Abstract:
A magnetic valve arrangement for controlling flow of fluid, the magnetic valve arrangement having at least one ferromagnetic element forming a portion of a magnetic circuit, a valve member and a valve seat; the valve member has a passage therethrough for the flow of fluid and is moveable between a first position, in which the valve member abuts the valve seat to restrict a fluid flow, and a second position, in which the valve member is spaced from the valve seat to allow a fluid flow into and through the passage in the valve member, wherein the position of the valve member is dependent on the temperature of the ferromagnetic element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Entry of PCT/GB2008/001695 filed on May 15, 2008, which claims priority to British Appln No. 0711477.0 filed on Jun. 14, 2007, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     The disclosed embodiments relate to a magnetic valve arrangement for controlling flow of fluid. They find particular application in controlling flow of fluid to a component of a gas turbine engine. 
     Components in a gas turbine engine are subject to elevated temperatures, often above the melting point of the material or materials from which they are formed. Hence there is a need for cooling of these components, which is conventionally provided by film or impingement cooling of the hot components using relatively cool air ducted from one or more compressor stages. The extraction of air from the compressor stages reduces the amount of air available as working fluid to be supplied to the combustor and turbines of the gas turbine engine. Typically 5 to 10% of the compressed air at an intermediate pressure compressor stage may be extracted to provide cooling to turbine rotor blades and turbine stator guide vanes of one or more turbine stages. 
     Such cooling systems must be rated for the highest temperature condition in the engine cycle, usually at take-off and maximum climb. However, at other times in the engine cycle, particularly at cruise, less cooling is required. Therefore, it is desirable to modulate the amount of air extracted during these periods to the minimum required to provide adequate cooling. Thus, more air remains as working fluid in the gas turbine engine and hence more output power is achieved. 
     One known method of modulating the flow of cooling fluid, depending on the engine cycle condition, is detailed in EP 1,632,649 and comprises a magnetic valve located in the cooling air supply conduit. The magnetic valve has at least one member that comprises a ferromagnetic material. The valve has a first configuration in which the valve at least partially restricts the supply conduit and a second configuration in which the supply conduit is substantially unrestricted. The configuration of the valve is dependent on the temperature of the ferromagnetic material. 
     In one embodiment of this related art, shown in  FIG. 1 , the ferromagnetic material  14  is a valve member located within an enlarged portion of a supply conduit  12  and in thermal contact, therefore, with the flow of a cooling fluid shown by arrow  16 . A permanent magnet  18 , or an electromagnet, surrounds the enlarged portion of the supply conduit  12  so that, when the ferromagnetic material  14  is below its Curie temperature, the ferromagnetic material valve member  14  at least partially restricts the flow of cooling fluid  16 . When the temperature of the fluid, and therefore of the ferromagnetic material valve member  14 , increases towards the Curie temperature of the valve member  14 , the valve member  14  loses its magnetism and is pushed along the conduit  12  by fluid pressure or another mechanism. Stops  20  may be provided to support the valve member  14  such that the fluid flow  16  is substantially unrestricted through the conduit  12 . 
     One problem with this method of modulating the cooling fluid flow is that the ferromagnetic valve member presents a large surface area to the fluid flow. This means that the magnets that hold the ferromagnetic valve member against the flow must be large and/or additional means, such as a spring, must be provided to enable the ferromagnetic valve member to resist the fluid flow and at least partially restrict the supply conduit when the ferromagnetic valve member is below its Curie temperature. 
     Another problem with this method of modulating the cooling fluid flow is that the ferromagnets required to provide sufficient force to resist the fluid pressure are large. This means that they have a large thermal inertia and, therefore, the response time of the valve is relatively long; typically of the order of a few seconds. In some applications, particularly within gas turbine engines, this is unacceptably long. 
     A further problem with this method of modulating the cooling fluid flow is that the valve components are bulky and heavy. In some applications, particularly within the core of a gas turbine engine, there is little space to accommodate additional components and weight is critical. 
     SUMMARY 
     The present invention seeks to provide a magnetic valve arrangement that seeks to address the aforementioned problems. 
     Accordingly the present invention provides a magnetic valve arrangement for controlling flow of fluid, the magnetic valve arrangement having at least one ferromagnetic element forming a portion of a magnetic circuit, a valve member and a valve seat; the valve member has a passage therethrough for the flow of fluid and is moveable between a first position, in which the valve member abuts the valve seat to restrict a fluid flow, and a second position, in which the valve member is spaced from the valve seat to allow a fluid flow into and through the passage in the valve member, wherein the position of the valve member is dependent on the temperature of the ferromagnetic element. 
     Preferably at least a portion of the valve member comprises a part of the magnetic circuit. More preferably, it comprises the ferromagnetic element. Even more preferably, the valve member comprises a tube. 
     Preferably a permanent magnet or electromagnet forms a portion of the magnetic circuit. More preferably the permanent magnet or electromagnet is coaxial with the valve member. 
     Preferably the valve member has its axis of symmetry perpendicular to a direction of fluid flow in the fluid conduit. 
     Preferably the magnetic valve arrangement further comprises sealing means. More preferably the sealing means is a sliding seal between the tube element and a wall of the fluid conduit. Alternatively the sealing means is at least one poppet valve seal. 
     Preferably the magnetic valve arrangement further comprises at least one locating feature. Preferably the locating feature is a leaf spring or Belleville washer. 
     Preferably the ferromagnetic element is thermally coupled to the flow of fluid in the fluid conduit. Alternatively the ferromagnetic element is thermally coupled to a second fluid. The thermal coupling may be by means of at least one duct to deliver fluid to the ferromagnetic element. Alternatively the ferromagnetic element is thermally coupled to a component. 
     One aspect of the present invention provides a gas turbine engine including a magnetic valve. The ferromagnetic element may be thermally coupled to a component of the gas turbine engine. The component of the gas turbine engine may be thermally coupled to the flow of fluid. 
     Preferably the flow of fluid from the fluid conduit is directed to a component of a gas turbine engine. Alternatively or additionally, the flow of fluid from the fluid conduit is directed to re-enter the fluid conduit. 
     Preferably the fluid conduit is substantially restricted when the ferromagnetic element is above or near its Curie temperature. Alternatively the fluid conduit is substantially restricted when the ferromagnetic element is below its Curie temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully described by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic side view of a magnetic valve according to the related art. 
         FIG. 2  is a schematic side view of a gas turbine engine incorporating a magnetic valve according to the present invention. 
         FIG. 3  is a schematic side view of an exemplary embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 4  is a schematic side view of an exemplary embodiment of a magnetic valve arrangement according to the present invention in a second configuration. 
         FIG. 5  is a schematic side view of a second embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 6  is a characteristic plot of distance and force for a related art magnetic valve and a magnetic valve according to the present invention. 
         FIG. 7  is a schematic side view of a third embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 8  is a schematic side view of a fourth embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 9  is a schematic side view of a fifth embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 10  is a schematic side view of a sixth embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 11  is a schematic side view of a seventh embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
         FIG. 12  is a schematic side view of an eighth embodiment of a magnetic valve arrangement according to the present invention in a first configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A gas turbine engine  100  is shown in  FIG. 2  and comprises an air intake  102  and a propulsive fan  104  that generates two airflows A and B. The gas turbine engine  100  comprises, in axial flow A, an intermediate pressure compressor  106 , a high pressure compressor  108 , a combustor  110 , a high pressure turbine  112 , an intermediate pressure turbine  114 , a low pressure turbine  116  and an exhaust nozzle  118 . A nacelle  120  surrounds the gas turbine engine  100  and defines, in axial flow B, a bypass duct  122 . Air may be extracted from a compressor stage  106 ,  108 , or the bypass duct  122  and be selectively passed to a turbine stage  112 ,  114 ,  116  for cooling the turbine stage  112 ,  114 ,  116  via a magnetic valve arrangement according to the present invention. 
     An exemplary embodiment of the present invention is shown in  FIG. 3 . A fluid conduit  22  is defined on a first side, in this example an upper side, by a first wall  24  and on a second side, in this example a lower side, by a second wall  34 . The fluid conduit  22  is arranged so that fluid flows towards a central portion, as shown by arrows  26 . The first wall  24  is provided with an aperture  25  which extends perpendicularly through the first wall  24  in the central portion of the fluid conduit  22 . A valve member tube  28  is positioned in and located by the aperture  25  and extends perpendicularly through the first wall  24 . The tube  28  comprises a ferromagnetic material. A seal  30  is arranged between the tube  28  and the first wall  24 ; for example the seal  30  is a lip, labyrinth or o-ring seal. The seal  30  may also act as a locating feature or a separate locating feature may be used. An annular, or ring, permanent magnet  32 , or electromagnet, is located above the first wall  24 , outside the fluid conduit  22  in this example, and surrounds the ferromagnetic tube  28 . Thus the permanent magnet  32  is coaxial with the tube  28 . The tube  28  has a first (upper) end  27  outside the fluid conduit  22  and a second (lower) end  29  within the fluid conduit  22 . 
     When the ferromagnetic tube  28  is near or above its Curie temperature it loses its magnetic properties and the tube  28  moves, by gravity or another mechanism such as a spring (not shown), such that the second end  29  of tube  28  seals against a valve seat portion  35  of the second wall  34  of the fluid conduit  22 . Therefore, no fluid can flow into the tube  28  from the fluid conduit  22  and, hence, the fluid conduit  22  is substantially restricted and the magnetic valve is closed. 
     When the ferromagnetic tube  28  is cooled below its Curie temperature it becomes magnetic and therefore the first end  27  of the tube  28  is attracted to the permanent magnet  32 . This is the configuration shown in  FIG. 4 . Hence, there is a clearance  36  between the second wall  34  of the fluid conduit  22  and the second end  29  of the tube  28 . The flow of fluid  26  in the fluid conduit  22  is thus able to pass through the clearance  36  and through the centre bore  31  of tube  28 . The fluid can then be ducted or otherwise transported to a component to be cooled or a component or system requiring fluid. 
     There are several advantages to providing a tube  28  as the valve member of the magnetic valve arrangement, Firstly, the tube  28  has a small surface area in the direction of fluid flow  38  when the valve is open. This means that less force is generated in the vertical direction and so a smaller permanent magnet  32  is required to effect the movement of the tube  28  or the tube  28  can move a greater distance vertically and therefore offer more clearance  36  for the fluid flow  26 ,  38 . Secondly, the tube  28  is a strong and rigid shape and allows the use of a thin walled tube. Thus, there is little thermal inertia associated with a thin walled tube  28  and the valve can react more quickly than related art arrangements. Thirdly, the whole of the tube  28  need not be ferromagnetic. 
       FIG. 5  shows an embodiment of the present invention in which the tube  28  comprises a non-magnetic second portion  40  at the second end  29 , nearest the second wall  34  of the fluid conduit  22  and a ferromagnetic first portion  42  at the first end  27 , nearest the coaxial, annular permanent magnet  32 . Alternatively, the tube  28  may comprise a non-magnetic material at both ends  27 ,  29  and a ferromagnetic portion in its central region, appropriately near the permanent magnet  32 . 
     Due to the shape of the permanent magnet  32 , the ferromagnetic tube  28  experiences a more emphasised change in flux as it moves between the first and second configurations (e.g.  FIG. 3  and  FIG. 4 ) of the magnetic valve arrangement. This provides a variable reluctance to achieve the moving force and therefore a greater operating range for the tube  28 . A schematic plot of this is shown in  FIG. 6  in which the curve C is a typical characteristic for a related art magnetic valve and the curve D is a typical characteristic for the magnetic valve arrangement of the present invention. It is clear that a magnetic valve with characteristic curve D experiences no force when the tube is precisely aligned with the surrounding magnet. However, there is a useable amount of force generated over a much greater distance than for the related art magnetic valve with a characteristic curve C. 
     Although the seal  30  has been described as a locating feature between the first wall  24  and the tube  28  it may equally be a leaf spring, a Belleville washer or another locating feature arrangement. There may be locating features at more than one location. These locating features may be the same or different types. 
     Additional or alternative sealing arrangements to seal  30  may be used, such as lip, labyrinth, o-ring or poppet valve seals. There may be sealing at more than one location, for example at the lower edge of the first wall  24  and at the upper edge of the permanent magnet  32 . These multiple seals  30  may be the same or different types of seal. There may also be additional sealing  44  between the second end  29  of the tube  28  and the second wall  34  of the fluid conduit  22 . 
       FIG. 7  shows an embodiment of the present invention in which the second end  29  of the tube  28  is provided with a skirt  46  extending outwardly. The valve seat  35  of the second wall  34  of the fluid conduit  22  has an arcuate recessed portion  48  into which the skirt  46  seats to improve the sealing of the tube  28  against the second wall  34  of the fluid conduit  22 . 
     The embodiments described hereinbefore all have at least a part of the tube  28  comprising ferromagnetic material and a permanent magnet  32 , or an electromagnet, surrounding a part of the tube  28 . The advantages of the present invention may be equally achieved by reversing the positions of the ferromagnetic material and magnetic material.  FIG. 8  shows an embodiment of the present invention in which at least a part of the tube  50  comprises a permanent magnet and there is an annular ferromagnet  52  surrounding it and coaxial with it. 
     The arrangement of  FIG. 8  enables the ferromagnet  52  to be heated or cooled by a variety of sources. In the previously described embodiments the ferromagnetic tube  28  is heated or cooled by the fluid flow  26 . In the arrangement of  FIG. 8  the ferromagnet  52  may be heated or cooled by this fluid flow  26 , or by a ducted portion thereof. However, it may also be heated or cooled by another fluid flow  54  from a different source, which may be relatively distant from the magnetic valve arrangement. Alternatively, it may be heated or cooled by being thermally coupled to the component that requires the fluid flow, or to another component. For example, thermally conductive tracks (not shown), possibly comprising ferromagnetic material for at least part of their length, may link a component and the ferromagnet  52  to cause the magnetic valve arrangement to operate dependent on the thermal condition of a relatively remote component. 
     These alternative methods of changing the temperature of the ferromagnetic element can equally be used in any of the described embodiments of the present invention. 
       FIG. 9  shows an embodiment of the present invention in which additional components are provided. An end stop  56  is provided extending inwardly from the permanent magnet  32  and the end stop  56  is provided with a central aperture  58  to permit the fluid flow to pass. Preferably, the end stop  56  is not magnetic, so as not to upset the flux patterns. Alternatively, the end stop  56  may be magnetic and appropriate compensation be made for the flux variations. A cylindrical mounting block  60  is provided within the tube  28 , a short distance below the first end  27  of the tube  28 . The mounting block  60  protrudes from the internal surface of the tube  28  but has an aperture  62  to permit the fluid to pass. A spring  64  is provided between the mounting block  60  and the end stop  56 . The spring  64  provides a biasing force that can be arranged either to close or to open the valve arrangement. Alternatively, the mounting block  60  may project from the external surface of the tube  28  and the spring  64  may be located adjacent the external surface of the tube  28  in the gap  66  sealed by seal  30 . 
     A sixth embodiment of the magnetic valve arrangement of the present invention is shown in  FIG. 10 . The permanent magnet  32  again includes an end stop  56  extending inwardly and having an aperture  58  centrally to permit fluid flow when the valve is in an open configuration. A poppet valve  70  is provided that extends outwardly from the walls of the tube  28  and is arranged to sit between the first wall  24  and the permanent magnet  32 . The poppet valve  70  seals against the first wall  24  when the valve is in the closed configuration so that the incoming fluid flow  26  is isolated from the outward fluid flow  72 . Thus, secondary sealing, such as by seal  30  from  FIG. 3 , is unnecessary. The poppet valve  70  may additionally or alternatively be further arranged to seal against the permanent magnet  32  when the magnetic valve arrangement is in the open configuration. This, therefore, directs fluid flow through the gap  66  between the tube  28  and the first wall  24  and distributes the fluid outwardly in the directions shown by arrows  72 . This flow  72  may subsequently be directed towards one or more components of the gas turbine engine that require the fluid for cooling or another purpose. This component or components may be the same as that supplied by the fluid exiting the first end  27  of the tube  28  or may be a different component or components. Alternatively, the flow  72  may be directed back into the fluid conduit  22  upstream of the tube  28 . Optionally, the arrangement shown in  FIG. 10  may also include a spring (not shown), similar to spring  64  in  FIG. 9 , extending between the poppet valve  70  and the end stop  56 . 
     The embodiment shown in  FIG. 10  also includes an alternative sealing arrangement at the second end  29  of tube  28 . The valve seat  35  of the second wall  34  of the fluid conduit  22  is a raised portion  68  that protrudes towards the tube  28  and is dimensioned and shaped to seat closely within the second end  29  of the tube  28  when the valve is in the closed configuration to provide sealing. When the valve is in the open configuration the raised portion  68  does not significantly impede fluid flow from the fluid conduit  22  into, and through, the central bore  31  of the tube  28 . 
     It is preferable, in the embodiment shown in  FIG. 10 , to design the components of the magnetic valve arrangement to provide the same effective diameter for fluid ingress and egress, namely through the second end  29  of the tube  28  and the combination of through the first end  27  of the tube  28  and adjacent the poppet valve  70 . If these two areas have the same effective diameter there is no net pressure on the tube  28 . However, it may be preferable to design different effective diameters so that there is a pressure difference between the two ends of the tube  28  as this will assist the magnetic valve arrangement to switch between the closed and open configurations as the ferromagnetic element (being the tube  28  in the illustrated embodiment) begins to lose its magnetism. This is earlier than without the assistance of the pressure difference and therefore results in a more rapid response time, in contrast to the related art. This arrangement may additionally or alternatively mean that less magnetic force is required to actuate the valve and hence smaller magnetic components may be used. 
     A seventh embodiment of the present invention is shown in  FIG. 11 . In this arrangement the tube  28  is non-magnetic and has, at its first (upper) end  27 , a C-shaped annular ferromagnetic portion  74 . The outwardly facing protrusions of this C-shaped ferromagnetic portion  74  correspond to similar, inwardly facing protrusions at the upper and lower extents of the annular, coaxial permanent magnet  32 . The purpose of the protrusions is to preferentially concentrate, or guide, the flux and therefore increase the available force. This again provides the advantages of offering a greater range of movement of the tube  28  and/or reducing the size of permanent magnet  32  that is required to effect that movement. 
     It will be understood by the skilled reader that the fluid may be any suitable fluid. The magnetic valve arrangement of the present invention finds particular application in selectively providing cooling to one or more components of a gas turbine engine, for example during take off but not cruise of an aircraft powered by the engine, and in this case the fluid would typically be air extracted from a compressor stage or the bypass flow. Alternatively, it may be ambient air or a working fluid, for example fuel or oil. The invention has equal utility in selectively providing heating, for example for anti-icing or assisting during cold starting of the engine, and the fluid may therefore be exhaust gases, air extracted from a turbine stage or air passed through a heat exchanger. Alternatively, it may be heated or re-circulated fuel or oil, or another fluid. In other applications other fluids may be more appropriate, for example cryogenic fluids, provided that the fluid and materials used to construct the magnetic valve arrangement are compatible. 
     The magnetic valve of the present invention also has utility as a safety valve, whether to cut off a fluid flow above a given temperature or to provide a fluid flow, particularly a cooling flow, above a given temperature. Alternatively the magnetic valve acting as a safety valve may control a heating flow. The magnetic valve may be controlled by the same flow that is provided to the component, heating or cooling, or by a different flow or by thermal coupling to the same component or a different component. 
     The magnetic valve of the, present invention can be arranged as a two-way valve, as shown in  FIG. 12 , and used in one of two ways. The arrangement in  FIG. 12  is substantially the same as in  FIG. 10  except that poppet valve  70  is located intermediate the first wall  24  and the permanent magnet  32  such that the poppet valve  70  abuts the permanent magnet  32  when the valve is in the open configuration. Additional sealing  76  is provided between the first end  27  of the tube  28  and the permanent magnet  32 . In the first way of using the two-way valve, a single fluid flow  26  is provided to one of two different components, or component groups, depending on the temperature of the ferromagnetic tube  28 . Hence, when the valve is in the closed configuration incoming fluid flow  26  is directed through gap  66  and outward as fluid flow  72 . When the valve moves to the open configuration incoming fluid flow  26  is able to flow through the central bore  31  of the tube  28  and thence exit as fluid flow  78  through aperture  58 . Optionally secondary sealing  80 , in the form of a poppet valve, may be provided to ensure the fluid flow only exits through aperture  58  as fluid flow  78 . Omitting this secondary sealing  80  enables fluid egress as fluid flow  72  in the open and closed configurations. In the second way of using the two-way valve the fluid flows  26 ,  72 ,  78  are reversed. Thus one of two different fluid flows  72 ,  78  (reversed) are provided to a single component via a single fluid flow  26  (reversed) depending on the temperature of the ferromagnetic tube  28 . 
     Although each embodiment of the present invention has been described with specific features, it will be understood that several of these features are interchangeable between the different embodiments. For example, the seal  30  shown in  FIG. 11  could be replaced or supplemented by the raised portion  68  of  FIG. 10 , a poppet valve in one or more of the locations discussed herein, the skirt  46  shown in  FIG. 7 , a leaf spring, a Belleville washer or any other known sealing arrangement. Similarly, although most of the embodiments are shown with the tube  28  at least partially comprising the ferromagnetic element and a permanent magnet  32 , or electromagnet, surrounding it, the skilled reader will understand that these may be reversed if appropriate to the application contemplated. 
     Preferably the ferromagnetic tube is circular in cross-section and the permanent magnet is annular. Alternatively the tube may have any other suitable cross-sections e.g. square, rectangular, hexagonal. 
     Although the present invention has been contemplated with respect to applications in the gas turbine engine industry it may be used in other industries including, but not limited to, automotive, airframe, air-conditioning and power generation. Alternatively it may find application in other industries, for example in medical applications such as dialysis.