Patent Application
20170030341
This disclosure relates generally to a manifold and, more particularly, to a manifold for a multi-plunger cryogenic in-tank pump.
Gaseous fuel powered engines are common in many applications. For example, the engine of a locomotive can be powered by natural gas (or another gaseous fuel) alone or by a mixture of natural gas and diesel fuel. Natural gas may be more abundant and, therefore, less expensive than diesel fuel. In addition, natural gas may burn cleaner in some application, and produce less greenhouse gas.
Natural gas, when used in a mobile application, may be stored in a liquid state onboard the associated machine. This may require the natural gas to be stored at cold temperatures, typically about −100 to −162° C. The liquefied natural gas is then drawn from the tank by gravity (and/or by a boost pump) and directed to a high-pressure pump. The high-pressure pump further increases a pressure of the fuel and directs the fuel to the machine's engine. In some applications, the liquid fuel may be gasified prior to injection into the engine and/or mixed with diesel fuel (or another fuel) before combustion.
One problem associated with pumps operating at cryogenic temperatures involves flash boiling of the natural gas due to low pressures observed during retracting strokes of the pump's pistons. In order to avoid such low pressures, and thereby avoid flash boiling of the natural gas, modern cryogenic pump systems incorporate pistons submerged within liquid fuel at the bottom of the tank. Each piston is connected with an inlet check valve that allows low-pressure fuel from the tank to enter an associated barrel, and with an outlet check valve that allows high-pressure fuel to be discharged from the barrel. These valves are typically packaged together within a separate head assembly associated with each piston.
An exemplary cryogenic pump is disclosed in U.S. Pat. No. 4,576,557 that issued to Pevzner on Mar. 18, 1986 (“the '557 patent”). The pump of the '557 patent is a reciprocating-type pump having a pumping section with three plungers that are each connected to a crankshaft. As the crankshaft rotates, the plungers are caused to reciprocate within the pumping section. A valve assembly is associated with each of the plungers and separately mounted to the pumping section. Each valve assembly includes a discharge valve and a suction valve.
While the conventional cryogenic pump having separate head or valve assemblies may be suitable for some applications, it may also be problematic for other applications. In particular, the separate head or valve assemblies can require a significant amount of space at the pump. There may not be enough space for these assemblies in some applications.
The disclosed pump and manifold are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
In one aspect, the present disclosure is directed to a liner for a cryogenic pump having a manifold. The liner may include a generally cylindrical body having a top end and a bottom end, and an internal bore formed in the generally cylindrical body and passing from the top end through the bottom end. The internal bore may be configured to receive a plunger of the cryogenic pump. The liner may also include a flange located at the top end and configured to be used to connect the generally cylindrical body to a barrel of the manifold.
In one aspect, the present disclosure is directed to a manifold for a cryogenic pump. The manifold may include a generally cylindrical body having a top end and a bottom end, and a plurality of bores arranged in a ring around a central axis of the generally cylindrical body. Each of the plurality of bores may be configured to communicate with a different plunger barrel of the cryogenic pump. The manifold may also include at least one inlet orifice in fluid communication with each of the plurality of bores.
In another aspect, the present disclosure is directed to a cryogenic pump. The cryogenic pump may include a plunger housing with a plurality of barrels formed in a ring around a central axis, and a plurality of plungers. Each of the plurality of plungers may be reciprocatingly disposed within a different one of the plurality of barrels. The cryogenic pump may also include an inlet manifold connected to an end of the plunger housing and having a plurality of bores. Each of the plurality of bores may be open to a corresponding one of the plurality of barrels. The cryogenic pump may also include at least one orifice in fluid communication with each of the plurality of bores, and an inlet check valve disposed within the inlet manifold between each of the plurality of bores and the at least one orifice. The inlet check valve may be movable to selectively allow fluid flow between the at least one orifice and a corresponding one of the plurality of barrels.
Tank 12 may be a cryogenic tank configured to hold fluid in its liquefied state. In the exemplary embodiment, tank 12 has one or more inner walls 20 separated from one or more outer walls 22 by an air gap. In some embodiments, an insulating layer 24 may be disposed in the air gap (e.g. on inner wall 20). The air gap, together with insulating layer 24, may function to maintain a temperature of the liquid below its boiling threshold of about −100° C. to −162° C. (i.e., depending on a pressure inside tank 12).
Tank 12 may be generally cylindrical, having a top 26 and a bottom 28. An opening 30 may be formed in top 26 that passes through both of inner and outer walls 20, 22. Opening 30 may be generally aligned with a central axis 32 of symmetry. Bottom 28 may be closed.
Pump 14 may be at least partially submerged inside of tank 12, for example inside a centralized socket 34 formed in tank 12. In particular, pump 14 may hang from top 26 of tank 12 a distance below a fluid level therein. By being connected to tank 12 at only one end, pump 14 may be allowed to expand and contract due to normal thermal loading without inducing stresses in tank 12 that could damage tank 12 and/or pump 14. Power source 16 may be located outside of tank 12, and connected to drive pump 14 via a belt 36 and a mechanical input 38. In the disclosed embodiment, power source 16 is an electric motor and mechanical input 38 is a shaft. In other exemplary embodiments, however, power source 16 could be the consumer receiving fuel from pump 14 (or another power source) and/or mechanical input 38 could be a gear train, if desired. In either of these arrangements, an output rotation of power source 16 may cause belt 36 to induce a corresponding input rotation of mechanical input 38.
Pump 14 may be generally cylindrical and divided into two ends. For example, pump 14 may be divided into a warm or input end 40, into which mechanical input 38 extends, and a cold or output end 42 that is at least partially submerged in the fluid. Warm end 40 may be fixedly mounted to tank 12 at top 26, for example by way of one or more mounting hardware components 44 (e.g., flanges, seals, brackets, gaskets, etc.). Warm end 40 may be insulated and/or isolated from cold end 42 (e.g., encased in vacuum jacket or super insulated liner that inhibits heat transfer). Cold end 42 may extend from warm end 40 deeper into tank 12. With this configuration, the input rotation provided to pump 14 at warm end 40 (i.e., via mechanical input 38) may be used to generate a high-pressure discharge at the opposing cold end 42. The high-pressure discharge may be directed back up past warm end 40 via passage 18 to exit tank 12 at opening 30. In most applications, pump 14 will be mounted and used in the orientation shown in
Pump 14 may be an axial piston type of pump. In particular, a pump shaft 46 may be rotatably supported within a housing 48, and connected at a top end to mechanical input 38 (e.g., via a splined interface) and at a bottom end to a load plate 50. Load plate 50 may be oriented at an oblique angle relative to axis 32, such that the input rotation of shaft 46 may be converted into a corresponding undulating motion of load plate 50. A plurality of tappets 52 may slide along a lower face of load plate 50, and a push rod 54 may be associated with each tappet 52. In this way, the undulating motion of load plate 50 may be transferred linearly through tappets 52 to push rods 54 and used to pressurize the fluid passing through cold end 42. A resilient member, for example a coil spring 56, may be associated with each push rod 54 and configured to bias the associated tappet 52 into engagement with load plate 50. Each push rod 54 may be a single-piece component or, alternatively, be comprised of multiple pieces, as desired. Many different shaft/load plate configurations may be possible, and the oblique angle of load plate 50 may be fixed or variable, as desired. In the disclosed embodiment, the oblique angle of load plate 50 is fixed, and a variable output of pump 14 is obtained via speed adjustment of power source 16.
Cold end 42 of pump 14 may be an assembly of different components that performs several different functions. In particular, cold end 42 may function as a guide for push rods 54, as a pumping mechanism, and as a distributer/collector of low- and high-pressure fluids. Several different cold end embodiments are included in this disclosure and depicted in
As shown in the embodiment of
Connecting flange 58 may function to connect cold end 42 to warm end 40 and also as a lower-end guide for push rods 54. In particular, connecting flange 58 may have a generally cylindrical body, with a plurality of bores 68 formed therein and arranged in a ring around axis 32. Each of bores 68 may be configured to receive a different guide nut 70. In one embodiment, connecting flange 58 is fastened to an end of housing 48 (e.g., via fasteners 66 or other fasteners—not shown), thereby connecting cold end 42 to warm end 40. In another embodiment, a plurality of push rod sleeves 72 (shown only in
Spacer plate 60, like connecting flange 58, may also have a generally cylindrical body with a plurality of bores 77 formed in a ring around axis 32. Spacer plate 60 may function as a spacer between connecting flange 58 and plunger housing 62 and provide for unrestricted leak paths 78 to bores 77. Accordingly, the body of spacer plate 60 may be relatively plate-like. Leak paths 78 may extend radially outward from each bore 77 to an outer periphery of spacer plate 60. With this configuration, any fuel leaking from manifold 64 at the distal ends of push rods 54 may be allowed to return uninhibited to tank 12 via leak paths 78.
Plunger housing 62 may function to house a plurality of plungers 80 and, together with plungers 80, form a plurality of different pumping mechanisms. Specifically, plunger housing 62 may have a generally cylindrical body, with a plurality of hollow barrels 82 formed therein in a ring around axis 32. Barrels 82 may be open to and aligned with bores 77 of spacer plate 60 and bores 68 of connecting flange 58. One plunger 80 may be slidingly disposed within each barrel 82 and engaged with the distal end of a corresponding push rod 54. In this way, an extending movement of push rod 54 may translate into a downward sliding motion of a corresponding plunger 80 toward a Bottom-Dead-Center (BDC) position. A pressure of the fuel in tank 12 and in barrel 82 may help to return plunger 80 to a Top-Dead-Center (TDC) position as push rod 54 is retracted from barrel 82. In one example, push rod 54 is disconnected from plunger 80 (i.e., plunger 80 is a free-floating plunger). In another example, push rod 54 is loosely connected to plunger 80, such that a retracting motion of push rod 54 functions to assist the upward movement of plunger 80 within barrel 82. The cylindrical body of plunger housing 62 may have a central cavity 83 disposed inward of barrels 82 and aligned with axis 32. Central cavity 83 may be configured to receive a portion of manifold 64.
Manifold 64 may house a plurality of valves that are movable to allow fluid into each barrel 82 during movement of the corresponding plungers 80. In particular, manifold 64 may have a generally cylindrical body, with a plurality of bores 84 formed therein that are open to and generally aligned with barrels 82 of plunger housing 62. Each bore 84 may be in communication with tank 12 (e.g., via one or more orifices 86) at a bottom end of manifold 64 and house a separate inlet check valve 87. Orifices 86 may be generally parallel with an axis of its corresponding bore 84, and arranged in a ring around a center valve guide 88. A stem 90 of each inlet check valve 87 may be slidingly disposed within a corresponding one of guides 88, such that as check valve 87 moves from a closed position (shown in
The cylindrical body of manifold 64 may be stepped, with inlet check valves 87 arranged in a flange portion that surrounds an inwardly protruding center portion. The inwardly protruding center portion may be recessed completely within cavity 83 of plunger housing 62, while the flange portion may abut the lower end of plunger housing 62. After drawing low-pressure fluid into barrels 82 via inlet check valves 87, a subsequent extending movement of plungers 80 may function to discharge high-pressure fluid out of barrels 82. The high-pressure discharge from all barrels 82 may join each other inside the center portion of manifold 64 for radial discharge from manifold 64 (and ultimately from pump 14) via passage 18. In particular, one or more passages 96 may extend through the flange and center portions of manifold 64 to connect each barrel 82 with a central discharge cavity 98, which is in fluid communication with passage 18.
An outlet check valve 100 may be disposed within each passage 96 to help ensure a unidirectional flow of fluid from barrels 82 into cavity 98. Outlet check valves 100 may be disposed in the center portion of manifold 64 and arranged in a ring around axis 32. In the disclosed embodiment, both inlet and outlet check valves 87, 100 are assembled into manifold 64 from the same internal end. Inlet check valves 87 may be retained inside manifold 64 by plunger housing 62 (or alternatively by way of dedicated threaded heads or pins inserted into stems 90 after assembly of stems 90 into guides 88), while outlet check valves 100 may be retained inside manifold 64 by associated plugs 102. In one embodiment, outlet check valves 100 may be biased against a seat 104 (i.e., biased into a closed position) by associated springs 106 located between outlet check valves 100 and plugs 102. When a pressure of fluid inside passages 96 (i.e., at a location between each barrel 82 and central cavity 98) creates a force on outlet check valves 100 that exceeds an opening force of springs 106, outlet check valves 100 may move away from seats 104 to allow flow through passages 96.
In some applications, a space inside tank 12 may be limited. In these applications, the amount of space (e.g., axial and/or radial space) consumed by manifold 64 may be important. For this reason, a size of manifold 64 may be reduced by strategically locating outlet check valves 100. In the disclosed embodiment of
Another embodiment of cold end 42 is illustrated in
Like plunger housing 62 of
Inlet manifold 110 of
Outlet manifold 112 may be generally cylindrical and fit almost entirely inside recess 114 of plunger housing 108. Outlet manifold 112 may be sealed against plunger housing 108 (e.g., by way of fasteners 66 shown at the bottom of inlet manifold 110), such that high-pressure fluid is retained in passages 96. Outlet manifold 112 may house central cavity 98 and portions of passages 96 (i.e., segments 96c) that extend from check valves 100 to central cavity 98. Passage 18 (not shown in
The cold end embodiment of
While the cold end embodiment of
Another embodiment of cold end 42 is illustrated in
Connecting flange 116 of
Plunger housing 118 of
Inlet manifold 120 of
The primary difference between the cold-end embodiment of
Although liners 122 are shown only in combination with the other components of the
The disclosed pump finds potential application in any fluid pumping application. For example the disclosed pump may be used in mobile (e.g., locomotive) or stationary (e.g., power generation) application having an internal combustion engine that consumes the fluid pressurized by the disclosed pump. The disclosed pump finds particular applicability in cryogenic applications, for example in applications having engines that burn LNG fuel. Operation of pump system 10 will now be explained.
Referring to
The disclosed pump may provide a high-pressure supply of fuel in a compact, simple, and robust configuration. The disclosed pump may be compact due to the strategic location of valves inside uniquely designed manifolds, which helps to reduce an axial and radial size of the pump. The disclosed pump may also be simple and robust due to the use of common manifolds, which may to help reduce part count. In addition, the use of replaceable plunger liners within the manifolds may allow for uncomplicated and low-cost remanufacturing of the pump.
It will be apparent to those skilled in the art that various modifications and variations can be made to the pump of the present disclosure. Other embodiments of the pump will be apparent to those skilled in the art from consideration of the specification and practice of the pump disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
