Turbo compressors and refrigeration equipment

Abstract

To reduce the size of a turbo compressor while maintaining fluid efficiency. A turbo compressor (10) includes an intermediate flow path (30) through which a refrigerant flows between a first impeller (11) and a second impeller (21), a diffuser flow path (40) through which the refrigerant flowing out of the second impeller (21) flows, and a volute flow path (50) through which the refrigerant that has passed through the diffuser flow path (40) flows. The diffuser flow path (40) includes a planar flow path (43) extending in the radial direction and a curved flow path (44) bent in the axial direction opposite to the refrigerant inlet side with respect to the planar flow path (43), and the volute flow path (50) extends in the circumferential direction and is connected to the curved flow path (44), and a maximum outer diameter (Rv) of the volute flow path (50) is equal to or smaller than a maximum outer diameter (Rr) of the intermediate flow path (30).

Description

[Technical Field]

[0001] The present disclosure relates to turbocompressors and refrigeration systems. [Background technology]

[0002] Patent Document 1 discloses a multi-stage turbo compressor having two impellers. The turbo compressor includes a diffuser passage through which refrigerant flowing out from the latter-stage impeller flows, and a volute passage through which refrigerant that has passed through the diffuser passage flows. The diffuser passage extends straight radially outward from the outlet of the latter-stage impeller. The volute passage is connected to the radially outer end of the diffuser passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Publication No. 2023 / 013972 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for larger capacity turbo compressors. In order to improve fluid efficiency in these larger capacity turbo compressors, it is necessary to sufficiently reduce the flow velocity of a large amount of refrigerant in the diffuser passage. To reduce the flow velocity of the refrigerant in the diffuser passage, the diffuser passage must be longer.

[0005] When the diffuser passage is lengthened to increase the capacity of the turbo compressor disclosed in Patent Document 1, the connection position between the diffuser passage and the volute passage expands radially outward. The volute passage expands further radially outward from the connection position. For this reason, increasing the fluid efficiency of a conventional turbo compressor results in an increase in the size of the turbo compressor. From the perspective of achieving both fluid efficiency and size reduction, conventional turbo compressors have room for improvement.

[0006] An object of the present disclosure is to reduce the size of turbocompressors while maintaining fluid efficiency. [Means for solving the problem]

[0007] A first aspect of the technology disclosed herein is directed to a turbo compressor. The turbo compressor includes a motor (100) having a stator (101) and a rotor (102), a rotating shaft (201) extending in an axial direction and rotated by the rotor (102), a first impeller (11) attached to the rotating shaft (201), a second impeller (21) attached to the rotating shaft (201) and disposed adjacent to the first impeller (11) in the axial direction, and a flow outlet (14) of the first impeller (11) and a flow outlet (15) of the second impeller (21). the first impeller (11) includes an intermediate flow path (30) for circulating a refrigerant between the first impeller (11) and an inlet (22a) of the first impeller (11), a diffuser flow path (40) through which the refrigerant flowing out from the second impeller (21) flows, and a volute flow path (50) through which the refrigerant that has passed through the diffuser flow path (40) flows, and the intermediate flow path (30) includes a first flow path (31) extending in a radial direction that is a direction extending radially from the center of the rotation shaft (201) and communicating with the outlet (14) of the first impeller (11). a second flow path (32) extending in the radial direction and communicating with the inlet (22a) of the second impeller (21); and a connecting flow path (33) connecting a radially outer portion of the first flow path (31) and a radially outer portion of the second flow path (32), and the diffuser flow path (40) includes a planar flow path (43) extending radially outward from the outlet (24) of the second impeller (21), and a flow path of the refrigerant in the axial direction relative to the planar flow path (43). and a curved flow path (44) bent toward the opposite side to the inlet side, the volute flow path (50) extends in a circumferential direction about a central axis (X) of the rotating shaft (201) so as to surround a casing that accommodates the rotating shaft (201) from the radial outside and is connected to the curved flow path (44), and a maximum value (Rv) of an outer diameter of the volute flow path (50) with respect to the central axis (X) is equal to or smaller than a maximum value (Rr) of an outer diameter of the connecting flow path (33) with respect to the central axis (X).

[0008] According to the first aspect, the volute passage (50) is connected to the curved passage (44) and is therefore located on the axially opposite side of the diffuser passage (40) from the intermediate passage (30). The maximum outer diameter of the volute passage (50) is equal to or less than the maximum outer diameter of the intermediate passage (30). This allows the turbo compressor to be downsized both radially and axially. The length of the diffuser passage (40) is increased by the curved passage, so that the flow velocity of the refrigerant in the diffuser passage (40) can be reduced, thereby maintaining fluid efficiency. This allows the turbo compressor to be downsized while maintaining fluid efficiency.

[0009] A second aspect of the technology disclosed herein is the first aspect, wherein the motor (100) is located on the opposite side of the second impeller (21) from the first impeller (11) in the axial direction, and the casing is a motor casing (110) that houses the motor (100).

[0010] According to the second aspect, the turbo compressor can be reduced in size in the radial and axial directions by effectively utilizing the space around the motor casing (110).

[0011] A third aspect of the technology disclosed herein is the first or second aspect, wherein the volute channel (50) has a shape that widens radially inward and increases in radial cross section, and when a maximum length of the radial cross section of the volute channel (50) along the radial direction is defined as a first length (r) and a maximum length of the radial cross section of the volute channel (50) along the axial direction is defined as a second length (L), a ratio of the second length (L) to the first length (r) increases as the radial cross section area of ​​the volute channel (50) increases.

[0012] In the third aspect, the radially outward expansion of the volute passage (50) can be suppressed, thereby enabling a reduction in the size of the turbo compressor. Furthermore, by increasing the radial cross section of the volute passage (50), the flow velocity of the refrigerant can be reduced, thereby improving fluid efficiency. Therefore, the turbo compressor can be reduced in size while improving fluid efficiency.

[0013] A fourth aspect of the technology disclosed herein is the third aspect, wherein the first length (r) is greater than the second length (L) at a portion where the radial cross-sectional area of ​​the volute channel (50) is smallest, and the second length (L) is greater than the first length (r) at a portion where the radial cross-sectional area of ​​the volute channel (50) is largest.

[0014] In the fourth aspect, in the portion having a small radial cross-sectional area, separation at the inlet of the volute channel (50) can be suppressed by making the radial length long and the axial length short, thereby improving fluid efficiency.

[0015] A fifth aspect of the technology disclosed herein is any one of the first to fourth aspects, wherein, in a radial cross section of the diffuser passage (40), a ratio of a length (Dc) of the curved passage (44) to a length (Dp) of the flat passage (43) at a mid-span of the diffuser passage (40) is 0.5 or more.

[0016] In the fifth aspect, the radial length of the diffuser passage (40) can be shortened, while the passage length itself can be increased by the bent passage (44). Since the flow velocity of the refrigerant can be reduced in the diffuser passage (40), the turbo compressor can improve its fluid efficiency.

[0017] A sixth aspect of the technology disclosed herein is the second aspect, wherein the motor casing (110) houses bearings (121, 122, 123) that support the rotary shaft (201).

[0018] In the sixth aspect, by arranging the bearings (121, 122, 123) inside the motor casing (110), the turbo compressor can be reduced in size in the radial and axial directions by effectively utilizing the space around the motor casing (110).

[0019] A seventh aspect of the technology disclosed herein is any one of the first to sixth aspects, wherein the suction side of the first impeller (11) and the suction side of the second impeller (21) face in the same direction, forming a two-stage in-line structure.

[0020] In the seventh aspect, since the turbo compressor has an in-line structure, the size of the turbo compressor can be reduced.

[0021] An eighth aspect of the technology disclosed herein is any one of the first to seventh aspects, wherein an inlet guide vane (23) is arranged on the suction side of the second impeller (21).

[0022] In the eighth aspect, even if the inlet guide vane (23) is disposed on the suction side of the second impeller (21), the axial size of the turbo compressor can be kept small.

[0023] A ninth aspect of the technology disclosed herein is any one of the first to eighth aspects, wherein an injection pipe (150) of an economizer (400) is disposed between the first impeller (11) and the second impeller (21).

[0024] In the ninth aspect, even if an injection pipe (150) is disposed between the first impeller (11) and the second impeller (21), the axial size of the turbo compressor can be kept small.

[0025] A tenth aspect of the technology disclosed herein is a refrigeration system including the multi-stage turbo compressor (10) according to any one of the first to ninth aspects.

[0026] In an eleventh aspect of the technology disclosed herein, the refrigerant is a low-pressure refrigerant. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a block diagram illustrating the configuration of a refrigeration device including a turbo compressor according to an exemplary embodiment. [Figure 2] FIG. 2 is a perspective view of the turbo compressor. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. [Figure 5] FIG. 5 is an enlarged view of the V region in FIG. [Figure 6] FIG. 6 is a front view of the turbo compressor. [Figure 7] FIG. 7 is an enlarged view of the diffuser flow path. [Figure 8] FIG. 8 is a rear view of the volute passage. [Figure 9] FIG. 9 is a cross-sectional view of the volute passage cut at a portion where the radial cross-sectional area is smallest. [Figure 10] FIG. 10 is a cross-sectional view of the volute passage cut at a portion where the radial cross-sectional area is the largest. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present disclosure. Since the drawings are intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary to facilitate understanding.

[0029] (1) Refrigeration equipment 1 shows a refrigeration system (1) including a turbo compressor (10) according to this embodiment. The refrigeration system (1) includes the turbo compressor (10), a condenser (300), an economizer (400), an evaporator (500), and a first pipe (610) to a fourth pipe (640).

[0030] The turbo compressor (10) is a centrifugal two-stage turbo compressor having a first impeller (11) and a second impeller (21). The turbo compressor (10) includes a motor (100) and a compression unit (200) including the first impeller (11) and the second impeller (21) rotated by the motor (100). The first impeller (11) and the second impeller (21) are attached to a rotating shaft (201). The rotation of the motor (100) is transmitted to the first impeller (11) and the second impeller (21) via the rotating shaft (201). The detailed configuration of the turbo compressor (10) will be described later.

[0031] The turbo compressor (10) compresses the refrigerant that has undergone heat exchange in the condenser (300). The refrigerant is a low-pressure refrigerant. For example, the refrigerant may be a hydrofluorocarbon such as 1233ZD, R123, DR-2, or 1336MZZ, which are alternatives to chlorofluorocarbons, or R718 (water).

[0032] The first pipe (610) is connected to the compression unit (200) and the condenser (300), and sends the refrigerant compressed in the compression unit (200) to the condenser (300). The condenser (300) condenses the refrigerant. The condenser (300) cools the refrigerant by heat exchange with cooling water or the like, thereby liquefying the refrigerant. The condenser (300) is, for example, a shell-and-tube heat exchanger.

[0033] The second pipe (620) is connected to the condenser (300) and the economizer (400), and sends the refrigerant condensed in the condenser (300) to the economizer (400). The economizer (400) separates the refrigerant into a gas phase and a liquid phase.

[0034] The economizer (400) has an injection pipe (150). A nozzle (150a) of the injection pipe (150) is disposed in the compression unit (200). The injection pipe (150) sends the gas phase refrigerant separated by the economizer (400) into the compression unit (200).

[0035] The third pipe (630) is connected to the economizer (400) and the evaporator (500), and sends the liquid phase refrigerant separated by the economizer (400) to the evaporator (500). The evaporator (500) evaporates the refrigerant by heat exchange with water, thereby converting the refrigerant into a saturated vapor state.

[0036] The fourth pipe (640) is connected to the evaporator (500) and the compression unit (200), and sends the refrigerant that has undergone heat exchange in the evaporator (500) to the compression unit (200).

[0037] (2) Turbo compressor The structure of the turbo compressor (10) will be described in detail with reference to Figures 2 to 10. In the following description, "axial direction" refers to the direction in which the rotary shaft (201) extends, "radial direction" refers to the direction extending radially from the central axis (X) of the rotary shaft (201), and "circumferential direction" refers to the direction around the central axis (X) of the rotary shaft (201). In addition, in the axial direction, the side on which the compression unit (200) is disposed is referred to as the front side, and the side on which the motor (100) is disposed is referred to as the rear side.

[0038] The turbo compressor (10) employs a two-stage in-line structure in which the suction side of the first impeller (11) and the suction side of the second impeller (21) face in the same direction. As shown in Fig. 2, the turbo compressor (10) has a motor casing (110) that houses the motor (100) and a unit casing (210) that houses the compression unit (200). The motor casing (110) is attached to the rear side of the unit casing (210). The motor casing (110) and the unit casing (210) also house a rotating shaft (201).

[0039] (2-1) Motor As shown in Fig. 3, the motor (100) has a stator (101) and a rotor (102). The stator (101) is attached to the inner circumferential wall of the motor casing (110). The rotor (102) is attached to a rotating shaft (201). The diameter of the motor (100) is the same as or slightly larger than the maximum diameter of the first impeller (11) and the second impeller (21).

[0040] The motor casing (110) accommodates a first radial bearing (121), a second radial bearing (122), and a thrust bearing (123) as bearings for supporting the rotary shaft (201).

[0041] The first radial bearing (121) and the second radial bearing (122) are, for example, magnetic bearings, and support the rotating shaft (201) in a non-contact manner by electromagnetic force. The first radial bearing (121) is arranged closer to the compression unit (200) (front side) than the rotor (102). The second radial bearing (122) is arranged on the opposite side of the rotor (102) from the compression unit (200) (rear side). The first radial bearing (121) is a larger bearing than the second radial bearing (122). The first radial bearing (121) and the second radial bearing (122) may be formed as a rolling bearing, a plain bearing, a gas bearing, or the like.

[0042] The thrust bearing (123) is, for example, a magnetic bearing, and supports the disk portion (201a) arranged at the rear end of the rotating shaft (201) in a non-contact manner by electromagnetic force. The thrust bearing (123) is arranged at the rear end of the motor casing (110). The thrust bearing (123) may be formed as a rolling bearing, a plain bearing, a gas bearing, or the like.

[0043] The motor casing (110) further accommodates a first touchdown bearing and a second touchdown bearing. The first touchdown bearing and the second touchdown bearing support the rotating shaft (201) by contacting the rotating shaft (201) when the first radial bearing (121) and the second radial bearing (122) do not support the rotating shaft (201). The first touchdown bearing is disposed in front of the first radial bearing (121). The second touchdown bearing is disposed axially between the second radial bearing (122) and the thrust bearing (123).

[0044] (2-2) Compression unit The compression unit (200) includes a first impeller (11), a second impeller (21), a front chamber (211), and a flow path through which a refrigerant flows.

[0045] (2-2-1) First impeller, second impeller As shown in Figure 3, the unit casing (210) houses the first impeller (11) and the second impeller (21). The first impeller (11) and the second impeller (21) are arranged adjacent to each other with a gap in the axial direction. The first impeller (11) is attached to the front end portion of the rotating shaft (201). The second impeller (21) is attached to the rotating shaft (201) on the rear side of the first impeller (11).

[0046] (2-2-2) Front room The front chamber (211) is disposed within the unit casing (210) between the first impeller (11) and the second impeller (21) in the axial direction. More specifically, the front chamber (211) is disposed between an intermediate flow path (30) (described later) and the second impeller (21) in the axial direction. As shown in FIG. 4 , the front chamber (211) is communicated with a nozzle (150a) of the injection pipe (150). A front wall portion (212) located in front of the front chamber (211) has a plurality of through-holes (213). The plurality of through-holes (213) are disposed at equal intervals in the circumferential direction.

[0047] The refrigerant from the economizer (400) is supplied to the front chamber (211) through the injection pipe (150). The refrigerant supplied to the front chamber (211) passes through the through hole (213) and flows into a second flow path (32) of the intermediate flow path (30) described below.

[0048] (2-2-3) Flow path As shown in FIG. 3, the unit casing (210) includes, as flow paths through which the refrigerant flows, a first inlet passage (12), an intermediate passage (30), a second inlet passage (22), a diffuser passage (40), a volute passage (50), and a final outlet passage (60) (see FIG. 2).

[0049] The first inlet (12) has a first inlet (12a). The first inlet (12a) is connected to the fourth pipe (640). The first inlet (12a) corresponds to the inlet of the first impeller (11).

[0050] A first inlet guide vane (13) (hereinafter referred to as a first IGV (13)) is arranged in the first inlet passage (12). The first IGV (13) adjusts the flow rate of the refrigerant flowing toward the first impeller (11). A first adjustment mechanism (13a) that adjusts the opening degree of the first IGV (13) is attached to the unit casing (210). A part of the first adjustment mechanism (13a) is arranged around the first inlet passage (12) in the unit casing (210).

[0051] A first outlet (14) is located radially outward of the first impeller (11). The refrigerant compressed by the first impeller (11) flows out from the first outlet (14).

[0052] As shown in Fig. 5, the intermediate flow path (30) allows the refrigerant to circulate between the first outlet (14) and a second inlet (22a) which is an inlet of the second inlet channel (22). The intermediate flow path (30) is formed over the entire circumferential direction. As shown in Fig. 5, the intermediate flow path (30) includes a first flow path (31), a second flow path (32), and a connecting flow path (33) which connects the first flow path (31) and the second flow path (32). The second inlet (22a) corresponds to the inlet of the second impeller (21).

[0053] The first flow path (31) communicates with the first outlet (14). The first flow path (31) extends radially from the first outlet (14).

[0054] The second flow path (32) communicates with the second inlet (22a) and extends radially from the second inlet (22a).

[0055] The connecting flow path (33) connects a radially outer end of the first flow path (31) and a radially outer end of the second flow path (32) in the axial direction. The connecting flow path (33) has a U-shaped radial cross section, which is a cross section cut along a plane along the central axis (X). The maximum value of the outer diameter of the connecting flow path (33) relative to the central axis (X) (hereinafter referred to as the outermost diameter (Rr)) is constant in the circumferential direction. As shown in FIG. 6 , the portion of the unit casing (210) where the intermediate flow path (30) is located has a circular shape when viewed in the axial direction.

[0056] As shown in FIG. 5, the second inlet channel (22) is curved in the axial direction from the second inlet (22a) toward the second impeller (21).

[0057] A second inlet guide vane (23) (hereinafter referred to as the second IGV (23)) is arranged on the suction side of the second impeller (21). The second IGV (23) is arranged in the second flow path (32) of the intermediate flow path (30) and the second inlet path (22). The second IGV (23) adjusts the flow rate of the refrigerant flowing toward the second impeller (21). A second adjustment mechanism (23a) that adjusts the opening degree of the second IGV (23) is attached to the unit casing (210). A part of the second adjustment mechanism (23a) is arranged in the front chamber (211).

[0058] As shown in Fig. 7, the diffuser flow path (40) extends from the second outlet (24), which is an outlet of the second impeller (21). The refrigerant compressed by the second impeller (21) and flowing out from the second outlet (24) flows through the diffuser flow path (40). The diffuser flow path (40) extends over the entire circumferential direction. The diffuser flow path (40) is formed by a front surface portion (41) that extends over the entire circumferential direction and is located relatively forward, and a rear surface portion (42) that faces the front surface portion (41) in the axial direction. The diffuser flow path (40) has a flat flow path (43) and a curved flow path (44).

[0059] The flat flow path (43) extends radially from the second outlet (24). The curved flow path (44) is curved toward the opposite side of the flat flow path (43) from the refrigerant inlet side (toward the rear side in the axial direction) with respect to the flat flow path (43). In a radial cross section of the diffuser flow path (40), at an intermediate span between the front surface (41) and the rear surface (42) of the diffuser flow path (40), the ratio of the length (Dc) of the curved flow path (44) to the length (Dp) of the flat flow path (43) is 0.5 or greater. The maximum outer diameter of the diffuser flow path (40) is the same as the maximum outer diameter of the volute flow path (50) (hereinafter referred to as the outermost diameter (Rv)).

[0060] The refrigerant that has passed through the diffuser passage (40) flows through the volute passage (50). The volute passage (50) is located on the axially opposite side of the diffuser passage (40) from the intermediate passage (30). In other words, the volute passage (50) is located on the axially closer side of the motor (100) to the diffuser passage (40). The volute passage (50) is connected to the rear side of the curved passage (44). The volute passage (50) expands radially inward and rearward from the connection with the curved passage (44). The radial position of the inlet portion of the volute passage (50) is the same as the radial position of the outlet portion of the curved passage (44).

[0061] As shown in FIG. 8 , the volute flow path (50) extends in the circumferential direction so as to surround the motor casing (110) from the radially outer side. The outermost diameter (Rv) of the volute flow path (50) relative to the central axis (X) is constant in the circumferential direction. The outermost diameter (Rv) of the volute flow path (50) is equal to or smaller than the outermost diameter (Rr) of the connection flow path (33) over the entire circumferential direction. In this embodiment, the ratio of the outermost diameter (Rv) of the volute flow path (50) to the outermost diameter (Rr) of the connection flow path (33) is approximately 0.96. Therefore, when the turbo compressor (10) is viewed from the axial front side, the volute flow path (50) overlaps with the intermediate flow path (30) and is therefore invisible.

[0062] The volute flow path (50) has a shape that widens radially inward and rearward while maintaining a constant outermost diameter (Rv), and its radial cross section increases accordingly. At the position of the volute flow path (50), the outer diameter (Rm) of the motor casing (110) relative to the central axis (X) is smaller than the minimum value of the inner diameter (Rvi) of the unit casing (210) relative to the central axis (X). A gap always exists between the motor casing (110) and a portion of the unit casing (210) that constitutes the volute flow path (50). At the position of the volute flow path (50), where the unit casing (210) and the motor casing (110) are closest to each other in the radial direction, the ratio of the outer diameter (Rm) of the motor casing (110) to the inner diameter (Rvi) of the unit casing (210) is 0.95 or less.

[0063] As shown in FIGS. 9 and 10 , the maximum length along the radial direction in the radial cross section of the volute channel (50) is defined as a first length (r), and the maximum length along the axial direction in the radial cross section is defined as a second length (L). When the radial cross-sectional area increases, the amount of change in the second length (L) is equal to or greater than the amount of change in the first length (r). The ratio of the second length (L) to the first length (r) increases as the radial cross-sectional area of ​​the volute channel (50) increases. As shown in FIG. 9 , in the portion of the volute channel (50) where the radial cross-sectional area is smallest, the first length (r) is larger than the second length (L). In this portion, the ratio of the second length (L) to the first length (r) is smaller than 1. On the other hand, as shown in FIG. 10 , in the portion of the volute channel (50) where the radial cross-sectional area is largest, the second length (L) is larger than the first length (r). In this section, the ratio of the second length (L) to the first length (r) is greater than one.

[0064] 8, the final outlet channel (60) is connected to a portion of the volute channel (50) having the largest radial cross-sectional area. The final outlet channel (60) allows the refrigerant, the flow velocity of which has been reduced by the diffuser channel (40) and the volute channel (50), to flow out. The final outlet channel (60) is connected to the first pipe (610).

[0065] The refrigerant flows in through the first inlet passage (12) and is adjusted in flow rate by the first IGV (13). The adjusted refrigerant is compressed by the first impeller (11) and flows out into the first flow path (31). The refrigerant passes through the connecting flow path (33) and then merges with the refrigerant from the economizer (400) in the second flow path (32). The flow rate of the refrigerant is adjusted by the second IGV (23). The flow velocity of the refrigerant decreases as the refrigerant passes through the first flow path (31), the connecting flow path (33), and the second flow path (32). The refrigerant that has passed through the second IGV (23) flows into the second impeller (21) through the second inlet passage (22) and is compressed by the second impeller (21). The refrigerant compressed by the second impeller (21) flows out into the planar flow path (43). The refrigerant passes through the planar flow path 43 and the curved flow path 44, and while decreasing its flow velocity, flows into the volute flow path 50. After decreasing its flow velocity in the volute flow path 50, the refrigerant flows out from the final outlet path 60.

[0066] (3) Effects of the embodiment In the present embodiment, the intermediate flow path (30) includes a first flow path (31) extending in the radial direction and communicating with the outlet (14) of the first impeller (11), a second flow path (32) extending in the radial direction and communicating with the inlet (22a) of the second impeller (21), and a connecting flow path (33) connecting a radially outer portion of the first flow path (31) to a radially outer portion of the second flow path (32). The diffuser flow path (40) extends in the radial direction from the outlet (24) of the second impeller (21). The refrigerant flow passage (50) includes a planar flow passage (43) extending outward and a curved flow passage (44) bent relative to the planar flow passage (43) in the axial direction opposite to the refrigerant inlet side, and the volute flow passage (50) is connected to the curved flow passage (44) and extends in the circumferential direction about the central axis (X) of the rotating shaft (201) so as to surround the casing accommodating the rotating shaft (201) from the radial outside, and the outermost diameter (Rv) of the volute flow passage (50) is equal to or smaller than the outermost diameter (Rr) of the connecting flow passage (33). In this embodiment, the curved flow passage (44) is bent relative to the planar flow passage (43) in the axial direction opposite to the refrigerant inlet side, and therefore the volute flow passage (50) connected to the curved flow passage (44) is located on the axial opposite side of the intermediate flow passage (30) with respect to the diffuser flow passage (40). If the volute flow path (50) were located on the same axial side of the diffuser flow path (40) as the intermediate flow path (30), the axial distance between the first impeller (11) and the second impeller (21) would need to be increased to ensure a space for arranging the volute flow path (50). In this embodiment, the volute flow path (50) is located on the axial opposite side of the diffuser flow path (40) from the intermediate flow path (30). This allows the first impeller (11) and the second impeller (21) to be positioned adjacent to each other in the axial direction. This allows the turbo compressor (10) to be downsized in the axial direction. Furthermore, since the outermost diameter (Rv) of the volute flow path (50) is equal to or smaller than the outermost diameter (Rr) of the connecting flow path (33), the size of the turbo compressor (10) can be reduced in the radial direction. Furthermore, the length of the diffuser flow path (40) is increased by the bent flow path (44), which reduces the flow velocity of the refrigerant, thereby maintaining fluid efficiency. Therefore, the turbo compressor (10) according to this embodiment can be reduced in size while maintaining fluid efficiency.

[0067] In this embodiment, the first impeller (11) and the second impeller (21) can be arranged adjacent to and close to each other in the axial direction, thereby improving the reliability of the turbo compressor (10) when it is operated at a high rotation speed.

[0068] In this embodiment, the volute flow path (50) is disposed on the axially opposite side of the diffuser flow path (40) from the intermediate flow path (30), thereby increasing the degree of freedom in the arrangement of the intermediate flow path (30).

[0069] In this embodiment, the outermost diameter of the connection passage (33) is constant in the circumferential direction, and the outermost diameter (Rv) of the volute passage (50) is also constant in the circumferential direction. This allows the outermost diameter (Rv) of the volute passage (50) to be as large as possible within a range equal to or smaller than the outermost diameter (Rr) of the connection passage (33). Since the radial cross-sectional area of ​​the volute passage (50) can be increased, the turbo compressor (10) according to this embodiment can be reduced in size while maintaining fluid efficiency.

[0070] In this embodiment, the motor (100) is located on the axial side of the second impeller (21) opposite the first impeller (11), and the volute flow path (50) surrounds a motor casing (110) that houses the motor (100) from the radial outside. As the motor (100) becomes increasingly compact, the area around the motor casing (110) tends to become dead space. The turbo compressor (10) according to this embodiment can be reduced in size in the radial and axial directions by effectively utilizing the space around the motor casing (110).

[0071] In this embodiment, the volute flow path (50) has a shape that widens radially inward and increases in radial cross section. In the radial cross section of the volute flow path (50), the ratio of the second length (L) to the first length (r) increases as the radial cross section of the volute flow path (50) increases. This prevents the volute flow path (50) from increasing radially outward, thereby enabling the turbo compressor (10) to be reduced in size in the radial direction. Furthermore, by increasing the radial cross section of the volute flow path (50) in the axial direction, the radial cross section can be efficiently increased. By increasing the radial cross section of the volute flow path (50), the refrigerant flow velocity can be reduced, thereby improving fluid efficiency. Therefore, the turbo compressor (10) according to this embodiment can improve fluid efficiency and be reduced in size.

[0072] In this embodiment, the first length (r) is greater than the second length (L) in the portion of the volute flow path (50) where the radial cross-sectional area is smallest, and the second length (L) is greater than the first length (r) in the portion of the volute flow path (50) where the radial cross-sectional area is largest. By making the radial length longer and the axial length shorter in the portion where the radial cross-sectional area is small, the refrigerant flow can be made to flow along the wall surface of the volute flow path (50) at the inlet of the volute flow path (50). This makes it possible to suppress separation at the inlet of the volute flow path (50), and therefore the turbo compressor (10) according to this embodiment can improve fluid efficiency.

[0073] In this embodiment, at the position of the volute flow path (50), where the unit casing (210) and the motor casing (110) are closest to each other in the radial direction, the ratio of the outer diameter (Rm) of the motor casing (110) to the inner diameter (Rvi) of the unit casing (210) is equal to or less than 0.95. A gap is ensured between the unit casing (210) and the motor casing (110), which improves the ease of insertion of tools. The turbo compressor (10) according to this embodiment can improve maintainability.

[0074] In this embodiment, in a cross section of the diffuser flow path (40) taken along a plane along the central axis (X), the ratio of the length (Dc) of the curved flow path (44) to the length (Dp) of the flat flow path (43) at the mid-span of the diffuser flow path (40) is 0.5 or greater. The radial distance of the diffuser flow path (40) can be shortened while the overall flow path length of the diffuser flow path (40) itself can be increased. This allows the flow velocity of the refrigerant in the diffuser flow path (40) to be reduced, thereby improving the fluid efficiency of the turbo compressor (10) according to this embodiment.

[0075] In this embodiment, the motor casing (110) accommodates bearings (121, 122, 123) that support the rotating shaft (201). By arranging the bearings (121, 122, 123) in the motor casing (110), the turbo compressor (10) according to this embodiment can be reduced in size in the radial and axial directions by effectively utilizing the space around the motor casing (110).

[0076] In this embodiment, the turbo compressor (10) has a two-stage inline structure in which the suction side of the first impeller (11) and the suction side of the second impeller (21) face in the same direction. Since the layout of the intermediate flow path (30) can be simplified compared to a non-inline structure, the turbo compressor (10) according to this embodiment can be made smaller.

[0077] In this embodiment, the second IGV (23) is disposed on the suction side of the second impeller (21). Since the volute flow path (50) is located on the axially opposite side of the diffuser flow path (40) from the intermediate flow path (30), a front chamber (211) can be formed between the second impeller (21) and the intermediate flow path (30) in the axial direction. Since the second adjustment mechanism (23a) can be disposed in the front chamber (211), the turbo compressor (10) according to this embodiment can have the second IGV (23) disposed therein while maintaining a small axial size.

[0078] In this embodiment, an injection pipe (150) of the economizer (400) is disposed between the first impeller (11) and the second impeller (21). A front chamber (211) can be formed between the second impeller (21) and the intermediate flow path (30). Since the injection pipe (150) can be disposed in the front chamber (211), the turbo compressor (10) according to this embodiment can accommodate the injection pipe (150) while maintaining a small axial size.

[0079] (4) Other embodiments The outermost diameter (Rv) of the volute passage (50) does not have to be constant in the circumferential direction. For example, the outermost diameter (Rv) of the volute passage (50) may be smaller in a portion of the volute passage (50) having a smaller radial cross-sectional area.

[0080] The volute channel (50) may be configured to expand in only one of the radial and axial directions to expand its radial cross section.

[0081] The motor (100) may be separate from the compression unit (200). In this case, the rotation of the motor (100) may be transmitted to the rotary shaft (201) via a gear. The volute flow path (50) surrounds the casing that houses the rotary shaft (201) instead of the motor casing (110).

[0082] The turbo compressor (10) may be a multi-stage turbo compressor having three or more impellers, in which case an additional impeller is provided upstream of the first impeller (11).

[0083] The first IGV (13), the second IGV (23), and the injection pipe (150) are not essential and may be omitted.

[0084] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0085] The terms "first," "second," "third," etc. mentioned above are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0086] As described above, the present disclosure is useful for turbocompressors. [Explanation of symbols]

[0087] 1 Refrigeration equipment 11 First impeller 21 Second impeller 23 Second inlet guide vane 30 Intermediate flow path 31 First Channel 32 Second Flow Path 33 Connecting Channel 40 Diffuser passage 43 Planar flow channel 44 Curved channel 50 Volute passage 100 motor 101 Stator 102 rotor 110 Motor casing 121 First radial bearing 122 Second radial bearing 123 Thrust bearing 150 injection tube 201 Rotation axis 400 Economizer Dc Length of the bend Dp Planar channel length L Second length r First length Rr Maximum outer diameter of connecting channel Rv Maximum outer diameter of volute passage X center axis

Claims

1. a motor (100) having a stator (101) and a rotor (102); an axially extending rotary shaft (201) rotated by the rotor (102); a first impeller (11) attached to the rotating shaft (201); a second impeller (21) attached to the rotating shaft (201) and disposed adjacent to the first impeller (11) in the axial direction; an intermediate flow path (30) through which a refrigerant flows between the outlet (14) of the first impeller (11) and the inlet (22a) of the second impeller (21); a diffuser flow path (40) through which the refrigerant flowing out of the second impeller (21) flows; a volute flow path (50) through which the refrigerant that has passed through the diffuser flow path (40) flows, The intermediate flow path (30) a first flow path (31) extending in a radial direction, that is, a direction extending radially from the center of the rotation shaft (201), and communicating with the outlet (14) of the first impeller (11); a second flow path (32) extending in the radial direction and communicating with the inlet (22a) of the second impeller (21); a connecting flow path (33) connecting a radially outer portion of the first flow path (31) and a radially outer portion of the second flow path (32); Including, The diffuser flow path (40) a planar flow path (43) extending radially outward from the outlet (24) of the second impeller (21); a curved flow path (44) bent in a direction opposite to the inlet side of the refrigerant with respect to the flat flow path (43) in the axial direction; Including, the volute flow path (50) extends in a circumferential direction about a central axis (X) of the rotating shaft (201) so as to surround a casing that accommodates the rotating shaft (201) from the radially outer side, is connected to the curved flow path (44), and has a shape in which a radial cross section becomes larger while widening radially inward, a maximum value (Rv) of an outer diameter of the volute channel (50) relative to the central axis (X) is equal to or smaller than a maximum value (Rr) of an outer diameter of the connecting channel (33) relative to the central axis (X); when a maximum length along the radial direction in a radial cross section of the volute channel (50) is defined as a first length (r) and a maximum length along the axial direction in the radial cross section of the volute channel (50) is defined as a second length (L), a ratio of the second length (L) to the first length (r) increases as the radial cross-sectional area of ​​the volute channel (50) increases, a multi-stage turbo compressor, wherein the first length (r) is greater than the second length (L) at a portion of the volute flow path (50) where the radial cross-sectional area is smallest, and the second length (L) is greater than the first length (r) at a portion of the volute flow path (50) where the radial cross-sectional area is largest.

2. 2. The multi-stage turbo compressor according to claim 1, the motor (100) is located on the opposite side of the second impeller (21) from the first impeller (11) in the axial direction; The casing is a motor casing (110) that houses the motor (100).

3. 2. The multi-stage turbo compressor according to claim 1, In a radial cross section of the diffuser flow path (40), a ratio of a length (Dc) of the curved flow path (44) to a length (Dp) of the flat flow path (43) at an intermediate span of the diffuser flow path (40) is 0.5 or more.

4. 3. The multi-stage turbo compressor according to claim 2, The motor casing (110) of the multi-stage turbo compressor accommodates bearings (121, 122, 123) that support the rotary shaft (201).

5. The multi-stage turbo compressor according to any one of claims 1 to 4, The multi-stage turbo compressor has a two-stage in-line structure in which the suction side of the first impeller (11) and the suction side of the second impeller (21) face in the same direction.

6. The multi-stage turbo compressor according to any one of claims 1 to 4, A multi-stage turbo compressor, wherein an inlet guide vane is disposed on the suction side of the second impeller (21).

7. The multi-stage turbo compressor according to any one of claims 1 to 4, The multi-stage turbo compressor further comprises an injection pipe (150) of an economizer (400) disposed between the first impeller (11) and the second impeller (21).

8. A refrigeration system comprising the multi-stage turbo compressor (10) according to any one of claims 1 to 4.

9. 9. The refrigeration system according to claim 8, The refrigeration device wherein the refrigerant is a low-pressure refrigerant.

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