BACKGROUND

[0001] Embodiments of this disclosure relate generally to a centrifugal compressors and, more particularly, to an electric motor for driving a centrifugal compressor.

[0002] In a compression system, a motor is provided for driving a compressor mechanism. The size and type of the motor required is dependent upon several factors, including the capacity of the compressor and the operating environment of the compression system. Centrifugal compressors are often used in refrigeration systems. Centrifugal compressors are usually driven by electric motors that are commonly included in a housing that encases both the motor and the compressor. Such motors typically have an overhung arrangement where an unsupported end of the rotor is easily accessible within the housing. The overhung configuration not only results in asymmetric and increased loads on the motor shaft but also increases the size, complexity, and manufacturing cost of the compressor.

SUMMARY

[0003] According to a first embodiment, an impeller of a centrifugal compressor comprising includes an impeller body rotatable about an impeller axis and a motor operable to drive said impeller about said impeller axis. The motor includes a stator assembly and a rotor assembly. The rotor assembly being associated with said impeller body.

[0004] In addition to one or more of the features described above, or as an alternative, in further embodiments said rotor assembly further comprises at least one interactive component configured to interact with a magnetic field generated by said stator assembly to drive said impeller about said impeller axis.

[0005] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is not coupled to an electrical source separate from said stator assembly.

[0006] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is integrally formed with said impeller body.

[0007] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is removably coupled to said impeller body. [0008] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is coupled to an exterior surface of said impeller body.

[0009] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is at least partially embedded within said impeller body.

[0010] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component comprises a plurality of interactive components positioned about a periphery of said impeller body.

[0011] In addition to one or more of the features described above, or as an alternative, in further embodiments said stator assembly includes at least one electrical component operable to generate a magnetic field when power is applied thereto.

[0012] In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a shroud arranged adjacent said impeller body, said stator assembly being associated with said shroud.

[0013] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one electrical component is positioned in vertical alignment with said at least one interactive component.

[0014] In addition to one or more of the features described above, or as an alternative, in further embodiments a clearance between said at least one electrical component and said at least one interactive component is uniform about said impeller body.

[0015] In addition to one or more of the features described above, or as an alternative, in further embodiments a clearance between said at least one electrical component and said at least one interactive component varies about said impeller body.

[0016] According to another embodiment, a centrifugal compressor includes a housing having a suction port and a discharge port. An impeller is rotatable relative to said housing to draw a fluid in through said suction port and discharge said fluid through said discharge port. A motor is operably coupled to said impeller to rotate said impeller about an impeller axis. The motor includes a stator assembly and a rotor assembly. The rotor assembly being associated with said impeller.

[0017] In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a shroud arranged adjacent said impeller, said stator assembly being associated with said shroud. [0018] In addition to one or more of the features described above, or as an alternative, in further embodiments said rotor assembly further comprises at least one interactive component configured to interact with a magnetic field generated by said stator assembly to drive said impeller about said impeller axis.

[0019] In addition to one or more of the features described above, or as an alternative, in further embodiments said at least one interactive component is not coupled to an electrical source separate from said stator assembly.

[0020] According to another embodiment, a chiller refrigeration system includes a condenser, evaporator, and compressor arranged in fluid communication to form a refrigeration circuit. The compressor is a centrifugal compressor including a housing having a suction port and a discharge port. An impeller is rotatable relative to said housing to draw a fluid in through said suction port and discharge said fluid through said discharge port. A motor is operably coupled to said impeller to rotate said impeller about an impeller axis. The motor includes a stator assembly and a rotor assembly, said rotor assembly being associated with said impeller.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The subject matter, which is regarded as the present disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

[0022] FIG. 1 is schematic diagram of an example of a chiller system;

[0023] FIG. 2 is a cross-sectional schematic diagram of a centrifugal compressor; and

[0024] FIG. 3 is a cross-sectional schematic diagram of a centrifugal compressor according to an embodiment.

[0025] The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION

[0026] Referring now to FIG. 1, an example of a chiller refrigeration system 20 is illustrated. As shown, the chiller refrigeration system 20 includes a compressor 22, a condenser 24, and a cooler or evaporator 26 fluidly coupled to form a circuit. A first conduit 28 extends from adjacent the outlet 30 of the cooler 26 to the inlet 32 of the compressor 22. The outlet 34 of the compressor is coupled by a conduit 36 to an inlet 38 of the condenser 24. In one embodiment, the condenser 24 includes a first chamber 40 and a second chamber 42, the second chamber 42 being accessible only from the interior of the first chamber 40. A float valve 44 within the second chamber 42 is connected to an inlet 46 of the cooler 26 by another conduit 48. Depending on the size of the chiller system 20, the compressor 22 may include a rotary, screw, or reciprocating compressor for small systems, or a screw compressor or a centrifugal compressor for larger systems.

[0027] The refrigeration cycle of the chiller refrigeration system 20 may be described as follows. The compressor 22 receives a refrigerant vapor from the e aporator/cooler 26 and compresses it to a higher temperature and pressure, with the relatively hot vapor then passing into the first chamber 40 of the condenser 24 where it is cooled and condensed to a liquid state by a heat exchange relationship with a cooling medium, such as water or air for example. Because the second chamber 42 has a lower pressure than the first chamber 40, a portion of the liquid refrigerant flashes to vapor, thereby cooling the remaining liquid. The refrigerant vapor within the second chamber 42 is re-condensed by the cool heat exchange medium. The refrigerant liquid then drains into the second chamber 42 located between the first chamber 40 and the cooler 26. The float valve 44 forms a seal to prevent vapor from the second chamber 42 from entering the cooler 26. As the liquid refrigerant passes through the float valve 44, the refrigerant is expanded to a low temperature two phase liquid/vapor state as it passed into the cooler 26. The cooler 26 is a heat exchanger which allows heat energy to migrate from a heat exchange medium, such as water for example, to the refrigerant gas. When the gas returns to the compressor 22, the refrigerant is at both the temperature and the pressure at which the refrigeration cycle began. The chiller refrigeration system 20 and refrigeration cycle illustrated and described herein are intended as an example only.

[0028] An example of a typical centrifugal compressor, such as compressor 22 of the chiller system 20, is shown in more detail in FIG. 2. The compressor 22 includes a housing 50 containing an electric motor 52 and an impeller 54 drivable by the electric motor 52. The motor 52 is arranged within a motor compartment 56 of the housing 50. The motor stator 58 is fixedly mounted to the housing 50 within the compartment 56, and the motor rotor 60 is arranged at least partially within the stator 58 and is rotatable about a rotor axis R. In the illustrated, non- limiting embodiment, the rotor 60 is coupled to a shaft 62 mounted to the housing 50 via one or more mechanical and/or electromagnetic bearings (not shown).

[0029] As shown, the impeller 54 is coupled to an impeller shaft 64. The impeller shaft 64 is mounted to the housing 50 via one or more mechanical and/or electromagnetic bearings (not shown) and is rotatable about an impeller axis I. The impeller axis I is offset from the motor axis R thereby requiring a transmission assembly 66 to operabiy couple the motor shaft 62 and the impeller shaft 64. However, embodiments of the compressor 22 that do not include a transmission assembly 66 because the impeller 54 is directly mounted to the motor shaft 62 are also within the scope of the disclosure. The impeller 54 is operable to draw fluid in through the suction port or inlet 32, compress the fluid, and discharge the fluid from the discharge port or outlet 34 (shown in FIG. 1). After the refrigerant vapor is accelerated to a high velocity by the impeller 54, a diffuser 68 (FIG. 1) may be used to decelerate the refrigerant to a low velocity while converting kinetic energy to pressure energy, and a discharge plenum (not shown) in the form of a volute collects the discharge vapor for subsequent flow to a condenser 24.

[0030] Positioned near the inlet 32 of the compressor 30 is an inlet guide vane assembly 70. Because a fluid flowing from the cooler 26 to the compressor 22 must first pass through the inlet guide vane assembly 70 before entering the impeller 54, the inlet guide vane assembly 70 may be used to control the fluid flow into the compressor 22. The inlet guide vanes of the inlet guide vane assembly 70 are generally triangular in plan form and are mounted for synchronized rotation about an associated vane axis between a maximally closed position and a maximally open condition.

[0031] To reduce the overall size of the compressor 22, the electric motor 52 may be integrated with the impeller 54. With reference now to FIG. 3, the electric motor 52 operable to drive rotation of the impeller 54 about the impeller axis I includes a stator assembly 72 coupled to a shroud 74 and a rotor assembly 76 associated with the impeller 54 and configured to rotate about the impeller axis I. The shroud 74 is a composite or laminate structure having one or more electrical components 78 mounted therein. The electrical components 78 may be selected from electromagnets, permanent magnets and windings such that when power is supplied to the electrical components 78 mounted to the shroud 74, a magnetic field is generated. The total number of electrical components 78 mounted to the shroud 74 may vary based on the desired performance of the compressor 22. The electrical components 78 are arranged generally circumferentially about the shroud 74 and are located at a position in overlapping arrangement with a portion of the adjacent impeller 54.

[0032] The rotor assembly 76 of the motor 52 includes one or more interactive components 80, such as permanent magnets or windings or laminations for example, mounted to the impeller 54 and configured to interact with the magnetic field created by the stator assembly 72. As shown, the interactive components 80 are arranged about the impeller 54 such that the one or more interactive components 80 are vertically aligned with the at least one electrical component 78 of the stator assembly 72. In an embodiment, the interactive components 80 are integrally formed with the impeller 54, such as via an additive manufacturing process for example. Alternatively, the interactive components 80 may be removably mounted to the impeller 54. For example, the interactive components 80 may be partially or fully embedded with the impeller 54, such as within one or more complementary openings (not shown) formed therein. The interactive components 80 are generally positioned circumferentially about the exterior surface of the impeller 54, concentric with the impeller shaft 64. The interactive components 80 may, but need not be, equidistantly spaced about the impeller 54. In other embodiments, the interactive components 80 may be placed at a position between circumferential and axial.

[0033] The interaction between the interactive components 80 mounted to the impeller 54 and the magnetic field generated when the electric components 78 of the stator assembly 72 are energized causes the impeller 54 including the rotor assembly 76 to rotate about the impeller axis I with respect to the stator assembly 72 and the shroud 74. Accordingly, any type of motor suitable for use with the topology described, such as a switch reluctance motor, permanent magnet motor, flux switching permanent magnet motor, and an induction motor for example, are contemplated herein.

[0034] In the embodiments illustrated and described herein, the interactive components 80 do not include an external electrical connection independent from the stator assembly 72. However, it should be understood that embodiments where the interactive components 80 require an electrical connection, such as for a squirrel cage for example are also contemplated herein. In addition, embodiments where the interactive components 80 mounted to the impeller 54 are operable to drive rotation of the impeller 54 are also contemplated herein. In such embodiments, wiring associated with the electrical components 78 may be located within an interior of the impeller shaft 64.

[0035] As previously suggested, the type and number of electrical components 78 of the stator assembly 72 and interactive components 80 of the rotor assembly 76 may vary based on the desired performance of the compressor 22. Accordingly, to increase the amount of interactive components 80 of the rotor assembly 76, the impeller 54 may have an elongated conical shape resulting in an increased axial flow distance relative to conventional compressors. The spatial positioning between the electrical components 78 of the stator assembly 72 and the adjacent interactive components 80 of the rotor assembly 76 is defined by the shape and size of not only the impeller 54, but also the shroud 74. The gap or clearance 82 between the electrical components 78 of the stator assembly 76 and the interactive components 80 of the rotor assembly 76 may be generally constant for ease of manufacturing. However, embodiments where the clearance 82 varies, such as about the periphery of impeller 54 and/or along an axial length of the impeller 54 for example, are also contemplated herein.

[0036] Integrating the electric motor 52 into the impeller 54 results in a compressor 22 having a more compact foot print. By eliminating the components associated with a separate electrical motor, such as the transmission, rotor shaft, and bearing for example, the complexity and weight, as well as the costs associated with the compressor 22 are reduced relative to more traditional compressor systems. Further, friction and windage losses may be reduced by eliminating the frictional losses of a motor separate from the impeller.

[0037] While the disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described embodiments. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.