Refrigeration system

Abstract

A refrigeration system using a Brayton cycle that generates cold energy using a refrigerant compressed by a compressor unit arranged on a refrigerant path. The compressor unit includes: a plurality of compressors arranged side by side with respect to the refrigerant path; a plurality of first motors for driving the plurality of compressors, respectively; an expander-integrated compressor configured integrally with an expander; and a second motor for driving the expander-integrated compressor. The plurality of compressors have a larger number of units than the expander-integrated compressor.

Description

Technical Field

[0001] This disclosure relates to refrigeration systems utilizing the Brayton refrigeration cycle. Background Technology

[0002] As a refrigeration cycle, a refrigeration system utilizing the Brayton refrigeration cycle is known. The Brayton refrigeration cycle is a thermodynamic cycle consisting of an insulated compression process, an isobaric heating process, an insulated expansion process, and an isobaric cooling process. It is constructed by arranging components corresponding to each process on the refrigerant lines through which the refrigerant circulates. These components constituting the refrigeration cycle are designed according to the required refrigeration capacity of the refrigeration unit.

[0003] Patent Document 1 discloses an example of a refrigeration system utilizing the Brayton refrigeration cycle. In Patent Document 1, the compressor unit corresponding to the insulated compression process achieves an appropriate compression ratio corresponding to the required refrigeration capacity by having a multi-stage compressor connected in series on the refrigerant line. Furthermore, a portion of the multi-stage compressor is configured as an integrated expander compressor sharing a common rotating shaft with the expander corresponding to the insulated expansion process, utilizing the power generated in the expander as part of the power to drive the compressor, thereby improving efficiency. Moreover, in Patent Document 1, by connecting the compressors that constitute the compressor unit in parallel, the amount of refrigerant circulating in the refrigeration cycle is increased, thus improving the refrigeration capacity.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-219125 Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] In such refrigeration systems, when expanding the refrigeration capacity of different product specifications, it is generally necessary to redesign each component of the refrigeration system, and reducing the cost and time required for development becomes a challenge. For example, the compressors and expanders that make up the refrigeration system need to be prepared in different models in advance according to the product specifications of the refrigeration system. When the existing models are insufficient, new models must be developed, which incurs significant costs and time.

[0009] As a method to reduce the cost and time required for such new development, in the case of developing a refrigerator with a higher freezing capacity than existing refrigerators, as mentioned in the aforementioned Patent Document 1, although the existing structure of parallel refrigeration cycle can be considered, it is not enough to avoid the increase in the number of required parts and the area occupied.

[0010] At least one embodiment of this disclosure was made in view of the above circumstances, and its purpose is to provide a refrigeration system that can be flexibly modified in design while suppressing the costs, time and space required for development and installation according to the required refrigeration capacity.

[0011] (II) Technical Solution

[0012] To address the aforementioned issues, at least one embodiment of the refrigeration system disclosed herein provides a refrigeration system that utilizes a Brayton cycle.

[0013] The Brayton cycle uses a refrigerant to generate cooling energy, and the refrigerant is compressed by a compressor unit located along the refrigerant path.

[0014] The compressor unit includes:

[0015] Multiple compressors are arranged side-by-side with respect to the refrigerant path;

[0016] Multiple first motors, each used to drive the multiple compressors;

[0017] An integrated expander compressor, which is integrally formed with an expander capable of expanding the refrigerant compressed by the compressor unit; and

[0018] The second motor is used to drive the integrated expander compressor.

[0019] The number of compressors is greater than that of the integrated expander compressor.

[0020] (III) Beneficial Effects

[0021] According to at least one embodiment of the present disclosure, a refrigeration system can be provided that allows for flexible design changes while minimizing the costs, time, and floor space required for development and installation, depending on the required refrigeration capacity. Attached Figure Description

[0022] Figure 1 This is a diagram schematically illustrating the overall structure of a refrigeration system according to one embodiment.

[0023] Figure 2 It is a schematic representation Figure 1 A cross-sectional view of a coaxial compressor.

[0024] Figure 3 It is a schematic representation Figure 1 A cross-sectional view of an integrated expander compressor.

[0025] Figure 4 It means Figure 1A flowchart of the startup method for the refrigeration system.

[0026] Figure 5A This is a schematic diagram illustrating one configuration of a refrigeration system comprising two coaxial compressors and one integrated expander compressor.

[0027] Figure 5B This is a schematic diagram illustrating another configuration of a refrigeration system comprising two coaxial compressors and one integrated expander compressor.

[0028] Figure 6A This is a schematic diagram illustrating one configuration of a refrigeration system comprising three coaxial compressors and one integrated expander compressor.

[0029] Figure 6B This is a schematic diagram illustrating another configuration of a refrigeration system comprising three coaxial compressors and one integrated expander compressor.

[0030] Figure 6C This is a schematic diagram illustrating another configuration of a refrigeration system comprising three coaxial compressors and one integrated expander compressor.

[0031] Figure 7A This is a schematic diagram illustrating one configuration of a refrigeration system comprising three coaxial compressors and two integrated expander compressors.

[0032] Figure 7B This is a schematic diagram illustrating another configuration of a refrigeration system comprising three coaxial compressors and two integrated expander compressors.

[0033] Figure 7C This is a schematic diagram illustrating another configuration of a refrigeration system comprising three coaxial compressors and two integrated expander compressors.

[0034] Figure 8A This is a schematic diagram illustrating one configuration of a refrigeration system comprising four coaxial compressors and two integrated expander compressors.

[0035] Figure 8B This is a schematic diagram illustrating another configuration of a refrigeration system comprising four coaxial compressors and two integrated expander compressors.

[0036] Figure 8C This is a schematic diagram illustrating another configuration of a refrigeration system comprising four coaxial compressors and two integrated expander compressors.

[0037] Figure 8D This is a schematic diagram illustrating another configuration of a refrigeration system comprising four coaxial compressors and two integrated expander compressors. Detailed Implementation

[0038] Hereinafter, several embodiments of the refrigeration system of this disclosure will be described with reference to the accompanying drawings.

[0039] However, the dimensions, materials, shapes, and relative arrangements of the constituent components described in these embodiments or shown in the accompanying drawings are not intended to limit the scope of the invention, but are merely illustrative examples.

[0040] Expressions indicating relative or absolute configurations, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly indicate such configurations but also indicate the state of relative displacement of angles or distances with tolerances or to the extent that the same function can be obtained.

[0041] For example, expressions such as "same," "equal," and "homogeneous" that indicate that things are in an equal state not only strictly represent the state of equality, but also indicate the state of difference in terms of the existence of tolerances or the degree to which the same function can be obtained.

[0042] For example, the descriptions of shapes such as quadrilaterals and cylinders not only refer to quadrilaterals and cylinders in the strict geometric sense, but also include shapes with concave and convex parts, chamfers, etc., within the range that can achieve the same effect.

[0043] On the other hand, the statement that "exists," "has," "possesses," "includes," or "has" one constituent element is not an exclusive statement that excludes the existence of other constituent elements.

[0044] First refer to Figure 1 The overall structure of a refrigeration system 100 according to one embodiment will be described. Figure 1 This is a schematic diagram showing the overall structure of a refrigeration system 100 according to one embodiment.

[0045] The refrigeration system 100 includes, in sequence along the refrigerant path 101 through which the refrigerant flows: a compressor unit 102 (110A, 110B, 110C) for compressing the refrigerant; an expander 103 for expanding the refrigerant; a cooling section 104 consisting of a heat exchanger for exchanging heat between the refrigerant and the object being cooled; and a cold energy recovery heat exchanger 105 for recovering the residual cold energy in the refrigerant after passing through the cooling section 104, thereby forming a Brayton cycle based on a counter-current heat exchanger method of a refrigeration cycle with stable circulating flow.

[0046] The refrigeration system 100 has a superconducting device 106 as the object of cooling, which utilizes a superconductor capable of superconductivity at extremely low temperatures. The superconducting device 106 is, for example, a superconducting cable. To maintain the extremely low temperature of the superconducting device 106, the refrigeration system 100 has a refrigerant path 107 for circulating liquid nitrogen cooled by a cooling section 104. The refrigerant path 107 is configured to exchange heat with the refrigerant flowing through the refrigerant path 101 of the refrigeration system 100 via the cooling section 104, and a pump 108 is provided for circulating the liquid nitrogen. Thus, the liquid nitrogen flowing through the refrigerant path 107, which is heated by the thermal load of the superconducting device 106, is cooled by exchanging heat with the refrigerant flowing through the refrigerant path 101 of the refrigeration system 100.

[0047] Furthermore, in the refrigerant path 101 of the refrigeration system 100, neon or the like is used as the refrigerant, but it is not limited to this, and the type of gas can be appropriately changed according to the cooling temperature, etc.

[0048] In the refrigeration system 100, the expander 103 through which the relatively low-temperature refrigerant flows, the cooling section 104, and the cold energy recovery heat exchanger 105 are housed in a cold box 109 that is insulated from the outside.

[0049] The cold box 109 has, for example, a vacuum insulation layer between its inner and outer surfaces, thereby preventing heat intrusion from the outside and reducing heat loss in the expander 103, cooling section 104, and cold energy recovery heat exchanger 105 housed within the cold box 109. On the other hand, the compressor unit 102 in the refrigeration system 100 is located outside the aforementioned cold box 109 because it is supplied with relatively high-temperature refrigerant.

[0050] The cold box 109 is positioned closer to the superconducting device 106, which is the object being cooled, than the compressor unit 102. This allows the cold energy generated in the cold box 109 to be supplied to the object being cooled with minimal loss, achieving good refrigeration efficiency. The compressor unit 102 and the cold box 109 are separate components, increasing layout flexibility; for example, the space required for the refrigeration system can be reduced by mounting the compressor unit on the cold box.

[0051] The compressor unit 102 includes a plurality of compressors 110 connected in series to the refrigerant path 101. In this embodiment, the compressor unit 102 is configured to perform multi-stage compression in three stages by including: a low-stage compressor 110A capable of compressing fluid; an intermediate compressor 110B capable of further compressing the fluid compressed by the low-stage compressor 110A; and a high-stage compressor 110C capable of further compressing the fluid compressed by the intermediate compressor 110B, wherein the low-stage compressor 110A, the intermediate compressor 110B and the high-stage compressor 110C are connected in series to the refrigerant path 101.

[0052] Furthermore, the number of compression stages in compressor unit 102 can be any number.

[0053] In addition, in compressor unit 102, a heat exchanger 112 is provided downstream of each of the plurality of compressors 110. The heat exchanger 112 is used to cool the refrigerant that has been heated by insulated compression by exchanging heat with cooling water. Specifically, a heat exchanger 112A is provided downstream of the low-stage compressor 110A, a heat exchanger 112B is provided downstream of the intermediate compressor 110B, and a heat exchanger 112C is provided downstream of the high-stage compressor 110C.

[0054] The refrigerant flowing through refrigerant path 101 is first heated by the insulated compression of the upstream low-stage compressor 110A, and then cooled by heat exchange with cooling water at the downstream heat exchanger 112A. Subsequently, the refrigerant is again heated by the insulated compression of the intermediate compressor 110B, and then cooled by heat exchange with cooling water at the downstream heat exchanger 112B. Furthermore, the refrigerant is again heated by the insulated compression of the advanced compressor 110C, and then cooled by heat exchange with cooling water at the downstream heat exchanger 112C.

[0055] Therefore, in compressor unit 102, efficiency is improved by repeatedly performing insulated compression based on compressor 110 and cooling based on heat exchanger 112 in multiple stages. That is, by repeatedly performing insulated compression and cooling in multiple stages, the Brayton cycle compression process can be made close to ideal isothermal compression. Although the more stages there are, the closer it is to isothermal compression, the number of stages is preferably determined after considering factors such as the selection of compression ratio, the complexity of the device structure, and the ease of operation caused by increasing the number of stages.

[0056] The refrigerant compressed by the compressor unit 102 is cooled by the cold energy recovery heat exchanger 105 and then expands insulatedly through the expander 103 to generate cold energy. The refrigerant discharged from the expander 103 exchanges heat with liquid nitrogen flowing through the refrigerant path 107 on the cooling target side in the cooling section 104, and its temperature rises due to the heat load.

[0057] After being heated in the cooling section 104, the refrigerant is introduced into the cold energy recovery heat exchanger 105, where it exchanges heat with the high-temperature compressed refrigerant that has passed through the heat exchanger 112C in the compressor unit 102, thereby recovering residual cold energy. As a result, the temperature of the refrigerant introduced into the expander 103 is reduced, and lower-temperature cold energy can be obtained.

[0058] In such a refrigeration system 100, a Brayton cycle is constructed using multiple rotating machines, such as multiple compressors 110 and expanders 103, included in the compressor unit 102. Here, the low-stage compressor 110A and the high-stage compressor 110C are configured to be connected to the output shaft 116A of a common power source, namely the first motor 114A (see reference). Figure 2 The coaxial compressors 118 at both ends of the compressor reduce the number of components and allow for installation in smaller spaces. The intermediate compressor 110B and expander 103 are also configured to be connected to the output shaft 116B of a common power source, namely the second motor 114B (see reference). Figure 3 The integrated expander compressor 120 at both ends of the expander 103 can reduce the number of parts and can be installed in a smaller space. Moreover, the power generated in the expander 103 helps the compression power of the intermediate compressor 110B, thereby achieving high efficiency.

[0059] Furthermore, among the multiple compressors 110 included in the compressor unit 102, it is possible to arbitrarily change which one is configured as a coaxial compressor 118 and which one is configured as an expander integrated compressor 120.

[0060] Refer to this Figure 2 as well as Figure 3 The structure of the coaxial compressor 118 and the integrated expander compressor 120 is described. Figure 2 It is a schematic representation Figure 1 A cross-sectional view of the coaxial compressor 118. Figure 3 It is a schematic representation Figure 1 A cross-sectional view of the integrated expander compressor 120.

[0061] like Figure 2 As shown, the coaxial compressor 118 is configured by connecting a low-stage compressor 110A and a high-stage compressor 110C to both sides of the output shaft 116A of the first motor 114A. In this embodiment, the first motor 114A is disposed between the low-stage compressor 110A and the high-stage compressor 110C, but in another embodiment, it may also be disposed outside the low-stage compressor 110A and the high-stage compressor 110C (for example, it may be disposed in the axial direction of the output shaft 116A in the order of the first motor 114A, the low-stage compressor 110A, and the high-stage compressor 110C).

[0062] The output shaft 116A of the first motor 114A is supported by a radial magnetic bearing 122-1 and a thrust magnetic bearing 126-1, which are disposed between the low-stage compressor 110A and the high-stage compressor 110C, allowing it to rotate non-contactly relative to the motor housing 130-1. The radial magnetic bearing 122-1 is positioned on both sides of the first motor 114A in the axial direction of the output shaft 116A, and uses magnetic force to levitate the output shaft 116A and bear the radial load. The thrust magnetic bearing 126-1 is positioned on one side of the first motor 114A in the axial direction of the output shaft 116A (in...). Figure 2 In the embodiment shown, the first motor 114A and the low-stage compressor 110A bear the thrust load of the output shaft 116A by magnetic force in such a way that a gap is formed between the first motor 114A and the axial turntable 127-1 provided on the output shaft 116A.

[0063] Furthermore, the thrust magnetic bearing 126-1 and the axial turntable 127-1 can also be disposed between the advanced compressor 110C and the first motor 114A. Additionally, although the axial turntable 127-1 is primarily disposed on one side of the first motor 114A to suppress fluid friction loss in this embodiment, it can also be disposed on both sides due to assembly considerations, if the outer diameter of the output shaft 116A of the first motor 114A is large.

[0064] The housing 128-1 of the coaxial compressor 118 is constructed along the axial direction of the output shaft 116A by interconnecting a motor housing 130-1, a low-stage compressor impeller housing 132-1, and a high-stage compressor impeller housing 132-3. The motor housing 130-1 is the housing defining the outer casing of the first motor 114A, and internally houses a rotor 136A integrally formed with the output shaft 116A, and a stator 138A disposed near the rotor 136A (the rotor 136A is integrally formed with the output shaft 116A). The low-stage compressor impeller housing 132-1 houses the impeller 140A of the low-stage compressor 110A, which is mounted on one end of the output shaft 116A. The high-stage compressor impeller housing 132-3 houses the impeller 140C of the high-stage compressor 110C, which is mounted on the other end of the output shaft 116A.

[0065] like Figure 3 As shown, the integrated expander compressor 120 is configured by connecting the intermediate compressor 110B and the expander 103 on both sides of the output shaft 116B of the second motor 114B. Although in this embodiment the second motor 114B is disposed between the intermediate compressor 110B and the expander 103, in another embodiment it may also be disposed outside the intermediate compressor 110B and the expander 103 (for example, it may be disposed in the axial direction of the output shaft 116B in the order of the second motor 114B, the intermediate compressor 110B, and the expander 103).

[0066] The output shaft 116B of the second motor 114B is supported by a radial magnetic bearing 122-2 and a thrust magnetic bearing 126-2 disposed between the intermediate compressor 110B and the expander 103, enabling it to rotate non-contactly relative to the motor housing 130-2. The radial magnetic bearing 122-2 is positioned on both sides of the second motor 114B in the axial direction of the output shaft 116B, and uses magnetic force to levitate the output shaft 116B and bear the radial load. The thrust magnetic bearing 126-2 is positioned on one side of the second motor 114B in the axial direction of the output shaft 116B (in...). Figure 3 In the embodiment shown, the second motor 114B and the intermediate compressor 110B bear the thrust load of the output shaft 116B by magnetic force in such a way that a gap is formed between the second motor 114B and the axial turntable 127-2 provided on the output shaft 116B.

[0067] Furthermore, the thrust magnetic bearing 126-2 and the axial turntable 127-2 can also be disposed between the expander 103 and the second motor 114B. Additionally, although the axial turntable 127-2 is primarily disposed on one side of the second motor 114B to suppress fluid friction loss in this embodiment, it can also be disposed on both sides due to assembly considerations when the outer diameter of the output shaft 116B of the second motor 114B is large.

[0068] The housing 128-2 of the integrated expander compressor 120 is constructed along the axial direction of the output shaft 116B by interconnecting a motor housing 130-2, an intermediate compressor impeller housing 132-2, and an expander impeller housing 134-1. The motor housing 130-2 is the housing of the second motor 114B, and internally houses a rotor 136B integrally formed with the output shaft 116B (the rotor 136B and the output shaft 116B are integrally formed), and a stator 138B disposed near the rotor 136B. The intermediate compressor impeller housing 132-2 houses the impeller 140B of the intermediate compressor 110B, which is mounted on one end of the output shaft 116B. The expander impeller housing 134-1 houses the impeller 142 of the expander 103, which is mounted on the other end of the output shaft 116B.

[0069] return Figure 1The compressor unit 102 includes multiple coaxial compressors 118 arranged side-by-side with respect to the refrigerant path 101. The coaxial compressors 118 in the compressor unit 102 are all common (of the same specifications), and the number of them is greater than that of the integrated expander compressor 120 in the compressor unit 102, and is set according to the refrigeration capacity required by the refrigeration system 100. In this embodiment, although the compressor unit 102 has two coaxial compressors 118A and 118B compared to one integrated expander compressor 120, a larger refrigeration capacity can be achieved by having three or more coaxial compressors 118. Furthermore, even when there are two integrated expander compressors 120, it is possible to have three or more coaxial compressors 118.

[0070] The number of coaxial compressors 118 included in compressor unit 102 is set according to the refrigeration capacity required by refrigeration system 100. For example, when the required refrigeration capacity of refrigeration system 100 increases, the flow rate of refrigerant through refrigerant path 101 increases, which can be addressed by increasing the number of coaxial compressors 118. Therefore, refrigeration system 100 can achieve specifications with different refrigeration capacities with less development burden by adjusting the number of coaxial compressors 118 included in compressor unit 102. Since the expander integrated compressor 120 can be adapted by only changing the design of the components (impeller housings 132-2 and 134-1) associated with the impeller 140B of intermediate compressor 110B and expander impeller 142, the development time and cost of coaxial compressors corresponding to the types of components required by refrigeration system 100 and the refrigeration capacity can be effectively reduced. In addition, compared with the case of coaxial compressors required to meet the refrigeration capacity of multiple refrigeration systems 100 configured in parallel, the footprint can be reduced.

[0071] Furthermore, in the refrigeration system 100, the first motor 114A of the coaxial compressor 118 and the second motor 114B of the integrated expander compressor 120 are common. In this way, by using a common specification for the drive motors between the coaxial compressor 118 and the integrated expander compressor 120, it is possible to realize refrigeration systems 100 with different refrigeration capacities while reducing the development burden.

[0072] Furthermore, the term "common" in the context of multiple first motors and second motors means that at least a portion of their specifications are common. Common specifications can refer to, for example, that at least a portion of the motor's output, speed, or dimensions is the same; it can also mean that they are interchangeable; or it can mean that they are designed identically without affecting the assembly of components other than the motor.

[0073] To illustrate with an example, if the required freezing capacity of the refrigeration system 100 is 5kW, assume that the required output of the first motor used in the coaxial compressor 118 is 45kW, and the required output of the second motor used in the integrated expander compressor 120 is 15kW. Based on this premise, if a refrigeration system 100 with doubled freezing capacity of 10kW is developed, since the amount of refrigerant flowing through the refrigerant path 101 increases exponentially, the required output of the first motor becomes 90kW (=45kW×2), and the required output of the second motor becomes 30kW (=15kW×2). In the refrigeration system 100 of this embodiment, for such requirements, as... Figure 1 As shown, by arranging two coaxial compressors 118, each with a first motor having the same output of 45kW as the basic design specifications, side-by-side with respect to the refrigerant path 101, it is possible to address the issue without designing new coaxial compressors. In this case, in the expander-integrated compressor 120, the second motor 114B, having the same 45kW output specification as the first motor 114A, can provide the required output of 30kW.

[0074] In this way, by using common (same specifications) motors as the first motor 114A and the second motor 114B, the commonality of the peripheral structures of the first motor 114A and the second motor 114B can also be promoted. For example, since the first motor 114A and the second motor 114B are common (same specifications), the output shafts 116A and 116B have the same shaft diameter. As a result, the bearings (radial magnetic bearing 122-1, thrust magnetic bearing 126-1) supporting the output shaft 116A in the coaxial compressor 118 can be common (same specifications) with the bearings (radial magnetic bearing 122-2, thrust magnetic bearing 126-2) supporting the output shaft 116B in the expander-integrated compressor 120. In addition, the motor housing 130-1 of the first motor 114A and the motor housing 130-2 of the second motor 114B can also be common (same specifications).

[0075] Furthermore, the term "common" for these bearings and motor housings means that at least a portion of their specifications are common. Common specifications can mean that they are interchangeable, or that they are designed identically without affecting the assembly of components other than the motor.

[0076] Furthermore, the impeller housing 132-1 for the low-stage compressor and the impeller housing 132-3 for the high-stage compressor of the first motor 114A, and the impeller housing 132-2 for the intermediate compressor and the impeller housing 134-1 for the expander of the second motor 114B can be designed differently according to the shape of the impellers they house.

[0077] In this way, by making the first motor 114A and the second motor 114B included in the compressor unit 102 and their peripheral structures common (of the same specifications), the refrigeration system 100 can be designed efficiently with less development burden even if the required refrigeration capacity of the refrigeration system 100 changes.

[0078] exist Figure 1 The illustration shows a compressor unit 102 comprising two coaxial compressors 118. The two coaxial compressors 118 are arranged side-by-side with respect to a refrigerant path 101. The refrigerant path 101 includes: a first line 144 supplying refrigerant from a cold energy recovery heat exchanger 105 to the compressor unit 102; second lines 146A and 146B branching from the downstream side of the first line 144 relative to the primary compressors 110A of the two coaxial compressors 118; third lines 148A and 148B through which the refrigerant compressed by the two primary compressors 110A flows; and a fourth line 148A and 148B merging downstream and connecting to the intermediate compressor 110B. Pipeline 150; fifth pipeline 152 through which the refrigerant compressed by intermediate compressor 110B flows; sixth pipelines 154A and 154B branching from the downstream side of fifth pipeline 152 to advanced compressors 110C of two coaxial compressors 118 respectively; seventh pipelines 156A and 156B through which the refrigerant compressed by advanced compressor 110C flows respectively; and eighth pipeline 158 where seventh pipelines 156A and 156B merge on the downstream side and connect to the cold energy recovery heat exchanger 105 on the cold box 109 side.

[0079] By one of the second pipelines 146A and 146B (in Figure 1 A first valve 160 is installed on the second pipeline 146B, thereby enabling adjustment of the refrigerant distribution ratio relative to the lower-stage compressor 110A of the two coaxial compressors 118. Additionally, a valve 160 is installed on one of the third pipelines 148A and 148B through which the refrigerant compressed by the two lower-stage compressors 110A flows (in... Figure 1 The third pipeline 148B is equipped with a second valve 162, thereby enabling the adjustment of the refrigerant discharge ratio from the two low-stage compressors 110A.

[0080] In addition, the aforementioned heat exchanger 112A is installed on the third pipelines 148A and 148B respectively.

[0081] Through one of the seventh pipelines 156A and 156B ( Figure 1 The seventh pipeline 156B is equipped with a third valve 164, thereby enabling the adjustment of the refrigerant discharge ratio from the advanced compressor 110C of the two coaxial compressors 118.

[0082] In addition, the aforementioned heat exchangers 112C are respectively installed in the seventh pipelines 156A and 156B.

[0083] Additionally, the refrigeration system 100 includes a first bypass line 166 connecting the upstream and downstream sides of the lower-stage compressor 110A of the two coaxial compressors 118. A first bypass valve 168 is installed on the first bypass line 166. A second bypass line 170 connecting the upstream and downstream sides of the intermediate-stage compressor 110B is also provided. A second bypass valve 172 is installed on the second bypass line 170. Furthermore, a third bypass line 174 connecting the upstream and downstream sides of the higher-stage compressor 110C of the two coaxial compressors 118 is provided. A third bypass valve 176 is installed on the third bypass line 174.

[0084] Additionally, a fourth bypass line 182 is provided to connect the high-pressure refrigerant line 178 and the low-pressure refrigerant line 180 in the refrigerant path 101. The high-pressure refrigerant line 178 is located downstream of the advanced compressor 110C and between it and the cold energy recovery heat exchanger 105, while the low-pressure refrigerant line 180 is located between the cold energy recovery heat exchanger 105 and the low-pressure compressor 110A. A buffer tank 184 for storing refrigerant and a fourth valve 186 and a fifth valve 188 are respectively located upstream and downstream of the buffer tank 184.

[0085] These valves are configured to control their opening degree based on control signals from a control device 200, which is a control unit of the refrigeration system 100, thereby enabling appropriate switching of the refrigerant flow path in the refrigerant path 101. The control device 200 is configured, for example, by installing a program for executing the prescribed control onto a hardware structure consisting of an electronic computing device such as a computer.

[0086] Furthermore, the configuration of each valve and bypass valve in the aforementioned refrigeration system 100 can be appropriately modified within the range that the same control can be achieved.

[0087] The starting method of the refrigeration system 100 with the above structure will be described next. Figure 4 It means Figure 1 A flowchart of the startup method for the refrigeration system 100.

[0088] First, assuming the refrigeration system 100 is in its initial state, the refrigerant temperature at the inlet of the expander 103 is at room temperature (approximately 300K). In the refrigeration system 100 in a stopped state, the temperature of the refrigerant remaining in the refrigerant path 101 rises to near room temperature (approximately 300K), thereby increasing the refrigerant pressure within the refrigerant path 101. In this state, the refrigerant pressures in the high-pressure refrigerant line 178 from the high-level compressor 110C to the expander 103 and the low-pressure refrigerant line 180 from the expander 103 to the low-level compressor 110A in the refrigerant path 101 are balanced (high and low pressure equilibrium). In this state, the pressure on the low-pressure refrigerant line 180 is higher than during normal operation. When the refrigeration system 100 is started and operated under this high refrigerant pressure, the pressure on the high-pressure refrigerant line 178 is prone to rise excessively, especially since the expander-integrated compressor 120 is configured with a motor drive, potentially increasing the motor load.

[0089] Therefore, when the pressure difference ΔP between the pressure in the high-pressure refrigerant line 178 and the pressure inside the buffer tank 184 exceeds a predetermined threshold ΔP1 (e.g., 10 kPa) (step S1: Yes), the control device 200 controls the fourth valve 186 to open (step S2), recovering a portion of the refrigerant flowing through the refrigerant path 101 back to the buffer tank 184 (step S3). This reduces the pressure difference ΔP, preventing excessive pressure rise in the high-pressure refrigerant line 178, and consequently, appropriately avoiding excessive motor load. Subsequently, when the pressure difference ΔP falls below the threshold ΔP1 (step S4: Yes), the control device 200 controls the fourth valve 186 to close (step S5).

[0090] Furthermore, if the pressure difference ΔP is greater than the threshold ΔP1 (step S4: no), the control device 200 returns the control to step S2.

[0091] Furthermore, the pressure difference ΔP can be obtained, for example, by the difference between the detection values ​​of the pressure sensor installed in the high-pressure refrigerant line 178 and the pressure sensor installed in the buffer tank 184.

[0092] In the refrigerant path 101, the flow path near the inlet of the expander 103, which has the highest density under rated operating conditions, has a minimum profile. During precooling, because the suction temperature of the expander 103 is higher than the rated condition (lower refrigerant density), compressor surge may occur due to choking of the expander 103 at this location due to reduced refrigerant flow. In the next step S6, to address this issue, only one of the two coaxial compressors 118 included in the compressor unit 102 (coaxial compressor 118A) is started together with the integrated expander compressor 120 (i.e., only one of the two coaxial compressors 118 is operated together with the integrated expander compressor 120, initiating so-called control number operation). This allows for startup with reduced refrigerant flow in the expander 103, thus effectively preventing compressor surge.

[0093] Next, the control device 200 determines the temperature T of the refrigerant at the inlet of the expander 103. in The opening degree of the second bypass valve 172 is controlled (step S7). In step S7, the opening degree is determined based on the refrigerant temperature T at the inlet of the expander 103. in By controlling the opening of the second bypass valve 172, a portion of the refrigerant flowing through the refrigerant path 101 bypasses the intermediate compressor 110B via the second bypass line 170. As a result, the flow rate of refrigerant supplied to the intermediate compressor 110B increases, which can more effectively prevent surge in the compressor as described above.

[0094] Additionally, the opening degree control of the second bypass valve 172 in step S7 can be based on the refrigerant temperature T at the inlet of the expander 103. in The process can be carried out continuously or in stages (steps). In this case, the speed of at least one of the coaxial compressor 118 or the integrated expander compressor 120 that is started in step S6 can be coordinated and controlled in such a way that the cooling rate of the refrigerant in the cold energy recovery heat exchanger 105 is approximately constant (e.g., 60 K / h).

[0095] In addition, the temperature T of the refrigerant at the inlet of the expander 103 in Temperature can be obtained through a temperature sensor (not shown) located at the inlet of the expander 103.

[0096] In addition, in step S7, the first valve 160, the second valve 162, the third valve 164, the first bypass valve 168, and the third bypass valve 176 are controlled to be closed.

[0097] Next, when the temperature T at the inlet of expander 103... inWhen the value becomes below the first target value T1 (e.g., 180-200K) (step S8: Yes), the control device 200 controls the first bypass valve 168, the third bypass valve 176 and the first valve 160 to open (step S9).

[0098] Next, the control device 200 determines whether surge exists (step S10). If surge exists (step S10: Yes), it controls the operation by reducing the speed of the coaxial compressor 118A that was started in step S6 (step S11). In step S11, the speed of the coaxial compressor 118A that was controlled is reduced to a level where surge does not occur in either compressor, assuming both coaxial compressors 118 in the compressor unit 102 are started.

[0099] Furthermore, reducing the speed of one of the coaxial compressors 118A in step S11 can also result in it being temporarily stopped. Additionally, if it is determined that there is no surge (step S10: No), the speed reduction control in step S11 is not implemented. For example, since surge is less likely to occur at lower speeds (e.g., when the speed is lower during pre-cooling due to limitations such as the cooling rate of the heat exchanger), speed reduction control as in step S11 may not be necessary depending on the operating conditions.

[0100] Next, the control device 200 controls the first bypass valve 168 and the third bypass valve 176 to open (step S12), starting the other coaxial compressor 118B included in the compressor unit 102 (step S13). At this time, the speed of the other coaxial compressor 118B is controlled to be equal to that of the coaxial compressor 118A whose speed was reduced in step S6. Moreover, when the pressure conditions of the two coaxial compressors 118 become equal (step S14: Yes), the control device controls the first bypass valve 168 and the third bypass valve 176 to close (step S15).

[0101] Next, the control device 200 opens the second valve 162 and the third valve 164 to complete the connection of the other coaxial compressor 118B with respect to the refrigerant path 101 (step S16). In this way, while the speed of the coaxial compressor 118A, which was started first in step S3, is temporarily reduced, starting the other coaxial compressor 118B can prevent surge in each compressor and smoothly transition from single-sided operation based on one coaxial compressor 118A to dual-sided operation based on two coaxial compressors 118A and 118B.

[0102] The control device 200 then bases its control on the temperature T of the refrigerant at the inlet of the expander 103. inThe cooling rate of the refrigerant in the cold energy recovery heat exchanger 105 controls the opening of the second bypass valve 172 and the rotational speed of at least one of the coaxial compressor 118 or the integrated expander compressor 120, simultaneously promoting pre-cooling operation. Furthermore, when the temperature T at the inlet of the expander 103... in When the temperature drops below the second target temperature T2 (e.g., 100-120K) (step S17: Yes), the control device 200 controls the second bypass valve 172 to close (step S18), completing the pre-cooling and transitioning to normal operation, thereby ending the start-up control of the series of refrigeration systems 100 (step S19).

[0103] Furthermore, when the refrigeration system 100 has three or more coaxial compressors 118, the control described above is applied by sequentially increasing the number of coaxial compressors 118 that are in operation, thereby enabling the temperature T to be controlled. in It becomes the desired value.

[0104] As described above, in the startup method of the refrigeration system 100, during the initial startup phase, the coaxial compressor 118, a portion of the compressor unit 102, is started, and the system is controlled to operate as precooling progresses (as the temperature T at the inlet of the expander 103 increases). in The number of coaxial compressors 118 in operation can be increased by reducing the temperature (T) at the inlet of expander 103. The number of coaxial compressors 118 in operation at each stage can be determined, for example, by adjusting the temperature T at the inlet of expander 103. in Control is performed in the following manner.

[0105] Based on the relationship between the speed of sound, Mach number, and adiabatic flow, the mass flow rate G of the refrigerant through the expander 103 is expressed as follows: G is represented by the temperature T of the refrigerant at the inlet of the expander 103. in The function of (here, it is assumed that the refrigerant passing through the expander 103 is not in a critical state, that is, the nozzle outlet velocity of the expander 103 does not reach the speed of sound, and the refrigerant is an ideal gas)

[0106] [Formula 1]

[0107]

[0108] Here, A represents the nozzle throat area of ​​expander 103, and P... in P ex Let κ be the pressure at the inlet and outlet of expander 103, respectively, κ be the specific heat ratio of the refrigerant, and R be the gas constant of an ideal gas. Using equation (1), the temperature T at the inlet of expander 103 can be estimated. in The refrigerant flow rate G. Therefore, if the discharge flow rate of each coaxial compressor 118 is R, the number D of coaxial compressors 118 that should be started can be obtained by the following formula (rounding up).

[0109] D = G / R (2)

[0110] like Figure 1 As shown, when the compressor unit 102 includes two coaxial compressors 118, the temperature T at the inlet of the expander 103 is... in Before reaching the first target value T1 (e.g., 180–200 K), precooling can be efficiently performed by starting only one coaxial compressor 118. However, efficiency decreases at the second target value T2 (e.g., 120–200 K), so it is preferable to start the other coaxial compressor 118 and operate both units. By changing the number of coaxial compressors 118 operating according to the temperature range, under operating conditions where surge may occur, as described above, by temporarily reducing the speed of the already started coaxial compressor 1, surge can be prevented and the transition in the number of operating units can be smooth.

[0111] In the above embodiment, although a refrigeration system 100 with two coaxial compressors 118 relative to one integrated expander compressor has been described, the number of integrated expander compressors 120 and coaxial compressors 118 in the refrigeration system 100 can be any number. Hereinafter, some variations of the refrigeration system 100 will be specifically described with reference to FIGS. 5 to 8.

[0112] Furthermore, Figures 5 to 8 extract and simply show the coaxial compressor 118, the expander integrated compressor 120, the first motor 114A, and the second motor 114B in the refrigeration system 100. Other structures are omitted in detail because they are similar to the structures described in the above embodiment.

[0113] Figures 5A-5B This is a schematic diagram showing refrigeration systems 100A-1 to 100A-2 equipped with two coaxial compressors 118A and 118B, and one integrated expander compressor 120. Figure 5A In the refrigeration system 100A-1 shown, similarly to the aforementioned embodiment, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, and the second motor 114B for driving the expander-integrated compressor 120 are all common. In this case, by making both the first motor 114A and the second motor 114B common, the types of motors used in the refrigeration system 100A can be minimized, effectively reducing the development costs and time required.

[0114] exist Figure 5BIn the refrigeration system 100A-2 shown, the first motor 114A-1 used to drive the coaxial compressor 118A and the second motor 114B used to drive the integrated expander compressor 120 are common. On the other hand, the first motor 114A-2 used to drive the coaxial compressor 118B is different (it is of a different specification). In this way, while vigorously promoting the commonality of the first motor 114A and the second motor 114B used in the refrigeration system 100, it is also possible to flexibly meet the specifications required by the refrigeration system 100 by making only a portion of the motors of a different specification.

[0115] then, Figures 6A-6C This is a schematic diagram showing refrigeration systems 100B-1 to 100B-3 equipped with three coaxial compressors 118A, 118B, and 118C, and one integrated expander compressor 120. Figure 6A In the refrigeration system 100B-1 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the first motor 114A-3 for driving the coaxial compressor 118C, and the second motor 114B for driving the integrated expander compressor 120 are all common. In this case, by making all the first motors 114A and the second motor 114B common, the types of motors used in the refrigeration system 100A can be minimized, effectively reducing the cost and time required for development.

[0116] exist Figure 6B In the refrigeration system 100B-2 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, and the second motor 114B for driving the integrated expander compressor 120 are common. On the other hand, the first motor 114A-3 for driving the coaxial compressor 118C is different (it is of a different specification). In this way, while vigorously promoting the commonality of the first motor 114A and the second motor 114B used in the refrigeration system 100, it is also possible to flexibly meet the specifications required by the refrigeration system 100 by making only some of the motors of a different specification.

[0117] exist Figure 6C In the refrigeration system 100B-3 shown, the first motor 114A-1 for driving the coaxial compressor 118A and the second motor 114B for driving the integrated expander compressor 120 are common to each other. On the other hand, the first motor 114A-2 for driving the coaxial compressor 118B and the first motor 114A-3 for driving the coaxial compressor 118C are common to each other. In this way, even if the various motors used in the refrigeration system 100 are made common for different specifications, the system can flexibly meet the specifications required by the refrigeration system 100.

[0118] then, Figures 7A-7C This is a schematic diagram showing refrigeration systems 100C-1 to 100C-3 equipped with three coaxial compressors 118A, 118B, and 118C, and two integrated expander compressors 120A and 120B. Figure 7A In the refrigeration system 100C-1 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the first motor 114A-3 for driving the coaxial compressor 118C, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are all common. In this case, by making the first motor 114A and the second motor 114B common, the types of motors used in the refrigeration system 100A can be minimized, effectively reducing the development costs and time required.

[0119] exist Figure 7B In the refrigeration system 100C-2 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are common. On the other hand, the first motor 114A-3 for driving the coaxial compressor 118C is different (it is of a different specification). In this way, while vigorously promoting the commonality of the first motor 114A and the second motor 114B used in the refrigeration system 100, it is also possible to flexibly meet the specifications required by the refrigeration system 100 by making only some of the motors of a different specification.

[0120] exist Figure 7C In the refrigeration system 100C-3 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are shared. On the other hand, the first motor 114A-2 for driving the coaxial compressor 118B is shared with the first motor 114A-3 for driving the coaxial compressor 118C. In this way, even if the various motors used in the refrigeration system 100 are made common for different specifications, the system can flexibly meet the specifications required by the refrigeration system 100.

[0121] Figures 8A-8DThis is a schematic diagram showing refrigeration systems 100D-1 to 100D-4 equipped with four coaxial compressors 118A, 118B, 118C, and 118D, and two integrated expander compressors 120A and 120B. Figure 8A In the refrigeration system 100D-1 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the first motor 114A-3 for driving the coaxial compressor 118C, the first motor 114A-4 for driving the coaxial compressor 118D, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are all common. In this case, by making the first motor 114A and the second motor 114B all common, the types of motors used in the refrigeration system 100A can be minimized, effectively reducing the development costs and time required.

[0122] exist Figure 8B In the refrigeration system 100D-2 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the first motor 114A-3 for driving the coaxial compressor 118C, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are common. On the other hand, the first motor 114A-4 for driving the coaxial compressor 118D is different (it is of a different specification). In this way, while vigorously promoting the commonality of the first motor 114A and the second motor 114B used in the refrigeration system 100, it is also possible to flexibly meet the specifications required by the refrigeration system 100 by making only some of the motors of a different specification.

[0123] exist Figure 8C In the refrigeration system 100D-3 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the first motor 114A-2 for driving the coaxial compressor 118B, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are shared. On the other hand, the first motor 114A-3 for driving the coaxial compressor 118C and the first motor 114A-4 for driving the coaxial compressor 118D are shared. In this way, even if the various motors used in the refrigeration system 100 are made common for different specifications, the system can flexibly meet the specifications required by the refrigeration system 100.

[0124] exist Figure 8DIn the refrigeration system 100D-4 shown, the first motor 114A-1 for driving the coaxial compressor 118A, the second motor 114B-1 for driving the integrated expander compressor 120A, and the second motor 114B-2 for driving the integrated expander compressor 120B are common to each other. On the other hand, the first motor 114A-2 for driving the coaxial compressor 118B, the first motor 114A-3 for driving the coaxial compressor 118C, and the first motor 114A-4 for driving the coaxial compressor 118D are common to each other. In this way, even if the various motors used in the refrigeration system 100 are made common for multiple different specifications, the system can flexibly meet the specifications required by the refrigeration system 100.

[0125] The content described in the above embodiments can be understood, for example, in the following manner.

[0126] (1) One type of refrigeration system is

[0127] A refrigeration system (e.g., the refrigeration system 100 of the above embodiment) utilizes a Brayton cycle, which uses a refrigerant to generate cold energy, the refrigerant being compressed by a compressor unit (e.g., compressor unit 102 of the above embodiment) disposed on a refrigerant path (e.g., refrigerant path 101 of the above embodiment).

[0128] The compressor unit includes:

[0129] Multiple compressors (e.g., multiple coaxial compressors 118 in the above embodiment) are arranged side by side with respect to the refrigerant path;

[0130] Multiple first motors (e.g., multiple first motors 114A in the above embodiment) are used to drive the multiple compressors respectively;

[0131] An integrated expander compressor (e.g., the integrated expander compressor 120 of the above embodiment) is integrally configured with an expander (e.g., the expander 103 of the above embodiment) capable of expanding the refrigerant compressed by the compressor unit; and

[0132] A second motor (such as the second motor 114B in the above embodiment) is used to drive the integrated expander compressor.

[0133] The number of compressors is greater than that of the integrated expander compressor.

[0134] According to the above (1), when developing refrigeration systems with different freezing capacities, it is also possible to cope with the situation by changing the number of compressors that are part of the compressor unit structure, thus effectively suppressing the increase in the number of components and the area occupied by the design change.

[0135] (2) In another manner, in the manner described in (1) above,

[0136] The plurality of first motors and the second motor are common.

[0137] According to the method described in (2) above, the multiple first motors used to drive the multiple compressors included in the compressor unit are shared with the second motor used to drive the integrated expander compressor. This reduces the number of types of motors used in the refrigeration system, effectively reducing development costs and time.

[0138] Furthermore, in this specification, "common" in the context of multiple first motors and second motors means that multiple first motors and second motors are separate motors, and that at least some of their specifications are common. Common specifications can mean, for example, that at least some of the motor's output, speed, or dimensions are the same; it can also mean that they are interchangeable; or it can mean that their designs are identical without affecting the assembly of components other than the motor.

[0139] (3) In another manner, in the manner described in (1) or (2) above,

[0140] It includes a control device for controlling the plurality of compressors (e.g., the control device 200 described in the above embodiment).

[0141] When the refrigeration system is started, the control device controls the multiple compressors in a manner that causes a portion of the multiple compressors to operate, based on the temperature of the refrigerant at the inlet of the expander.

[0142] According to the above (3), by running a portion of multiple compressors when the refrigeration system is started, surge in the coaxial compressor can be effectively prevented.

[0143] (4) In another manner, in the manner described in (3) above,

[0144] The control device controls the compressor by reducing its rotational speed when it is in the start-up state, and then controls it by changing the number of compressors in operation.

[0145] According to the above (4), when the number of compressors to be started varies, by reducing the speed of the compressors that are started first, surge in each compressor can be prevented and the number of compressors to be started can be changed smoothly.

[0146] (5) In another manner, in any of the schemes (1) to (4) above,

[0147] The refrigerant path includes: a bypass line (e.g., the second bypass line 170 in the above embodiment), configured to bypass the upstream and downstream sides of the compressor (e.g., the intermediate compressor 110B in the above embodiment) of the integrated expander compressor; and

[0148] A bypass valve (such as the second bypass valve 172 in the above embodiment) is provided on the bypass line.

[0149] According to the above (5), by adjusting the opening of the bypass valve set in the bypass pipeline, surge in each compressor can be effectively prevented.

[0150] (6) In another manner, in the manner described in (5) above,

[0151] The bypass valve is controlled based on the temperature of the refrigerant at the inlet of the expander, such that the flow rate of the refrigerant in the compressor of the integrated compressor on the expander side is above a predetermined value.

[0152] According to the above (6), in the event that surge may occur due to the temperature rise of the refrigerant at the inlet of the expander, the opening of the bypass valve is controlled to prevent surge by ensuring that the refrigerant flow rate in the compressor of the integrated expander compressor is above a specified value.

[0153] (7) In another manner, in the manner described in (6) above,

[0154] The rotational speed of the compressor or the integrated expander compressor and the opening degree of the bypass valve are coordinated and controlled in such a way that the cooling rate of the refrigerant becomes approximately constant.

[0155] According to the method described in (7) above, by coordinating the control of the compressor or the speed of the integrated compressor with the control of the bypass valve opening, the cooling rate of the refrigerant flowing through the refrigerant path is kept approximately constant. Therefore, during the pre-cooling period from startup to normal operation, the cooling rate can be adjusted / corrected, and the refrigerant temperature can be controlled with high precision.

[0156] (8) In another manner, in any of the schemes (1) to (7) above,

[0157] The plurality of compressors are coaxial compressors (e.g., coaxial compressor 118 in the above embodiment) that include a plurality of compressors connected in series with respect to the refrigerant path.

[0158] According to the above (8), by using a coaxial compressor (multi-stage compressor) as multiple compressors, a larger compression ratio than that of a single-stage compressor can be obtained, and high efficiency can be achieved.

[0159] Explanation of reference numerals in the attached figures

[0160] 100 refrigeration system

[0161] 101 Refrigerant Path

[0162] 102 compressor unit (110A, 110B, 110C)

[0163] 103 Expander

[0164] 104 Cooling Section

[0165] 105 Cold Energy Recovery Heat Exchanger

[0166] 106 Superconducting Device

[0167] 107 Refrigerant Path

[0168] 108 pump

[0169] 109 Cold Box

[0170] 110 compressor

[0171] 110A Low-grade compressor

[0172] 110B Intermediate Compressor

[0173] 110C Advanced Compressor

[0174] 112 (112A, 112B, 112C) heat exchangers

[0175] 114A First Motor

[0176] 114B Second Motor

[0177] 116A and 116B output shafts

[0178] 118 (118A, 118B) coaxial compressor

[0179] 120 Expander Integrated Compressor

[0180] 122-1, 122-2 radial magnetic bearings

[0181] 126 thrust magnetic bearing

[0182] 127-1 and 127-2 Axial Turntables

[0183] 128 housing

[0184] 130 Motor Housing

[0185] 132-1 Impeller housing for low-grade compressors

[0186] 132-2 Impeller housing for intermediate compressors

[0187] 132-3 Impeller housing for advanced compressors

[0188] 134-1 Impeller casing for expander

[0189] 136A and 136B rotors

[0190] 138A and 138B stators

[0191] Impellers 140A, 140B, 140C, and 142

[0192] 144 First Pipeline

[0193] 146A, 146B Second Pipeline

[0194] 148A, 148B Third Pipeline

[0195] 150 Fourth Pipeline

[0196] 152 Fifth Pipeline

[0197] Pipelines 154A and 154B (Sixth Pipeline)

[0198] Pipelines 156A and 156B (Seventh Pipeline)

[0199] 158 Eighth Pipeline

[0200] 160 First Valve

[0201] 162 Second Valve

[0202] 164 Third Valve

[0203] 166 First bypass pipeline

[0204] 168 First bypass valve

[0205] 170 Second bypass pipeline

[0206] 172 Second bypass valve

[0207] 174 Third Bypass Pipeline

[0208] 176 Third bypass valve

[0209] 178 High-pressure refrigerant line

[0210] 180 Low-pressure refrigerant line

[0211] 182 Fourth Bypass Pipeline

[0212] 184 Buffer Tank

[0213] 186 Fourth Valve

[0214] 188 Fifth Valve

[0215] 200 Control device.

Claims

1. A refrigeration system utilizing a Brayton cycle, wherein the Brayton cycle uses a refrigerant to generate cold energy, the refrigerant being compressed by a compressor unit disposed in the refrigerant path. The compressor unit includes: Multiple coaxial compressors are arranged side by side with respect to the refrigerant path, and each includes multiple compressors connected in series with respect to the refrigerant path; Multiple first motors, which are used to drive the multiple coaxial compressors respectively; An integrated expander compressor, which is integrally formed with an expander capable of expanding the refrigerant compressed by the compressor unit; The second motor is used to drive the integrated expander compressor; as well as A control device for controlling the multiple coaxial compressors. The multiple coaxial compressors have a greater number of units than the integrated expander compressor. When the refrigeration system is started, the control device controls the multiple coaxial compressors in a manner that causes a portion of the multiple coaxial compressors to operate, based on the temperature of the refrigerant at the inlet of the expander.

2. The refrigeration system according to claim 1, characterized in that, The plurality of first motors and the second motor are common.

3. The refrigeration system according to claim 1, characterized in that, The control device controls the compressor by reducing its rotational speed when it is in the start-up state, and then controls it by changing the number of coaxial compressors in operation.

4. The refrigeration system according to claim 1 or 2, characterized in that, The refrigerant path includes: a bypass line configured to bypass the upstream and downstream sides of the compressor in the integrated expander compressor; and A bypass valve is installed on the bypass line.

5. The refrigeration system according to claim 4, characterized in that, The bypass valve, based on the temperature of the refrigerant at the inlet of the expander, ensures that the flow rate of the refrigerant in the compressor of the integrated expander compressor is above a specified value.

6. The refrigeration system according to claim 5, characterized in that, The rotational speed of the compressor or the integrated expander compressor and the opening degree of the bypass valve are coordinated and controlled in such a way that the cooling rate of the refrigerant becomes approximately constant.

7. The refrigeration system according to claim 1 or 2, characterized in that, The plurality of first motors and the second motor each comprise: Output shafts with the same shaft diameter; Bearings that support the output shaft and are of the same specification; and Motor housings of the same specifications.

8. The refrigeration system according to claim 7, characterized in that, The multiple coaxial compressors and the integrated expander compressor each comprise: Compressor impellers with different shapes; and Impeller housings for compressors with different specifications.

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