Centrifugal compressors, refrigeration equipment

Abstract

A technology is provided that can improve the performance of a closed impeller of a centrifugal compressor. [Solution] A compressor (10) according to one embodiment of the present disclosure comprises an impeller (200) and a casing (100) that houses the impeller (200). The impeller (200) has a hub (210) having a meridian plane (211), a plurality of blades (220) arranged on the meridian plane (211), and a shroud (230) arranged at the tips of the plurality of blades so as to cover the meridian plane (211). The shroud (230) has a through hole (235) that penetrates between an inner surface facing the meridian plane (211) and an outer surface facing the inner surface of the casing (100), and has an opening (235B) on the outer surface side and an opening (235A) on the inner surface side. In a cross section including the axis AX of the rotation shaft (250) of the impeller (200), the through hole (235) is inclined so that the center (235Bc) of the opening (235B) is located closer to the inlet (200in) of the impeller (200) than the center (235Ac) of the opening (235A.

Description

[Technical Field]

[0001] The present disclosure relates to centrifugal compressors and the like. [Background technology]

[0002] BACKGROUND ART Conventionally, a technique relating to a closed impeller of a centrifugal compressor is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-156122 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, it is desirable to improve the performance of the closed impeller of a centrifugal compressor by suppressing performance degradation due to, for example, backflow, separation, and the like.

[0005] An object of the present disclosure is to provide a technique that can improve the performance of a closed impeller of a centrifugal compressor. [Means for solving the problem]

[0006] In a first aspect of the present disclosure, Impeller (200) and a casing (100) that houses the impeller (200), The impeller (200) a hub (210) having a meridian face (211); a plurality of blades (220) provided on the meridian plane (211); a shroud (230) provided at the tip of the plurality of blades (220) so as to cover the meridian plane (211); the shroud (230) is provided with a first passage (235) that penetrates between an inner surface facing the meridian plane (211) and an outer surface facing the inner surface of the casing (100), and has a first opening (235B) on the outer surface side and a second opening (235A) on the inner surface side; the first passage (235) is inclined so that a center (235Bc) of the first opening (235B) is located closer to an inlet (200in) of the impeller (200) than a center (235Ac) of the second opening (235A) in a cross section including an axis (AX) of a rotation shaft (250) of the impeller (200); A centrifugal compressor is provided.

[0007] According to this aspect, the centrifugal compressor can, for example, allow a portion of the fluid passing through the impeller to flow into the gap between the shroud and the casing through the first passage, and circulate the fluid to the inlet side of the impeller through the gap. Therefore, while the peak efficiency of the impeller is slightly reduced, the work coefficient (i.e., impeller work) on the high-pressure / low-flow side is increased, thereby suppressing the upward-sloping slope of the pressure-flow characteristic. As a result, the centrifugal compressor can achieve an expanded operating range (so-called wide-range). Furthermore, the centrifugal compressor can suppress mild surges caused by the upward-sloping slope of the pressure-flow characteristic and can also suppress the generation of humming noise associated with mild surges. Furthermore, the centrifugal compressor can circulate the fluid from the outlet side of the impeller through, for example, the gap between the shroud and the casing and the first passage. Therefore, the centrifugal compressor can suppress wakes near the outlet of the impeller. Therefore, the centrifugal compressor can improve the performance of a closed impeller.

[0008] Furthermore, according to this aspect, in the centrifugal compressor, the first passage is inclined toward the inlet side of the impeller, and therefore, pressure loss caused by separation when the fluid circulates can be suppressed, and the effect of improving performance can be further improved.

[0009] In addition, in a second aspect of the present disclosure, based on the first aspect described above, The plurality of blades (220) a first blade (220a); a second blade (220b) adjacent to the first blade (220a) on the front side in the rotation direction (RT) of the impeller (200); In a line segment (225) that starts from one end (Ps) of the first blade (220a) on the inlet (200 in) side and forms the shortest distance between the first blade (220a) and the second blade (220b), a point that is 40 percent of the length of the line segment from the end on the first blade (220a) side is defined as a first imaginary point (P1), and a point that is 60 percent of the length of the line segment (225) from the end on the first blade (220a) side is defined as a second imaginary point (P2). The second opening (235A) may be located between a first imaginary line (VL1) extending circumferentially through the first imaginary point (P1) and a second imaginary line (VL2) extending circumferentially through the second imaginary point (P2).

[0010] In addition, in a third aspect of the present disclosure, on the premise of the first or second aspect described above, The end of the shroud (230) on the inlet (200 in) side and the casing (100) face each other in the axial direction, thereby forming a second passage (110B), In a cross section including the axis (AX), the second passage (110B) may be inclined from the outer surface side to the inner surface side of the shroud (230) toward the outlet (200out) side of the impeller (200) with respect to a direction perpendicular to the inner surface of the shroud (230).

[0011] Furthermore, in a fourth aspect of the present disclosure, based on the third aspect described above, The inlet (200 inch) end of the shroud (230) may be chamfered.

[0012] Furthermore, in a fifth aspect of the present disclosure, based on the third or fourth aspect described above, The axial width of the second passage (110B) may be narrowed from the outer surface side toward the inner surface side of the shroud (230).

[0013] In addition, in a sixth aspect of the present disclosure, on the premise of any one of the third to fifth aspects described above, The inner diameter (D2) of the inlet (200 in) end of the shroud (230) may be smaller than the inner diameter (D1) of the casing (100) at a point axially opposite the inlet (200 in) end of the shroud (230).

[0014] In addition, in a seventh aspect of the present disclosure, on the premise of any one of the first to sixth aspects described above, The tip ends of the blades (220) on the shroud (230) side may not overlap the second opening (235A).

[0015] In addition, in an eighth aspect of the present disclosure, on the premise of any one of the first to seventh aspects described above, A seal (240) may be provided between the outer surface of the shroud (230) and the casing (100).

[0016] Furthermore, in a ninth aspect of the present disclosure, based on the eighth aspect described above, The first opening (235B) may be provided closer to the inlet (200 inches) than the seal portion (240).

[0017] In addition, in a tenth aspect of the present disclosure, on the premise of any one of the first to ninth aspects described above, The first passage (235) may be provided to extend in the circumferential direction.

[0018] In addition, in an eleventh aspect of the present disclosure, on the premise of any one of the first to tenth aspects described above, The end of the shroud (230) on the inlet (200 in) side and the casing (100) face each other in the axial direction along the axis (AX), thereby forming a second passage (110B), a third passage (110A) communicating with the first passage (235) and the second passage (110B) is formed between an outer surface of the shroud (230) and an inner surface of the casing (100); In the second passage (110B) or the third passage (110A), the inner surface of the casing (100) may have protrusions (114, 115) extending in a direction perpendicular to the circumferential direction, grooves (113) extending in a direction perpendicular to the circumferential direction, or a rough surface that is rougher than the inner surface of the shroud (230).

[0019] Furthermore, in a twelfth aspect of the present disclosure, based on the above-mentioned eighth aspect, The first opening (235B) may be provided closer to the outlet (200out) of the impeller (200) than the seal portion (240).

[0020] In addition, in a thirteenth aspect of the present disclosure, on the premise of any one of the first to twelfth aspects described above, a first compression section that compresses an incoming fluid; a second compression section into which the fluid discharged from the first compression section flows and compresses the fluid, the first compression section includes another impeller having another shroud in which the first passage (235) is not provided; The second compression section may include the impeller (200) having the shroud (230) in which the first passage (235) is provided.

[0021] In addition, a fourteenth aspect of the present disclosure is a centrifugal compressor (10) including the centrifugal compressor (10) according to any one of the first to twelfth aspects described above. A refrigeration system is provided. [Effects of the Invention]

[0022] According to the above-described embodiment, it is possible to improve the performance of the closed impeller of the centrifugal compressor. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an example of a refrigeration device. [Figure 2] FIG. 2 is a diagram illustrating a configuration of an example of a compressor. [Figure 3] FIG. 1 is a diagram illustrating a first example of the structure of a compressor. [Figure 4] FIG. 1 is a diagram illustrating a first example of the structure of a compressor. [Figure 5] FIG. 4 is a diagram showing pressure-flow rate characteristics of the compressor according to the embodiment and a compressor according to a comparative example. [Figure 6] FIG. 4 is a diagram illustrating a second example of the structure of a compressor. [Figure 7] FIG. 10 is a diagram showing pressure-flow characteristics relating to a second example of the compressor structure. [Figure 8] FIG. 10 is a diagram illustrating a third example of the structure of a compressor. [Figure 9] FIG. 10 is a diagram illustrating a fourth example of the structure of a compressor. [Figure 10] FIG. 10 is a diagram illustrating a fifth example of the structure of a compressor. [Figure 11] FIG. 10 is a diagram illustrating a sixth example of the structure of a compressor. [Figure 12] FIG. 10 is a diagram illustrating a seventh example of the structure of a compressor. [Figure 13] FIG. 10 is a diagram illustrating an eighth example of the structure of a compressor. [Figure 14] FIG. 10 is a diagram illustrating a ninth example of the structure of a compressor. [Figure 15] FIG. 19 is a diagram illustrating a tenth example of the structure of a compressor. [Figure 16] FIG. 11 is a diagram illustrating an eleventh example of the structure of a compressor. [Figure 17] FIG. 12 is a diagram illustrating a twelfth example of the structure of a compressor. [Figure 18] FIG. 13 is a diagram illustrating a thirteenth example of the structure of a compressor. [Figure 19] FIG. 14 is a diagram illustrating a fourteenth example of the structure of a compressor. [Figure 20] FIG. 15 is a diagram illustrating a fifteenth example of the structure of a compressor. [Figure 21] FIG. 16 is a diagram illustrating a sixteenth example of the structure of a compressor. [Figure 22]FIG. 17 is a diagram illustrating a seventeenth example of the structure of a compressor. [Figure 23] FIG. 19 is a diagram illustrating an eighteenth example of the structure of a compressor. [Figure 24] FIG. 20 is a diagram illustrating a 19th example of the structure of a compressor. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment will be described with reference to the drawings.

[0025] [Configuration of refrigeration equipment] The configuration of a refrigeration device 1 according to this embodiment will be described with reference to FIG.

[0026] FIG. 1 is a diagram showing the configuration of an example of a refrigeration device 1. As shown in FIG.

[0027] The refrigeration device 1 circulates a refrigerant through a refrigerant circuit RC, and uses a compression refrigeration cycle to cool or heat a target liquid or gas.

[0028] The refrigeration device 1 is, for example, a chiller that cools a target liquid (liquid to be cooled) by heat exchange between a refrigerant and the target liquid using a compression refrigeration cycle. The liquid to be cooled is, for example, water or brine. The refrigeration device 1 may also be a water heater that produces hot water by heat exchange between a refrigerant and water using a compression refrigeration cycle. The refrigeration device 1 may also be, for example, an air conditioner that cools or heats a target space by heat exchange between a refrigerant and air. The following explanation will focus on the case where the refrigeration device 1 is a chiller.

[0029] As shown in FIG. 1, the refrigeration device 1 includes refrigerant paths L1 to L4, a compressor 10, a heat exchanger 20, an expansion mechanism 30, and a heat exchanger 40 as components of a refrigerant circuit RC.

[0030] The refrigerant paths L1 to L4 are paths through which the refrigerant flows. The refrigerant paths L1 to L4 are, for example, pipes made of a metal such as steel.

[0031] Refrigerant path L1 connects the heat exchanger 40 and the suction port of the compressor 10. Refrigerant path L2 connects the discharge port of the compressor 10 and the heat exchanger 20. Refrigerant path L3 connects the heat exchanger 20 and the expansion mechanism 30. Refrigerant path L4 connects the expansion mechanism 30 and the heat exchanger 40.

[0032] The compressor 10 compresses the low-pressure refrigerant flowing in from the refrigerant path L1 and discharges the high-pressure refrigerant into the refrigerant path L2.

[0033] The heat exchanger 20 exchanges heat between a refrigerant flowing inside and an external heat medium (for example, cooling water).

[0034] The heat exchanger 20 is a so-called condenser, which condenses the high-temperature, high-pressure refrigerant compressed by the compressor 10 and flowing in from the refrigerant path L2 by heat exchange with an external heat medium, and then discharges the high-pressure liquid refrigerant into the refrigerant path L3.

[0035] The expansion mechanism 30 expands the high-pressure liquid refrigerant and discharges a low-pressure refrigerant in a gas-liquid mixed state. The expansion mechanism 30 is, for example, an expansion valve or an orifice.

[0036] The expansion mechanism 30 expands the high-pressure liquid refrigerant that flows in from the refrigerant path L3 and has passed through the heat exchanger 20, and causes the low-pressure refrigerant in a gas-liquid mixed state to flow into the refrigerant path L4.

[0037] The heat exchanger 40 exchanges heat between the refrigerant flowing inside and the liquid to be cooled outside.

[0038] The heat exchanger 40 is a so-called evaporator that evaporates the low-pressure gas-liquid mixed refrigerant that flows in from the refrigerant path L4 and has been expanded by the expansion mechanism 30 by absorbing heat from the liquid to be cooled, and causes the low-pressure gas refrigerant to flow into the refrigerant path L1. This allows the refrigeration device 1 to cool the liquid to be cooled.

[0039] [Compressor configuration] Next, the configuration of the compressor 10 according to this embodiment will be described with reference to FIG.

[0040] FIG. 2 is a diagram showing an example of the configuration of the compressor 10. As shown in FIG.

[0041] 2 shows a cross section taken along a plane including the axis AX of the rotary shaft 250 so that the contents inside the casing 100 are exposed.

[0042] Hereinafter, the direction along the axis AX of the rotating shaft 250, i.e., the direction parallel to it, will be referred to as the "axial direction," and explanations may be given using the terms "axial direction," as well as "radial direction" and "circumferential direction" based on the axis AX.

[0043] As shown in FIG. 2, in this example, the compressor 10 is a centrifugal compressor.

[0044] The compressor 10 has, for example, one stage (single stage) as shown in Fig. 2. The compressor 10 may have two or more stages, and the multi-stage compressor 10 has multiple compression sections, each including an impeller 200, arranged in series.

[0045] The compressor 10 includes a casing 100 , an impeller 200 , a rotating shaft 250 , an electric motor 300 , a radial magnetic bearing 400 , a thrust magnetic bearing 500 , and a touchdown bearing 600 .

[0046] The casing 100 is a housing for accommodating and mounting the components of the compressor 10 therein.

[0047] The impeller 200 is housed in an impeller chamber 110 formed inside the casing 100 .

[0048] Impeller 200 is attached to a rotary shaft 250 and rotates around an axial center AX of rotary shaft 250. Impeller 200 is formed so that the outer diameter of its outer surface (meridian plane 211, described later) increases from one axial end (the right end in the drawing in this example) to the other axial end (the left end in the drawing in this example). Impeller 200 causes the refrigerant that flows in along the axial direction from suction pipe 120 at the circumferential center of one axial end to flow out radially outward at the other axial end. A diffuser 111 is provided radially outward from the other radial end of impeller 200. In diffuser 111, the dynamic pressure (i.e., kinetic energy) of the refrigerant flowing out from impeller 200 is converted into static pressure (i.e., pressure energy), and the compressed refrigerant flows out from diffuser 111 to discharge pipe 130.

[0049] The electric motor 300 is housed in an electric motor chamber 140 formed inside the casing 100 .

[0050] Electric motor 300 uses externally supplied power to rotate impeller 200. Electric motor 300 is, for example, a permanent magnet synchronous motor. Electric motor 300 is an inner rotor type and includes a rotor 310 attached to rotating shaft 250, and a stator 320 disposed radially outside rotor 310 and fixed to the inner circumferential surface of motor chamber 140 in casing 100.

[0051] The radial magnetic bearings 400 use electromagnetic force to support the radial load of the rotating shaft 250 in a non-contact manner. Two radial magnetic bearings 400 are provided, each fixed to the inner surface of the casing 100. The two radial magnetic bearings 400 are arranged adjacent to each other at both ends of the electric motor 300 in the axial direction.

[0052] Thrust magnetic bearing 500 supports the thrust load of rotating shaft 250 in a non-contact manner by using electromagnetic force. Thrust magnetic bearing 500 includes a pair of electromagnets 510, each fixed to the inner surface of casing 100. The pair of electromagnets 510 are arranged adjacent to each end in the axial direction of a disk-shaped collar 260 centered on axis AX, which is provided on rotating shaft 250. Collar 260 is made of a magnetic material, and thrust magnetic bearing 500 maintains the position of rotating shaft 250, which is integral with collar 260, in a non-contact manner by the magnetic attraction force of the pair of electromagnets 510 to collar 260.

[0053] The touchdown bearing 600 is provided to prevent contact between the rotating shaft 250 and the radial magnetic bearing 400, and between the collar 260 and the electromagnet 510 of the thrust magnetic bearing 500. The touchdown bearing 600 is configured, for example, mainly from an angular contact ball bearing.

[0054] [First example of compressor structure] Next, a first example of the structure of the compressor 10 according to this embodiment will be described with reference to FIGS.

[0055] 3 and 4 are diagrams illustrating a first example of the compressor 10. Specifically, FIG. 3 is a perspective view of the impeller 200 of the compressor 10 according to this example. FIG. 4 is a cross-sectional view of the compressor 10 according to this example, taken along a plane including the axis AX of the rotating shaft 250. Similar cross-sectional views are also shown in FIGS. 8 to 17 and 20 to 24, which will be described later. FIG. 5 is a diagram illustrating pressure-flow characteristics of the compressor 10 according to the embodiment and a compressor according to a comparative example. In FIG. 5, a surge line 501 and a pressure-flow characteristic line 502 are plotted for the compressor according to the comparative example, and a surge line 511 and a pressure-flow characteristic line 512 are plotted for the compressor 10 according to this embodiment.

[0056] The compressor according to the comparative example differs from the compressor 10 according to the present example in that it does not have a through hole 235, which will be described later, but is the same as the compressor 10 according to the present example in other respects.

[0057] 4, impeller 200 is disposed in impeller chamber 110 formed inside casing 100. Impeller 200 is driven to rotate by electric motor 300 via rotary shaft 250, causing refrigerant in suction pipe 120 to flow in from inlet 200in at one axial end and to flow out from outlet 200out at the other axial end toward diffuser 111 on the radially outer side.

[0058] As shown in FIGS. 3 and 4, in this example, the impeller 200 is a so-called closed impeller, and includes a hub 210, blades 220, and a shroud 230.

[0059] The blades 220 are provided on a meridian plane 211, which is the outer surface of the hub 210. There are a plurality of blades 220, and the plurality of blades 220 are arranged in the circumferential direction. The plurality of blades 220 may be arranged at equal intervals in the circumferential direction, or may be arranged at unequal intervals.

[0060] The shroud 230 is provided to be connected to the tips of the blades 220 so as to cover the meridian plane 211 of the hub 210. The shroud 230 is formed so that the outer diameter of the shroud 230, centered on the axis center AX, increases as a whole in the axial direction from the inlet 200in side of the impeller 200 toward the outlet 200out. For example, as shown in FIG. 4 , the shroud 230 has, in the axial direction, a first section that starts at the inlet 200in of the impeller 200 and has a constant outer diameter centered on the axis center AX of the rotating shaft 250, and a second section that starts at the rear end of the first section and has an increasing outer diameter centered on the axis center AX. Alternatively, the shroud 230 may be formed so that the outer diameter of the shroud 230, centered on the axis center AX of the rotating shaft 250, increases continuously in the axial direction from the inlet 200in toward the outlet 200out of the impeller 200.

[0061] In this example, suction pipe 120 is formed inside casing 100. For example, inner surface 100A of casing 100 corresponding to suction pipe 120 has a constant diameter (inner diameter) centered on axis AX of rotating shaft 250. The inner diameter of inner surface 100A of casing 100 is the same as the diameter (inner diameter) of the inner surface of shroud 230 at inlet 200 in of impeller 200, for example, as shown in FIG.

[0062] A step surface 100C is provided between the inner surfaces 100A and 100B of the casing 100, and the step surface 100C faces an end surface 230A on the inlet 200in side of the shroud 230. In this example, the step surface 100C is a flat surface perpendicular to the axial direction.

[0063] End surface 230A of shroud 230 is a flat surface perpendicular to the axial direction, similar to stepped surface 100C, so the distance between stepped surface 100C and shroud 230 is constant in the radial direction.

[0064] The shroud 230 is provided with a through hole 235 that passes through between its inner and outer surfaces.

[0065] 4, through-hole 235 is provided in shroud 230 at a position relatively close to inlet 200in of impeller 200 in a cross section including axis AX, and is formed so as to linearly penetrate between the inner and outer surfaces of shroud 230. In this example, through-hole 235 is provided in the first section of shroud 230. As a result, through-hole 235 can communicate between the space inside shroud 230 and inlet 200in of impeller 200 via space 110A between shroud 230 and inner surface 100B of casing 100, and space 110B between end face 230A of shroud 230 and step surface 100C. Therefore, a portion of the refrigerant flowing into the impeller 200 can be circulated to the inlet 200in of the impeller 200 through the through-holes 235, the space 110A, and the space 110B, and can be merged with the main flow flowing into the impeller 200.

[0066] 5 (pressure-flow rate characteristic line 512), the compressor 10 can obtain a high pressure in a region where the discharge flow rate Q is relatively low (see pressure difference 513) compared to the pressure-flow rate characteristic 502 of the compressor according to the comparative example in which the through-hole 235 is not provided. Also, the compressor 10 can achieve an expanded (i.e., wider) operating region (see region 514) compared to the pressure-flow rate characteristic 502 of the compressor according to the comparative example in which the through-hole 235 is not provided.

[0067] 5, the pressure-flow rate characteristic 502 of the compressor according to the comparative example includes a region 503 of the discharge flow rate Q having an upward-sloping characteristic in which the pressure P increases in accordance with an increase in the discharge flow rate Q. In the region 503 having the upward-sloping characteristic, a local backflow phenomenon called a mild surge occurs, which may result in a whirring noise from the impeller 200.

[0068] In contrast, in this example, as described above, the pressure in the region where the discharge flow rate Q is relatively low can be increased, thereby increasing the work of the impeller 200, and as a result, the upward-sloping characteristic in the region 503 can be suppressed (in the example of FIG. 5, the upward-sloping characteristic can be eliminated). Therefore, the whirring noise of the impeller 200 can be suppressed.

[0069] 3, the through-holes 235 are provided in the entire circumferential direction, i.e., around the entire circumference, and are formed in the shape of slits extending in the circumferential direction, thereby making it possible to increase the flow rate circulating through the through-holes 235 to the inlet 200in of the impeller 200.

[0070] Through hole 235 includes opening 235A on the inner surface side of shroud 230 and opening 235B on the outer surface side of shroud 230. In this example, through hole 235 has a constant width (axial dimension) in a cross section including axis AX, and openings 235A and 235B have the same width.

[0071] A seal member 240 is provided in the gap between the shroud 230 and the inner surface 100B of the casing 100 corresponding to the impeller chamber 110. The seal member 240 is, for example, a non-contact seal member such as a labyrinth seal. Alternatively, the seal member 240 may be a sliding seal member.

[0072] In this example, the seal member 240 is provided closer to the outlet 200out of the impeller 200 than the opening 235B of the through hole 235. As a result, the seal member 240 can partition the space between the shroud 230 and the inner surface 100B of the casing 100, between the inner surface 100B that communicates with the through hole 235 and a space closer to the outlet 200out of the impeller 200 than the seal member 240. Therefore, the seal member 240 can suppress the circulation of the refrigerant from the outlet 200out to the inlet 200in of the impeller 200 through the space between the shroud 230 and the inner surface 100B of the casing 100. Therefore, the compressor 10 can suppress an increase in loss due to the generation of an excessive circulation flow and can achieve both the above-mentioned effect and efficiency due to the action of the through hole 235.

[0073] Furthermore, through hole 235 is provided so as to incline toward inlet 200in of impeller 200 with respect to a direction perpendicular to the inner surface of shroud 230. Specifically, in a cross section including axis AX, center 235Bc of opening 235B is positioned closer to inlet 200in of impeller 200 than center 235Ac of opening 235A. This makes it possible to suppress separation that occurs at the outer edge of opening 235B of through hole 235 when refrigerant flows into space 110B from through hole 235, and as a result, it is possible to suppress a reduction in the effective flow path cross-sectional area. Therefore, compressor 10 can increase the flow rate circulating to inlet 200in of impeller 200 through through hole 235, thereby further improving the effect of through hole 235.

[0074] Furthermore, for example, if opening 235B of through-hole 235 is positioned closer to outlet 200out of impeller 200 in the axial direction, it may be necessary to dispose seal member 240 at a location where the rate of expansion of the outer diameter of shroud 230 along the axial direction is relatively large. In this case, the gap between seal member 240 and the outer surface of shroud 230 increases, which may increase the amount of refrigerant leaking from outlet 200out of impeller 200 through the gap between shroud 230 and inner surface 100B of casing 100 to inlet 200in of impeller 200, potentially resulting in a decrease in efficiency of compressor 10. Furthermore, in order to reduce the gap between seal member 240 and the outer surface of shroud 230, it may be necessary to modify the shape of the outer surface of shroud 230, which may result in an increase in inertia of impeller 200 and an increase in cost.

[0075] In contrast, in this example, because the through-hole 235 is inclined toward the inlet 200in of the impeller 200, the position of the opening 235B of the through-hole 235 can be disposed closer to the inlet 200in of the impeller 200 in the axial direction. Therefore, the seal member 240 can be disposed closer to the inlet 200in of the impeller 200 in the axial direction, which makes it less likely that the seal member 240 will be disposed in a location where the rate of expansion of the outer diameter of the shroud 230 in the axial direction is relatively large. Therefore, the compressor 10 can suppress problems such as a decrease in efficiency, an increase in the inertia of the impeller 200, and an increase in costs, which are caused by an increase in the amount of leakage of the fluid that flows from the outlet 200out side of the impeller 200 into the space between the shroud 230 and the inner surface 100B of the casing 100 toward the inlet 200in of the impeller 200.

[0076] The degree of inclination of through hole 235 (for example, inclination angle θ1) is determined taking into consideration, for example, the viewpoint of suppressing separation occurring at the outer edge of opening 235B of through hole 235 and the viewpoint of ease of flow of refrigerant into through hole 235 from the main stream inside impeller 200. This is because the greater the degree of inclination of through hole 235, the less likely separation occurs at the outer edge of opening 235B of through hole 235, while the smaller the degree of inclination of through hole 235, the more likely the main stream refrigerant passing inside shroud 230 will flow into through hole 235.

[0077] The inclination angle θ1 is the angle formed between a line (reference line) perpendicular to the inner or outer surface of the shroud 230 at the location where the through hole 235 is located and the center line of the through hole 235 in a cross section including the axis center AX. The reference line is, for example, a line that passes through the center 235Ac of the opening 235A and is perpendicular to the line segment connecting both ends of the opening 235A in a cross section including the axis center AX. The center line of the through hole 235 is a line that continuously connects the centers of the through hole 235 at each position along the reference line between the opening 235A and the opening 235B in the cross section including the axis center AX. In this example, the center line of the through hole 235 is a line that connects the center 235Ac of the opening 235A and the center 235Bc of the opening 235B.

[0078] For example, by prioritizing ease of flow of the mainstream refrigerant into through hole 235, inclination angle θ1 of through hole 235 is set to a range of 10 degrees or greater. Alternatively, by prioritizing prevention of separation occurring at the outer edge of opening 235B of through hole 235, inclination angle θ1 of through hole 235 may be set to a range of 30 degrees or greater. Alternatively, by achieving a balance between ease of flow of the mainstream refrigerant into through hole 235 and prevention of separation occurring at the outer edge of opening 235B of through hole 235, inclination angle θ1 of through hole 235 may be set to a range of 20 degrees or greater.

[0079] Furthermore, as described above, the compressor 10 may be a multi-stage compressor. In this case, the higher the pressure, i.e., the lower the operating point, the higher the load of the downstream compressor section becomes compared to the upstream compressor section. As a result, downstream compressor sections are generally more susceptible to mild surge or surge than upstream compressor sections. Therefore, in order to widen the operating range of the compressor section, the impeller 200 of this embodiment is adopted in the downstream compressor section, and the shroud 230 is provided with the through-hole 235. However, in order to improve efficiency, the shroud of the impeller in the upstream compressor section may not be provided with the through-hole 235. Specifically, the through-hole 235 may be provided in the shroud 230 only in at least one compressor section downstream of the first compressor section among the multiple compressor sections. For example, the compressor 10 includes a first compressor section into which a refrigerant flows and a second compressor section into which a refrigerant discharged from the first compressor section flows. An impeller having no through-holes 235 in the shroud is used in the first compression section, and an impeller 200 having through-holes 235 in the shroud 230 is used in the second compression section. Alternatively, impellers 200 having through-holes 235 in the shroud 230 may be used in all compression sections of the multiple-stage compression sections, prioritizing a wide range of the compression sections.

[0080] [Second example of compressor structure] Next, a second example of the structure of the compressor 10 according to this embodiment will be described with reference to FIGS.

[0081] Hereinafter, the same reference numerals will be used to designate the same or corresponding components as in the first example described above, and the description will focus on the parts that are different from the first example described above, and the description of the parts that are the same or corresponding to the first example described above may be omitted. In the following description of the third to twentieth examples described below, the same correspondence will be used in relation to the examples already described.

[0082] FIG. 6 is a diagram illustrating a second example of the structure of the compressor 10. Specifically, FIG. 6 is a development view of the meridian plane 211 and the base ends of the blades 220 of the impeller 200 developed around the axis AX. FIG. 7 is a diagram illustrating pressure-flow characteristics related to the second example of the structure of the compressor 10. FIG. 7 includes pressure-flow characteristics 701 of the compressor 10 according to this example and pressure-flow characteristics 702 and 703 of compressors according to two comparative examples. The pressure-flow characteristics 702 correspond to the comparative example in which the entire opening 235A of the through-hole 235 is located in the region 602 adjacent to the inlet 200in side of the impeller 200 relative to the region 601 in FIG. 6 . The pressure-flow characteristics 703 correspond to the comparative example in which the entire opening 235A of the through-hole 235 is located in the region 603 adjacent to the outlet 200out side of the impeller 200 relative to the region 601. 7 also includes a comparative example of FIG. 5, that is, a pressure-flow characteristic 502 of a compressor in which the through-hole 235 is not provided.

[0083] In Figure 6, two blades 220 are selected as representatives from the multiple blades 220, and for convenience, the blade 220 on the rear side in the rotation direction RT is referred to as "blade 220a" and the blade 220 on the front side in the rotation direction RT is referred to as "blade 220b."

[0084] The compressor 10 of this example differs from the first example described above in that the position of the opening 235A of the through hole 235 is determined in relation to the arrangement of the blades 220 of the impeller 200, but may be the same as the first example described above in other respects.

[0085] As shown in FIG. 6, in this example, the through-hole 235 is provided so that part or all of the opening 235A is located above a region 601 that includes an imaginary line VL0 that extends from the center P0 of the throat 225 in the circumferential direction.

[0086] The throat 225 is a line segment that starts at one end (imaginary point Ps) of the blade 220a on the inlet 200in side and corresponds to the shortest distance to the blade 220b on the meridian plane 211. In other words, the throat 225 is a line segment that connects the imaginary point Ps on the blade 220a and the imaginary point Pe on the blade 220b that corresponds to the position at the shortest distance from the imaginary point Ps on the meridian plane 211.

[0087] Region 601 is a region between imaginary lines VL1 and VL2 extending in the circumferential direction, and imaginary lines VL1 and VL2 are arranged so as to sandwich imaginary line VL0 in the axial direction. For example, imaginary line VL1 is an imaginary line that extends in the circumferential direction from imaginary point P1, which is 40% of the length of throat 225, starting from imaginary point Ps, on throat 225. Also, for example, imaginary line VL2 is an imaginary line that extends in the circumferential direction from imaginary point P1, which is 60% of the length of throat 225, starting from imaginary point Ps, on throat 225.

[0088] 7, pressure-flow characteristics 702 and 703 of the comparative example, in which regions 602 and 603 each include the entire opening 235A of through-hole 235, have a relatively low pressure in the low flow rate region. This is because when opening 235A of through-hole 235 is located in region 602, region 602 is relatively close to inlet 200in of impeller 200, so the pressure of the refrigerant circulating through through-hole 235 is relatively low, and the effect of the circulating flow on increasing the pressure of impeller 200 is limited. Also, when opening 235A of through-hole 235 is located in region 603, region 603 is relatively close to outlet 200out of impeller 200, so the pressure of the refrigerant circulating through through-hole 235 is relatively high, resulting in a significant decrease in the efficiency of impeller 200.

[0089] In contrast, in this example, the flow rate of the circulation flow can be optimized by arranging the opening 235A of the through-hole 235 so that part or all of it is included above the region 601. Therefore, as shown in Fig. 7, the pressure in the low flow rate region is relatively high in the pressure flow rate characteristic 701 of the compressor 10. Therefore, by increasing the pressure in the low flow rate region, the above-mentioned upward sloping characteristic can be suppressed.

[0090] [Third example of compressor structure] Next, a third example of the compressor 10 according to the present embodiment will be described with reference to FIG.

[0091] FIG. 8 is a diagram illustrating a third example of the compressor 10. As shown in FIG.

[0092] As shown in FIG. 8, the compressor 10 of this example differs from the first and second examples described above in that the through-hole 235 passes through a curved path between the inner and outer surfaces of the shroud 230, but may be the same as the first or second example described above in other respects.

[0093] In this example, through hole 235 is curved such that its center line inclines toward inlet 200in of impeller 200 as it moves from opening 235A to opening 235B. In other words, through hole 235 is curved such that inclination angle θ1 increases as it moves from opening 235A to opening 235B. This allows the inclination angle θ1 at opening 235B to be set relatively large. This further reduces separation of the refrigerant inside shroud 230 when it flows into space 110A through through hole 235. Furthermore, within the manufacturing constraints of through hole 235, the inclination angle θ1 at opening 235A and the inclination angle θ1 at opening 235B can be set separately. This allows the inclination angle θ1 at opening 235A to be set relatively small, while the inclination angle θ1 at opening 235B to be set relatively large, within the manufacturing constraints of through hole 235. Therefore, it is possible to optimize the ease with which the main flow of refrigerant flows into the through-hole 235 and the suppression of separation that occurs at the outer edge of the opening 235B of the through-hole 235.

[0094] [Fourth example of compressor structure] Next, a fourth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0095] FIG. 9 is a diagram illustrating a fourth example of the compressor 10. As shown in FIG.

[0096] As shown in FIG. 9, the compressor 10 of this example differs from the first to third examples described above in that the corners of the outer edges of the openings 235A, 235B of the through-hole 235 are curved and chamfered, but in other respects it may be the same as the first or second example described above.

[0097] In this example, chamfers 235C and 235D are applied to the corners of the outer edges of openings 235A and 235B of through-hole 235 on the inlet 200in side of impeller 200. Chamfers 235C and 235D are, for example, rounded chamfers.

[0098] This makes it possible to suppress separation at the outer edge of opening 235A when the main stream of refrigerant inside shroud 230 flows into through-hole 235, and also makes it possible to suppress separation at the outer edge of opening 235B when refrigerant flows from through-hole 235 into space 110A.

[0099] [5th ​​example of compressor structure] Next, a fifth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0100] FIG. 10 is a diagram showing the structure of a fifth example of the compressor 10. In FIG.

[0101] As shown in FIG. 10, the compressor 10 of this example differs from the first to fourth examples described above in that the end surface 230A of the shroud 230 is inclined toward the inside of the impeller 200, but may be the same as any one of the first to fourth examples described above in other respects.

[0102] The end face 230A of the shroud 230 is a plane that is inclined so that the end point on the inner surface side of the shroud 230 is closer to the inside of the impeller 200 (in other words, closer to the outlet 200out side of the impeller 200) than the end point on the outer surface side in a cross section including the axis AX.

[0103] This allows the circulation flow in space 110B to have a component in the same direction as the main flow near inlet 200in of impeller 200. Therefore, separation at end surface 230A of shroud 230 can be suppressed when the circulation flow of refrigerant passing through through holes 235 joins the main flow of refrigerant from space 110B near the inlet of impeller 200, and pressure loss can be reduced. Furthermore, backflow occurring at the ends of blades 220 of impeller 200 can be suppressed by the circulation flow joining the main flow from space 110B near inlet 200in of impeller 200.

[0104] The greater the degree of inclination of end face 230A of shroud 230 (e.g., inclination angle θ2), the smaller the difference in flow direction between the mainstream and circulating flows, thereby suppressing losses associated with the merging of the mainstream and circulating flows and the resulting mixing of refrigerant.On the other hand, the smaller the degree of inclination of end face 230A of shroud 230, the smaller the angle of deflection of the circulating flow from space 110A to space 110B, thereby suppressing losses associated with separation at the corner between the outer surface of shroud 230 and end face 230A.

[0105] The inclination angle θ2 is the angle formed between a line perpendicular to the inner surface of the shroud 230 and the end surface 230A of the shroud 230 in a cross section including the axis AX.

[0106] For example, by prioritizing suppression of loss due to the joining of the main flow and the circulation flow, the inclination angle θ2 of the end face 230A of the shroud 230 is set to a range of 30 degrees or greater. Alternatively, by prioritizing suppression of loss due to separation of the circulation flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ2 of the end face 230A of the shroud 230 may be set to a range of 10 degrees or greater. Alternatively, by achieving a balance between suppression of loss due to the joining of the main flow and the circulation flow and suppression of loss due to separation of the circulation flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ2 of the end face 230A of the shroud 230 may be set to a range of 20 degrees or greater.

[0107] The degree of inclination of end surface 230A of shroud 230 may be indirectly determined from the condition of the degree of inclination (for example, inclination angle θ3) of space 110B serving as a passage for the coolant.

[0108] In this example, due to the inclination of end face 230A of shroud 230, the direction of the circulation flow of the refrigerant passing through space 110B is inclined from the outer surface of shroud 230 toward the inner surface, toward outlet 200out of impeller 200, with respect to the direction perpendicular to the inner surface of shroud 230. Therefore, space 110B as a refrigerant passage can be considered to be inclined from the outer surface of shroud 230 toward the inner surface, toward outlet 200out of impeller 200, with respect to the direction perpendicular to the inner surface of shroud 230.

[0109] The inclination angle θ3 is defined as, for example, an angle formed between a line (reference line) perpendicular to the inner surface of one end of the shroud 230 on the inlet 200in side of the impeller 200 and the center line of the space 110B serving as a refrigerant passage in a cross section including the axis AX. The center line of the space 110B serving as a refrigerant passage is a line that continuously connects the centers of the width of the space 110B at each position along the reference line between one end of the space 110B on the outer surface side of the shroud 230 and the other end on the inner surface side of the shroud 230. The width of the space 110B is the width of the space 110B in a direction perpendicular to the reference line. In this example, the center line of the space 110B serving as a refrigerant passage is a straight line connecting the center of the width of the space 110B at one end of the shroud 230 on the outer surface side and the center of the width of the space 110B at the other end of the shroud 230 on the inner surface side.

[0110] For example, by prioritizing suppression of loss due to the merging of the main flow and the circulation flow, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 30 degrees or greater. Alternatively, by prioritizing suppression of loss due to separation of the circulation flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 10 degrees or greater. Alternatively, by achieving a balance between suppression of loss due to the merging of the main flow and the circulation flow and suppression of loss due to separation of the circulation flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 20 degrees or greater.

[0111] In this example, the inclination angle θ2 is twice the inclination angle θ3, so the value twice the inclination angle θ3 defined above can be defined as the inclination angle θ2.

[0112] [Sixth example of compressor structure] Next, a sixth example of the compressor 10 according to the present embodiment will be described with reference to FIG.

[0113] FIG. 11 is a diagram showing a sixth example of the structure of the compressor 10. In FIG.

[0114] As shown in FIG. 11, the compressor 10 according to this example differs from the fifth example described above in that the end surface 230A of the shroud 230 is a curved surface, but may be the same as the fifth example described above in other respects.

[0115] End surface 230A of shroud 230 is inclined as in the case of the above-mentioned fifth example, and has a curved shape such that the degree of inclination (for example, inclination angles θ2, θ3) increases from the outer surface of shroud 230 toward the inner surface.

[0116] As a result, the compressor 10 can improve the effect of suppressing separation when the refrigerant circulation flow merges with the main flow from the space 110B and the effect of suppressing backflow at the ends of the blades 220 of the impeller 200.

[0117] In this example, the degree of inclination (inclination angles θ2, θ3) of the end surface 230A of the shroud 230 and the space 110B as a passage for the refrigerant is evaluated at one end on the inner surface of the shroud 230, i.e., near the point where the refrigerant flow joins the main flow, and may be defined in a manner similar to that of the sixth example described above.

[0118] [Seventh example of compressor structure] Next, a seventh example of the compressor 10 according to the present embodiment will be described with reference to FIG.

[0119] FIG. 12 is a diagram showing a seventh example of the structure of the compressor 10. In FIG.

[0120] As shown in FIG. 12, the compressor 10 of this example differs from the first to sixth examples described above in that the corners of the outer edge of the end face 230A of the shroud 230 are chamfered in a curved shape, but in other respects may be the same as the fifth example described above.

[0121] The corners between the end face 230A of the shroud 230 and the outer and inner surfaces of the shroud 230 are chamfered 230B and 230C, respectively.

[0122] This makes it possible to suppress separation of the circulating flow of the refrigerant and also to suppress pressure loss.

[0123] [8th example of compressor structure] Next, an eighth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0124] FIG. 13 is a diagram showing an eighth example of the structure of the compressor 10. In FIG.

[0125] As shown in FIG. 13, the compressor 10 of this example differs from the first to seventh examples described above in that the step surface 100C is inclined from the inner surface 100B side toward the inner surface 100A side so as to approach the end surface 230A of the shroud 230, but in other respects may be the same as any one of the first to fourth examples described above.

[0126] In this example, the step surface 100C is a plane that forms an acute angle with both the inner surface 100A corresponding to the suction pipe 120 and the inner surface 100B corresponding to the impeller chamber 110 in a plane including the axis AX.

[0127] This allows the circulation flow in space 110B to have a component in the same direction as the main flow near inlet 200in of impeller 200. Therefore, separation at end surface 230A of shroud 230 can be suppressed when the circulation flow of refrigerant passing through through holes 235 joins the main flow of refrigerant from space 110B near the inlet of impeller 200, and pressure loss can be reduced. Furthermore, backflow occurring at the ends of blades 220 of impeller 200 can be suppressed by the circulation flow joining the main flow from space 110B near inlet 200in of impeller 200.

[0128] Furthermore, as step surface 100C approaches end surface 230A of shroud 230 from inner surface 100B toward inner surface 100A, the width of space 110B serving as a refrigerant passage becomes smaller as it approaches the junction where the refrigerant circulating flow joins the mainstream. Specifically, width t2 of space 110B serving as a refrigerant passage at one end on inner surface 100A side is smaller than width t2 at the other end on inner surface 100A side.

[0129] This increases the dynamic pressure of the circulating flow, facilitating the merging of the circulating flow with the mainstream. In addition, by increasing the dynamic pressure of the circulating flow, the circulating flow can strengthen its ability to push back against the flow that tries to flow backward in the mainstream, thereby suppressing the backward flow in the mainstream.

[0130] The greater the inclination of the step surface 100C (for example, the inclination angle θ4), the smaller the difference in flow direction between the mainstream and circulating flows, thereby suppressing losses associated with the merging of the mainstream and circulating flows and the resulting mixing of the refrigerant.On the other hand, the smaller the inclination of the step surface 100C, the smaller the angle at which the circulating flow turns from the space 110A to the space 110B, thereby suppressing losses associated with separation at the corner between the outer surface of the shroud 230 and the end surface 230A.

[0131] The inclination angle θ4 is the angle formed by a line perpendicular to the inner surface of the shroud 230 at one end on the inlet 200in side of the impeller 200 and the step surface 100C in a cross section including the axis AX.

[0132] For example, by prioritizing suppression of loss due to the joining of the main flow and the circulating flow, the inclination angle θ4 of the step surface 100C is set to a range of 30 degrees or greater. Alternatively, by prioritizing suppression of loss due to separation of the circulating flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ4 of the step surface 100C may be set to a range of 10 degrees or greater. Alternatively, by balancing the suppression of loss due to the joining of the main flow and the circulating flow and the suppression of loss due to separation of the circulating flow at a corner between the outer surface of the shroud 230 and the end face 230A, the inclination angle θ4 of the step surface 100C may be set to a range of 20 degrees or greater.

[0133] The degree of inclination of the step surface 100C may be indirectly determined from the condition of the degree of inclination (for example, the inclination angle θ3) of the space 110B serving as a passage for the coolant.

[0134] In this example, due to the inclination of step surface 100C, the direction of the circulation flow of the refrigerant passing through space 110B is inclined from the outer surface of shroud 230 toward the inner surface, toward outlet 200out of impeller 200, with respect to the direction perpendicular to the inner surface of shroud 230. Therefore, space 110B as a refrigerant passage can be considered to be inclined from the outer surface of shroud 230 toward the inner surface, toward outlet 200out of impeller 200, with respect to the direction perpendicular to the inner surface of shroud 230.

[0135] For example, by prioritizing suppression of loss due to the merging of the mainstream and circulating flows, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 30 degrees or greater. Alternatively, by prioritizing suppression of separation or the like at the corner between the outer surface of the shroud 230 and the end face 230A of the circulating flow, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 10 degrees or greater. Alternatively, by balancing the manufacturability of the casing 100 with suppression of loss due to separation when the circulating flow merges with the mainstream, the inclination angle θ3 of the space 110B serving as the refrigerant passage may be set to a range of 20 degrees or greater.

[0136] In this example, the inclination angle θ4 is twice the inclination angle θ3, so the value twice the inclination angle θ3 defined above can be defined as the inclination angle θ4.

[0137] [9th example of compressor structure] Next, a ninth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0138] FIG. 14 is a diagram illustrating a ninth example of the structure of the compressor 10. In FIG.

[0139] As shown in FIG. 14, the compressor 10 according to this example differs from the first to eighth examples described above in that the step surface 100C is a curved surface, but may be the same as the eighth example described above in other respects.

[0140] In this example, the step surface 100C of the casing 100 is inclined in the same manner as in the eighth example described above, and has a curved shape in which the degree of inclination (e.g., inclination angle θ4) increases from the inner surface 100B side toward the inner surface 100A side in a cross section including the axis AX.

[0141] As a result, the compressor 10 can improve the effect of suppressing separation when the refrigerant circulation flow merges with the main flow from the space 110B and the effect of suppressing backflow at the ends of the blades 220 of the impeller 200.

[0142] In this example, the degree of inclination (inclination angles θ3, θ4) of the end face 230A of the shroud 230 and the space 110B as a passage for the refrigerant is evaluated at one end of the inner surface of the shroud 230, i.e., near the point where the refrigerant flow joins the main flow, and may be defined in a manner similar to the eighth example described above.

[0143] [10th example of compressor structure] Next, a tenth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0144] FIG. 15 is a diagram showing a tenth example of the structure of the compressor 10. In FIG.

[0145] As shown in Figure 15, the compressor 10 of this example differs from the first to ninth examples described above in that the connection portion between the step surface 100C and the inner surface 100A and the connection portion between the step surface 100C and the inner surface 100B are formed in a curved shape, but may be the same as the ninth example described above in other respects.

[0146] In this example, a curved surface 100D is formed at the corner corresponding to the connection between the step surface 100C and the inner surface 100B, and a curved chamfer 100E is formed at the corner corresponding to the connection between the step surface 100C and the inner surface 100A.

[0147] This makes it possible to suppress separation of the circulating flow of the refrigerant when it passes through the spaces 110A and 110B, and also to reduce pressure loss.

[0148] [11th example of compressor structure] Next, an eleventh example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0149] FIG. 16 is a diagram showing an eleventh example of the structure of the compressor 10. In FIG.

[0150] As shown in FIG. 16, the compressor 10 of this example differs from the first to tenth examples described above in that both the end face 230A of the shroud 230 and the step face 100C are formed in a curved shape, but may be the same as the sixth or ninth example described above in other respects.

[0151] In this example, the end surface 230A of the shroud 230 has a curved shape similar to that of the sixth example described above. Also, the stepped surface 100C of the casing 100 has a curved shape similar to that of the ninth example described above.

[0152] As a result, similar to the sixth and ninth examples described above, the compressor 10 can improve the effect of suppressing separation when the refrigerant circulation flow merges from the space 110B into the main flow and the effect of suppressing backflow at the ends of the blades 220 of the impeller 200.

[0153] In this example, the curved shapes of end face 230A of shroud 230 and step face 100C of casing 100 are defined so that the width of space 110B, which serves as a refrigerant passage, becomes smaller as it approaches the junction where the refrigerant circulating flow joins the mainstream. For example, the curved shapes of end face 230A of shroud 230 and step face 100C of casing 100 are defined so that, in a cross section including axis AX, width t2 of one end of space 110B, which serves as a refrigerant passage, on the inner surface 100A side is smaller than width t1 of the other end on the inner surface 100B side.

[0154] This increases the dynamic pressure of the circulating flow, facilitating the merging of the circulating flow with the main flow. In addition, increasing the dynamic pressure of the circulating flow can suppress backflow in the main flow.

[0155] [12th example of compressor structure] Next, a twelfth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0156] FIG. 17 is a diagram showing a twelfth example of the structure of the compressor 10. In FIG.

[0157] As shown in FIG. 17, the compressor 10 of this example differs from the first to eleventh examples described above in that the area extending from the intake pipe 120 to the inlet 200in of the impeller 200 is formed in a bell-mouth shape, but in other respects may be the same as the eleventh example described above.

[0158] In this example, the inner diameter of an inner surface 100A of the casing 100 corresponding to the suction pipe 120 is formed to decrease toward the inlet 200in of the impeller 200. For example, as shown in Fig. 17, the inner surface 100A of the casing 100 is formed in a bell-mouth shape.

[0159] This allows the flow of the refrigerant to be accelerated toward inlet 200in of impeller 200. Therefore, the circulating flow of refrigerant from space 110B can be merged into the acceleration region of the main flow of the refrigerant, thereby promoting mixing of the main flow of the refrigerant with the circulating flow of refrigerant that merges with the main flow from space 110B and suppressing loss due to interference between the main flow and the recirculating flow.

[0160] In this example, the diameter (inner diameter D2) of the inner surface of shroud 230 at inlet 200in of impeller 200 is set to be smaller than the diameter (inner diameter D1) of the connecting portion of casing 100 between inner surface 100A and stepped surface 100C.

[0161] This further accelerates the flow of the refrigerant between one end of inner surface 100A of casing 100 and inlet 200in of impeller 200. This further promotes mixing of the main flow of the refrigerant with the circulating flow of refrigerant that joins the main flow from space 110B, thereby improving the effect of suppressing loss due to interference between the main flow and the circulating flow.

[0162] [13th example of compressor structure] Next, a thirteenth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0163] Fig. 18 is a diagram showing a thirteenth example of the structure of the compressor 10. Specifically, Fig. 18 is a perspective view of the impeller 200 of the compressor 10 according to this example.

[0164] As shown in FIG. 18, the compressor 10 of this example differs from the first to twelfth examples described above in that the circumferentially extending slit-shaped through holes 235 are provided only in a portion of the circumferential direction, but in other respects may be the same as any one of the first to twelfth examples described above.

[0165] In this example, the multiple through holes 235 are arranged spaced apart in the circumferential direction. A connecting portion 236, which separates adjacent through holes 235 in the circumferential direction, connects a portion of the shroud 230 on the inlet 200in side with a portion of the shroud 230 on the outlet 200out side relative to the through holes 235.

[0166] For example, the impeller 200 may experience a blade vibration mode in which the leading edges of the blades 220 vibrate.

[0167] In contrast to this, in this example, the connecting portion 236 connects the portion of the shroud 230 on the inlet 200in side of the through hole 235, which corresponds to the leading edge of the tip of the blade 220, to the portion on the outlet 200out side. This makes it possible to suppress a decrease in the eigenvalue and improve strength against blade vibration.

[0168] [14th example of compressor structure] Next, a fourteenth example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0169] Fig. 19 is a diagram showing a fourteenth example of the structure of the compressor 10. Specifically, Fig. 19 is a perspective view of the impeller 200 of the compressor 10 according to this example.

[0170] As shown in FIG. 19, the compressor 10 according to this example may be different from the thirteenth example described above in terms of the structure of the connecting portion 236, but may be the same as the thirteenth example described above in other respects.

[0171] In this example, in some or all of the multiple through holes 235 provided in the circumferential direction, the openings 235B are arranged so as not to overlap the tips of the blades 220. In other words, the inner surfaces of the connecting portions 236 may be connected to the blades 220. For example, as shown in FIG. 19 , the connecting portions 236 are formed so as to overlap the blades 220 when viewed from the outside in the radial direction. This makes it possible to prevent the blades 220 from reducing the flow path cross-sectional area of ​​the through holes 235, and as a result, it is possible to prevent a decrease in the flow rate circulating to the inlet 200 in of the impeller 200 through the through holes 235. This makes it possible to both ensure the circulation of the air to the inlet 200 in of the impeller 200 through the through holes 235 and ensure strength against blade vibration.

[0172] [15th example of compressor structure] Next, with reference to FIG. 20, a diagram showing a fifteenth example of the structure of the compressor 10 according to this embodiment is shown.

[0173] FIG. 20 is a diagram showing a fifteenth example of the structure of the compressor 10. In FIG.

[0174] As shown in Figure 20, the compressor 10 of this example differs from the above-mentioned first to sixteenth examples in that a groove portion 113 is provided on the inner surface 100B of the casing 100 corresponding to the space 110A, but may be the same as the above-mentioned twelfth example in other respects.

[0175] The groove 113 is provided on the inner surface 100B of the casing 100 corresponding to the space 110A, i.e., on a portion of the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend in a direction perpendicular to the circumferential direction. In other words, the groove 113 is provided on a portion of the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend along a plane including the axial and radial directions (i.e., a plane including the axis AX). In this example, the groove 113 is provided on the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend in the axial direction. For example, there are a plurality of grooves 113, and the plurality of grooves 113 are arranged side by side in the circumferential direction over the entire circumferential direction, i.e., the entire circumference. The intervals at which the plurality of grooves 113 are arranged may be equal or unequal.

[0176] As a result, when the circulation flow of the refrigerant flowing into space 110A from through-hole 235 passes through groove portion 113, groove portion 113 restricts the flow in the circumferential direction, and can suppress the velocity component (forward swirl component) in the rotational direction (swirl direction) contained in the circulation flow. Therefore, it is possible to suppress a situation in which the forward swirl component contained in the circulation flow reduces the pressure increase of impeller 200 caused by the merging of the circulation flow with the mainstream.

[0177] [16th example of compressor structure] Next, a sixteenth example of the structure of the compressor 10 will be described with reference to FIG.

[0178] FIG. 21 is a diagram showing a sixteenth example of the structure of the compressor 10. In FIG.

[0179] As shown in FIG. 21, the compressor 10 of this example differs from the first to fifteenth examples described above in that a protrusion 114 is provided on the inner surface 100B of the casing 100 corresponding to the space 110A, but in other respects may be the same as the twelfth example described above.

[0180] The protrusions 114 are provided on the inner surface 100B of the casing 100 corresponding to the space 110A, i.e., on a portion of the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend in a direction perpendicular to the circumferential direction. In other words, the grooves 113 are provided on a portion of the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend along a plane including the axial and radial directions (i.e., a plane including the axis AX). In this example, the grooves 113 are provided on a portion of the inner surface 100B of the casing 100 closer to the inlet 200in of the impeller 200 than the seal member 240, so as to extend in the axial direction. For example, there are a plurality of protrusions 114, and the plurality of protrusions 114 are arranged side by side in the circumferential direction, i.e., over the entire circumference. The plurality of protrusions 114 may be arranged at equal intervals or at unequal intervals.

[0181] As a result, when the circulation flow of the refrigerant flowing into space 110A from through-hole 235 passes near protrusion 114, protrusion 114 restricts the flow in the circumferential direction, and can suppress the velocity component (forward swirl component) in the rotational direction (swirl direction) contained in the circulation flow. Therefore, it is possible to suppress a situation in which the forward swirl component contained in the circulation flow reduces the pressure increase of impeller 200 that occurs when the circulation flow merges with the mainstream.

[0182] [17th example of compressor structure] Next, a seventeenth example of the structure of the compressor 10 will be described with reference to FIG.

[0183] FIG. 22 is a diagram showing a seventeenth example of the structure of the compressor 10. In FIG.

[0184] As shown in FIG. 22, the compressor 10 of this example differs from the first to sixteenth examples described above in that a protrusion 115 is provided on the step surface 100C, but may be the same as the twelfth example described above in other respects.

[0185] The protrusions 115 are provided on the step surface 100C so as to extend in the radial direction. For example, there are a plurality of protrusions 115, and the plurality of protrusions 115 are arranged in a line in the circumferential direction over the entire circumferential direction, i.e., the entire circumference. The plurality of protrusions 115 may be arranged at equal intervals or at unequal intervals.

[0186] As a result, when the circulation flow of the refrigerant flowing from space 110A to space 110B passes near protrusions 115, protrusions 115 regulate the circumferential flow and can suppress the velocity component (forward swirl component) in the rotational direction (swirl direction) contained in the circulation flow. Therefore, it is possible to suppress a situation in which the forward swirl component contained in the circulation flow reduces the pressure increase of impeller 200 that occurs when the circulation flow joins the mainstream.

[0187] [18th example of compressor structure] Next, an 18th example of the structure of the compressor 10 will be described with reference to FIG.

[0188] FIG. 23 is a diagram illustrating an eighteenth example of the structure of the compressor 10. In FIG.

[0189] As shown in FIG. 23, the compressor 10 of this example differs from the first to seventeenth examples described above in that the through hole 235 is provided closer to the outlet 200out than the sealing member 240 in the shroud 230, but may be the same as the first example described above in other respects.

[0190] The seal member 240 is disposed between the end of the shroud 230 on the inlet 200 in side of the impeller 200 and the inner surface 100 B of the casing 100 .

[0191] As described above, the through hole 235 is provided on the outlet 200out side of one end of the shroud 230 on the inlet 200in side of the impeller 200, the other end on the outlet 200out side, and the seal member 240. For example, the inner opening 235A of the through hole 235 is provided on the outlet 200out side of the center between the one end on the inlet 200in side and the other end on the outlet 200out side of the inner surface of the shroud 230 in a cross section including the axis center AX. In this example, the through hole 235 is provided at a position in the shroud 230 relatively close to the outlet 200out of the impeller 200 in a cross section including the axis center AX, and is formed so as to linearly penetrate between the inner surface and the outer surface of the shroud 230.

[0192] 23, a portion of the refrigerant discharged from outlet 200out of impeller 200 can flow into through-hole 235 through space 110C between inner surface 100B of casing 100 and shroud 230, and circulate inside impeller 200. Therefore, compressor 10 can suppress wake, which is an accumulation region of low-energy refrigerant, that occurs near the outlet of impeller 200, by the circulation flow that joins the mainstream of impeller 200 through through-hole 235.

[0193] As in the first example described above, through hole 235 is provided so as to incline toward inlet 200in of impeller 200 with respect to a direction perpendicular to the inner surface of shroud 230. In a cross section including axis AX, through hole 235 has center 235Bc of opening 235B positioned closer to inlet 200in of impeller 200 than center 235Ac of opening 235A. This makes it possible to suppress separation that occurs at the outer edge of opening 235A of through hole 235 when refrigerant flows into the main stream of impeller 200 from through hole 235. Compressor 10 can suppress loss when the sub-downstream flow from through hole 235 joins the main stream of impeller 200, thereby further improving the effect of through hole 235.

[0194] The degree of inclination of through hole 235 (for example, inclination angle θ1) is determined taking into consideration, for example, the viewpoint of suppressing separation occurring at the outer edge of opening 235A of through hole 235 and the viewpoint of ease of flow of the circulating flow of refrigerant in space 110C into through hole 235. This is because the greater the degree of inclination of through hole 235, the less likely separation occurs at the outer edge of opening 235A of through hole 235, while the smaller the degree of inclination of through hole 235, the more likely the circulating flow of refrigerant in space 110C flows into through hole 235.

[0195] For example, by prioritizing the ease with which the refrigerant from space 110C flows into through hole 235, inclination angle θ1 of through hole 235 is set to a range of 10 degrees or greater. Alternatively, by prioritizing the prevention of separation occurring at the outer edge of opening 235A of through hole 235, inclination angle θ1 of through hole 235 may be set to a range of 30 degrees or greater. Alternatively, by achieving a balance between the ease with which the refrigerant from space 110C flows into through hole 235 and the prevention of separation occurring at the outer edge of opening 235A of through hole 235, inclination angle θ1 of through hole 235 may be set to a range of 20 degrees or greater.

[0196] [19th example of compressor structure] Next, a 19th example of the structure of the compressor 10 according to this embodiment will be described with reference to FIG.

[0197] FIG. 24 is a diagram illustrating a 19th example of the structure of the compressor 10. In FIG.

[0198] As shown in Figure 24, the compressor 10 of this example differs from the above-mentioned first to eighteenth examples in that the seal member 240 is provided on both the inlet 200in side and the outlet 200out side of the impeller 200 in the shroud 230, but may be the same as the above-mentioned twelfth example in other respects.

[0199] As a result, the compressor 10 can achieve high pressure, a wide range, and suppress mild surge of the impeller 200 in the low flow rate region of the compressor 10 through the action of the through hole 235 on the inlet 200in side of the impeller 200, while suppressing wake of the impeller 200 through the action of the through hole 235 on the outlet 200out side of the impeller 200.

[0200] In this example, similar to the first example described above, the through-hole 235 on the inlet 200in side of the impeller 200 is provided so as to incline toward the inlet 200in side of the impeller 200 with respect to the direction perpendicular to the inner surface of the shroud 230.

[0201] This allows the compressor 10 to suppress separation at the outer edge of the opening 235B when the refrigerant flows into the space 110B through the through-hole 235, thereby increasing the flow rate circulating to the inlet 200in of the impeller 200. Therefore, the compressor 10 can further improve the mild surge suppression effect due to the action of the through-hole 235.

[0202] In this example, similar to the above-described 18th example, the through-hole 235 on the outlet 200out side of the impeller 200 is provided so as to incline toward the inlet 200in side of the impeller 200 with respect to the direction perpendicular to the inner surface of the shroud 230.

[0203] As a result, compressor 10 can suppress separation at the outer edge of opening 235A when the refrigerant flows from through hole 235 to join the main refrigerant flow, and compressor 10 can suppress loss when the sub-downstream flow flows from through hole 235 to join the main refrigerant flow of impeller 200. Therefore, compressor 10 can further improve the wake suppression effect achieved by the action of through hole 235.

[0204] [Another example of compressor structure] Next, another example of the structure of the compressor 10 will be described.

[0205] The above-described first to nineteenth examples of the structure of the compressor 10 may be modified or changed as appropriate. Hereinafter, for convenience, examples in which modifications or changes have been made will be referred to as "modified examples."

[0206] <First Modification> In the fourth example of the structure of the compressor 10 described above (FIG. 9), the chamfers 235C and 235D may be linear chamfers (for example, C-chamfers).

[0207] <Second Modification> In the fourth example (FIG. 9) and the first modified example of the structure of the compressor 10 described above, either one of the chamfers 235C and 235D may be omitted.

[0208] <Third Modification> In the third example (FIG. 8) of the structure of the compressor 10 described above, the chamfer 235C or the chamfer 235D of the fourth example (FIG. 9) or the first modified example described above may be provided on the outer edge of at least one of the openings 235A, 235B. <Fourth Modification> In the fifth example (FIG. 10) to the twelfth example (FIG. 17) and the fifteenth example (FIG. 20) to the seventeenth example (FIG. 22) of the structure of the compressor 10 described above, the through hole 235 may be replaced with the through hole 235 in the form of the fourth example (FIG. 9) described above.

[0209] <Fifth Modification> In the eighteenth and nineteenth examples of the structure of the compressor 10 described above, the through hole 235 provided on the outlet 200out side of the impeller 200 relative to the seal member 240 may be formed in a curved shape in a cross section including the axis AX. In this case, unlike the through hole 235 in the third example (FIG. 8) described above, the through hole 235 is formed in a curved shape such that its center line inclines toward the inlet 200in side of the impeller 200 as it moves from the opening 235B to the opening 235A.

[0210] <Sixth Modification> The chamfers 230B and 230C in the seventh example (FIG. 12) of the structure of the compressor 10 described above may be linear chamfers (for example, C-chamfers).

[0211] <Seventh Modification> In the seventh example (FIG. 12) and the sixth modified example of the structure of the compressor 10 described above, either one of the chamfers 230B and 230C may be omitted.

[0212] <Eighth Modification> In the sixth example (FIG. 11) of the structure of the compressor 10 described above, the chamfers 230B, 230C of the seventh example (FIG. 12) or the fifth modified example described above may be provided at the connection portions (corners) between the end face 230A of the shroud 230 and each of the outer and inner surfaces.

[0213] <Ninth Variation> In the tenth example of the structure of compressor 10 (FIG. 15), a corner corresponding to the connection between step surface 100C and inner surface 100B may be provided with a flat surface arranged to fill the corner, instead of curved surface 100D. Also, in the tenth example of the structure of compressor 10, chamfer 100E of the corner corresponding to the connection between step surface 100C and inner surface 100A may be a flat chamfer (for example, a C-chamfer).

[0214] <Tenth Variation> In the tenth example (FIG. 15) and the ninth variant of the structure of the compressor 10 described above, either the curved surface 100D or the flat surface provided at the corner corresponding to the connection between the step surface 100C and the inner surface 100B, or the chamfer 100E may be omitted.

[0215] <Eleventh Variation> In the first example (Figure 4) to the seventh example (Figure 12), the ninth example (Figure 14), the eleventh example (Figure 16), the twelfth example (Figure 17), the fifteenth example (Figure 20) to the seventeenth example (Figure 22), and the nineteenth example (Figure 24) of the structure of the compressor 10 described above, the corner portion corresponding to the connection between the step surface 100C and the inner surface 100B may be provided with the curved surface 100D of the tenth example (Figure 15) described above or a flat surface of the ninth modified example described above. Similarly, in the first example (Figure 4) to the seventh example (Figure 12), the ninth example (Figure 14), the eleventh example (Figure 16), the twelfth example (Figure 17), the fifteenth example (Figure 20) to the seventeenth example (Figure 22), and the nineteenth example (Figure 24) of the structure of the compressor 10 described above, the corner corresponding to the connection between the step surface 100C and the inner surface 100A may be provided with the chamfer 100E of the tenth example (Figure 15) described above or the ninth modified example described above.

[0216] <Twelfth Modification> In the fifteenth example ( FIG. 20 ) of the structure of the compressor 10 described above and its various modified examples, a relatively rough surface (rough surface) may be employed on the inner surface 100B of the casing 100 instead of or in addition to the groove portion 113. For example, the inner surface 100B of the casing 100 is rougher than the inner and outer surfaces of the shroud 230. The roughness of the inner surface 100B of the casing 100 can suppress a velocity component (forward swirling component) in the rotational direction (swirl direction) included in the circulating flow of the refrigerant flowing from the through-hole 235 into the space 110A.

[0217] <13th Variation> In the sixteenth example ( FIG. 21 ) of the structure of the compressor 10 described above and its various modified examples, a relatively rough surface may be adopted for the inner surface 100B of the casing 100 instead of or in addition to the protrusions 114. For example, the inner surface 100B of the casing 100 is rougher than the inner and outer surfaces of the shroud 230. The roughness of the inner surface 100B of the casing 100 can suppress the rotational (swirl direction) velocity component (forward swirl component) contained in the circulating flow of the refrigerant flowing from the through-holes 235 into the space 110A.

[0218] <14th Modification> Furthermore, in the first example (FIG. 4) to the nineteenth example (FIG. 24) of the structure of the compressor 10 and the first to eleventh modified examples described above, the through holes 235 may not be slit-shaped with a relatively long dimension in the circumferential direction, but may be shaped with a relatively short dimension in the circumferential direction (for example, a round hole, an oval hole, a rectangular hole, or the like). In this case, there may be a plurality of through holes 235, and the plurality of through holes 235 may be arranged side by side at equal or unequal intervals in the circumferential direction. In this case, the openings 235B of some or all of the plurality of through holes 235 provided in the circumferential direction may be arranged so as not to overlap with the tips of the blades 220. This makes it possible to prevent the blades 220 from reducing the flow path cross-sectional area of ​​the through holes 235. As a result, it is possible to prevent a reduction in the flow rate circulating through the through holes 235 to the inlet 200in of the impeller 200 from decreasing.

[0219] [Effect] Next, the operation of the centrifugal compressor and the refrigeration system according to this embodiment will be described.

[0220] In a first aspect of this embodiment, a centrifugal compressor includes an impeller and a casing that houses the impeller. The centrifugal compressor is, for example, the compressor 10 described above. The impeller is, for example, the impeller 200 described above. The casing is, for example, the casing 100 described above. Specifically, the impeller has a hub having a meridian plane, a plurality of blades provided on the meridian plane, and a shroud provided at the tips of the plurality of blades so as to cover the meridian plane. The meridian plane is, for example, the meridian plane 211 described above. The hub is, for example, the hub 210 described above. The blade is, for example, the blade 220 described above. The shroud is, for example, the shroud 230 described above. More specifically, the shroud is provided with a first passage that penetrates between an inner surface facing the meridian plane and an outer surface facing the inner surface of the casing, and has a first opening on the outer surface side and a second opening on the inner surface side. The first opening is, for example, the above-mentioned opening 235B. The second opening is, for example, the above-mentioned opening 235A. The first passage is, for example, the above-mentioned through hole 235. The first passage is inclined so that the center of the first opening is located closer to the inlet of the impeller than the center of the second opening in a cross section including the axis of the rotary shaft of the impeller. The rotary shaft is, for example, the above-mentioned rotary shaft 250. The axis is, for example, the above-mentioned axis center AX. The center of the first opening is, for example, the above-mentioned center 235Bc. The center of the second opening is, for example, the above-mentioned center 235Ac. The inlet is, for example, the above-mentioned inlet 200in.

[0221] As a result, the centrifugal compressor can, for example, allow a portion of the fluid passing through the impeller to flow into the gap between the shroud and the casing through the first passage, and circulate the fluid to the impeller inlet through the gap. Therefore, while the peak efficiency of the impeller is slightly reduced, the work coefficient (i.e., impeller work) on the high-pressure / low-flow side is increased, thereby suppressing the upward-sloping pressure-flow characteristic. As a result, the centrifugal compressor can achieve an expanded operating range (so-called wide-range). Furthermore, the centrifugal compressor can suppress mild surges caused by the upward-sloping pressure-flow characteristic and the generation of humming noise associated with mild surges. Furthermore, the centrifugal compressor can circulate the fluid from the impeller outlet to the impeller through, for example, the gap between the shroud and the casing and the first passage. Therefore, the centrifugal compressor can suppress wakes near the impeller outlet. Therefore, the centrifugal compressor can improve the performance of a closed impeller.

[0222] In a second aspect of this embodiment, based on the first aspect described above, the plurality of blades includes a first blade and a second blade adjacent to and ahead of the first blade in the direction of rotation of the impeller. The first blade is, for example, blade 220a described above. The rotation direction is, for example, rotation direction RT described above. The second blade is, for example, blade 220b described above. Specifically, on a line segment that starts at one end of the inlet side of the first blade and forms a shortest distance between the first blade and the second blade, a first imaginary point is defined as a point that is 40 percent of the length of the line segment from the end of the first blade side, and a second imaginary point is defined as a point that is 60 percent of the length of the line segment from the end of the first blade side. The second opening may be located between the first imaginary line that passes through the first imaginary point and extends in the circumferential direction, and the second imaginary line that passes through the second imaginary point and extends in the circumferential direction. The inlet-side end of the first blade is, for example, the above-mentioned imaginary point Ps. The line segment is, for example, the above-mentioned throat 225. The first imaginary point is, for example, the above-mentioned imaginary point P1. The second imaginary point is, for example, the above-mentioned imaginary point P2. The first imaginary line is, for example, the above-mentioned imaginary line VL1. The second imaginary line is, for example, the above-mentioned imaginary line VL2.

[0223] This allows the centrifugal compressor to optimize the flow rate circulated to the inlet of the impeller through the first passage, and appropriately suppress the upward slope of the pressure-flow rate characteristic.

[0224] In a third aspect of this embodiment, based on the first or second aspect described above, a second passage may be formed by axially opposing the inlet end of the shroud and the casing. The second passage may be, for example, the space 110B described above. The second passage may be inclined, in a cross section including the axis, from the outer surface side to the inner surface side of the shroud toward the outlet side of the impeller with respect to a direction perpendicular to the inner surface of the shroud. The outlet may be, for example, the outlet 200out described above.

[0225] As a result, the centrifugal compressor can return the circulating flow that flows into the gap between the shroud and the casing through the first passage to the mainstream of the fluid at the inlet of the impeller through the second passage. Also, because the second passage is inclined toward the outlet side of the impeller, the centrifugal compressor can suppress separation of the circulating flow and reduce pressure loss when the circulating flow joins the mainstream. Also, because the second passage is inclined toward the outlet side of the impeller, the centrifugal compressor can cause the circulating flow to enter the mainstream with a component oriented in the mainstream direction, thereby suppressing backflow that occurs at the blade ends of the impeller.

[0226] In addition, in a fourth aspect of this embodiment, based on the above-described third aspect, the inlet side end of the shroud may be chamfered.

[0227] This makes it possible to suppress separation occurring in the circulating flow and also to reduce the amount of separation that occurs It is possible to suppress pressure loss due to a reduction in the effective cross-sectional area of ​​the flow path.

[0228] In addition, in a fifth aspect of this embodiment, based on the third or fourth aspect described above, the axial width of the second passage may narrow from the outer surface side toward the inner surface side of the shroud.

[0229] As a result, in the centrifugal compressor, the second passage is formed in a nozzle shape toward the main flow at the inlet of the impeller, which makes it possible to increase the dynamic pressure of the recirculation flow when it joins the main flow, thereby enhancing the effect of suppressing the backflow phenomenon that occurs at the blade ends of the impeller.

[0230] In addition, in a sixth aspect of this embodiment, based on any one of the third to fifth aspects described above, the inner diameter of the inlet end of the shroud may be smaller than the inner diameter of the casing at a location axially opposite the inlet end of the shroud. The inner diameter of the inlet end of the shroud is, for example, the inner diameter D2 described above. The inner diameter of the casing at a location axially opposite the inlet end of the shroud is, for example, the inner diameter D1 described above.

[0231] As a result, the centrifugal compressor has a bell-mouth-shaped flow passage formed near the inlet of the impeller, and can accelerate the main flow at the inlet of the impeller. Therefore, the centrifugal compressor can merge the circulating flow from the second passage into the acceleration region of the main flow, thereby promoting mixing of the main flow and the circulating flow and suppressing loss caused by interference between the main flow and the circulating flow.

[0232] In addition, in a seventh aspect of this embodiment, assuming any one of the first to sixth aspects described above, the tip portions of the plurality of blades on the shroud side may not overlap with the second opening.

[0233] This allows the centrifugal compressor to increase the flow path cross-sectional area of ​​the first passage and increase the flow path for the circulating flow.

[0234] In an eighth aspect of the present embodiment, based on any one of the first to seventh aspects, a seal may be provided between the outer surface of the shroud and the casing. The seal is, for example, the seal member 240 described above.

[0235] This allows the centrifugal compressor to guide, for example, the fluid that flows into the space between the shroud and the casing through the first passage to the inlet side of the impeller. Also, the centrifugal compressor can guide the fluid that flows into the space between the shroud and the casing from the outlet of the impeller to the first passage.

[0236] Furthermore, for example, if the opening (first opening) on ​​the outer surface side of the shroud in the first passage is positioned closer to the outlet of the impeller in the axial direction, it may be necessary to place the seal at a location where the rate of expansion of the outer diameter of the shroud along the axial direction is relatively large. In this case, the gap between the seal and the outer surface of the shroud increases, which may increase the amount of leakage of fluid flowing into the gap between the shroud and the casing to the opposite side of the seal, potentially reducing the efficiency of the centrifugal compressor. Furthermore, reducing the gap between the seal and the outer surface of the shroud requires modifying the shape of the outer surface of the shroud, which may result in increased inertia of the impeller and increased costs.

[0237] In contrast, in this aspect, as described above, because the first passage is inclined toward the inlet of the impeller, the opening (first opening) on ​​the outer surface of the first passage can be positioned closer to the inlet of the impeller in the axial direction. Therefore, the seal portion can be positioned closer to the inlet of the impeller in the axial direction, which makes it less likely that the seal portion will be positioned in a location where the axial expansion rate of the outer diameter of the shroud is relatively large. Therefore, the centrifugal compressor can suppress problems such as a decrease in efficiency, an increase in impeller inertia, and an increase in cost, which are caused by an increase in the amount of leakage of fluid flowing into the gap between the shroud and the casing to the opposite side of the seal portion.

[0238] In addition, in a ninth aspect of this embodiment, based on the above-described eighth aspect, the first opening may be provided closer to the inlet than the seal portion.

[0239] This allows the centrifugal compressor to circulate the fluid that flows into the space between the shroud and the casing through the first passage to the inlet side of the impeller, thereby suppressing the upward slope of the pressure-flow characteristics of the centrifugal compressor, thereby suppressing mild surges and the occurrence of humming noise.

[0240] In a tenth aspect of the present embodiment, based on any one of the first to ninth aspects, the first passage may be provided so as to extend in a circumferential direction. Alternatively, the first passage may be provided only in a part of the entire circumferential direction.

[0241] This allows the centrifugal compressor to increase the flow path cross-sectional area of ​​the first passage. Also, in the centrifugal compressor, the first passage is provided only in a part of the entire circumferential direction, which prevents the shroud from being divided by the first passage and reduces the eigenvalue, thereby ensuring appropriate blade vibration strength of the impeller.

[0242] In an eleventh aspect of this embodiment, based on any one of the first to tenth aspects described above, a second passage may be formed by the inlet end of the shroud and the casing being opposed in the axial direction along the axis. A third passage communicating with the first passage and the second passage may be formed between the outer surface of the shroud and the inner surface of the casing. The third passage may be, for example, space 110A. In the second passage or the third passage, the inner surface of the casing may have a protrusion extending in a direction perpendicular to the circumferential direction, a groove extending in a direction perpendicular to the circumferential direction, or a roughened surface rougher than the inner surface of the shroud. The inner surface of the casing may be, for example, inner surface 100B described above. The protrusion may be, for example, protrusions 114 and 115 described above. The groove may be, for example, groove portion 113 described above.

[0243] This allows the centrifugal compressor to reduce the swirl component (i.e., the circumferential velocity component) of the flow of fluid that flows into the gap between the casing and the shroud through the first passage, thereby preventing the effect of the swirl component contained in the circulating flow from being reduced in increasing the pressure of the impeller due to the circulating flow.

[0244] In addition, in a twelfth aspect according to the present embodiment, based on the above-described eighth aspect, the first opening may be provided closer to the outlet side of the impeller than the seal portion.

[0245] As a result, the centrifugal compressor directs the fluid from the outlet side of the impeller through the space between the casing and the shroud. By allowing the fluid to flow into the gap between the impeller and then join the main flow of the impeller through the first passage, a portion of the fluid at the impeller outlet can be circulated, which allows the centrifugal compressor to suppress wakes near the impeller outlet.

[0246] In a thirteenth aspect according to the present embodiment, based on any one of the first to twelfth aspects described above, the centrifugal compressor may include a first compression section that compresses an inflowing fluid, and a second compression section that receives the inflowing fluid discharged from the first compression section and compresses the fluid. The first compression section may include another impeller having another shroud that is not provided with the first passage, and the second compression section may include the impeller having the shroud that is provided with the first passage.

[0247] As a result, by providing the first passage only in the compression section on the rear stage where mild surge is likely to occur, the centrifugal compressor can achieve a balance between efficiency and suppression of mild surge due to high pressure and wide range in the low flow rate region.

[0248] In addition, in a fourteenth aspect of the present embodiment, the refrigeration device may include the centrifugal compressor of any one of the first to thirteenth aspects described above. The refrigeration device is, for example, the refrigeration device 1 described above.

[0249] This makes it possible to improve the performance of the closed impeller of the centrifugal compressor installed in the refrigeration device.

[0250] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Explanation of symbols]

[0251] 1 Refrigeration equipment 10 Compressor 20 Heat exchanger 30 Expansion mechanism 40 Heat exchanger 100 casing 100A inner surface 100B inner surface 100C step surface 100D curved surface 110 Impeller chamber 110A space 110B Space 110C space 111 Diffuser 113 Groove 114 Protrusion 115 Protrusion 120 Suction pipe 130 Discharge pipe 140 Electric motor room 200 impeller 200in entrance 200out exit 210 Hub 211 Meridian 220 blade 220a blade 220b blade 225 Throat 230 Shroud 230A end face 235 Through hole 235A aperture 235Ac center 235B opening 235Bc center 236 Connecting part 240 Sealing material 250 rotation axis 260 Color 300 electric motor 310 Rotor 320 Stator 400 Radial Magnetic Bearing 500 Thrust Magnetic Bearing 510 Electromagnet 600 Touchdown Bearing AX axis center D1 Inner diameter D2 inner diameter P0 center P1 Virtual point P2 virtual point Pe virtual point Ps virtual point t1 width t2 width VL0 Virtual Line VL1 Virtual Line VL2 Virtual Line θ1 Tilt angle θ2 Tilt angle θ3 Tilt angle θ4 Tilt angle

Claims

1. An impeller (200), a casing (100) that houses the impeller (200); The impeller (200) a hub (210) having a meridian face (211); A plurality of blades (220) provided on the meridian plane (211); a shroud (230) provided at the tip of the plurality of blades (220) so as to cover the meridian plane (211); The shroud (230) is provided with a first passage (235) that penetrates between an inner surface facing the meridian plane (211) and an outer surface facing the inner surface of the casing (100), and has a first opening (235B) on the outer surface side and a second opening (235A) on the inner surface side; The first passage (235) is inclined so that, in a cross section including an axis (AX) of a rotation shaft (250) of the impeller (200), a center (235Bc) of the first opening (235B) is located closer to an inlet (200 in) of the impeller (200) than a center (235Ac) of the second opening (235A). Centrifugal compressor.

2. The plurality of blades (220) a first blade (220a); The impeller (200) has a second blade (220b) adjacent to the first blade (220a) on the front side in the rotation direction (RT) of the impeller (200), In a line segment (225) that starts from one end (Ps) of the first blade (220a) on the inlet (200 in) side and forms the shortest distance between the first blade (220a) and the second blade (220b), a point that is 40 percent of the length of the line segment from the end on the first blade (220a) side is defined as a first imaginary point (P1), and a point that is 60 percent of the length of the line segment (225) from the end on the first blade (220a) side is defined as a second imaginary point (P2). The second opening (235A) is located between a first imaginary line (VL1) that passes through the first imaginary point (P1) and extends in the circumferential direction, and a second imaginary line (VL2) that passes through the second imaginary point (P2) and extends in the circumferential direction. The centrifugal compressor according to claim 1 .

3. The end of the shroud (230) on the inlet (200 in) side and the casing (100) face each other in the axial direction, thereby forming a second passage (110B), In a cross section including the axis (AX), the second passage (110B) is inclined from the outer surface side to the inner surface side of the shroud (230) toward the outlet (200out) side of the impeller (200) with respect to a direction perpendicular to the inner surface of the shroud (230). The centrifugal compressor according to claim 1 or 2.

4. The inlet (200 in) end of the shroud (230) is chamfered. The centrifugal compressor according to claim 3 .

5. The axial width of the second passage (110B) narrows from the outer surface side to the inner surface side of the shroud (230). The centrifugal compressor according to claim 3 .

6. an inner diameter (D2) of the shroud (230) at the end on the inlet (200 in) side is smaller than an inner diameter (D1) of the casing (100) at a location axially opposite the end on the inlet (200 in) side of the shroud (230); The centrifugal compressor according to claim 3 .

7. The plurality of blades (220) have their tips on the shroud (230) side not overlapping with the second opening (235A). The centrifugal compressor according to claim 1 or 2.

8. A seal portion (240) is provided between the outer surface of the shroud (230) and the casing (100). The centrifugal compressor according to claim 1 or 2.

9. The first opening (235B) is provided closer to the inlet (200 in) than the seal portion (240). The centrifugal compressor according to claim 8.

10. The first passage (235) is provided to extend in a circumferential direction. The centrifugal compressor according to claim 1 or 2.

11. A second passage (110B) is formed by an end portion of the shroud (230) on the inlet (200 in) side and the casing (100) facing each other in an axial direction along the axis (AX), a third passage (110A) communicating with the first passage (235) and the second passage (110B) is formed between an outer surface of the shroud (230) and an inner surface of the casing (100); In the second passage (110B) or the third passage (110A), the inner surface of the casing (100) has protrusions (114, 115) extending in a direction perpendicular to the circumferential direction, grooves (113) extending in a direction perpendicular to the circumferential direction, or a rough surface that is rougher than the inner surface of the shroud (230). The centrifugal compressor according to claim 1 or 2.

12. The first opening (235B) is provided closer to the outlet (200out) of the impeller (200) than the seal portion (240). The centrifugal compressor according to claim 8.

13. a first compression section that compresses an incoming fluid; a second compression section into which the fluid discharged from the first compression section flows and compresses the fluid, the first compression section includes another impeller having another shroud in which the first passage (235) is not provided; the second compression section includes the impeller (200) having the shroud (230) in which the first passage (235) is provided; The centrifugal compressor according to claim 1 or 2.

14. The centrifugal compressor (10) according to claim 1 or 2, Refrigeration equipment.

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