Method for cooling a multi-stage, in particular two-stage centrifugal compressor, and a multi-stage, in particular two-stage centrifugal compressor for performing the method
Patent Information
- Application Number
- PCT/IB2026/052757
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-24
- Filing Date
- 2026-03-23
- Publication Date
- 2026-10-01
Smart Images
Figure IB2026052757_01102026_PF_FP_ABST
Abstract
Description
[0001] Method for cooling a multi-stage, in particular two-stage centrifugal compressor, and a multi-stage, in particular two-stage centrifugal compressor for performing the method
[0002] Technical field
[0003] The invention relates to a method for cooling a multi-stage centrifugal compressor comprising in each stage a radial impeller mounted on a common shaft, in the central part of which a motor rotor is mounted, surrounded by a motor stator, which is mounted in the compressor housing, the shaft being mounted in radial gas dynamic bearings arranged on both sides of the motor rotor and in a double-sided axial gas dynamic bearing.
[0004] The invention also relates to a method for cooling a two-stage centrifugal compressor comprising two radial impellers mounted on a common shaft, in the central part of which is mounted a rotor of an electric motor surrounded by a stator, which is mounted in the compressor housing, wherein between the impeller of the first stage of the compressor and the electric motor, the shaft is mounted in a first radial gas dynamic bearing, and between the impeller of the second stage of the compressor and the electric motor, the shaft is mounted in a second radial gas dynamic bearing and in a double-sided axial gas dynamic bearing, wherein the outlet of the first compressor stage is connected to the inlet of the second compressor stage.
[0005] In addition, the invention relates to a multi-stage and / or two-stage centrifugal compressor for performing these methods.
[0006]
[0007] art
[0008] Refrigeration compressors are used to circulate refrigerant in a refrigeration system, which includes at least a compressor, a condenser, an evaporator, and an expansion device.
[0009] For example, US 11 486618 B2 discloses a two-stage compressor, the compression stages of which are provided with impellers which are mounted atopposite ends of a shaft on which the motor rotor is mounted, rotating around an axis common to these components. The refrigerant from the evaporator enters the first compression stage of the refrigerant loop, where it is compressed, and exits the first compression stage and enters a hollow connector, via which it travels to the inlet of the second compression stage, where it is further compressed, and the main refrigerant loop is connected to the outlet of the second compression stage so that the gas flows into its condenser. The connector provides a smooth channel for the gas to flow from the first compression stage to the second compression stage. The shaft 31 is rotatably supported by magnetic bearings or by other bearings, such as gas bearings including static and dynamic gas bearings like foil bearings or rigid grooved bearings, wherein the specific construction of the bearings is not described. The connector provides a smooth transition for the refrigerant gas from the outlet of the first compression stage to the inlet of the second compression stage so as to improve the aerodynamic performance of the refrigerant gas flow.
[0010] The disadvantage of using magnetic bearings is that they require additional energy costs, which reduces the efficiency of the refrigerant loop in proportion to the amount of energy spent on the magnetic bearings. Magnetic bearings are very sensitive to sudden changes in current, for example, pulses or surges, therefore, when the parameters change suddenly, the rotor may not be able to maintain the position and a crash will occur.
[0011] In addition, when using magnetic bearings, it is necessary to additionally use rolling bearings as a backup, especially when starting and stopping the compressor, which requires extending the rotor, thereby increasing the complexity of the construction.
[0012] When using bypass channels according to this solution, the system can only operate in a single-parameter mode. In other modes, there will be different inflow angles, which will lead to the formation of vortices in the channel and, consequently, to an increase in hydraulic resistance, which in turn will lead to a decrease in compressor efficiency.US 2018038380 discloses a two-stage centrifugal compressor comprising a casing which houses a motor the rotor of which is arranged on a shaft, at the ends of which impellers of the first and second stages of the compressor are mounted. In the first stage of the compressor, the casing includes a first inlet portion and a first outlet portion, which guide the refrigerant towards and away from the impeller of the first stage. A transfer pipe is connected to the outlet portion of the first stage, through which the refrigerant is fed to the inlet portion of the second stage of the compressor, in which it is further compressed, and its outlet portion is led to the main refrigerant circuit. The shaft of the centrifugal compressor is mounted on a magnetic bearing, which is fixedly mounted in the compressor casing. The magnetic bearing assembly includes a first radial magnetic bearing, a second radial magnetic bearing and an axial magnetic bearing. The magnetic bearing allows at least some relative axial movement between the magnetic bearing and the shaft, which is used in the elongation and contraction of the shaft due to temperature changes.
[0013] The disadvantages of magnetic bearings according to this solution are the same as in the previous solution.
[0014] Principle of the invention
[0015] The principle of the invention is a method for cooling a multi-stage centrifugal compressor according to claim 1 and especially this method applied to cooling a two-stage centrifugal compressor, in which the refrigerant in a liquid state is directed around the outer surface of the stator of the electric motor, thereby cooling the stator and heating up until it changes into a gaseous state, and this gaseous refrigerant is used to cool the rotor and the interior of the stator of the electric motor and to cool the second radial gas dynamic bearing and the double-sided axial gas dynamic bearing, these bearings being simultaneously cooled by the refrigerant from the second spiral chamber and the first radial gas dynamic bearing being cooled by the refrigerant from a first spiral chamber. Supplying the liquid refrigerant in the first stage of cooling increases the cooling effect, reduces the energy consumption for cooling and reduces the cooling surface area.The principle of the multi-stage centrifugal compressor for performing the above-described method is described in claim 3, and the principle of the two-stage centrifugal compressor for performing the method according to claim 2 consists in that a cooling spiral groove is formed around the outer surface of the stator in the compressor housing, the inlet of which is connected to a condenser arranged downstream of the outlet of the second compressor stage, from which the refrigerant in a liquid state is supplied to the spiral groove to cool the stator. As it passes through the spiral groove, the refrigerant evaporates and the gaseous refrigerant enters the main cooling system, which terminates in an annular gap, downstream of which it is divided into the cooling system of the interior of the electric motor and the cooling system of the bearings of the second compressor stage, wherein both of these systems open into the gap between the internal surface of the stator and the casing of the rotor of the electric motor. An outlet channel connected to the first compressor stage is attached to the end of this gap, wherein the cooling system of the second stage bearings is connected to the second spiral chamber, and the cooling space of the first radial gas dynamic bearing is connected to the first spiral chamber.
[0016] Preferred embodiments of the two-stage centrifugal compressor according to the invention are described in the dependent claims, and a person skilled in the art is able to apply them to the cooling of multi-stage centrifugal compressors as well.
[0017] Brief description of drawings
[0018] The invention will be described with reference to the enclosed drawings, wherein Fig. 1 is an exemplary diagram of a cooling system with a two-stage compressor, Fig. 2 is an exemplary diagram of the cooling system with the two-stage compressor and an economizer I heat / cold exchanger, Fig. 3 is a diagram of the bearings of the two-stage compressor, Fig. 4 is a diagram of the cooling of the stator of the electric motor of the compressor, Fig. 5a is an exemplary embodiment of the two-stage compressor in section, Fig. 5 is an exemplary embodiment of the compressor in section with the flow of the refrigerant through the cooled parts of the compressor, Fig. 6a is a radial gas dynamic foil bearing in side view, Fig. 6b is a radial gas dynamic foil bearing in axonometric view, Fig.7a is a side view of the housing with a radial gas dynamic graphite bearing, Fig.
[0019] 7b is a detailed view of the graphite bearing according to Fig. 7a, Fig. 7c is a cross-section of the graphite bearing according to Fig. 7a, Fig. 8 is a cross-section of a double-sided axial gas dynamic bearing, Fig. 9 is a view of the front surface of a disk of the double-sided axial gas dynamic bearing, Fig. 10 is a view of a friction ring of a foil double-sided axial gas dynamic bearing, Fig. 1a is addition of the first compressor stage with an additional radial impeller, Fig. 1b is addition of the second compressor stage with an additional radial impeller and Fig. 1c is addition of both compressor stages with additional radial impellers
[0020] Examples of embodiment
[0021] The invention will be explained with reference to the below description of a two-stager centrifugal compressor shown in Figs. 1 to 9.
[0022] Fig. 1 shows an exemplary diagram of a cooling system with a two-stage compressor 1 arranged in a refrigerant circuit 2. The compressor 1 comprises a first compressor stage 11 and a second compressor stage 12, between which an electric motor 14 is mounted on a common shaft 13. The axis of the shaft 13 also forms the axis of the compressor 1.
[0023] The outlet 21 of the refrigerant circuit 2 is connected to the inlet 111 of the first compressor stage 11. The outlet 112 of the first compressor stage 11 is connected via a pipe 15 to the inlet 121 of the second compressor stage 12, to whose outlet 122 is connected the inlet 22 of the refrigerant circuit 2, in which a condenser 3, a control valve 4, and an evaporator 5 are arranged in series one after the other. The condenser 3 and the evaporator 5 are of known construction and are used in the refrigerant circuit 2 in a known manner.
[0024] The two-stage compressor 1 according to the invention may be used also in other cooling systems, for example in the cooling system according to Fig. 2, the basic part of which is configured in the same way as the previous embodiment according to Fig. 1 , but in the direction of flow, between the condenser 3 and the control valve 4, an economizer (heat exchanger) 6 is inserted, to which a control valve 7 of the flow through the economizer 6 is assigned. The economizer 6 is provided with an auxiliary outlet 61, which is connected by a pipe 610 to aconnection 150, which is part of a pipe 15, which comes from the outlet 112 of the first compressor stage and opens into the inlet 121 of the second compressor stage 12.
[0025] As shown in Fig. 3, the shaft 13 between the first compressor stage 11 and the electric motor 14 is mounted in a first radial gas dynamic bearing 16, and between the electric motor 14 and the second compressor stage 12, it is mounted in a second radial gas dynamic bearing 17, wherein the axial clearances of the entire shaft 13 assembly of the electric motor 14 and the first and second stages of the compressor 1 are limited by a double-sided axial gas dynamic bearing 18, which is mounted on the shaft 13 between the second radial gas dynamic bearing 17 and the electric motor 14. With respect to the construction of the compressor, it is clear to the skilled person that the axial gas dynamic bearing 18 can also be mounted between the first radial gas dynamic bearing 16 and the electric motor 14.
[0026] The cooling of the stator of the electric motor of the compressor is schematically shown in Fig. 4, from which it is clear that a spiral cooling groove 81 is formed around the circumference of the stator in the compressor housing, into which the refrigerant in a liquid state is supplied from a suitable point of the cooling circuit, not shown in more detail here. When passing through the groove 81 around the circumference of the stator, the refrigerant heats up, evaporates and returns in a gaseous state to the first stage 11 of the compressor. The specific embodiment of the cooling of the stator and other components of the compressor will be described below.
[0027] In the embodiment according to Fig. 5a, in which the structure of the compressor 1 is shown in more detail, the axial gas dynamic bearing 18 is mounted on the shaft 13 between the second radial gas dynamic bearing 17 and the electric motor 14. In this embodiment, the outlet of the refrigerant circuit 2 is connected to the inlet 111 of the first compressor stage 11 in a known manner, not shown in Fig. 5a, wherein the inlet channel arranged downstream of the inlet 111 comprises a confusor 1110, in which inlet controlled blades 1111 (AGV) are arranged for regulating the amount of the refrigerant entering a first radial impeller 110 of the first compressor stage 11, the first radial impeller 110 being mounted on the shaft 13.A first spiral chamber 1101 is assigned to the first radial impeller 110. The first spiral chamber 1101 opens into the outlet 112 of the first compressor stage 11, Connected to the outlet 112 of the first compressor stage 11 is the pipe 15, which opens into the inlet 121 of the second compressor stage 12. The inlet 121 of the second compressor stage 12 also includes a confusor, which opens out against the second radial impeller 120, to which is assigned a second spiral chamber 1201, which opens into the outlet 122 of the second compressor stage 12, which opens into the refrigerant circuit 2. The pipe 15 has an inlet connection 150 for connecting the pipe 610 from the auxiliary outlet 61 of the economizer.
[0028] The second radial impeller 120 is mounted on the opposite end of the shaft 13, on which is mounted first radial impeller 110, on which the first radial impeller 110 is mounted, with both radial impellers 110 and 120 mounted on shaft 13 in a mirror-image configuration relative to each other, which means that the leading edges of the blades of each radial impeller 110 and 120 are oriented outward, i.e. , away from the shaft 13, which is advantageous in terms of the forces acting on the shaft 13 during its rotation, since the total force acting on the shaft 13 is equal to the difference between the forces acting on the individual radial impellers 110 and 120.
[0029] The first compressor stage 11 and the second compressor stage 12 are arranged in the compressor housing 8, the electric motor 14 being arranged between them.
[0030] The electric motor 14 comprises a rotor 140 arranged in the central part of the shaft 13, wherein the rotor 140 of the electric motor is provided with a casing 142, which is surrounded by a stator 141, which is mounted in the housing 8 of the compressor. A cooling spiral groove 8 is formed in the housing 8 of the compressor around the stator 141 of the electric motor 14. The cooling spiral groove 8 connects to a cooling inlet channel 80 formed in the housing 8 of the compressor. A cooling pipe 1220, in which a pressure reducing valve 1221 is included, opens into the cooling inlet channel 80. The cooling pipe 1220 is connected to the condenser 3 arranged downstream of the outlet 122 of the second compressor stage 12. The cooling pipe 1220 serves to supply refrigerant in a liquid state, which evaporates during cooling and passes into a gaseousstate, which cools the stator 141 and the rotor 140 and subsequently the refrigerant vapors are transferred to or in front of the first compressor stage 11.
[0031] Connected to the spiral groove 81 is the main cooling system, which comprises an auxiliary channel 82, in which a temperature sensor 822 is mounted. The auxiliary channel 82 is connected to a transfer channel 83, which is formed in the housing 8 of the compressor and in the bearing housing 830 of the second compressor stage and opens into an annular gap 831 formed between the housing 800 of the second compressor stage 12 and the bearing housing 830 of the second compressor stage 12. Downstream of the annular gap 831 the main cooling system is divided into the cooling system for the interior of the electric motor 14 and the cooling system for the bearings of the second compressor stage 12.
[0032] The cooling system of the internal space of the electric motor 14 includes auxiliary transfer channels 832 formed in the bearing housing 830 parallel to the axis of the shaft 13, which are connected to the annular gap 831. The auxiliary transfer channels 832 open into a radial transfer gap 833 between the face of the stator 141 and the bearing housing 830, which is connected to a gap 834 between the internal surface of the stator 141 and the casing 142 of the rotor 140, which ends the cooling system of the internal space of the electric motor and opens into the outlet channel 84 of the refrigerant. The outlet channel 84 is connected to the return pipe 85 of the refrigerant, which opens into the auxiliary inlet 1113 of the first compressor stage 11.
[0033] The cooling system of the bearings 17, 18 of the second stage 12 of the compressor includes horizontal and vertical gaps 835 connecting to the annular gap 831 and opening into the cooling gaps and / or grooves of the second radial gas dynamic bearing 17 and, through the cooling gaps and / or grooves of the double-sided axial gas dynamic bearing 18, it connects to the gap 834 between the internal surface of the stator 141 and the casing 142 of the rotor 140 of the electric motor 14 , where it merges with the cooling system of the internal space of the electric motor 14.
[0034] To cool the second radial gas dynamic bearing 17 and the double-sided axial gas dynam ic bearing 18, a refrigerant supply pipe 836 from the second spiral chamber 1201 is further provided, which connects to the horizontal and verticalgaps 835 between the housing 8 and the bearing housing 830 of the second stage 12 of the compressor.
[0035] To cool the first radial gas dynamic bearing 16, a refrigerant supply pipe 837 from the first spiral chamber 1101 to the cooling space of the first radial gas dynamic bearing 16 is formed in the bearing housing 838 of the first compressor stage 11, wherein this cooling space opens into the outlet channel 84 of the refrigerant.
[0036] Between the second radial impeller 120 of the second compressor stage 12 and the rotor 140 of the electric motor 14, the shaft 13 is mounted in the second radial gas dynamic bearing 17, which is provided with a regulator of the gap between this bearing 17 and the shaft 13. Both the radial gas dynamic bearings 16 and 17 are the same and the surface of the shaft 13 inside these radial bearings 16 and 17 is smooth.
[0037] Between the second radial gas dynamic bearing 17 and the rotor 140 of the electric motor 14, a double-sided axial gas dynamic bearing 18 is mounted on the shaft 13. which comprises an axial disk with shallow grooves on each side of the disk when using graphite bearings and with a smooth surface when using foil bearings.
[0038] Either foil bearings or graphite bearings are used as radial gas dynamic bearings 16, 17.
[0039] A radial foil gas dynamic bearing 16, 17 is schematically represented in Figs. 6a, 6b and comprises a casing 160, 170 for being mounted into a respective bearing housing 830 or 838. Inside the casing 160, 170, axial grooves 161, 171 are formed, in which foil lamellae 162, 172 are arranged, the outer surfaces of which form a cylindrical surface around the unillustrated shaft. In the rest state, the foil lamellae 162, 172 rest on the shaft, and when the shaft rotates, they move away from it, creating a gap between their outer surfaces and the shaft, which is used to allow the refrigerant flow through during the cooling of the bearing.
[0040] The radial graphite gas dynamic bearing 16 is shown in Figs. 7a, 7b, 7c in an embodiment for the first compressor stage 11. The design of the radial graphite bearing 17 of the second compressor stage differs only in the shape and size of the bearing housing 830. The illustrated radial graphite gas dynamicbearing 16 comprises a bearing housing 838, in the internal space of which bearing segments 163 are mounted, on the internal surface of which graphite inserts 164 are mounted. The graphite inserts 164 surround the unillustrated shaft, and between the bearing segments 163 and the internal surface of the bearing housing 838, flat springs 165 are mounted. Opposite the springs 165, clamping screws 166 are arranged in the bearing housing 838, which pass through holes in the springs 165 and abut a support plate 167 mounted in the bearing segment 163 and abutting the respective graphite insert 164. The clamping screw 166 is provided with a spherical surface at the end, with which it rests on the surface of the support plate 167. The outer diameter and shape of the end of the clamping screw 166 are also adapted to the support plate 167 of the bearing segment 163, which allows the fixation of the bearing segment 163 in all directions, including the circumferential direction, but at the same time allows the tilting of the bearing segment 163, thereby ensuring the necessary clearance between the graphite insert 164 of the bearing segment 163 and the shaft 13. Assigned to the clamping screw 166 are two adjusting screws 168, the axes of which are parallel to the axis of the clamping screw 166. Perpendicular to the clamping screws 166, fixing screws 169 are mounted in the bearing housing to secure the position of the clamping screws 166. The clamping screws 166, support plates 167, adjusting screws 168 serve to adjust the gap between the bearing and the shaft 13 for the passage of the refrigerant in the respective radial graphite gas dynamic bearing 16, 17.
[0041] Axial gaps are formed between the bearing segments 163 to allow the refrigerant to flow during bearing operation. Similar axial gaps are formed between the graphite inserts 164 mounted on the segments. Additional space for the passage of the refrigerant is created between the outer surfaces of the segments 163 and the internal surface of the bearing housing 838.
[0042] Either a foil bearing or a graphite bearing is used as an axial gas dynamic bearing 18.
[0043] The double-sided axial gas dynamic bearing 18 is shown schematically in cross-section in Fig. 8 and comprises a double-sided disk 180 which is rigidly connected to the shaft 13 or forms part of it, as in the illustrated embodiment. When graphite bearings are used, the disk 180 is provided on both front surfaceswith curved grooves 181, which, in the illustrated embodiment, extend from the central portion of the disk 180 to its circumference, where they terminate. The curved grooves 181 serve to allow the refrigerant to flow through during bearing operation and may also be formed by other suitable means. On both sides of the disk 180, annular recesses 8301 are formed in the bearing housing 830 of the second compressor stage 12, in which friction rings 182 are mounted; in the case of a foil bearing, the friction rings 182 consist of foil segments 1821, and in the case of a graphite bearing, they consist of graphite segments, which are not shown in detail.
[0044] The overall concept of the cooling of the two-stage compressor 1 according to the invention consists in that a part of the refrigerant in a liquid state is taken downstream of the outlet 122 of the second compressor stage 12 and is fed through the cooling pipe 1220 into the inlet channel 80 for cooling the stator 141 and enters the spiral groove 81 formed in the compressor housing 8 around the stator 141 of the electric motor 14. During its passage through the spiral groove 81 the liquid cools the stator, heats up and the resulting gaseous refrigerant passes into a discharge channel 82, from which it is led into the transfer channel 83, which opens into the annular gap 831 formed between the housing 800 of the second compressor stage 12. A temperature sensor 822 is mounted in the discharge channel 82, which, based on the measured temperature, controls the pressure reducing valve 1221, thereby ensuring an optimal supply of the refrigerant, and regulates also the amount of liquid supplied for cooling so that all the liquid is converted into gas. From the annular gap 831, the gaseous refrigerant passes through the auxiliary transfer channels 832 into the radial transfer gap 833, formed between the face of the stator 141 and the bearing housing 830 of the second compressor stage 12. From the transfer gap 833, the gaseous refrigerant passes into the gap 834 between the internal surface of the stator 141 and the casing 142 of the rotor 140, from which it is directed into the refrigerant outlet channel 84, from which it passes into the return pipe 85 and from there into the auxiliary inlet 1113 of the first compressor stage 11, where it combines with the incoming refrigerant flow from the refrigerant circuit 2.
[0045] The refrigerant from the annular gap 831 is also led into the horizontal and vertical gap 835 and from there into the cooling gaps and / or grooves of thesecond radial gas dynamic bearing 17, from which it passes into the cooling gaps and / or grooves of the double-sided axial bearing 18 and further into the gap 834 between the internal surface of the stator 141 and the casing 142 of the rotor 140 of the electric motor 14.
[0046] To improve the performance of the second radial gas dynamic bearing 17 and the double-sided axial gas dynamic bearing 18, the refrigerant in a gaseous state is taken from the second spiral chamber 1201 and, passing through the refrigerant inlet 836, is directed into the cooling chamber of the second radial gas dynamic bearing 17, where it mixes with the refrigerant supplied from the annular gap 835 and progresses with it into the cooling chamber of the double-sided axial bearing 18, from which it progresses into the gap 834 between the internal surface of the stator 141 and the casing 142 of the rotor 140 of the electric motor 14, where it mixes with the refrigerant supplied from the gap 833 and further progresses together with it.
[0047] To cool the first radial gas dynamic bearing 16, the refrigerant in a gaseous state is taken from the first spiral chamber 1101 and, via the refrigerant inlet 837, is led into the cooling chamber of the first radial gas dynamic bearing 16; after passing through the bearing 16, it is directed into the outlet channel 84, where it mixes with the refrigerant supplied from the gap 834 between the internal surface of the stator 141 and the rotor casing 142 and further progresses together with it.
[0048] Possible variants of multi-stage compressors to which the cooling method of the invention also applies are shown in Fig. 1a, Fig. 1b, and Fig. 1c, in which, compared to the above-described two-stage compressor, the first compressor stage 11 and / or the second compressor stage 12 are essentially supplemented with an additional radial impeller 11b and / or 12b, wherein the original radial impellers are designated 11a and 12a in these drawings and all radial impellers 11a, 11b, 12a, 12b are mounted on the common shaft 13, on which the rotor 140 of the electric motor 14 is mounted.Industrial applicability
[0049] The invention is intended for compressors used to circulate refrigerant in refrigeration systems.List of references
[0050] I compressor
[0051] I I first compressor stage
[0052] 11 a radial impeller of the first stage of the multi-stage compressor
[0053] 11 b additional radial impeller of the first stage of the multi-stage compressor 110 first radial impeller of the first compressor stage
[0054] 1101 first spiral chamber
[0055] 111 inlet of the first compressor stage
[0056] 1110 confusor
[0057] 1111 inlet controlled vanes (AVG)
[0058] 1113 auxiliary inlet of the first compressor stage
[0059] 112 outlet of the first compressor stage
[0060] 12 second compressor stage
[0061] 12a radial impeller of the second stage of the multi-stage compressor 12b additional radial impeller of the second stage of the multi-stage compressor
[0062] 120 second radial impeller of the second compressor stage
[0063] 1201 second spiral chamber
[0064] 121 inlet of the second compressor stage
[0065] 122 outlet of the second compressor stage
[0066] 1220 cooling pipe
[0067] 1221 pressure reducing valve of the cooling pipe
[0068] 13 shaft
[0069] 14 electric motor
[0070] 140 rotor of the electric motor
[0071] 141 stator of the electric motor
[0072] 142 casing of the rotor
[0073] 15 pipe
[0074] 150 connector
[0075] 16 first radial gas dynamic bearing
[0076] 160 casing of the first radial foil gas dynamic bearing
[0077] 161 axial grooves of the first radial foil gas dynamic bearing
[0078] 162 foil lamellae of the first radial foil gas dynamic bearing
[0079] 163 bearing segment of the first radial graphite gas dynamic bearing 165 flat spring
[0080] 166 clamping screw
[0081] 167 support plate / disk
[0082] 168 adjusting screw
[0083] 169 fixing screw
[0084] 17 second radial gas dynamic bearing
[0085] 170 casing of the second radial foil gas dynamic bearing
[0086] 171 axial grooves of the second radial foil gas dynamic bearing
[0087] 172 foil lamellae of the second radial foil gas dynamic bearing
[0088] 18 double-sided axial gas dynamic bearing
[0089] 180 double-sided disk
[0090] 181 curved grooves
[0091] 182 friction rings
[0092] 1821 foil segments2 refrigerant circuit
[0093] 21 outlet of the refrigeration circuit
[0094] 22 inlet of the refrigerant circuit
[0095] 3 condenser
[0096] 4 control valve
[0097] 5 evaporator
[0098] 6 economizer / heat exchanger
[0099] 61 auxiliary outlet of the economizer
[0100] 610 pipe from the auxiliary outlet of the economizer
[0101] 7 control valve of the flow through the economizer
[0102] 8 housing of the compressor
[0103] 80 inlet channel for cooling the stator of the compressor motor
[0104] 800 housing of the second stage of the compressor
[0105] 81 spiral cooling groove
[0106] 82 auxiliary channel
[0107] 822 temperature sensor
[0108] 83 transfer channel
[0109] 830 bearing housing of the second compressor stage
[0110] 8301 annular recesses
[0111] 831 annular gap
[0112] 832 auxiliary transfer channels
[0113] 833 radial transfer gaps between the face end of the stator and the bearing housing of the second stage of the compressor
[0114] 834 gap between the internal surface of the stator and the casing of the rotor 835 horizontal and vertical gaps between the housing and the bearing housing of the second stage of the compressor
[0115] 836 refrigerant supply from the second spiral chamber to the second radial gas dynamic bearing
[0116] 837 refrigerant supply from the first spiral chamber to the first radial gas dynamic bearing
[0117] 838 bearing housing of the first compressor stage
[0118] 84 outlet channel of the refrigerant
[0119] 85 return pipe of the refrigerant
Claims
Patent claims1. A method for cooling a multi-stage centrifugal compressor comprising in each stage radial impellers mounted on a common shaft (13), in the central part of which a rotor (140) of an electric motor (14) is mounted, surrounded by a stator (141), which is mounted in a housing (8) of the compressor, wherein the shaft (13) is mounted in radial gas dynamic bearings arranged on both sides of the rotor (140) of the electric motor (14), characterized in that a liquid refrigerant is led around the outer surface of the stator (141); as it passes around the stator (141), it is heated, and the resulting gaseous refrigerant is used to cool the rotor (140) and the interior of the stator (141) of the electric motor (14) and to cool a second radial gas dynamic bearing (17) and a double-sided axial gas dynamic bearing (18).
2. The method according to claim 1 for cooling a two-stage centrifugal compressor comprising two radial impellers (110, 120) mounted on a common shaft (13), in the central part of which the rotor surrounded by a stator (141), which is mounted in the housing (8) of the compressor, wherein between the impeller (110) of the first stage (11 ) of the compressor and the electric motor (14), the shaft(140) is mounted in a first radial gas dynamic bearing (16), while between the impeller (120) of the second stage (12) of the compressor and the electric motor (14), the shaft (13) is mounted in a second radial gas dynamic bearing (17) and in a double-sided axial gas dynamic bearing (18), wherein the outlet (112) of the first compressor stage (11) is connected to the inlet (121) of the second compressor stage (12), characterized in that a liquid refrigerant is led around the outer surface of the stator (141); as it passes around the stator (141), it is heated, and the resulting gaseous refrigerant is used to cool the rotor (140) and the interior of the stator (141 ) of the electric motor (14) and to cool a second radial gas dynamic bearing (17) and a double-sided axial gas dynamic bearing (18), wherein the bearings (17, 18) are simultaneously cooled by supplying refrigerant from a second spiral chamber (1201), wherein for cooling the first radial gas dynamic bearing (16), gaseous refrigerant is supplied from a first spiral chamber (1101).
3. A multi-stage centrifugal compressor for performing the method according to claim 1 , characterized in that around the outer surface of the stator (141 ) in the housing (8) of the compressor, a cooling spiral groove (81 ) is formed, whose inlet is connected to a condenser (3) arranged downstream of the outlet (122) of the outlet compressor stage (12) for supplying the refrigerant in a liquid state, wherein the cooling spiral groove (81), in which the refrigerant changes its state from liquid to gaseous, connects to the main cooling system terminated with an annular gap (831), downstream of which it is divided into the cooling system of the internal space of the electric motor (14) and the cooling system of the bearings (17, 18) of the outlet compressor stage (12), wherein both of these systems open into the gap (834) between the internal surface of the stator (141) and the casing (142) of the rotor (140).
4. A two-stage centrifugal compressor for performing the method according to claim 2, characterized in that that around the outer surface of the stator (141) in the housing (8) of the compressor, a cooling spiral groove (81) is formed, whose inlet is connected to a condenser (3) arranged downstream of the outlet (122) of the second compressor stage (12) for supplying refrigerant in a liquid state, wherein the cooling spiral groove (81), in which refrigerant changes its state from liquid to gaseous, connects to the main cooling system terminated with an annular gap (831), downstream of which it is divided into the cooling system of the internal space of the electric motor (14) and the cooling system of the bearings (17, 18) of the second compressor stage (12), wherein both of these systems open into a gap (834) between the internal surface of the stator (141) and the casing (142) of the rotor (140), wherein to the end of this gap (834) is connected an outlet channel (84) connected to the first compressor stage (11), the cooling system of the bearings (17,18) of the second stage (12) being connected to the second spiral chamber (1201) and the cooling space of the first radial gas dynamic bearing (16) being connected to the first spiral chamber (1101).
5. The two-stage centrifugal compressor according to claim 4, characterized in that the inlet of the cooling spiral groove (81) connects to an inlet cooling channel (80), into which a cooling pipe (1220) opens, which isconnected to the condenser (3), wherein a pressure reducing valve (1221) is arranged in the cooling pipe.
6. The two-stage centrifugal compressor according to claim 4 or 5, characterized in that the main cooling system comprises an auxiliary channel (82) connected to a transfer channel (83), which is formed in the housing (8) of the compressor and in the bearing housing (830) of the second stage and opens into an annular gap (831 ) created between the housing (800) of the second stage (12) and the bearing housing (830) of the second stage (12).
7. The two-stage centrifugal compressor according to any of claims 4 to 6, characterized in that the cooling system of the internal space of the electric motor (14) comprises auxiliary transfer channels (832) formed in the bearing housing (830) of the second stage (12) of the compressor, which connect to the annular gap (831) and open into the radial transfer gap (833) between the face end of the stator (141) and the bearing housing (830), which connects to a gap (834) between the internal surface of the stator (141 ) and the casing (142) of the rotor (140).
8. The two-stage centrifugal compressor according to any of claims 4 to 7, characterized in that the cooling system of the bearings (17, 18) of the second compressor stage (12) comprises horizontal and vertical gaps (835) connected to the annular gap (831 ) and opening into the cooling gaps and / or grooves of the second radial gas dynamic bearing (17) and from there into the cooling gaps and / or grooves of the axial gas dynamic bearing (18), which open into the gap (834) between the internal surface of the stator (141 ) and the casing (142) of the rotor (140), wherein the refrigerant supply pipe (836) from the second spiral chamber (1201) opens into the horizontal and vertical gaps (835).
9. The two-stage centrifugal compressor according to any of claims 4 to 8, characterized in that the cooling space of the first radial gas dynamic bearing (16) is connected to the first spiral chamber (1101) by means of the inlet (837), wherein this cooling space opens into the outlet channel (84).
10. The two-stage centrifugal compressor according to any of claims 4 to 9, characterized in that the radial gas dynamic bearings (16, 17) are foil gas dynamic bearings.
11. The two-stage centrifugal compressor according to claim 10, characterized in that the radial foil gas dynamic bearing (16, 17) comprises a casing (160, 170), in which axial grooves (161, 171) are formed, in which foil lamellae (162, 172) are mounted, the internal surfaces of which form a cylindrical surface around the shaft (13), wherein there are gaps between the foil lamellae (162, 172) and the shaft (13) for the passage of the refrigerant.
12. The two-stage centrifugal compressor according to any of claims 4 to 8, characterized in that the radial gas dynamic bearings (16, 17) are graphite gas dynamic bearings.
13. The two-stage centrifugal compressor according to claim 12, characterized in that the radial graphite gas dynamic bearing (16, 17) comprises a bearing housing (838), in the internal space of which are mounted bearing segments (163, 173), on the internal surface of which graphite inserts (164, 174) are arranged, surrounding the shaft (13), wherein between the bearing segments (163, 173), as well as between the graphite inserts (164, 174), axial gaps are created for the passage of refrigerant.
14. The two-stage centrifugal compressor according to claim 13, characterized in that between the bearing segments (163) and the internal surface of the bearing housing (838) are mounted flat springs (165), against which clamping screws (166) are arranged in the bearing housing (838) passing through holes in the springs (165) and resting on the support plate (167) mounted in the bearing segment (163) and resting on the respective graphite insert (164).
15. The two-stage centrifugal compressor according to claim 14, characterized in that the clamping screw is provided with a spherical surface at the end, with which it rests on the surface of the support plate (167).
16. The two-stage centrifugal compressor according to any of claims 4 to 15, characterized in that the axial gas dynamic bearing (18) comprises a double-sided disk (180), which is fixedly connected to the shaft (13), wherein in the bearing housing (830) of the second bearing stage (120), on both sides of the disk (180), annular recesses (8301) are formed, in which friction rings (182) are mounted.
17. The two-stage centrifugal compressor according to claim 16, characterized in that the friction rings (182) are formed by foil segments (1821 ).
18. The two-stage centrifugal compressor according to claim 16, characterized in that the friction rings (182) are formed by graphite segments, wherein the disk (180) is provided with curved grooves (181) on both front surfaces.