Abstract:
A high pressure valve assembly ( 10 ) comprising a valve sleeve ( 14 ) and a valve body ( 16 ) slidably mounted in the valve sleeve ( 14 ) is disclosed, the valve body ( 16 ) and valve sleeve ( 14 ) each having first ends ( 18, 56 ) and second ends ( 20, 58 ). A sidewall ( 22 ) extends between the valve sleeve first end ( 18 ) and second end ( 20 ) which sidewall ( 22 ) has an inner surface ( 24 ) and an outer surface ( 26 ) and at least one opening ( 30 ) therethrough. The sidewall ( 22 ) also includes at least one channel ( 40 ) having a first end ( 42 ) facing the inner surface ( 24 ) at a first location closer to the first valve sleeve end ( 18 ) than to the second valve sleeve end ( 20 ) and a second end ( 44 ) facing the inner surface ( 24 ) at a second location closer to the second valve sleeve end ( 20 ) than to the first valve sleeve end ( 18 ). A method of using the valve assembly ( 10 ) is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of U.S. Provisional Patent Application No. 60/492,301, filed Aug. 5, 2003, the entire contents of which is hereby incorporated by reference. 
     
    
       [0002]     This invention was made with Government support under Contract No. N00019-02-C-3003 awarded by the United States Navy. The Government has certain rights in this invention. 
     
    
     FIELD OF THE INVENTION  
       [0003]     This invention relates to a valve for high pressure applications, and, more specifically, to a valve for a high pressure fluid metering system that reduces matched clearance leakage between a valve body and a valve sleeve.  
       BACKGROUND OF THE INVENTION  
       [0004]     Fluid metering systems requiring high accuracy flow, such as fuel metering systems for gas turbine engines, often use a servo-controlled throttling valve to maintain a constant pressure delta (head pressure) across a metering orifice. In such systems, a supply of burn fuel is directed against a first side of a throttling valve, and the position of a valve body in the throttling valve controls the amount of fuel that leaves the valve outlet.  
         [0005]     A servo may be used to create a control pressure (“PX pressure”) for positioning the valve body to vary the flow rate through the valve. In high pressure systems, the fluid conveying the control pressure against the valve body may leak between the valve body and the valve sleeve and into the valve outlet. This “matched clearance servo leakage,” adds to the amount of servo flow required for the valve to hold position, as well as, adding to the measured volume of burn fuel that passes through the valve outlet. Because this leakage is somewhat unpredictable—it varies with temperature and operating conditions, for example, it is often a large contributor to metering system inaccuracy.  
         [0006]     In order to control matched clearance leakage, one known throttling valve includes a dual outer diameter valve body and a dual inner diameter valve sleeve.  FIG. 6  illustrates a conventional dual-diameter throttle valve assembly  210  comprising a valve housing  212  and a valve sleeve  214  in which a valve body  216  is slidably mounted. Valve sleeve  214  includes a first inner diameter  218  and a second inner diameter  220  while valve body  216  includes a first outer diameter  222  corresponding to valve sleeve first inner diameter  218  and a second outer diameter  224  corresponding to valve sleeve second inner diameter  220 . Seals  226  and  270  control leakage from the supply flow path  286  and a leakage control port  228  during shutoff. The leakage control port  228  ports supply pressure to a center area between the valve body and the valve sleeve to reduce the pressure differential between the control pressure flow path  290  and the outlet flow path  288  to reduce servo leakage.  
         [0007]     System requirements typically call for drip-tight shutoff leakage on throttle valves. Not only is the dual-diameter matched valve assembly expensive to manufacture, but it is extremely difficult to achieve the low leakage or drip-tight shutoff sealing required in some applications with this valve. In the dual-diameter configuration, it is also extremely difficult to install a durable drip-tight seal in the upper seal diameter, because the seal  226  must be stretched when it is installed and re-sized after installation. Moreover, burn fuel from the supply flow path  286  which supplies flow to leakage control port  228 , tends to contain more impurities than fuel from the control supply flow path  290  which has generally been more thoroughly filtered. Seal  226  is exposed to the burn fuel, and these impurities may tend to collect around seal  226 , thus degrading performance of the seal and interfering with a drip-tight shutoff. It is therefore desirable to provide a valve assembly that does not suffer from the above-described shortcomings.  
       SUMMARY OF THE INVENTION  
       [0008]     These shortcomings and others are addressed by the present invention which, in a first aspect, comprises a valve assembly of a fluid metering system. According to another aspect, the present invention is directed to a fluid metering system using a valve assembly described herein. One embodiment of the present invention utilizes a valve assembly with a channel in the valve sleeve to port metered flow pressure to an annulus to reduce the servo side matched clearance leakage to near zero. In one implementation, the valve of the valve assembly has a single diameter. This single diameter valve approach opens up numerous options, particularly for the upper seal design, making it much easier to achieve low leakage or drip-tight shutoff.  
         [0009]     Another aspect of the invention comprises a high pressure valve having a valve sleeve and a valve body slidably mounted in the valve sleeve. A sidewall extends between the first and second ends of the valve sleeve and has an inner surface, an outer surface and at least one opening therethrough. The sidewall also includes at least one channel having a first end facing the inner surface at a first location closer to the first valve sleeve end than to the second valve sleeve end and a second end facing the inner surface at a second location closer to the second valve sleeve end than to the first valve sleeve end.  
         [0010]     An additional aspect of the invention comprises a gas turbine engine throttle valve assembly including a throttle valve having a first end and a second end and comprising a valve sleeve and a valve body slidably mounted in the valve sleeve. A supply flow path delivers a supply fuel flow against the first end of the throttle valve to shift it between a first position blocking the at least one opening in the sidewall and a second position exposing at least a portion of the at least one opening to the supply fuel flow. A control flow path delivers a control fluid against the second end of the throttle valve and into a space between the valve body and a circumferential end section of the valve sleeve when the valve body is in the second position. The valve also includes a passage allowing communication between the supply fuel flow and the space between the valve body and the valve sleeve circumferential end section when the valve body is in the second position and substantially preventing communication between the supply fuel flow and that space when the valve body is in the first position.  
         [0011]     Another aspect of the invention comprises a method of controlling fuel flow in a gas turbine engine that includes providing a throttle valve comprising a valve sleeve and a single diameter valve body slidably mounted in the valve sleeve. The valve sleeve has a sidewall comprising a first end and a second end, a central circumferential section including at least one opening, a first circumferential section lying between the first end and the central circumferential section and a second circumferential section lying between the second end and the central circumferential section. A supply fuel under pressure is directed against the first end of the throttle valve and a control fluid under pressure is directed against the second end of the throttle valve and into a space between the valve body and the valve sleeve second circumferential section. The valve body is shifted from a first position blocking the at least one opening to a second position exposing at least a portion of the at least one opening to the supply fuel. A portion of the supply fuel is allowed to enter the space between the valve body and the second circumferential section when the valve is in the second position.  
         [0012]     In another aspect, the invention comprises a method of controlling a gas turbine engine throttle valve outlet flow that involves providing a throttle valve comprising a valve sleeve and a single diameter valve body slidably mounted in the valve sleeve. The valve sleeve has a sidewall having a first end and a second end, a central circumferential section including at least one opening, a first circumferential section lying between the first end and the central circumferential section and a second circumferential section lying between the second end and the central circumferential section. A supply fuel under pressure is directed against the first end of the throttle valve and a control fluid under pressure is directed against the second end of the throttle valve and into a space between the valve body and the valve sleeve second circumferential section. Fluid flow through the at least one opening is prevented by shifting the valve body into a first position and fluid flow is allowed through a passageway connecting the first circumferential section to the second circumferential section when the valve body is in the second position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above and other aspects and features of the invention will be better understood after a reading of the following detailed description of the invention in connection with the drawings wherein:  
         [0014]      FIG. 1  is a cross sectional view of a valve according to a first embodiment of the present invention in a first, closed position;  
         [0015]      FIG. 2  is a cross sectional view of the valve of  FIG. 1  in a second, partially open position;  
         [0016]      FIG. 3  is a cross sectional view the valve of  FIG. 1  in a third, open position;  
         [0017]      FIG. 4  is an exploded perspective view of the valve of  FIGS. 1-3 ;  
         [0018]      FIG. 5  is a cross sectional view of a valve according to a second embodiment of the present invention; and  
         [0019]      FIG. 6  is a cross sectional view of a conventional dual-diameter valve. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Referring now to the drawings, wherein the showings are for purposes of illustrating preferred embodiments of the invention only, and not for purposes of limiting same,  FIG. 1  shows a valve assembly  10  comprising a valve housing  12  and a valve sleeve  14  in which a valve body  16  is slidably mounted. Valve sleeve  14  includes a first end  18  and a second end  20  and a sidewall  22  extending between first end  18  and second end  20  having an inner wall  24  and an outer wall  26 . A central circumferential sidewall section  28  includes a plurality of openings  30  that extend completely through side wall  22 . Valve sleeve sidewall  22  further include a first circumferential section  32  extending from first end  18  of valve sleeve  14  to second circumferential section  28  and a second circumferential section  34  between second end  20  of valve sleeve  14  and central circumferential section  28 .  
         [0021]     Several circumferential grooves are formed in inner wall  24  of valve sleeve  14  including a primary circumferential groove  36  and several auxiliary circumferential grooves  38 . Side wall  22  further includes a leakage control channel  40  having a first end  42  extending through inner wall  24  in first circumferential section  32  and a second end  44  extending through inner wall  24  in second circumferential section  34 . A plurality of these channels  40  are provided between pairs of openings  30 ; only one is visible in  FIGS. 1 and 4 .  
         [0022]     Valve assembly  10  further includes a flow deflector  46  surrounding valve sleeve  14 . A spacer  48  surrounds flow deflector  46  and a portion of valve sleeve  14 , and an O-ring seal  50  is provided in a channel  45  in outer wall  26  of valve sleeve  14 . Cover  49  helps retain these elements in valve housing  12 . The spacer  48  also includes a channel  52  in which a seal  53  for forming a seal between spacer  48  and valve housing  12  is provided.  
         [0023]     Valve body  16  has a first end  56  and a second end  58 , a first bore  60  extending into first end  56 , and a second bore  62  extending into second end  58 . A wall  64  separates first bore  60  from second bore  62 .  
         [0024]     Valve assembly  10  further comprises a lower seal seat  66  that includes a channel  68  retaining a seal  70 . First end  18  of valve sleeve  14  engages lower seal seat  66 , and first end  56  of valve body  16  engages seal  70  when the valve assembly  10  is in a first, or closed, configuration shown in  FIG. 1 . Valve assembly  10  also includes an upper seal seat  72 , which may be formed of Teflon, for example, that includes an annular portion  74  having a channel  76  holding a seal  78  and a projecting portion  80  extending into second bore  62  in valve body  16  that includes an end wall  82  having an opening  84 .  
         [0025]     A supply flow path  86  brings a supply of burn fuel to valve assembly  10 , which burn fuel exits the valve assembly  10  along an outlet path  88 . A control fluid is directed against the second end of the valve assembly  10  via a control flow path  90 . In one specific implementation of the principles of the present invention, the valve assembly  10  is designed for operation at supply flow path pressures of approximately 2000 psig with an outlet flow path pressure of approximately 50 psig. A typical, conventional, single diameter valve for such an application would have matched clearance leakage from the control flow path  90  to the outlet flow path  88  ranging from 15 pph to 120 pph depending on tolerances and temperature conditions. A conventional single diameter valve would not only be inaccurate, but might also fail to function under these extreme conditions.  
         [0026]     In operation, a control fluid provided via control flow path  90  is directed against the second end of the valve sleeve  14 . The force of the control fluid, together with the force provided by biasing spring  92  which extends between upper seal seat  72  and cover  49 , biases valve body  16  in a first direction toward lower seal seat  66 , to the left as viewed in  FIG. 1 . Supply or burn fuel is provided via supply flow path  86  against first end  56  of valve body  16  which pressure is greater than the control pressure, and therefore tends to move valve body  16  in a second direction, toward the right as viewed in  FIG. 1 . As valve body  16  moves in the second direction, first end  56  of valve body  16  moves past first end  42  of leakage control channel  40  into the position illustrated in  FIG. 2 , and allows the supply or burn fuel to flow through leakage control channel  40  from first circumferential section  32  to primary circumferential groove  36  in second circumferential section  34 . As valve body  16  continues to move in the second direction, first end  56  of the valve body  16  passes an edge of opening  30  in side wall  22  of valve sleeve  14 , as illustrated in  FIG. 3 , and allows the supply fuel flow to pass through opening  30  and into the outlet flow path  88 .  
         [0027]     As will be appreciated from  FIGS. 1-3 , as valve body  16  moves in a second direction, it forces annular portion  74  of upper seal seat  72  away from engagement with valve sleeve  14 . The junction between valve body  16  and valve sleeve  14  is therefore exposed to the high pressure control fluid in control fluid flow path  90 . While the outer diameter of valve body  16  is substantially identical to the inner diameter of valve sleeve  14 , high pressure control fluid tends to leak between these two elements and into auxiliary circumferential grooves  38 . High pressure burn fuel, however, begins filling primary circumferential channel  36  soon after valve body  16  lifts off lower seal seat  66 . The presence of this supply fluid in primary circumferential groove  36  reduces the pressure difference between control flow path  90  and the space between valve body  26  and central circumferential section  28  of valve sleeve  14  enough to substantially prevent control fluid from leaking from control flow path  90  into output flow path  88 . In one embodiment of the invention, the pressure difference between the control flow path  90  and the outlet flow path  88  is reduced to about 40 psi which produces a leakage of about 3 pph. Moreover, any fluid that leaks from primary circumferential channel  36  into the space between central circumferential section  28  and valve sleeve  14  will come from leakage control channel  40 , and thus will comprise a portion of supply fuel arriving from supply flow path  86 , which has already been metered. This leakage will therefore not adversely affect the flow rate through outlet flow path  88 .  
         [0028]     To stop fuel flow through outlet flow path  88 , the control pressure in control flow path  90  is increased to drive upper seal seat  72  in the first direction until seal  78  engages the junction between valve body  16  and valve sleeve  14  and valve body  16  first end  56  engages seal  70  in lower seal seat  66  as illustrated in  FIG. 1 . This provides for drip-tight shut off by valve assembly  10 , a substantial improvement over the prior art.  
         [0029]     A second embodiment of the subject invention is shown in  FIG. 5  wherein like numerals are used to identify parts identical to the first embodiment. Valve assembly  100  shown in  FIG. 3  includes a valve body  102  having a first bore  104  in a first end  106  substantially shallower that first bore  60  in the valve body  16  of the first embodiment, and a second bore  108  in a second end  110  of the valve body  102  that is substantially deeper than second bore  62  of valve body  16  of the first embodiment. In this embodiment, the seal seat  112  includes an end wall  114  that, unlike end wall  82  of the upper seal seat  72  of the first embodiment, lacks a through opening. Pressure channels  116  are provided in the side walls of valve body  102 . This embodiment ports the relatively low outlet pressure  88  between the seal seat  112  and the valve body  102 . The low pressure in this area increases the clamping force between the seal seat  112  and the valve body  102 , as well as, improving the seal retention and valve deflection.  
         [0030]     While the subject invention has been described in terms of specific embodiment, obvious variations will become apparent to those skilled in the relevant arts and such variations comprise a part of the subject invention to the extent they fall within the scope of the several claims appended hereto.