[0001] This invention was made with government support under Government Contract No. DOE-DE-FE0000493 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

[0002] This application claims the benefit of U.S. Provisional Patent Application having Serial No. 62/139,042, which was filed March 27, 2015 and U .S. Utility Patent Application having Serial No. 15/072,818, which was filed March 17, 2016. The aforementioned patent applications are hereby incorporated by reference in their entirety into the present application to the extent consistent with the present application.

[0003] Compressors and systems incorporating compressors have been developed and are often utilized in a myriad of industrial processes (e.g. , petroleum refineries, offshore oil production platforms, and subsea process control systems). Conventional compressors may be configured to compress a process fluid by applying kinetic energy to the process fluid to transport the process fluid from a low pressure environment to a high pressure environment. The compressed process fluid discharged from the compressors may be utilized to efficiently perform work or operate one or more downstream processes. Improvements in the efficiency of conventional compressors has increased the application of the compressors at various oil production sites. Many of the oil production sites (e.g. , offshore), however, may be constrained or limited in space. Accordingly, there is an increased interest and demand for smaller and lighter compressors, or compact compressors. In addition to the foregoing, it is often desirable that the compact compressors be capable of achieving higher compression ratios (e.g., 10:1 or greater) for increased production while maintaining a compact footprint.

[0004] As the compression ratios of the compact compressors increase, the heat generated through compression may also correspondingly increase. Improper management of the increased heat of compression may adversely affect the reliability and/or performance of the compact compressors. For example, one or more components (e.g. , seals) of the compact compressors may be at least partially fabricated from a material (e.g. , an elastomer) that may not be capable of operating at relatively high temperatures (e.g. , greater than about 380°F/193°C) for extended periods of time. Accordingly, the increased heat generated via compression may often limit or reduce the operational lifetimes of the components. In another example, the components (e.g. , impellers) of the compact compressors may not have the metallurgical properties (e.g., strength and/or fatigue life) to operate unless the respective temperatures thereof are maintained at or below design temperatures. [0005] In view of the foregoing , skilled artisans have attempted to manage and/or counteract the heat of compression by utilizing a heat transfer medium or a cooling fluid . For example, the cooling fluid may often be circulated through one or more portions of conventional compact compressors to cool the components of the compact compressors. The circulation of the cooling fluid, however, may not sufficiently manage the heat generated in compact compressors having relatively higher compression ratios (e.g. , about 10: 1 or greater).

[0006] What is needed, then, is a balance piston with a sealing member for managing heat generated in a compact compressor having a relatively high compression ratio.

[0007] Embodiments of the disclosure may provide a balance piston for a compressor. The balance piston may include an annular body and a seal extending from an axial surface of the annular body. The annular body may be configured to be disposed about and coupled with a rotary shaft of the compressor. The seal may be configured to form a sealing engagement with at least one component of the compressor to prevent a flow of a process fluid from an impeller of the compressor to a seal cavity of the compressor.

[0008] Embodiments of the disclosure may also provide a compressor configured to provide a compression ratio of at least about 8:1 . The compressor may include a casing and a rotary shaft disposed in the casing and configured to be driven by a driver. The compressor may also include a shaft seal assembly disposed radially outward from the rotary shaft and at least partially defining a seal cavity, and an impeller coupled with the rotary shaft and configured to receive a process fluid and discharge the process fluid at an absolute Mach number of about 1 .0 or greater. The compressor may further include a balance piston integral with the impeller, and a balance piston seal disposed radially outward from the balance piston such that the balance piston seal and the balance piston define a radial clearance therebetween. The compressor may also include a protrusion coupled or integral with the balance piston. The protrusion may be configured to prevent a flow of a process fluid from the radial clearance to the seal cavity.

[0009] Embodiments of the disclosure may provide a compression system including a driver and a compressor coupled with the driver via a drive shaft and configured to provide a compression ratio of at least about 8: 1 . The compressor may include a casing and an inlet coupled or integral with the casing . The inlet and the casing may at least partially define a fluid pathway of the compressor configured to receive a process fluid. The compressor may also include a rotary shaft disposed in the casing and coupled with the driver via the drive shaft. The rotary shaft may be configured to be rotated by the driver via the drive shaft. The compressor may further include a shaft seal assembly disposed radially outward from the rotary shaft and at least partially defining a seal cavity. An impeller may be coupled with the rotary shaft and configured to receive the process fluid and discharge the process fluid at an absolute Mach number of about one or greater. The compressor may also include a balance piston integral with the impeller and a balance piston seal disposed radially outward from the balance piston such that the balance piston seal and the balance piston define a radial clearance therebetween. A protrusion may be coupled or integral with the balance piston and configured to prevent a flow of the process fluid from the radial clearance to the seal cavity.

[0010] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0011] Figure 1 illustrates a schematic view of an exemplary compression system including a compressor, according to one or more embodiments disclosed.

[0012] Figure 2A illustrates a partial, cross-sectional view of an exemplary compressor that may be included in the compression system of Figure 1 , according to one or more embodiments disclosed.

[0013] Figure 2B illustrates an enlarged view of the portion of the compressor indicated by the box labeled 2B of Figure 2A, according to one or more embodiments disclosed.

[0014] Figure 2C illustrates an enlarged view of the portion of the compressor indicated by the box labeled 2C of Figure 2B, according to one or more embodiments disclosed.

[0015] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0016] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Further, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0017] Figure 1 illustrates a schematic view of an exemplary compression system 100, according to one or more embodiments. The compression system 100 may include, amongst other components, one or more compressors 102 (one is shown), a driver 104, and a drive shaft 106 configured to operatively couple the compressor 102 with the driver 104. The compression system 100 may be configured to compress or pressurize a process fluid. For example, as further described herein, the driver 104 may be configured to drive the compressor 102 via the drive shaft 106 to compress the process fluid. In an exemplary embodiment, the compression system 100 may have a compression ratio of at least about 6:1 or greater. For example, the compression system 100 may compress the process fluid to a compression ratio of about 6:1 , about 6.1 :1 , about 6.2:1 , about 6.3:1 , about 6.4:1 , about 6.5:1 , about 6.6:1 , about 6.7:1 , about 6.8:1 , about 6.9:1 , about 7:1 , about 7.1 :1 , about 7.2:1 , about 7.3:1 , about 7.4:1 , about 7.5:1 , about 7.6:1 , about 7.7:1 , about 7.8:1 , about 7.9:1 , about 8:1 , about 8.1 :1 , about 8.2:1 , about 8.3:1 , about 8.4:1 , about 8.5:1 , about 8.6:1 , about 8.7:1 , about 8.8:1 , about 8.9:1 , about 9:1 , about 9.1 :1 , about 9.2:1 , about 9.3:1 , about 9.4:1 , about 9.5:1 , about 9.6:1 , about 9.7:1 , about 9.8:1 , about 9.9:1 , about 10:1 , about 10.1 :1 , about 10.2:1 , about 10.3:1 , about 10.4:1 , about 10.5:1 , about 10.6:1 , about 10.7:1 , about 10.8:1 , about 10.9:1 , about 1 1 :1 , about 1 1 .1 :1 , about 1 1 .2:1 , about 1 1 .3:1 , about 1 1 .4:1 , about 1 1 .5:1 , about 1 1 .6:1 , about 1 1 .7:1 , about 1 1 .8:1 , about 1 1 .9:1 , about 12:1 , about 12.1 :1 , about 12.2:1 , about 12.3:1 , about 12.4:1 , about 12.5:1 , about 12.6:1, about 12.7:1, about 12.8:1, about 12.9:1, about 13:1, about 13.1:1, about 13.2:1, about 13.3:1, about 13.4:1, about 13.5:1, about 13.6:1, about 13.7:1, about 13.8:1, about 13.9:1, about 14:1 , or greater.

[0018] The compressor 102 may be a direct-inlet centrifugal compressor. The direct-inlet centrifugal compressor may be, for example, a version of a Dresser-Rand Pipeline Direct Inlet (PDI) centrifugal compressor manufactured by the Dresser-Rand Company of Olean, New York. The compressor 102 may have a center-hung rotor configuration or an overhung rotor configuration, as illustrated in Figure 1. In an exemplary embodiment, the compressor 102 may be an axial-inlet centrifugal compressor. In another embodiment, the compressor 102 may be a radial-inlet centrifugal compressor. As previously discussed, the compression system 100 may include one or more compressors 102. For example, the compression system 100 may include a plurality of compressors (not shown). In another example, illustrated in Figure 1, the compression system 100 may include a single compressor 102. The compressor 102 may be a supersonic compressor or a subsonic compressor. In at least one embodiment, the compression system 100 may include a plurality of compressors (not shown), and at least one compressor of the plurality of compressors is a subsonic compressor. In another embodiment, illustrated in Figure 1, the compression system 100 includes a single compressor 102, and the single compressor 102 is a supersonic compressor.

[0019] The compressor 102 may include one or more stages (not shown). In at least one embodiment, the compressor 102 may be a single-stage compressor. In another embodiment, the compressor 102 may be a multi-stage centrifugal compressor. Each stage (not shown) of the compressor 102 may be a subsonic compressor stage or a supersonic compressor stage. In an exemplary embodiment, the compressor 102 may include a single supersonic compressor stage. In another embodiment, the compressor 102 may include a plurality of subsonic compressor stages. In yet another embodiment, the compressor 102 may include a subsonic compressor stage and a supersonic compressor stage. Any one or more stages of the compressor 102 may have a compression ratio greater than about 1:1. For example, anyone or more stages of the compressor 102 may have a compression ratio of about 1.1:1, about 1.2:1, about 1.3:1, about 1.4:1, about 1.5:1, about 1.6:1, about 1.7:1, about 1.8:1, about 1.9:1, about 2:1, about 2.1:1, about 2.2:1, about 2.3:1, about 2.4:1, about 2.5:1, about 2.6:1, about 2.7:1, about 2.8:1, about 2.9:1, about 3:1, about 3.1:1, about 3.2:1, about 3.3:1, about 3.4:1, about 3.5:1, about 3.6:1, about 3.7:1, about 3.8:1, about 3.9:1, about 4:1, about 4.1:1, about 4.2:1, about 4.3:1, about 4.4:1, about 4.5:1, about 4.6:1, about 4.7:1, about 4.8:1, about 4.9:1, about 5:1, about 5.1:1, about 5.2:1, about 5.3:1, about 5.4:1, about 5.5:1, about 5.6:1, about 5.7:1, about 5.8:1, about 5.9:1, about 6:1, about 6.1:1, about 6.2:1, about 6.3:1, about 6.4:1, about 6.5:1, about 6.6:1, about 6.7:1, about 6.8:1, about 6.9:1, about 7:1, about 7.1:1, about 7.2:1, about 7.3:1 , about 7.4:1 , about 7.5:1 , about 7.6:1 , about 7.7:1 , about 7.8:1 , about 7.9:1 , about 8.0:1 , about 8.1 :1 , about 8.2:1 , about 8.3:1 , about 8.4:1 , about 8.5:1 , about 8.6:1 , about 8.7:1 , about 8.8:1, about 8.9:1, about 9:1, about 9.1:1, about 9.2:1, about 9.3:1, about 9.4:1, about 9.5:1, about 9.6:1, about 9.7:1, about 9.8:1, about 9.9:1, about 10:1, about 10.1:1, about 10.2:1, about 10.3:1, about 10.4:1, about 10.5:1, about 10.6:1, about 10.7:1, about 10.8:1, about 10.9:1, about 11:1, about 11.1:1, about 11.2:1 , about 11.3:1 , about 11.4:1 , about 11.5:1, 113.6:1, about 11.7:1, about 11.8:1, about 11.9:1, about 12:1, about 12.1:1, about 12.2:1, about 12.3:1, about 12.4:1, about 12.5:1, about 12.6:1, about 12.7:1, about 12.8:1, about 12.9:1, about 13:1, about 13.1:1, about 13.2:1, about 13.3:1, about 13.4:1, about 13.5:1, about 13.6:1, about 13.7:1, about 13.8:1, about 13.9:1, about 14:1, or greater. In an exemplary embodiment, the compressor 102 may include a plurality of compressor stages, where a first stage (not shown) of the plurality of compressor stages may have a compression ratio of about 1.75:1 and a second stage (not shown) of the plurality of compressor stages may have a compression ratio of about 6.0:1.

[0020] The driver 104 may be configured to provide the drive shaft 106 with rotational energy. The drive shaft 106 may be integral or coupled with a rotary shaft 108 of the compressor 102 such that the rotational energy of the drive shaft 106 may be transmitted to the rotary shaft 108. The drive shaft 106 of the driver 104 may be coupled with the rotary shaft 108 via a gearbox (not shown) having a plurality of gears configured to transmit the rotational energy of the drive shaft 106 to the rotary shaft 108 of the compressor 102. Accordingly, the drive shaft 106 and the rotary shaft 108 may spin at the same speed, substantially similar speeds, or differing speeds and rotational directions via the gearbox. The driver 104 may be a motor, such as a permanent magnetic electric motor, and may include a stator (not shown) and a rotor (not shown). It should be appreciated, however, that other embodiments may employ other types of motors including, but not limited to, synchronous motors, induction motors, and brushed DC motors, or the like. The driver 104 may also be a hydraulic motor, an internal combustion engine, a steam turbine, a gas turbine, or any other device capable of driving or rotating the rotary shaft 108 of the compressor 102.

[0021] The compression system 100 may include one or more radial bearings 110 directly or indirectly supported by a housing 112 of the compression system 100. The radial bearings 110 may be configured to support the drive shaft 106 and/or the rotary shaft 108. The radial bearings 110 may be oil film bearings. The radial bearings 110 may also be magnetic bearings, such as active magnetic bearings, passive magnetic bearings, or the like. The compression system 100 may also include one or more axial thrust bearings 1 14 disposed adjacent the rotary shaft 108 and configured to control the axial movement of the rotary shaft 108. The axial thrust bearings 1 14 may be magnetic bearings configured to at least partially support and/or counter thrust loads or forces generated by the compressor 102.

[0022] The process fluid pressurized, circulated, contained, or otherwise utilized in the compression system 100 may be a fluid in a liquid phase, a gas phase, a supercritical state, a subcritical state, or any combination thereof. The process fluid may be a mixture, or process fluid mixture. The process fluid may include one or more high molecular weight process fluids, one or more low molecular weight process fluids, or any mixture or combination thereof. As used herein, the term "high molecular weight process fluids" refers to process fluids having a molecular weight of about 30 grams per mole (g/mol) or greater. Illustrative high molecular weight process fluids may include, but are not limited to, hydrocarbons, such as ethane, propane, butanes, pentanes, and hexanes. Illustrative high molecular weight process fluids may also include, but are not limited to, carbon dioxide (CO2) or process fluid mixtures containing carbon dioxide. As used herein, the term "low molecular weight process fluids" refers to process fluids having a molecular weight less than about 30 g/mol. Illustrative low molecular weight process fluids may include, but are not limited to, air, hydrogen, methane, or any combination or mixtures thereof.

[0023] In an exemplary embodiment, the process fluid or the process fluid mixture may be or include carbon dioxide. The amount of carbon dioxide in the process fluid or the process fluid mixture may be at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or greater by volume. Utilizing carbon dioxide as the process fluid or as a component or part of the process fluid mixture in the compression system 100 may provide one or more advantages. For example, carbon dioxide may provide a readily available, inexpensive, non-toxic, and nonflammable process fluid. In another example, the relatively high working pressure of applications utilizing carbon dioxide may allow the compression system 100 incorporating carbon dioxide (e.g. , as the process fluid or as part of the process fluid mixture) to be relatively more compact than compression systems incorporating other process fluids (e.g., process fluids not including carbon dioxide). Additionally, the high density and high heat capacity or volumetric heat capacity of carbon dioxide with respect to other process fluids may make carbon dioxide more "energy dense." Accordingly, a relative size of the compression system 100 and/or the components thereof may be reduced without reducing the performance of the compression system 100. [0024] The carbon dioxide may be of any particular type, source, purity, or grade. For example, industrial grade carbon dioxide may be utilized as the process fluid without departing from the scope of the disclosure. Further, as previously discussed, the process fluids may be a mixture, or process fluid mixture . The process fluid mixture may be selected for one or more desirable properties of the process fluid mixture within the compression system 100. For example , the process fluid mixture may include a mixture of a liquid absorbent and carbon dioxide (or a process fluid containing carbon dioxide) that may enable the process fluid mixture to be compressed to a relatively higher pressure with less energy input than compressing carbon dioxide (or a process fluid containing carbon dioxide) alone.

[0025] Figure 2A illustrates a partial, cross-sectional view of an exemplary compressor 200 that may be included in the compression system 100 of Figure 1 , according to one or more embodiments. Figure 2B illustrates an enlarged view of the portion of the compressor 200 indicated by the box labeled 2B of Figure 2A, according to one or more embodiments. As illustrated in Figure 2A, the compressor 200 may include a casing 202 and an inlet 204 (e.g., an axial inlet) . The casing 202 and the inlet 204 may at least partially define a fluid pathway of the compressor 200 through which the process fluid may flow. The fluid pathway may include an inlet passageway 206 configured to receive the process fluid , an impeller cavity 208 fluidly coupled with the inlet passageway 206, a diffuser 210 (e.g. , static diffuser) fluidly coupled with the impeller cavity 208, and a collector or volute 212 fluidly coupled with the diffuser 210. The casing 202 may be configured to support and/or protect one or more components of the compressor 200. The casing 202 may also be configured to contain the process fluid flowing through one or more portions or components of the compressor 200.

[0026] As illustrated in Figure 2A, the compressor 200 may include an inlet guide vane assembly 214 configured to condition a process fluid flowing through the inlet passageway 206 to achieve predetermined or desired fluid properties and/or fluid flow attributes. Such fluid properties and/or fluid flow attributes may include flow pattern (e.g. , swirl distribution), velocity, flow rate, pressure, temperature , and/or any suitable fluid property and fluid flow attribute to enable the compressor 200 to function as described herein. The inlet guide vane assembly 214 may include one or more inlet guide vanes 21 6 disposed in the inlet passageway 206 and configured to impart the one or more fluid properties and/or fluid flow attributes to the process fluid flowing through the inlet passageway 206. The inlet guide vanes 216 may also be configured to vary the one or more fluid properties and/or fluid flow attributes of the process fluid flowing through the inlet passageway 206. For example, respective portions of the inlet guide vanes 216 may be moveable (e.g. , adjustable) to vary the one or more fluid properties and/or fluid flow attributes (e.g. , swirl, velocity, mass flowrate, etc.) of the process fluid flowing through the inlet passageway 206. In an exemplary embodiment, the inlet guide vanes 216 may be configured to move or adjust within the inlet passageway 206, as disclosed in U.S. 8,632,302, the subject matter of which is incorporated by reference herein to the extent consistent with the present disclosure.

[0027] In another embodiment, illustrated in Figure 2A, the inlet guide vanes 216 may extend through the inlet passageway 206 from an inner surface 218 of the inlet 204 to a hub 220 of the inlet guide vane assembly 214. The inlet guide vanes 216 may be circumferentially spaced at substantially equal intervals or at varying intervals about the hub 220. The inlet guide vanes 216 may be airfoil shaped, streamline shaped, or otherwise shaped and configured to at least partially impart the one or more fluid properties on the process fluid flowing through the inlet passageway 206.

[0028] The compressor 200 may include an impeller 222 disposed in the impeller cavity 208. The impeller 222 may have a hub 224 and a plurality of blades 226 extending from the hub 224. In an exemplary embodiment, illustrated in Figure 2A, the impeller 222 may be an open or "unshrouded" impeller. In another embodiment, the impeller 222 may be a shrouded impeller. The impeller 222 may be configured to rotate about a longitudinal axis 228 of the compressor 200 to increase the static pressure and/or the velocity of the process fluid flowing therethrough. For example, the hub 224 of the impeller 222 may be coupled with the rotary shaft 108, and the impeller 222 may be driven or rotated by the driver 104 (see Figure 1) via the rotary shaft 108 and the drive shaft 106. The rotation of the impeller 222 may draw the process fluid into the compressor 200 via the inlet passageway 206. The rotation of the impeller 222 may further draw the process fluid to and through the impeller 222 and accelerate the process fluid to a tip 230 (see Figure 2B) of the impeller 222, thereby increasing the static pressure and/or the velocity of the process fluid. The plurality of blades 226 may be configured to impart the static pressure (potential energy) and/or the velocity (kinetic energy) to the process fluid to raise the velocity of the process fluid and direct the process fluid from the impeller 222 to the diffuser 210 fluidly coupled therewith. The diffuser 210 may be configured to convert kinetic energy of the process fluid from the impeller 222 into increased static pressure.

[0029] In one or more embodiments, the process fluid at the tip 230 of the impeller 222 may be subsonic and have an absolute Mach number less than one. For example, the process fluid at the tip 230 of the impeller 222 may have an absolute Mach number less than 1 , less than 0.9, less than 0.8, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1 . Accordingly, in such embodiments, the compressors 102, 200 discussed herein may be "subsonic," as the impeller 222 may be configured to rotate about the longitudinal axis 228 at a speed sufficient to provide the process fluid at the tip 230 thereof with an absolute Mach number of less than one.

[0030] In one or more embodiments, the process fluid at the tip 230 of the impeller 222 may be supersonic and have an absolute Mach number of one or greater. For example, the process fluid at the tip 230 of the impeller 222 may have an absolute Mach number of at least 1 , at least 1 .1 , at least 1.2, at least 1 .3, at least 1 .4, or at least 1 .5. Accordingly, in such embodiments, the compressors 102, 200 discussed herein are said to be "supersonic," as the impeller 222 may be configured to rotate about the longitudinal axis 228 at a speed sufficient to provide the process fluid at the tip 230 thereof with an absolute Mach number of one or greater or with a fluid velocity greater than the speed of sound. In a supersonic compressor or a stage thereof, the rotational or tip speed of the impeller 222 may be about 500 meters per second (m s) or greater. For example, the tip speed of the impeller 222 may be about 510 m/s, about 520 m/s, about 530 m/s, about 540 m/s, about 550 m/s, about 560 m/s, or greater.

[0031] As illustrated in Figures 2A and 2B, the compressor 200 may include a balance piston 232 configured to balance an axial thrust generated by the impeller 222 during one or more modes of operating the compressor 200. In at least one embodiment, the balance piston 232 and the impeller 222 may be separate components. For example, the balance piston 232 and the impeller 222 may be separate annular components coupled with one another. In another embodiment, illustrated in Figures 2A and 2B, the balance piston 232 may be integral with the impeller 222, such that the balance piston 232 and the impeller 222 may be formed from a single or unitary annular piece.

[0032] As illustrated in Figures 2A and 2B, the compressor 200 may also include a shroud 234 disposed proximal the impeller 222. For example, the shroud 234 may be disposed adjacent the plurality of blades 226 of the impeller 222. The shroud 234 may extend annularly about the impeller 222 such that an inner surface 236 thereof may be disposed near or proximal the plurality of blades 226 of the impeller 222. During one or more modes of operating the compressor 200, the inner surface 236 of the shroud 234 and the impeller 222 may define an impeller clearance (not shown) therebetween.

[0033] As illustrated in Figures 2A and 2B, the compressor 200 may include a balance piston seal assembly 238 having a balance piston seal 240 disposed about the balance piston 232 and configured to prevent or reduce a flow of the process fluid from leaking or flowing past the balance piston 232. For example, as illustrated in Figure 2B, the balance piston seal 240 may be disposed radially outward from an outer radial surface 242 of the balance piston 232. In at least one embodiment, illustrated in Figure 2A, the balance piston seal 240 may be or include a single, annular monolithic body. In another embodiment, the balance piston seal 240 may be formed from one or more arcuate segments configured to be coupled with one another. The balance piston seal 240 may be fabricated from one or more metals (e.g. , a metal alloy) . The balance piston seal 240 may be rotationally stationary with respect to the rotary shaft 108 and the balance piston 232 coupled therewith, which may rotate relative to the balance piston seal 240. An inner radial surface 244 of the balance piston seal 240 may extend circumferentially about and be radially offset from the outer radial surface 242 of the balance piston 232. The inner radial surface 244 of the balance piston seal 240 and the outer radial surface 242 of the balance piston 232 may at least partially define a radial gap or clearance 246 therebetween.

[0034] The inner radial surface 244 of the balance piston seal 240 may be or may provide a seal surface for the balance piston seal 240. It should be appreciated that the inner radial surface 244 may define any type of seal known in the art. For example, the inner radial surface 244 of the balance piston seal 240 may define a plurality of teeth (not shown) extending radially inward toward the outer radial surface 242 of the balance piston 232. Accordingly, the balance piston seal 240 may have a labyrinth seal along the inner radial surface 244 thereof. In another example, the inner radial surface 244 of the balance piston seal 240 may define a plurality of holes or openings (not shown). Accordingly, the balance piston seal 240 may provide a hole pattern sealing surface or a damper-type seal surface along the inner radial surface 244 thereof. In yet another example, the inner radial surface 244 may define a plurality of generally hexagonally-shaped openings (not shown) to thereby provide the balance piston seal 240 with a honeycomb seal surface along the inner radial surface 244 thereof.

[0035] The balance piston seal 240 may be coupled with (e.g. , indirectly or directly) the casing 202. In at least one embodiment, the balance piston seal 240 may be directly coupled with the casing 202. In another embodiment, the balance piston seal 240 may be indirectly coupled with the casing 202 via a stationary support 248 of the balance piston seal assembly 238. The balance piston seal 240 may generally be stationary with respect to the rotary shaft 108 and the balance piston 232 coupled therewith, which may rotate relative to the balance piston seal 240. In at least one example, the balance piston seal 240 may be coupled with the stationary support 248 and/or the casing 202 via one or more mechanical fasteners (one is shown 250). Illustrative mechanical fasteners may include, but are not limited to, one or more bolts, studs and nuts, or any other mechanical fasteners known in the art. In another example, the balance piston seal 240 may be coupled with the stationary support 248 via an interference or resistance fit or interlocking connections. In at least one embodiment, the stationary support 248 may be coupled with the casing 202. In another embodiment, the stationary support 248 may form a portion of or be integral with the casing 202 of the compressor 200.

[0036] The compressor 200 may include a shaft seal assembly 252 disposed proximal the balance piston 232 and about the rotary shaft 108. The shaft seal assembly 252 may include one or more seals (two are indicated 254, 256) disposed radially outward from and coaxially aligned with the rotary shaft 108. As illustrated in Figure 2B, the casing 202 and/or the balance piston 232 may at least partially define a seal cavity 258 configured to receive the one or more seals 254, 256. The seals 254, 256 may generally be configured to prevent the compressed process fluid from flowing or leaking out of the casing 202. The one or more seals 254, 256 may be or include dry gas seals, labyrinth seals, or the like, or any combination thereof. For example, as illustrated in Figure 2B, a first seal 254 may be a dry gas seal disposed in the seal cavity 258. The dry gas seal 254 may be configured to receive a seal gas or a conditioned gas to prevent the compressed process fluid from leaking out of the casing 202. For example, the seal gas may be directed to the seal cavity 258 and the dry gas seal 254 contained therein to form a non-contacting seal between the dry gas seal 254 and the rotary shaft 108. In at least one embodiment, the seal gas may be a portion of the compressed process fluid from a discharge line (not shown) of the compressor 200. In another embodiment, the seal gas may be provided by a closed-loop or an open-loop system. For example, the seal gas may be provided by an internal closed-loop system. As further illustrated in Figure 2B, a second seal 256 may be or include a labyrinth seal. The labyrinth seal 256 may be disposed in the seal cavity 258 between the balance piston 232 and the dry gas seal 254. The labyrinth seal 256 may generally be configured to prevent the compressed process fluid discharged from the tip 230 of the impeller 126 from flowing into or entering the seal cavity 258.

[0037] The casing 202, the shaft seal assembly 252, and/or the balance piston seal 232 may at least partially define a cavity 260 configured to receive the process fluid flowing through the radial clearance 246. As illustrated in Figure 2B, the cavity 260 may be disposed near or proximal the balance piston 232 and the labyrinth seal 256. As further illustrated in Figure 2B, the cavity 260 may be disposed radially outward of the seal cavity 258. The cavity 260 may extend annularly about the seal cavity 258 and the labyrinth seal 256. As further described herein, the cavity 260 may be configured to receive at least a portion of the compressed process fluid discharged from the impeller 222 and leaked through the radial clearance 246. The cavity 260 may have any shape and/or size suitable for receiving at least a portion of the compressed process fluid from the radial clearance 246. [0038] The compressor 200 may include a seal or sealing member 272 coupled or integral with the balance piston 232 and configured to prevent the compressed process fluid in the cavity 260 from flowing into one or more portions of the seal cavity 258. In an exemplary embodiment, the sealing member 272 may be or include a flange, a protrusion, or a tab extending from an axial surface 274 of the balance piston 232. It should be appreciated that the sealing member 272 may alternatively extend from an axial surface (not shown) of the impeller 222. As illustrated in Figure 2B and further illustrated in detail in Figure 2C, the sealing member 272, illustrated as a protrusion, may include a body 276 configured to cooperate with or form a sealing engagement with one or more components of the compressor 200 to at least partially prevent the compressed process fluid contained in the cavity 260 from flowing into or entering the seal cavity 258. In at least one embodiment, illustrated in Figure 2C, the body 276 of the protrusion 272 may be configured to form a sealing engagement with the labyrinth seal 256 to prevent the flow of the process fluid from the cavity 260 to one or more portions of the seal cavity 258. For example, the sealing member 272 may be configured to prevent the compressed process fluid in the cavity 260 from flowing into a forward portion of the seal cavity 258 defined between the axial surface 272 of the balance piston 232 and the labyrinth seal 256. Accordingly, the sealing member 272 may be configured to keep the axial surface 272 of the balance piston 232 at a relatively lower temperature than the cavity 260. In another embodiment, the body 276 of the protrusion 272 may be configured to form a sealing engagement with at least a portion of the casing 202.

[0039] The body 276 of the protrusion 272 may extend annularly along the axial surface 274 of the balance piston 232. The body 276 may have any shape or profile suitable for forming a sealing engagement with the one or more components (e.g. , the labyrinth seal 256, the casing 202, etc.) of the compressor 200. For example, as illustrated in Figure 2C, an inner radial surface 278 and/or an outer radial surface 280 of the body 276 or the profile thereof may extend substantially linearly. The inner radial surface 278 and the outer radial surface 280 may also be substantially parallel with one another. In at least one embodiment, the body 276 of the protrusion 272 may also have at least one concave surface (not shown) and/or at least one convex surface (not shown). For example, the inner and/or outer radial surfaces 278, 280 of the body 276 or the profile thereof may be arcuate or shaped to include at least one concave surface and/or at least one convex surface. The body 276 of the protrusion 272 may generally extend from the balance piston 232 in an axially direction. For example, as illustrated in Figure 2C, the body 276 of the protrusion 272 may extend axially from a base portion 282 coupled or integral with the balance piston 232 to an end portion 284. The body 276 of the protrusion 272 may also at least partially extend radially outward or radially inward. For example, the body 276 may extend from the base portion 282 such that the end portion 284 may be disposed radially outward of the base portion 282. Alternatively, the body 276 may extend from the base portion 282 such that the end portion 284 may be disposed radially inward of the base portion 282. Accordingly, the body 276 may be slanted in a radially outward direction or a radially inward direction.

[0040] As previously discussed, the protrusion 272 may be configured to form the sealing engagement with one or more components of the compressor 200. For example, at least a portion of the body 276 (e.g., the base portion 282 and/or end portion 284) may be configured to form the sealing engagement with the labyrinth seal 256 or another component of the compressor 200. In at least one embodiment, at least a portion of the body 276 may contact the labyrinth seal 256 or any other component(s) of the compressor 200 to form the sealing engagement. In another embodiment, at least a portion of the body 276 may extend toward the labyrinth seal 256 such that the end portion 284 may be disposed proximal a seal surface of the labyrinth seal 256 to form the sealing engagement therewith. For example, as illustrated in Figure 2C, the end portion 284 may be disposed in close proximity to an axial surface 286 and/or an outer radial surface 288 of the labyrinth seal 256 to thereby define a torturous path or serpentine gap 290 therebetween. The serpentine gap 290 may be configured to prevent or reduce a flow of the compressed process fluid from the cavity 260 to the seal cavity 258.

[0041] In an exemplary operation of the compressor 200, with continued reference to Figures 2A-2C, the driver 104 (see Figure 1 ) may drive the compressor 200 from rest to the steady state mode of operation by accelerating or rotating the rotary shaft 108 (via the drive shaft 106) , the impeller 222, and the balance piston 232 coupled therewith. The impeller 222 and the balance piston 232 may rotate relative to the balance piston seal 240 and about the longitudinal axis 228. The acceleration and/or rotation of the impeller 222 may draw the process fluid into the compressor 200 via the inlet passageway 206. The inlet guide vanes 216 disposed in the inlet passageway 206 may induce one or more flow properties (e.g., swirl) to the process fluid flowing therethrough. The rotation of the impeller 222 may further draw the process fluid from the inlet passageway 206 to and through the rotating impeller 222, and urge the process fluid to the tip 230 of the impeller 222, thereby increasing the velocity (e.g. , kinetic energy) thereof. The process fluid from the impeller 222 may be discharged from the tip 230 thereof and directed to the diffuser 210 fluidly coupled therewith. The diffuser 210 may receive the process fluid from the impeller 222 and convert the velocity (e.g., kinetic energy) of the process fluid from the impeller 222 to potential energy (e.g. , increased static pressure). The diffuser 210 may direct the process fluid downstream to the volute 212 fluidly coupled therewith. The volute 212 may collect the process fluid and deliver the process fluid to one or more downstream pipes and/or process components (not shown). The volute 212 may also be configured to increase the static pressure of the process fluid flowing therethrough by converting the kinetic energy of the process fluid to increased static pressure.

[0042] During one or more modes of operation, at least a portion of the process fluid discharged from the impeller 222 may flow or leak from the impeller 222 to the cavity 260 via the radial clearance 246. The protrusion 272 may form a sealing engagement with the labyrinth seal 256 to prevent or reduce the flow of the process fluid from the cavity 260 to the seal cavity 258. The sealing engagement formed between the labyrinth seal 256 and the protrusion 272 may maintain the seal cavity 258 at a relatively lower temperature than the cavity 260. For example, compressing the process fluid in the compressor 200 may generate thermal energy (e.g., heat of compression) to thereby heat the process fluid discharged from the impeller 222. According, the portion of the process fluid discharged from the impeller 222 and flowing into the cavity 260 via the radial clearance 246 may have a relatively high temperature , and forming the sealing engagement between the protrusion 272 and the labyrinth seal 256 may prevent the flow of the heated process fluid from the cavity 260 to the seal cavity 258, thereby maintaining the seal cavity 258, a bore of the impeller 222, and/or the balance piston 232 at a relatively lower temperature than the cavity 260. It should be appreciated that maintaining the seal cavity 258 at a relatively lower temperature may also maintain the bore of the impeller 222 , the balance piston 232, and/or the dry gas seal 254 at a relatively lower temperature . Maintaining the bore of the impeller 222 and/or the balance piston 232 at a relatively lower temperature may preserve one or more metallurgical properties (e.g. , strength) of the bore of the impeller 222 and/or the balance piston 232. It should also be appreciated that maintaining the dry gas seal 254 at a relatively lower temperature may allow the compressor 200 to utilize a cost effective, standard dry gas seal in lieu of high temperature dry gas seals.

[0043] In addition to the foregoing, a cooling fluid, such as the seal gas, may be directed to the seal cavity 258 to prevent the flow of the heated process fluid from the cavity 260 to the seal cavity 258. For example, the seal gas may be directed to the seal cavity 258 to maintain the seal cavity 258 at a relatively higher pressure than the cavity 260. Accordingly, the seal gas contained in the seal cavity 258 may be discharged or purged from the seal cavity 258 to the cavity 260 via the serpentine gap 290 defined between the protrusion 272 and the labyrinth seal 256. The seal gas discharged from the seal cavity 258 may converge with the heated process fluid from the cavity 260 at or proximal the serpentine gap 290. The convergence of the pressurized seal gas with the heated process fluid and/or the purging of the seal gas from the seal cavity 258 may prevent the flow of the heated process fluid from the cavity 260 to the seal cavity 258. It should be appreciated that the pressure of the seal gas injected into the seal cavity 258 and/or the pressure of the seal cavity 258 may be regulated via an external and/or an internal device (e.g. , flow control valve).

[0044] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.