A gas-bearing centrifugal compressor with a grooved bearing

Abstract

The application discloses a gas floating centrifugal compressor with a grooved bearing, which comprises a motor, an impeller, an air inlet, an air outlet and a connecting pipe. The motor comprises a shell and a rotor, the shell is internally provided with a first chamber and a second chamber at two ends respectively, the rotor is provided with a first groove, and when the rotor rotates, gas is introduced into the first groove to form a gas film, so that a grooved gas floating radial bearing is formed. The impeller is fixed to the end of the rotor and located in the first chamber and / or the second chamber. The air inlet of the first chamber is communicated with the air inlet, the air outlet is communicated with one end of the connecting pipe, the air outlet of the second chamber is communicated with the air outlet, and the air inlet is communicated with the other end of the connecting pipe. By adopting the grooved gas floating bearing, the limitation of the DN value of the foil type dynamic pressure bearing can be eliminated, and thus the compressor can be used in a medium-pressure and high-pressure refrigeration system.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, and in particular to an air-floating centrifugal compressor with grooved bearings. Background Technology

[0002] Thermal management refers to the management and control of the temperature of the overall system, discrete components, or their environment, with the aim of maintaining the normal operation of each component or improving its performance or lifespan. Currently, thermal management is commonly required in fields such as electrochemical energy storage, and it has a significant impact on the performance, lifespan, and safety of energy storage systems. Because liquid-cooled thermal management systems have strong heat exchange capabilities, allowing cell temperature differences to be within 3°C, they can significantly extend the lifespan of energy storage systems compared to air-cooled systems. Therefore, liquid-cooled systems are currently widely used in the energy storage field.

[0003] Energy storage liquid cooling systems typically require a cooling capacity of 100kW or less, and these small-capacity refrigeration cycles often employ scroll compressors. To improve the reliability of the compressor and the system, air bearings can be used in scroll compressors. Common air bearings are foil bearings. Due to manufacturing limitations, their radial diameter is usually above 20mm, while their DN value is usually below 400. The DN value equals diameter (mm) * rotational speed (krpm), meaning the maximum speed of foil bearings is only around 200krpm, limiting their application range. For medium-pressure refrigeration systems with a cooling capacity of kilowatts or high-pressure refrigerant (R410a, CO2, etc.) refrigeration systems with a cooling capacity below 30kW, foil bearings cannot meet the requirements. Summary of the Invention

[0004] To address some or all of the problems in the prior art, the present invention provides an air-float centrifugal compressor with grooved bearings, comprising:

[0005] An electric motor, comprising:

[0006] The shell has a first chamber and a second chamber respectively located at its two ends;

[0007] A rotor having a first groove, wherein when the rotor rotates, gas is introduced into the first groove to form a gas film, thereby forming a grooved air-bearing radial bearing; and

[0008] stator;

[0009] An impeller is arranged at the end of the rotor and located within the first chamber and / or the second chamber;

[0010] An air inlet, which is connected to the air inlet of the first chamber;

[0011] An exhaust port, which is connected to the exhaust port of the second chamber;

[0012] The connecting pipe has its two ends connected to the air outlet of the first chamber and the air inlet of the second chamber, respectively.

[0013] Furthermore, the motor is a high-speed permanent magnet synchronous motor.

[0014] Furthermore, the air-float centrifugal compressor also includes:

[0015] A thrust disk is disposed at the end of the rotor, and a second groove is provided on the thrust disk. When the rotor rotates, gas is introduced into the second groove to form an air film, thereby forming a grooved air-bearing thrust bearing.

[0016] Furthermore, the first or second chamber includes a multi-stage impeller.

[0017] Furthermore, the impeller in the first chamber and the impeller in the second chamber are designed back-to-back.

[0018] Furthermore, the impeller is fixed to the end of the rotor by a locking nut.

[0019] Furthermore, the impeller is a closed impeller.

[0020] Furthermore, the impeller is an open impeller.

[0021] Furthermore, a sealing structure is provided on the impeller cover side.

[0022] Furthermore, end caps are provided at the air outlets of the first and second chambers.

[0023] Furthermore, the air-float centrifugal compressor also includes an interstage air supply port, which is disposed on the connecting pipe.

[0024] This invention provides an air-floating centrifugal compressor with grooved bearings. Grooves are cut into the shaft and / or thrust plate to form air-floating bearings, eliminating the need for lubrication and the need for return oil lines, thereby improving the reliability of the compressor and the system. Simultaneously, since the shaft does not contact the bearing during operation, but rather the motor rotor is suspended by an air film, the bearing life can be increased by at least 100%. Furthermore, for the same cooling capacity, the size and weight of a centrifugal compressor based on a high-speed permanent magnet synchronous motor are approximately 50% smaller and the mass can be reduced by approximately 90% compared to a scroll compressor. This allows for the placement of more batteries within a container of the same size when applied to energy storage systems, thus contributing to increased energy density. The advantages of high-speed centrifugal compressors become more significant as the cooling power requirements of energy storage systems increase. Moreover, because the grooves are cut into the shaft, there are no DN value limitations for the air-floating bearings. Compared to foil-type air-floating centrifugal compressors, this allows for higher rotational speeds, smaller compressor sizes, and a wider range of applications. Specifically, the air bearing formed by the groove can reach a speed of over 500krpm, so it can be used in medium-pressure refrigeration systems with a cooling capacity of less than 10kW and high-pressure (R410a, CO2, etc.) refrigeration systems with a cooling capacity of less than 30kW. Attached Figure Description

[0025] To further illustrate the above and other advantages and features of the various embodiments of the present invention, a more specific description of the various embodiments of the present invention will be presented with reference to the accompanying drawings. It is to be understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by identical or similar reference numerals for clarity.

[0026] Figure 1 A schematic diagram of the configuration of an air-floating centrifugal compressor with grooved bearings according to an embodiment of the present invention is shown.

[0027] Figure 2 A schematic diagram of the thrust disk according to an embodiment of the present invention is shown;

[0028] Figures 3a-3d Schematic diagrams of different rotor systems in an air-float centrifugal compressor with grooved bearings according to embodiments of the present invention are shown respectively.

[0029] Figure 4 This diagram illustrates the structure of a high-pressure refrigerant air-float centrifugal compressor with a small cooling capacity, according to an embodiment of the present invention; and

[0030] Figure 5 This diagram shows a cross-sectional schematic of a high-pressure refrigerant air-float centrifugal compressor with a small cooling capacity, according to an embodiment of the present invention. Detailed Implementation

[0031] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details. Furthermore, it should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0032] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0033] It should be noted that the embodiments of the present invention describe the process steps in a specific order; however, this is only for illustrating the specific embodiment and not for limiting the order of the steps. On the contrary, in different embodiments of the present invention, the order of the steps can be adjusted according to the process.

[0034] In embodiments of the present invention, the term "main gas path" refers to the gas flow path through which gas enters the compressor via the inlet, is compressed, and then exits via the outlet. The term "high-pressure side" refers to the side of the compressor with higher internal pressure, i.e., the side where the final stage impeller is located, while the term "low-pressure side" refers to the side of the compressor relative to the high-pressure side. Under normal circumstances, gas flows from the high-pressure side through the air bearing to the low-pressure side and then returns to the main gas path.

[0035] To avoid the limitation of DN value and increase bearing speed to meet the requirements of medium-pressure and high-pressure refrigeration systems, this invention replaces the foil bearing with a grooved bearing in the existing air-float centrifugal compressor. Since the grooved bearing has grooves directly carved on the shaft, it is not limited by DN value. This makes it still applicable to the same fields as foil-type air-float centrifugal compressors, and it can achieve higher speeds and smaller compressor sizes. Testing has shown that the grooved bearing can reach speeds of over 500 rpm, thus it can be used in medium-pressure refrigeration systems with a cooling capacity of less than 10 kW and high-pressure (R410a, CO2, etc.) refrigeration systems with a cooling capacity of less than 30 kW. The following description, in conjunction with the accompanying drawings, further illustrates the invention.

[0036] Figure 1A schematic diagram of the configuration of an air-floating centrifugal compressor with grooved bearings according to an embodiment of the present invention is shown. As shown, in this embodiment of the present invention, the air-floating centrifugal compressor includes a motor and an impeller 200. The rotor of the motor is provided with a first groove 111. When the motor shaft rotates, gas is introduced into the first groove to form an air film supporting the high-speed rotation of the rotor, achieving the effect of an air-floating radial bearing.

[0037] In order to withstand the axial thrust generated during compressor operation, in one embodiment of the present invention, such as Figure 1 As shown, a thrust disk 112 is also provided at one end of the rotor. Figure 2 A schematic diagram of the thrust disk according to an embodiment of the present invention is shown. Figure 2 As shown, the surface of the thrust disk is provided with a second groove 113. When the motor shaft rotates, gas is introduced into the second groove to form a gas film, so that the thrust shaft and the bearing have no contact, the bearing has almost no wear, and mechanical losses and noise can be significantly reduced or even eliminated, achieving the effect of an air-floating thrust bearing. As shown, the impeller 200 is located at the end of the rotor 101 and is used to compress the low-temperature, low-pressure refrigerant gas from the evaporator to form a high-temperature, high-pressure refrigerant gas that is discharged into the condenser. Here, the terms "radial" and "axial" refer to the radial and axial directions of the rotor or its rotation axis.

[0038] Figures 3a-3d The figures show schematic diagrams of different rotor system configurations in an air-floating centrifugal compressor with grooved bearings according to embodiments of the present invention. As shown in the figures, in an embodiment of the present invention, a set of first grooves is provided at both ends of the rotor, which is equivalent to providing two air-floating radial bearings at both ends of the rotor. There is a certain distance between the two sets of first grooves, and they can be symmetrically distributed on the rotor.

[0039] like Figures 3a-3d As shown, the thrust disk 112 can be located at either end of the rotor, or one thrust disk 112 can be located at each end of the rotor. When only one thrust disk is provided, a set of second grooves 113 can be provided on each of the two side surfaces of the thrust disk 112, which is equivalent to providing an air-bearing thrust bearing on each side of the thrust disk. As shown, when the motor shaft rotates, air films are formed at the two sets of second grooves, which can withstand axial thrust in opposite directions respectively. When two thrust disks are provided, a set of second grooves 113 can be provided on the opposite sides or the far sides of the two thrust disks 112. When the motor shaft rotates, air films are formed at the two sets of second grooves, which can withstand axial thrust in opposite directions respectively.

[0040] It should be understood that in different embodiments of the present invention, single-stage, double-stage, or multi-stage impellers can be provided according to actual needs. When only a single-stage impeller is provided, the impeller can be located at either end of the rotor, and the side with the impeller can be designated as the high-pressure side, while the side without the impeller can be designated as the low-pressure side. When two-stage impellers are provided, the two impellers can be located at both ends of the rotor, or both can be located at either end of the rotor. When they are located at both ends of the rotor, the side with the preceding impeller can be designated as the low-pressure side, and the side with the following impeller can be designated as the high-pressure side. When both are located at one end of the rotor, the side with the impeller can be designated as the high-pressure side, and the side without the impeller can be designated as the low-pressure side. Similarly, when multiple impellers are provided, the multiple impellers can be equally or unequally distributed at both ends of the rotor, or all of them can be distributed at any one end of the rotor. When they are distributed at both ends of the rotor, the side with the preceding impeller can be designated as the low-pressure side, and the side with the following impeller can be designated as the high-pressure side. When all of them are distributed at one end of the rotor, the side with the impeller can be designated as the high-pressure side, and the side without the impeller can be designated as the low-pressure side. Based on this, when the rotor rotates, a portion of the high-pressure gas compressed by the impellers in the main air passage will enter the radial bearing on the high-pressure side under pressure, then pass through the air gap between the motor stator and rotor into the radial bearing on the low-pressure side, and return to the main air passage. When a thrust disc with grooved surfaces is provided, the high-pressure gas will also pass through the second groove to form a gas film, bearing the axial thrust. To effectively reduce the axial thrust on the thrust disc, in one embodiment of the invention, the impeller on the low-pressure side and the impeller on the high-pressure side are arranged back-to-back, thereby ensuring that the axial thrust directions of the impellers on the high-pressure and low-pressure sides are opposite and cancel each other out. In this embodiment, the impeller can be an open impeller or a closed impeller. A closed impeller can eliminate the secondary flow from the blade pressure surface to the suction surface caused by the blade tip clearance, effectively improving the compressor's aerodynamic efficiency, while an open impeller can withstand higher speeds and has a smaller size. Therefore, in practical applications, either an open or closed impeller can be selected according to requirements. In one embodiment of the invention, the impeller is fixed to the rotor by a locking nut.

[0041] Figure 4 and Figure 5 The figures show a structural schematic diagram and a cross-sectional schematic diagram of a small-capacity high-pressure refrigerant air-float centrifugal compressor according to an embodiment of the present invention. As shown in the figures, a small-capacity high-pressure refrigerant air-float centrifugal compressor includes a motor 100, an impeller, an air inlet 301, an air outlet 302, and a connecting pipe 303.

[0042] The motor 100 includes a rotor 101, a stator 102, and a housing 103. The stator 102 is fixed inside the housing 103, and the central axis of the rotor 101 coincides with the central axis of the stator 102. The rotor 101 has two sets of first grooves 111 at both ends, and a thrust plate 112 is provided on the side near the air inlet 301. The two sides of the thrust plate are respectively provided with a set of second grooves 113 to withstand axial thrust directed towards the low-pressure side or the high-pressure side.

[0043] As shown in the figure, the housing 103 has a first chamber and a second chamber at its two ends. The air inlet of the first chamber is connected to the air inlet 301 of the compressor; that is, the air inlet 301 is the air inlet of the first chamber. A first impeller 201 is installed in the first chamber and fixed to the first end of the rotor 101. A connecting pipe 303 connects the first chamber and the second chamber. Gas compressed by the first impeller 201 flows out of the outlet of the first chamber, enters the connecting pipe 303, and then enters the second chamber through the air inlet. A second impeller 202 is installed in the second chamber and fixed to the second end of the rotor 101. Most of the gas compressed by the second impeller 202 flows out from the outlet of the second chamber, which is connected to the exhaust port 302 of the compressor; that is, the exhaust port 302 is the air outlet of the second chamber. As shown in the figure, in an embodiment of the present invention, a first end cap 135 and a second end cap 136 are respectively provided at the air outlets of the first chamber and the second chamber. There are gaps between the first end cap 135 and the second end cap 136 and the rotor 101. Simultaneously, there is a certain gap between the first end cap 135 and the first impeller 201, allowing gas flowing through the first and second grooves to return to the main air path via this gap. Similarly, there is a certain gap between the second end cap 136 and the second impeller 202, allowing a portion of the gas compressed by the second impeller 202 to enter the first and second grooves under pressure, forming an air film and achieving an air flotation effect. In one embodiment of the present invention, as mentioned above, the first impeller 201 and the second impeller 202 are designed back-to-back, so that the axial thrust directions of the first and second impellers are opposite and cancel each other out, thereby effectively reducing the axial thrust on the thrust plate. In one embodiment of the present invention, the first impeller 201 and the second impeller 202 are fixed to the rotor 101 by the first locking nut 211 and the second locking nut 221, respectively.

[0044] As shown in the figure, a first pressure shell 131 and a second pressure shell 132 are respectively provided on the outer sides of both ends of the motor. A first sealing ring 133 is provided between the first pressure shell 131 and the first impeller 201, and a second sealing ring 134 is provided between the second pressure shell 132 and the second impeller 202. The first and second sealing rings can significantly reduce the backflow effect from the outlet to the inlet of the first and second impellers, and can further improve the compressor efficiency.

[0045] In order to reduce the compression power consumption of the second impeller 202, in one embodiment of the present invention, an interstage air inlet 331 is also provided on the connecting pipe 303 to access the exhaust gas from the economizer, thereby cooling the gas compressed by the first impeller, and thus achieving the purpose of reducing the compression power consumption of the high-pressure impeller and improving the efficiency of the system.

[0046] In one embodiment of the present invention, the motor 100 adopts a high-speed permanent magnet synchronous motor, whose bearing is a non-contact bearing when working, so it can withstand a higher speed than ordinary ball bearings. According to the Euler formula for compressors, Δh=U2Cu2-U1Cu1, for compressors with the same work capacity, the higher the speed, the smaller the radial dimension. Therefore, using a permanent magnet synchronous motor can improve the power density of the compressor.

[0047] The working principle of the air-floating centrifugal compressor, as described above, is as follows: Gas compressed by the second impeller enters the high-pressure side through the gap between the second impeller and the second end cover, and the gap between the second end cover and the rotor. An air film forms at the first groove on the high-pressure side, achieving an air-floating effect. Then, it passes through the air gap between the stator and the rotor to reach the first groove on the low-pressure side, forming an air film. Subsequently, it passes through the gap between the thrust plate and the motor housing, and the gap between the thrust plate and the first end cover, forming air films at the second grooves on both sides of the thrust plate, achieving the air-floating effect. Finally, it passes sequentially through the gap between the first end cover and the rotor, and the gap between the first impeller and the first end cover, entering the first chamber, i.e., the exhaust port of the first impeller, and returning to the main air path to achieve internal circulation. Compared to static pressure air-floating bearings, the air-floating centrifugal compressor can omit the external air supply channel, simplifying the system structure and improving reliability. The grooved dynamic pressure air-floating bearing eliminates the DN value limitation of foil-type dynamic pressure bearings, allowing speeds up to 500 krpm. It can be used in medium-pressure refrigeration systems with a cooling capacity of less than 10 kW and high-pressure refrigeration systems with a cooling capacity of less than 30 kW. Its rotational speed is higher, and for applications of foil bearings, the compressor size can be reduced by 20%-30%.

[0048] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A centrifugal compressor with grooved bearings, characterized in that, include: An electric motor, comprising: A housing, in which a stator is fixed, and at its ends respectively provided a first chamber and a second chamber, wherein the air outlets of the first chamber and the second chamber are respectively provided with a first end cap and a second end cap; and A rotor having a first groove, wherein the rotor, when rotating, introduces gas into the first groove to form a gas film in order to form a grooved air-floating radial bearing. An impeller is arranged at the end of the rotor and located within the first chamber and the second chamber; An air inlet, which is connected to the air inlet of the first chamber; An exhaust port, which communicates with the exhaust port of the second chamber; and The connecting pipe has its two ends connected to the air outlet of the first chamber and the air inlet of the second chamber, respectively. The gas compressed by the impeller in the first chamber enters the second chamber through the connecting pipe, and is compressed again by the impeller in the second chamber. The gas compressed again enters the motor through the gap between the impeller and the second end cover, and between the second end cover and the rotor, and forms an air film at the first groove near the second chamber to achieve an air flotation effect. Then, it passes through the air gap between the stator and the rotor to reach the first groove near the first chamber to form an air film, and enters the first chamber through the gap between the first end cover and the rotor, and the gap between the impeller and the first end cover, and returns to the main air path.

2. The air-float centrifugal compressor as described in claim 1, characterized in that, The motor is a high-speed permanent magnet synchronous motor.

3. The air-float centrifugal compressor as described in claim 1, characterized in that, Also includes: A thrust disk is disposed at the end of the rotor, and a second groove is provided on the thrust disk. When the rotor rotates, gas is introduced into the second groove to form an air film, thereby forming a grooved air-bearing thrust bearing.

4. The air-float centrifugal compressor as described in claim 1, characterized in that, The impeller in the first chamber and the impeller in the second chamber are designed back-to-back.

5. The air-float centrifugal compressor as described in claim 1, characterized in that, The first or second chamber includes multiple stages of impellers.

6. The air-float centrifugal compressor as described in claim 1, characterized in that, The impeller is fixed to the end of the rotor by a lock nut.

7. The air-float centrifugal compressor as described in claim 1, characterized in that, The impeller can be a closed impeller or an open impeller.

8. The air-float centrifugal compressor as described in claim 1, characterized in that, The impeller has a sealing structure on the wheel cover side.

9. The air-float centrifugal compressor as described in claim 1, characterized in that, The air flotation centrifugal compressor also includes an interstage air supply port, which is located on the connecting pipe.

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