Patent Abstract:
A fuel system for an energy conversion device includes a multiple of non-metallic fuel plates, gaskets, oxygen permeable membranes, porous substrate plates, and vacuum frame plates. Intricate 3-dimension fuel channel structures such as laminar flow impingement elements within the fuel channel dramatically enhance oxygen diffusivity in the FSU. The fuel plates are manufactured from a relatively soft non-metallic material. The non-metallic fuel plates and gasket arrangement provide an effective sealing interface between the fuel plate and oxygen permeable membrane, since compression may be applied to the plates without damaging the relatively delicate oxygen permeable membrane.

Full Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to stabilizing fuel by deoxygenation, and more particularly to a fuel plate assembly for a fuel stabilization unit.  
         [0002]     Fuel is often utilized in aircraft as a coolant for various aircraft systems. The presence of dissolved oxygen in hydrocarbon jet fuels may be objectionable because the oxygen supports oxidation reactions that yield undesirable by-products. Dissolution of air in jet fuel results in an approximately 70 ppm oxygen concentration. When the fuel is heated between 300 and 850° F. the oxygen initiates free radical reactions of the fuel resulting in deposits commonly referred to as “coke” or “coking.” Coke may be detrimental to the fuel lines and may inhibit fuel delivery. The formation of such deposits may impair the normal functioning of a fuel system, either with respect to an intended heat exchange function or the efficient injection of fuel.  
         [0003]     Various conventional fuel deoxygenation techniques are currently utilized to deoxygenate fuel. Typically, lowering the oxygen concentration to 6 ppm or less is sufficient to overcome the coking problem.  
         [0004]     One conventional Fuel Stabilization Unit (FSU) utilized in aircraft fuel systems removes oxygen from jet fuel by producing an oxygen partial pressure gradient across a membrane permeable to oxygen. The FSU includes a plurality of fuel plates sandwiched with permeable membranes and porous substrate plates within an outer housing. Each fuel plate defines a portion of the fuel passage and the porous plate backed permeable membranes defines the remaining portions of the fuel passages. The permeable membrane includes Teflon AF or other type of amorphous glassy polymer coating in contact with fuel within the fuel passages for preventing the bulk of liquid fuel from migrating through the permeable membrane and the porous plate.  
         [0005]     The use of a plurality of similarly configured flat plates increases manufacturing efficiency and reduces overall cost. Further, the size and weight of the FSU is substantially reduced while increasing the capacity for removing dissolved oxygen from fuel. Moreover, the planar design is easily scalable compared to previous tubular designs.  
         [0006]     Disadvantageously, the planar fuel plates are typically stainless steel which is relatively difficult, time-consuming, and expensive to machine while the oxygen permeable membrane is a relatively delicate, thin (˜2-5 microns) film which may lack mechanical integrity. Contact between the metallic fuel plate and the oxygen permeable membrane may result in damage to the permeable membrane which necessitates careful manufacture and assembly to avoid leakage between the multitude of plates.  
         [0007]     A failed seal between plates or a damaged permeable membrane may permit inter-stream leakage which may dramatically decrease the performance of the FSU. Sealing the interface between fuel plates, sealing the fuel channel between fuel plates and the oxygen permeable membrane, as well as sealing the vacuum path from potential leaks to ambient are critical to effective operation of the FSU. Furthermore, to increase oxygen diffusivity and enhance fuel deoxygenator performance, the fuel plate includes a relatively intricate 3-dimension fuel channel structure which further complicates sealing and manufacture.  
         [0008]     Although effective manufacturing techniques exist for the production of the relatively intricate 3-dimension fuel channel structure and the high-precision FSU sealing gaskets, these conventional techniques are exceedingly time consuming and expensive.  
         [0009]     Accordingly, it is desirable to provide an effective relatively inexpensive and uncomplicated fuel plate and sealing gasket arrangement for a deoxygenation system that facilitates manufacture of an intricate 3-dimension fuel channel structure to increase fuel and deoxygenation.  
       SUMMARY OF THE INVENTION  
       [0010]     The fuel system for an energy conversion device according to the present invention includes a deoxygenator system that comprises a multiple of non-metallic fuel plates, gaskets, oxygen permeable membranes, porous substrate plates, epoxy film adhesive, liquid epoxy materials, and vacuum frame plates. The deoxygenator system is an on-line fuel stabilization unit (FSU) that deoxygenates fuel for use in aircraft thermal management applications. An important element of the FSU is the fuel plate. Intricate 3-dimension fuel channel structures such as laminar flow impingement elements within the fuel channel dramatically enhance oxygen diffusivity in the FSU. The fuel plates are manufactured from a relatively soft non-metallic material, such as various plastics or KAPTON®. Utilizing laser cutting with non-metallic materials permits cost-effective manufacture of relatively large area fuel plates with intricate 3-dimension fuel channel structures heretofore unavailable with metallic fuel plats.  
         [0011]     The non-metallic fuel plates advantageously provide an effective sealing interface between the fuel plate and oxygen permeable membrane, since compression may be applied to the plates without damaging the relatively delicate oxygen permeable membrane. The non-metallic fuel plates permit manufacturing techniques for the intricate 3-dimensional fuel channel structures and correspondingly intricate sealing gaskets that seal and soften the contact between the fuel plates, the oxygen permeable membrane, and the non-metallic fuel plate as well as permit sealing within the fuel channel.  
         [0012]     The present invention therefore provides an effective relatively inexpensive and uncomplicated fuel plate and sealing gasket arrangement for a deoxygenation system that facilitates manufacture of an intricate 3-dimension fuel channel structure to increase fuel turbulence and deoxygenation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
         [0014]      FIG. 1  is a general schematic block diagram of an energy conversion device (ECD) and an associated fuel system employing a fuel deoxygenator in accordance with the present invention;  
         [0015]      FIG. 2A  is a perspective view of the fuel deoxygenator of the present invention;  
         [0016]      FIG. 2B  is an exploded view of the fuel deoxygenator of the present invention;  
         [0017]      FIG. 2C  is a sectioned perspective and expanded view of the deoxygenator system;  
         [0018]      FIG. 2D  is a plan view of a gasket of the fuel deoxygenator;  
         [0019]      FIG. 2E  is an expanded sectional view of the fuel deoxygenator;  
         [0020]      FIG. 3  is an expanded schematic sectional view of a flow channel;  
         [0021]      FIG. 4A  is an expanded top view of a fuel plate of the fuel deoxygenator;  
         [0022]      FIG. 4B  is an expanded bottom view of the fuel plate of  FIG. 4A ;  
         [0023]      FIG. 4C  is an expanded perspective view of a groove and up-standing member interface with a gasket between a first and a second fuel plate;  
         [0024]      FIG. 4D  is an expanded plan view of a fuel plate illustrating a fuel gasket location;  
         [0025]      FIG. 4E  is an expanded plan view of a fuel plate illustrating a vacuum gasket location;  
         [0026]      FIG. 4F  is an expanded perspective view of a multiple of fuel plates illustrating a fuel port and vacuum port location;  
         [0027]      FIG. 4G  is an expanded sectional view taken along a short axis of the fuel deoxygenator illustrating inter plate vacuum ports; and  
         [0028]      FIG. 4H  is an expanded sectional view taken along a long axis of the fuel deoxygenator illustrating inter plate fuel communication. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]      FIG. 1  illustrates a general schematic view of a fuel system  10  for an energy conversion device (ECD)  12 . A deoxygenator system  14  receives liquid fuel F from a reservoir  16  such as a fuel tank. The fuel F is typically a liquid hydrocarbon such as jet fuel. The ECD  12  may exist in a variety of forms in which the liquid hydrocarbon, at some point prior to eventual use as a lubricant, or for processing, for combustion, or for some form of energy release, acquires sufficient heat to support autoxidation reactions and coking if dissolved oxygen is present to any significant extent in the liquid hydrocarbon.  
         [0030]     One form of the ECD  12  is a gas turbine engine, and particularly such engines in aircraft. Typically, the fuel also serves as a coolant for one or more sub-systems in the aircraft and becomes heated as it is delivered to fuel injectors immediately prior to combustion.  
         [0031]     A heat exchange section  18  represents a system through which the fuel passes in a heat exchange relationship. It should be understood that the heat exchange section  18  may be directly associated with the ECD  12  and/or distributed elsewhere in the larger system  10 . The heat exchange system  18  may alternatively or additionally include a multiple of heat exchanges distributed throughout the system.  
         [0032]     As generally understood, fuel F stored in the reservoir  16  normally contains dissolved oxygen, possibly at a saturation level of 70 ppm. A fuel pump  20  draws the fuel F from the reservoir  16 . The fuel pump  20  communicates with the reservoir  16  via a fuel reservoir conduit  22  and a valve  24  to a fuel inlet  26  of the deoxygenator system  14 . The pressure applied by the fuel pump  20  assists in circulating the fuel F through the deoxygenator system  14  and other portions of the fuel system  10 . As the fuel F passes through the deoxygenator system  14 , oxygen is selectively removed into a vacuum system  28 .  
         [0033]     The deoxygenated fuel Fd flows from a fuel outlet  30  of the deoxygenation system  14  via a deoxygenated fuel conduit  32 , to the heat exchange system  18  and to the ECD  12  such as the fuel injectors of a gas turbine engine. A portion of the deoxygenated fuel may be recirculated, as represented by recirculation conduit  33  to either the deoxygenation system  14  and/or the reservoir  16 . It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from the instant invention.  
         [0034]     Referring to  FIG. 2A , the deoxygenator system  14  preferably includes a multiplicity of vacuum/fuel flow-channel assemblies  34  ( FIG. 2B ). The assemblies  34  include a oxygen permeable membrane  36  between a fuel channel  38  and an oxygen receiving vacuum channel  40  which can be formed by a supporting mesh ( FIG. 3 ). It should be understood that the channels may be of various shapes and arrangements to provide a oxygen partial pressure differential, which maintains an oxygen concentration differential across the membrane to deoxygenate the fuel.  
         [0035]     The oxygen permeable membrane  36  allows dissolved oxygen (and other gases) to diffuse through angstrom-size voids but excludes the larger fuel molecules. Alternatively, or in conjunction with the voids, the permeable membrane  36  utilizes a solution-diffusion mechanism to dissolve and diffuse oxygen (and/or other gases) through the membrane while excluding the fuel. The family of Teflon AF which is an amorphous copolymer of perfluoro-2,2-dimethyl-1,3-dioxole (PDD) often identified under the trademark “Teflon AF” registered to E. I. DuPont de Nemours of Wilmington, Del., USA, and the family of Hyflon AD which is a copolymer of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TDD) registered to Solvay Solexis, Milan, Italy have proven to provide effective results for fuel deoxygenation.  
         [0036]     Fuel flowing through the fuel channel  38  is in contact with the oxygen permeable membrane  36 . Vacuum creates an oxygen partial pressure differential between the inner walls of the fuel channel  38  and the oxygen permeable membrane  36  which causes diffusion of oxygen dissolved within the fuel to migrate through the porous support  42  which supports the membrane  36  and out of the deoxygenator system  14  through the oxygen receiving channel  40  separate from the fuel channel  38 . For further understanding of other aspects of one membrane based fuel deoxygenator system and associated components thereof, attention is directed to U.S. Pat. No. 6,315,815 and U.S. patent application Ser. No.: 6,709,492 entitled PLANAR MEMBRANE DEOXYGENATOR which are assigned to the assignee of the instant invention and which are hereby incorporated herein in their entirety.  
         [0037]     Referring to  FIG. 2B , one set of plates, which forms one flow-channel assembly  34  of the deoxygenator system  14 , includes a flow plate assembly  44  sandwiched adjacent to the oxygen permeable membranes  36  which are supported by a porous support  42  such as non-woven polyester (also illustrated in  FIG. 3 ). It should be understood that the porous substrate, although schematically illustrated, may take various forms. Adjacent one or more assembly  34  is a separator plate  48 . The separator plate  48  prevents fuel from leaking across the predefined fuel passages defined by the flow plate assemblies  34 . The deoxygenation system  14 , irrespective of the number of flow-channel assemblies  34 , is sealed by an interface plate  46  and an outer housing plate  50   a ,  50   b , which respectively include the fuel inlet  26 , the vacuum port  29 , and the fuel outlet  30  (also illustrated in  FIGS. 2A and 2E ).  
         [0038]     The outer housing plates  50   a ,  50   b  are preferably attached together through a multitude of fasteners such as bolts or the like such that the flow-channel assemblies  34  are sandwiched therebetween. The outer housing plates  50   a ,  50   b  are preferably relatively rigid components which compress the flow-channel assemblies  34  such that sealing between plates is maintained thereby. Although illustrated as rectilinear in the illustrated embodiment, one of ordinary skill in the art will recognize that alternative shapes, sizes, or configurations including non-rigid housings are suitable and within the scope of the invention.  
         [0039]     Each flow plate assembly  44  defines a portion of the fuel channel  38  between the inlet  26  and outlet  30 . The vacuum port  29  ( FIG. 2A ) is in communication with the interface plate  46  and the porous support  42  through vacuum ports  29  in the flow plates  52 ,  54 . Vacuum creates a partial pressure gradient within each of the porous supports  42  to extract dissolved oxygen from the fuel channel  38  through the oxygen permeable membrane  36 . The oxygen is then expelled through the vacuum port  29 .  
         [0040]     The specific quantity of flow-channel assemblies  34  are determined by application-specific requirements, such as fuel type, fuel temperature, and mass flow demand from the engine. Further, different fuels containing differing amounts of dissolved oxygen may require differing amounts of deoxygenation to remove a desired amount of dissolved oxygen.  
         [0041]     Each flow plate assembly  44  defines one fuel channel  38  ( FIG. 3 ) between the inlet  26  and outlet  30  ( FIG. 2A ). Preferably a multitude of parallel flow channels  38  are defined between the inlet  26  and outlet  30  by a multitude of the flow-channel assemblies  34  within the deoxygenator system  14 . The configuration of each fuel channel  38  is preferably defined to maximize fuel exposure to the oxygen permeable membrane  36  in order to maximize the amount of dissolved oxygen removed from the fuel. The fuel channels  38  are preferably small enough that fuel is in contact with the oxygen permeable membrane  36  but also large enough so as to not restrict fuel flow.  
         [0042]     Each flow plate assembly  44  includes a first flow plate  52 , a second flow plate  54 , and a flow plate gasket  56  (also illustrated separately in  FIG. 2D ) therebetween. It should be understood that the flow plate assembly  44  disclosed in the illustrative embodiment illustrates only two flow plates and a gasket for the sake of clarity, it should be understood that any number of plate assemblies may be located between the outer housing plates  50   a ,  50   b.    
         [0043]     The first flow plate  52  and the second flow plate  54  are preferably manufactured of a non-metallic material such as a thermoplastic, for instance polyphenylene sulfide (PPS), or more preferably up to 20 wt % carbon fiber filled PPS. The first fuel plate  52  and the second fuel plate  54  are preferably manufactured of a non-metallic material such as KAPTON® film manufactured by E. I. du Pont de Nemours and Company of Delaware USA. It should be understood that other plastics that are compatible with fuel and are electrically conductive (to prevent static charge buildup) may alternatively be utilized as well as materials which are machined rather than molded.  
         [0044]     The first flow plate  52  and the second flow plate  54  include flow impingement elements  55  ( FIGS. 2C and 3 ) which increase oxygen transport. When the flow plates  52 ,  54  are assembled together, the flow impingement elements  55  are interleaved and alternate to provide the fuel channel  38  defined by the flow plates  52 ,  54  with an intricate two-dimensional flow characteristic ( FIG. 4 ). In other words, the flow impingement elements  55  on each flow plate  52 ,  54  extend above the planar surface of their respective flow plates  52 ,  54 . When the flow plates  52 ,  54  are assembled together with the gasket  56  to form the flow plate assembly  44 , the flow impingement elements  55  form a complete fuel channel  38  in which the flow impingement elements  55  from adjacent flow plates  52 ,  54  extend ( FIG. 3 ).  
         [0045]     The flow impingement elements  55  enhance transport of oxygen from the bulk flow to the membrane surface, while the non-metallic material minimizes weight and sharp edges which may otherwise damage the oxygen permeable membranes  36 . The flow impingement elements  55  of the deoxygenator system  14  enhance contact between fuel flow and the composite oxygen permeable membrane  36  to increase mass transport of dissolved oxygen.  
         [0046]     Fuel flowing through the fuel channel  38  is in contact with the oxygen permeable membrane  36 . Vacuum creates an oxygen partial pressure differential between the inner walls of the fuel channel  38  and the composite oxygen permeable membrane  36  which causes diffusion of oxygen dissolved within the fuel to migrate through the porous support  42  which supports the membrane  36  and out of the deoxygenator system  14  through the oxygen receiving channel  40  separate from the fuel channel  38 . For further understanding of other aspects of one membrane based fuel deoxygenator system and associated components thereof, attention is directed to U.S. Pat. No. 6,315,815 entitled MEMBRANE BASED FUEL DEOXYGENATOR; U.S. Pat. No. 6,939,392 entitled SYSTEM AND METHOD FOR THERMAL MANAGEMENT and U.S. Pat. No. 6,709,492 entitled PLANAR MEMBRANE DEOXYGENATOR which are assigned to the assignee of the instant invention and which are hereby incorporated herein in their entirety.  
         [0047]     The first fuel plate  52  and the second fuel plate  54  include flow impingement elements  55  ( FIG. 2 ) which form ridges which increase oxygen diffusivity through fuel agitation.  
         [0048]     Referring to  FIGS. 4A, 4B , each fuel plate  52 ,  54  includes a groove  58  which seals fuel flow on one side  52   a ,  54   a  and an up-standing ridge member  60  on an opposite side  52   b ,  54   b . The groove  58  receives the fuel plate gasket  56  to seal the fuel plate assembly  44  ( FIG. 4C ). It should be understood that in addition to the gasket  56  ( FIG. 3D ), other sealing materials such as adhesive film and epoxy liquid may alternatively or additionally be utilized. The groove  58  and up-standing ridge member  60  are preferably defined about the fuel plates  52 ,  54  in a location which may be fuel leak paths ( FIG. 4D ). The groove  58  and up-standing ridge member  60  are preferably directly opposed such that the fuel plate  52 ,  54  material thicknesses is equivalent throughout. That is, the groove  58  extends into the planar surface  52   a ,  54   a  of the fuel plates  52 ,  54  for a depth generally equivalent to a depth with which the up-standing ridge member  60  extends from the planar surface  52   b ,  54   b  of the fuel plates  52 ,  54 .  
         [0049]     Each fuel plate  52 ,  54  further includes a groove  62  ( FIG. 4E ) which seals vacuum channel on one side  52   a ,  54   a  and an up-stand ridge member  64  on the opposite side  52   b ,  54   b  which receives a fuel plate vacuum gasket  66  ( FIG. 4C ) to seal the fuel plate assembly  44  in a manner similar to that of groove  58  and up-standing ridge member  60 . The groove  62  and up-stand ridge member  64  are preferably defined about the fuel plates  52 ,  54  in a location which may be may be a vacuum leak paths ( FIG. 4E ). It should be understood that although only the fuel plates  52 ,  54  are illustrated in the disclosed embodiment, each plate preferably includes a groove-gasket-upstanding ridge member interface to assure sealing and provide alignment and interlocking during assembly of adjacent plates. The vacuum ports  29  and fuel inlets and outlets  26 ,  29  which provide communication between multiples of fuel plate assemblies  44  ( FIG. 3C ) are respectively located on a long side ( FIG. 4G ) and a short side ( FIG. 4H ) of the deoxygenator system  14  ( FIG. 4F ).  
         [0050]     Laser-cut is one preferred technique to manufacture the high precision sealing gaskets and fuel plates  52 ,  54 . The KAPTON® or other such like non-metallic materials is preferably cut with a computer-controlled, high-tolerance laser such as a CO 2  laser, and a CAD design file of the desired sealing gasket and fuel plate configuration. The laser is programmed to follow the pattern required to cut the sealing gasket and fuel plate fuel channel shape. Laser cutting may be performed either in stages or layers of material, which may then be assembled together, or cutting may be accomplished in a single operation to render a complete fuel plate, e.g fuel plate  52 ,  54  is formed as a single plate. Laser cutting provides a cost-effective manufacturing technique for massive production of high-tolerance sealing gasket and fuel plates. A laser-cut high-tolerance sealing gasket, particularly made with a rubber-type sealing material, provides leak-free assembly. Advantages utilizing laser cut technique for fabricating high-tolerance sealing gaskets and the adjacent fuel plates is particularly relevant to a multilayer FSU assembly ( FIG. 3A ).  
         [0051]     Water jet cutting as generally understood is another effective technique for fabricating high precision FSU seals and fuel plate in accordance with the present invention. Waterjet cutting has absolute repeatability and does not affect material properties or the temperature.  
         [0052]     Electrical discharge machining (EDM) as generally understood is yet another effective technique for fabricating high precision FSU seals and fuel plates in accordance with the present invention. EDM manufacturing is quite affordable and a very desirable manufacturing process when low counts or high accuracy is required.  
         [0053]     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.  
         [0054]     The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.

Technology Classification (CPC): 8