Abstract:
A check valve is provided that includes a valve housing that has a side wall and a flow path therethrough, the side wall defining the flow path. The flow path includes an inlet, an outlet, and a centerline extending between the inlet and the outlet. At least one control member is positioned in the flow path and movable between a first position, wherein fluid flow through the valve housing is substantially prohibited and a second position wherein fluid flow is permitted. The side wall includes a stop configured to limit movement of the at least one control member at a pre-determined stop angle relative to the flow path centerline.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engines and more particularly, to engine bleed air systems used with gas turbine engines.  
         [0002]     Gas turbine engines used in aircraft propulsion systems typically include a bleed air system that routes air from a compressor section of the engine to an environmental control system (ECS) on the aircraft. For example, in at least some engines, bleed air is bled from the compressor through holes or ports formed in the compressor housing. However, bleed air routed from the compressor section is generally at a higher pressure and temperature than desired for use by the ECS, and is therefore conditioned prior to use. More specifically, at least some known ECS include various components, such as regulating valves and heat exchangers, to condition the bleed air for use by the ECS.  
         [0003]     Because the pressure of air bled from a specific bleed port may change significantly as engine operating conditions change, it may not be possible, without undue complexity and costs, to provide exactly the correct pressure to the ECS from the same bleed port. Accordingly, at least some known compressors include a plurality of bleed ports positioned at more than one location in the compressor, and also a plurality of external valves to control the flow of bleed air. Typically, such control valves include at least one check valve that includes flapper doors that permit air flow in only one direction through the doors when the doors are in an open position. When closed, the doors inhibit air flow in the opposite direction. Typically, the flapper doors pivot or rotate on a pin that extends across the valve.  
         [0004]     During engine operation, the check valves may be subjected to vibrational stresses induced by the engine and/or excitation from the bleed air stream. For example, with known check valves, when the check valve flapper doors are open, the doors may be subjected to a flutter condition that may cause the flapper doors to vibrate against a stop. Over time, continued exposure to the vibrational stresses may damage the valve pin and/or may limit the useful life of the check valve.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In one aspect, a method for extracting bleed air from a gas turbine engine including a compressor is provided. The method includes coupling a first end of a bleed duct to a bleed port to enable fluid to be extracted from the compressor of the engine, coupling a second end of the bleed duct to a check valve having a cross sectional flow area at an outlet of the check valve that is substantially equal to a cross sectional flow area at an inlet of the check valve, and controlling fluid flow from the bleed duct to the bleed port using the check valve.  
         [0006]     In another aspect, a check valve is provided that includes a valve housing that has a side wall and a flow path therethrough, the side wall defining the flow path. The flow path includes an inlet, an outlet, and a centerline extending between the inlet and the outlet. At least one control member is positioned in the flow path and movable between a first position, wherein fluid flow through the valve housing is substantially prohibited and a second position wherein fluid flow is permitted. The side wall includes a stop configured to limit movement of the at least one control member at a pre-determined stop angle relative to the flow path centerline.  
         [0007]     In a further aspect, a gas turbine engine bleed air supply system is provided. The bleed air supply system includes a bleed duct having first and second ends. The first end is coupled to at least one compressor bleed port, and a check valve coupled to the second end of the bleed duct. The check valve is configured to permit fluid flow from the bleed duct while substantially preventing fluid flow into the bleed duct. The check valve includes a valve housing that has a side wall and a flow path therethrough, the side wall defining the flow path. The flow path includes an inlet, an outlet, and a centerline extending between the inlet and the outlet. At least one control member is positioned in the flow path and is movable between a first position, wherein fluid flow through the valve housing is substantially prohibited and a second position wherein fluid flow is permitted. The side wall includes a stop configured to limit movement of the at least one control member at a pre-determined stop angle relative to the flow path centerline. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine;  
         [0009]      FIG. 2  is a schematic cross-sectional view of a portion of a bleed air supply system;  
         [0010]      FIG. 3  is a perspective view of an exemplary check valve used with the supply system shown in  FIG. 2 ;  
         [0011]      FIG. 4  is an exploded view of the check valve shown in  FIG. 3 ;  
         [0012]      FIG. 5  is a cross sectional view of the retaining pin installed in the valve housing shown in  FIG. 4 ; and  
         [0013]      FIG. 6  is a cross sectional view of the check valve shown in  FIG. 3  taken along the line  6 - 6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine  10 . Engine  10  includes a low pressure compressor  12 , a high pressure compressor  14 , and a combustor assembly  16 . Engine  10  also includes a high pressure turbine  18 , and a low pressure turbine  20  arranged in a serial, axial flow relationship. Compressor  12  and turbine  20  are coupled by a first shaft  24 , and compressor  14  and turbine  18  are coupled by a second shaft  26 . In one embodiment, engine  10  is a GP7200 engine commercially available from General Electric Aircraft Engines, Cincinnati, Ohio. Engine  10  includes a bleed air supply system  30  coupled to compressor  14 . In an exemplary embodiment, air is bled from a fourth stage of compressor  14 .  
         [0015]     In operation, air flows through low pressure compressor  12  from an upstream side  28  of engine  10 . Compressed air is supplied from low pressure compressor  12  to high pressure compressor  14 . Bleed air supply system  30  extracts bleed air from compressor  14  for use in an aircraft, such as for delivery to an environmental control system (ECS) (not shown). Compressed air is then delivered to combustor assembly  16  where it is mixed with fuel and ignited. Combustion gases are channeled from combustor  16  to drive turbines  18  and  20 .  
         [0016]      FIG. 2  illustrates a schematic cross-sectional view of an exemplary embodiment of a portion of a bleed air supply system  30 . Bleed air system  30  includes a bleed port  32  and a bleed air duct  34 . A check valve  40  interconnects bleed port  32  and bleed duct  34 . In one embodiment, bleed port  32  is used to extract bleed air from a fourth stage of compressor  14 . Check valve  40  regulates bleed air fluid flow from engine  10  (shown in  FIG. 1 ). More specifically, in one embodiment, check valve  40  regulates the delivery of bleed air from compressor  14  to an ECS. Check valve  40  includes an inlet  42  and an inlet flange  44  that is coupled to a flange  46  on bleed port  32 . Inlet flange  44  couples check valve  40  in flow communication with bleed port  32 . Similarly, check valve  40  also includes an outlet  48  and an outlet flange  50 . Outlet flange  50  is coupled to a bleed duct flange  52  and couples check valve  40  in flow communication to bleed duct  34 . Check valve  40  controls fluid flow from bleed port  32  to bleed duct  34 . More specifically, check valve  40  selectively enables fluid flow in the direction of arrow A, while substantially preventing fluid flow in the opposite direction.  
         [0017]     Check valve  40  includes a valve housing  56  that has a side wall  58  that extends between inlet  42  and outlet  48 . Housing  56  defines a flow path  60  through check valve  40  between inlet  42  and outlet  48 . Control members  62  and  64  are positioned in the flow path  60  to regulate fluid flow through check valve  40 . Control members  62  and  64  may operate together or independently from each other.  
         [0018]      FIG. 3  is a perspective view of check valve  40 . In the exemplary embodiment, housing side wall  58  is substantially conical and has a substantially circular cross section at profile. Valve housing  56  has a diameter D 1  (see  FIG. 6 ) at outlet  48  that is larger than a diameter D 2  at inlet  42 . Inlet flange  44  and outlet flange  48  are formed integrally with valve housing  56  and extend outwardly therefrom. In the exemplary embodiment, flanges  44  and  48  are substantially circular. Alternatively, flange  44  and  48  are non-circular. A lip  66  is formed on an interior surface  67  of side wall  58  proximate check valve inlet  42 . Lip  66  extends circumferentially within side wall  58  and forms a seat for control members  62  and  64  when control members  62  and  64  are in a closed position. A pressure sensing port  68  extends through side wall  58  for sensing pressure at valve inlet  42 . Stops  70  are formed on side wall interior surface  67  proximate valve outlet  48 . Stops  70  engage control members  62  and  64  to facilitate limiting the amount of movement and thus the size of the opening defined by control members  62  and  64 . In the exemplary embodiment, stops  70  are diametrically opposed and are identical to one another. In an exemplary embodiment, stops  70  are formed integrally with the valve housing  56 .  
         [0019]      FIG. 4  is an exploded view of check valve  40 .  FIG. 5  is a schematic cross-sectional view of retaining pin  74  installed in the check valve housing  56 . In the exemplary embodiment, valve housing  56  is a one-piece casting that includes integrally formed flanges  44  and  50 , stops  70 , and lip  66  (see  FIG. 3 ). Valve housing  56  also includes an aperture  72  that receives a retaining pin  74  to which control members  62  and  64  are rotatably coupled. An interior cavity  76  is defined in valve housing  56  diametrically opposite aperture  72 , and a platform  78  extends diametrically across valve housing  56  and joins lip  66 . A flow splitter  79  (see  FIG. 2 ) extends from an underside of platform  78 . Flow splitter  79  diverts fluid flow around platform  78  and towards control members  62  and  64  to facilitate preventing pressure losses within check valve  40  such that fluid flow through check valve  40  is enhanced. When retaining pin  74  is installed in valve housing  56 , platform  78 , retaining pin  74 , and stops  70  are substantially aligned with one another.  
         [0020]     Retaining pin  74 , which also may be referred to as a hinge pin, includes an elongated shaft  80  that extends between a first end  82  and a second end  84 . First end  82  includes a flange  85  that has a diameter D 4  and a stepped portion  86  that has a diameter D 5  that is slightly smaller than a diameter D 6  of aperture  72  such that stepped portion  86  is received in aperture  72  without resistance. Valve housing  56  includes an internal aperture  87  that is slightly smaller in diameter than flange  85 , but slightly larger than stepped portion  86 . More specifically, stepped portion  86  is slip fitted into internal aperture  87 . Flange  85  abuts a shoulder  91  at internal aperture  87  to establish an axial position of stepped portion  86 . Second end  84  of retaining pin  74  is received in cavity  76  such that pin second end  84  is supported. Cavity  76  also provides an axial clearance  89  to accommodate thermal growth of retaining pin  74 . A retaining nut  88  retains retaining pin  74  in valve housing  56  and applies sufficient force to flange  85  against shoulder  91  such that rotation and axial motion of retaining pin  74  in valve housing  56  is substantially prohibited.  
         [0021]     In the exemplary embodiment, control members  62  and  64  are identical. Each control member  62  and  64  includes a pair of mounting arms  90  that rotatably couple each member  62  and  64  to retaining pin  74 . In the exemplary embodiment, control members  62  and  64  are hinged on retaining pin  74  and are independently operable. Each mounting arm  90  includes an aperture  92  that receives a bushing  94 . In one embodiment, bushings  94  are press fit into mounting arms  90 . Bushings  94  facilitate providing wear resistance between retaining pin  74  and mounting arms  90 . In addition, bushings  94  extend through mounting arms  90 . Flange  85 , when positioned against shoulder  91  axially positions stepped portion  86  such that bushings  94  cooperate with stepped portion  86  and a shoulder  95  on valve body  56  to facilitate aligning control members  62  and  64  and eliminate the need for shim washers during assembly of control members  62  and  64 . In one embodiment, bushings  94  are fabricated from cobalt.  
         [0022]     Each control member  62  and  64  includes a flapper portion  96  from which mounting arms  90  extend. Flapper portions  96  are substantially semi circular and extend across flow path  60 . In the exemplary embodiment, flapper portions  96  have a thickness T (see  FIG. 6 ) which tapers from a central portion proximate mounting arms  90  to a reduced thickness at an outer periphery  98 . Flapper portions  96  include projections  100  that extend from an upper surface  102 .  
         [0023]     Projections  100  are positioned to engage stops  70  when control members  62  and  64  are fully open.  
         [0024]      FIG. 6  is a schematic cross-sectional view of check valve  40 . Side wall  58  defines flow path  60  through valve housing  56 . Flow path  60  has a centerline  110  that extends through a geometric center of valve housing  56 . In  FIG. 6 , check valve  40  is depicted with control members  60  and  62  fully open such that flapper projections  100  are in contrast with valve housing stops  70 . To facilitate reducing flutter of control members  62  and  64  when fully opened, the rotation of the control members  62  and  64  is stopped at an angle β with respect to flow path centerline  110  before control members  62  and  64  are parallel to the flow path centerline  110 . Angle β represents a stabilization angle wherein momentum or inertia forces from the impingement of fluid against the control members  62  and  64  act to stabilize control members  62  and  64  against flutter. In the exemplary embodiment, angle β is approximately equal to fifteen degrees.  
         [0025]     To facilitate minimizing pressure loss through check valve  40 , valve housing  56  is formed such that a cross-sectional flow path area is substantially uniform between valve inlet  42  and outlet  48  when control members  62  and  64  are fully open (as shown in  FIG. 6 ). More specifically, the cross-sectional flow area at valve inlet  42  is proportional to an inlet flow path width represented by the arrow W 1 . Similarly, the cross-sectional flow area at valve outlet  48  is proportional to an outlet flow path width represented by the arrow W 2 . Valve housing side wall  58  is fabricated such that the flow path area at inlet  42  is substantially equal to the flow path area at valve outlet  48  when control members  62  and  64  are fully opened, thereby facilitating minimizing pressure loss through check valve  40 . In an exemplary embodiment, valve housing side wall  58  is formed with an outward conical flare having a cone angle β relative to the flow path centerline  110 . Angle β is measured between valve inlet  42  and valve outlet  48  and is selected to provide an outlet flow path width W 2  that is substantially equal to inlet flow path width W 1 . In an exemplary embodiment, angle β is approximately seventy-three percent of the stabilization angle β.  
         [0026]     Check valve  40  is assembled by pressing bushings  94  into control member mounting arms  90 . Control members  62  and  64  are then positioned within valve housing  56  such that retaining pin second end  84  is inserted through aperture  72 , through interleaved control member mounting arms  90 , and into cavity  76 . Retaining nut  88  is then installed in aperture  72  to retain retaining pin  74  therein. Retaining nut  88  is safety wired to valve housing  56  to prevent retaining nut  88 , from uncoupling from housing  56 . A plug or pressure sensor fitting is installed in pressure sensor port  68  as desired. The plug or pressure sensor fitting can also be safety wired in place. Thus, assembly of check valve  40  is accomplished with a minimal number of parts.  
         [0027]     In one embodiment, check valve  40  can be used in a system to supply bleed air to an environmental control system (ECS). In operation, and with reference to  FIG. 2 , check valve inlet  42  is coupled to a compressor bleed port  32 . Check valve outlet  48  is coupled to a bleed duct  34 . The bleed port and bleed duct connections are made at valve inlet and outlet flanges  44  and  50 , respectively. As fluid flow from bleed port  32  enters check valve  40 , fluid pressure acting on control members  62  and  64  causes control members  62  and  64  to rotate to an open position. At sufficient pressure, control members  62  and  64  open sufficiently to engage stops  70 . Side wall  58  is formed at a conical angle sized to maintain a cross sectional flow area at valve outlet  48  that is substantially equal to a cross sectional area at valve inlet  42 . As a result, pressure losses through check valve  40  are facilitated to be reduced. Finally, when pressure differentials between bleed port  32  and bleed duct  34  change so as to cause a reversal in fluid flow, control members  62  and  64  rotate to a fully closed position to substantially prevent fluid flow from bleed duct  34  to bleed port  32 .  
         [0028]     The above-described check valve is cost-effective to manufacture and is highly reliable and serviceable. The check valve includes control members that have a fully open position at a angle to the fluid flow path so that the control members are stabilized against flutter. This reduces wear on the retaining pin and control members which increases the service life of the control valve, thus reducing maintenance costs. Assembly costs are also reduced due to a reduction in part count in comparison to known check valves.  
         [0029]     Exemplary embodiments of check valve assemblies engine bleed air systems are described above in detail. The systems and assemblies are not limited to the specific embodiments described herein, but rather, components of each assembly and system may be utilized independently and separately from other components described herein. Each system and assembly component can also be used in combination with other system and assembly components.  
         [0030]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.