US20110020144A1 - Variable-volume head - Google Patents
Variable-volume head Download PDFInfo
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- US20110020144A1 US20110020144A1 US12/933,848 US93384809A US2011020144A1 US 20110020144 A1 US20110020144 A1 US 20110020144A1 US 93384809 A US93384809 A US 93384809A US 2011020144 A1 US2011020144 A1 US 2011020144A1
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- Prior art keywords
- plug
- threaded portion
- adjustment screw
- volume
- variable
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- Abandoned
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J1/00—Pistons; Trunk pistons; Plungers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
- F04B17/05—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by internal-combustion engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
- F04B35/002—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for driven by internal combustion engines
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
- F04B39/12—Casings; Cylinders; Cylinder heads; Fluid connections
- F04B39/125—Cylinder heads
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/16—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by adjusting the capacity of dead spaces of working chambers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
- F04B53/007—Cylinder heads
Definitions
- Embodiments of the present invention relate generally to compressors. More particularly, some embodiments of the present invention relate to compressors having variable-volume heads.
- a reciprocating compressor includes a piston and a cylinder.
- inlet valves temporarily open to allow the fluid to flow into the cylinder.
- the inlet valves close, and the piston is driven through the cylinder, reducing the volume of the cylinder in which the fluid is disposed and elevating the pressure of the fluid.
- the change in the volume of the cylinder during the compression stroke of the piston is referred to as the “swept volume.”
- an outlet valve is opened and the compressed fluid flows from the cylinder.
- Compressors are often characterized by their volumetric compression efficiency. This parameter is the ratio of the swept volume to the total volume of the cylinder that houses the fluid being compressed. A high volumetric efficiency generally correlates with a larger outlet pressure, as a substantial portion of the volume of the cylinder is swept by the piston, and a low volumetric efficiency generally correlates with a lower outlet pressure, as the percentage reduction in the cylinder's volume during a piston stroke is lower.
- the volumetric compression efficiency of a given compressor may not be matched to the system in which the compressor operates.
- a compressor design may be used in a variety of systems that expose the compressors to different conditions. For example, across systems, the compressor may be subject to varying inlet pressure or outlet pressure, as components upstream or downstream from the compressor may impede flow to or from the compressor to differing degrees in different applications. These variations and others can affect the performance of a compressor. Accordingly, it would be useful to be able to tune a compressor's volumetric compression efficiency according to characteristics of upstream and downstream components.
- FIG. 1 illustrates a partially-sectioned elevation view of an embodiment of a compressor
- FIG. 2 illustrates a cross-sectional elevation view of an embodiment of a variable-volume head that may be included in the compressor of FIG. 1 ;
- FIG. 3 illustrates a perspective view of an embodiment of a plug that may be included in the variable-volume head of FIG. 2 ;
- FIG. 4 illustrates a perspective view of an embodiment of an adjustment screw that may be included in the variable-volume head of FIG. 2 ;
- FIG. 5 illustrates a perspective view of the variable-volume head of FIG. 2 being adjusted in accordance with an embodiment of the present technique
- FIG. 6 illustrates a cross-sectional elevation view of the variable-volume head of FIG. 2 adjusted to increase volumetric compression efficiency in accordance with an embodiment of the present technique
- FIG. 7 illustrates another cross-sectional elevation view that is generally orthogonal to the views of FIGS. 2 and 6 ;
- FIG. 8 illustrates a block diagram of an embodiment of a gas-compression system.
- the articles “a,” “an,” “the,” “said,” and the like are intended to mean that there are one or more of the elements.
- the terms “comprising,” “including,” “having,” and the like are intended to be inclusive and mean that there may be additional elements other than the listed elements.
- the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components relative to some fixed reference, such as the direction of gravity.
- the term “fluid” encompasses liquids, gases, vapors, and combinations thereof.
- FIG. 1 illustrates an elevation view of an embodiment of a compressor 10 .
- the compressor 10 includes a variable-volume head 12 that adjusts the volume of a cylinder 14 of the compressor 10 .
- the variable-volume head 12 consumes relatively little space compared to conventional designs and is adjustable with relatively little force.
- the illustrated variable-volume head 12 is relatively resistant to ambient corrosive elements. Not all embodiments, however, provide all of these benefits, and some embodiments may provide other benefits. Before describing the variable-volume head 12 in detail, other features of the compressor 10 are described.
- the illustrated compressor 10 includes an engine 16 , a crank case 18 , a flywheel 20 , a piston 22 , a rod 24 , valves 26 and 28 , and a skid 30 .
- the engine 16 is a generally horizontally-mounted, internal-combustion engine with a reciprocating piston.
- the engine may be a spark-ignition engine or a compression-ignition engine, e.g., a diesel engine.
- Other embodiments may include other sources of mechanical power, such as electric motors or pneumatic drives.
- the engine 16 drives a rod coupled to a crankshaft in the crankcase 18 via a crosshead.
- the crankshaft in the crankcase 18 is coupled by an axle to the flywheel 20 , which provides an inertial mass that functions as a reservoir for angular momentum.
- the crankshaft in the crankcase 18 is also connected to the piston 22 via the rod 24 and another crosshead.
- the piston 22 and the cylinder 14 have a generally complementary generally right circular cylindrical shape that is generally concentric about a central axis 32 .
- the cylinder 14 includes inlet passages 34 and outlet passages 36 that are in fluid communication with the valves 26 and 28 .
- the valves 26 and 28 may include a variety of types of valve members, such as a plurality of poppet valves that are biased against openings connected to the passages 34 and 36 .
- the valves 26 and 28 are check valves configured to open in response to a pressure in the cylinder greater than a threshold pressure or less than a threshold pressure.
- the engine 16 drives the flywheel 20 and the piston 22 .
- the flywheel 20 rotates with the crankshaft in the crankcase 18
- the movement of the crankshaft causes the piston 22 to oscillate axially, back and forth through the cylinder 14 , as illustrated by arrow 38 .
- the valve 28 opens in response to the drop in pressure in the cylinder 14 , and fluid is drawn into the cylinder 14 through the inlet passage 34 .
- the valve 28 closes in response to the increase in pressure, and the piston 22 decreases the volume of this cylinder 14 in which the fluid is disposed, thereby elevating the fluid's pressure.
- valve 26 opens in response to the increase in pressure, and pressurized fluid exits the cylinder 14 through the outlet passage 36 .
- the valves 26 and 28 may be pressure-actuated valves, such as check valves.
- valve 28 may be a check valve configured to open in response to a fluid pressure in the cylinder 14 below some threshold, e.g., a partial vacuum, corresponding to an intake stroke
- valve 26 may be a check valve configured to open in response to a pressure in the cylinder 14 above some threshold corresponding to the end of a compression stroke.
- FIG. 2 illustrates a cross-sectional elevation view of an embodiment of the variable-volume head 12 .
- the variable-volume head 12 includes a head body 40 , a plug 42 , an adjustment screw 44 , a collar 46 , and a cap 48 .
- Each of these illustrated components 40 , 42 , 44 , 46 , and 48 is generally concentric about the central axis 32 and is made of steel or other appropriate materials.
- the head body 40 includes a flange 50 , a tubular portion 52 , and a distal portion 54 .
- the illustrated flange 50 is a generally annular member shaped to couple to a distal surface 56 of the cylinder 14 .
- the flange 50 may include a threaded aperture 58 for receiving an eye-bolt or other structures configured to support the variable-volume head 12 during installation.
- a mating surface 60 of the flange 50 may be generally orthogonal to the central axis 32 . Near the inner diameter of the mating surface 60 , the illustrated flange 50 includes a groove 62 and a lip 64 that extends axially beyond the mating surface 60 .
- a seal 66 such as an O-ring seal or a T-ring seal, is disposed in the groove 62 .
- the lip 64 overlaps a shoulder 68 near the distal portion of the cylinder 14 .
- a plurality of bolts 70 extend axially through the flange 50 and couple the variable-volume head 12 to threaded apertures in the cylinder 14 .
- other coupling mechanisms such as a weld, a lock ring, or threads, may be used to secure the variable-volume head 12 to the cylinder 14 .
- the tubular portion 52 extends generally perpendicular from the flange 50 and defines an interior 72 with a generally right-circular-cylindrical shape.
- the interior 72 may be generally concentric about the central axis 32 and generally coaxial with an interior 74 of the cylinder 14 .
- these volumes 72 and 74 are not coaxial or are not right circular cylinders, e.g., the variable-volume head 12 may be mounted to the side of the cylinder 14 and may extend generally radially or at an angle.
- the interior 72 may have a diameter 76 between about 5 inches and about 28 inches.
- the interior 72 may have other shapes, e.g., the interior 72 may be a generally right elliptical cylinder or it may have some other curvilinear or non-curvilinear shape.
- the distal portion 54 extends radially inward from the tubular portion 52 and is generally orthogonal to the central axis 32 .
- the distal portion 54 includes an aperture 78 and a mating surface 80 .
- the aperture 78 generally defines a right-circular-cylindrical volume that is generally concentric about and coaxial with the central axis 32 .
- the illustrated aperture 78 extends through the distal portion 54 to the interior 72 of the head body 40 .
- the mating surface 80 is generally perpendicular to the central axis 32 and is shaped to mate with a complementary surface on the collar 46 .
- the plug 42 is disposed in the interior 72 of the head body 40 .
- the plug 42 includes an outer tubular member 82 , a base 84 , and an inner tubular member 86 .
- the outer tubular member 82 in this embodiment, is generally concentric about, and coaxial with, the central axis 32 .
- the outer tubular member 82 includes a sealing surface 88 , generally annular grooves 90 and 92 , and a recessed portion 94 .
- the sealing surface 88 is generally complementary to the surface of the interior 72 of the head body 40 .
- the grooves 90 and 92 house seal members 96 and 98 that are configured to seal against the surface of the interior 72 of the head body 40 .
- the seal members 96 and 98 are carbon-filled-Teflon ring seals that are biased against the surface of the interior 72 of the head body 40 .
- the recessed portion 94 has a smaller diameter than the sealing surface 88 and is generally complementary to the interior 74 of the cylinder 14 .
- the illustrated base 84 extends radially between the outer tubular member 82 and the inner tubular member 86 and is generally orthogonal to the central axis 32 .
- the base 84 includes a recess 100 in which a distal portion of the adjustment screw 44 may be disposed.
- the inner tubular member 86 extends generally axially from the base 84 and is generally concentric about, and co-axial with, the central axis 32 .
- the inner tubular member 86 is disposed within the outer tubular member 82 .
- the illustrated inner tubular member 86 includes a fillet 102 near where the inner tubular member 86 meets the base 84 .
- a threaded aperture 104 extends through the inner tubular member 86 to the recess 100 .
- the threaded aperture 104 is generally coaxial with, and concentric about, the central axis 32 . Additional details of the plug 42 are described below with reference to FIG. 3 , which illustrates a perspective view of the plug 42 .
- the adjustment screw 44 is a generally right-circular-cylindrical member that extends generally coaxial with the central axis 32 .
- the illustrated adjustment screw 44 extends through the plug 42 , the collar 46 , and into the cap 48 .
- the presently described adjustment screw 44 includes a threaded portion 106 , a sealing surface 108 , another threaded portion 110 , another sealing surface 112 , and a tool interface 114 .
- the threaded portion 106 is configured to mate with the threaded aperture 104 of the plug 42
- the threaded portion 110 is configured to mate with complementary threads on the collar 46
- the sealing surface 108 is shaped to form a sliding and rotating seal with the collar 46 and the sealing surface 112 is shaped to form a generally static seal with the cap 48 .
- the sealing surfaces generally define right-circular cylindrical volumes.
- the collar 46 includes a tubular portion 116 , a flange 118 , and another tubular portion 120 .
- the tubular portion 116 includes a distal sealing surface 122 that is generally orthogonal to the central axis 32 .
- the illustrated tubular portion 116 also includes a breather aperture 124 that extends to a threaded aperture 126 through the collar 46 and a grease fitting 128 for lubricating the threaded aperture 126 .
- the breather aperture 124 may include a check valve or some other device configured to relieve pressure in the threaded aperture 126 . As explained below with reference to FIG.
- the threaded aperture 126 in this embodiment, is threaded in an opposite direction relative to the threaded aperture 104 in the plug 42 . Further, as is also explained below, the threads in the threaded aperture 126 may have a finer thread pitch then the threads in the threaded aperture 104 to reduce the movement of the adjustment screw 44 relative to movement of the plug 42 .
- the flange 118 is a generally annular member that extends generally perpendicular to the central axis 32 .
- a plurality of bolts 130 extend axially through the flange 118 and secure the collar 46 to threaded apertures in the head body 40 .
- the bolts 130 also transmit loads from the plug 42 to the head body 40 via the collar 46 . These forces are transmitted through the adjustment screw to the collar 46 by the coupling formed between the threaded portion 110 and the threaded aperture 126 .
- a seal member 132 such as an O-ring seal, is biased against the mating surface 80 of the head body 40 to form a seal.
- the illustrated tubular member 120 extends generally axially through the aperture 78 in the head body 40 .
- the interior of the tubular member 120 includes a non-threaded aperture 134 that is an extension of the threaded aperture 126 and a seal member 136 , such as a T-ring seal.
- a seal member 136 such as a T-ring seal.
- the distal portion of the tubular member 120 extends into the outer tubular member 82 of the plug 42 and abuts the inner tubular member 86 .
- the position of the plug 42 may be shifted relative to the collar 46 as the variable-volume head 12 is adjusted.
- the cap 48 includes an interior 138 and seals 140 and 142 .
- the cap 48 may be threaded to the adjustment screw 44 or it may be secured to the adjustment screw 44 with a friction fit or other coupling mechanism.
- the interior 138 of the cap 48 includes a generally conical tip 144 and a generally right-circular-cylindrical portion 146 extending through the remainder of the cap 48 .
- the seals 140 and 142 may include a variety of types of seals.
- the seal 142 may be a T-ring seal
- the seal 140 may be an O-ring seal.
- the seals 140 and 142 are formed with elastomers.
- the cap 48 may be removable from the adjustment screw 44 with or without tools.
- the cap 48 of the illustrated embodiment is removable by hand. As explained below, the cap 48 may be removed to access the tool interface 114 of the adjustment screw 44 . When the adjustment screw 44 is not being adjusted, the cap 48 is returned to the adjustment screw 44 to protect the adjustment screw 44 from the environment.
- FIG. 3 illustrates additional details of the plug 42 .
- the plug 42 includes a groove 148 .
- the illustrated groove 148 is recessed generally radially into the plug 42 , orthogonal to the central axis 32 , and extends generally parallel to the central axis 32 .
- the illustrated groove 148 does not penetrate entirely through the outer tubular member 82 , but it does extend axially along and radially into both the sealing surface 88 and the recessed portion 94 .
- the groove 148 includes a deeper portion 150 and a shallower portion 152 that produce a bottom surface 154 of the groove 148 that is a generally uniform distance away from the central axis 32 .
- the groove 148 is part of an anti-rotation device that impedes the plug 42 from rotating while allowing the plug 42 to translate axially.
- Some embodiments include a plurality of grooves like the groove 148 distributed around the plug 148 , e.g., two grooves 180 degrees apart.
- FIG. 4 illustrates additional details of the adjustment screw 44 .
- the threaded portion 106 and the threaded portion 110 include threads with different pitches and different orientations.
- the threaded portion 106 is right-handed, and the threaded portion 110 is left-handed. Consequently, rotation of the adjustment screw 44 in one direction tends to bring objects coupled to the threaded portions 106 and 110 toward one another, and rotation in the other direction tends to drive those objects away from one another.
- the orientation of the threads 106 and 110 may be reversed, or it may be the same.
- the pitch of the threaded portion 106 may be substantially greater than the pitch of the threaded portion 110 , such that a given amount of rotation of the adjustment screw 44 produces more movement in an object coupled to the threaded portion 106 than in an object coupled to the threaded portion 110 .
- the threaded portion 110 may have more than 4 threads per inch, e.g., generally equal to 8 threads or more per inch.
- the threaded portion 106 may have fewer than 4 threads per inch, e.g., generally equal to or less than 2 threads per inch. As explained below, having relatively fine pitched threads on the threaded portion 110 may result in relatively little axial movement of the adjustment screw 44 through the collar 80 ( FIG.
- the adjustment screw 44 does not translate axially as it rotates.
- the threaded portion 110 may be omitted (which is not to suggest that other features may not also be omitted), and an annular flange may extend generally radially from the adjustment screw 44 near where the threaded portion 110 is positioned.
- the flange may mate with an annular groove in the collar 46 ( FIG. 2 ), and together, these components may allow the adjustment screw 44 to rotate while generally axially constraining the adjustment screw 44 .
- the adjustment screw 44 may include an annular groove
- the collar 46 FIG. 2
- FIG. 5 illustrates the variable-volume head 12 being adjusted.
- the cap 48 is removed, and the adjustment screw 44 is rotated.
- the cap 48 is removed by un-threading the cap 48 from the adjustment screw 44 , or in other embodiments, the cap 48 is removed by applying an axial force to the cap 48 and overcoming friction that secures the cap 48 to the adjustment screw 44 .
- the cap 48 includes a gauge 156 that correlates axial movement of the adjustment screw 44 with changes in the volume of the interior 74 of the cylinder 14 ( FIG. 2 ) produced by movement of the plug 42 .
- the cap 48 is inverted and placed on the flange 118 of the collar 46 to axially align the gauge 156 with the variable-volume head 12 .
- an initial volume of the interior 74 of the cylinder 14 is determined by identifying which mark on the gauge 156 corresponds with an indicator on the adjustment screw 44 , such as the top of the adjustment screw 44 .
- the adjustment screw 44 is rotated to shift the position of the plug 42 .
- the range of motion of the plug 42 is illustrated by FIGS. 2 and 6 , which illustrate the plug 42 retracted and extended, respectively.
- the adjustment screw 44 may be rotated manually by applying a tool, such as a wrench or a wheel, to the tool interface 114 and rotating the tool about the axis 32 , as indicated by arrows 158 in FIG. 5 .
- the adjustment screw 44 may be rotated with a powered device, such as an electric motor or a pneumatic motor. As the adjustment screw 44 is rotated, the threaded portion 110 ( FIG. 4 ) cooperates with the threaded aperture 126 ( FIG.
- the gauge 156 ( FIG. 5 ) may be used to determine the change in volume of the interior 74 of the cylinder 14 ( FIG. 2 ).
- the new axial position of the adjustment screw 44 is correlated with a volume of the interior 74 by positioning the cap 48 on the flange 18 ( FIG. 2 ) and determining which mark on the gauge 156 generally corresponds with a given point on the adjustment screw 44 .
- the mark indicates the volume of the interior 74 ( FIG. 2 ) corresponding to the position of the adjustment screw 44 .
- FIG. 2 illustrates the plug 42 in its retracted position. In the retracted position, the volume of the interior 74 of the cylinder 14 is generally increased or maximized. As a result, in the state illustrated by FIG. 2 , the compressor 10 ( FIG. 1 ) operates with a relatively low, e.g., minimized, volumetric compression efficiency.
- the denominator is increased by retracting the plug 42 to the state illustrated by FIG. 2 . That is, the total volume is increased in the state illustrated by FIG. 2 .
- retracting the plug 42 and increasing the volume of the cylinder 14 reduces the volumetric compression efficiency, as the swept volume remains generally constant and the total volume of the cylinder is increased.
- FIG. 6 illustrates the plug 42 in its extended position.
- the plug 42 has penetrated into the interior 74 of the cylinder 14 , and as a result, the volume of the interior 74 is reduced.
- Decreasing the volume of the interior 74 increases, e.g., maximizes, the volumetric compression efficiency of the compressor 10 ( FIG. 1 ), as the denominator in the equation for volumetric compression efficiency is reduced by reducing the total volume of the interior 74 . That is, while the swept volume may remain generally constant, the total volume decreases.
- the plug 42 moves a larger axial distance 160 than the axial distance 162 moved by the adjustment screw 44 . This is due to the difference in the thread pitch of the threaded portions 106 and 110 ( FIG. 4 ).
- the distance 160 is larger than or generally equal to 2 times the distance 162 , 3 times the distance 162 , 4 times the distance 162 , or five times the distance 162 .
- the seals 96 and 98 and the threaded coupling between the threaded portion 106 and the threaded aperture 104 may impede or seal fluids from flowing between the interior 74 of the cylinder 14 and the interior 72 of the head body 40 . Should the pressure in the interior 72 rise, the seals 136 and 132 tend to prevent that pressure from driving fluid to the atmosphere.
- the threaded coupling between the relatively fine threads of the threaded portion 110 and the threaded aperture 126 in the collar 46 are believed to prevent debris from penetrating the collar 46 and entering the interior 72 of the head body 40 . This is believed to extend the useful life of the variable-volume head 12 .
- FIG. 7 illustrates another cross-section of the variable-volume head 12 that is generally orthogonal to the view illustrated by FIG. 6 .
- This view illustrates the operation of the groove 148 and a guide pin 164 to impede the plug 42 from rotating with the adjustment screw 44 .
- the illustrated guide pin 164 is a generally right-circular-cylindrical member that radially extends through the flange 50 , generally orthogonal to the central axis 32 into the groove 148 .
- the guide pin 164 applies a torque to the sidewalls of the groove 148 to impede or prevent the plug 42 from rotating.
- the guide pin 164 translates axially through the groove 148 as the plug 42 translates axially.
- the plug 42 may be characterized as having a single degree of freedom relative to the head body 40 .
- Some embodiments may include multiple grooves and guide pins.
- another groove and guide pin may be disposed opposite the guide pin 164 and groove 148 , e.g., about 180 degrees around the plug 42 .
- the groove 148 and guide pin 164 may be referred to as an anti-rotation device.
- Other embodiments may include other types of anti-rotation devices.
- the plug 42 and interior 72 may have a generally non-circular shape, such as a generally right-elliptical-cylindrical shape, that tends to impede rotation about the central axis 32 .
- the guide pin 164 may be positioned on the plug 42 , near the distal portion of the plug 42 , extending generally radially outward, and the groove 148 may be disposed in the inner walls of the cylinder 14 ( FIG. 2 ).
- the groove 148 is not necessarily straight, e.g., the groove 148 may spiral, causing the plug 42 to rotate as it translates axially, though the rotation may be less than the rotation of the adjustment screw 44 .
- FIG. 8 illustrates an example of a compression system 166 that includes the variable-volume head 12 described above.
- the system 166 includes a natural-gas well 168 , the engine 16 , a compressor 10 that includes the above-described variable-volume head 12 ( FIG. 2 ), and a pipeline, storage, or other fluid destination 169 .
- the gas well 168 may be a subsea or a surface natural gas well.
- the engine 16 may be a two-stroke combustion engine having between 40 and 800 hp, e.g., between 40 and 200 hp.
- natural gas flows from the gas well 168 to the compressor 10 , as illustrated by arrow 170 .
- a portion of this flow is diverted to the engine 16 , as illustrated by arrow 172 .
- the diverted flow of 172 may be conditioned by removing moisture or changing the gas pressure before being introduced to the engine 16 .
- the engine 16 combusts the diverted fuel 172 and drives a shaft 174 or other mechanical linkage, such as a crankshaft and rods, that powers the compressor 10 .
- the compressor 10 compresses the flow 170 from the gas well 168 and produces an outlet flow 176 at a higher pressure.
- the volumetric compression efficiency of the compressor 10 may be adjusted with the variable-volume head 12 ( FIG. 2 ) to account for the pressure of the inlet flow 170 or the outlet flow 176 .
- the outlet flow 169 flows to a fluid destination, such as a pipeline, storage, refining equipment, or other fluid destinations.
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Abstract
Description
- This application claims priority to PCT Application No. PCT/US2009/041468 entitled “Variable-Volume Head”, filed on Apr. 22, 2009, which is herein incorporated by reference in its entirety, and which claims priority to U.S. Provisional Patent Application No. 61/057,790, entitled “Variable-Volume Head”, filed on May 30, 2008, which is herein incorporated by reference in its entirety.
- Embodiments of the present invention relate generally to compressors. More particularly, some embodiments of the present invention relate to compressors having variable-volume heads.
- This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
- Reciprocating compressors are frequently used to compress and transport fluids, such as natural gas. Generally, a reciprocating compressor includes a piston and a cylinder. During compression, inlet valves temporarily open to allow the fluid to flow into the cylinder. Then, the inlet valves close, and the piston is driven through the cylinder, reducing the volume of the cylinder in which the fluid is disposed and elevating the pressure of the fluid. The change in the volume of the cylinder during the compression stroke of the piston is referred to as the “swept volume.” Near the end of the piston's travel, an outlet valve is opened and the compressed fluid flows from the cylinder.
- Compressors are often characterized by their volumetric compression efficiency. This parameter is the ratio of the swept volume to the total volume of the cylinder that houses the fluid being compressed. A high volumetric efficiency generally correlates with a larger outlet pressure, as a substantial portion of the volume of the cylinder is swept by the piston, and a low volumetric efficiency generally correlates with a lower outlet pressure, as the percentage reduction in the cylinder's volume during a piston stroke is lower.
- The volumetric compression efficiency of a given compressor may not be matched to the system in which the compressor operates. A compressor design may be used in a variety of systems that expose the compressors to different conditions. For example, across systems, the compressor may be subject to varying inlet pressure or outlet pressure, as components upstream or downstream from the compressor may impede flow to or from the compressor to differing degrees in different applications. These variations and others can affect the performance of a compressor. Accordingly, it would be useful to be able to tune a compressor's volumetric compression efficiency according to characteristics of upstream and downstream components.
- These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
-
FIG. 1 illustrates a partially-sectioned elevation view of an embodiment of a compressor; -
FIG. 2 illustrates a cross-sectional elevation view of an embodiment of a variable-volume head that may be included in the compressor ofFIG. 1 ; -
FIG. 3 illustrates a perspective view of an embodiment of a plug that may be included in the variable-volume head ofFIG. 2 ; -
FIG. 4 illustrates a perspective view of an embodiment of an adjustment screw that may be included in the variable-volume head ofFIG. 2 ; -
FIG. 5 illustrates a perspective view of the variable-volume head ofFIG. 2 being adjusted in accordance with an embodiment of the present technique; -
FIG. 6 illustrates a cross-sectional elevation view of the variable-volume head ofFIG. 2 adjusted to increase volumetric compression efficiency in accordance with an embodiment of the present technique; -
FIG. 7 illustrates another cross-sectional elevation view that is generally orthogonal to the views ofFIGS. 2 and 6 ; and -
FIG. 8 illustrates a block diagram of an embodiment of a gas-compression system. - One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
- When introducing elements of various embodiments, the articles “a,” “an,” “the,” “said,” and the like, are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “having,” and the like are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components relative to some fixed reference, such as the direction of gravity. The term “fluid” encompasses liquids, gases, vapors, and combinations thereof.
-
FIG. 1 illustrates an elevation view of an embodiment of acompressor 10. In this embodiment, thecompressor 10 includes a variable-volume head 12 that adjusts the volume of acylinder 14 of thecompressor 10. As explained below, the variable-volume head 12 consumes relatively little space compared to conventional designs and is adjustable with relatively little force. Additionally, the illustrated variable-volume head 12 is relatively resistant to ambient corrosive elements. Not all embodiments, however, provide all of these benefits, and some embodiments may provide other benefits. Before describing the variable-volume head 12 in detail, other features of thecompressor 10 are described. - The illustrated
compressor 10 includes anengine 16, acrank case 18, aflywheel 20, apiston 22, arod 24,valves skid 30. In this embodiment, theengine 16 is a generally horizontally-mounted, internal-combustion engine with a reciprocating piston. The engine may be a spark-ignition engine or a compression-ignition engine, e.g., a diesel engine. Other embodiments may include other sources of mechanical power, such as electric motors or pneumatic drives. In operation, theengine 16 drives a rod coupled to a crankshaft in thecrankcase 18 via a crosshead. The crankshaft in thecrankcase 18 is coupled by an axle to theflywheel 20, which provides an inertial mass that functions as a reservoir for angular momentum. The crankshaft in thecrankcase 18 is also connected to thepiston 22 via therod 24 and another crosshead. Thepiston 22 and thecylinder 14 have a generally complementary generally right circular cylindrical shape that is generally concentric about acentral axis 32. Thecylinder 14 includesinlet passages 34 andoutlet passages 36 that are in fluid communication with thevalves valves passages valves - In operation, the
engine 16 drives theflywheel 20 and thepiston 22. As theflywheel 20 rotates with the crankshaft in thecrankcase 18, the movement of the crankshaft causes thepiston 22 to oscillate axially, back and forth through thecylinder 14, as illustrated byarrow 38. While thepiston 22 moves back toward thecrankcase 18, thevalve 28 opens in response to the drop in pressure in thecylinder 14, and fluid is drawn into thecylinder 14 through theinlet passage 34. Then, as thepiston 22 translates away from thecrankcase 18, thevalve 28 closes in response to the increase in pressure, and thepiston 22 decreases the volume of thiscylinder 14 in which the fluid is disposed, thereby elevating the fluid's pressure. As noted above, the portion of thecylinder 14 through which the surface of thepiston 22 translates is referred to as the swept volume of thecylinder 14. As thepiston 22 nears the end of its travel away from thecrankcase 18, thevalve 26 opens in response to the increase in pressure, and pressurized fluid exits thecylinder 14 through theoutlet passage 36. In some embodiments, thevalves valve 28 may be a check valve configured to open in response to a fluid pressure in thecylinder 14 below some threshold, e.g., a partial vacuum, corresponding to an intake stroke, and thevalve 26 may be a check valve configured to open in response to a pressure in thecylinder 14 above some threshold corresponding to the end of a compression stroke. -
FIG. 2 illustrates a cross-sectional elevation view of an embodiment of the variable-volume head 12. In this embodiment, the variable-volume head 12 includes ahead body 40, aplug 42, anadjustment screw 44, acollar 46, and acap 48. Each of these illustratedcomponents central axis 32 and is made of steel or other appropriate materials. - In the illustrated embodiment, the
head body 40 includes aflange 50, atubular portion 52, and adistal portion 54. The illustratedflange 50 is a generally annular member shaped to couple to adistal surface 56 of thecylinder 14. Theflange 50 may include a threadedaperture 58 for receiving an eye-bolt or other structures configured to support the variable-volume head 12 during installation. Amating surface 60 of theflange 50 may be generally orthogonal to thecentral axis 32. Near the inner diameter of themating surface 60, the illustratedflange 50 includes agroove 62 and alip 64 that extends axially beyond themating surface 60. Aseal 66, such as an O-ring seal or a T-ring seal, is disposed in thegroove 62. Thelip 64 overlaps ashoulder 68 near the distal portion of thecylinder 14. A plurality ofbolts 70 extend axially through theflange 50 and couple the variable-volume head 12 to threaded apertures in thecylinder 14. In other embodiments, other coupling mechanisms, such as a weld, a lock ring, or threads, may be used to secure the variable-volume head 12 to thecylinder 14. - The
tubular portion 52, in this embodiment, extends generally perpendicular from theflange 50 and defines an interior 72 with a generally right-circular-cylindrical shape. The interior 72 may be generally concentric about thecentral axis 32 and generally coaxial with an interior 74 of thecylinder 14. In other embodiments, thesevolumes volume head 12 may be mounted to the side of thecylinder 14 and may extend generally radially or at an angle. The interior 72 may have adiameter 76 between about 5 inches and about 28 inches. In other embodiments, the interior 72 may have other shapes, e.g., the interior 72 may be a generally right elliptical cylinder or it may have some other curvilinear or non-curvilinear shape. Thedistal portion 54 extends radially inward from thetubular portion 52 and is generally orthogonal to thecentral axis 32. In this embodiment, thedistal portion 54 includes anaperture 78 and amating surface 80. Theaperture 78 generally defines a right-circular-cylindrical volume that is generally concentric about and coaxial with thecentral axis 32. The illustratedaperture 78 extends through thedistal portion 54 to the interior 72 of thehead body 40. Themating surface 80 is generally perpendicular to thecentral axis 32 and is shaped to mate with a complementary surface on thecollar 46. - As illustrated by
FIG. 2 , theplug 42 is disposed in theinterior 72 of thehead body 40. In some embodiments, theplug 42 includes anouter tubular member 82, abase 84, and aninner tubular member 86. The outertubular member 82, in this embodiment, is generally concentric about, and coaxial with, thecentral axis 32. The outertubular member 82 includes a sealingsurface 88, generallyannular grooves portion 94. The sealingsurface 88 is generally complementary to the surface of the interior 72 of thehead body 40. Thegrooves house seal members head body 40. In some embodiments, theseal members head body 40. The recessedportion 94 has a smaller diameter than the sealingsurface 88 and is generally complementary to the interior 74 of thecylinder 14. - The illustrated
base 84 extends radially between the outertubular member 82 and theinner tubular member 86 and is generally orthogonal to thecentral axis 32. In this embodiment, thebase 84 includes arecess 100 in which a distal portion of theadjustment screw 44 may be disposed. - In the present embodiment, the
inner tubular member 86 extends generally axially from thebase 84 and is generally concentric about, and co-axial with, thecentral axis 32. Theinner tubular member 86 is disposed within the outertubular member 82. The illustratedinner tubular member 86 includes afillet 102 near where theinner tubular member 86 meets thebase 84. A threadedaperture 104 extends through theinner tubular member 86 to therecess 100. The threadedaperture 104 is generally coaxial with, and concentric about, thecentral axis 32. Additional details of theplug 42 are described below with reference toFIG. 3 , which illustrates a perspective view of theplug 42. - In this embodiment, the
adjustment screw 44 is a generally right-circular-cylindrical member that extends generally coaxial with thecentral axis 32. The illustratedadjustment screw 44 extends through theplug 42, thecollar 46, and into thecap 48. The presently describedadjustment screw 44 includes a threadedportion 106, a sealingsurface 108, another threadedportion 110, another sealingsurface 112, and atool interface 114. These features of theadjustment screw 44 are described further below with reference toFIG. 4 , which illustrates a perspective view of theadjustment screw 44. With reference toFIG. 2 , it should be noted that the threadedportion 106 is configured to mate with the threadedaperture 104 of theplug 42, and the threadedportion 110 is configured to mate with complementary threads on thecollar 46. The sealingsurface 108 is shaped to form a sliding and rotating seal with thecollar 46 and the sealingsurface 112 is shaped to form a generally static seal with thecap 48. In some embodiments, the sealing surfaces generally define right-circular cylindrical volumes. - In the illustrated embodiment, the
collar 46 includes atubular portion 116, aflange 118, and anothertubular portion 120. Thetubular portion 116 includes adistal sealing surface 122 that is generally orthogonal to thecentral axis 32. The illustratedtubular portion 116 also includes abreather aperture 124 that extends to a threadedaperture 126 through thecollar 46 and agrease fitting 128 for lubricating the threadedaperture 126. Thebreather aperture 124 may include a check valve or some other device configured to relieve pressure in the threadedaperture 126. As explained below with reference toFIG. 4 , which illustrates complementary structures on theadjustment screw 44, the threadedaperture 126, in this embodiment, is threaded in an opposite direction relative to the threadedaperture 104 in theplug 42. Further, as is also explained below, the threads in the threadedaperture 126 may have a finer thread pitch then the threads in the threadedaperture 104 to reduce the movement of theadjustment screw 44 relative to movement of theplug 42. - The
flange 118 is a generally annular member that extends generally perpendicular to thecentral axis 32. A plurality ofbolts 130 extend axially through theflange 118 and secure thecollar 46 to threaded apertures in thehead body 40. Thebolts 130 also transmit loads from theplug 42 to thehead body 40 via thecollar 46. These forces are transmitted through the adjustment screw to thecollar 46 by the coupling formed between the threadedportion 110 and the threadedaperture 126. Aseal member 132, such as an O-ring seal, is biased against themating surface 80 of thehead body 40 to form a seal. - The illustrated
tubular member 120 extends generally axially through theaperture 78 in thehead body 40. The interior of thetubular member 120 includes anon-threaded aperture 134 that is an extension of the threadedaperture 126 and aseal member 136, such as a T-ring seal. In the state illustrated byFIG. 2 , the distal portion of thetubular member 120 extends into the outertubular member 82 of theplug 42 and abuts theinner tubular member 86. However, as explained below, the position of theplug 42 may be shifted relative to thecollar 46 as the variable-volume head 12 is adjusted. - In this embodiment, the
cap 48 includes an interior 138 andseals cap 48 may be threaded to theadjustment screw 44 or it may be secured to theadjustment screw 44 with a friction fit or other coupling mechanism. Theinterior 138 of thecap 48 includes a generallyconical tip 144 and a generally right-circular-cylindrical portion 146 extending through the remainder of thecap 48. Theseals seal 142 may be a T-ring seal, and theseal 140 may be an O-ring seal. In some embodiments, theseals cap 48 may be removable from theadjustment screw 44 with or without tools. For example, thecap 48 of the illustrated embodiment is removable by hand. As explained below, thecap 48 may be removed to access thetool interface 114 of theadjustment screw 44. When theadjustment screw 44 is not being adjusted, thecap 48 is returned to theadjustment screw 44 to protect theadjustment screw 44 from the environment. -
FIG. 3 illustrates additional details of theplug 42. In this embodiment, theplug 42 includes agroove 148. The illustratedgroove 148 is recessed generally radially into theplug 42, orthogonal to thecentral axis 32, and extends generally parallel to thecentral axis 32. The illustratedgroove 148 does not penetrate entirely through the outertubular member 82, but it does extend axially along and radially into both the sealingsurface 88 and the recessedportion 94. Thegroove 148 includes adeeper portion 150 and ashallower portion 152 that produce abottom surface 154 of thegroove 148 that is a generally uniform distance away from thecentral axis 32. As explained below, thegroove 148 is part of an anti-rotation device that impedes theplug 42 from rotating while allowing theplug 42 to translate axially. Some embodiments include a plurality of grooves like thegroove 148 distributed around theplug 148, e.g., two grooves 180 degrees apart. -
FIG. 4 illustrates additional details of theadjustment screw 44. As illustrated, the threadedportion 106 and the threadedportion 110 include threads with different pitches and different orientations. In some embodiments, the threadedportion 106 is right-handed, and the threadedportion 110 is left-handed. Consequently, rotation of theadjustment screw 44 in one direction tends to bring objects coupled to the threadedportions threads portions portions portions FIG. 2 ) axially. As theadjustment screw 44 is rotated, the threadedportion 110 pushes against the collar 46 (FIG. 2 ), and the threadedportion 110 pushes in the same direction against the plug 42 (FIG. 2 ). - The pitch of the threaded
portion 106 may be substantially greater than the pitch of the threadedportion 110, such that a given amount of rotation of theadjustment screw 44 produces more movement in an object coupled to the threadedportion 106 than in an object coupled to the threadedportion 110. For instance, the threadedportion 110 may have more than 4 threads per inch, e.g., generally equal to 8 threads or more per inch. In addition, the threadedportion 106 may have fewer than 4 threads per inch, e.g., generally equal to or less than 2 threads per inch. As explained below, having relatively fine pitched threads on the threadedportion 110 may result in relatively little axial movement of theadjustment screw 44 through the collar 80 (FIG. 2 ) during adjustment, thereby reducing the volume of space consumed by the variable-volume head 12 (FIG. 2 ) as theadjustment screw 44 is adjusted between its maximum and minimum positions. Further, including relatively coarse threads in the threadedportion 106 tends to produce a relatively large movement of the plug 42 (FIG. 2 ) for a given amount of rotation of theadjustment screw 44, which also tends to reduce the amount of space consumed by the variable-volume head 12, as the plug 42 (FIG. 2 ) can reach its maximum and minimum positions with relatively little movement of theadjustment screw 44. - In some embodiments, the
adjustment screw 44 does not translate axially as it rotates. For example, the threadedportion 110 may be omitted (which is not to suggest that other features may not also be omitted), and an annular flange may extend generally radially from theadjustment screw 44 near where the threadedportion 110 is positioned. The flange may mate with an annular groove in the collar 46 (FIG. 2 ), and together, these components may allow theadjustment screw 44 to rotate while generally axially constraining theadjustment screw 44. In another example, theadjustment screw 44 may include an annular groove, and the collar 46 (FIG. 2 ) may include an annular flange that extends generally radially inward into the groove, thereby impeding axial movement of theadjustment screw 44 while allowing rotation. -
FIG. 5 illustrates the variable-volume head 12 being adjusted. To shift the position of theplug 42, and thereby adjust the volume of the interior 74 of the cylinder 14 (FIG. 2 ), thecap 48 is removed, and theadjustment screw 44 is rotated. In some embodiments, thecap 48 is removed by un-threading thecap 48 from theadjustment screw 44, or in other embodiments, thecap 48 is removed by applying an axial force to thecap 48 and overcoming friction that secures thecap 48 to theadjustment screw 44. - In some embodiments, the
cap 48 includes agauge 156 that correlates axial movement of theadjustment screw 44 with changes in the volume of the interior 74 of the cylinder 14 (FIG. 2 ) produced by movement of theplug 42. To use thegauge 156, thecap 48 is inverted and placed on theflange 118 of thecollar 46 to axially align thegauge 156 with the variable-volume head 12. Then, an initial volume of the interior 74 of the cylinder 14 (FIG. 2 ) is determined by identifying which mark on thegauge 156 corresponds with an indicator on theadjustment screw 44, such as the top of theadjustment screw 44. - After taking an initial reading, the
adjustment screw 44 is rotated to shift the position of theplug 42. The range of motion of theplug 42 is illustrated byFIGS. 2 and 6 , which illustrate theplug 42 retracted and extended, respectively. Theadjustment screw 44 may be rotated manually by applying a tool, such as a wrench or a wheel, to thetool interface 114 and rotating the tool about theaxis 32, as indicated byarrows 158 inFIG. 5 . In some embodiments, theadjustment screw 44 may be rotated with a powered device, such as an electric motor or a pneumatic motor. As theadjustment screw 44 is rotated, the threaded portion 110 (FIG. 4 ) cooperates with the threaded aperture 126 (FIG. 2 ) to axially shift both theadjustment screw 44 and the plug 42 (FIG. 6 ). As theadjustment screw 44 rotates and translates axially, it both carries theplug 42 and rotates within theplug 42. Theplug 42 is impeded from rotating with theadjustment screw 42 by a member, such as a guide pin (an example of which is described below with reference toFIG. 7 ), disposed in thegroove 148 and mounted to thehead body 40. The rotation of the threadedportion 106 within the threaded aperture 104 (FIG. 2 ) of theplug 42 causes theplug 42 to translate axially along theadjustment screw 44, which is itself also translating axially due to the threaded portion 110 (FIG. 4 ). Thus, the axial movement of theadjustment screw 44 relative to thecollar 46 and the axial movement of theplug 42 relative to theadjustment screw 44 add together to yield a net movement of theplug 42 that is larger than either individual axial movement. - After adjusting the
adjustment screw 44, the gauge 156 (FIG. 5 ) may be used to determine the change in volume of the interior 74 of the cylinder 14 (FIG. 2 ). The new axial position of theadjustment screw 44 is correlated with a volume of the interior 74 by positioning thecap 48 on the flange 18 (FIG. 2 ) and determining which mark on thegauge 156 generally corresponds with a given point on theadjustment screw 44. The mark indicates the volume of the interior 74 (FIG. 2 ) corresponding to the position of theadjustment screw 44. - As mentioned above, the range of movement of the
plug 42 is illustrated by comparingFIG. 2 andFIG. 6 .FIG. 2 illustrates theplug 42 in its retracted position. In the retracted position, the volume of the interior 74 of thecylinder 14 is generally increased or maximized. As a result, in the state illustrated byFIG. 2 , the compressor 10 (FIG. 1 ) operates with a relatively low, e.g., minimized, volumetric compression efficiency. In the equation for volumetric compression efficiency, i.e., the swept volume divided by the total volume of the cylinder 14 (FIG. 1 ), the denominator is increased by retracting theplug 42 to the state illustrated byFIG. 2 . That is, the total volume is increased in the state illustrated byFIG. 2 . Thus, retracting theplug 42 and increasing the volume of thecylinder 14 reduces the volumetric compression efficiency, as the swept volume remains generally constant and the total volume of the cylinder is increased. - In contrast,
FIG. 6 illustrates theplug 42 in its extended position. In this state, theplug 42 has penetrated into the interior 74 of thecylinder 14, and as a result, the volume of the interior 74 is reduced. Decreasing the volume of the interior 74 increases, e.g., maximizes, the volumetric compression efficiency of the compressor 10 (FIG. 1 ), as the denominator in the equation for volumetric compression efficiency is reduced by reducing the total volume of the interior 74. That is, while the swept volume may remain generally constant, the total volume decreases. - As illustrated by
FIG. 6 , theplug 42 moves a larger axial distance 160 than the axial distance 162 moved by theadjustment screw 44. This is due to the difference in the thread pitch of the threadedportions 106 and 110 (FIG. 4 ). In some embodiments, the distance 160 is larger than or generally equal to 2 times the distance 162, 3 times the distance 162, 4 times the distance 162, or five times the distance 162. - The
seals portion 106 and the threadedaperture 104 may impede or seal fluids from flowing between the interior 74 of thecylinder 14 and the interior 72 of thehead body 40. Should the pressure in the interior 72 rise, theseals - Further, the threaded coupling between the relatively fine threads of the threaded
portion 110 and the threadedaperture 126 in thecollar 46 are believed to prevent debris from penetrating thecollar 46 and entering the interior 72 of thehead body 40. This is believed to extend the useful life of the variable-volume head 12. -
FIG. 7 illustrates another cross-section of the variable-volume head 12 that is generally orthogonal to the view illustrated byFIG. 6 . This view illustrates the operation of thegroove 148 and aguide pin 164 to impede theplug 42 from rotating with theadjustment screw 44. The illustratedguide pin 164 is a generally right-circular-cylindrical member that radially extends through theflange 50, generally orthogonal to thecentral axis 32 into thegroove 148. Theguide pin 164 applies a torque to the sidewalls of thegroove 148 to impede or prevent theplug 42 from rotating. Theguide pin 164 translates axially through thegroove 148 as theplug 42 translates axially. In some embodiments, theplug 42 may be characterized as having a single degree of freedom relative to thehead body 40. Some embodiments may include multiple grooves and guide pins. For example, another groove and guide pin may be disposed opposite theguide pin 164 andgroove 148, e.g., about 180 degrees around theplug 42. - The
groove 148 andguide pin 164, together, may be referred to as an anti-rotation device. Other embodiments may include other types of anti-rotation devices. For example, theplug 42 and interior 72 may have a generally non-circular shape, such as a generally right-elliptical-cylindrical shape, that tends to impede rotation about thecentral axis 32. In another example, theguide pin 164 may be positioned on theplug 42, near the distal portion of theplug 42, extending generally radially outward, and thegroove 148 may be disposed in the inner walls of the cylinder 14 (FIG. 2 ). In some embodiments, thegroove 148 is not necessarily straight, e.g., thegroove 148 may spiral, causing theplug 42 to rotate as it translates axially, though the rotation may be less than the rotation of theadjustment screw 44. -
FIG. 8 illustrates an example of acompression system 166 that includes the variable-volume head 12 described above. Thesystem 166 includes a natural-gas well 168, theengine 16, acompressor 10 that includes the above-described variable-volume head 12 (FIG. 2 ), and a pipeline, storage, orother fluid destination 169. The gas well 168 may be a subsea or a surface natural gas well. Theengine 16 may be a two-stroke combustion engine having between 40 and 800 hp, e.g., between 40 and 200 hp. - In operation, natural gas flows from the gas well 168 to the
compressor 10, as illustrated byarrow 170. A portion of this flow is diverted to theengine 16, as illustrated byarrow 172. The diverted flow of 172 may be conditioned by removing moisture or changing the gas pressure before being introduced to theengine 16. Theengine 16 combusts the divertedfuel 172 and drives ashaft 174 or other mechanical linkage, such as a crankshaft and rods, that powers thecompressor 10. Thecompressor 10 compresses theflow 170 from the gas well 168 and produces anoutlet flow 176 at a higher pressure. The volumetric compression efficiency of thecompressor 10 may be adjusted with the variable-volume head 12 (FIG. 2 ) to account for the pressure of theinlet flow 170 or theoutlet flow 176. Theoutlet flow 169 flows to a fluid destination, such as a pipeline, storage, refining equipment, or other fluid destinations. - While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
Claims (20)
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US20150110657A1 (en) * | 2013-10-18 | 2015-04-23 | Hoerbiger Kompressortechnik Holding Gmbh | Adjusting Device for an Adjusting Piston of a Variable Clearance Space of a Reciprocating Compressor |
EP2955380A4 (en) * | 2013-02-07 | 2017-01-11 | Wen-San Chou | Air compressor apparatus |
US10263547B2 (en) * | 2014-10-09 | 2019-04-16 | Direct Drive Systems, Inc. | Permanent magnet motor control for electric subsea pump |
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ITMI20112392A1 (en) * | 2011-12-27 | 2013-06-28 | Nuovo Pignone Spa | EQUIPMENT AND METHODS FOR IMPLEMENTING VALVES |
ITMI20112393A1 (en) * | 2011-12-27 | 2013-06-28 | Nuovo Pignone Spa | ROTO-TRANSLATING ACTIVATED ROTARY VALVES FOR ALTERNATIVE COMPRESSORS AND RELATED METHODS |
ITMI20112391A1 (en) | 2011-12-27 | 2013-06-28 | Nuovo Pignone Spa | DEVICES AND METHODS TO IMPLEMENT VALVES |
ITMI20112396A1 (en) * | 2011-12-27 | 2013-06-28 | Nuovo Pignone Spa | ROTARY VALVES WITH CLOSING PROFILES BETWEEN STATOR AND ROTOR AND RELATED METHODS |
US11220877B2 (en) * | 2018-04-27 | 2022-01-11 | Sean P. Thomas | Protective cap assembly for subsea equipment |
US10907433B2 (en) * | 2018-04-27 | 2021-02-02 | Sean P. Thomas | Protective cap assembly for subsea equipment |
CN108869235A (en) * | 2018-07-04 | 2018-11-23 | 蚌埠艾普压缩机制造有限公司 | A kind of pressure adjusting cylinder for hydrogenation stations high pressure hydrogen compressor |
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2009
- 2009-04-22 WO PCT/US2009/041468 patent/WO2009146222A1/en active Application Filing
- 2009-04-22 GB GB1021730.5A patent/GB2472961B/en active Active
- 2009-04-22 BR BRPI0912310A patent/BRPI0912310A2/en not_active IP Right Cessation
- 2009-04-22 US US12/933,848 patent/US20110020144A1/en not_active Abandoned
- 2009-04-22 GB GB1212335.2A patent/GB2489631B/en active Active
-
2010
- 2010-10-13 NO NO20101423A patent/NO20101423L/en not_active Application Discontinuation
-
2014
- 2014-05-24 US US14/287,011 patent/US9897207B2/en active Active
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US1586278A (en) * | 1925-06-27 | 1926-05-25 | Brunswickkroeschell Company | Clearance pocket |
US2047167A (en) * | 1932-04-13 | 1936-07-07 | Baldwin Southwark Corp | Adjustable clearance mechanism |
US2342830A (en) * | 1941-08-30 | 1944-02-29 | Lummus Co | Micrometer control |
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US3174677A (en) * | 1962-03-30 | 1965-03-23 | Phillips Petroleum Co | Variable clearance bottle for gas compressors and gas leakage sealing means therefor |
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US20050175476A1 (en) * | 2004-02-09 | 2005-08-11 | Energy Xtraction Corporation | Gas well liquid recovery |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2955380A4 (en) * | 2013-02-07 | 2017-01-11 | Wen-San Chou | Air compressor apparatus |
US20150110657A1 (en) * | 2013-10-18 | 2015-04-23 | Hoerbiger Kompressortechnik Holding Gmbh | Adjusting Device for an Adjusting Piston of a Variable Clearance Space of a Reciprocating Compressor |
US10954937B2 (en) * | 2013-10-18 | 2021-03-23 | Hoerbiger Wien Gmbh | Adjusting device for an adjusting piston of a variable clearance space of a reciprocating compressor |
US10263547B2 (en) * | 2014-10-09 | 2019-04-16 | Direct Drive Systems, Inc. | Permanent magnet motor control for electric subsea pump |
Also Published As
Publication number | Publication date |
---|---|
GB2472961B (en) | 2013-02-27 |
NO20101423L (en) | 2010-11-24 |
GB2489631B (en) | 2013-02-13 |
GB2489631A (en) | 2012-10-03 |
GB2472961A (en) | 2011-02-23 |
US20140338526A1 (en) | 2014-11-20 |
BRPI0912310A2 (en) | 2017-12-26 |
US9897207B2 (en) | 2018-02-20 |
GB201021730D0 (en) | 2011-02-02 |
GB201212335D0 (en) | 2012-08-22 |
WO2009146222A1 (en) | 2009-12-03 |
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