Abstract:
A seal system having a rotating seal section and a static seal section operable for working together to restrict fluid flow there between. An arm connected to the static seal is tuned to move the static seal asymmetrically to correspond with asymmetric movement of the rotating seal during operation to maintain a desired relative position between the static and rotating seals.

Description:
CROSS REFERENCE 
     The present application claims the benefit of U.S. Patent Application No. 60/875,640, filed Dec. 19, 2006, which is incorporated herein by reference. 
    
    
     GOVERNMENT RIGHTS 
     The present invention was made with U.S. Government support under contract no. N00019-04-C-0093 awarded by the United States Navy. The United States Government will have certain rights herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a fluid seal, and more particularly in one form to a fluid seal having a static portion tuned to match deflections of a rotating portion as operating conditions change within an apparatus. 
     BACKGROUND 
     Fluid seals in high-speed machines such as a gas turbine engines typically have a rotating section and a corresponding static section. Some fluid seals are designed such that the rotating section engages the static section during operation. Other fluid seals are designed to have a predetermined gap or space between the rotating and static sections. One problem associated with fluid seals is that during certain operating conditions the static section and rotating section may be displaced from their nominal positions. Operating parameters that cause movement or deflection in the seal position include rotational speed of the rotating section as well as pressure, temperature, and mass flow rate of the fluid. If the static section and the rotating section each deflect proportionally during operation of the machine then the seal will work as designed. If however, the deflection of the static section does not match the deflection of the rotating section then the seal will be less effective. The present application provides a novel and non-obvious improvement in seal operation as the static section of the seal is tuned to match the movement or deflection of the rotating section of the seal. 
     SUMMARY 
     An aspect of the present invention discloses an apparatus having a rotating component with a rotating fluid seal coupled with a static seal for restricting fluid flow therebetween. An arm having first and second ends connected to static structure carries the static seal and is tuned to asymmetrically move in response to a change of operating conditions in the apparatus. 
     Another aspect of the present invention discloses a seal system comprising a rotatable seal and a static seal operable for working with the rotatable seal to restrict fluid flow therebetween and an arm connected to the static seal. The arm is tuned to move in an asymmetric manner to correspond with asymmetric movement of the rotatable seal as operating conditions of the seal system changes. 
     In another aspect of the present invention a method provides for controlling the position of a static seal relative to a position of a rotating seal, operating the rotating seal in a machine, asymmetrically moving the rotating seal in a manner in response to operating conditions within the machine and moving the static seal in an asymmetric manner corresponding to the asymmetric movement of the rotating seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  is a schematic view of a gas turbine engine; 
         FIG. 2  is section view of a fluid seal within a gas turbine engine; 
         FIG. 3  is a first exemplary embodiment of a static section of a fluid seal according to the present invention; 
         FIG. 4  is a second exemplary embodiment of a static section of a fluid seal according to the present invention; and 
         FIG. 5  is a third exemplary embodiment of a static section of a fluid seal according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Many fluid seals are designed to restrict fluid flow from moving between rotating and static sections of the seal. It may be desirable to completely eliminate fluid flow, or alternatively, to minimize the flow to a predefined level. Fluid seals in machines such as gas turbine engines work well at design conditions and when the static section of the seal matches the displacement or deflection of the rotating section of the seal during operation of the machine. However, many rotating seals do not always move symmetrically in a radial direction in response to temperature and pressure changes. Sometimes rotating seals move asymmetrically such that one end of the seal moves to a different radial location than the other end. When asymmetrical movement occurs in the rotating section of the seal and the static section of the seal does not move a similar manner, the seal loses its design effectiveness. In order to minimize the gap between the rotating and static sections of the seal without rubbing the static section of the seal, the static section must be designed to move proportionally with respect to the rotating section of the seal. 
     Referring to  FIG. 1 , a schematic view of a gas turbine engine  10  is depicted. While the gas turbine engine is illustrated with one spool (i.e. one shaft connecting a turbine and a compressor), it should be understood that the present invention is not limited to any particular engine design or configuration and as such may be used in multi spool engines of the aero or power generation type. The gas turbine engine  10  will be described generally, however significant details regarding general gas turbine engines will not be presented herein as it is believed that the theory of operation and general parameters of gas turbine engines are well known to those of ordinary skill in the art. 
     The gas turbine engine  10  includes an inlet section  12 , a compressor section  14 , a combustor section  16 , a turbine section  18 , and an exhaust section  20 . In operation, air is drawn in through the inlet  12  and compressed to a high pressure relative to ambient pressure in the compressor section  14 . The air is mixed with fuel in the combustor section  16  wherein the fuel/air mixture burns and produces a high temperature and pressure working fluid from which the turbine section  18  extracts power. The turbine section  18  is mechanically coupled to the compressor section  14  via a shaft  22 . The shaft  22  rotates about a centerline axis  24  that extends axially along the longitudinal axis of the engine  10 , such that as the turbine section  18  rotates due to the forces generated by the high pressure working fluid, the compressor section  14  is rotatingly driven by the turbine section  18  to produce compressed air. A portion of the power extracted from the turbine section  18  can be utilized to drive a secondary device  26 , such as an electrical, gas compressor or pump and the like. Alternatively, the gas turbine engine  10  can be of the aero type to produce thrust or shaft power for fixed wing aircraft or rotorcraft, respectively. Thrust producing engines produce high velocity mass flow through the exhaust section  20  and do not drive a secondary device  26 . 
     Referring now to  FIG. 2 , a fluid seal  30  located internal to the engine  10  is illustrated. The fluid seal  30  includes a static section  32  and a rotating section  34 . The rotating section  34  extends from a rotating component such as a shaft  36  and is positioned proximate the static section  32  of the seal  30 . The rotating section  34  of the seal  30  can include a plurality of edges  38  sometimes called knives that extend radially outward between a leading edge  40  and a trailing edge  42  of the rotating section  34 . The static section  32  of the seal  30  can include a flange  44  to connect with static support structure  46  within the engine  10 . A plurality of mechanical fasteners  48  such as threaded bolts or screws and the like can be used to attach the flange  44  to the static structure  46 . An outer arm  50  is connected to the flange  44  and extends toward a desired location of the static section  32  of the fluid seal  30 . An attachment arm  52  connects an inner arm  54  to the outer arm  50  of the static seal section  32 . The inner arm  54  has a leading edge  56  and a trailing edge  58  and is connected to the attachment arm  52  at an attachment point  57  between the leading and trailing edges  56 ,  58 , respectively. The present application contemplates that the length from the leading edge to the attachment point  57  and the length from the trailing edge  58  to the attachment point  57  may be similar or dissimilar. It should be understood that the terms “leading-edge” and “trailing edge” are with reference to fluid flow direction. In general, a fluid streamline will pass by a leading edge prior to passing the trailing edge for any particular component. 
     A static seal member  60  is attached to the inner arm  54 . The static seal member  60  extends radially inward toward the rotating seal section  34 . The seal member  60  can be made from materials that can withstand the temperatures, pressures and loads placed on the seal in operation. Typical material selection would include metals such as stainless steel and super alloys as would be known to those killed in the art. The static seal member  60  can be a honeycomb seal, but also could include other types such as brush seals and labyrinth seals. The seal  32  can be formed as a continuous 360° ring or alternatively can be segmented or placed in discreet positions around a centerline of rotation  24  as desired. The static seal  32  is designed to maintain a desired position relative to the rotating seal  34 . The relative position between the static and rotating sections  32 ,  34  respectively, can include no gap (i.e. engagement) to a relatively large gap if metered fluid flow through the seal  30  is desired. 
     Referring now to  FIG. 3 , one embodiment of the present invention shows a static seal  32  operable for moving asymmetrically by offsetting the attachment point  57  of the inner arm  54  to the attachment arm  52  toward the trailing edge  58  of the inner arm  54 . If the inner arm  54  pivots about the attachment point  57  during operation caused by movement in the outer arm  50  or attachment arm  52 , then the leading edge  56  will be located in a different radial position than the trailing edge  58 . The inner arm  54  includes a foreward portion  62  and an aft portion  64 . For example, if the inner arm  54  pivots counterclockwise about attachment point  57 , then the leading edge  56  will be located radially inward relative to the trailing edge  58 . 
     Referring now to  FIG. 4 , another embodiment of the present invention shows a static seal  32  operable for moving asymmetrically by forming foreword portion  62  of the inner arm  54  with a different section thickness than aft portion  64 . It should be understood that section thickness could be greater in one of the foreword or aft portions  62 ,  64  than the other of the foreword or aft portions. A thicker section will cause the inner arm  54  to respond slower to temperature variations and will be stiffer to withstand pressure loads relative to a thinner section of the inner arm  54 . 
     Referring now to  FIG. 5 , another embodiment of the present invention shows a static seal  32  operable for moving asymmetrically by forming the offset attachment point  57  with a change of section shape in the aft portion  64  or forward portion  62  of the inner arm  54 . It should be understood that the magnitude and direction of the offset and the section thickness can be varied as necessary to match the deflection of the rotating section  34 . Further alternate embodiments of the present invention can include asymmetrical construction and attachment of other static structure such as the outer arm  50  and the attachment arm  52 . 
     In operation, the static section  32  of the seal  30  is positioned at a nominal location relative to the rotating section  34  of the seal. The nominal position of the static and rotating seals  32 ,  34  can include full engagement between the two or alternatively provide a gap therebetween. When the operating temperature of the fluid in the engine  10  increases, the radial position of the knife edges  38  and the static seal member  60  generally will deflect outward in a radial direction. Due to design and operating conditions, the rotating section  34  may deflect asymmetrically in the radial direction. Utilizing the design techniques disclosed by the present invention, the static section  32  of the seal can substantially match the asymmetrical movement of the rotating section  34  thereby minimizing the variation in gap distance between the rotating and static sections  32 ,  34  of the seal  30 . 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.