Patent Publication Number: US-9835169-B2

Title: Actuator sealing system and method

Description:
BACKGROUND OF THE INVENTION 
     Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for sealing an actuator rod in a variable inlet vanes system. 
     During the past years, the importance of compressors in various industries has increased. The compressors are used in engines, turbines, power generation, cryogenic applications, oil and gas processing, etc. Therefore, various mechanisms and techniques related to compressors are often subject to research for improving the efficiency of this turbomachine and solving problems related to specific situations. 
     Actuation systems are used in various equipments, such as, compressors, pumps and expanders, to apply a force in order to modify a current state of the equipment. For example, an actuation system may operate adjustable inlet guide vanes (IVG) used in compressor applications to adjust an angle of incidence of inlet air into a compressor rotor and to control an amount of inlet air such as to ensure proper surge and to maximize efficiency. 
     An example of an adjustable IGV system  100  is shown in  FIG. 1 , which is reproduced from M. Hensges, Simulation and Optimization of an Adjustable Inlet Guide Vane for Industrial Turbo Compressors from the Proceedings of ASME Turbo Expo 2008: Power for Land, Sea and Air (Jun. 9-13, 2008), the entirety of which is hereby incorporated by reference. The adjustable IGV system  100  includes an actuator lever  102  directly connected to a first vane  104 . The first vane  104  is connected via a drive arm  106  to a driving ring  108 . The first vane  104  is rotatably attached to a guide vane carrier  110 . A plurality of other vanes  112  are rotatably attached to the guide vane carrier  110 . The plurality of vanes  112  are actuated by a plurality of linkages  114  that are connected to the driving ring  108 . Thus, when the actuator lever  102  is rotated, it determines a rotation of the first vane  104  but also a displacement of the driving ring  108 , which results in a movement of the plurality of linkages  114  and a rotation of the plurality of vanes  112 . 
       FIG. 2  illustrates a manner of operating the adjustable IGV system (here  116  is a guide vane carrier). At a contact point  118 , an actuation force F applied from an actuation bar  120  is transferred to the driving ring  108 . The actuation force transmitted via the actuator rod  120  is generated by an actuation device  130 . The actuation device  130  is controlled and/or monitored at least in part by control electronics  140  that is located inside the actuation device. 
     Given the potentially damaging environment in which the adjustable IGV system  100  may operate (for example, when used in a natural gas installation), the control electronics  140  is isolated from this environment. Conventionally, this separation of the control electronics  140  from the environment is achieved using mechanical seals, for example, a dynamic seal energized by springs closing a space between the body of the actuation device  130  and the actuator rod  120 . 
     It has been observed that the mechanical seals do not operate satisfactory. Moreover, sometimes the gas in the environment (i.e., outside the actuation device) has low (cryogenic) temperature and, therefore, the chilled actuator rod  120 , which extends inside the body of the actuator device  130  and is a good heat conductor, may determine ice formation (by condensation of the humidity inside the case). The ice may block the actuators bar&#39;s movement. 
     Further, if the force is generated hydraulically, different pressures inside and outside the actuation device  130  may create further problems (e.g., imbalances and forces) and inefficiencies (e.g., a direction of the force may be altered), when the sealing is not effective. 
     Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks. 
     BRIEF SUMMARY OF THE INVENTION 
     According to various embodiments, separating a first fluid at one end of an actuator rod and a second fluid at an opposite end of the actuator rod is achieved using at least one fluid flow. 
     According to one exemplary embodiment, an actuator device useable to change orientation of one or more vanes includes an actuator rod and an actuator device body. The actuator rod is configured to transfer a force along an axis thereof, and having a first end in a first fluid and a second end in a second fluid, the second end being opposite to the first end along the axis. The actuator device body is configured to allow the actuator rod to move along the axis inside the actuator device body, and having has a first inlet flange configured to allow a third fluid to enter a space between the actuator device body and the actuator rod, and a first outlet flange configured to allow the third fluid to exit the actuator device body. The third fluid has a pressure larger than a pressure of the first fluid, and the first outlet flange is closer to the first end of the actuator rod than the first inlet flange. 
     According to another exemplary embodiment, a compressor has one or more vanes configured to determine at least one of a direction and an amount of a first fluid passing through the compressor, and an actuator device configured to apply a force to the one or more vanes. The actuator device includes an actuator rod and an actuator device body. The actuator rod is configured to transfer a force along an axis thereof, and having a first end in a first fluid and a second end in a second fluid, the second end being opposite to the first end along the axis. The actuator device body is configured to allow the actuator rod to move along the axis inside the actuator device body, and having has a first inlet flange configured to allow a third fluid to enter a space between the actuator device body and the actuator rod, and a first outlet flange configured to allow the third fluid to exit the actuator device body. The third fluid has a pressure larger than a pressure of the first fluid, and the first outlet flange is closer to the first end of the actuator rod than the first inlet flange. 
     According to another exemplary embodiment, a method of sealing a compressor fluid at a first end of an actuation bar and an environment at a second end of the actuation bar, the second end being opposite to the first end, and the actuation bar being configured to move along an axis, inside an actuator device body is provided. The method includes providing a first flow of compressor fluid routed from an output of the compressor in a space between the actuator device body and the actuator rod, via a first inlet flange of the actuator body and a first outlet flange of the actuator body, (1) the compressor fluid in the first flow having a pressure larger than a pressure of the compressor fluid at a first end of an actuation bar, and (2) the first outlet flange being closer to the first end of the actuator rod than the first inlet flange. The method further includes providing a second flow of neutral fluid in the space between the actuator device body and the actuator rod, via a second inlet flange of the actuator body and a second outlet flange of the actuator body, (3) the first inlet flange and the first outlet flange being closer to the first end than the second inlet flange and the second outlet flange, and (4) the second inlet flange being closer to the second end of the actuation bar than the second outlet flange. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings: 
         FIG. 1  is a schematic diagram of an IVG system; 
         FIG. 2  is an illustration of an actuator device operating an IVG system; 
         FIG. 3  is a schematic diagram of an actuator device according to an exemplary embodiment; 
         FIG. 4  is a schematic diagram of an actuator device according to another exemplary embodiment; 
         FIG. 5  is a schematic diagram of an actuator device according to another exemplary embodiment; 
         FIG. 6  is a schematic diagram of an actuator device according to another exemplary embodiment; 
         FIG. 7  is a schematic diagram of an actuator device operating in IGV vanes of a compressor according to another exemplary embodiment; and 
         FIG. 8  is a flow chart of a method of sealing a compressor fluid at a first end of an actuation bar from an environment at a second end of the actuation bar in a compressor, the second end being opposite to the first end, and the actuation bar being configured to move along an axis according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION 
     The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of compressors having inlet vanes that are modified by applying a force via an actuator device. However, the embodiments to be discussed next are not limited to these compressors, but may be applied to other systems that require to isolate an environment at one end of an actuator rod thereof from an environment at another end of the actuation rod. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
     In actuator devices according to various embodiments, the mechanical seals with springs are replaced by dynamical sealing using one or more flows of fluid circulating between an actuator rod and an actuator body. At least one of the flows of fluid may heat the actuator rod preventing the formation of ice. 
       FIG. 3  illustrates an exemplary embodiment of an actuator device  300  that is configured to apply a force along an axis  305 . The actuator device  300  may be used to change the orientation of one or more vanes. The actuator device  300  includes an actuator rod  310  configured to transfer a force along the axis  305 . A first end  312  of the actuator rod  310  is surrounded by a first fluid, for example, natural gas entering a compressor. 
     The actuator rod  310  is mounted to move through an actuator device body  320 . In other words, the actuator device body  320  is configured to allow the actuator rod  310  to move along the axis  305  inside the actuator device body  320 . A second end  314  of the actuator rod  310  (which second end is opposite to the first end  312  along the axis  305 ) may be exposed to a second fluid that may be confined inside a cavity  316  of the actuator device body  320 . Control electronics  318  may be mounted on the actuator device body  320  to be exposed with the second fluid. The term control electronics may stand for an actuator and/or an actuator motor. The invention is not limited by the device(s) collectively named control electronics exposed to the second fluid kept isolated from the corrosive first fluid. 
     The second fluid may be air or other fluid that does not have a negative effect on the electronics  318 . However, the natural gas that may be compressed in a compressor is usually corrosive and typically leads to rapid degradation of the electronics. Therefore, the actuator device body  320  and the actuator rod  310  are configured and operated to prevent the first fluid (e.g., natural gas) from mixing with the second fluid (e.g., air). 
     The actuator body  320  is therefore configured to allow a third fluid to flow inside the actuator body, in a space between the actuator rod  310  and the actuator body  320 . In order to allow the third fluid to enter this space, the actuator device body  320  has a first inlet flange  322 . In order to allow the third fluid to exit the actuator device body, the actuator device body  320  has a first outlet flange  324 . Thus, the third fluid flows from the first inlet flange  322  to the first outlet flange  324  parallel to the axis  305  and between the actuator rod  310  and the device body  320 . The outlet flange  324  may be closer to the first end  312  of the actuator rod  310  than the first inlet flange  322 . The third fluid may have a pressure larger than a pressure of the first fluid and/or substantially the same composition as the first fluid. For example, the third fluid may be compressed first fluid (i.e., gas) re-circulated from an outlet of the compressor. 
     The third fluid may have a temperature different from a temperature of the first fluid. To control the temperature of the third fluid, a heat exchanger or similar known devices may be used. Thereby, the actuator rod  310 , which is made of a good heat conductor (e.g., metal or metallic alloy), may be heated due to the third fluid so that condensation and ice do not occur. 
     A number of mechanical seals  330  may be present at various locations but the present inventive concept is not limited by the presence of other seals. Between the actuator  310  rod and the one or more vanes moved due to a force generated along the axis  305  in the actuator device  300 , it may be a connecting rod  340 , but the present inventive concept is not limited by the presence of such a connecting rod. 
     The third fluid flow may also be used to develop a force along the axis. For example, as illustrated in  FIG. 4 , an actuator device  400  according to another exemplary embodiment includes the actuator rod  410  configured to have a step  415  located between a position of the sealing inlet flange  322  and a position of the sealing outlet flange  324  along the axis  305 . In other words, a first area A 1  of the actuator rod  410 , perpendicular to the axis  305 , between the position of the sealing inlet flange and the step  415  is smaller than a second area A 2  of the actuator rod  410 , perpendicular to the axis, between the step  415  and the position of the sealing outlet flange  324 . This change of cross-sectional area (perpendicular to a direction in which the third fluid flows, i.e., parallel to axis  305 ), makes the flow of the third fluid not only to seal the rod but also to generate a force in the flowing direction, thus contributing to the overall force of the actuator device  400 . The step  415  has also a balancing effect as the fluid from the compressor acts on the rod  410  in one direction and the third fluid acts on the rod  410  in the opposite direction. 
     In another exemplary embodiment illustrated in  FIG. 5 , an actuator device  500  has an actuator device body  520  configured to allow another fluid to flow in the space between the actuator device body  520  and the actuator rod  310 . The actuator device body  520  has a second inlet flange  532  configured to allow a neutral fluid to enter a space in-between the actuator device body  520  and the actuator rod  310 , and a second outlet flange  534  configured to allow the neutral fluid to exit the actuator device body  520 . The first inlet flange  322  and the first outlet flange  324  are closer to the first end  312  of the actuation rod  310  than the second inlet flange  532  and the second outlet flange  534 . Also, the second inlet flange  532  is closer to the second end  314  of the actuation rod  310  than the second outlet flange  534 . The neutral fluid may be mostly nitrogen (N 2 ), for example, the neutral fluid may contain 70% nitrogen. 
     When a pressure of the neutral fluid entering the space is larger than a pressure of the fluid entering the first inlet flange  322 , it may further prevent the fluid from  322  to advance toward the closed cavity  316  where the electronics  318  is installed. Thus, the sealing around the actuator rod  310  is further enhanced. Of course, traditional seals  330  may also be provided closer to the end  314  of the rod  310  for further sealing. 
     Further, the actuator device body may include a vent  550  located between the first inlet flange  322  and the second outlet flange  534  along the axis  305 , and configured to allow the neutral fluid and/or the third fluid to exit the actuator device body  520 . 
       FIG. 6 , is an embodiment of an actuator device  600  including plural of the features described above (the same reference numbers in  FIGS. 3-6  identify the same or similar elements). Additionally, the actuator device  600  (or any of the actuators  300 ,  400 ,  500 ) may include a third fluid temperature regulator  660  configured to change a current temperature of the third fluid before entering the first inlet flange  322 . The third fluid may be heated or cooled depending on the specific application/usage of the actuator device. 
     In an overall view illustrated in  FIG. 7 , compressor  700  has one or more vanes  710  configured to determine at least one of a direction and an amount of a first fluid passing through the compressor, and an actuator device  720 . The actuator device  720 , which may be any of the devices  300 ,  400 ,  500 ,  600  described above, is configured to apply a force to the one or more vanes  710 . The compressor  700  has a compressor  730  body configured to receive the first fluid after passing through the one or more vanes, to compress the first fluid, and then to output the compressed first fluid. The third fluid may be a portion of the compressed first fluid. 
     Some of the embodiments described about may execute a method  800  of sealing a compressor fluid at a first end of an actuator rod and an environment at a second end of the actuator rod, the second end being opposite to the first end, and the actuator bar being configured to move along an axis, inside an actuator device body. The method  800  illustrated in  FIG. 8  includes providing a first flow of compressor fluid routed from an output of the compressor in a space between the actuator device body and the actuator rod, via a first inlet flange of the actuator body and a first outlet flange of the actuator body, (1) the compressor fluid in the first flow having a pressure larger than a pressure of the compressor fluid at a first end of an actuation bar, and (2) the first outlet flange being closer to the first end of the actuator rod than the first inlet flange, at  5810 . 
     The method  800 , further includes providing a second flow of neutral fluid in the space between the actuator device body and the actuator rod, via a second inlet flange of the actuator body and a second outlet flange of the actuator body, (3) the first inlet flange and the first outlet flange being closer to the first end than the second inlet flange and the second outlet flange, and (4) the second inlet flange being closer to the second end of the actuation bar than the second outlet flange, at S 820 . 
     The disclosed exemplary embodiments provide devices and methods for sealing, preventing icing and balancing an actuator of an IGV of a turbo-machine. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. 
     Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. 
     This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.