Patent Application
20200325899
The subject matter disclosed herein relates generally to fluid machines, and more specifically, to fluid machines, such as compressors, having helically lobed rotors.
It has been determined that commonly used refrigerants, such as R-410A in one non-limiting example, have unacceptable global warming potential (GWP) such that their use will cease for many HVAC&R applications. Non-flammable, low GWP refrigerants are replacing existing refrigerants in many applications, but have lower density and do not possess the same cooling capacity as existing refrigerants. Replacement refrigerants require a compressor capable of providing a significantly greater displacement, such as a screw compressor.
Existing screw compressor typically utilized roller, ball, or other rolling element bearings to precisely position the rotors and minimize friction during high speed operation. However, for typical HVAC&R applications, existing screw compressors with roller element bearings result in an unacceptable large and costly fluid machine.
Therefore, there exists a need in the art for an appropriately sized and cost effective fluid machine that minimizes friction while allowing precise positioning and alignment of the rotors.
According to one embodiment, a fluid machine includes a first rotor rotatable about a first axis, a second rotor rotatable about a second axis, a casing for supporting said first rotor and said second rotor, a sump having a volume of lubricant contained therein, a first lubricant passage for supplying lubricant from the sump to a dynamic interface associated with the first rotor, and a second lubricant passage for supplying lubricant from the sump to a dynamic interface associated with the second rotor. A pressure differential created within the fluid machine supplies the lubricant from the sump to the first lubricant passage and the second lubricant passage.
In addition to one or more of the features described above, or as an alternative, in further embodiments during operation of the fluid machine, the pressure differential is formed between a high pressure adjacent at least one end of the casing and low pressure at a central location of the first rotor and the second rotor.
In addition to one or more of the features described above, or as an alternative, in further embodiments said lubricant is supplied from said sump to said first lubricant passage and said second lubricant passage simultaneously.
In addition to one or more of the features described above, or as an alternative, in further embodiments said first rotor is rotatably mounted to the casing without roller element bearings.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first rotor includes a first shaft rotatably mounted to the casing, wherein at least one surface of the casing and the first shaft define the dynamic interface associated with the first rotor.
In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one surface of the casing arranged in direct contact with the first shaft functions as a bearing.
In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one surface of the casing arranged in direct contact with the first shaft includes a first surface arranged in direct contact with a portion the first shaft adjacent a first end, and a second surface arranged in direct contact with a portion the first shaft adjacent a second end.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first lubricant passage includes a first portion for supplying lubricant to the first surface and a second portion, distinct from the first portion, for supplying lubricant to the second surface, wherein lubricant is supplied to both the first portion and the second portion simultaneously.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first lubricant passage further comprises: a cavity formed in a portion of the casing adjacent the first shaft, a passage extending axially through at least a portion of the first shaft, at least one radial hole coupling the cavity and the passage, and a groove extending from the cavity to an interior of a compression pocket formed between the first rotor and the second rotor and the casing.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first lubricant passage further comprises: a counter bore formed at the interface between the casing and the compression pocket.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first lubricant passage comprises: a groove extending from the sump to an interior of a compression pocket formed between the first rotor and the second rotor and the casing.
In addition to one or more of the features described above, or as an alternative, in further embodiments the second rotor further comprises: a second shaft supported by the casing, and a working portion rotatable relative to the second shaft. The second shaft and the working portion define the dynamic interface associated with the second rotor.
In addition to one or more of the features described above, or as an alternative, in further embodiments the second lubricant passage further comprises: a first passage extending axially through at least a portion of the second shaft, a second passage formed in an outer periphery of the second shaft, and at least one radial hole coupling the first passage and the second passage.
In addition to one or more of the features described above, or as an alternative, in further embodiments the second passage extends axially such that a first end of the second passage is fluidly coupled to a first portion of the casing and a second, opposite end of the second passage is fluidly coupled to a second portion of the casing.
In addition to one or more of the features described above, or as an alternative, in further embodiments a counter bore is formed in the casing where at least one of the first lubricant passage and the second lubricant passage enters a compression pocket formed between the first rotor and the second rotor.
In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a recess is formed in the casing in fluid communication with the counter bore, the recess being arranged at an angle towards an interface between the first rotor and the second rotor.
In addition to one or more of the features described above, or as an alternative, in further embodiments at least one of an angle, length, width, and depth of the recess is optimized to control a flow of lubricant to the compression pocket.
According to another embodiment, a method of lubricating one or more dynamic interfaces of a fluid machine includes supplying lubricant from a sump to a dynamic interface associated with a first rotor of the fluid machine via a first lubricant passage, and supplying lubricant from a sump to a dynamic interface associated with a second rotor of the fluid machine via a second lubricant passage. The second lubricant passage is distinct from the first lubricant passage. Supplying lubricant to the dynamic interface associated with the first rotor and the dynamic interface associated with the second rotor occurs automatically in response to a pressure differential created within the fluid machine during operation of the fluid machine.
In addition to one or more of the features described above, or as an alternative, in further embodiments supplying lubricant from a sump to a dynamic interface associated with a first rotor and supplying lubricant from a sump to a dynamic interface associated with a second rotor occurs simultaneously.
In addition to one or more of the features described above, or as an alternative, in further embodiments supplying lubricant from a sump to a dynamic interface associated with a first rotor and supplying lubricant from a sump to a dynamic interface associated with a second rotor occurs without a pump or control valve.
In addition to one or more of the features described above, or as an alternative, in further embodiments supplying lubricant from a sump to a dynamic interface associated with a first rotor further comprises: supplying lubricant via a first passage to a first bearing surface, the first passage extending through an opening formed in a first shaft of the first rotor, and supplying lubricant via a second passage to a second bearing surface.
In addition to one or more of the features described above, or as an alternative, in further embodiments comprising supplying lubricant from the dynamic interface associated with a first rotor and the dynamic interface associated with a second rotor to a compression pocket formed between the first rotor and the second rotor.
The subject matter, which is regarded as the 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 disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the drawings.
Referring now to the
The fluid machine 20 includes a first shaft 34 fixed for rotation with the first rotor 22. The fluid machine 20 further include a casing 36 rotatably supporting the first shaft 34 and at least partially enclosing the first rotor 22 and the second rotor 24. A first end 38 and a second end 40 of the casing 36 are configured to rotatably support the first shaft 34. In the illustrated, non-limiting embodiment, the first, lower end 38 of the casing 36 is formed by a lower bearing housing 42 and the second, upper end 40 of the casing 36 is formed by a distinct upper bearing housing 44. A rotor case 46 may extend between and couple the lower and upper bearing housings 42, 44. However, embodiments where the lower bearing housing 42 and/or the upper bearing housing 44 is integrally formed with the rotor case 46 are also contemplated herein.
The first shaft 34 of the illustrated embodiments is directly coupled to an electric motor 48 operable to drive rotation of the first shaft 34 about an axis X. Any suitable type of electric motor 48 is contemplated herein, including but not limited to an induction motor, permanent magnet (PM) motor, and switch reluctance motor for example. In an embodiment, the first rotor 22 is fixed to the first shaft 34 by a fastener, coupling, integral formation, interference fit, and/or any additional structures or methods known to a person having ordinary skill in the art (not shown), such that the first rotor 22 and the first shaft 34 rotate about axis X in unison.
The fluid machine 20 additionally includes a second shaft 50 operable to rotationally support the second rotor 24. The second rotor 24 includes an axially extending bore 52 within which the second shaft 50 is received. In an embodiment, the second shaft 50 is stationary or fixed relative to the casing 36 and the second rotor 24 is configured to rotate about the second shaft 50. However, embodiments where the second shaft 50 is also rotatable relative to the casing 36 are also contemplated herein.
With specific reference to
By including lobes 30, 32 with having opposite helical configurations, opposing axial flows are created between the first and second helical lobes 30, 32. Due to the symmetry of the axial flows, thrust forces resulting from the helical lobes 30, 32 are generally equal and opposite, such that the thrust forces substantially cancel one another. As a result, this configuration of the opposing helical lobes 30, 32 provides a design advantage since the need for thrust bearings in the fluid machine can be reduced or eliminated.
The second rotor 24 has a first portion 54 configured to mesh with the first helical lobes 30 and a second portion 56 configured to mesh with the second helical lobes 32. To achieve proper intermeshing engagement between the first rotor 22 and the second rotor 24, each portion 54, 56 of the second rotor 24 includes one or more lobes 58 having an opposite configuration to the corresponding helical lobes 30, 32 of the first rotor 22. In the illustrated, non-limiting embodiment, the first portion 54 of the second rotor 24 has at least one right-handed lobe 58a, and the second portion 56 of the second rotor 24 includes at least one left-handed lobe 58b.
In an embodiment, the first portion 54 of the second rotor 24 is configured to rotate independently from the second portion 56 of the second rotor 24. However, embodiments where the first and second portions 54, 56 are rotationally coupled are also contemplated herein. Each portion 54, 56 of the second rotor 24 may include any number of lobes 58. In an embodiment, the total number of lobes 58 formed in each portion 54, 56 of the second rotor 24 is generally larger than a corresponding portion of the first rotor 24. For example, if the first rotor 22 includes four first helical lobes 30, the first portion 54 of the second rotor 24 configured to intermesh with the first helical lobes 30 may include five helical lobes 58a. However, embodiments where the total number of lobes 58 in a portion 54, 56 of the second rotor 24 is equal to a corresponding group of helical lobes (i.e. the first helical lobes 30 or the second helical lobes 32) of the first rotor 22 are also within the scope of the disclosure.
Returning to
With reference now to
As best shown in
In an embodiment, a groove 80 extends over the axial length of the surface 72. This groove 80 is arranged in fluid communication with the cavity 68 and is configured to distribute lubricant from the cavity 68 over the axial length of the first surface 72. Alternatively, or in addition, a groove 84 extends over the axial length of the surface 76. The groove 84 is configured to distribute lubricant from the sump 61 located adjacent the lower bearing housing 42.
A second shaft passage 86 extends axially through the lower bearing housing 42 and at least a portion of the second shaft 50. In the illustrated, non-limiting embodiment, the second shaft passage 86 extends over about half of the axial length of the second shaft 50. However, a shaft passage 86 of any length is contemplated herein. With reference now to
During operation of the fluid machine 20, the relatively high pressure discharge at outer ends 38, 40 of the casing 36, and the relatively low pressure suction at a central location of the first rotor 22 and the second rotor 24, urges or draws lubricant from the sump 61 through the lubricant supply passages associated with the first and second rotors 22, 24. More specifically, lubricant will flow from the sump 61 through the first shaft passage 60, the axial groove 84 formed in surface 76 of the lower bearing housing 42, and through the second shaft passage 86 simultaneously. The lubricant supply passages are intended to lubricate the surfaces 72, 74, and 76 of the upper and lower bearing housings 42, 44 that function as bearings for the first shaft 34, and the interface between the second shaft 50 and the second rotor 24 to reduce friction there between.
A counter bore 78, 82, 92, 94 may be formed in the surfaces of the lower bearing housing 42 and the upper bearing housing 44 facing the first and second rotors 22, 24, respectively. The counterbore 78 may be arranged in fluid communication with the groove 80. The counterbore 82 may be arranged in fluid communication with the groove 84. As a result, lubricant will flow to each of the counter bores 78, 82 after lubricating the respective surfaces 72, 74, and 76. Also, the counterbore 92, 94 may be arranged in fluid communication with the axial passage 88. As a result, lubricant will flow to the counter bores 92, 94 after lubricating the interface between the second shaft 50 and the second rotor 24. In an embodiment, a recess 96 may extend from one or more of the counter bores 78, 82, 92, 94 at an angle towards the interface between the first rotor 22 and the second rotor 24. Although the fluid machine illustrated and described herein includes a recess formed at each of the counter bores, embodiments where none or only some of the counter bores includes a recess are also within the scope of the disclosure.
The configuration of each recess 96, such as the angle, length, width, and depth for example, may be optimized to control the amount of lubricant flow to the compression pocket. In an embodiment, the recess 96 has a linear contour and is aligned with the interface between the lobes 30, 32 of the first rotor 22 and the corresponding lobes 58a, 58b of the second rotor 24. Accordingly, as shown
By positioning the recess 96 in alignment with the intermeshing engagement of the rotors 22, 24, the recess communicates with both the high pressure and low pressure areas adjacent the first rotor 22 and second rotor 24. As a result, lubricant may flow from the recess 96 into the compression pocket formed between the first and second rotors 22, 24. In an embodiment, the length of the recess 96, measured radially from the origin of the bore for receiving a corresponding shaft 34 or 50 is greater than a root radius of the rotor 22 or 24. Further, the length of the recess 96 may be greater than the root radius, but less than the tip radius of the rotor 22 or 24 associated therewith. In an embodiment, a width of the recess 96, measured perpendicular to the length, is between 1 mm and 10 mm, and a depth of the recess 96 extending into the lower or upper bearing housing 42, 44 is between 1-5 times the axial length of the clearance between the rotor 22 or 24 and the adjacent surface of the lower or upper bearing housing 42, 44. It should be understood that in embodiments including a plurality of recesses, the configuration of recesses may be the same, or alternatively, may be different.
The fluid machine 20 illustrated and described herein provides a simple and low cost configuration for a lubricant supply system. Because the pressure of the machine 20 is used to draw the fluid to the respective interfaces, costly devices, such as a pump or control valve for example, are not required. Further, because the lubricant is driven by the pressure differential created during operation of the machine 20, a stable supply of lubricant is provided over a wide range of shaft speeds.
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 disclosure 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.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/056101 | 10/16/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62576430 | Oct 2017 | US |
