Pumping seals for rotary machinery

Abstract

The rotary machine includes a rotating shaft, a housing surrounding a portion of the rotating shaft and having an initial pressure therein, and a gas seal that exhausts gas to the outside of the housing, thereby reducing the pressure within the housing to an operating pressure that is less than the initial pressure.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Exemplary embodiments relate to the art of rotary machines, and more particularly, to rotary machines that include pumping seals. [Background technology]

[0002] An electric machine includes a stator having a stator winding attached to a housing, and a rotor including a rotor winding that rotates relative to the stator. The stator winding may be excited to impart a rotational force to the rotor, and the rotation of the rotor may induce a current in the stator winding. In a first mode of operation, current flows into the stator winding, and in a second mode of operation, current flows out of the stator winding.

[0003] In either mode, the rotor rotates relative to the stator. The rotor may contain either magnets or coils, depending on the type of electric machine. Summary of the Invention [Problem to be solved by the invention]

[0004] Exemplary embodiments relate to rotary machines, particularly any machine in which a shaft can rotate within a sealed enclosure that includes a pumping seal. The sealed enclosure contains the shaft within a volume of gaseous environment. The gaseous environment may be, but is not necessarily, atmospheric. The pumping seal removes gas from the volume of gas, thereby reducing the pressure. The reduced pressure reduces heat (wasted energy) generated by the rotation of the shaft and the agitation of the gas. [Means for solving the problem]

[0005] In one embodiment, a rotary machine is disclosed that includes a rotating shaft, a housing surrounding a portion of the rotating shaft, and a gas seal that vents gas from the housing to reduce pressure within the housing to an operating pressure that is lower than an initial pressure.

[0006] In any embodiment herein, the gas seal is capable of evacuating gas from the housing such that the pressure within the housing is less than atmospheric pressure.

[0007] In any important embodiment, the pressure within the enclosure may be reduced to less than half atmospheric pressure - less than 0.5 bar absolute.

[0008] In any important embodiment, the rotating shaft may be the rotor of a motor or may include two parts coupled together by a coupling member, which, if used, may be present within the housing.

[0009] In any important embodiment, the housing may have bleed holes formed therein to allow gas to be drawn into the housing.

[0010] In any important embodiment, the machine may include a valve that controls the flow of gas into the housing based on the pressure within the housing.

[0011] In any important embodiment, the dry gas seal may include a mating ring and a base ring that may be coupled to the rotatable shaft for rotation therewith or may be part of the rotatable shaft.

[0012] In some cases, the machine may optionally include a biasing member that biases the base ring towards the mating ring.

[0013] In any important embodiment, the machine may include a sleeve ring coupled to the rotating shaft and carrying the mating ring.

[0014] Also disclosed is a method of operating a rotary machine, which may be any machine disclosed or referenced herein, including a rotatable shaft and a housing surrounding a portion of the rotatable shaft, the method including sealing the shaft within the housing with a dry gas seal, establishing an initial pressure within the housing, and evacuating gas from the housing at the dry gas seal such that pressure within the housing is reduced from the initial pressure to a lower pressure.

[0015] In any important method, the initial pressure may be atmospheric pressure and the lower pressure may be less than 1 / 2 atmospheric pressure, e.g., less than 0.5 bar absolute. In some embodiments, the initial pressure may be greater than the external environmental pressure and the lower pressure is less than the initial pressure.

[0016] In any important manner, the rotating shaft is the rotor of a motor.

[0017] In any important manner, the rotating shaft comprises two parts joined together by a joining member which may optionally be present within the housing.

[0018] In any method of interest, the housing may have an air bleed hole formed therein, and the method may also include recharging gas within the housing by drawing gas into the housing through the air bleed hole.

[0019] The method may also include a step of having a machine and a valve controlling the flow of gas into the enclosure, and allowing gas to flow into the enclosure through the valve based on pressure within the enclosure.

[0020] Further technical features and advantages are realized by the techniques of the present invention. Embodiments and aspects of the present invention are described in detail herein and are considered part of the claimed subject matter. For a better understanding, please refer to the detailed description and drawings. [Brief description of the drawings]

[0021] The particular subject matter of the exclusive rights set forth herein is particularly pointed out and distinctly claimed in the claims at the end of the specification. The foregoing and other features and advantages of embodiments of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] 1 is a cross-sectional view of a rotary machine including a pumping dry gas seal; [Diagram 2] 5A-5D illustrate various types of surfaces that can be utilized within a dry gas seal for use as a pump for a rotary machine. [Diagram 3] 1 is a cross-sectional view of a rotary machine including a pumping dry gas seal and a valve for returning gas into a chamber of the machine. [Figure 4] FIG. 1 is a cross-sectional view of a rotary machine including a pumping dry gas seal and a bleed hole for filling or returning gas into a chamber of the machine. [Diagram 5] FIG. 2 is a cross-sectional view of an example seal that may be used in some embodiments, illustrating the gas path through the seal. [Figure 6] 1 shows a machine including a chamber having two shafts connected by a connecting member.

[0022] The figures depicted herein are exemplary. There may be many variations in the figures or the operations described therein without departing from the spirit of the invention. For example, operations may be performed in a different order, operations may be added, deleted, or modified. Additionally, the term "coupled" and variations thereof refer to having a connection path between two elements, and do not imply a direct connection between the two elements without an intervening element / connector between the elements. All of these variations are considered part of this specification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A detailed description of one or more embodiments of the disclosed apparatus and method is illustrated by way of example and not by way of limitation with reference to the figures.

[0024] Various embodiments of the present invention are described herein with reference to the associated drawings. Alternative embodiments of the present invention are contemplated without departing from the scope of the present invention. Various connections and relationships (e.g., above, below, adjacent, etc.) are defined between elements in the following description and drawings. These connections and / or relationships may be direct or indirect unless otherwise specified, and the present invention is not intended to be limited in this respect. Thus, coupling of entities may refer to either direct coupling or indirect coupling, and relationships between entities may be direct or indirect. Additionally, various tasks and process steps described herein may be combined into a more comprehensive procedure or process having additional steps or functions not described in detail herein.

[0025] Turning now to an overview of the technology more specifically related to aspects of the present invention, it should first be understood that the teachings herein are applicable to all machines that include a rotating shaft (e.g., a rotor). Examples include electric motors, electric generators, flywheels, kinetic energy recovery systems (KERS), energy storage systems, gas turbines, wind turbines, steam turbines, and coupling members. In certain embodiments, at least a portion of the rotating shaft is enclosed in a sealed chamber.

[0026] The present inventors have recognized that such rotating shafts generate heat due to the stirring of the gaseous environment within the enclosed chamber. This heat represents energy lost from the system, resulting in inefficiencies. Given the number of rotating shafts in the world, having a simple technique that can limit this heat generation would result in significant energy savings, with the potential benefits of reduced costs and reduced emissions.

[0027] Recognizing this problem, embodiments herein relate to systems and methods that can reduce heat generation due to agitation. In a basic form, this can be accomplished by reducing the pressure of the gas in the enclosed chamber in which the rotor rotates. The chamber is sealed by a dry gas seal. By dry gas seal, it is preferably meant a gas seal (i.e., that prevents the passage of gas from one area to another), such as a contactless mechanical gas seal. It will be understood that substances contained in the gas, such as vapors or aerosols, may also be present in some cases. The dry gas seal may be utilized to evacuate the gas from the chamber, reducing agitation and associated heat in the chamber. The pressure in the chamber may be reduced to below atmospheric pressure in the operating area. In one embodiment, it is reduced to less than 1 / 2 atmospheric pressure, i.e., less than 0.5 bar absolute.

[0028] 1 illustrates an example of a rotating machine 1. The illustrated machine 1 may be a motor or generator, a vibration damper, an alternator, a pump, a compressor, or a turbine, although those skilled in the art will appreciate that the teachings herein are not so limited and may be applied to any machine having a rotating shaft.

[0029] Machine 1 includes a rotating shaft 2 (e.g., rotor) enclosed within a chamber 3. Chamber 3 is shown as having a single opening 4 through which shaft 2 passes as it exits chamber 3 via opening 9. Those skilled in the art will appreciate that the chamber may have multiple openings to accommodate situations where both ends of the shaft extend beyond chamber 3. This may occur with motor / generators as well as with coupling members that are within an enclosed chamber, to name just a few non-limiting examples.

[0030] The chamber 3 is defined by a housing 5, which in one embodiment may be the housing of a motor or turbine. As shown, within the housing 3 is a member 6 connected to the shaft 2. The member may be a rotor winding, a rotor magnet, a coupling member, a flywheel, a gear, etc. Of course, other examples are possible.

[0031] The opening 9 is at least partially or completely filled by a dry gas seal 4, which serves to evacuate the gas from the chamber 3 at a controlled rate. The path that the gas takes is generally indicated by the arrows labeled "flow."

[0032] One or more bearings 7a, 7b may be provided within the housing 5 to support the rotating shaft. The first bearing 7a is shown as being on the outside of the seal 4 (direction A), although the exact configuration may vary. As shown, the flow is from the outside of the seal 4 radially inward towards the shaft (direction B). Those skilled in the art will appreciate that the direction may be reversed. The direction is determined by a number of factors, including the orientation of the grooves.

[0033] Typically, dry gas seals, such as seal 4 shown in Figure 1, work by providing a seal between a rotating ring and a fixed ring. The rotating ring is sometimes called the "mating ring" because it is fitted to the rotating shaft / rotor. The rotating ring may be fitted to the rotor via a shaft sleeve. The fixed ring is sometimes called the base ring and does not rotate during operation.

[0034] During operation, a layer of gas forms between the two rings that may form a seal or restrict flow, while allowing the two rings to move relative to each other without contacting each other. A groove in the rotating (mating) ring draws gas from the radial end of the mating ring to a position between the two rings. The gas drawn into the groove is compressed as it moves toward the radially inner end (or tip) of the groove. The compressed gas forms a pressure dam that "peels" the base ring from the mating ring, creating a continuous gap in the range of a few microns (e.g., 3-10 μm). To allow relative axial movement between the rings, the base ring is usually attached to the fixed part of the dry gas seal by a compression member, such as a spring.

[0035] In the following examples, a dry gas seal is shown as a perfect seal. However, one skilled in the art will appreciate that the teachings herein are applicable to any type of device that utilizes pumping action due to the relative rotation of two rings. An example would be a nanomachine with very small axial motion, eliminating the need for springs or other biasing members. Also contemplated are devices that include elastomeric parts that bias, for example, a non-rotating ring towards a rotating ring.

[0036] After peeling, a controlled amount of gas is allowed to flow (e.g., pumped or otherwise made movable) across the dam area to the low pressure side of the seal (e.g., outside the sealed chamber), creating a controlled seal leak, with the ring acting on a thin film of gas as a contactless seal. The controlled leak can be used to evacuate gas from the sealed chamber and reduce pressure in the chamber, which can reduce heat in some embodiments. Referring to FIG. 1, the gas pumping is shown by the arrow labeled "flow."

[0037] Either the sealing ring or the mating ring includes a surface texture pattern to allow for contactless operation by drawing gas between the rings and causing separation, or lift-off, between the rings. A specifically illustrated surface texture pattern is a groove, but this is not meant to be limiting and any type of surface pattern can be used as long as it supports the separation or lift-off described above and subsequent pumping of gas from chamber 3.

[0038] 2a shows an example of a generic sealing surface 200, which may be the sealing surface of either the seal ring or the mating ring (114, 116). The surface texture pattern / grooves 202 on this surface 200 are unidirectional and extend from the outer diameter OD to the inner diameter ID.

[0039] 2b shows another example of a generic sealing surface 204, which can be the sealing surface of either the seal ring or the mating ring (114, 116). The surface texture pattern / grooves 206 on this surface 204 is also unidirectional, running from the inner diameter ID to the outer diameter OD.

[0040] 2c shows another example of a generic sealing surface 208, which can be the sealing surface of either the seal ring or the mating ring (114, 116). The surface texture features / grooves 202 on this surface 208 are bidirectional, extending from the outer diameter OD to the inner diameter ID.

[0041] 2d shows another example of a generic sealing surface 220, which may be the sealing surface of either the seal ring or the mating ring (114, 116). The surface texture 230 of this sealing surface 220 is bidirectional and extends from the inner diameter ID to the outer diameter OD.

[0042]

[0048] In any of these examples, when the gas enters the surface texture features / grooves it is compressed as the faces rotate relative to one another creating a peeling force that separates the faces. In any of the above examples, the surface texture patterns / grooves can have any depth based on the desired flow.

[0043] During operation, the seal 4 can serve to reduce the pressure in the chamber 3. This process, or pumping, can, in one embodiment, reduce the pressure in the chamber to a level lower than the ambient pressure surrounding the chamber. In certain embodiments, the seal can be positioned to allow gas to evacuate the chamber until it approaches a vacuum, i.e., to reduce the gas density for mixing. As shown at the bottom of FIG. 3, at near vacuum pressures, the relief valve 301 can open or the seal can be designed to open to return to atmospheric pressure to refill the chamber 3 to begin the process again. Alternatively, as shown in FIG. 4, a small bleed hole 401 (or any other form of refill facility) can allow the system to be in a continuous near vacuum state. In this or other embodiments, the gas seal can be opened at counter pressure for refilling.

[0044] In another embodiment, the gas seal evacuates gas from the housing to reduce the pressure in the housing to an operating pressure that is lower than the initial pressure in the housing, which may be defined as the pressure after sealing the shaft in the housing and before evacuating gas from the housing with the dry gas seal.

[0045] In any configuration, reducing the pressure reduces or eliminates the gaseous medium for agitation and heat generation. For example, the gas may be at half the initial pressure or less. Additionally, a near vacuum can establish a thermal barrier that prevents heat transfer and high temperatures. Of course, the extent to which the pressure is reduced can be affected by the initial pressure, with higher initial pressures generally reducing it more than lower pressures on a percentage basis.

[0046] While not fully shown herein for simplicity, examples of dry gas seals that may be used include those disclosed in PCT Application PCT / US21 / 25126 and U.S. Patent Application Serial No. 16 / 992,296, filed August 13, 2020, both of which are incorporated by reference in their entireties. Of course, not all of the seals or parts of the seals shown in FIG. 5 below are required, and only two rings as described above may be required. In particular, labyrinth seals and split seals may not be required.

[0047] 5 is a partial cross-sectional view of a single non-contact dry gas seal assembly 100 (abbreviated as dry gas seal assembly). This assembly may be used as the seal 4 shown in any of the important embodiments. However, the teachings herein may be applied to other dry gas seal configurations. As will be understood from reading the detailed description, the teachings herein may be applied to any type of dry gas seal, including but not limited to single dry gas seal, tandem dry gas seal, tandem dry gas seal with intermediate labyrinth, triple dry gas seal with or without labyrinth, and dual opposed dry gas seal.

[0048] At least a portion of the dry gas seal assembly 100 is disposed between the rotating shaft 2 and the housing 5. The mating ring is formed as part of the shaft 2 or is attached to the shaft 2.

[0049] The rotating shaft may be part of any rotating machine, and may in fact be a shaft formed from two parts (2a and 2b) coupled together by a coupling member 2c (see FIG. 6) housed in a chamber 3 defined by a housing 5. As mentioned above, the shaft 2 may be supported by the housing 5 via bearings (not shown) located in bearing cavities 108 of the housing 5. The stator may also be part of the housing rather than including its own retaining member.

[0050] The housing 5 includes a hole 109 formed therein that extends between the chamber 3 and the bearing cavity 108 and defines an annular sealed chamber 112 into which the dry gas seal assembly 100 can be inserted. This chamber contains the gas that is evacuated by the seal 4.

[0051] An optional shroud 126 may include a labyrinth seal and extends over a radially extending opening formed between the rotating shaft 2 and the housing 5. The optional shroud 126 may be provided to inhibit the free flow of gas from the chamber 3 into the bore 109. The shroud 126 is disposed within the bore 109 and carries a labyrinth seal 128 as shown that serves to totally or partially prevent the free flow of process gas from the process cavity 106 into the bore 109.

[0052] The labyrinth seal 128 includes a plurality of ridges 134 at its radially inner end. During operation, the ridges 134 are disposed near an outer surface 136 of the rotatable shaft 102. The plurality of ridges 134 and the corresponding intermediate cavities formed between any two consecutive ridges 134 prevent ingress of gas from the process cavity 106 through the rotatable shaft 2 into the sealed chamber 112.

[0053] The dry gas seal assembly 100 shown in Figure 5 includes a single dry gas seal, generally referred to as the first seal 110. Typically, the components of the first seal 110 are preassembled into a cartridge that is then placed into the sealed chamber 112. The cartridge 118 includes a stator 117 that may be formed of one or more parts and joined in a fixed relationship to one another, as well as the compressor housing 104, during installation. As shown, the stator 117 includes a retaining ring 117a that may be sealed to the chamber 3 by a sealing member, such as a radial seal 140.

[0054] The cartridge 118 may also include a sleeve ring 115, which may be formed of one or more parts and attached to the rotating shaft 2 for rotation therewith. However, in one embodiment, the cartridge may be omitted. For example, the mating ring may be part of the shaft and the base ring may be integrated into the housing.

[0055] The illustrated sleeve ring 115 includes two portions 115a, 115b in Figure 5. In particular, the sleeve 115 includes a rotatable ring 115a that is configured to rotate in contact with the rotatable shaft 2. In the illustrated embodiment, a spacer sleeve 115b is included as part of the sleeve 115. Of course, the sleeve ring 115 may be formed as a unitary piece or may include any number of pieces that are joined together or otherwise held stationary relative to one another during operation (e.g., all of the pieces rotate together as a unit).

[0056] The illustrated cartridge 118 also includes what is referred to as an isolation seal 119. Of course, the isolation seal 119 is not generally required to be part of the dry gas seal, but may be a separate member joined to the dry gas seal. The isolation seal may serve to prevent or reduce the ingress of oil or other lubricant from a bearing (not shown) disposed within the bearing cavity 108 into the first seal 110. The isolation seal 119 may also prevent or reduce the ingress of contaminants from the outside environment. Contaminants may include, for example, one or a combination of dirt, debris, or other undesirable particles or liquids.

[0057] It will be understood that the split seal 119 is not required in certain embodiments; that is, embodiments herein do not require a split seal as part of the cartridge 118. Additionally, as shown in one or more of the embodiments below, the split seal 119, if present, need not be adjacent to the first seal 110, and one or more other seals may be provided between the first seal 110 and the split seal 119.

[0058] [Axial movement of sleeve ring 115 relative to rotatable shaft 102 is limited by shaft thrust ring 125 received in a groove in rotatable shaft 102. Axial movement of stator 117 is limited by stator thrust ring 121 received in a groove in housing 5.

[0059] It should be understood that in the above embodiment, the shaft thrust ring 125 may be fixed relative to the sleeve ring 115 so that the two members rotate together. It should also be understood that for completeness, other members may be attached to the sleeve ring 115 to provide support or other functions, but are not specifically described herein. One optional example is a mating ring position fixing element 115c.

[0060] The sleeve ring 115 carries or otherwise mates with the rotating or mating ring 114 on the rotating shaft 102. That is, the sleeve ring 115 mates with the rotating shaft 102 such that the mating ring 114 also rotates with the shaft 102. The mating ring 114 may include one or more grooves (not shown) formed in its surface. Examples of such grooves are shown above in FIG. 2.

[0061] The base ring 116 may also be referred to as a stationary ring, since it does not rotate with the shaft and is therefore generally or completely rotationally stationary relative to the housing during operation. Reference numeral 113 indicates the location of the sealing interface formed between the mating ring 114 and the base ring 116.

[0062] As will be appreciated by those skilled in the art, the base ring 116 is axially movable relative to the housing 104 during operation so that a controlled distance may be maintained between the mating ring 114 and the base ring 116 at the sealing interface 113. In the illustrated embodiment, a spring force is applied to the base ring 116 by one or more biasing members 138 disposed between the retaining ring 117a and the base ring 116.

[0063] During operation, gas is present in chamber 3. The gas is present in the so-called sealed chamber 112 and its path through the seal is indicated by arrow 150.

[0064] Rotation of the mating ring 114 by coupling with the rotating shaft 102 draws a portion of the gas in the sealing chamber 112 from the outer diameter of the mating ring 114 into a groove formed therein. The shape of the groove is optimized to enhance sealing performance. The groove is shaped with an end such that the gas entering the groove is compressed due to the reduced volume at the end. The area of ​​slightly higher gas pressure forms a pressure dam, resulting in a so-called "lift-off" (peeling), resulting in a physical separation of the base ring 116 and the mating ring 114. Thus, during operation, gas flows over the dam area (between the base ring and the mating ring 114) to the downstream side 160 of the sealing interface 113. Gas that has passed through the sealing interface can exit the dry gas seal assembly 100 via a vent 174 in the housing 5 or by other means.

[0065] To enable the above-mentioned lift-off, a carrier ring 170 is provided as a means to enable the necessary movement. The carrier ring 170 is coupled to the retaining ring 117a by a biasing member 138. The biasing member 138 may be a single member or may be comprised of multiple members. The biasing member 138, in one embodiment, includes one or more springs.

[0066] The biasing member 138 can enable the base ring 116 to maintain a constant distance between itself and the mating ring 114 during operation, even if such movement of the rotatable shaft 102 causes the mating ring 114 to move axially.

[0067] To prevent uncontrolled movement of gas around the sealing interface 113, one or more radial seals may be provided. The seals may be made of a polymer or elastomer, one example of such a seal is a lip seal. In FIG. 5, the seals are illustrated as lip seals, but this is by way of example only and not by way of limitation. As shown, a first seal 172 may be provided between the retaining ring 117a and the carrier ring 170. The first seal 172 is fixed relative to the retaining ring 117a in one embodiment. The first seal 172 may be arranged such that the sealing gas follows the path 150 and expands when the gas impinges. This makes the first seal 172 a so-called contact seal. When the base ring 116 moves (either by lift-off or shaft movement), the carrier ring 170 moves relative to the first seal 172. A seal may also be provided between the base ring 116 and the carrier ring 170, preferably made of a polymer or elastomer.

[0068] The term "about" is intended to include the degree of error associated with measuring the particular amount based on the equipment available at the time of application.

[0069] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that as used herein, the terms "comprising" and / or "having" specify the presence of stated features, integers, steps, operations, members, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, members, components, and / or groups thereof.

[0070] Although the present disclosure has been described with reference to exemplary embodiments or embodiments, those skilled in the art will recognize that various modifications can be made and equivalents can be substituted for the elements without departing from the scope of the present disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope of the present disclosure. Therefore, the present disclosure is not limited to the particular embodiment disclosed as the best mode contemplated for carrying out the disclosure, but the present disclosure is intended to include all embodiments falling within the scope of the claims.

Claims

1. A rotating shaft; a housing surrounding a portion of the rotating shaft; a gas sealing portion configured to exhaust gas to the outside of the housing so that the pressure inside the housing is less than atmospheric pressure; A rotating machine comprising:

2. 10. The rotary machine of claim 1, wherein the pressure within the housing is less than atmospheric pressure.

3. 3. The rotary machine of claim 2, wherein the rotating shaft is a rotor of a motor.

4. 4. The rotary machine of claim 3, wherein the rotating shaft has two portions joined together by a connecting member.

5. The rotary machine of claim 4 , wherein the coupling member is present within the housing.

6. 6. The rotary machine of claim 5, wherein the housing has bleed holes formed therein to allow gas to be drawn into the housing.

7. The rotary machine of claim 6 , comprising a valve configured to control the flow of gas into the housing based on the pressure within the housing.

8. 8. A rotary machine according to claim 7, The gas sealing portion is a mating ring coupleable with the rotatable shaft for rotation therewith; Basic ring, A rotating machine having

9. The rotary machine of claim 8 , further comprising a biasing member configured to bias the base ring toward the mating ring.

10. The rotary machine of claim 8 , further comprising a sleeve ring coupled to the rotating shaft and carrying the mating ring.

11. 1. A method of operating a rotary machine having a rotating shaft and a housing surrounding a portion of the rotating shaft, comprising: sealing the shaft within the housing with a dry gas seal; setting an initial pressure within the enclosure; venting gas out of the enclosure through the dry gas seal such that pressure within the enclosure is reduced from the initial pressure to a lower pressure; A method having the following.

12. 12. The method of claim 11, wherein the initial pressure is atmospheric pressure and the lower pressure is less than atmospheric pressure.

13. 13. The method of claim 12, wherein the rotating shaft is a rotor of a motor.

14. 14. The method of claim 13, wherein the rotating shaft has two portions joined together by a connecting member.

15. The method of claim 14 , wherein the coupling member is within the housing.

16. 16. The method of claim 15, wherein the housing has a bleed hole formed therein, and further comprising refilling the housing with gas by drawing gas into the housing through the bleed hole.

17. 17. The method of claim 16, wherein the rotary machine includes a valve controlling gas flow into the housing, the method further comprising allowing gas to flow into the housing through the valve based on the pressure within the housing.

18. A rotating shaft; a housing surrounding a portion of the rotating shaft and having an initial pressure therein; a gas seal that exhausts gas to the exterior of the housing, thereby reducing the pressure within the housing to an operating pressure that is less than the initial pressure; A rotating machine comprising:

19. A rotary machine according to claim 18, further defined in any one of claims 2 to 10.

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