JP2022028991A - Turbo-compressor and refrigeration cycle device - Google Patents

Abstract

To provide a turbo-compressor advantageous for enhancing stability of rotation of a rotating shaft.SOLUTION: A turbo-compressor (1a) comprises a rotating shaft (10), a first impeller (21), a second impeller (22), a first bearing (41), and a return flow passage (82a). The first impeller (21) comprises a first suction port (21a) and a first discharge port (21b). The second impeller (22) comprises a second suction port (22a) and a second discharge port (22b). The first bearing (41) rotatably supports the rotating shaft (10). The return flow passage (82a) guides working fluid from the first discharge port (21b) to the second suction port (22a). The first suction port (21a) and the second suction port (22a) are opened in a same direction.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to turbo compressors and refrigeration cycle devices.

Conventionally, a multi-stage turbo compressor for compressing a low-pressure refrigerant has been known.

As shown in FIG. 4A, Patent Document 1 describes a turbo compressor 200. The turbo compressor 200 includes a casing 221, an electric motor 213, a rotary shaft 225, a rolling bearing 227, and a slide bearing 228. Two-stage impellers 223a and 223b are fixed to one end of the rotating shaft 225, and the impellers 223a and 223b form a compression portion 223 together with a compression passage structure. The rolling bearing 227 pivotally supports the rotary shaft 225 between the motor 213 and the impellers 223a and 223b, and the other end of the rotary shaft 225 is pivotally supported by the slide bearing 228. The rolling bearing 227 has two angular contact ball bearings 227a and 227b. In the slide bearing 228, the bearing metal 228a is press-fitted into the bearing boss 221d. The motor 213 includes a stator 213A and a rotor 213B fixed to a rotating shaft 225. When the compression unit 223 is driven by the electric motor 213, the vaporized refrigerant is sucked into the compression unit 223 and compressed.

On the other hand, conventionally, as a turbo compressor, a multi-stage centrifugal compressor having a return flow path is known. For example, as shown in FIG. 4B, Patent Document 2 describes a multi-stage centrifugal compressor 300. The multi-stage centrifugal compressor 300 includes a first-stage impeller 301, a second-stage impeller 304, a diffuser 306, a return vane 307, a diffuser vane 308, a stage labyrinth 309, and a rotary shaft 310. The multi-stage centrifugal compressor 300 has a return flow path for allowing a gas flow from the diffuser 306 to flow into the next-stage impeller 304, and a return vane 307 is arranged in the return flow path. In FIG. 4B, the white arrows indicate the mainstream of the gas flow. The return flow path converts the velocity energy of the gas into pressure energy. In FIG. 4B, C is the axis of the rotating shaft 310.

Japanese Unexamined Patent Publication No. 2017-125434 Japanese Unexamined Patent Publication No. 7-127600

According to the techniques described in Patent Documents 1 and 2, for example, a working fluid such as a gas phase refrigerant having a saturated vapor pressure of atmospheric pressure or less at room temperature (20 ° C ± 15 ° C: Japanese Industrial Standard JIS Z 8703) is compressed. In some cases, there is room to improve the rotational stability of the rotating shaft.

The present disclosure provides a turbo compressor that is advantageous for enhancing the rotational stability of the rotating shaft.

This disclosure is
The axis of rotation and
A first impeller fixed to the rotating shaft and having a first suction port for sucking the working fluid and a first discharge port for discharging the working fluid.
A second impeller fixed to the rotating shaft and having a second suction port for sucking the working fluid and a second discharge port for discharging the working fluid.
A first bearing, which is arranged between the first impeller and the second impeller in the axial direction of the rotation axis and rotatably supports the rotation axis,
A return flow path for guiding the working fluid from the first discharge port to the second suction port is provided.
The first suction port and the second suction port are open in the same direction.
Provides a turbo compressor.

The above turbo compressor is advantageous for enhancing the rotational stability of the rotating shaft.

FIG. 1 is a cross-sectional view showing an example of the turbo compressor of the present disclosure. FIG. 2 is a configuration diagram showing an example of the refrigeration cycle apparatus of the present disclosure. FIG. 3 is a cross-sectional view showing another example of the turbo compressor of the present disclosure. FIG. 4A is a cross-sectional view showing a conventional turbo compressor. FIG. 4B is a cross-sectional view showing a conventional multi-stage centrifugal compressor.

(Findings underlying this disclosure)
For example, it is conceivable to compress a working fluid having a saturated vapor pressure of atmospheric pressure or less at room temperature by using a multi-stage turbo compressor having a return flow path. In this case, it is necessary to increase the cross-sectional area of the return flow path. This is because such a working fluid flows through the return flow path with a large specific volume, and the volumetric flow rate of the working fluid in the return flow path is large. On the other hand, in order to increase the cross-sectional area of the return flow path, it is necessary to lengthen the length of the rotation axis in the axial direction. However, this tends to reduce the natural frequency based on the flexural rigidity of the rotating shaft. When the natural frequency based on the bending rigidity of the rotating shaft is low, the natural frequency based on the bending rigidity of the rotating shaft and the rotating number of the rotating shaft become close to each other, causing resonance, and the rotating shaft is rotated at a desired rotation number. It becomes difficult. Therefore, in order to prevent a decrease in the natural frequency based on the flexural rigidity of the rotating shaft, it is desirable to suppress the extension of the length of the rotating shaft in the axial direction. Therefore, the present inventors have made extensive studies on the configuration of a turbo compressor for increasing the cross-sectional area of the return flow path while suppressing the extension of the length of the rotating shaft in the axial direction. As a result, the present inventors have newly found a desired arrangement relationship between the bearing that rotatably supports the rotation shaft and the return flow path, and devised the turbo compressor of the present disclosure. It should be noted that this finding is based on the studies of the present inventors and is not self-identified as prior art.

(Summary of one aspect pertaining to this disclosure)
The turbo compressor according to the first aspect of the present disclosure is
The axis of rotation and
A first impeller fixed to the rotating shaft and having a first suction port for sucking the working fluid and a first discharge port for discharging the working fluid.
A second impeller fixed to the rotating shaft and having a second suction port for sucking the working fluid and a second discharge port for discharging the working fluid.
A first bearing, which is arranged between the first impeller and the second impeller in the axial direction of the rotation axis and rotatably supports the rotation axis,
A return flow path for guiding the working fluid from the first discharge port to the second suction port is provided.
The first suction port and the second suction port are open in the same direction.

According to the first aspect, since the first bearing is arranged between the first impeller and the second impeller in the axial direction of the rotating shaft, the return flow is suppressed while suppressing the extension of the length in the axial direction of the rotating shaft. It is easy to increase the cross-sectional area of the road. This makes it possible to prevent a decrease in the natural frequency based on the flexural rigidity of the rotating shaft. Therefore, the turbo compressor according to the first aspect is advantageous for improving the rotational stability of the rotating shaft.

In the second aspect of the present disclosure, for example, in the turbo compressor according to the first aspect, all the regions where the first bearing exists in the axial direction overlap with the region where the return flow path exists in the axial direction. ing. According to the second aspect, it is possible to more reliably suppress the extension of the length of the rotation axis in the axial direction.

In the third aspect of the present disclosure, for example, in the turbo compressor according to the first aspect or the second aspect, the working fluid having a saturated vapor pressure of atmospheric pressure or less at room temperature may be accelerated and compressed. According to the third aspect, it is possible to compress a working fluid having a saturated vapor pressure of atmospheric pressure or less at room temperature in a state where the rotation stability of the rotating shaft is high.

In the fourth aspect of the present disclosure, for example, the turbo compressor according to the first to third aspects is arranged at a position farther from the first impeller than the first bearing in the axial direction, and the rotary shaft is provided. A second bearing that rotatably supports and a motor having a rotor fixed to the rotating shaft between the first bearing and the second bearing in the axial direction may be further provided. According to the fourth aspect, it is possible to improve the rotational stability of the rotating shaft in a state where the rotor of the motor is fixed to the rotating shaft.

In the fifth aspect of the present disclosure, for example, the turbo compressor according to the first to fourth aspects has a first suction port and a third suction port that is open in the same direction as the second suction port. A third impeller, which is located at a position away from the first bearing in the axial direction and is fixed to the rotating shaft, may be further provided, and the second impeller is the first impeller and the third impeller. It may be arranged between the impeller and the diameter of the rotating shaft at the fixed position of the third impeller, and may be equal to or larger than the diameter of the rotating shaft at the fixed position of the second impeller. According to the fifth aspect, it is easy to realize the operation at a high pressure ratio by the third impeller. In addition, since the diameter of the rotating shaft at the fixed position of the third impeller is equal to or larger than the diameter of the rotating shaft at the fixed position of the second impeller, the bending rigidity of the rotating shaft tends to increase. Therefore, according to the fifth aspect, it is possible to prevent a decrease in the natural frequency based on the flexural rigidity of the rotating shaft.

In the sixth aspect of the present disclosure, for example, the turbo compressor according to the fifth aspect is arranged at a position farther from the first impeller than the first bearing in the axial direction, and rotatably supports the rotary shaft. The third impeller may further include a second bearing and a motor having a rotor fixed to the rotating shaft between the first bearing and the second bearing in the axial direction. , May be fixed between the second impeller and the rotor in the front axis direction. According to the sixth aspect, the stability of rotation of the rotating shaft can be improved in a state where the rotor of the motor is fixed to the rotating shaft.

The refrigeration cycle apparatus according to the seventh aspect of the present disclosure is
An evaporator that produces a vapor phase refrigerant and
A turbo compressor according to any one of the first to sixth aspects, which compresses the vapor phase refrigerant generated in the evaporator as the working fluid.
A condenser for condensing the gas phase refrigerant compressed by the turbo compressor is provided.

According to the seventh aspect, the vapor phase refrigerant generated in the evaporator can be compressed while the rotation stability of the rotation shaft of the turbo compressor is high.

In the eighth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the seventh aspect, the evaporator may store the liquid phase refrigerant in the inside thereof, and the condenser stores the liquid phase refrigerant in the inside thereof. Alternatively, at least one of the liquid phase refrigerant stored in the evaporator and the liquid phase refrigerant stored in the condenser may be supplied to the first bearing. According to the eighth aspect, for example, at least one of the liquid phase refrigerant stored in the evaporator and the liquid phase refrigerant stored in the condenser can be used for lubrication or cooling of the first bearing.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following description relates to an example of the present disclosure, and the present disclosure is not limited to the following embodiments.

As shown in FIG. 1, the turbo compressor 1a includes a rotating shaft 10, a first impeller 21, a second impeller 22, a first bearing 41, and a return flow path 82a. The first impeller 21 is fixed to the rotating shaft 10. The first impeller 21 has a first suction port 21a into which the working fluid is sucked and a first discharge port 21b in which the working fluid is discharged. The second impeller 22 is fixed to the rotating shaft 10. The second impeller 22 has a second suction port 22a into which the working fluid is sucked and a second discharge port 22b in which the working fluid is discharged. The first bearing 41 is arranged between the first impeller 21 and the second impeller 22 in the axial direction of the rotating shaft, and rotatably supports the rotating shaft 10. The first bearing 41 is an indispensable member for rotatably supporting the rotating shaft 10. The first bearing 41 is distinguished from the sealing member, which is not indispensable for rotatably supporting the rotating shaft 10, from such a viewpoint. The return flow path 82a is a flow path that guides the working fluid from the first discharge port 21b to the second suction port 22a. The first suction port 21a and the second suction port 22a are open in the same direction.

For example, the entire region where the first bearing 41 exists in the axial direction of the rotating shaft 10 overlaps with the region where the return flow path 82a exists in the axial direction of the rotating shaft 10.

The first impeller 21 is fixed to, for example, one end of the rotating shaft 10. Since the first bearing 41 is arranged between the first impeller 21 and the second impeller 22 in the axial direction of the rotating shaft 10, the first impeller 21 is fixed to one end of the rotating shaft 10. Also, the first bearing 41 can be rotatably supported.

The turbo compressor 1a includes, for example, a casing 60, and the first bearing 41 is fixed to the casing 60. The casing 60 has a wall surface forming a stationary flow path, and the return flow path 82a exists inside the casing 60.

As shown in FIG. 1, the turbo compressor 1a further includes, for example, a motor 70. The motor 70 includes, for example, a rotor 71 and a stator 72. The rotor 71 is fixed to the rotating shaft 10, for example. The rotor 71 is preferably fixed to the rotating shaft 10 at a position farther from the first impeller 21 than the second impeller 22 in the axial direction of the rotating shaft 10. In other words, the first impeller 21, the second impeller 22, and the rotor 71 are arranged in this order in the axial direction of the rotating shaft 10. The stator 72 is fixed to the casing 60, for example. When electric power is supplied to the motor 70, a rotating magnetic field is generated by the stator 72, and a rotational torque is generated in the rotor 71. As a result, the first impeller 21 and the second impeller 22 fixed to the rotation shaft 10 rotate.

The turbo compressor 1a accelerates and compresses a working fluid having a saturated vapor pressure of atmospheric pressure or less at room temperature, for example. The working fluid is typically the gas phase. Water can preferably be used as such a working fluid. Since such a working fluid easily flows through the return flow path with a large specific volume, it is highly necessary to increase the cross-sectional area of the return flow path. In some cases, the turbo compressor 1a may accelerate and compress a working fluid having a saturated vapor pressure exceeding atmospheric pressure at room temperature.

The turbo compressor 1a further includes, for example, a second bearing 42. The second bearing 42 is arranged at a position farther from the first impeller 21 than the first bearing 41 in the axial direction of the rotating shaft 10. The second bearing 42 rotatably supports the rotating shaft 10. The rotor 71 of the motor 70 is fixed to the rotating shaft 10 between the first bearing 41 and the second bearing 42 in the axial direction of the rotating shaft 10, for example. The center of the rotating shaft 10 in the axial direction is located, for example, between the second impeller 22 and the rotor 71.

The rotating shaft 10 preferably has an axisymmetric shape with high accuracy in order to minimize imbalance during rotation. The rotor 71 is fixed to the rotating shaft 10 by, for example, shrink fitting. A sufficiently large shrink fit margin is secured in the shrink fit of the rotor 71 so that the shrink fit margin remains even if the diameter of the rotor 71 is slightly expanded due to centrifugal force as the rotary shaft 10 rotates at high speed. .. The rotation speed of the rotation shaft 10 is, for example, from 5000 revolutions per minute (rpm) to 100,000 rpm. The material of the rotating shaft 10 is not limited to a specific material. The material of the rotating shaft 10 can be, for example, a high-strength iron-based material such as SNCM630.

For example, the diameter of the rotating shaft 10 at the fixed position of the second impeller 22 is larger than the diameter of the rotating shaft 10 at the fixed position of the first impeller 21. In this case, the rotating shaft 10 has a large diameter near the center, and the natural frequency based on the bending rigidity of the rotating shaft 10 tends to be high. Therefore, the rotation stability of the rotating shaft 10 tends to be high.

In the turbo compressor 1a, the first impeller 21 and the second impeller 22 typically constitute a centrifugal compression mechanism. The outer diameter of the portion forming the first suction port 21a of the first impeller 21 is smaller than, for example, the outer diameter of the portion forming the first discharge port 21b of the first impeller 21. The first suction port 21a is opened, for example, in front of the first impeller 21. The first discharge port 21b is open outward in the radial direction of the first impeller 21. The outer diameter of the portion forming the second suction port 22a of the second impeller 22 is smaller than, for example, the outer diameter of the portion forming the second discharge port 22b of the second impeller 22. The second suction port 22a is opened, for example, in front of the second impeller 22. The second discharge port 22b is open to the outside in the radial direction of the second impeller 22.

The return flow path 82a is, for example, an annular flow path located outside the first bearing 41 in a direction perpendicular to the axis of the rotating shaft 10. The outer diameter of the portion forming the first discharge port 21b of the first impeller 21 is smaller than, for example, the outer diameter of the portion forming the second suction port 22a of the second impeller 22. Therefore, the return flow path 82a is formed so as to narrow toward the second impeller 22 in the axial direction of the rotating shaft 10.

The working fluid sucked from the first suction port 21a is accelerated by the first impeller 21 and discharged from the first discharge port 21b. After that, the working fluid is sucked into the second suction port 22a through the return flow path 82a, accelerated by the second impeller 22, and discharged from the second discharge port 22b. This compresses the working fluid. A flow path 83 is connected to the turbo compressor 1a, and the working fluid discharged from the second discharge port 22b is supplied to the outside of the turbo compressor 1a through the flow path 83.

The first bearing 41 is not limited to a specific bearing as long as it rotatably supports the rotating shaft 10. The first bearing 41 is, for example, a slide bearing. The first bearing 41 has, for example, a radial support portion 41a and a thrust support portion 41b. The radial support portion 41a supports the load of the rotating body including the rotation shaft 10 in the radial direction. The thrust support portion 41b supports the thrust force generated by the rotation of the first impeller 21 and the second impeller 22. When the first bearing 41 is a sliding bearing, the fluid that lubricates the first bearing 41 may be a lubricating oil or a fluid that is compatible with the working fluid. The fluid that lubricates the first bearing 41 may preferably be a fluid having the same composition as the working fluid. The first bearing 41 may be a rolling bearing such as a ball bearing or a magnetic bearing.

The second bearing 42 is not limited to a specific bearing as long as it rotatably supports the rotating shaft 10. The second bearing 42 is, for example, a slide bearing. The second bearing 42 is configured not to support the thrust force in, for example, the normal operation of the turbo compressor 1a. The second bearing 42 allows, for example, a dimensional change of about 1/1000 or more of the total length in the axial direction of the rotating shaft 10 with respect to the rotating body including the rotating shaft 10 in the axial direction of the rotating shaft 10. As a result, even if the rotary shaft 10 expands due to the temperature rise of the rotary shaft 10 during the operation of the turbo compressor 1a, the second bearing 42 can cope with the expansion of the rotary shaft 10 due to the expansion of the rotary shaft 10. The second bearing 42 may be a rolling bearing such as a ball bearing or a magnetic bearing.

An example of the operation and operation of the turbo compressor 1a will be described. In the space in front of the first suction port 21a of the first impeller 21, for example, a working fluid of a gas phase having a pressure of 1 kPa exists. When the rotary shaft 10 is rotated by the operation of the motor 70, the first impeller 21 and the second impeller 22 rotate together with the rotary shaft 10. As a result, the working fluid in the space in front of the first suction port 21a passes through the first suction port 21a, is accelerated by the first impeller 21, and is discharged from the first discharge port 21b. This compresses the working fluid. The pressure ratio of the working fluid in the first impeller 21 may be, for example, 2, and the pressure of the working fluid discharged from the first discharge port 21b may be 2 kPa. The working fluid discharged from the first discharge port 21b is sucked into the second suction port 22a through the return flow path 82a. For example, when the working fluid is water vapor, the specific volume of water vapor at a pressure of 2 kPa at room temperature is 67 m ³ / kg, and the return flow path 82a requires a large cross-sectional area. In the turbo compressor 1a, the first bearing 41 is arranged between the first impeller 21 and the second impeller 22 in the axial direction of the rotating shaft 10. Therefore, the rotary shaft 10 originally has a length for arranging the first bearing 41 between the first impeller 21 and the second impeller 22. In the turbo compressor 1a, since the first bearing 41 overlaps with the return flow path 82a in the axial direction of the rotary shaft 10, the cross-sectional area of the return flow path 82a is suppressed while the extension of the length of the rotary shaft 10 in the axial direction is suppressed. Is easy to increase. Therefore, the natural frequency based on the bending rigidity of the rotating shaft 10 tends to be high. As a result, according to the turbo compressor 1a, it is possible to prevent resonance from occurring due to the natural frequency based on the bending rigidity of the rotating shaft 10 and the rotating number of the rotating shaft 10 becoming close to each other.

For example, a turbo compressor 1a can be used to provide a refrigeration cycle device. As shown in FIG. 2, the refrigeration cycle device 100 includes an evaporator 30, a turbo compressor 1a, and a condenser 50. The evaporator 30 produces a vapor phase refrigerant. The turbo compressor 1a compresses the gas phase refrigerant generated in the evaporator 30 as a working fluid. The condenser 50 condenses the gas phase refrigerant compressed by the turbo compressor 1a. According to the refrigeration cycle device 100, the vapor phase refrigerant generated in the evaporator 30 can be compressed while the rotation stability of the rotation shaft 10 of the turbo compressor 1a is high. The refrigeration cycle device 100 can function as, for example, an air conditioner.

The evaporator 30 stores, for example, a liquid phase refrigerant inside the evaporator 30. The condenser 50 stores, for example, a liquid phase refrigerant inside the condenser 50. In the refrigeration cycle apparatus 100, at least one of the liquid phase refrigerant stored in the evaporator 30 and the liquid phase refrigerant stored in the condenser 30 is supplied to the first bearing 41. In this case, for example, at least one of the liquid phase refrigerant stored in the evaporator 30 and the liquid phase refrigerant stored in the condenser 50 can be used for lubrication or cooling of the first bearing 41.

As shown in FIG. 2, the refrigeration cycle device 100 includes, for example, a main circuit 80, a first circulation circuit 31, and a second circulation circuit 51. The main circuit 80 is a circuit in which the evaporator 30, the turbo compressor 1a, and the condenser 50 are connected in this order. The internal space of the evaporator 30 and the internal space of the casing 60 of the turbo compressor 1a are communicated with each other by a flow path 81. The internal space of the casing 60 of the turbo compressor 1a and the internal space of the condenser 50 are communicated with each other by the flow path 83. The internal space of the condenser 50 and the internal space of the evaporator 30 are communicated with each other by the flow path 84.

The first circulation circuit 31 has a first pump 35 and a first heat exchanger 33. In the first circulation circuit 31, the working fluid of the liquid stored in the evaporator 30 is supplied to the first heat exchanger 33 by the first pump 35, and the working fluid absorbed by the first heat exchanger 33 is supplied to the evaporator 30. It is configured to go back. In the first circulation circuit 31, the inlet of the evaporator 30 and the first pump 35 is connected by the flow path 31a. The outlet of the first pump 35 and the inlet of the first heat exchanger 33 are connected by a flow path 31b. The outlet of the first heat exchanger 33 and the evaporator 30 are connected by a flow path 31c.

The second circulation circuit 51 includes a second pump 55 and a second heat exchanger 53. In the second circulation circuit 51, the working fluid of the liquid stored in the condenser 50 is supplied to the second heat exchanger 53 by the second pump 55, and the working fluid radiated by the second heat exchanger 53 is supplied to the condenser 50. It is configured to go back. In the second circulation circuit 51, the condenser 50 and the inlet of the second pump 55 are connected by a flow path 51a. The outlet of the second pump 55 and the inlet of the second heat exchanger 53 are connected by a flow path 51b. The outlet of the second heat exchanger 53 and the condenser 50 are connected by a flow path 51c.

In the refrigeration cycle apparatus 100, for example, the liquid phase refrigerant stored in the evaporator 30 is used as a lubricating liquid to be supplied to the first bearing 41 and the second bearing 42. In the refrigeration cycle apparatus 100, for example, the liquid phase refrigerant stored in the condenser 50 may be used as the lubricating liquid to be supplied to the first bearing 41 and the second bearing 42. The liquid phase refrigerant supplied to the first bearing 41 and the second bearing 42 is returned to the evaporator 30 or the condenser 50.

The turbo compressor 1a can be changed from various viewpoints. For example, the turbo compressor 1a may be modified as in the turbo compressor 1b shown in FIG. The turbo compressor 1b is configured in the same manner as the turbo compressor 1a except for a portion to be described in particular. The same components as those of the turbo compressor 1a or the corresponding components of the turbo compressor 1b are designated by the same reference numerals, and detailed description thereof will be omitted. The description of the turbo compressor 1a also applies to the turbo compressor 1b, as long as there is no technical conflict.

As shown in FIG. 3, the turbo compressor 1b further includes a third impeller 23. The third impeller 23 is arranged at a position away from the first bearing 41 in the axial direction of the rotating shaft 10 and is fixed to the rotating shaft 10. The second impeller 22 is arranged between the first impeller 21 and the third impeller 23. According to the turbo compressor 1b, it is easy to realize operation at a high pressure ratio by the third impeller 23. In addition, in the turbo compressor 1b, the diameter of the rotating shaft 10 at the fixed position of the third impeller 23 is equal to or larger than the diameter of the rotating shaft 10 at the fixed position of the second impeller 22. As a result, the rotating shaft 10 tends to have a large diameter near the center in the axial direction, and the bending rigidity of the rotating shaft 10 tends to increase. As a result, it is possible to prevent a decrease in the natural frequency based on the bending rigidity of the rotating shaft 10, and prevent resonance from occurring due to the natural frequency based on the bending rigidity of the rotating shaft 10 and the rotating frequency of the rotating shaft 10 becoming close to each other. can.

The third impeller 23 is fixed to the rotating shaft 10 between the second impeller 22 and the rotor 71, for example, in the axial direction of the rotating shaft 10. In this case, the rotational stability of the rotating shaft 10 can be improved with the rotor 71 of the motor 70 fixed to the rotating shaft 10. The center of the rotating shaft 10 in the axial direction is located, for example, between the second impeller 22 and the rotor 71.

The third impeller 23 typically has a third suction port 23a into which the working fluid is sucked and a third discharge port 23b in which the working fluid is discharged. The third suction port 23a is opened in the same direction as the opening direction of the first suction port 21a and the second suction port 22a, for example. The third impeller 23 constitutes, for example, a centrifugal compression mechanism together with the first impeller 21 and the second impeller 22. The outer diameter of the portion forming the third suction port 23a of the third impeller 23 is smaller than, for example, the outer diameter of the portion forming the third discharge port 23b of the third impeller 23. The third suction port 23a is opened, for example, in front of the third impeller 23. The third discharge port 23b is open to the outside in the radial direction of the third impeller 23.

The turbo compressor 1b further includes, for example, a return flow path 82b. The return flow path 82b is a flow path that guides the working fluid from the second discharge port 22b to the third suction port 23a. As a result, the working fluid having a small specific volume compressed through the first impeller 21 and the second impeller 22 is guided to the third impeller 23. Therefore, the third impeller 23 can be manufactured so that the width of the working fluid flow path in the third impeller 23 is narrower than the width of the working fluid flow path in the first impeller 21.

The turbo compressor according to the present disclosure can prevent resonance due to a decrease in the natural frequency based on the bending rigidity of the rotating shaft, and can be applied to applications of a turbo compressor for an air conditioner, a chiller, and a thermal cycle power generation system.

1a, 1b Turbo compressor 10 Rotating shaft 11 One end 21 First impeller 21a First suction port 21b First discharge port 22 Second impeller 22a Second suction port 22b Second discharge port 23 Third impeller 30 Evaporator 41 First bearing 42 Second bearing 50 Condenser 70 Motor 71 Rotor 82a Return flow path 100 Refrigeration cycle device

Claims (8)

The axis of rotation and
A first impeller fixed to the rotating shaft and having a first suction port for sucking the working fluid and a first discharge port for discharging the working fluid.
A second impeller fixed to the rotating shaft and having a second suction port for sucking the working fluid and a second discharge port for discharging the working fluid.
A first bearing, which is arranged between the first impeller and the second impeller in the axial direction of the rotation axis and rotatably supports the rotation axis,
A return flow path for guiding the working fluid from the first discharge port to the second suction port is provided.
The first suction port and the second suction port are open in the same direction.
Turbo compressor. The turbo compressor according to claim 1, wherein all of the region where the first bearing exists in the axial direction overlaps with the region where the return flow path exists in the axial direction. The turbo compressor according to claim 1 or 2, wherein the working fluid having a saturated vapor pressure of atmospheric pressure or less at room temperature is accelerated and compressed. A second bearing, which is arranged at a position farther from the first impeller than the first bearing in the axial direction and rotatably supports the rotating shaft,
Further comprising a motor having a rotor fixed to the rotating shaft between the first bearing and the second bearing in the axial direction.
The turbo compressor according to any one of claims 1 to 3. It has a first suction port and a third suction port that opens in the same direction as the second suction port, is arranged at a position away from the first bearing in the axial direction, and is fixed to the rotating shaft. Yes, with a third impeller
The second impeller is arranged between the first impeller and the third impeller.
The turbo compressor according to any one of claims 1 to 4, wherein the diameter of the rotating shaft at the fixed position of the third impeller is equal to or larger than the diameter of the rotating shaft at the fixed position of the second impeller. A second bearing, which is arranged at a position farther from the first impeller than the first bearing in the axial direction and rotatably supports the rotating shaft,
Further comprising a motor having a rotor fixed to the rotating shaft between the first bearing and the second bearing in the axial direction.
The turbo compressor according to claim 5, wherein the third impeller is fixed between the second impeller and the rotor in the axial direction. An evaporator that produces a vapor phase refrigerant and
The turbo compressor according to any one of claims 1 to 6, wherein the gas phase refrigerant generated in the evaporator is compressed as the working fluid.
A condenser for condensing the gas phase refrigerant compressed by the turbo compressor.
Refrigeration cycle equipment. The evaporator stores a liquid phase refrigerant inside the evaporator and stores the liquid phase refrigerant inside the evaporator.
The condenser stores a liquid phase refrigerant inside the condenser.
At least one of the liquid phase refrigerant stored in the evaporator and the liquid phase refrigerant stored in the condenser is supplied to the first bearing.
The refrigeration cycle apparatus according to claim 7.

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