JP7490367B2 - Refrigeration Cycle Equipment - Google Patents

Description

This disclosure relates to a refrigeration cycle device.

Conventionally, technology is known for supplying liquid refrigerant to the compressor bearings in a refrigeration cycle.

For example, Patent Document 1 describes a refrigerator using water as a refrigerant. This refrigerator includes a compressor as shown in FIG. 4. This compressor includes a housing 322, a rotor, a plurality of bearings 326, a motor, a seal portion 330, a lubricating water supply line 332, and a lubricating water discharge line 334. A compression chamber 322a is formed inside the housing 322. The rotor compresses water vapor as a refrigerant gas by rotating with the driving force of the motor. The rotor has a plurality of impellers 324a and a rotating shaft 324b. Lubricating water is supplied to each bearing 326 through the lubricating water supply line 332. The lubricating water is introduced into a gap formed between the inner surface of the bearing 326 and the outer surface of the rotating shaft 324b to form a water film, and then flows out to both sides in the axial direction. This flowed-out lubricating water accumulates around the bearing 326 inside the housing 322 and is discharged through the lubricating water discharge line 334. The pressure in the space inside the housing 322 in which the bearing 326 is located is approximately 1 atmosphere or higher.

The seal unit 330 is a ring-shaped non-contact seal. The compression chamber 322a is at a negative pressure relative to the space in which the bearing 326 is provided. As a result, some of the lubricating water in the space in which the bearing 326 is provided is sucked into the compression chamber 322a through the gap between the seal unit 330 and the rotating shaft 324b. The seal unit 330 prevents a large amount of lubricating water from being suddenly sucked into the compression chamber 322a. According to Patent Document 1, the negative pressure inside the compression chamber 322a is set to the saturated vapor pressure, so the lubricating water sucked into the compression chamber 322a immediately evaporates.

International Publication No. 2010/010925

The present disclosure provides a refrigeration cycle device that can suppress an increase in power loss caused by droplets colliding with an impeller in a turbo compressor.

The refrigeration cycle device according to the present disclosure includes:
A rotation axis;
A vane wheel fixed to the rotating shaft;
a bearing having a bearing surface facing an outer circumferential surface of the rotating shaft, the bearing supporting the rotating shaft with a liquid-phase refrigerant present between the outer circumferential surface and the bearing surface;
a first discharge space adjacent to the bearing in the axial direction of the rotating shaft and configured to store the liquid-phase refrigerant discharged from the bearing;
A compression chamber in which the impeller is disposed;
a second discharge space adjacent to the first discharge space between the first discharge space and the compression chamber in the axial direction of the rotary shaft;
a seal portion disposed around the rotating shaft between the first discharge space and the second discharge space in the axial direction of the rotating shaft;
a narrowed portion that forms a narrowed flow path around the rotary shaft between the compression chamber and the second discharge space in an axial direction of the rotary shaft; and
an evaporator for generating a vapor phase refrigerant that is supplied to the impeller;
a condenser that condenses the gas phase refrigerant compressed by the turbo compressor;
a first discharge path that communicates the first discharge space with the condenser;
The turbo compressor further includes a second discharge passage that connects the second discharge space with an external space of the turbo compressor.

The above refrigeration cycle device can suppress an increase in power loss caused by droplets colliding with the impeller in the turbo compressor.

FIG. 1 is a diagram showing a configuration of a refrigeration cycle device according to a first embodiment. FIG. 1 is a diagram showing a portion near a condenser of a refrigeration cycle device according to a first embodiment. FIG. 1 shows a configuration of a refrigeration cycle device according to a second embodiment. FIG. 1 is a schematic diagram showing a part of a compressor in a conventional refrigerator.

(Findings that form the basis of this disclosure)
At the time when the present inventors came up with the present disclosure, attempts were being made to develop a technology for supplying a liquid-phase refrigerant in a refrigeration cycle to a bearing of a compressor. In a compressor, a space in which the liquid-phase refrigerant discharged from a bearing exists may be close to another space maintained at a pressure lower than the pressure of the space. For this reason, there was room for more detailed consideration of the handling of the liquid-phase refrigerant discharged from a bearing in a compressor. For example, according to Patent Document 1, it is explained that the negative pressure inside the compression chamber 322a is set to a saturated vapor pressure, so that the lubricating water sucked into the compression chamber 322a immediately evaporates. However, according to the study by the present inventors, it is considered that most of the lubricating water sucked into the compression chamber 322a remains in a liquid state. This is because, even if the lubricating water sucked into the compression chamber 322a comes into contact with the negative pressure environment inside the compression chamber 322a, the enthalpy does not increase enough in the lubricating water to evaporate all of it. For this reason, it is considered that the lubricating water only changes to a gas-liquid two-phase state at most, and a part of the lubricating water remains in a liquid state and forms droplets. The droplets may collide with the impeller 324a and cause a large power loss. The present inventors have newly discovered this problem in the conventional technology, and have come to form the subject of the present disclosure in order to solve this problem.

Below, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. Note that the attached drawings and the following explanation are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIG. 1 and FIG.

[1-1. Configuration]
As shown in FIG. 1, the refrigeration cycle device 1a includes a turbo compressor 10a, an evaporator 20, a condenser 30, a first discharge path 41, and a second discharge path 42. The turbo compressor 10a includes a rotating shaft 11, an impeller 12, a first bearing 13, a first discharge space 14f, a second discharge space 14s, a compression chamber 15, a seal portion 16, and a narrowed portion 17. The impeller 12 is fixed to the rotating shaft 11. The impeller 12 is disposed in the compression chamber 15. The first bearing 13 has a bearing surface 13b facing the outer circumferential surface 11g of the rotating shaft 11. In addition, the first bearing 13 supports the rotating shaft 11 with a liquid-phase refrigerant present between the outer circumferential surface 11g and the bearing surface 13b. The first discharge space 14f is adjacent to the first bearing 13 in the axial direction of the rotating shaft 11, and stores the liquid-phase refrigerant discharged from the first bearing 13. The second discharge space 14s is adjacent to the first discharge space 14f between the first discharge space 14f and the compression chamber 15 in the axial direction of the rotating shaft 11. The seal portion 16 is disposed around the rotating shaft 11 between the first discharge space 14f and the second discharge space 14s in the axial direction of the rotating shaft 11. The narrowed portion 17 forms a narrow flow path around the rotating shaft 11 between the compression chamber 15 and the second discharge space 14s in the axial direction of the rotating shaft 11. The evaporator 20 generates a gas-phase refrigerant to be supplied toward the impeller 12. The condenser 30 condenses the gas-phase refrigerant compressed by the turbo compressor 10a. The first discharge path 41 communicates the first discharge space 14f with the condenser 30. The second discharge path 42 communicates the second discharge space 14s with an external space of the turbo compressor 10a.

[1-2. motion]
The operation and function of the refrigeration cycle apparatus 1a configured as above will be described below. The evaporator 20 stores, for example, a liquid-phase refrigerant. The liquid-phase refrigerant stored in the refrigerant storage tank 20 evaporates to generate a gas-phase refrigerant. This gas-phase refrigerant is supplied to the turbo compressor 10a and guided to the suction space 15q. The gas-phase refrigerant is then compressed. In the chamber 15, the refrigerant is compressed by passing through the impeller 12 and is discharged toward the condenser 30. Next, the gas phase refrigerant is condensed in the condenser 30 and changes to a liquid phase refrigerant. The liquid phase refrigerant is The refrigerant is then circulated to the evaporator 20. This circulation of the refrigerant completes a refrigeration cycle.

In the refrigeration cycle device 1a, a portion of the liquid-phase refrigerant is supplied toward the first bearing 13. The liquid-phase refrigerant forms a liquid film between the outer peripheral surface 11g and the bearing surface 13b, and is discharged from the first bearing 13. The temperature of the liquid-phase refrigerant discharged from the first bearing 13 rises due to friction loss in the first bearing 13, and for example, in the first discharge space 14f, the refrigerant exists in a gas-liquid two-phase state. On the other hand, the pressure in the condenser 30 is maintained at, for example, the saturated vapor pressure of the refrigerant at a temperature lower than the temperature of the refrigerant stored in the first discharge space 14f. Most of the liquid-phase refrigerant stored in the first discharge space 14f is led to the condenser 30 through the first discharge path 41. This is because the pressure loss of the flow of the liquid-phase refrigerant moving from the first discharge space 14f to the second discharge space 14s is large due to the seal portion 16, and the pressure loss in the first discharge path 41 is relatively small. The pressure in the first discharge space 14f increases so that the liquid-phase refrigerant is discharged according to the pressure loss in the first discharge path 41.

A small amount of liquid-phase refrigerant can pass through the seal portion 16 and be guided to the second discharge space 14s. The small amount of liquid-phase refrigerant guided to the second discharge space 14s is stored in the second discharge space 14s and then guided to the outside of the turbo compressor 10a through the second discharge path 42.

[1-3. Effects, etc.]
As described above, in the present embodiment, the turbo compressor 10a of the refrigeration cycle apparatus 1a includes the first discharge space 14f, the second discharge space 14s, the seal portion 16, and the narrowed portion 17. The first discharge space 14f is adjacent to the first bearing 13 in the axial direction of the rotating shaft 11, and stores the liquid-phase refrigerant discharged from the first bearing 13. The second discharge space 14s is adjacent to the first discharge space 14f between the first discharge space 14f and the compression chamber 15 in the axial direction of the rotating shaft 11. The seal portion 16 is disposed around the rotating shaft 11 between the first discharge space 14f and the second discharge space 14s in the axial direction of the rotating shaft 11. The narrowed portion 17 forms a narrowed flow path around the rotating shaft 11 between the compression chamber 15 and the second discharge space 14s in the axial direction of the rotating shaft 11. The seal portion 16 allows most of the liquid-phase refrigerant stored in the first discharge space 14f to be discharged through the first discharge path 41, and only a small amount of liquid-phase refrigerant passes through the seal portion 16 and is guided to the second discharge space 14s. In addition, a small amount of liquid-phase refrigerant is stored in the second discharge space 14s, and the narrowing portion 17 makes it difficult for the small amount of liquid-phase refrigerant stored in the second discharge space 14s to be guided to the compression chamber 15. This makes it possible to suppress the liquid-phase refrigerant discharged from the first bearing 13 from being guided to the compression chamber 15. As a result, it is possible to suppress an increase in power loss due to collision of liquid droplets with the impeller 12 in the turbo compressor 10a.

As shown in FIG. 1, the second discharge path 42 may be connected to the condenser 30. This allows the liquid phase refrigerant stored in the second discharge space 14s to be guided to the condenser 30.

2, the second discharge path 42 may have a downward flow path 42k. The downward flow path 42k is located below the liquid level L of the liquid-phase refrigerant stored in the condenser 30. This forms a liquid seal in the downward flow path 42k. Therefore, even if the temperature in the condenser 30 is high and the pressure in the condenser 30 is higher than the pressure in the second discharge space 14s, the high-pressure gas-phase refrigerant cannot pass through the second discharge path 42, and the liquid-phase refrigerant stored in the second discharge space 14s is discharged without hindrance. The height of the liquid level in the liquid seal is maintained at a desired height by increasing the pressure in the second discharge space 14s and making the difference between the pressure in the condenser 30 and the pressure in the second discharge space 14s a desired value.

As shown in FIG. 2, the second discharge path 42 may be connected to the condenser 30 above the liquid level L of the liquid-phase refrigerant stored in the condenser 30. The second discharge path 42 may be connected to the condenser 30 below the liquid level L of the liquid-phase refrigerant stored in the condenser 30.

The connection between the second discharge path 42 and the second discharge space 14s is located, for example, below the axis of the rotating shaft 11. As described above, a small amount of liquid-phase refrigerant is stored in the second discharge space 14s. Because the connection between the second discharge path 42 and the second discharge space 14s is located below the axis of the rotating shaft 11, the small amount of liquid-phase refrigerant stored in the second discharge space 14s is easily discharged.

As shown in FIG. 1, the turbo compressor 10a may further include a third discharge space 14t and a communication passage 14v. The third discharge space 14t is adjacent to the first bearing 13 in the axial direction of the rotating shaft 11, and stores the liquid-phase refrigerant discharged from the first bearing 13 away from the first discharge space 14f. The communication passage 14v connects the first discharge space 14f and the third discharge space 14t. As a result, the liquid-phase refrigerant stored in the third discharge space 14t is guided to the first discharge space 14f through the communication passage 14v, and most of it is guided to the condenser 30 through the first discharge path 41. This simplifies the configuration of the flow path for discharging the liquid-phase refrigerant from the third discharge space 14t.

The communication passage 14v, for example, connects the bottom of the first discharge space 14f to the bottom of the third discharge space 14t.

The sealing portion 16 maintains the difference ΔP, obtained by subtracting the pressure in the first discharge space 14f from the pressure in the second discharge space 14s, at a desired value during operation of the refrigeration cycle device 1a. For example, the sealing portion 16 maintains the difference ΔP at a magnitude of 1 kP to 1 MPa. The sealing portion 16 may maintain the difference ΔP at a magnitude of 1 kPa to 100 kPa. The sealing portion 16 is, for example, constituted by a seal ring.

The dimension N of the narrowed flow passage formed by the narrowed portion 17 in a direction perpendicular to the axis of the rotating shaft 11 satisfies, for example, the condition N/D≦1.5. Here, D means the diameter of the rotating shaft 11 at the portion of the rotating shaft 11 that contacts the narrowed portion 17. This more reliably prevents the small amount of liquid-phase refrigerant stored in the second discharge space 14s from being led to the compression chamber 15. N/D is preferably 1.2 or less, and more preferably 1.1 or less. A seal ring may be arranged in the narrowed portion 17.

The turbo compressor 10a is, for example, a single-stage compressor.

As shown in FIG. 1, the turbo compressor 10a further includes, for example, a motor 18. The motor 18 includes, for example, a stator 18s and a rotor 18r. The rotor 18r is fixed to the rotating shaft 11. The rotating shaft 11, the impeller 12, and the rotor 18r form a rotating body, and the rotating body rotates when the motor 18 is operated, compressing the gas-phase refrigerant in the compression chamber 15.

The impeller 12 is a impeller that constitutes a velocity-type fluid machine, such as a centrifugal type, mixed flow type, or axial flow type.

The second discharge space 14s is adjacent to the space in the compression chamber 15 in which the gas-phase refrigerant that has passed through the impeller 12 is present, for example.

As shown in FIG. 1, for example, a liquid supply flow path 11p is formed inside the rotating shaft 11. The liquid supply flow path 11p has, for example, a first liquid supply flow path 11a and a second liquid supply flow path 11b. The first liquid supply flow path 11a extends from one end of the rotating shaft 11 in the axial direction of the rotating shaft 11. The second liquid supply flow path 11b extends from the first liquid supply flow path 11a to the outer circumferential surface 11g of the rotating shaft 11. During operation of the refrigeration cycle device 1a, a liquid phase refrigerant is supplied to the liquid supply flow path 11p. When the rotating shaft 11 rotates, the liquid phase refrigerant in the liquid supply flow path 11p is supplied toward the first bearing 13.

As shown in FIG. 1, the refrigeration cycle device 1a further includes, for example, a liquid supply pump 50. The liquid supply pump 50 pumps the liquid phase refrigerant toward the liquid supply flow path 11p. For example, the liquid supply pump 50 pumps a portion of the liquid phase refrigerant stored in the condenser 30 toward the liquid supply flow path 11p.

As shown in FIG. 1, the turbo compressor 1a further includes, for example, a second bearing 19. The first bearing 13 is disposed, for example, between the second bearing 19 and the impeller 12. The second bearing 19 stably supports the rotating shaft 11. The second bearing 19 is, for example, a slide bearing. The liquid phase refrigerant in the liquid supply passage 11p may be supplied toward the second bearing 19. In this case, the liquid phase refrigerant discharged from the second bearing 19 is discharged to the outside of the turbo compressor 1a through a predetermined discharge path. The second bearing 19 may be a magnetic bearing.

The evaporator 20 is, for example, a container having thermal insulation and pressure resistance. The evaporator 20 stores liquid-phase refrigerant and evaporates the liquid-phase refrigerant inside. The liquid-phase refrigerant inside the evaporator 20 absorbs heat provided from outside the evaporator 20 and evaporates. The evaporator 20 may be an indirect contact type heat exchanger such as a shell-tube heat exchanger, or a direct contact type heat exchanger such as a spray type or filler type heat exchanger.

The condenser 30 is, for example, composed of a container having thermal insulation and pressure resistance. The condenser 30 may be an indirect contact type heat exchanger such as a shell-tube heat exchanger, or a direct contact type heat exchanger such as a spray type or filler type heat exchanger.

In the refrigeration cycle device 1a, the refrigerant is not limited to a specific refrigerant. For example, the refrigeration cycle device 1a is filled with a refrigerant whose main component is a substance whose saturated vapor pressure at room temperature (Japanese Industrial Standard: 20°C ± 15°C/JIS Z8703) is negative (an absolute pressure lower than atmospheric pressure). An example of such a refrigerant is a refrigerant whose main component is water. "Main component" means the component that is present in the largest amount by mass.

A typical example of operating conditions for the refrigeration cycle device 1a is shown when the refrigerant is water. The pressure in the condenser 30 is, for example, 1128 kPa, which is the saturated vapor pressure of water at 10°C. The temperature of the water discharged from the first bearing 13 is 20°C. The temperature of the water stored in the first discharge space 14f is 15°C. The liquid supply pump 50 increases the pressure of a portion of the liquid phase refrigerant stored in the condenser 30 to 1 atmosphere.

(Embodiment 2)
Hereinafter, the second embodiment will be described with reference to Fig. 3. The refrigeration cycle apparatus 1b shown in Fig. 3 is configured similarly to the refrigeration cycle apparatus 1a, except for the parts that will be particularly described. The same reference numerals are used to designate the same or corresponding components of the refrigeration cycle apparatus 1a, and detailed description thereof will be omitted. The description of the refrigeration cycle apparatus 1a also applies to the refrigeration cycle apparatus 1b, unless there is a technical contradiction.

As shown in FIG. 3, in the refrigeration cycle device 1b, the second exhaust path 42 is connected to the evaporator 20.

The operation and action of the refrigeration cycle device 1b configured as above will be described below. Depending on the installation location of the refrigeration cycle device 1b, the height difference between the turbo compressor 10a and the condenser 30 may be small. In this case, the difference in the positional head at both ends of the first discharge path 41 becomes small, and the pressure in the first discharge space 14f becomes high. Therefore, the amount of liquid-phase refrigerant passing through the seal portion 16 increases. The temperature and pressure in the evaporator 20 are lower than the temperature and pressure in the condenser 30. Therefore, since the second discharge path 42 is connected to the evaporator 20, the pressure in the second discharge space 14s tends to be low. As a result, the liquid-phase refrigerant stored in the second discharge space 14s is less likely to be led to the compression chamber 15, and the liquid-phase refrigerant discharged from the first bearing 13 can be suppressed from being led to the compression chamber 15. In this way, according to the refrigeration cycle device 1b, even if the height difference between the turbo compressor 10a and the condenser 30 is small, the liquid-phase refrigerant discharged from the first bearing 13 can be suppressed from being led to the compression chamber 15.

Other Embodiments
As described above, the first and second embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. have been made. In addition, it is also possible to combine the components described in the first and second embodiments above to create new embodiments. Therefore, other embodiments will be described below as examples.

In the first and second embodiments, the turbo compressor 10a, which is a single-stage compressor, has been described as an example of a turbo compressor. The turbo compressor may include a rotating shaft 11, a vane wheel 12, a first bearing 13, a first discharge space 14f, a second discharge space 14s, a compression chamber 15, a seal portion 16, and a narrowed portion 17. Therefore, the turbo compressor is not limited to the turbo compressor 10a, which is a single-stage compressor. A multi-stage compressor may be used as the turbo compressor. In this case, the vane wheel 12 constitutes, for example, the first stage. The pressure of the compression chamber 15 in which the vane wheel 12 of the first stage is arranged tends to be low. However, the first discharge space 14f, the second discharge space 14s, the seal portion 16, and the narrowed portion 17 act to prevent the liquid-phase refrigerant discharged from the first bearing 13 from being led to the compression chamber 15.

In the first and second embodiments, the second discharge space 14s is described as a space adjacent to the space in the compression chamber 15 where the gas-phase refrigerant that has passed through the impeller 12 exists. The second discharge space 14s may be a space adjacent to the first discharge space 14f between the first discharge space 14f and the compression chamber 15 in the axial direction of the rotating shaft 11. Therefore, the second discharge space 14s is not limited to a space adjacent to the space in the compression chamber 15 where the gas-phase refrigerant that has passed through the impeller 12 exists. However, if the second discharge space 14s is a space adjacent to the space where the gas-phase refrigerant that has passed through the impeller 12 exists, the liquid-phase refrigerant stored in the second discharge space 14s is unlikely to be led by the compression chamber 15. The second discharge space 14s may also be a space adjacent to the space in the compression chamber 15 where the gas-phase refrigerant exists before passing through the impeller 12.

In the first and second embodiments, the third discharge space 14t is described as a space connected to the first discharge space 14f by the communication passage 14v. The third discharge space 14t may be adjacent to the first bearing 13 in the axial direction of the rotating shaft 11 and may be a space that stores the liquid-phase refrigerant that is discharged from the first bearing 13 away from the first discharge space 14f. Therefore, the third discharge space 14t is not limited to a space that is connected to the first discharge space 14f by the communication passage 14v. The third discharge space 14t may be directly connected to the first discharge path 41, or may be connected to a discharge path other than the first discharge path 41.

The above-described embodiments are intended to illustrate the technology disclosed herein, and various modifications, substitutions, additions, and omissions may be made within the scope of the claims or their equivalents.

The present disclosure is applicable to a refrigeration cycle device that can suppress an increase in power loss due to the collision of droplets with an impeller in a turbo compressor. Specifically, the present disclosure is applicable to air conditioners and chillers.

1a, 1b refrigeration cycle device 10a turbo compressor 11 rotating shaft 11g outer circumferential surface 12 impeller 13 bearing (first bearing)
Reference Signs List 13b Bearing surface 14f First discharge space 14s Second discharge space 14t Third discharge space 14v Communication passage 15 Compression chamber 16 Sealing portion 17 Narrowing portion 20 Evaporator 30 Condenser 41 First discharge path 42 Second discharge path 42k Downward flow path

Claims (5)

A rotation axis;
A vane wheel fixed to the rotating shaft;
a bearing having a bearing surface facing an outer circumferential surface of the rotating shaft, the bearing supporting the rotating shaft with a liquid-phase refrigerant present between the outer circumferential surface and the bearing surface;
a first discharge space adjacent to the bearing in the axial direction of the rotating shaft and configured to store the liquid-phase refrigerant discharged from the bearing;
A compression chamber in which the impeller is disposed;
a second discharge space adjacent to the first discharge space between the first discharge space and the compression chamber in the axial direction of the rotary shaft;
a seal portion disposed around the rotating shaft between the first discharge space and the second discharge space in the axial direction of the rotating shaft;
a narrowed portion that forms a narrowed flow path around the rotary shaft between the compression chamber and the second discharge space in an axial direction of the rotary shaft; and
an evaporator for generating a vapor phase refrigerant that is supplied to the impeller;
a condenser that condenses the gas phase refrigerant compressed by the turbo compressor;
a first discharge path that communicates the first discharge space with the condenser;
a second discharge passage that communicates the second discharge space with an external space of the turbo compressor ,
The second discharge space is adjacent to a space in the compression chamber where the gas phase refrigerant that has passed through the impeller exists.
Refrigeration cycle equipment. The refrigeration cycle device according to claim 1, wherein the second exhaust path is connected to the condenser. The refrigeration cycle device according to claim 2, wherein the second discharge path has a downward flow path located below the liquid level of the liquid-phase refrigerant stored in the condenser. The refrigeration cycle device according to claim 1, wherein the second exhaust path is connected to the evaporator. The refrigeration cycle device according to any one of claims 1 to 4, wherein the turbo compressor further comprises a third discharge space adjacent to the bearing in the axial direction of the rotating shaft, for storing the liquid-phase refrigerant that moves away from the first discharge space and is discharged from the bearing, and a communication passage that connects the first discharge space to the third discharge space.

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