CN111247343A

CN111247343A - Lubricant supply passage for compressor

Info

Publication number: CN111247343A
Application number: CN201880069655.0A
Authority: CN
Inventors: M.阿凯
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2017-10-24
Filing date: 2018-10-16
Publication date: 2020-06-05
Also published as: EP3701151B1; US20200325899A1; WO2019083778A1; EP3701151A1; ES2909572T3

Abstract

A fluid machine comprising: a first rotor rotatable about a first axis; a second rotor rotatable about a second axis; a housing for supporting the first and second rotors; an oil sump having a volume of lubricant contained therein; a first lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the first rotor; and a second lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the second rotor. A pressure difference generated within the fluid machine supplies lubricant from the oil groove to the first lubricant passage and the second lubricant passage.

Description

Lubricant supply passage for compressor

Technical Field

The subject matter disclosed herein relates generally to fluid machines (compressors), and more particularly to fluid machines having a helical lobed rotor, such as compressors.

Background

It has been determined that common refrigerants, such as R-410A in one non-limiting example, have unacceptable Global Warming Potential (GWP), and thus their use will cease for many HVAC & R applications. Non-flammable, low GWP refrigerants are replacing existing refrigerants in many applications, but have lower densities and do not have the same cooling capacity as existing refrigerants. Alternative refrigerants require compressors, such as screw compressors, that can provide significantly greater displacement.

Existing screw compressors typically utilize roller, ball or other rolling element bearings to accurately position the rotor and minimize friction during high speed operation. However, for typical HVAC & R applications, existing screw compressors with roller element bearings may result in unacceptably large and expensive fluid machines.

Accordingly, there is a need in the art for a suitably sized and cost effective fluid machine that minimizes friction while allowing precise positioning and alignment of the rotor.

Disclosure of Invention

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 housing for supporting the first and second rotors; an oil sump having a volume of lubricant contained therein; a first lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the first rotor; and a second lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the second rotor. A pressure difference generated within the fluid machine supplies lubricant from the oil groove to the first lubricant passage and the second lubricant passage.

In addition or alternatively to one or more features described above, in other embodiments, a pressure differential is created between a high pressure adjacent at least one end of the housing and a low pressure at a central location of the first and second rotors during operation of the fluid machine.

In addition to one or more of the features described above, or as an alternative, in other embodiments, the lubricant is supplied from the oil groove to the first lubricant passage and the second lubricant passage simultaneously.

In addition to one or more of the features described above, or as an alternative, in other embodiments, the first rotor is rotatably mounted to the housing without a roller element bearing.

In addition or alternatively to one or more of the features described above, in other embodiments, the first rotor includes a first shaft rotatably mounted to the housing, wherein the first shaft and at least one surface of the housing define a dynamic interface associated with the first rotor.

In addition to one or more of the features described above, or as an alternative, in other embodiments at least one surface of the housing arranged in direct contact with the first shaft acts as a bearing.

In addition to one or more features described above, or as an alternative, in other embodiments, the at least one surface of the housing disposed in direct contact with the first shaft includes a first surface disposed in direct contact with a portion of the first shaft adjacent the first end, and a second surface disposed in direct contact with a portion of the first shaft adjacent the second end.

In addition or alternatively to one or more of the features described above, in other embodiments, the first lubricant passage includes a first portion for supplying lubricant to the first surface and a second portion different from the first portion for supplying lubricant to the second surface, wherein lubricant is supplied to the first portion and the second portion simultaneously.

In addition or alternatively to one or more of the features described above, in other embodiments, the first lubricant passage further comprises: a cavity formed in a portion of the housing adjacent the first shaft; a channel extending axially through at least a portion of the first shaft; at least one radial hole connecting the cavity and the channel; and a groove extending from the cavity to an interior of a compression pocket formed between the first and second rotors and the housing.

In addition or alternatively to one or more of the features described above, in other embodiments, the first lubricant passage further comprises: a counterbore formed at an interface between the housing and the compression pocket.

In addition or alternatively to one or more of the features described above, in other embodiments, the first lubricant passage includes: a groove extending from the oil groove to an interior of a compression pocket formed between the first and second rotors and the housing.

In addition or alternatively to one or more of the features described above, in other embodiments the second rotor further comprises: a second shaft supported by the housing, and a working portion rotatable relative to the second shaft. The second shaft and the working portion define a dynamic interface associated with the second rotor.

In addition or alternatively to one or more of the features described above, in other embodiments, the second lubricant passage further comprises: the first channel extends axially through at least a portion of the second shaft, the second channel is formed in an outer periphery of the second shaft, and at least one radial bore couples the first channel and the second channel.

In addition to or as an alternative to one or more features described above, in other embodiments, the second channel extends axially such that a first end of the second channel is fluidly coupled to the first portion of the housing and an opposite second end of the second channel is fluidly coupled to the second portion of the housing.

In addition to one or more of the features described above, or alternatively, in other embodiments, a counterbore is formed in the housing in which at least one of the first and second lubricant passages enters a compression pocket formed between the first and second rotors.

In addition to one or more of the features described above, or alternatively, in other embodiments, a recess is formed in the housing in fluid communication with the counterbore, the recess being disposed at an angle toward the interface between the first and second rotors.

In addition to or as an alternative to one or more of the features described above, in other embodiments at least one of the angle, length, width and depth of the recess is optimized to control lubricant flow to the compression pocket.

According to another embodiment, a method of lubricating one or more dynamic interfaces of a fluid machine includes: the lubricant is supplied from the oil sump via a first lubricant channel to a dynamic interface associated with a first rotor of the fluid machine, and the lubricant is supplied from the oil sump via a second lubricant channel to a dynamic interface associated with a second rotor of the fluid machine. The second lubricant passage is different 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 generated 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 other embodiments, the supplying lubricant from the oil sump to the dynamic interface associated with the first rotor and the supplying lubricant from the oil sump to the dynamic interface associated with the second rotor occur simultaneously.

In addition to one or more of the features described above, or as an alternative, in other embodiments, the supplying lubricant from the oil sump to the dynamic interface associated with the first rotor and the supplying lubricant from the oil sump to the dynamic interface associated with the second rotor occurs without a pump or a control valve.

In addition or alternatively to one or more of the features described above, in other embodiments, supplying lubricant from an oil sump to a dynamic interface associated with the first rotor further comprises: the lubricant is supplied to the first bearing surface via a first passage that extends through an opening formed in the first shaft of the first rotor and supplies the lubricant to the second bearing surface via a second passage.

In addition or alternatively to one or more features described above, in other embodiments, including supplying lubricant from a dynamic interface associated with the first rotor and a dynamic interface associated with the second rotor to a compression pocket formed between the first rotor and the second rotor.

Drawings

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:

FIG. 1 is a cross-sectional view of a fluid machine according to one embodiment;

FIG. 2 is a perspective view of a working portion of a fluid machine according to one embodiment;

FIG. 3 is a cross-sectional view of a fluid machine including a lubricant supply passage according to one embodiment;

FIG. 4 is a cross-sectional view of a working portion of a fluid machine according to one embodiment;

FIG. 5 is a perspective cross-sectional view of a housing of a fluid machine according to one embodiment;

FIG. 6 is a perspective view of a second shaft of the fluid machine according to one embodiment; and is

FIG. 7 is a front view of a surface of a bearing housing facing a compression pocket of a fluid machine according to one embodiment.

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

Detailed Description

Referring now to fig. 1 and 2, a fluid machine 20 is shown. In the non-limiting embodiment shown, the fluid machine 20 is an opposed screw compressor. However, other suitable embodiments of fluid machines, such as pumps, fluid motors, or engines, are also within the scope of the present disclosure. The fluid machine 20 includes a first rotor 22 intermeshed with a second rotor 24. In one embodiment, the first rotor 22 is a male rotor having a male lobed working portion 26 and the second rotor 24 is a female rotor including a female lobed working portion 28. Alternatively, first rotor 22 may be a female rotor and second rotor 24 may be a male rotor. The working portion 26 of the first rotor 22 includes at least one first lobe (lobe, also sometimes referred to as a lobe) 30 and at least one second lobe 32. In the non-limiting embodiment shown, the first rotor 22 includes two separate portions defining a first helical lobe 30 and a second helical lobe 32. In another embodiment, the first rotor 22, including the first lobes 30 and the second lobes 32, may be formed as a single, unitary piece.

The fluid machine 20 includes a first shaft 34 fixed for rotation with the first rotor 22. The fluid machine 20 further includes a housing 36, the housing 36 rotatably supporting the first shaft 34 and at least partially enclosing the first and

second rotors

22, 24. The first and

second ends

38,40 of the housing 36 are configured to rotatably support the first shaft 34. In the non-limiting embodiment shown, the lower first end 38 of the housing 36 is formed by a lower bearing housing 42, and the upper second end 40 of the housing 36 is formed by a different upper bearing housing 44. A rotor housing 46 may extend between and be coupled with the lower bearing housing 42 and the upper bearing housing 44. However, embodiments are also contemplated herein in which the lower bearing housing 42 and/or the upper bearing housing 44 are integrally formed with the rotor housing 46.

The first shaft 34 of the illustrated embodiment is directly coupled to a motor 48 operable to drive rotation of the first shaft 34 about the axis X. Any suitable type of electric motor 48 is contemplated herein, including but not limited to, for example, induction motors, Permanent Magnet (PM) motors, and switched reluctance motors. In one embodiment, the first rotor 22 is secured to the first shaft 34 by fasteners, couplings, integral formations, interference fits, and/or any other structure or method known to those of ordinary skill in the art (not shown) such that the first rotor 22 and the first shaft 34 rotate in unison about the axis X.

The fluid machine 20 additionally includes a second shaft 50 operable to rotatably support the second rotor 24. The second rotor 24 includes an axially extending bore 52 in which the second shaft 50 is received. In one embodiment, the second shaft 50 is stationary or fixed relative to the housing 36, and the second rotor 24 is configured to rotate about the second shaft 50. However, embodiments are also contemplated herein in which the second shaft 50 is also rotatable relative to the housing 36.

Referring specifically to fig. 2, the first rotor 22 is shown to include four first lobes 30 and at least four second lobes 32. The illustrated non-limiting embodiment is intended as an example only, and one of ordinary skill in the art will appreciate that any suitable number of first lobes 30 and second lobes 32 is within the scope of the present disclosure. As shown, the first helical lobe 30 and the second helical lobe 32 have opposite helical configurations. In the non-limiting embodiment shown, the first helical lobe 30 is left-handed and the second helical lobe 32 is right-handed. Alternatively, the first helical lobe 30 may be right-handed and the second helical lobe 32 may be left-handed.

By including

lobes

30,32 having opposite helical configurations, opposite axial flow is created between the first helical lobe 30 and the second helical lobe 32. Due to the symmetry of the axial flow, the thrust forces generated by the

lobes

30,32 are generally equal and opposite such that the thrust forces substantially cancel each other. As a result, this configuration of the opposing

lobes

30,32 provides design advantages in that the need for thrust bearings in a fluid machine may be reduced or eliminated.

The second rotor 24 has a first portion 54 configured to mesh with the first helical lobe 30 and a second portion 56 configured to mesh with the second helical lobe 32. To achieve proper intermeshing engagement between the first and

second rotors

22,24, 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 non-limiting embodiment shown, the first portion 54 of the second rotor 24 has at least one right-hand lobe 58a and the second portion 56 of the second rotor 24 includes at least one left-hand lobe 58 b.

In one embodiment, the first portion 54 of the second rotor 24 is configured to rotate independently of the second portion 56 of the second rotor 24. However, embodiments are also contemplated herein in which first portion 54 and second portion 56 are rotationally coupled. Each

portion

54,56 of the second rotor 24 may include any number of lobes 58. In one embodiment, the total number of lobes 58 formed in each

portion

54,56 of the second rotor 24 is generally greater than the corresponding portion of the first rotor 24. For example, if the first rotor 22 includes four first lobes 30, the first portion 54 of the second rotor 24 configured to intermesh with the first lobes 30 may include five lobes 58 a. However, embodiments in which the total number of lobes 58 in the

portions

54,56 of the second rotor 24 is equal to the corresponding set of lobes (i.e., the first lobes 30 or the second lobes 32) of the first rotor 22 are also within the scope of the present disclosure.

Turning to fig. 1, during operation of fluid machine 20 of one embodiment, a gas or other fluid, such as a low GWP refrigerant, is drawn to a central location by a suction process created by fluid machine 20. Due to the structure and function of the opposing

helical rotors

22,24, the rotation of the first and

second rotors

22,24 compresses the refrigerant and forces the refrigerant toward the outer ends 38,40 of the housing 36. The compressed refrigerant is directed through an internal gas passage within the housing 36 and discharged through an upper end 40 of the housing 36. The discharged refrigerant passes through the motor 48 and exits the discharge outlet 59.

Referring now to fig. 3-7, fluid machine 20 includes one or more lubricant supply passages for providing lubricant from reservoir 61 to the dynamic interface of machine 20. In one embodiment, an oil sump 61 containing a volume of lubricant, such as oil, is adjacent to and in communication with the lower bearing housing 42. The first shaft passage 60 extends axially through at least a portion of the first shaft 34. In the non-limiting embodiment shown, the first shaft passage 60 extends from adjacent the lower end 38 of the housing 36 to adjacent the upper end 40 of the housing 36.

As best shown in fig. 4 and 5, in one embodiment, a cavity 68 formed in the upper bearing housing 64 is configured to surround the periphery of a portion of the first shaft 34. At least one radial bore 70 extends between the first shaft passage 60 to the outer surface of the shaft 34 to deliver lubricant to the cavity 68. In the non-limiting embodiment shown, two radial bores 70 extend in opposite directions relative to each other from the first shaft passage 60 to the outer surface of the shaft 34. In addition, one or more surfaces formed in the upper bearing portion 44 and configured to contact the bore of the first shaft 34 may serve as bearings. For example, referring to FIG. 5, a first surface 72 disposed adjacent a first side of the cavity 68 may operate as a primary bearing, and a second surface 74 disposed adjacent an opposite second side of the cavity 68 may operate as a secondary bearing. Similarly, a bore formed in the lower bearing portion 62 for receiving a portion of the first shaft 34 includes a surface 76 operable as a bearing.

In one embodiment, the groove 80 extends the axial length of the surface 72. The groove 80 is disposed in fluid communication with the cavity 68 and is configured to dispense lubricant from the cavity 68 over the axial length of the first surface 72. Alternatively or additionally, the groove 84 extends over the axial length of the surface 76. Groove 84 is configured to dispense lubricant from oil sump 61 located adjacent 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 non-limiting embodiment shown, the second shaft passage 86 extends over about half of the axial length of the second shaft 50. However, any length of the shaft passage 86 is contemplated herein. Referring now to fig. 6, an axially extending passage 88 is formed in the outer periphery of the second shaft 50, and at least one radial bore 90 fluidly couples the shaft passage 86 and the axial passage 88. In one embodiment, the radial bore is generally centrally disposed with respect to the shaft passage such that a portion of the lubricant is distributed in both directions with respect to the radial bore 90. However, embodiments are also contemplated herein in which the radial hole 90 is disposed near one end of the channel 88 or at another location. The axial passages 88 are configured to distribute lubricant at an interface formed between the second shaft 50 and the bore 52 formed in the second rotor 24. In one embodiment, the axial passage 88 extends between the upper bearing housing 44 and the lower bearing housing 42.

During operation of fluid machine 20, the relatively high pressure discharged at outer ends 38,40 of housing 36, and the relatively low pressure drawn at the central location of first and

second rotors

22,24, propel or draw lubricant from oil sump 61 through lubricant supply passages associated with first and

second rotors

22, 24. More specifically, lubricant will flow from the oil groove 61 simultaneously through the first shaft passage 60, the axial groove 84 formed on the surface 76 of the lower bearing housing 42, and through the second shaft passage 86. The lubricant supply channels are intended to lubricate the

surfaces

72,74 and 76 of the upper and

lower bearing housings

42 and 44, which serve as bearings for the first shaft 34, and the interface between the second shaft 50 and the second rotor 24 to reduce friction therebetween.

Counterbores

78,82,92,94 may be formed in the surfaces of lower bearing housing 42 and upper bearing housing 44 facing first rotor 22 and second rotor 24, respectively. The counterbore 78 may be placed in fluid communication with the groove 80. Counterbore 82 may be placed in fluid communication with groove 84. As a result, after lubricating the

respective surfaces

72,74, and 76, the lubricant will flow to each

counterbore

78, 82. Likewise, the

counterbores

92,94 may be disposed in fluid communication with the axial passage 88. As a result, after lubricating the interface between second shaft 50 and second rotor 24, the lubricant will flow to

counterbores

92, 94. In one embodiment, the recess 96 may extend from one or more of the

counterbores

78,82,92,94 at an angle toward the interface between the first and

second rotors

22, 24. Although the fluid machines shown and described herein include a recess formed at each counterbore, embodiments in which none or only some of the counterbores include a recess are within the scope of the invention.

The configuration of each recess 96, such as, for example, angle, length, width, and depth, may be optimized to control the amount of lubricant flow to the compression pockets. In one embodiment, the recesses 96 have a linear profile and are 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. Thus, as shown in fig. 6, the recess 96 is angled between 0 and 60 degrees relative to an axis extending through the origin of both the first shaft 34 and the second shaft 50.

By positioning the recesses 96 in alignment with the intermeshing engagement of the

rotors

22,24, the recesses communicate with high and low pressure regions adjacent the first and

second rotors

22, 24. As a result, lubricant may flow from the recess 96 into the compression pockets formed between the first and

second rotors

22, 24. In one embodiment, the length of the recess 96 (measured radially from the origin of the bore for receiving the corresponding shaft 34 or 50) is greater than the 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 with which it is associated. In one embodiment, the width of the recess 96 measured perpendicular to the length is between 1mm and 10mm, and the depth of the recess 96 extending into the lower bearing housing 42 or the upper bearing housing 44 is between 1-5 times the axial length of the gap between the

rotor

22 or 24 and the adjacent surface of the lower bearing housing 42 or the upper bearing housing 44. It should be understood that in embodiments including multiple recesses, the configuration of the recesses may be the same, or alternatively, may be different.

The fluid machine 20 shown and described herein provides a simple and low cost construction for a lubricant supply system. Because the pressure of machine 20 is used to draw fluid to the various ports, no expensive devices, such as pumps or control valves, are required. Further, because the lubricant is driven by the pressure differential created during operation of 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.

Claims

1. A fluid machine comprising:

a first rotor rotatable about a first axis;

a second rotor rotatable about a second axis;

a housing for supporting the first and second rotors;

an oil sump having a volume of lubricant contained therein;

a first lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the first rotor; and

a second lubricant passage for supplying lubricant from the oil sump to a dynamic interface associated with the second rotor, wherein a pressure differential created within a fluid machine supplies the lubricant from the oil sump to the first lubricant passage and the second lubricant passage.

2. The fluid machine according to claim 1, wherein, during operation of the fluid machine, the pressure difference is formed between a high pressure near at least one end of the housing and a low pressure at a central position of the first and second rotors.

3. The fluid machine according to claim 1, wherein the lubricant is supplied from the oil groove to the first lubricant passage and the second lubricant passage simultaneously.

4. The fluid machine of claim 1, wherein the first rotor is rotatably mounted to the housing without a roller element bearing.

5. The fluid machine of claim 1, wherein the first rotor includes a first shaft rotatably mounted to the housing, wherein the first shaft and at least one surface of the housing define a dynamic interface associated with the first rotor.

6. Fluid machine according to claim 5, wherein at least one surface of the housing arranged in direct contact with the first shaft acts as a bearing.

7. The fluid machine of claim 6, wherein the at least one surface of the housing disposed in direct contact with the first shaft includes a first surface disposed in direct contact with a portion of the first shaft adjacent a first end and a second surface disposed in direct contact with a portion of the first shaft adjacent a second end.

8. The fluid machine according to claim 7, wherein the first lubricant passage includes a first portion for supplying lubricant to the first surface and a second portion different from the first portion for supplying lubricant to the second surface, wherein lubricant is supplied to both the first portion and the second portion at the same time.

9. The fluid machine according to claim 5, wherein the first lubricant passage further includes:

a cavity formed in a portion of the housing adjacent the first shaft;

a channel extending axially through at least a portion of the first shaft;

at least one radial hole coupling the cavity and the channel; and

a groove extending from the cavity to an interior of a compression pocket formed between the first and second rotors and the housing.

10. The fluid machine according to claim 9, wherein the first lubricant passage further includes:

a counterbore formed at an interface between the housing and the compression pocket.

11. The fluid machine according to claim 5, wherein the first lubricant passage includes:

a groove extending from the oil groove to an interior of a compression pocket formed between the first and second rotors and the housing.

12. The fluid machine according to claim 5, wherein said second rotor further comprises:

a second shaft supported by the housing; and

a working portion rotatable relative to the second shaft, wherein the second shaft and the working portion define the dynamic interface associated with the second rotor.

13. The fluid machine according to claim 12, wherein the second lubricant passage further includes:

a first passage extending axially through at least a portion of the second shaft;

a second channel formed in an outer periphery of the second shaft; and

at least one radial bore coupling the first channel and the second channel.

14. The fluid machine of claim 13, wherein the second passage extends axially such that a first end of the second passage is fluidly coupled to a first portion of the housing and an opposite second end of the second passage is fluidly coupled to a second portion of the housing.

15. The fluid machine of claim 1, wherein a counterbore is formed in the housing where at least one of the first and second lubricant passages enters a compression pocket formed between the first and second rotors.

16. The fluid machine of claim 15, further comprising a recess formed in the housing in fluid communication with the counterbore, the recess disposed at an angle toward an interface between the first rotor and the second rotor.

17. The fluid machine of claim 16, wherein at least one of an angle, a length, a width, and a depth of the groove is optimized to control lubricant flow to the compression pocket.

18. A method of lubricating one or more dynamic interfaces of a fluid machine, comprising:

supplying lubricant from an oil sump via a first lubricant channel to a dynamic interface associated with a first rotor of the fluid machine; and

supplying lubricant from an oil sump to a dynamic interface associated with a second rotor of the fluid machine via a second lubricant passage, the second lubricant passage being different from the first lubricant passage;

wherein the supplying of 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 generated within the fluid machine during operation of the fluid machine.

19. The method of claim 18, wherein supplying lubricant from the oil sump to the dynamic interface associated with the first rotor and supplying lubricant from the oil sump to the dynamic interface associated with the second rotor occur simultaneously.

20. The method of claim 18, wherein supplying lubricant from the oil sump to the dynamic interface associated with the first rotor and supplying lubricant from the oil sump to the dynamic interface associated with the second rotor occurs without a pump or a control valve.

21. The method of claim 18, wherein supplying lubricant from an oil sump to a dynamic interface associated with the first rotor further comprises:

supplying lubricant to a first bearing surface via a first passage extending through an opening formed in a first shaft of the first rotor; and

lubricant is supplied to the second bearing surface via the second channel.

22. The method of claim 18, further comprising supplying lubricant from a dynamic interface associated with a first rotor and a dynamic interface associated with a second rotor to a compression pocket formed between the first rotor and the second rotor.