Turbo compressor and refrigeration device

Abstract

A turbo compressor (10) comprises: 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 that has flowed 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. The diffuser flow path (40) includes a planar flow path (43) extending in a radial direction, and a curved flow path (44) bent to the opposite side to a refrigerant inflow side in an axial direction with respect to the planar flow path (43). The volute flow path (50) extends in a circumferential direction and is connected to the curved flow path (44). A maximum value (Rv) of the outer diameter of the volute flow path (50) is equal to or less than a maximum value (Rr) of the outer diameter of the intermediate flow path (30).

Description

Turbo-compressor and refrigeration device

[0001] The present disclosure relates to a turbo-compressor and a refrigeration device.

[0002] Patent Document 1 discloses a multi-stage turbo-compressor having two impellers. The turbo-compressor includes a diffuser flow path through which the refrigerant flowing out from the rear-stage impeller circulates, and a volute flow path through which the refrigerant passing through the diffuser flow path circulates. The diffuser flow path extends straight radially outward from the outlet of the rear-stage impeller. The volute flow path is connected to the radially outer end of the diffuser flow path.

[0003] U.S. Patent Publication No. 2023 / 013972

[0004] In recent years, there has been a demand for increasing the capacity of turbo-compressors. In a turbo-compressor with an increased capacity, in order to improve the fluid efficiency, it is required to sufficiently lower the flow velocity of a large amount of refrigerant in the diffuser flow path. To lower the flow velocity of the refrigerant in the diffuser flow path, it is necessary to lengthen the diffuser flow path.

[0005] In order to increase the capacity of the turbo-compressor disclosed in Patent Document 1, when the diffuser flow path is lengthened, the connection position between the diffuser flow path and the volute flow path spreads radially outward. The volute flow path spreads further radially outward from the connection position. Therefore, when the fluid efficiency of a conventional turbo-compressor is increased, the size of the turbo-compressor increases. There is room for improvement in the conventional turbo-compressor from the viewpoint of achieving both high fluid efficiency and size reduction of the turbo-compressor.

[0006] An object of the present disclosure is to reduce the size of a turbo-compressor while maintaining the fluid efficiency.

[0007] A first aspect of the technology disclosed herein relates to a turbo compressor. The turbo compressor includes a motor (100) having a stator (101) and a rotor (102), an axially extending rotating shaft (201) rotated by the rotor (102), a first impeller (11) mounted on the rotating shaft (201), a second impeller (21) mounted on the rotating shaft (201) and positioned adjacent to the first impeller (11) in the axial direction, and an outlet (14) of the first impeller (11) and the second impeller (2 1) comprises an intermediate flow path (30) through which refrigerant flows between the inlet (22a) and the first impeller (21), a diffuser flow path (40) through which refrigerant flowing out from the second impeller (21) flows, and a volute flow path (50) through which refrigerant that has passed through the diffuser flow path (40) flows, wherein the intermediate flow path (30) extends radially in a direction that radiates from the center of the rotation shaft (201) and communicates with the outlet (14) of the first impeller (11). The diffuser flow path (40) includes a second flow path (32) extending radially and communicating with the inlet (22a) of the second impeller (21), and a connecting flow path (33) connecting the radially outer portion of the first flow path (31) and the radially outer portion of the second flow path (32), wherein the diffuser flow path (40) includes a planar flow path (43) extending radially outward from the outlet (24) of the second impeller (21), and the flow of the refrigerant in the axial direction relative to the planar flow path (43). The volute channel (50) includes a curved channel (44) bent to the opposite side from the inlet side, and the volute channel (50) extends circumferentially around the central axis (X) of the rotating shaft (201) so as to surround the casing housing the rotating shaft (201) from the radially outside and is connected to the curved channel (44), and the maximum outer diameter (Rv) of the volute channel (50) with respect to the central axis (X) is less than or equal to the maximum outer diameter (Rr) of the connecting channel (33) with respect to the central axis (X).

[0008] According to the first embodiment, the volute flow path (50) is connected to the curved flow path (44), and is therefore located on the opposite side of the axial direction from the intermediate flow path (30) to the diffuser flow path (40). Furthermore, the maximum outer diameter of the volute flow path (50) is less than or equal to the maximum outer diameter of the intermediate flow path (30). As a result, the turbo compressor can be reduced in size in both the radial and axial directions. Because the length of the diffuser flow path (40) is increased by the curved flow path, the flow velocity of the refrigerant can be reduced in the diffuser flow path (40), and fluid efficiency can be maintained. Therefore, the turbo compressor can be reduced in size while maintaining fluid efficiency.

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

[0010] According to the second embodiment, 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, in the first or second aspect, the volute channel (50) has a shape in which the radial cross-section increases while widening radially inward, and when the maximum length along the radial direction in the radial cross-section of the volute channel (50) is defined as the first length (r), and the maximum length along the axial direction in the radial cross-section of the volute channel (50) is defined as the second length (L), the ratio of the second length (L) to the first length (r) is larger in the portion of the volute channel (50) with a larger radial cross-sectional area.

[0012] In the third embodiment, the radial outward expansion of the volute flow path (50) can be suppressed, allowing for a reduction in the size of the turbo compressor. Furthermore, by increasing the radial cross-section of the volute flow path (50), the refrigerant flow velocity can be reduced, thereby improving fluid efficiency. Consequently, the turbo compressor can be made smaller while simultaneously improving fluid efficiency.

[0013] A fourth aspect of the technology disclosed herein is, in the third aspect, that in the portion of the volute flow path (50) with the smallest radial cross-sectional area, the first length (r) is greater than the second length (L), and in the portion of the volute flow path (50) with the largest radial cross-sectional area, the second length (L) is greater than the first length (r).

[0014] In the fourth embodiment, in the portion with a small radial cross-sectional area, separation at the inlet of the volute flow path (50) can be suppressed by making the radial direction longer and the axial direction shorter, thereby improving fluid efficiency.

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

[0016] In the fifth embodiment, the radial length of the diffuser flow path (40) can be shortened while the overall flow path length can be increased by the curved flow path (44). Because the refrigerant flow velocity can be lowered in the diffuser flow path (40), the turbo compressor can improve its fluid efficiency.

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

[0018] In the sixth embodiment, by arranging bearings (121, 122, 123) within the motor casing (110), the turbo compressor can be reduced in size radially and axially by effectively utilizing the space around the motor casing (110).

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

[0020] In the seventh embodiment, the turbo compressor can be made smaller because it has an in-line structure.

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

[0022] In the eighth embodiment, even if an inlet guide vane (23) is placed on the intake 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 that, in any one of the first to eighth aspects, an injection tube (150) of an economizer (400) is positioned between the first impeller (11) and the second impeller (21).

[0024] In the ninth embodiment, even if an injection pipe (150) is placed 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 comprising a multi-stage turbo compressor (10) as described in any one of the first to ninth aspects.

[0026] An eleventh aspect of the technology disclosed herein is that the refrigerant is a low-pressure refrigerant.

[0027] Figure 1 is a block diagram showing the configuration of a refrigeration system equipped with a turbo compressor according to an exemplary embodiment. Figure 2 is a perspective view of the turbo compressor. Figure 3 is a cross-sectional view taken along the line III-III shown in Figure 2. Figure 4 is a cross-sectional view taken along the line IV-IV shown in Figure 3. Figure 5 is an enlarged view of region V in Figure 3. Figure 6 is a front view of the turbo compressor. Figure 7 is an enlarged view of the diffuser flow path. Figure 8 is a rear view of the volute flow path. Figure 9 is a cross-sectional view taken at the portion of the volute flow path with the smallest radial cross-sectional area. Figure 10 is a cross-sectional view taken at the portion of the volute flow path with the largest radial cross-sectional area.

[0028] The embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below, and various modifications are possible without departing from the technical idea of ​​this disclosure. Since the drawings are for conceptual illustration of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.

[0029] (1) Refrigeration apparatus Figure 1 shows a refrigeration apparatus (1) equipped with a turbo compressor (10) according to this embodiment. The refrigeration apparatus (1) comprises a turbo compressor (10), a condenser (300), an economizer (400), an evaporator (500), and first piping (610) to fourth piping (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) comprises a motor (100) and a compression unit (200) including a first impeller (11) and a second impeller (21) rotated by the motor (100). The first impeller (11) and the second impeller (21) are mounted on 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] A turbo compressor (10) compresses the refrigerant that has been heat-exchanged in the condenser (300). The refrigerant is a low-pressure refrigerant. The refrigerant is, for example, a hydrofluorocarbon such as the alternative fluorocarbons 1233ZD, R123, DR-2, and 1336MZZ, or R718 (water).

[0032] The first piping (610) is connected to the compression unit (200) and the condenser (300), and the refrigerant compressed in the compression unit (200) is sent 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, and returns it to a liquid state. The condenser (300) is, for example, a shell-and-tube type 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 tube (150). The nozzle (150a) of the injection tube (150) is located in the compression unit (200). The injection tube (150) delivers the gaseous 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 exchanging heat with water, resulting in saturated vapor.

[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 rotating shaft (201) extends, "radial direction" refers to the direction radiating from the central axis (X) of the rotating shaft (201), and "circumferential direction" refers to the direction around the central axis (X) of the rotating shaft (201). Also, in the axial direction, the side on which the compression unit (200) is located is called the front side, and the side on which the motor (100) is located is called 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 the same direction. As shown in Figure 2, the turbo compressor (10) has a motor casing (110) that houses a motor (100) and a unit casing (210) that houses a 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 Figure 3, the motor (100) has a stator (101) and a rotor (102). The stator (101) is mounted on the inner circumferential wall of the motor casing (110). The rotor (102) is mounted on the 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) houses a first radial bearing (121), a second radial bearing (122), and a thrust bearing (123) as bearings to support the rotating shaft (201).

[0041] The first radial bearing (121) and the second radial bearing (122) are, for example, magnetic bearings that non-contactively support the rotating shaft (201) by electromagnetic force. The first radial bearing (121) is positioned on the side of the rotor (102) that faces the compression unit (200) (front side). The second radial bearing (122) is positioned on the side of the rotor (102) that faces 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 composed of rolling bearings, sliding bearings, gas bearings, etc.

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

[0043] The motor casing (110) further houses 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 at a portion anterior to the first radial bearing (121). The second touchdown bearing is disposed at a position between the second radial bearing (122) and the thrust bearing (123) in the axial direction.

[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 FIG. 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 disposed adjacent to each other with an axial interval therebetween. 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) behind the first impeller (11).

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

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

[0048] (2-2-3) Flow Path As shown in FIG. 3, within the unit casing (210), as flow paths through which the refrigerant flows, there are arranged a first inflow path (12), an intermediate flow path (30), a second inflow path (22), a diffuser flow path (40), a volute flow path (50), and a final outflow path (60) (see FIG. 2).

[0049] The first inflow path (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 the first IGV (13)) is arranged in the first inflow path (12). The first IGV (13) adjusts the flow rate of the refrigerant flowing into the first impeller (11). A first adjustment mechanism (13a) for adjusting 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 inflow path (12) in the unit casing (210).

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

[0052] As shown in Figure 5, the intermediate flow path (30) circulates the refrigerant between the first outlet (14) and the second inlet (22a), which is the entrance to the second inlet passage (22). The intermediate flow path (30) is formed over the entire circumferential direction. As shown in Figure 5, the intermediate flow path (30) has a first flow path (31), a second flow path (32), and a connecting flow path (33) that 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 channel (31) communicates with the first outlet (14). The first channel (31) extends radially from the first outlet (14).

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

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

[0056] As shown in Figure 5, the second inlet passage (22) is curved axially 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 positioned on the suction side of the second impeller (21). The second IGV (23) is positioned in the second flow path (32) and the second inlet passage (22) of the intermediate flow path (30). The second IGV (23) adjusts the flow rate of the refrigerant flowing toward the second impeller (21). A second adjustment mechanism (23a) for adjusting the opening degree of the second IGV (23) is attached to the unit casing (210). Part of the second adjustment mechanism (23a) is positioned in the pre-chamber (211).

[0058] As shown in Figure 7, the diffuser flow path (40) extends from the second outlet (24), which is the 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 circumferentially. The diffuser flow path (40) is formed by a front portion (41) that extends circumferentially and is located relatively towards the front, and a rear portion (42) that is axially opposite to the front portion (41). The diffuser flow path (40) has a planar flow path (43) and a curved flow path (44).

[0059] The planar channel (43) extends radially from the second outlet (24). The curved channel (44) is bent relative to the planar channel (43) on the opposite side from the refrigerant inflow side (the rear side in the axial direction). In the radial cross-section of the diffuser channel (40), at the intermediate span, which is midway between the front portion (41) and the rear portion (42) of the diffuser channel (40), the ratio of the length of the curved channel (44) (Dc) to the length of the planar channel (43) (Dp) is 0.5 or more. The maximum outer diameter of the diffuser channel (40) is the same as the maximum outer diameter of the volute channel (50) (hereinafter referred to as the outermost diameter (Rv)).

[0060] The volute channel (50) is through which the refrigerant that has passed through the diffuser channel (40) flows. The volute channel (50) is located on the opposite side of the axial direction from the intermediate channel (30) relative to the diffuser channel (40). In other words, the volute channel (50) is located on the motor (100) side in the axial direction relative to the diffuser channel (40). The volute channel (50) is connected to the rear side of the curved channel (44). From the connection point with the curved channel (44), the volute channel (50) extends radially inward and to the rear. The radial position at the inlet of the volute channel (50) is the same as the radial position at the outlet of the curved channel (44).

[0061] As shown in Figure 8, the volute flow path (50) extends circumferentially, surrounding the motor casing (110) from the radially outside. 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 less than or equal to the outermost diameter (Rr) of the connecting flow path (33) throughout 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 connecting flow path (33) is approximately 0.96. Therefore, when the turbo compressor (10) is viewed from the axial front, the volute flow path (50) overlaps with the intermediate flow path (30) and is not visible.

[0062] The volute channel (50) has a shape in which the radial cross-section increases while expanding radially inward and backward, while keeping the outermost diameter (Rv) constant. At the location of the volute channel (50), the outer diameter (Rm) of the motor casing (110) with respect to the central axis (X) is smaller than the minimum value of the inner diameter (Rvi) of the unit casing (210) with respect to the central axis (X). There is always a gap between the part of the unit casing (210) that constitutes the volute channel (50) and the motor casing (110). At the location of the volute channel (50), at the point where the unit casing (210) and the motor casing (110) are closest radially, 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 Figures 9 and 10, the maximum length along the radial direction in the radial cross-section of the volute channel (50) is defined as the first length (r), and the maximum length along the axial direction in the radial cross-section is defined as the second length (L). When the radial cross-sectional area expands, the change in the second length (L) is greater than or equal to the change in the first length (r). The ratio of the second length (L) to the first length (r) is larger in the larger the radial cross-sectional area of ​​the volute channel (50). As shown in Figure 9, in the part of the volute channel (50) with the smallest radial cross-sectional area, the first length (r) is greater than the second length (L). In this part, the ratio of the second length (L) to the first length (r) is less than 1. On the other hand, as shown in Figure 10, in the part of the volute channel (50) with the largest radial cross-sectional area, the second length (L) is greater than the first length (r). In this section, the ratio of the second length (L) to the first length (r) is greater than 1.

[0064] As shown in Figure 8, the final outlet passage (60) is connected to the portion of the volute passage (50) with the largest radial cross-sectional area. The final outlet passage (60) discharges the refrigerant whose flow velocity has been reduced by the diffuser passage (40) and the volute passage (50). The final outlet passage (60) is connected to the first piping (610).

[0065] The refrigerant flows in from the first inlet passage (12) and its flow rate is regulated by the first IGV (13). The regulated refrigerant is compressed by the first impeller (11) and flows out into the first flow path (31). After passing through the connecting flow path (33), the refrigerant merges with the refrigerant from the economizer (400) in the second flow path (32). At this time, the flow rate of the refrigerant is regulated by the second IGV (23). Also, the flow velocity of the refrigerant decreases as it 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) via 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 flows through the planar channel (43) and the curved channel (44), gradually decreasing in flow velocity as it enters the volute channel (50). After decreasing in flow velocity within the volute channel (50), the refrigerant flows out through the final outlet channel (60).

[0066] (3) Effects of the Embodiment In this embodiment, the intermediate flow path (30) includes a first flow path (31) extending radially and communicating with the outlet (14) of the first impeller (11), a second flow path (32) extending radially and communicating with the inlet (22a) of the second impeller (21), and a connecting flow path (33) connecting the radially outer portion of the first flow path (31) and the radially outer portion of the second flow path (32), and the diffuser flow path (40) is the outlet (24) of the second impeller (21) The volute channel (50) has a planar channel (43) extending radially outward from the planar channel (43) and a curved channel (44) bent axially away from the refrigerant inflow side in the axial direction relative to the planar channel (43). The volute channel (50) is connected to the curved channel (44) and extends circumferentially around the central axis (X) of the rotating shaft (201) so as to surround the casing housing the rotating shaft (201) from the radially outward direction, and the outermost diameter (Rv) of the volute channel (50) is less than or equal to the outermost diameter (Rr) of the connecting channel (33). In this embodiment, since the curved channel (44) is bent axially away from the refrigerant inflow side in the axial direction relative to the planar channel (43), the volute channel (50) connected to the curved channel (44) is positioned axially away from the intermediate channel (30) relative to the diffuser channel (40). If the volute passage (50) were to be positioned on the same axial side as the intermediate passage (30) relative to the diffuser passage (40), the axial distance between the first impeller (11) and the second impeller (21) would need to be increased to secure space for the volute passage (50). In this embodiment, since the volute passage (50) is positioned on the opposite axial side from the intermediate passage (30) relative to the diffuser passage (40), the first impeller (11) and the second impeller (21) can be positioned adjacent and close together in the axial direction. This allows the turbo compressor (10) to be reduced in size in the axial direction. Furthermore, since the outermost diameter (Rv) of the volute passage (50) is less than or equal to the outermost diameter (Rr) of the connecting passage (33), the size can be reduced in the radial direction. In addition, the diffuser passage (40) has a longer flow path length due to the curved passage (44), which reduces the flow velocity of the refrigerant, thus 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 operating at high rotational speeds.

[0068] In this embodiment, the volute channel (50) is positioned on the opposite side of the axial direction from the intermediate channel (30) to the diffuser channel (40), thus increasing the degree of freedom in routing the intermediate channel (30).

[0069] In this embodiment, the outermost diameter of the connecting channel (33) is constant in the circumferential direction, and the outermost diameter (Rv) of the volute channel (50) is also constant in the circumferential direction. This allows the outermost diameter (Rv) of the volute channel (50) to be made as large as possible within a range less than or equal to the outermost diameter (Rr) of the connecting channel (33). Because the radial cross-sectional area of ​​the volute channel (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 opposite side of the second impeller (21) from the first impeller (11) in the axial direction, and the volute flow path (50) surrounds the motor casing (110) housing the motor (100) from the radially outside. As motors (100) are becoming smaller, 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 in which the radial cross-section increases while expanding radially inward, and in the radial cross-section of the volute flow path (50), the ratio of the second length (L) to the first length (r) is larger in the portion of the volute flow path (50) where the radial cross-sectional area is larger. This suppresses the volute flow path (50) from expanding radially outward, and allows the turbo compressor (10) to be reduced in size radially. Furthermore, by increasing the radial cross-section of the volute flow path (50) in the axial direction, the radial cross-sectional area can be efficiently increased. By increasing the radial cross-sectional area of ​​the volute flow path (50), the flow velocity of the refrigerant 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, in the portion of the volute flow path (50) with the smallest radial cross-sectional area, the first length (r) is greater than the second length (L), and in the portion of the volute flow path (50) with the largest radial cross-sectional area, the second length (L) is greater than the first length (r). In the portion with a small radial cross-sectional area, by making the radial length longer and the axial length shorter, the refrigerant flow at the inlet of the volute flow path (50) can be made to flow along the wall surface of the volute flow path (50). As a result, separation at the inlet of the volute flow path (50) can be suppressed, and the turbo compressor (10) according to this embodiment can improve fluid efficiency.

[0073] In this embodiment, at the location of the volute flow path (50), at the point where the unit casing (210) and the motor casing (110) are closest 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. Since a gap is secured between the unit casing (210) and the motor casing (110), tool insertion can be improved. The turbo compressor (10) according to this embodiment can improve maintainability.

[0074] In this embodiment, in a cross-section obtained by cutting the diffuser flow path (40) with 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) in the intermediate span of the diffuser flow path (40) is 0.5 or more. This allows the radial distance of the diffuser flow path (40) to be shortened while increasing the overall flow path length of the diffuser flow path (40). As a result, the flow velocity of the refrigerant in the diffuser flow path (40) can be lowered, and the turbo compressor (10) according to this embodiment can improve fluid efficiency.

[0075] In this embodiment, the motor casing (110) houses bearings (121, 122, 123) that support the rotating shaft (201). By arranging the bearings (121, 122, 123) within 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 the same direction. Compared to a non-inline structure, the routing of the intermediate flow path (30) can be simplified, and therefore the turbo compressor (10) according to this embodiment can be made smaller.

[0077] In this embodiment, the second IGV (23) is positioned on the intake side of the second impeller (21). Since the volute passage (50) is located on the opposite side of the axial direction from the intermediate passage (30) to the diffuser passage (40), a pre-chamber (211) can be formed between the second impeller (21) and the intermediate passage (30) in the axial direction. Since the second adjustment mechanism (23a) can be positioned in the pre-chamber (211), the turbo compressor (10) according to this embodiment can accommodate the second IGV (23) while keeping the axial size small.

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

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

[0080] The volute flow path (50) may be configured to enlarge the radial cross-section by expanding it in only one of the radial or axial directions.

[0081] The motor (100) may be separate from the compression unit (200). In this case, the rotation of the motor (100) can be transmitted to the rotating shaft (201) via gears. Also, the volute flow path (50) surrounds the casing that houses the rotating shaft (201), rather than the motor casing (110).

[0082] The turbo compressor (10) may be a multi-stage turbo compressor equipped with three or more impellers. In this case, an additional impeller is added upstream of the first impeller (11).

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

[0084] While embodiments and modifications have been described above, it will be understood that a variety of changes in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the embodiments, modifications, and other embodiments described above may be combined or substituted as appropriate, as long as they do not impair the functions covered by this disclosure.

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

[0086] As described above, this disclosure is useful for turbo compressors.

[0087] 1 Refrigeration unit 11 First impeller 21 Second impeller 23 Second inlet guide vane 30 Intermediate channel 31 First channel 32 Second channel 33 Connecting channel 40 Diffuser channel 43 Planar channel 44 Curved channel 50 Volute channel 100 Motor 101 Stator 102 Rotor 110 Motor casing 121 First radial bearing 122 Second radial bearing 123 Thrust bearing 150 Injection tube 201 Rotating shaft 400 Economizer Dc Curved channel length Dp Planar channel length L Second length r First length Rr Maximum outer diameter of connecting channel Rv Maximum outer diameter of volute channel X Center axis

Claims

1. A motor (100) having a stator (101) and a rotor (102); a rotating shaft (201) extending in the 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 arranged adjacent to the first impeller (11) in the axial direction; an intermediate flow path (30) for circulating refrigerant 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 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, wherein the intermediate flow path (30) is The diffuser flow path (40) includes: a first flow path (31) extending radially in a direction radiating from the center of the rotating shaft (201) and communicating with the outlet (14) of the first impeller (11); a second flow path (32) extending radially and communicating with the inlet (22a) of the second impeller (21); and a connecting flow path (33) connecting the radially outer portion of the first flow path (31) and the 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 curved flow path (44) bent relative to the planar flow path (43) on the opposite side from the refrigerant inflow side in the axial direction; A multi-stage turbo compressor wherein the volute flow path (50) extends in the circumferential direction about the central axis (X) of the rotating shaft (201) so as to surround the casing housing the rotating shaft (201) from the radially outside and is connected to the curved flow path (44), and the maximum outer diameter (Rv) of the volute flow path (50) with respect to the central axis (X) is less than or equal to the maximum outer diameter (Rr) of the connecting flow path (33) with respect to the central axis (X).

2. A multistage turbo compressor according to claim 1, wherein the motor (100) is located on the opposite side of the axial direction from the first impeller (11) with respect to the second impeller (21), and the casing is a motor casing (110) housing the motor (100).

3. A multistage turbo compressor according to claim 1 or 2, wherein the volute flow path (50) has a shape in which the radial cross-section increases while widening radially inward, and when the maximum length along the radial direction in the radial cross-section of the volute flow path (50) is defined as the first length (r), and the maximum length along the axial direction in the radial cross-section of the volute flow path (50) is defined as the second length (L), the ratio of the second length (L) to the first length (r) is larger in the portion of the volute flow path (50) with a larger radial cross-sectional area.

4. A multi-stage turbo compressor according to claim 3, wherein in the portion of the volute flow path (50) with the smallest radial cross-sectional area, the first length (r) is greater than the second length (L), and in the portion of the volute flow path (50) with the largest radial cross-sectional area, the second length (L) is greater than the first length (r).

5. A multistage turbo compressor according to any one of claims 1 to 4, wherein in the radial cross-section of the diffuser flow path (40), the ratio of the length (Dc) of the curved flow path (44) to the length (Dp) of the planar flow path (43) in the intermediate span of the diffuser flow path (40) is 0.5 or more.

6. A multi-stage turbo compressor according to claim 2, wherein the motor casing (110) houses bearings (121, 122, 123) that support the rotating shaft (201).

7. A multi-stage turbo compressor according to any one of claims 1 to 6, having 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 the same direction.

8. A multistage turbo compressor according to any one of claims 1 to 7, wherein an inlet guide vane is arranged on the suction side of the second impeller (21).

9. A multistage turbo compressor according to any one of claims 1 to 8, wherein an injection pipe (150) for an economizer (400) is positioned between the first impeller (11) and the second impeller (21).

10. A refrigeration system comprising a multi-stage turbo compressor (10) according to any one of claims 1 to 9.

11. A refrigeration apparatus according to claim 10, wherein the refrigerant is a low-pressure refrigerant.

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