Refrigerant compressor with impeller having slotted shroud

Abstract

A refrigerant compressor and a method of operating the same. The refrigerant compressor can include an impeller with a shroud including a passageway that allows refrigerant to flow from a radially outer location of the shroud of the impeller to a radially inner location of the shroud. The method can include operating the refrigerant compressor including the impeller with the shroud to cause the impeller with the shroud to rotate within a housing, and directing a leakage flow between the impeller with the shroud and the housing back into the impeller with the shroud through the passageway that extends radially through the shroud of the impeller.

Description

Background Technology

[0001] A refrigerant compressor is used to circulate refrigerant within a refrigeration unit via a refrigerant loop. The refrigerant loop is known to include a condenser, an expander, and an evaporator. The compressor compresses the fluid, which then travels to the condenser, where it is cooled and condensed. The refrigerant then enters the expander, which reduces the fluid pressure, and finally enters the evaporator, where the fluid is evaporated, thus completing the refrigeration cycle.

[0002] Many refrigerant compressors are centrifugal compressors and have an electric motor that drives at least one impeller to compress the refrigerant. Fluid flows axially into the impeller and exits radially from it. The fluid is then directed downstream for use in a refrigeration system. Some known refrigerant compressors include a shrouded impeller comprising a circumferentially extending shroud or wall that connects to the ends of the impeller blades, allowing refrigerant to flow in and out of the impeller. Summary of the Invention

[0003] In some aspects, the technology described herein relates to a refrigerant compressor comprising: a shrouded impeller having a passageway allowing refrigerant to flow from a radially outer position of the shroud of the shroud to a radially inner position of the shroud.

[0004] In some respects, the technology described herein relates to a refrigerant compressor, wherein the passage is a slot.

[0005] In some respects, the technology described herein relates to a refrigerant compressor in which the slot is axially spaced between the leading and trailing edges of the shrouded impeller.

[0006] In some aspects, the technology described herein relates to a refrigerant compressor in which: the shrouded impeller comprises a plurality of main blades, the shrouded impeller includes a split vane between adjacent main blades, and the slot is arranged downstream of the leading edge of the main blades and upstream of the leading edge of the split vane.

[0007] In some respects, the technology described herein relates to a refrigerant compressor in which the slot extends through the shroud at an angle other than 90° relative to the axis of rotation of the shrouded impeller.

[0008] In some aspects, the technology described herein relates to a refrigerant compressor, wherein the slot extends through the shroud at an angle substantially perpendicular to the profile of the tip of the blades of the shrouded impeller at an axial position of the slot.

[0009] In some aspects, the technology described herein relates to a refrigerant compressor in which the outer wall of the shroud provides part of a sealing assembly at an axial position between the leading edge of the shrouded impeller and the slot.

[0010] In some respects, the technology described herein relates to a refrigerant compressor, wherein the slot is one of a plurality of slots of the shrouded impeller.

[0011] In some respects, the technology described herein relates to a refrigerant compressor, wherein the passage is a series of orifices.

[0012] In some respects, the technology described herein relates to a refrigerant compressor in which the shrouded impeller comprises a plurality of series of orifices.

[0013] In some aspects, the technology described herein relates to a refrigerant compressor in which each of the plurality of series of orifices is axially aligned with each other and circumferentially spaced apart from each other.

[0014] In some respects, the technology described herein relates to a refrigerant compressor, wherein the hole is formed by drilling.

[0015] In some respects, the technology described herein relates to a refrigerant compressor in which, within each series of orifices, each orifice is spaced apart by an amount equal to approximately one-quarter of the diameter of the orifice.

[0016] In some aspects, the technology described herein relates to a refrigerant compressor, wherein each of the plurality of series of orifices comprises 8 to 10 orifices.

[0017] In some aspects, the technology described herein relates to a method comprising: operating a refrigerant compressor comprising a shrouded impeller such that the shrouded impeller rotates within a housing; and guiding a leakage flow between the shrouded impeller and the housing back to the shrouded impeller through a passage extending radially through the shroud of the shrouded impeller. Attached Figure Description

[0018] Figure 1 A schematic example illustrates a refrigerant system.

[0019] Figure 2 The illustration shows a cross-section of a portion of an exemplary refrigerant compressor.

[0020] Figure 3 Example illustration of an exemplary impeller.

[0021] Figure 4 Example illustration of an exemplary shield.

[0022] Figure 5 This is a three-dimensional end view of an exemplary impeller with a protective cover.

[0023] Figure 6 Illustrative example Figure 5 A cross-section of an exemplary arrangement of a shielded impeller.

[0024] Figure 7 Here is another exemplary stereoscopic end view of an impeller with a protective shield. Detailed Implementation

[0025] Figure 1 This example illustrates a refrigerant system 10. The refrigerant system 10 includes a main refrigerant loop or circuit 12 in communication with a refrigerant compressor 14, a condenser 13, an evaporator 15, and an expansion device 17. For example, this refrigerant system 10 can be used in a refrigeration unit. In this example, a cooling tower may be in fluid communication with the condenser 13. While a specific example of a refrigerant system 10 is shown, this application extends to other refrigerant system configurations, including those excluding refrigeration units. For example, the main refrigerant loop 12 may include an economizer located downstream of the condenser 13 and upstream of the expansion device 17.

[0026] Figure 2 An exemplary refrigerant compressor 14 according to this disclosure is illustrated schematically. The refrigerant compressor 14 includes a housing 20, within which an electric motor 16 is disposed. The housing 20 is schematically depicted and may include one or more components. The electric motor 16 drives an impeller 18 rotatably about a central axis X via a rotor shaft 22 to compress refrigerant. The rotor shaft 22 may include one or more components. The illustrated refrigerant compressor 14 is a centrifugal compressor, meaning that the impeller 18 is specifically configured to discharge fluid in a direction away from the axis of rotation, which is here the axis X of shaft 22. In particular, the impeller 18 has an outlet 28 radially external to an inlet 24, wherein the outlets 28 are axially spaced downstream of the inlet 24. The compressed refrigerant then exits the refrigerant compressor 14 via an outlet volute 32. While reference is made herein to a refrigerant compressor 14, this disclosure is not limited to any particular working fluid but extends to systems configured for other fluids such as air, water, etc.

[0027] In this example, impeller 18 is a shrouded impeller. That is, a circumferentially extending shroud 30 or wall partially encloses impeller 18 and specifically connects to the tips of the impeller blades, thereby increasing blade rigidity. In this disclosure, the term "impeller" is used to refer to the central hub and the impeller blades projecting from the hub, not to the shroud. However, in the art, the assembly comprising a hub, blades, and shroud is sometimes collectively referred to as "impeller," as a shorthand for "shrouded impeller." In this disclosure, the assembly comprising a hub, blades, and shroud will be referred to as a shrouded impeller, impeller assembly, or simply assembly. In one example, shroud 30 is permanently attached to impeller 18 by brazing. Impeller 18 and shroud 30 rotate together with shaft 22.

[0028] Figure 3 Example illustration of an exemplary impeller 18. Impeller 18 has a plurality of blades 34 arranged circumferentially around a central axis X. When the refrigerant is compressed, the blades 34 guide the refrigerant between inlet 24 and outlet 28.

[0029] Figure 4 The example illustrates an exemplary shroud 30. The shroud 30 fits onto the impeller 18 and contacts the tip of the blades 34. For example, the shroud 30 and impeller 18 can be metallic components. The shroud 30 and impeller 18 can be made of the same material or different materials.

[0030] During operation of the refrigerant compressor 14, fluid is radially discharged from the outlet 28 of the impeller 18. As discussed overall above, most of the discharged flow travels downward toward the diffuser and eventually reaches the volute 32. However, some flow remains in the gap 35 between the impeller 18 and the housing 20. Figure 6 Leakage occurs between the blades 34 and the impeller 18, and within this gap 35, the flow generally returns from the location adjacent to the outlet 28 toward the inlet 24. To reduce this leakage, various seals can be placed. In this disclosure, the shroud 30 is configured to redirect the leaked flow into the impeller 18, and specifically to the main flow path of the impeller 18, which is inside the shroud 30 and between the blades 34.

[0031] In this example, the shroud 30 includes a plurality of slots 36 extending radially through the shroud 30 to allow fluid to flow from a radially outer position to a radially inner position, where the fluid merges with fluid within the impeller 18. The slots 36 are oriented around an axis X ( Figure 5 They are circumferentially spaced apart from each other. Slot 36 can be referred to as a channel.

[0032] Now refer to Figure 5 and Figure 6An exemplary arrangement of slot 36 is described. In this example, impeller 18 extends between a leading edge 38 and a trailing edge 40. Impeller 18 includes a central hub 42 and two different types of blades 34, which in this example extend between the central hub 42 (at the root of the blade) and a shroud 30 (at the tip of the blade). Specifically, impeller 18 includes main blades 34A extending axially between a leading edge 44 and a trailing edge 46, the leading edge 44 being axially spaced behind the leading edge 38, and the trailing edge 46 extending substantially together with the trailing edge 40. Impeller 18 further includes a splitting blade 34B, wherein a splitting blade 34B exists between adjacent main blades 34A to provide an alternating arrangement, the splitting blade extending axially between a leading edge 48 and a trailing edge 50, the leading edge 48 being axially spaced behind the leading edge 44, and the trailing edge 50 extending substantially together with the trailing edges 40, 46.

[0033] The cross-section of the slot 36 can be rectangular, wherein the length dimension of the rectangle substantially corresponds to the circumferential distance between adjacent main blades 34A of the impeller 18. However, the cross-section of the slot 36 can be other shapes.

[0034] In this example, the shroud 30 has a wall thickness between the inner wall 52 and the outer wall 54. The inner wall 52 faces and provides the boundary of the main flow path of the impeller 18. The inner wall 52 also contacts the tip of the blade 34. The outer wall faces and provides the inner boundary of the gap 35. In this example, the slot 36 extends completely through the wall thickness of the shroud 30 from the inner wall 52 to the outer wall 54. In this way, fluid within the gap 35 can flow back from the gap 35 to the main flow path through the slot 36.

[0035] In this example, slot 36 is arranged such that it is axially spaced between the leading edge 38 and the trailing edge 40 of impeller 18. Further, slot 36 is arranged such that it intersects the inner wall 54 at a location downstream of the leading edge 44 of the main blade 34A and upstream of the leading edge 48 of the splitter blade 34B. Slot 36 may be located at another location, such as upstream of the leading edge 44 or downstream of the leading edge 48.

[0036] Slot 36 is tilted at an angle other than 90° relative to axis X, such that slot 36 extends substantially perpendicular to the profile of the ends of the main blade 34A and the splitter blade 34B at the location of slot 36. In other examples, slot 36 may be tilted in a different manner.

[0037] Axially, between the slot 36 and the leading edge 38 of the impeller 18, the outer wall 54 and the housing 20 are configured to provide a sealing assembly 56. In this example, the outer wall 54 includes a plurality of knife-edge seals and the housing 20 includes a plurality of platforms corresponding to and configured to abut the knife-edge seals. The sealing assembly 56 may be arranged in another manner. The sealing assembly 56 is used to direct fluid within the gap 35 to the slot 36 and ultimately to the main flow path of the impeller 18.

[0038] During operation of the refrigerant compressor 14, fluid F1, i.e., the refrigerant, enters the impeller 18 through inlet 24, flows along the main flow path of the impeller 18, is pressurized, and exits from outlet 28. A majority of fluid F1 (labeled F2 herein) flows to the diffuser and then downstream, such as to the volute 32. A portion of fluid F1, labeled F3, leaks and flows into the gap 35. In this disclosure, this portion F3 is redirected back into the main flow path of the impeller 18 via slot 36. In one example, approximately 3% of fluid F1 becomes portion F3. Recirculating the fluid within the gap 35 back into the impeller 18 passively improves the surge range of the refrigerant compressor 14, meaning there is no active control mechanism, such as a valve, determining the flow through the gap 35 and / or slot 36.

[0039] Figure 7 The example illustrates an exemplary impeller 118, which is constructed substantially the same as impeller 18, but instead of slots 36 providing a passage for leakage flow, impeller 118 replaces each slot 36 with a series of holes 136. Each series of holes 136 comprises a plurality of holes 138. The holes 138 are axially aligned with each other and circumferentially spaced apart. The holes 138 extend through the shroud 30 to press against... Figure 6 The flow F3 is passively recirculated in the same manner as shown. In this respect, impeller 118 functions essentially equivalent to impeller 18. The holes 138 can be formed by drilling, which increases the ease of manufacturing impeller 118 compared to when the impeller includes elongated slots 36. Within each series of holes 136, the holes 138 are spaced relatively small apart, such as approximately 0.25 mm, or approximately one-quarter of the diameter of the hole 138; in this example, the holes 138 have a diameter of approximately 1 mm. The circumferential spacing between each series of holes 136 and adjacent series of holes 136 is greater than the diameter of the hole 138. In the example, each series of holes 136 contains 8-10 holes 138. The number of holes 138 within each series of holes 136, as well as the relative spacing of the holes 138 and the relative spacing of the series of holes 136, can be determined based on the desired amount of recirculated flow.

[0040] It should be understood that the terms "axial," "radial," and "circumferential" are used above in reference to the normal operating conditions of the compressor and the compressor's central axis. In some accompanying drawings, the axial direction is often labeled "A," and the radial direction is often labeled "R." Furthermore, these terms are used herein for illustrative purposes and should not be considered restrictive. Terms such as "generally," "approximately," and "substantially" are not unbounded terms and should be interpreted in accordance with the manner in which those skilled in the art interpret these terms.

[0041] Although the different examples have the specific components shown in the figures, the embodiments of this disclosure are not limited to these specific combinations. Some components or features of one example may be used in combination with features or components of another example. In addition, the various figures accompanying this disclosure are not necessarily drawn to scale, and some features may be enlarged or reduced to show certain details of a particular component or arrangement.

[0042] Those skilled in the art will understand that the above embodiments are exemplary and not restrictive. That is, modifications to this disclosure will fall within the scope of the claims. Therefore, the following claims should be studied to determine their true scope and content.

Claims

1. A refrigerant compressor, comprising: A shrouded impeller, the shrouded impeller including passages that allow refrigerant to flow from a radially outer position of the shroud of the shroud to a radially inner position of the shroud. The passage is a narrow slot. The slots are axially spaced between the leading and trailing edges of the shrouded impeller. The shrouded impeller comprises multiple main blades. The shrouded impeller includes splitter blades between adjacent main blades, and The slot is arranged downstream of the leading edge of the main blade and upstream of the leading edge of the splitter blade.

2. The refrigerant compressor according to claim 1, wherein, The slot extends through the shroud at an angle other than 90° relative to the axis of rotation of the shroud-enclosed impeller.

3. The refrigerant compressor according to claim 2, wherein, The slot extends through the shroud at an angle substantially perpendicular to the profile of the tip of the blade of the shroud impeller at its axial position.

4. The refrigerant compressor according to claim 1, wherein, The outer wall of the shroud provides part of a sealing assembly at an axial position between the leading edge of the shrouded impeller and the slot.

5. The refrigerant compressor according to claim 1, wherein, The slot is one of a plurality of slots in the shrouded impeller.

6. A method comprising: Operate a refrigerant compressor including a shrouded impeller such that the shrouded impeller rotates within the housing; as well as The leakage flow between the shrouded impeller and the housing is guided back to the shrouded impeller through a passage that extends radially through the shroud of the shrouded impeller. The passage is a narrow slot. The slots are axially spaced between the leading and trailing edges of the shrouded impeller. The shrouded impeller comprises multiple main blades. The shrouded impeller includes splitter blades between adjacent main blades, and The slot is arranged downstream of the leading edge of the main blade and upstream of the leading edge of the splitter blade.

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