US20150300697A1

US20150300697A1 - Turbomachine and refrigeration cycle apparatus

Info

Publication number: US20150300697A1
Application number: US14/680,442
Authority: US
Inventors: Mamoru Nishibu; Hidetoshi Taguchi; Akira Hiwata; Tadayoshi Shoyama; Kazuyuki Kouda
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2014-04-18
Filing date: 2015-04-07
Publication date: 2015-10-22
Also published as: EP2933498B1; CN105004083A; EP2933498A1; JP2015212545A

Abstract

A turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature includes a rotation shaft and a bearing for supporting the rotation shaft. The rotation shaft includes a lubricant supply passage for supplying the refrigerant as a lubricant that travels smoothly between the rotation shaft and the bearing. The lubricant supply passage includes a main passage and a sub-passage. The main passage extends from an inlet located at an end of the rotation shaft in an axial direction of the rotation shaft. The sub-passage diverges from the main passage and extends to an outlet located in a side surface of the rotation shaft.

Description

BACKGROUND

1. Technical Field
The present disclosure relates to a turbomachine and particularly relates to a turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature specified as 20° C.±15° C. in JIS Z8703 of Japanese Industrial Standards (JIS), which is pressure lower than atmospheric pressure when measured as absolute pressure.
2. Description of the Related Art
Conventionally, refrigeration cycle apparatuses that use chlorofluorocarbon (CFC) refrigerants or alternative CFC refrigerants have been widely used. However, such refrigerants cause problems including destruction of the ozone layer and global warming. Thus, refrigeration cycle apparatuses that use water as refrigerants capable of greatly reducing loads to the global environment are proposed.
For example, as illustrated in FIG. 12, International Publication No. 2010/010925 describes a refrigerator 300 that includes a compressor 301, an evaporator 302, a condenser 304, a cooling tower 316, and a cooling water pump 318. In the refrigerator 300, water is used as a refrigerant. The compressor 301 includes a rotation shaft 310, an impeller 312, and a bearing 320. In the compressor 301, water is supplied to the bearing 320 as a lubricant. Specifically, the discharge pressure of the cooling water pump 318 is utilized to carry part of the cooling water supplied to the condenser 304 to the bearing 320. The refrigerator described in International Publication No. 2010/010925 is susceptible of increasing reliability of the compressor.

SUMMARY

One non-limiting and exemplary embodiment provides a highly reliable turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature.
In one general aspect, the techniques disclosed here feature a turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the turbomachine including a rotation shaft and a bearing for supporting the rotation shaft, where the rotation shaft includes a lubricant supply passage that includes a main passage extending from an inlet located at an end of the rotation shaft in an axial direction of the rotation shaft, and one of more sub-passage that divere from the main passage and that extend to an outlet located in a side surface of the rotation shaft, and the lubricant supply passage supplies the refrigerant to a portion between the rotation shaft and the bearing.
Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of a turbomachine according to a first embodiment;

FIG. 2 is a cross-sectional diagram of a rotation shaft along line II-II in FIG. 1;

FIG. 3 is a cross-sectional diagram of a rotation shaft according to a variation;

FIG. 4 is a cross-sectional diagram of a rotation shaft according to another variation;

FIG. 5 is a cross-sectional diagram of a rotation shaft and a bearing according to still another variation;

FIG. 6 is a cross-sectional diagram of a rotation shaft along line VI-VI in FIG. 5;

FIG. 7 is a cross-sectional diagram of a rotation shaft and a bearing according to still another variation;

FIG. 8 is a cross-sectional diagram of a rotation shaft and a bearing according to still another variation;

FIG. 9 is a configuration diagram illustrating an example of a refrigeration cycle apparatus that includes the turbomachine in FIG. 1;

FIG. 10 is a configuration diagram illustrating another example of a refrigeration cycle apparatus that includes the turbomachine in FIG. 1;

FIG. 11 is a cross-sectional diagram illustrating a condensation mechanism according to a variation; and

FIG. 12 is a configuration diagram illustrating a conventional refrigerator.

DETAILED DESCRIPTION

[Underlying Knowledge Forming Basis of the Present Disclosure]

The present inventors have conducted study of a turbomachine referred to as the “turbomachine in the study stage” hereinafter, which is a turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature specified as 20° C.±15° C. in JIS Z8703, which is pressure lower than atmospheric pressure when measured as absolute pressure. The turbomachine in the study stage includes a rotation shaft and a bearing that supports the rotation shaft, and includes a lubricant supply passage that supplies a refrigerant as a lubricant that travels smoothly between the rotation shaft and the bearing. As a result, the knowledge described below has been obtained.
In the turbomachine in the study stage, what is supplied to the bearing as the lubricant is not a “lubricating oil” but “water”, which is the refrigerant. Thus, the turbomachine in the study stage has been favorable in the points described below. That is, when a “lubricating oil” is supplied to the bearing as the lubricant, the lubricating oil and the water are mixed and cause a suspension, and the performance of the lubrication considerably decreases. As another possibility, when the suspension flows out into the refrigeration cycle apparatus, the lubricating oil acts as thermal resistance and reduces the performance of the refrigeration cycle apparatus. In contrast, in the turbomachine in the study stage, “water”, which is the refrigerant, is supplied to the bearing as the lubricant. Accordingly, the above-mentioned problems caused by the suspension of the lubricating oil and the water may be prevented and the considerable decrease in the performance of the lubrication may be suppressed. In addition, the lubricant of the bearing may be disposed of more easily and the configurations of the turbomachine and the refrigeration cycle apparatus may be simplified.
However, the present inventors have found that the reliability of the turbomachine in the study stage is insufficient. The reasons are given as follows. In the refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the pressure inside the compressor is close to the saturated vapor pressure of the refrigerant. Thus, when the refrigerant of the refrigeration cycle apparatus is supplied to the bearing of the compressor as the lubricant, the refrigerant is already in a state in which the refrigerant easily evaporates. In particular, as regards slide bearings used in turbomachines, the peripheral speed of the rotation shaft of the turbomachine is high and the calorific amount is large. As the peripheral speed of the rotation shaft of the turbomachine increases, the pressure of the lubricant in a portion in which the gap between the supported surface of the rotation shaft and the slide surface of the bearing widens becomes a negative pressure more easily. Accordingly, as the number of rotations of the rotation shaft increases, cavitation is more likely to occur in the refrigerant supplied as the lubricant. As a result, the amount of the lubricant of the bearing is insufficient and the reliability of the compressor is decreased.
Thus, the present inventors have considered applying sufficiently high static pressure to the refrigerant supplied to the bearing as the lubricant so as to suppress the evaporation of the refrigerant and the occurrence of the cavitation in the bearing. For example, utilization of the discharge pressure of the cooling water pump has been considered so as to supply water to the lubricant supply passage as the lubricant. It has been found however that arranging a cooling water pump with high performance is necessary so as to apply sufficiently high static pressure to the refrigerant supplied to the bearing as the lubricant and that the cost of the turbomachine increases accordingly.
Then, after careful review, the present inventors have focused on the point that when a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, such as water, is used as an operating fluid, the turbomachine needs the number of rotations that is very large as the number of rotations of a rotation body. That is, it is desired that the turbomachine in a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature as an operating fluid achieve the higher pressure ratio than the pressure ratio of the turbomachine in a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a positive pressure at ordinary temperature as an operating fluid. Thus, the turbomachine needs the number of rotations very large as the number of rotations of a rotation body. The present inventors have reached the idea that if the centrifugal force produced through the very large number of rotations is utilizable to apply pressure to the refrigerant, it may be possible to apply sufficiently high static pressure to the refrigerant supplied to the bearing as the lubricant without using a cooling water pump with high performance. On the basis of the aforementioned knowledge, the present inventors have conceived the present disclosure including the aspects described below.
A turbomachine according to a first aspect of the present disclosure is a turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the turbomachine including a rotation shaft and a bearing that supports the rotation shaft, where the rotation shaft includes a lubricant supply passage therein, the lubricant supply passage including a main passage that extends from an inlet located at an end of the rotation shaft in an axial direction of the rotation shaft, and one or more sub-passages that diverge from the main passage and that extend to an outlet located in a side surface of the rotation shaft, and while the rotation shaft rotates, the lubricant supply passage supplies the refrigerant to a portion where is located between the rotation shaft and the bearing.
According to the first aspect, with the rotation of the rotation shaft, the refrigerant as the lubricant is supplied to the bearing under pressure through the lubricant supply passage. Accordingly, the pressure of the refrigerant supplied as the lubricant increases and the evaporation of the refrigerant as the lubricant or the occurrence of the cavitation may be suppressed in the bearing. The turbomachine according to the first aspect is oriented toward a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, and includes the lubricant supply passage for supplying the refrigerant as the lubricant that travels smoothly between the rotation shaft and the bearing. As described above, when the refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature is used as an operating fluid, the turbomachine needs the number of rotations that is very large as the number of rotations of a rotation body. Thus, according to the first aspect, since the centrifugal force produced through the large number of rotations may be utilized to apply pressure to the refrigerant, high pressure may be applied to the lubricant supplied to the bearing through the lubricant supply passage. Accordingly, shortage of the lubricant in the bearing may be prevented and the reliability of the turbomachine may increase. In addition, the performance that an external pump of the turbomachine for supplying the refrigerant as the lubricant to the lubricant supply passage is desired to offer may be reduced and accordingly, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.
For example, when water is used in a refrigerator with a refrigerating ability of a 10 kW class as an operating fluid, the number of rotations of the rotation body in the turbomachine is very large, which is in a range from approximately 75 thousand to 90 thousand rpm. In this case, depending on the design, the pressure of the refrigerant liquid supplied between the rotation shaft and the bearing is in a range from approximately 0.5 to 1 MPaA. In contrast, when the turbomachine according to the first aspect is not used, that is, for example, the turbomachine in the study stage, in which the rotation shaft has no lubricant supply passage, is used, the discharge pressure of the external pump of the turbomachine is desired to be in a range from approximately 200 to 400 KPaA so as to suppress the evaporation of the refrigerant and the occurrence of cavitation in the bearing. In contrast, the discharge pressure of the external pump of the turbomachine according to the first aspect is in a range from approximately 50 to 80 KPaA. As described above, according to the first aspect, the performance that the external pump of the turbomachine is desired to offer may be reduced and accordingly, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.
The first aspect of the present disclosure is favorable, compared with the refrigerator 300 disclosed in International Publication No. 2010/010925 in the points described below.
For example, in the refrigerator 300, the discharge pressure of the cooling water pump 318 is utilized to carry water as the lubricant to the bearing 320 and the reliability of the compressor 301 depends on the performance of the cooling water pump 318. Depending on the performance of the cooling water pump 318, the pressure of the water supplied to the bearing 320 as the lubricant may be insufficient. In this case, the evaporation of the lubricant or the cavitation in the lubricant may occur and cause shortage of the amount of the lubricant in the bearing 320 and the reliability of the compressor 301 may be decreased accordingly. Since the cooling water pump 318 is desired to offer high performance so as to increase the reliability of the compressor 301, the cooling water pump 318 involves the high cost.
In contrast, the turbomachine according to the present disclosure includes the lubricant supply passage that includes the main passage extending from the inlet located at an end of the rotation shaft in the axial direction of the rotation shaft, and the sub-passage diverging from the main passage and extending to the outlet located in the side surface of the rotation shaft, and supplies the refrigerant as the lubricant traveling smoothly between the rotation shaft and the bearing. Thus, the centrifugal force produced through the rotation of the rotation shaft enables pressure to be applied to the refrigerant in the lubricant supply passage and accordingly, the refrigerant to which pressure is applied may be supplied between the rotation shaft and the bearing. That is, since the lubricant supply passage functions as a pump mechanism that utilizes the rotation of the rotation shaft, the occurrence of cavitation may be suppressed without using a cooling water pump that has high performance.
In a second aspect of the present disclosure, the sub-passage of the turbomachine according to the first aspect may intersect a central axis of the main passage and extend along a straight line perpendicular to the central axis. According to the second aspect, the rotation shaft may be processed easily in forming the sub-passage.
In a third aspect of the present disclosure, the outlet of the sub-passage of the turbomachine according to the first aspect may be located at a more backward position in a direction of rotation of the rotation shaft than a point at which a straight line intersects the side surface of the rotation shaft, the straight line connecting a central axis of the main passage and a center of an opening of the sub-passage on a side of the main passage. According to the third aspect, decrease in the pressure of the refrigerant as the lubricant is small while the refrigerant as the lubricant flows through the lubricant supply passage and cavitation is unlikely to occur in the flow of the refrigerant through the lubricant supply passage.
In a fourth aspect of the present disclosure, when viewed in an axial direction of the rotation shaft, the sub-passage of the turbomachine according to the first aspect or the third aspect may be expanded backward in the direction of rotation of the rotation shaft from a position in the sub-passage to the outlet, the position being located between an opening of the sub-passage on the side of the main passage and the outlet. According to the fourth aspect, decrease in the pressure of the refrigerant as the lubricant is small while the refrigerant as the lubricant flows through the lubricant supply passage and cavitation is unlikely to occur in the flow of the refrigerant through the lubricant supply passage
In a fifth aspect of the present disclosure, the lubricant supply passage of the turbomachine according to any one of the first to fourth aspects may include the plurality of sub-passages arranged in the axial direction of the rotation shaft. According to the fifth aspect, the amount of the refrigerant as the lubricant supplied to the bearing through the lubricant supply passage increases. Thus, the cooling ability of the bearing may be enhanced.
In a sixth aspect of the present disclosure, when the sub-passage is viewed from the direction perpendicular to the axial direction of the rotation shaft, a central axis of the sub-passage of the turbomachine according to any one of the first to fifth aspects may be tilted with respect to the central axis of the main passage in the axial direction of the rotation shaft. According to the sixth aspect, the outlet may be located at a position where the lubricant may be supplied suitably to the bearing while enhancing the performance to cool the rotation shaft by forming the main passage as long as possible. Occasionally, the outlet may be located at a position where the lubricant may be supplied suitably to the bearing while simplifying the processing of the rotation shaft by forming the main passage as short as possible.
In a seventh aspect of the present disclosure, the turbomachine according to any one of the first to sixth aspects may further include a storage portion that adjoins the bearing on the side of the inlet and stores the refrigerant as the lubricant, where the inlet located at the end of the rotation shaft may be soaked in the refrigerant stored in the storage portion as the lubricant. According to the seventh aspect, the bearing and the rotation shaft may be cooled by the lubricant stored in the storage portion.
A refrigeration cycle apparatus according to an eighth aspect of the present disclosure includes: a main circuit that circulates a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the main circuit including an evaporation mechanism that stores a refrigerant liquid and evaporates the refrigerant liquid, the turbomachine according to any one of the first to seventh aspects that is a compressor that compresses refrigerant vapor, and a condensation mechanism that condenses refrigerant vapor and stores a refrigerant liquid, the evaporation mechanism, the turbomachine, and the condensation mechanism being connected in named order; an evaporation-side circulation circuit that includes a heat-absorption-side liquid carrying pump and a heat-absorption heat exchanger, the heat-absorption-side liquid carrying pump causing the refrigerant liquid stored in the evaporation mechanism to be supplied to the heat-absorption heat exchanger, the refrigerant after heat absorption in the heat-absorption heat exchanger being returned to the evaporation mechanism; a condensation-side circulation circuit that includes a heat-radiation-side liquid carrying pump and a heat-radiation heat exchanger, the heat-radiation-side liquid carrying pump causing the refrigerant liquid stored in the condensation mechanism to be supplied to the heat-radiation heat exchanger, the refrigerant after heat radiation in the heat-radiation heat exchanger being returned to the condensation mechanism; and an upstream-side supply passage that diverges from the evaporation-side circulation circuit at a position downstream of an exit of the heat-absorption-side liquid carrying pump in the evaporation-side circulation circuit or diverges from the condensation-side circulation circuit at a position downstream of an exit of the heat-radiation-side liquid carrying pump in the condensation-side circulation circuit, and supplies the refrigerant to the lubricant supply passage.
According to the eighth aspect, since the refrigerant to which pressure is applied through the heat-absorption-side liquid carrying pump or the heat-radiation-side liquid carrying pump is supplied to the lubricant supply passage through the upstream-side supply passage, the pressure of the refrigerant as the lubricant supplied to the bearing may be further raised.
Embodiments of the present disclosure are described below with reference to the drawings. The description below relates to examples of the present disclosure and the present disclosure is not limited by the examples.

As illustrated in FIG. 1, a turbomachine 1 a includes a rotation shaft 10 a and a bearing 20. The turbomachine 1 a is a turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature. The turbomachine 1 a is typically a turbocompressor. The turbomachine 1 a is configured as a fluid machine of, for example, a centrifugal type, an axial-flow type, or a diagonal-flow type. The bearing 20 is a bearing for supporting the rotation shaft 10 a and is, for example, a slide bearing that supports the radial load of the rotation shaft 10 a. An impeller 12 is attached to the rotation shaft 10 a. The rotation shaft 10 a is connected to a motor, which is not illustrated. When the motor is driven, the rotation shaft 10 a and the impeller 12 rotate. Thus, the refrigerant of the refrigeration cycle apparatus is sucked into the turbomachine 1 a and discharged from the turbomachine 1 a after being compressed. The refrigerant is not limited in particular as long as the saturated vapor pressure of the refrigerant is a negative pressure at ordinary temperature, and examples of the refrigerant include a refrigerant that contains mainly water, alcohol, or ether. The turbomachine 1 a is operated at pressure near the saturated vapor pressure of the refrigerant of the refrigeration cycle apparatus. The pressure at the entrance of the turbomachine 1 a is in a range from, for example, 0.5 to 5 kPaA. The pressure at the exit of the turbomachine 1 a is in a range from, for example, 5 to 15 kPaA.
The rotation shaft 10 a includes a lubricant supply passage 30. The lubricant supply passage 30 is a passage for supplying the refrigerant of the refrigeration cycle apparatus as the lubricant that travels smoothly between the rotation shaft 10 a and the bearing 20. During the operation of the refrigeration cycle apparatus, the lubricant supply passage 30 is filled with the refrigerant of the refrigeration cycle apparatus liquid. The lubricant supply passage 30 includes a main passage 31 and a sub-passage 32. As illustrated in FIG. 1, the main passage 31 extends from an inlet 33 located at an end 11 of the rotation shaft 10 a in the axial direction of the rotation shaft 10 a. The sub-passages 32 diverge from the main passage 31 and extend to outlets 35 located in the side surface of the rotation shaft 10 a. As illustrated in FIG. 1, the sub-passage 32 is located so that the outlet 35 faces the slide surface of the bearing 20. In FIG. 2, although the lubricant supply passage 30 includes four sub-passages as the sub-passages 32 positioned in the circumferential direction of the rotation shaft 10 a, the lubricant supply passage 30 may include one sub-passage 32 or include two, three, five, or more sub-passages 32 positioned in the circumferential direction of the rotation shaft 10 a.
During the operation of the turbomachine 1 a, the rotation shaft 10 a rotates at high speed. The centrifugal force produced through the rotation of the rotation shaft 10 a causes the refrigerant of the refrigeration cycle apparatus in the lubricant supply passage 30 to be supplied between the rotation shaft 10 a and the bearing 20 while pressure is being applied to the refrigerant of the refrigeration cycle apparatus in the lubricant supply passage 30. Specifically, the refrigerant liquid of the refrigeration cycle apparatus that flows into the main passage 31 from the inlet 33 flows through the main passage 31 in the axial direction. After that, the refrigerant liquid is guided to the sub-passage 32 and flows through the sub-passage 32 and out from the outlet 35. The refrigerant liquid supplied between the rotation shaft 10 a and the bearing 20 travels smoothly between the rotation shaft 10 a and the bearing 20. In this manner, the lubricant supply passage 30 functions as a pump mechanism that utilizes the rotation of the rotation shaft 10 a and the refrigerant liquid as the lubricant is supplied between the rotation shaft 10 a and the bearing 20 at predetermined pressure. As described above, the turbomachine 1 a is operated at pressure near the saturated vapor pressure of the refrigerant of the refrigeration cycle apparatus. Since the lubricant supply passage 30 functions as a pump mechanism that utilizes the rotation of the rotation shaft 10 a, the pressure of the refrigerant liquid supplied between the rotation shaft 10 a and the bearing 20 is high. The evaporation of the refrigerant liquid supplied between the rotation shaft 10 a and the bearing 20 as the lubricant or the occurrence of cavitation in the lubricant may be suppressed accordingly. In addition, as the number of rotations of the rotation shaft 10 a increases, the pressure of the lubricant supplied to the bearing 20 through the lubricant supply passage 30 becomes higher. Thus, shortage of the lubricant in the bearing 20 may be prevented and the turbomachine 1 a has high reliability.
As long as the rotation shaft 10 a of the turbomachine 1 a rotates, the lubricant may be supplied to the bearing 20. For example, even when power failure or the like stops the supply of power to the motor that drives the rotation shaft 10 a, not illustrated, the lubricant may be supplied to the bearing 20 as long as the rotation shaft 10 a rotates and thus, the rotation shaft 10 a may be stopped safely.
The turbomachine 1 a includes a casing 50. A storage portion 40 is included in the casing 50. That is, the turbomachine 1 a further includes the storage portion 40. The storage portion 40 is a space for storing the lubricant. The storage portion 40 stores the lubricant. The storage portion 40 adjoins the bearing 20 on the side of the inlet 33. The end 11 of the rotation shaft 10 a is soaked in the lubricant stored in the storage portion 40. The casing 50 is provided with a supply hole 41 and a discharge hole 42. The refrigerant in a specific location of the refrigeration cycle apparatus is supplied to the storage portion 40 through the supply hole 41 using, for example, an external pump of the turbomachine 1 a, and stored in the storage portion 40 as the lubricant. The refrigerant is discharged from the storage portion 40 through the discharge hole 42 and is returned to the specific location of the refrigeration cycle apparatus. The lubricant stored in the storage portion 40 is continuously supplied to the bearing 20 through the lubricant supply passage 30 because of the rotation of the rotation shaft 10 a. Further, the lubricant stored in the storage portion 40 cools the bearing 20 and the rotation shaft 10 a.
As described above, the refrigeration cycle apparatus is desirably provided with a pump outside the turbomachine 1 a so as to supply the refrigerant as the lubricant from a specific location of the refrigeration cycle apparatus to the lubricant supply passage 30. In this case, it is desirable to set the discharge pressure of the external pump so that the pressure of the refrigerant at the inlet 33 is equal to or more than the saturated vapor pressure. Thus, the occurrence of cavitation may be suppressed in the lubricant supply passage 30 and shortage of the amount of the lubricant to be supplied to the bearing 20 may be prevented. Since the refrigerant as the lubricant is supplied between the rotation shaft 10 a and the bearing 20 at high pressure by passing through the lubricant supply passage 30, the performance that the external pump is desired to offer may be reduced. Thus, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.
For example, when water is used in a refrigerator with a refrigerating ability of a 10 kW class as an operating fluid, the number of rotations of the rotation body in the turbomachine is very large, which is in a range from approximately 75 thousand to 90 thousand rpm. In this case, depending on the design, the pressure of the refrigerant liquid supplied between the rotation shaft and the bearing is in a range from approximately 0.5 to 1 MPaA. In contrast, when the turbomachine according to the present disclosure is not used, that is, for example, the turbomachine in the study stage, in which the rotation shaft has no lubricant supply passage, is used, the discharge pressure of the external pump of the turbomachine is desired to be in a range from approximately 200 to 400 KPaA so as to suppress the evaporation of the refrigerant and the occurrence of cavitation in the bearing. In contrast, the discharge pressure of the external pump of the turbomachine according to the present embodiment is in a range from approximately 50 to 80 KPaA. As described above, according to the present embodiment, the performance that the external pump of the turbomachine is desired to offer may be reduced and accordingly, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.
As illustrated in FIG. 2, the sub-passage 32 is located so that a distance between the center of an opening 34 of the sub-passage 32 on the side of the main passage 31 and the center of the outlet 35 is the shortest. The sub-passage 32 is located so as to extend straight. The sub-passage 32 is located so that a straight line that connects the center of the opening 34 of the sub-passage 32 on the side of the main passage 31 and the center of the outlet 35 passes through a specific point on the central axis of the main passage 31 and is orthogonal to the central axis of the main passage 31. Accordingly, the rotation shaft 10 a may be processed easily in forming the sub-passage 32.

[Variations]

The above-described turbomachine 1 a may be changed in various terms. Variations of the turbomachine 1 a are described below. The same reference alphanumeric characters are given to the elements in the variations that are the same as or correspond to the elements in the above-described turbomachine 1 a, and the detailed description of such elements is omitted.
The rotation shaft 10 a of the turbomachine 1 a may be changed like a rotation shaft 10 b illustrated in FIG. 3. In the rotation shaft 10 b, sub-passages 32 are located so that outlets 35 are located in more backward positions in the direction of the rotation of the rotation shaft 10 b than a point A. The point A is a point at which a straight line Q, which connects a central axis P of a main passage 31 and a center 34 c of an opening 34 of the sub-passage 32 on the side of the main passage 31 and is perpendicular to the central axis P of the main passage 31 and a side surface of the rotation shaft 10 a intersect. In FIG. 3, the rotation shaft 10 b rotates clockwise during the operation of the turbomachine 1 a. There are possibilities that when the refrigerant flows from the main passage 31 into the sub-passage 32, the pressure of the refrigerant as the lubricant may decrease as the flow of the refrigerant changes and cavitation may be caused in the flow of the refrigerant through a lubricant supply passage 30. By forming the sub-passage 32 in the rotation shaft 10 b as described above, change in the velocity of the flow of the refrigerant may be made small and decrease in the pressure of the refrigerant as the lubricant may be suppressed when the refrigerant flows from the main passage 31 into the sub-passage 32. Accordingly, cavitation is unlikely to occur in the flow of the refrigerant through the lubricant supply passage 30.
The rotation shaft 10 a of the turbomachine 1 a may be changed like a rotation shaft 10 c illustrated in FIG. 4. In the rotation shaft 10 c, sub-passages 32 are viewed from the side of an inlet 33 in the axial direction of the rotation shaft 10 c. Each of the sub-passages 32 bends backward in the direction in which the rotation shaft 10 c rotates from a position in the sub-passage 32 to an outlet 35, and the position is located between an opening 34 of the sub-passage 32 on the side of a main passage 31 and the outlet 35. In FIG. 4, the rotation shaft 10 c rotates clockwise during the operation of the turbomachine 1 a. By forming the sub-passage 32 as described above, change in the velocity of the flow of the refrigerant may be made small and decrease in the pressure of the refrigerant as the lubricant may be suppressed when the refrigerant flows through the sub-passage 32. Accordingly, cavitation is unlikely to occur in the flow of the refrigerant through a lubricant supply passage 30. As illustrated in FIG. 4, the sub-passage 32 is located so that the passage cross-sectional area of the sub-passage 32 is enlarged from the position at which the sub-passage 32 bends toward the outlet 35. Thus, the refrigerant as the lubricant in the sub-passage 32 may flow out easily through the outlet 35.
The rotation shaft 10 a of the turbomachine 1 a may be changed like a rotation shaft 10 d illustrated in FIGS. 5 and 6. As illustrated in FIG. 5, in the rotation shaft 10 d, a lubricant supply passage 30 includes a plurality of sub-passages 32 arranged in the axial direction of the rotation shaft 10 d. Accordingly, the amount of the refrigerant as the lubricant supplied to the bearing 20 through the lubricant supply passage 30 increases. In addition, unevenness in the amount of the refrigerant supplied to the bearing 20 in the axial direction of the rotation shaft 10 d may be suppressed. In this case, as illustrated in FIGS. 5 and 6, the lubricant supply passage 30 includes a plurality of sub-passage groups (two in the example of FIGS. 5 and 6), each of which includes the plurality of sub-passages 32 (four in the example of FIGS. 5 and 6) arranged in the circumferential direction of the rotation shaft 10 d. The plurality of sub-passage groups are arranged in the axial direction of the rotation shaft 10 d. As illustrated in FIG. 6, the sub-passages 32 that belong to one of the sub-passage groups arranged in the axial direction of the rotation shaft 10 d are shifted in the circumferential direction of the rotation shaft 10 d from the positions of the sub-passages 32 that belong to another one of the sub-passage groups. Specifically, the sub-passages 32 that belong to one of the sub-passage groups arranged in the axial direction of the rotation shaft 10 d are shifted in the circumferential direction of the rotation shaft 10 d from the positions of the sub-passages 32 that belong to another one of the sub-passage groups by approximately 45°. As a result, unevenness in the amount of the refrigerant supplied to the bearing 20 in the circumferential direction of the rotation shaft 10 d may be suppressed. In the rotation shaft 10 d, the sub-passages 32 may be located as illustrated in FIG. 3 or 4.
The rotation shaft 10 a of the turbomachine 1 a may be changed like a rotation shaft 10 e illustrated in FIG. 7 or a rotation shaft 10 f illustrated in FIG. 8. In the rotation shaft 10 e or the rotation shaft 10 f, sub-passages 32 are located so that a central axis L of the sub-passage 32 is tilted in the axial direction of the rotation shaft 10 e or the rotation shaft 10 f with respect to a central axis P of a main passage 31. The sub-passages 32 are located so that in the axial direction of the rotation shaft 10 e, an outlet 35 is closer to an inlet 33 than an opening 34 of the sub-passage 32 on the side of the main passage 31 is. By forming the sub-passages 32 in this manner, the main passage 31 may be located as long as possible and the performance of cooling the rotation shaft 10 e may be enhanced while the outlets 35 may be located at positions desirable for supplying the lubricant to the bearing 20. For example, the outlets 35 may be located near the center of the bearing 20 in the axial direction of the rotation shaft 10 e.
In the axial direction of the rotation shaft 10 f, the sub-passages 32 are located so that an outlet 35 is farther away from an inlet 33 than an opening 34 of the sub-passage 32 on the side of the main passage 31 is. By forming the sub-passages 32 in this manner, even when the main passage 31 is located as short as possible and the processing of the rotation shaft 10 f is simplified, the outlets 35 may be located at positions desirable for supplying the lubricant to the bearing 20. For example, the outlets 35 may be located near the center of the bearing 20 in the axial direction of the rotation shaft 10 f.

A refrigeration cycle apparatus that includes the above-described turbomachine 1 a is described below.
As illustrated in FIG. 9, a refrigeration cycle apparatus 100 a includes a main circuit 5, an evaporation-side circulation circuit 6, a condensation-side circulation circuit 7, and an upstream-side supply passage 91 a. The main circuit 5 includes an evaporation mechanism 2, the turbomachine 1 a, and a condensation mechanism 4. The evaporation mechanism 2 stores a refrigerant liquid and evaporates the refrigerant liquid. The evaporation mechanism 2 is made up of, for example, a container with heat insulating properties and resistance to pressure. The turbomachine 1 a is a compressor that compresses refrigerant vapor. The condensation mechanism 4 condenses the refrigerant vapor and stores the refrigerant liquid. The condensation mechanism 4 is made up of, for example, a container with heat insulating properties and resistance to pressure. The main circuit 5 is a circuit in which the evaporation mechanism 2, the turbomachine 1 a, and the condensation mechanism 4 are connected in named order. The exit of the evaporation mechanism 2 and the entrance of the turbomachine 1 a are connected through a passage 5 a. The exit of the turbomachine 1 a and the entrance of the condensation mechanism 4 are connected through a passage 5 b. The exit of the condensation mechanism 4 and the entrance of the evaporation mechanism 2 are connected through a passage 5 c. The main circuit 5 is filled with, for example, a refrigerant that contains mainly water, alcohol, or ether, and kept in a state of a negative pressure lower than atmospheric pressure. The refrigeration cycle apparatus 100 a is included in, for example, air conditioning equipment for air cooling purpose.
The evaporation-side circulation circuit 6 includes a heat-absorption-side liquid carrying pump 61 and a heat-absorption heat exchanger 62. The evaporation-side circulation circuit 6 is configured so that the refrigerant liquid stored in the evaporation mechanism 2 is supplied to the heat-absorption heat exchanger 62 with the heat-absorption-side liquid carrying pump 61 and the refrigerant after heat absorption in the heat-absorption heat exchanger 62 is returned to the evaporation mechanism 2. In the evaporation-side circulation circuit 6, the evaporation mechanism 2 and the entrance of the heat-absorption-side liquid carrying pump 61 are connected through a passage 6 a. The exit of the heat-absorption-side liquid carrying pump 61 and the entrance of the heat-absorption heat exchanger 62 are connected through a passage 6 b. Further, the exit of the heat-absorption heat exchanger 62 and the evaporation mechanism 2 are connected through a passage 6 c. The refrigerant liquid in the evaporation mechanism 2, which has a temperature decreased as a result of the evaporation of the refrigerant in the evaporation mechanism 2, is carried by the heat-absorption-side liquid carrying pump 61 to the heat-absorption heat exchanger 62 under pressure. The refrigerant liquid is heated in the heat-absorption heat exchanger 62 and returned to the evaporation mechanism 2. The passage 6 c may be provided with a pressure reducing mechanism for reducing the pressure of the refrigerant after the heat absorption in the heat-absorption heat exchanger 62. The heat-absorption heat exchanger 62 cools indoor air through the heat absorption of the refrigerant in the heat-absorption heat exchanger 62.
The condensation-side circulation circuit 7 includes a heat-radiation-side liquid carrying pump 71 and a heat-radiation heat exchanger 72. The condensation-side circulation circuit 7 is configured so that the refrigerant liquid stored in the condensation mechanism 4 is supplied to the heat-radiation heat exchanger 72 with the heat-radiation-side liquid carrying pump 71 and the refrigerant after heat radiation in the heat-radiation heat exchanger 72 is returned to the condensation mechanism 4. In the condensation-side circulation circuit 7, the condensation mechanism 4 and the entrance of the heat-radiation-side liquid carrying pump 71 are connected through a passage 7 a. The exit of the heat-radiation-side liquid carrying pump 71 and the entrance of the heat-radiation heat exchanger 72 are connected through a passage 7 b. The exit of the heat-radiation heat exchanger 72 and the condensation mechanism 4 are connected through a passage 7 c. The refrigerant cooled indirectly in the heat-radiation heat exchanger 72 is guided to the condensation mechanism 4 through the passage 7 c. Thus, the refrigerant vapor compressed in the turbomachine 1 a is cooled and condensed. The refrigerant liquid that has a temperature raised through the condensation in the condensation mechanism 4 is carried to the heat-radiation heat exchanger 72 with the heat-radiation-side liquid carrying pump 71 under pressure and cooled indirectly in the heat-radiation heat exchanger 72, and then returned to the condensation mechanism 4. In the heat-radiation heat exchanger 72, the refrigerant radiates heat against outdoor air.
The upstream-side supply passage 91 a diverges from the evaporation-side circulation circuit 6 at a position downstream of the exit of the heat-absorption-side liquid carrying pump 61 in the evaporation-side circulation circuit 6. The upstream-side supply passage 91 a is a passage for supplying the refrigerant to the lubricant supply passage 30 of the turbomachine 1 a. For example, the upstream-side supply passage 91 a diverges from the evaporation-side circulation circuit 6 at a position between the exit of the heat-absorption-side liquid carrying pump 61 and the entrance of the heat-absorption heat exchanger 62 in the evaporation-side circulation circuit 6. Further, the upstream-side supply passage 91 a is connected to the turbomachine 1 a so as to communicate with the lubricant supply passage 30. For example, the refrigerant that travels through the upstream-side supply passage 91 a passes through the supply hole 41 to be supplied to the storage portion 40. As described above, the refrigerant to which pressure has been applied with the heat-absorption-side liquid carrying pump 61 passes through the upstream-side supply passage 91 a to be supplied to the lubricant supply passage 30 as the lubricant. In this case, the discharge pressure of the heat-absorption-side liquid carrying pump 61 is desirably set so that the pressure of the refrigerant at the inlet 33 of the lubricant supply passage 30 is equal to or more than the saturated vapor pressure. When the upstream-side supply passage 91 a diverges from the evaporation-side circulation circuit 6 at a position between the exit of the heat-absorption-side liquid carrying pump 61 and the entrance of the heat-absorption heat exchanger 62 in the evaporation-side circulation circuit 6, the refrigerant with a relatively low temperature may be supplied to the lubricant supply passage 30. Thus, the lubricant may enhance the ability of cooling the rotation shaft 10 a and the bearing 20.
The upstream-side supply passage 91 a may diverge from the evaporation-side circulation circuit 6 at a position between the exit of the heat-absorption heat exchanger 62 in the evaporation-side circulation circuit 6 and the evaporation mechanism 2. Also in this case, part of the refrigerant of the refrigeration cycle apparatus 100 a may be supplied to the lubricant supply passage 30 as the lubricant.
The refrigeration cycle apparatus 100 a further includes a return passage 92 a. The return passage 92 a is a passage for returning the refrigerant supplied to the lubricant supply passage 30 through the upstream-side supply passage 91 a to the main circuit 5. For example, the return passage 92 a communicates with the storage portion 40 via the discharge hole 42. Further, the return passage 92 a is connected to the evaporation mechanism 2. The refrigerant stored in the storage portion 40 is guided to the return passage 92 a through the discharge hole 42 to flow through the return passage 92 a and is returned into the evaporation mechanism 2. The return passage 92 a may be connected to the condensation mechanism 4 so as to return the refrigerant to the condensation mechanism 4.
The refrigeration cycle apparatus 100 a may be included in, for example, air conditioning equipment where cooling and heating modes are switchable. In this case, an indoor heat exchanger placed indoors and an outdoor heat exchanger placed outdoors are connected to the evaporation mechanism 2 and the condensation mechanism 4 via a four-way valve. In the cooling mode, the indoor heat exchanger functions as the heat-absorption heat exchanger 62 and the outdoor heat exchanger functions as the heat-radiation heat exchanger 72. In the heating mode, the indoor heat exchanger functions as the heat-radiation heat exchanger 72 and the outdoor heat exchanger functions as the heat-absorption heat exchanger 62. The refrigeration cycle apparatus 100 a may be included in, for example, a chiller. For example, the heat-absorption heat exchanger 62 may cool gas other than air or liquid through the heat absorption of the refrigerant. For example, the heat-radiation heat exchanger 72 may heat gas other than air or liquid through the heat radiation of the refrigerant. The heat-absorption heat exchanger 62 and the heat-radiation heat exchanger 72 are not limited in particular as long as the heat-absorption heat exchanger 62 and the heat-radiation heat exchanger 72 are indirect heat exchangers.
The refrigeration cycle apparatus 100 a may be changed like a refrigeration cycle apparatus 100 b illustrated in FIG. 10. The refrigeration cycle apparatus 100 b has a configuration the same as the configuration of the refrigeration cycle apparatus 100 a unless otherwise described. The same reference alphanumeric characters are given to the elements in the refrigeration cycle apparatus 100 b that are the same as or correspond to the elements in the refrigeration cycle apparatus 100 a, and the detailed description of such elements is omitted. The description of the refrigeration cycle apparatus 100 a is applicable to the refrigeration cycle apparatus 100 b as long as no technical contradiction arises.
The refrigeration cycle apparatus 100 b includes an upstream-side supply passage 91 b and a return passage 92 b instead of the upstream-side supply passage 91 a and the return passage 92 a. The upstream-side supply passage 91 b diverges from the condensation-side circulation circuit 7 at a position downstream of the exit of the heat-radiation-side liquid carrying pump 71 in the condensation-side circulation circuit 7. The upstream-side supply passage 91 b is a passage for supplying a refrigerant to the lubricant supply passage 30 of the turbomachine 1 a. For example, the upstream-side supply passage 91 b diverges from the condensation-side circulation circuit 7 at a position between the exit of the heat-radiation-side liquid carrying pump 71 and the entrance of the heat-radiation heat exchanger 72. Further, the upstream-side supply passage 91 b is connected to the turbomachine 1 a so as to communicate with the lubricant supply passage 30. For example, the refrigerant that travels through the upstream-side supply passage 91 b passes through the supply hole 41 to be supplied to the storage portion 40. As described above, the refrigerant to which pressure has been applied with the heat-radiation-side liquid carrying pump 71 passes through the upstream-side supply passage 91 b to be supplied to the lubricant supply passage 30 as the lubricant. In this case, the discharge pressure of the heat-radiation-side liquid carrying pump 71 is desirably set so that the pressure of the refrigerant at the inlet 33 of the lubricant supply passage 30 is equal to or more than the saturated vapor pressure.
The upstream-side supply passage 91 b may diverge from the condensation-side circulation circuit 7 at a position between the exit of the heat-radiation heat exchanger 72 and the condensation mechanism 4 in the condensation-side circulation circuit 7. Also in this case, part of the refrigerant of the refrigeration cycle apparatus 100 b may be supplied to the lubricant supply passage 30 as the lubricant.
The return passage 92 b is a passage for returning the refrigerant supplied to the lubricant supply passage 30 through the upstream-side supply passage 91 b to the main circuit 5. For example, the return passage 92 b communicates with the storage portion 40 via the discharge hole 42. Further, the return passage 92 b is connected to the condensation mechanism 4. The refrigerant stored in the storage portion 40 is guided to the return passage 92 b through the discharge hole 42 to flow through the return passage 92 b and is returned into the condensation mechanism 4. The return passage 92 a may be connected to the evaporation mechanism 2 so as to return the refrigerant to the evaporation mechanism 2.
According to the present embodiment, with the rotation of the rotation shaft, the refrigerant as the lubricant is supplied under pressure to the bearing through the lubricant supply passage in the turbomachine. Accordingly, the pressure of the refrigerant supplied as the lubricant increases and the evaporation of the refrigerant as the lubricant or the occurrence of the cavitation may be suppressed in the bearing. According to the present embodiment, the refrigerant as the lubricant is a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature. As described above, when the refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature is used as an operating fluid, the turbomachine needs the number of rotations that is very large as the number of rotations of a rotation body. Since in the refrigeration cycle apparatus according to the present embodiment, the centrifugal force produced through the large number of rotations may be utilized to apply pressure to the refrigerant, high pressure may be applied to the lubricant supplied to the bearing through the lubricant supply passage. As a result, shortage of the lubricant in the bearing may be prevented and the reliability of the turbomachine may increase. In addition, the performance that the external pump of the turbomachine for supplying the refrigerant as the lubricant to the lubricant supply passage is desired to offer may be reduced and accordingly, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.
For example, when water is used as an operating fluid, the number of rotations of the rotation body in the turbomachine is very large, which is in a range from approximately 75 thousand to 90 thousand rpm. In this case, depending on the design, the pressure of the refrigerant liquid supplied between the rotation shaft and the bearing is in a range from approximately 0.5 to 1 MPaA. In contrast, when the turbomachine according to the present disclosure is not used, that is, for example, the turbomachine in the study stage, in which the rotation shaft has no lubricant supply passage, is used, the discharge pressure of the external pump of the turbomachine is desired to be in a range from approximately 300 to 500 KPaA so as to suppress the evaporation of the refrigerant and the occurrence of cavitation in the bearing. In contrast, the discharge pressure of the external pump of the turbomachine according to the present embodiment, which is the heat-absorption-side liquid carrying pump 61 illustrated in FIG. 9, is in a range from approximately 150 to 180 KPaA. As described above, according to the present embodiment, the performance that the external pump of the turbomachine is desired to offer may be reduced and accordingly, the external pump may be downsized or the cost of the refrigeration cycle apparatus may be lowered.

[Variations]

The refrigeration cycle apparatus 100 a and the refrigeration cycle apparatus 100 b may be changed in various terms. For example, the turbomachine 1 a may include compression mechanisms of a plurality of stages. In this case, an intermediate cooler for cooling the refrigerant may be provided between the compression mechanisms. For example, when the turbomachine 1 a includes compression mechanisms of two stages, the temperature of the refrigerant vapor discharged from the compression mechanism at the first stage is 110° C. The temperature of the refrigerant vapor discharged from the compression mechanism at the second stage is, for example, 170° C. When an intermediate cooler is provided between the compression mechanism at the first stage and the compression mechanism at the second stage, the refrigerant vapor discharged from the compression mechanism at the first stage is cooled by the intermediate cooler. In this case, the temperature of the refrigerant vapor sucked into the compression mechanism at the second stage is, for example, 45° C.
The turbomachine 1 a and another compressor may be connected in series. The other compressor may be a positive-displacement compressor or a turbocompressor. In this case, an intermediate cooler may be provided between the turbomachine 1 a and the other compressor.
The passage 5 c may be provided with an expansion mechanism, such as a capillary or an expansion valve.
In the condensation mechanism 4, an ejector 4 b illustrated in FIG. 11 may be used. As illustrated in FIG. 11, the ejector 4 b includes a first nozzle 80, a second nozzle 81, a mixing unit 82, and a diffuser unit 83. The passage 7 c is connected to the first nozzle 80. The refrigerant liquid that flows out from the heat-radiation heat exchanger 72 through the passage 7 c is supplied to the first nozzle 80 as a driving flow. The passage 5 b is connected to the second nozzle 81. The temperature of the refrigerant liquid ejected from the first nozzle 80 is lowered by the heat-radiation heat exchanger 72. Thus, the ejection of the refrigerant liquid from the first nozzle 80 causes the pressure of the mixing unit 82 to be lower than the pressure of the passage 5 b. Consequently, the refrigerant vapor with pressure equal to or lower than the atmospheric pressure is continuously sucked into the second nozzle 81 through the passage 5 b.
The refrigerant liquid ejected from the first nozzle 80 while accelerating and the refrigerant vapor ejected from the second nozzle 81 while expanding and accelerating are mixed in the mixing unit 82. Then, a refrigerant mixture with a small quality (dryness) is generated because of first condensation caused by the difference in temperature between the refrigerant liquid and the refrigerant vapor and second condensation caused by the pressure raising effect based on the transportation of energy between the refrigerant liquid and the refrigerant vapor and the transportation of momentum between the refrigerant liquid and the refrigerant vapor. When the quality of the refrigerant mixture is not zero, the velocity of flow of the refrigerant mixture exceeds the velocity of sound of two-phase flow and abrupt rising of the pressure occurs, and the condensation is further promoted. The generated refrigerant mixture is a refrigerant in a liquid-phase state or a gas-liquid two-phase state of a very small quality. After that, the diffuser unit 83 regains static pressure by reducing the velocity of the refrigerant mixture. In the ejector 4 b configured as described above, the temperature and the pressure of the refrigerant rise.
The ejector 4 b further includes a needle valve 84 and a servo actuator 85. The needle valve 84 and the servo actuator 85 are flow-rate regulators for regulating the flow rate of the refrigerant liquid as a driving flow. The needle valve 84 enables the cross-sectional area of an orifice at the tip of the first nozzle 80 to be changed. The servo actuator 85 enables the position of the needle valve 84 to be adjusted. Thus, the flow rate of the refrigerant liquid that flows through the first nozzle 80 may be regulated.
The refrigeration cycle apparatus according to the present disclosure is useful for a home air conditioner or an industrial air conditioner in particular. Moreover, the refrigeration cycle apparatus according to the present disclosure is applicable to a chiller or a heat pump.

Claims

What is claimed is:

1. A turbomachine for a refrigeration cycle apparatus that uses a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the turbomachine comprising:

a rotation shaft; and

a bearing that supports the rotation shaft, wherein

the rotation shaft includes a lubricant supply passage containing

a main passage that extends from an inlet located at an end of the rotation shaft in an axial direction of the rotation shaft, and

one or more sub-passages that diverge from the main passage and that extend to an outlet located in a side surface of the rotation shaft, and

while the rotation shaft rotates, the lubricant supply passage supplies the refrigerant to a portion where is located between the rotation shaft and the bearing.

2. The turbomachine according to claim 1, wherein

the sub-passage intersects a central axis of the main passage and extends along a straight line perpendicular to the central axis.

3. The turbomachine according to claim 1, wherein

the outlet of the sub-passage is located at a more backward position in a direction of rotation of the rotation shaft than a point at which a straight line intersects the side surface of the rotation shaft, the straight line connecting a central axis of the main passage and a center of an opening of the sub-passage on a side of the main passage.

4. The turbomachine according to claim 1, wherein

when the sub-passage is viewed in an axial direction of the rotation shaft, the sub-passage is expanded backward in a direction of rotation of the rotation shaft from a position in the sub-passage to the outlet, the position being located between an opening of the sub-passage on a side of the main passage and the outlet.

5. The turbomachine according to claim 1, wherein

the lubricant supply passage includes the plurality of sub-passages arranged in the axial direction of the rotation shaft.

6. The turbomachine according to claim 1, wherein

when the sub-passage is viewed from a direction perpendicular to the axial direction of the rotation shaft, a central axis of the sub-passage is tilted with respect to a central axis of the main passage in the axial direction of the rotation shaft.

7. The turbomachine according to claim 1, further comprising:

a storage portion that adjoins the bearing on a side of the inlet and stores the refrigerant as the lubricant, wherein

the inlet located at the end of the rotation shaft is soaked in the refrigerant stored in the storage portion as the lubricant.

8. A refrigeration cycle apparatus comprising:

a main circuit that circulates a refrigerant whose saturated vapor pressure is a negative pressure at ordinary temperature, the main circuit including

an evaporation mechanism that stores a refrigerant liquid and evaporates the refrigerant liquid,

an turbomachine according to claim 1, and

a condensation mechanism that condenses refrigerant vapor and stores a refrigerant liquid, the evaporation mechanism, the turbomachine, and the condensation mechanism being connected in named order;

an evaporation-side circulation circuit that includes a heat-absorption-side liquid carrying pump and a heat-absorption heat exchanger, the heat-absorption-side liquid carrying pump causing the refrigerant liquid stored in the evaporation mechanism to be supplied to the heat-absorption heat exchanger, the refrigerant after heat absorption in the heat-absorption heat exchanger being returned to the evaporation mechanism;

a condensation-side circulation circuit that includes a heat-radiation-side liquid carrying pump and a heat-radiation heat exchanger, the heat-radiation-side liquid carrying pump causing the refrigerant liquid stored in the condensation mechanism to be supplied to the heat-radiation heat exchanger, the refrigerant after heat radiation in the heat-radiation heat exchanger being returned to the condensation mechanism; and

an upstream-side supply passage that diverges from the evaporation-side circulation circuit at a position downstream of an exit of the heat-absorption-side liquid carrying pump in the evaporation-side circulation circuit or diverges from the condensation-side circulation circuit at a position downstream of an exit of the heat-radiation-side liquid carrying pump in the condensation-side circulation circuit, and supplies the refrigerant to the lubricant supply passage.