the thrust surface, the area of the thrust surface can be increased on the premise of not increasing the outer diameter of the main shaft of the rotor, and the rotor runs more stably;

When the centrifugal compressor motor operates under a low-temperature working condition, motor cooling does not need to be considered, the motor comprises a motor stator, a rotor and an end cover, an air inlet and an air outlet are formed in a motor shell, and the motor rotor is supported by adopting an air bearing;

the impellers at two ends of the centrifugal compressor and the middle motor are positioned in different chambers of the heat-insulating cold box;

The centrifugal compressor volute is divided into a first-stage volute and a second-stage volute, a gas circuit is additionally arranged at the second-stage volute, the gas circuit is communicated with the inside of the centrifugal compressor motor to form a motor heat insulation loop, a temperature sensor is arranged on the heat insulation loop, the temperature of the motor can be judged, and the direction and the gas quantity of the gas circuit are controlled through an electric opening regulating valve.

The centrifugal compressor is supported by adopting a gas bearing, working medium self-lubrication is adopted, the gas bearing is divided into a radial bearing and a thrust bearing, and the bearing type can be full dynamic pressure type, dynamic and static pressure type combined type or full static pressure type;

furthermore, the low-temperature centrifugal compressor can be operated at an inlet temperature of-268 ℃, so that the power consumption of the compressor is greatly reduced, and the working gas can be helium, air, nitrogen, neon or hydrogen.

Further, since the variable compression work of the compressor is proportional to the intake air temperature, the expression is as follows,

Wherein W is multi-table compression work, m is a polytropic exponent, R is a constant, the inlet air temperature and p ₂/p₁ is the compressor pressure ratio; when the centrifugal compressor is operated at the extremely low inlet temperature, partial cold energy is needed to maintain a low-temperature environment, and when the inlet temperature of the compressor is-200 ℃ under the condition of unchanged compression ratio, the compression work of the compressor is about 25% of the inlet temperature of 20 ℃, so that the power consumption of the compressor is greatly reduced, and the energy of a system is saved.

Further, when the same structure is adopted on both sides of the centrifugal compressor, the compressor can be supported by the radial bearing only or the radial bearing plus the thrust bearing, and when the thrust bearing is set up, the thrust bearing is parallel to the thrust surface.

Further, the impellers and the middle motor at two ends of different chambers of the heat-insulating cold box can be in the same vacuum degree environment, or in environments with different vacuum degrees, or in environments wrapped by heat-insulating materials or pearly-lustre sand.

Further, the motor cooling is not needed to be considered when the low-temperature centrifugal compressor runs at low temperature, the temperature of the motor is monitored through a temperature sensor arranged on the heat preservation loop, when the temperature of the motor is lower, the motor of the first-stage compressor and the motor of the second-stage compressor are heated through the electric opening regulating valve by using higher-temperature gas at the outlet of the second-stage volute, and the normal running of the motor is ensured. If the gas at the outlet of the second-stage volute cannot completely meet the heat preservation function of the motor, the auxiliary heat preservation work is carried out on the motor shell through the gas storage tank additionally arranged, so that the normal work of the motor is ensured.

Furthermore, the centrifugal compressor unit can be 1-12 stages, and interstage cooling can be further arranged between the compressors of each stage.

Furthermore, the centrifugal compressor unit can adopt 1-8 centrifugal compressors with the same structure at two sides to be connected in parallel or 1-8 multistage centrifugal compressors to be connected in series.

Further, the gas bearing is divided into a radial bearing and a thrust bearing, wherein the radial bearing can adopt a dynamic pressure type or a static pressure type, and the thrust bearing can also adopt a dynamic pressure type or a static pressure type.

Furthermore, the connecting pipe has elasticity, avoids expending with heat and contracting with cold to produce the influence of stress.

Furthermore, the end part of the motor is provided with a heat insulation plate, the heat insulation plate is made of polytetrafluoroethylene or epoxy resin, a terminal of the compressor is led out from a stator of the motor, and the heat insulation cold box is led out through a heat insulation cavity where the shell of the compressor and the motor are positioned.

Compared with the prior art, the invention has the following advantages and technical effects:

The low-temperature centrifugal compressor is arranged in the heat-insulating cold box, and meanwhile, impellers and motors at two ends are arranged in different chambers in the heat-insulating cold box, so that the power consumption of the centrifugal compressor and the cold leakage during operation under a low-temperature working condition can be reduced. When the centrifugal compressor structure with the same two end structures is adopted, the influence of axial force can be eliminated; when a single two-stage centrifugal compressor is adopted, the system structure is more compact; when a structure in which a plurality of two-stage compressors are connected in series is adopted, a higher compression ratio can be obtained. Through the setting of adiabatic cold box and heat preservation return circuit, can realize the monitoring of motor temperature and the tolerance regulation of heat preservation return circuit, realize the motor heat preservation function of low temperature operating mode operation, guarantee the normal operating of motor. Through the setting of the inside different cavities of adiabatic cold box, can have multiple different adiabatic modes to can avoid the vacuum extraction of big volume, reduce the energy consumption. The combined vacuum pump structure of the mechanical pump and the molecular pump can obtain higher vacuum degree and further reduce cold leakage. By adopting the air bearing support, the whole system can run in a pure oil-free mode, friction loss is reduced, and service life is prolonged.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

FIG. 1 is a schematic diagram of a parallel connection of two centrifugal compressors with the same structure on both sides;

FIG. 2 is a schematic view of a configuration employing a single two-stage centrifugal compressor;

FIG. 3 is a schematic diagram of a configuration employing two-stage centrifugal compressors in series;

FIG. 4 is a schematic view of a configuration employing a single stage centrifugal compressor;

FIG. 5 is a schematic view of a rotor structure and bearing arrangement of a centrifugal compressor having the same structure on both sides;

FIG. 6 is a schematic view of a rotor structure and bearing arrangement of a centrifugal compressor having the same side structure;

FIG. 7 is a schematic view of a rotor structure and bearing arrangement of a centrifugal compressor having the same side structure;

FIG. 8 is a schematic view of a rotor structure and bearing arrangement of a centrifugal compressor having the same side structure;

FIG. 9 is a schematic diagram of a two-stage centrifugal compressor rotor structure and bearing arrangement;

Wherein 1-adiabatic cold box, 11-first adiabatic chamber, 12-second adiabatic chamber, 13-third adiabatic chamber, 14-fourth adiabatic chamber, 15-fifth adiabatic chamber, 16-sixth adiabatic chamber, 2-primary centrifugal compressor, 211-primary compressor stator, 212-primary compressor rotor, 213-primary compressor cover plate, 214-motor housing insulation material, 22-primary compressor impeller, 231-primary compressor radial bearing, 232-primary compressor thrust bearing, 233-primary compressor thrust disk, 24-primary compressor volute, 25-primary compressor terminal, 3-secondary compressor, 311-secondary compressor stator, the device comprises a 34-secondary compressor volute, a 341-secondary compressor volute opening, a 35-secondary compressor terminal, a 4-vacuum pump, a 41-mechanical pump, a 42-molecular pump, a 51-55-gas storage tank, a 6-secondary compressor 1, a 611-secondary compressor stator, a 612-secondary compressor rotor, a 621-secondary compressor primary impeller, a 622-secondary compressor secondary impeller, a 631-secondary compressor radial bearing, a 632-secondary compressor thrust bearing, a 641-secondary compressor primary volute, a 642-secondary compressor secondary volute, a 65-secondary compressor terminal, a 7-secondary compressor 2, an 8-secondary compressor 3, a 91-temperature sensor and a 92-electric opening regulating valve.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.

Example 1:

fig. 1 is a schematic diagram of a parallel connection structure of two first-stage centrifugal compressors 2 and two second-stage centrifugal compressors 3 with the same structure at two sides, and according to the structure shown in fig. 1, the assembly and welding of the first-stage centrifugal compressors 2 and the second-stage centrifugal compressors 3 are completed, and then the two centrifugal compressors are placed in an adiabatic cold box 1 in a parallel connection mode. Wherein the impellers at two ends of the primary compressor 2 are positioned in the first heat insulation chamber 11, the motor of the primary compressor 2 is positioned in the second heat insulation chamber 12, and during the working process of the compressor, when the inlet temperature of the compressor is extremely low, the heat insulation of the impellers at two ends and the motor can be realized by a method of extracting different vacuum degrees from the first heat insulation chamber 11 and the second heat insulation chamber 12, and the vacuum degree of the second heat insulation chamber 12 can be lower than that of the first heat insulation chamber 11 because the temperature of the working environment of the impellers is lower, but the temperature of the motor is not lower. When the inlet temperature of the centrifugal compressor is not extremely low, the vacuum extraction of each heat-insulating chamber is not needed, and the impellers and the motors at the two ends can be in an environment wrapped by heat-insulating materials or pearlites.

When two centrifugal compressors with the same two-side structure are connected in parallel and work, working gas enters the runner of the first-stage compressor 1 from the inlet of the first-stage compressor volute 24, flows through the first-stage compressor impeller 22, flows into a pipeline from the outlet of the first-stage compressor volute 24, then enters the runner of the second-stage compressor 2 from the inlet of the second-stage compressor volute 34, flows through the second-stage compressor impeller 32, is discharged from the outlet of the second-stage compressor volute 34, and after the outlet airflows of the two centrifugal compressors are combined, the working gas is discharged from the heat-insulating cold box 1, so that the compression process of the working gas is completed.

In the working process of the centrifugal compressor shown in fig. 1, as the structures at two sides of the compressor are the same, the influence of axial force can be avoided, and as shown in fig. 5-8, the rotor structure and the bearing schematic diagram of the centrifugal compressor with the same structures at two sides are adopted. As shown in FIG. 5, the thrust bearing is not needed in the centrifugal compressor, the thrust surface is an inclined surface on the rotor, and only the radial bearing 231 is needed to support the rotor to run at high speed, so that the thrust area can be increased on the premise of not increasing the outer diameter of the main shaft, and the running stability of the rotor is improved; as shown in fig. 6, the inclined plane on the rotor is used as a thrust surface, and a thrust bearing 232 is simultaneously arranged, the thrust bearing 232 is parallel to the thrust surface of the rotor, and the thrust bearing 232 and a radial bearing 231 jointly support the rotor to run at high speed; as shown in fig. 7, the vertical plane on the rotor is used as a thrust surface, a thrust disc is not required to be arranged singly, and thrust bearings 232 are positioned on two sides of the thrust surface to support the rotor to run; as shown in fig. 8, the rotor is further provided with two thrust disks 233, the thrust disks 233 and the rotor spindle 212 are in interference fit, and the thrust bearings 232 are located at two sides of the thrust disks.

During operation of the centrifugal compressor, primary compressor rotor 212 is supported by the gas bearings and drives primary compressor wheel 22 into rotation. During operation, since the same configuration of primary compressor wheel 22 is employed on both sides of primary compressor 2, there is substantially no need to consider the effect of axial forces on compressor operation. The labyrinth seal structure is arranged inside the first-stage compressor end cover 213, so that gas leakage is prevented, and the first-stage compressor end cover 213 is welded with the first-stage compressor shell 211, so that cold leakage can be prevented. The end part of the compressor motor is provided with a heat insulation plate, and the heat insulation plate is made of polytetrafluoroethylene or epoxy resin, so that the compressor is prevented from being leaked and cooled. The operation of the secondary compressor 3 is similar to that of the primary compressor 2, and thus will not be described in detail.

The heat insulation cold box and the pipeline shown in the figure 1 are connected by welding to prevent gas leakage, and in the working process of the centrifugal compressor, the inlet air temperature of the compressor can reach-268 ℃ because the inlet air temperature is lower, especially when helium liquefaction work is carried out, so that whether the motor can normally operate at extremely low temperature or not needs to be considered. Since the pressure and the temperature of the compressor are raised in the compression process, the outlet temperature of the secondary compressor volute 34 is relatively high, and the working gas with higher temperature can be introduced into the motors of the primary compressor 2 and the secondary compressor 3 through the secondary compressor volute opening 341 to complete the heat preservation work of the motors. If the air flow led out by the secondary volute cannot completely realize the heat preservation work of the compressor motor, the stator of the primary centrifugal compressor 2 can be heated by the air flow in the air storage tank 51 according to the feedback of the temperature sensor, and the stator of the secondary centrifugal compressor 3 can be heated by the air flow in the air storage tank 52, so that the heat preservation work of the motor can be assisted.

Through setting up adiabatic cold box, setting up each cavity in the cold box, measure such as setting up motor insulation circuit reduce the compressor and leak cold, guarantee the normal work of motor to make the compressor can be at the normal operating under the import temperature be-268 ℃ operating mode.

Example 2:

Fig. 2 is a schematic structural diagram of a single two-stage centrifugal compressor, and the two-stage centrifugal compressor 6 has advantages of compact structure and small volume, when the single two-stage centrifugal compressor shown in fig. 2 is used for operation, the whole machine is assembled and welded according to the schematic structural diagram of the two-stage centrifugal compressor 6, then the whole machine is placed in an adiabatic cold box, wherein the first-stage side of the two-stage centrifugal compressor is located in a fifth adiabatic chamber 15, the motor is located in a sixth adiabatic chamber 16, the second-stage side of the two-stage centrifugal compressor is located in the sixth adiabatic chamber 16, vacuum extraction, pearlite filling or adiabatic material wrapping of the two adiabatic chambers are performed according to the situation as described in embodiment 1, and then the two-stage centrifugal compressor 6 starts to operate.

Working gas enters the inside of the compressor from the inlet of the two-stage compressor one-stage volute 641, flows through the two-stage compressor one-stage impeller 621, enters the two-stage centrifugal compressor two-stage volute 642 through the middle connecting pipe, flows through the two-stage compressor two-stage impeller 622, is discharged from the outlet of the two-stage centrifugal compressor two-stage volute 642, and then flows out of the heat-insulating cold box through a pipeline to perform the next work.

The rotor structure and bearing structure of the single two-stage centrifugal compressor shown in fig. 2 are shown in fig. 9, the first-stage impeller 621 and the second-stage impeller 622 are fixed at two ends of the motor rotor 612, and because of the difference between the structures of the two sides, it is necessary to consider the influence of axial force on the normal operation of the compressor, a thrust disc is arranged at the first-stage side of the rotor, two thrust bearings are arranged at two sides of the thrust disc arranged at the first-stage side, and the thrust bearing and the radial bearing jointly support the rotor to operate at high speed.

In order to ensure the normal operation of the centrifugal compressor, the heat preservation operation of the motor is required, and the temperature of the motor is monitored through a temperature sensor. An opening is arranged at the outlet of the two-stage volute, the opening is communicated with the inside of the motor of the centrifugal compressor, and the motor is insulated by air flow with higher temperature at the outlet. If the air flow cannot completely realize the heat preservation work, the air storage tank 53 is used for heating the compressor stator 611, so that the compressor can still normally operate in a low-temperature environment.

Example 3:

FIG. 3 is a schematic diagram of a configuration in which two-stage centrifugal compressors are employed in series, and when a higher air flow pressure is desired, the two-stage centrifugal compressors shown in FIG. 3 may be employed in series. When the two-stage compressors shown in fig. 3 are connected in series for operation, the whole machine is assembled and welded according to the structural diagram shown in fig. 3, then the whole machine is placed in an adiabatic cold box, and after the vacuum extraction, the pearlite filling or the adiabatic material wrapping operation of the adiabatic chamber as described in embodiment 1 is completed, the two-stage centrifugal compressors 7 and 8 start to operate.

When two compressors are connected in series, the outlet air flow of the two-stage centrifugal compressor 7 is discharged into the inlet of the two-stage centrifugal compressor 8 through the connecting pipeline, compressed in the runner of the two-stage centrifugal compressor 8, finally discharged from the outlet of the two-stage centrifugal compressor 8, and then flows out of the heat-insulating cold box through the pipeline to perform the next operation, thus completing the compression process of the two centrifugal compressors connected in series.

In order to ensure that the two-stage centrifugal compressors connected in series normally work, heat preservation work of the motor is needed, and the temperature of the motor is monitored through a temperature sensor. Openings are arranged at the outlets of the two-stage volutes of the two-stage centrifugal compressors 7 and 8, the two-stage volute is communicated with the inside of the motor of the centrifugal compressor, and the motor is insulated by air flow with higher temperature at the outlet. If the air flow cannot completely realize heat preservation, the motor stator of the two-stage centrifugal compressor 7 is heated through the air storage tank 54, and the motor stator of the two-stage centrifugal compressor 8 is heated through the air storage tank 55, so that the compressor can still normally operate in a low-temperature environment.

Example 4:

FIG. 4 is a schematic diagram of a low temperature centrifugal compressor employing single stage compression, as shown, with airflow entering from the compressor volute, flowing through the impeller, exiting from the volute outlet from the insulated cold box. As shown in the figure, the impeller and the motor are in different chambers, and the same vacuum degree or different vacuum degrees or wrapping heat insulating materials can be arranged on the two chambers according to different use environments and use requirements, so that the cold leakage loss of the compressor is reduced, and meanwhile, the heat insulation loop is arranged, so that the normal operation of the compressor at a lower working environment temperature is ensured.

Claims (10)

1. The invention discloses a low-temperature oil-free centrifugal compressor placed in an adiabatic environment, which comprises an adiabatic cold box, a centrifugal compressor unit, a connecting pipeline and a vacuum pump, and is characterized in that:

(1) The centrifugal compressor unit is arranged in the heat-insulating cold box and can operate within the inlet temperature range of-268 ℃ to-20 ℃;

(2) A plurality of chambers are arranged in the heat-insulating cold box;

(3) The centrifugal compressor comprises a motor, an impeller, a volute and a bearing;

(4) When the centrifugal compressors with the same structures at two sides are adopted, the two ends of the centrifugal compressor adopt the same impellers, the motor rotors have the same structures and are symmetrically distributed, axial force is not required to be considered, the thrust disc can not be arranged on the compressor at the moment, and the thrust surface is a vertical surface perpendicular to the main shaft or an inclined surface forming a certain included angle with the main shaft of the rotor;

(5) The centrifugal compressor motor does not need to consider motor cooling when running under a low-temperature working condition, the motor comprises a motor stator, a rotor and an end cover, an air inlet and an air outlet are formed in a motor shell, and the motor rotor is supported by adopting a gas bearing or a gas-magnetic hybrid bearing;

(6) The impellers at two ends of the centrifugal compressor and the middle motor are positioned in different chambers of the heat-insulating cold box;

(7) The centrifugal compressor volute is divided into a first-stage volute and a second-stage volute, a gas circuit is additionally arranged at the second-stage volute, the gas circuit is communicated with the inside of the centrifugal compressor motor to form a motor heat insulation loop, a temperature sensor is arranged on the heat insulation loop, the temperature of the motor can be judged, and the direction and the gas quantity of the gas circuit are controlled through an electric opening regulating valve;

(8) When the centrifugal compressor adopts a gas bearing for supporting, working medium self-lubrication is adopted, the gas bearing is divided into a radial bearing and a thrust bearing, and the bearing type can be full dynamic pressure type, dynamic and static pressure type combined type or full static pressure type.

2. The low temperature oil-free centrifugal compressor in an adiabatic environment according to claim 1, wherein said low temperature centrifugal compressor is operated at an inlet temperature of-268 ℃ and the compressor power consumption is greatly reduced, and the working gas is helium, air, nitrogen, neon or hydrogen.

3. A low temperature oil free centrifugal compressor in a thermally insulated environment as claimed in claim 1 wherein said centrifugal compressor is of the same construction on both sides, the compressor may be supported by radial bearings only or by radial bearings plus thrust bearings, the thrust bearings being parallel to the thrust faces when the thrust bearings are set up.

4. The low temperature oil-free centrifugal compressor in an adiabatic environment according to claim 1, wherein the impellers and the intermediate motor are positioned at two ends of different chambers of the adiabatic cold box, and the impellers and the motor can be positioned in the same vacuum environment, or in environments with different vacuum degrees, or in environments wrapped by adiabatic materials or pearlized sand.

5. The low-temperature oil-free centrifugal compressor in an adiabatic environment according to claim 1, wherein the low-temperature centrifugal compressor is operated at a low temperature without considering motor cooling, the temperature of the motor is monitored by a temperature sensor arranged on a heat preservation loop, when the temperature of the motor is lower, a motor of the first-stage compressor and the second-stage compressor are heated by using higher-temperature gas at the outlet of the second-stage volute through an electric opening regulating valve, so that the normal operation of the motor is ensured, and if the gas at the outlet of the second-stage volute cannot completely meet the heat preservation function of the motor, the auxiliary heat preservation operation can be performed on a motor shell through an additionally arranged gas storage tank, so that the normal operation of the motor is ensured.

6. A low temperature oil free centrifugal compressor in an adiabatic environment as claimed in claim 1 wherein said centrifugal compressor train may be of 1-12 stages, with interstage cooling further provided between each stage of compressors.

7. The low temperature oil-free centrifugal compressor placed in an adiabatic environment according to claim 1, wherein said centrifugal compressor unit is connected in parallel with 1 to 8 centrifugal compressors having the same structure on both sides or connected in series with 1 to 8 multistage centrifugal compressors.

8. The low temperature oilless centrifugal compressor placed in an adiabatic environment as defined in claim 1, wherein said gas bearing is divided into a radial bearing and a thrust bearing, the radial bearing being of a dynamic pressure type or a static pressure type, and the thrust bearing being of a dynamic pressure type or a static pressure type.

9. The low temperature oil-free centrifugal compressor placed in an adiabatic environment according to claim 1, wherein said connection pipe has elasticity to avoid the effect of stress caused by expansion with heat and contraction with cold.

10. The low temperature oilless centrifugal compressor in adiabatic environment as defined in claim 1, wherein said motor end is provided with an insulation board made of polytetrafluoroethylene or epoxy resin, and the compressor terminal is led out from the motor stator, through the compressor housing and the adiabatic chamber where the motor is located, and out of the adiabatic cold box.