Patent Application
20170030477
The disclosure relates generally to pneumatic valves, and more particularly to pneumatic valves having a passive servo filter.
Pneumatically actuated valves, typically but not exclusively butterfly valves, use servo air acting on either side of a piston to provide a linear force which is converted into a rotary motion to position the butterfly disc. Often the servo air is drawn from a valve inlet side, then is routed through a servo valve. The servo valve modulates servo airflow to position the valve as desired.
Due to their relatively small size in comparison to the main pneumatic valve, many servo valves often have tight operating clearances. Operation can therefore be impaired by airborne contaminants (e.g., dust, sand particles, foreign objects, etc.) which may be found in the primary flow of the valve. Some of these contaminants are too large to pass through the servo valve clearances, leading to accumulation of particulate in key areas. This will degrade performance of the servo valve and result in eventual failure of the pneumatic valve.
A bleed assembly includes a bleed valve disposed across a bleed duct. The bleed valve includes a valve housing, a shaft connecting an actuator assembly to a flow control member, and a servo tube. The actuator assembly includes a linear actuator disposed perpendicular to a valve centerline, so that linear motion of the actuator is transverse to a valve centerline. The member is in the main fluid passage, rotatable between a fully closed position defined by leading and trailing edges abutting one or more housing walls, and a fully open position defined by the leading edge at the upstream side and the trailing edge at the downstream side of the main flow passage. A first portion of a servo tube extends into the main passage from a distance P1 upstream of the member in a fully closed position, and angular distance A1 of at least 10° from the top dead center (TDC) position.
A valve assembly includes at least one wall defining a main fluid passage having an upstream side and a downstream side, a top dead center (TDC) position, and a bottom dead center (BDC) position. A flow control member is mounted to a shaft entering the main fluid passage at the TDC position. The member is rotatable in the main fluid passage between a fully closed position defined by leading and trailing edges abutting one or more passage walls, and a fully open position defined by the leading edge at the upstream side of the passage and the trailing edge at the downstream side of the passage. A servo tube includes a first tube portion extending into the main fluid passage from a port disposed distance P1 upstream of the leading edge of the member when the member is in the fully open position, and disposed at angular distance A1 from the TDC position. Angular distance A1 is at least 10° measured in a direction around the main fluid passage toward the trailing edge when the member is in the fully closed position, and distance P1 is equal to or greater than at least 60% of passage diameter D1.
Example bleed assembly includes bleed duct 12 providing communication between compressor 14 and manifold 16. Valve 20 can be disposed across bleed duct 12 to control flow the amount of compressed fluid drawn from working fluid stream 18.
Valve 20 can be actuated in response to a pressure input as compared to a desired pressure setpoint. The pressure input can be from a sensor (not shown) disposed in bleed duct 12 (shown in
Note that “upstream” and “downstream” are described with reference to the intended flow direction through main fluid passage 30. In this type of installation, designed to regulate flow in a single direction, the description of “upstream” and “downstream” are not intended to encompass transient, emergency, or other unplanned events whereby reversals of flow occur, temporarily resulting in the “upstream” side having “downstream” flow, or vice versa. It will be recognized that other installations of valve 20 may be configured to regulate flow in both directions. However, the totality of this disclosure will make any useful or needed modifications for bidirectional flow installations readily apparent to one skilled in the art.
Returning to
Linear actuator 38 can be disposed perpendicular to centerline CL (Main) of main fluid passage 28, so that linear motion of actuator 38, e.g., along centerline CL (Actuator), is transverse thereto. Linear actuator 38 can include piston rod 40 connecting a pair of horizontally opposed pistons 42A, 42B defining piston unit 44. Actuator assembly 24 can also include torque motor 46 disposed in motor chamber or mount 48. In addition. actuator chamber 32 can include walls 50 and cover 52 for retaining piston unit 44 while also providing access for maintenance.
Torque motor 46 can actuate linear actuator 38 by driving piston unit 44 along centerline CL (Actuator). In the example shown, fluid from upstream side 34A of main fluid passage 28 is drawn into actuator chamber 32 via servo tube 56, and enters through supply port 58 disposed in filter chamber 60 and formed through one of the walls defining actuator chamber 32. A filter element (omitted for clarity) can be provided in filter chamber 60 to clean the fluid of particulates and/or contaminants before it is supplied to actuator 38.
Fluid is drawn from main fluid passage 28 via servo tube 56 (better seen in
Depending on operating conditions of a particular installation, fluid drawn from main fluid passage 28 via supply port 58, can be subject to particulate infiltration. A filter (disposed in filter chamber 60) can remove some of the particulates. However arranging the inlet of servo tube 56, as shown in subsequent figures, can optimize flow through the valve over its operating envelope, while also minimizing particulate infiltration into chamber 60 and beyond.
In addition to elements in preceding figures,
As better seen in these views, actuator assembly 24 and actuator chamber 34 have a combined center of gravity directly above the flow control element 66 and substantially proximate to shaft 26. Elements of actuator chamber 24 are spaced above main fluid passage 28 such that valve 20 is more balanced than a conventional cantilevered valve. Support brackets 64, which can be integral to housing 22, provide further lateral support in certain embodiments. However, the arrangement is not so limited. Additional details of transversely mounted actuator valves can also be found in copending U.S. patent application Ser. No. 14/599,898 filed on Jan. 19, 2015, which is herein incorporated by reference in its entirety.
Flow control member 66 can be a disc or other structure that, at least when fully closed, generally separates upstream side 34A from downstream side 34B of main fluid passage 28. In the example shown, where member 66 is a disc, member 66 can be rotatable in main fluid passage 28 between a fully closed position and a fully open position. The fully closed position, shown in
As with other directional descriptors, leading edge 68, trailing edge 70, upstream face 72, and downstream face 74 are defined generally based on an intended flow direction through main fluid passage 30. As such, with
As noted with respect to
In addition to the optional active filter described above, servo tube 56 operates as a passive particle separator to draw clean air from main flow passage 28. Servo tube 56 can include first portion 82 extending into main fluid passage 28 from port 84 formed through the at least one wall (e.g., cylindrical wall 30). First portion 82 can extend down to a point proximate to or even with central diametral plane 80, which passes through main fluid passage 28, including valve centerline CL (Main) in a direction normal to shaft 26.
Previous iterations, intended for butterfly valves with cantilevered actuators, have a servo tube aligned with the disc and shaft such that the port is positioned at TDC and the opening is in turn positioned close to the duct wall. The servo tube typically has a single length in the main passage and a scarf cut at the end of the tube angled to the downstream to pick up air. Typically the tube is located with the opening positioned close to the duct wall to reduce the valve overall envelope. However, when the valve is open, this close proximity can result in turbulence from the leading edge of the disc distorting the airflow into the tube and reducing its precision and responsiveness to commands.
Elbow 92 is disposed proximate to main passage inlet 90 to main fluid passage 30, and can have a bend angle of more than 90°. The bend angle can coincide with the angle of first portion 82 and simplify insertion of tube 56 into passage 28, while providing ready access to filter 94 disposed in filter chamber 60.
Port 84 can be disposed a distance P1 upstream of disc member 66 when member 66 is in a fully closed position. (closed position shown in
Servo tube opening 96 can be disposed a distance P2 upstream of disc member 66 when member 66 is in a fully closed position (closed position shown in
Servo tube 56 can extend either straight down or be angled upstream from port 84. Tube inlet of the servo tube can be located in or proximate to a horizontal plane through the valve centerline. A direct route from the inlet chamber to the filter, which can be offset from the main valve centerline to provide balance in valves with a transversely mounted actuator, further reduces the possible locations for particle accumulation in the servo tube before airflow (and the entrained particles) reaches the filter and the remainder of the actuator assembly.
As noted previously, valve 20 is suitable for use in the bleed arrangement shown in
The following are non-exclusive descriptions of possible embodiments of the present disclosure.
A bleed assembly includes a bleed valve disposed across a bleed duct. The bleed valve includes a valve housing, a shaft connecting an actuator assembly to a flow control member, and a servo tube. The actuator assembly includes a linear actuator disposed perpendicular to a valve centerline, so that linear motion of the actuator is transverse to a valve centerline. The member is in the main fluid passage, rotatable between a fully closed position defined by leading and trailing edges abutting one or more housing walls, and a fully open position defined by the leading edge at the upstream side and the trailing edge at the downstream side of the main flow passage. A first portion of a servo tube extends into the main passage from a distance P1 upstream of the member in a fully closed position, and angular distance A1 of at least 10° from the top dead center (TDC) position.
The bleed assembly embodiment of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A bleed assembly according to an exemplary embodiment of this disclosure, among other possible things includes a bleed duct providing communication between a compressor and a manifold; and a bleed valve disposed across the bleed duct, the bleed valve comprising: a valve housing including at least one wall defining a main fluid passage having an upstream side and a downstream side, a top dead center (TDC) position, and a bottom dead center (BDC) position; an actuator assembly disposed in an actuator chamber, the actuator assembly including a linear actuator disposed perpendicular to the main fluid passage centerline, so that linear motion of the actuator is transverse to a valve centerline; a flow control member separating the upstream side from the downstream side of the main fluid passage, the member including a leading edge, a trailing edge, an upstream face and a downstream face, the member rotatable in the main fluid passage between a fully closed position defined by the leading and trailing edges abutting the one or more walls, and a fully open position defined by the member having the leading edge at the upstream side and the trailing edge at the downstream side of the main flow passage; a shaft connecting the flow control member to the actuator assembly; and a servo tube including a first portion extending from a port formed through the at least one wall, the port disposed a distance P1 upstream of the member when the member is in a fully closed position, and an angular distance A1 of from the TDC position; wherein the angular distance A1 is at least 10° as measured in a direction around the main fluid passage toward the trailing edge of the member when the member is fully closed, and the distance P1 is equal to or greater than at least 60% of a passage diameter D1.
A further embodiment of the foregoing assembly, wherein the actuator assembly includes a filter chamber configured to receive working fluid entering the actuator assembly from the servo tube.
A further embodiment of any of the foregoing assemblies, wherein the actuator assembly also includes a torque motor in communication with the linear actuator.
A further embodiment of any of the foregoing assemblies, wherein the first portion of the servo tube extends straight into the main fluid passage in a direction generally parallel to the shaft.
A further embodiment of any of the foregoing assemblies, wherein the first portion of the servo tube extends from the port at an upstream angle toward an inlet to the main fluid passage.
A further embodiment of any of the foregoing assemblies, wherein the servo tube also includes an elbow proximate to an inlet to the main fluid passage, the elbow having a bend angle of more than 90°.
A further embodiment of any of the foregoing assemblies, wherein the servo tube also includes a second portion substantially parallel to, and radially offset from a valve centerline.
A further embodiment of any of the foregoing assemblies, wherein the second portion extends through a central diametrical plane of the main fluid passage.
A further embodiment of any of the foregoing assemblies, wherein the second portion has a generally downstream opening facing the flow control member.
A further embodiment of any of the foregoing assemblies, wherein the opening is disposed a distance P2 upstream of the member when the member is in a fully closed position, the distance P2 equal to or greater than at least 50% of the passage diameter D2.
A further embodiment of any of the foregoing assemblies, wherein the actuator assembly and the actuator chamber have a combined center of gravity directly above the flow control element and substantially proximate to the shaft.
A valve assembly includes at least one wall defining a main fluid passage having an upstream side and a downstream side, a top dead center (TDC) position, and a bottom dead center (BDC) position. A flow control member is mounted to a shaft entering the main fluid passage at the TDC position. The member is rotatable in the main fluid passage between a fully closed position defined by leading and trailing edges abutting one or more passage walls, and a fully open position defined by the leading edge at the upstream side of the passage and the trailing edge at the downstream side of the passage. A servo tube includes a first tube portion extending into the main fluid passage from a port disposed distance P1 upstream of the leading edge of the member when the member is in the fully open position, and disposed at angular distance A1 from the TDC position. Angular distance A1 is at least 10° measured in a direction around the main fluid passage toward the trailing edge when the member is in the fully closed position, and distance P1 is equal to or greater than at least 60% of passage diameter D1.
The valve assembly embodiment of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A valve assembly according to an exemplary embodiment of this disclosure, among other possible things includes at least one wall defining a main fluid passage having an upstream side and a downstream side, a top dead center (TDC) position, and a bottom dead center (BDC) position; a shaft entering the main fluid passage at the TDC position between the upstream and downstream sides of the main fluid passage; a flow control member mounted to the shaft, the member including a leading edge, a trailing edge, an upstream face and a downstream face, the member rotatable in the main fluid passage between a fully closed position defined by the leading and trailing edges abutting the one or more walls, and a fully open position defined by the member having the leading edge at the upstream side and the trailing edge at the downstream side of the main flow passage; and a servo tube including a first tube portion extending into the main fluid passage from a port disposed a distance P1 upstream of the leading edge of the member when the member is in the fully open position, and disposed an angular distance A1; wherein the angular distance is at least 10° measured from the TDC position in a direction around the main fluid passage toward the trailing edge of the member when the member is in the fully closed position, and the distance P1 is equal to or greater than at least 60% of a passage diameter D1.
A further embodiment of the foregoing assembly, wherein the first portion of the servo tube extends straight into the main fluid passage in a direction generally parallel to the shaft.
A further embodiment of any of the foregoing assemblies, wherein the first portion of the servo tube extends into the main fluid passage toward a passage inlet at an upstream angle from the bore.
A further embodiment of any of the foregoing assemblies, wherein the servo tube also includes an elbow proximate to an inlet of the main fluid passage, the elbow having a bend angle of more than 90°.
A further embodiment of any of the foregoing assemblies, wherein the servo tube includes a second portion substantially parallel to, and offset from, a valve centerline.
A further embodiment of any of the foregoing assemblies, wherein the second portion extends through a central diametrical plane of the main fluid passage.
A further embodiment of any of the foregoing assemblies, wherein the second portion has a generally downstream opening facing the flow control member.
A further embodiment of any of the foregoing assemblies, wherein the opening is disposed a distance P2 upstream of the member when the member is in a fully closed position, the distance P2 equal to or greater than at least 50% of the passage diameter D2.
A further embodiment of any of the foregoing assemblies, further comprising: a linear actuator disposed in an actuator chamber, the linear actuator including at least one piston drivable along an actuator centerline, disposed perpendicular to the main fluid passage centerline, so that linear motion of the at least one piston is transverse to the valve centerline; wherein the actuator assembly and the actuator chamber have a combined center of gravity directly above the flow control element and substantially proximate to the shaft.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
