Patent Application
20220220958
The present invention relates to solids handling in rotary positive displacement machines where the machines are based on trochoidal geometry. In at least some embodiments the machines comprise a helical rotor that undergoes planetary motion relative to a helical stator.
Rotary machines, in which at least one rotor has planetary motion within a stator or housing, can be employed, for example, as positive displacement pumps, rotary compressors, vacuum pumps, expansion engines, and the like.
Pumps are devices that can move a working fluid from one place to another. There is a wide range of end uses for various types of pumps, including irrigation, fire-fighting, flood control, water supply, gasoline supply, refrigeration, chemical movement and sewage transfer. Rotary pumps are typically positive displacement pumps comprising a fixed housing, gears, cams, rotors, vanes and/or similar elements. Rotary pumps usually have close running clearances (only a small distance or gap between their moving and stationary parts), do not require suction or discharge valves, and are often lubricated only by the fluid being pumped.
A positive displacement pump moves fluid by trapping a volume of fluid in a chamber and forcing the trapped volume into a discharge pipe. Some positive displacement pumps employ an expanding chamber on the suction side and a decreasing chamber on the discharge side. Fluid flows into the pump intake as the chamber on the suction side expands, and the fluid flows out of the discharge pipe as the chamber collapses. The output volume is the same for each cycle of operation. An ideal positive displacement pump can produce the same flow rate at a given pump speed regardless of the discharge pressure.
Progressive cavity pumps (PCPs) are one type of rotary positive displacement machine that can offer advantages for certain applications. In PCPs, a rotor is disposed and rotates eccentrically within a helical stator cavity. The fluid to be pumped follows a helical path along the pump axis. The rotor is typically formed of rigid material and the stator (or stator lining) of resilient or elastomeric material. In some PCPs, an elastomeric stator can facilitate sealing and improve abrasion resistance. In some PCPs, the elastomeric stator can deform to partially accommodate solids in the fluid that is being pumped by the PCP.
Various classes of rotary machines based on trochoidal geometries are also known. Such rotary machines comprise a rotor or stator whose cross-section is bounded by a certain family of curves, known as trochoids or trochoidal shapes. These include rotating lobe machines with the following configurations:
(1) rotary machines in which the rotor is hypotrochoidal in cross-section, and undergoes planetary motion (spins about its axis and orbits eccentrically) within a stator that is shaped as an outer envelope of that rotor (with the rotor having one more apex or lobe than the stator cavity);
(2) rotary machines in which the stator cavity is hypotrochoidal in cross-section, and the rotor undergoes planetary motion within the stator and is shaped as the inner envelope of that stator (with the rotor having one less apex or lobe than the stator cavity);
(3) rotary machines in which the rotor is epitrochoidal in cross-section, and undergoes planetary motion within a stator that is shaped as an outer envelope of that rotor (with the rotor having one less apex or lobe than the stator cavity); and
(4) rotary machines in which the stator cavity is epitrochoidal in cross-section, and the rotor undergoes planetary motion within the stator and is shaped as the inner envelope of that stator (with the rotor having one more apex or lobe than the stator cavity).
Thus, in all of these configurations, the rotor or stator is a trochoidal component, meaning it has a cross-sectional shape that is a trochoid. Generally, as used herein, an object is said to undergo “planetary motion” when it spins about one axis and orbits about another axis. Such rotary machines, such as those described above, can be designed for various applications including, for example, as pumps, compressors, and expansion engines. The design, configuration and operation of different rotary machines can offer particular advantages for certain applications.
In some end-use applications, it can be important, or at least desirable, for rotary machines to be able to tolerate the presence of solids in the fluid stream being handled by the machine. Solids can cause jamming, abrasive wear of components and/or premature failure of the machine.
In at least some of a first set of embodiments, a rotary machine comprises a stator and a rotor. The rotor has a rotor helical profile, a rotor axis, and a hypotrochoidal shape at any cross-section transverse to the rotor axis, along at least a portion of a length of the rotor. The rotor is disposed within the stator and is configured to undergo planetary motion relative to the stator. The stator has a stator helical profile, a stator axis, and a shape at any cross-section transverse to the stator axis along at least a portion of a length of the stator that is an outer envelope formed when the hypotrochoidal shape of the rotor undergoes planetary motion. In some of the first set of embodiments the hypotrochoidal shape has n lobes, where n is an integer, the outer envelope shape has (n−1) lobes, the pitch of the rotor is the same as the pitch of the stator; and the ratio of the lead of the rotor to the lead of the stator is n:(n−1). In some such embodiments the hypotrochoidal shape is an ellipse, and n=2.
In at least some of a second set of embodiments, a rotary machine rotary machine comprises a stator and a rotor. The rotor has a helical profile, a rotor axis, and a rotor shape that is inwardly offset from a hypotrochoidal shape at any cross-section transverse to the rotor axis, along at least a portion of a length of the rotor. The rotor is disposed within the stator and is configured to undergo planetary motion relative to the stator. The stator has a stator axis, a helical profile, and a stator shape at any cross-section transverse to the stator axis along at least a portion of a length of the stator that is an outer envelope formed when the rotor shape undergoes planetary motion. In some of the second set of embodiments, the hypotrochoidal shape has n lobes, where n is an integer, the outer envelope shape has (n−1) lobes, the pitch of the rotor is the same as the pitch of the stator; and the ratio of the lead of the rotor to the lead of the stator is n:(n−1). In some such embodiments the hypotrochoidal shape is an ellipse, and n=2.
In at least some of a third set of embodiments, a rotary machine rotary machine comprises a stator and a rotor. The stator has a helical profile, a stator axis, and an epitrochoidal shape at any cross-section transverse to the stator axis, along at least a portion of a length of the stator. The rotor has a helical profile, a rotor axis, and a shape at any cross-section transverse to the rotor axis, along at least a portion of a length of the rotor, that is an inner envelope formed when the epitrochoidal shape of the stator undergoes planetary motion. The rotor is disposed within the stator and is configured to undergo planetary motion relative to the stator. In some of the third set of embodiments, the epitrochoidal shape of the stator has n−1 lobes, where n is an integer, the inner envelope shape of the rotor has n lobes, the pitch of the rotor is the same as the pitch of the stator, and the ratio of the lead of the rotor to the lead of the stator is n:(n−1). In some such embodiments n=2.
In at least some of a fourth set of embodiments, a rotary machine rotary machine comprises a stator and a rotor. The stator has a stator axis, a helical profile, and a stator shape that is outwardly offset from an epitrochoidal shape at any cross-section transverse to the stator axis, along at least a portion of a length of the stator. The rotor has a rotor axis, a helical profile, and a rotor shape at any cross-section transverse to the rotor axis, along at least a portion of a length of the rotor, that is an inner envelope formed when the stator shape undergoes planetary motion. The rotor is disposed within the stator and is configured to undergo planetary motion relative to the stator. In some of the fourth set of embodiments, the stator shape has n−1 lobes, where n is an integer, the rotor shape has n lobes, the pitch of the rotor is the same as the pitch of the stator, and the ratio of the lead of the rotor to the lead of the stator is n:(n−1). In some such embodiments n=2.
In some embodiments of rotary machines, such as the first, second, third and fourth sets of embodiments discussed above, the rotor is configured to spin about the rotor axis, the stator is configured to spin about the stator axis, and the rotor and stator are held at a fixed eccentricity with the rotor axis offset relative to the stator axis, so that during operation of said helical trochoidal rotary machine the rotor undergoes planetary motion relative to said stator without orbiting.
In some embodiments of rotary machines, such as the first, second, third and fourth sets of embodiments discussed above, the rotary machine is a multi-stage machine having a plurality of chambers between (and defined by) a fluid-facing surface of the rotor and a fluid-facing surface of the stator, and the fluid-facing surface of the rotor and/or the fluid-facing surface of the stator comprise one or more solids-handling features. In some embodiments, the rotary machines further comprise at least one seal mounted on the rotor and/or at least one seal mounted on the stator. In some embodiments, each of the plurality of chambers has approximately the same dimensions and shape. In some embodiments at least one of the plurality of chambers has dimensions that are different from another of the plurality of chambers.
In some embodiments, the solids-handling features comprise at least one groove formed in the fluid-facing surface of the rotor and/or in the fluid-facing surface of the stator. In some embodiments, the solids-handling features comprise a plurality of grooves formed in the fluid-facing surface of the rotor and/or in the fluid-facing surface of the stator. In some embodiments, the solids-handling features comprise at least one stitched groove formed in the fluid-facing surface of the rotor and/or in the fluid-facing surface of the stator. In some embodiments, the solids-handling features comprise a plurality of stitched grooves formed in the fluid-facing surface of the rotor and/or in the fluid-facing surface of the stator. In some embodiments, the solids-handling features comprise a plurality of indentations formed in the fluid-facing surface of the rotor and/or in the fluid-facing surface of the stator. In some embodiments, the solids-handling features are disposed asymmetrically on the fluid-facing surface of the rotor and/or on the fluid-facing surface of the stator.
In some embodiments of rotary machines, such as the first, second, third and fourth sets of embodiments discussed above, the rotary machine comprises at least one seal mounted on the rotor and/or the stator wherein each of the at least one seals has at least one of the following characteristics: the seal is mounted asymmetrically on the rotor or the stator; an outer surface of the seal is featured with indentations; an outer surface of the seal is featured with protrusions; the seal is configured to act as a scraper during operation of the rotary machine.
In some embodiments, the rotor has a double-start helical profile having a first rotor thread and a second rotor thread, the stator has a single-start helical profile, and the at least one seal comprises a first helical rotor seal mounted in a first groove extending along a path to one side of the crest of the first rotor thread of the helical rotor, and a second helical rotor seal mounted in a second groove extending along a path to one side of the second thread of the helical rotor. In some embodiments, the rotor has a double-start helical profile, and the stator has a single-start helical profile having a first stator thread, and the at least one seal comprises a helical stator seal mounted in a first groove extending along a path to one side of the first stator thread of the helical stator. In some embodiments, the at least one seal comprises at least one rotor seal mounted on the rotor. In some embodiments, the at least one seal comprises at least one stator seal mounted on the stator. In some embodiments, the at least one seal comprises at least one rotor seal mounted on the rotor and at least one stator seal mounted on the stator. In some embodiments, the rotary machine is a multi-stage machine having a plurality of chambers between (and defined by) cooperating surfaces of the rotor and the stator, and wherein each of the plurality of chambers has approximately the same dimensions and shape. In some embodiments, the rotary machine is a multi-stage machine having a plurality of chambers between (and defined by) cooperating surfaces of the rotor and the stator, and at least one of the plurality of chambers has dimensions that are different from another of the plurality of chambers.
The present disclosure relates to, among other things, rotary machines in which a helical rotor undergoes planetary motion relative to a stator. The rotary machines are based on trochoidal geometries, with the rotor or stator having a trochoidal geometry (in transverse cross-section, i.e. perpendicular to its axis). In some embodiments, the stator cavity can have an epitrochoidal cross-sectional geometry with the corresponding rotor cross-sectional profile being the inner envelope formed by the trochoid as it undergoes planetary motion (with the rotor having one more apex or lobe than the stator cavity). Much of the description below is focused on embodiments in which the rotor has a hypotrochoidal cross-sectional shape, with the corresponding stator cavity profile being the outer envelope of the rotor as it undergoes planetary motion (with the rotor having one more apex or lobe than the stator cavity). In at least some of these embodiments, one or more specific points on the envelope (whether it be the rotor or the stator) is in continuous contact with the corresponding component, and the contact point traces a trochoidal profile as the components execute their relative motions.
In some embodiments, the hypotrochoid and outer envelope (rotor and stator transverse cross-sectional profiles, respectively) are each swept along helical paths, the axes of those helices being the axes of rotation of those components in a reference frame in which both parts undergo simple rotary motion (the “centers” of those components). In some embodiments, the axes of the rotor and stator helices are offset from one another by a distance equal to the eccentricity of the rotor. In some embodiments, the helical rotor and corresponding stator have the same pitch, and the ratio of the lead of the rotor to the lead of the stator is the same as the ratio of their number of lobes (which is also the same as the ratio of their number of starts). As used herein, “pitch” is defined as the axial distance between adjacent threads (or crests or roots, for example, on a helix), and “lead” is defined as the axial distance or advance for one complete turn (360°). Pitch and lead are equal with single start helices; for multiple start helices the lead is the pitch multiplied by the number of starts.
In some embodiments of the rotary machines, the stator cross-sectional shape has n−1 lobes, where n is an integer greater than 1, the rotor shape has n lobes, the pitch of the rotor is the same as the pitch of the stator, and the ratio of the lead of the rotor to the lead of the stator is n:(n−1). In some embodiments, where n=2, the pitch of the rotor is the same as the pitch of the stator, and the ratio of the lead of the rotor to the lead of the stator is 2:1.
Thus, in some embodiments the outer surface of a helical rotor is defined by an ellipse swept along a helical path, and a corresponding stator cavity is defined by sweeping the corresponding outer envelope along a helical path with half the lead of the helical rotor. The rotor profile is a double-start helix, and the stator profile is a single-start helical cavity. For such a machine, when a transverse cross-section is taken in any plane perpendicular to the axis of rotation (of the rotor and/or stator), the outer profile of the rotor and inner profile of the stator (that is, the cross-sectional shape of the rotor and stator, respectively) is similar to those illustrated for those components in
In at least some embodiments, there is a quasi-helical contact path between the rotor and the inner “ridge” (or crest) of the stator at all times during rotation of the rotor relative to the stator. The contact path with the stator moves or oscillates back and forth across the helical “ridge” or crest of the rotor as the rotor rotates relative to the stator. The rotor-stator contact path revolves around the machine as pumping action proceeds, “threading” the fluid (or material to be pumped) in a spiral path along the helix, to that it is moved axially from one end of the stator cavity to the other.
The working principal of the rotary machines described herein is independent of which component of the machine is “fixed” and which is rotating. In some embodiments, for example, the machine can be operated such that the stator is fixed and the rotor spins and undergoes planetary motion (orbits) within it. This configuration is mechanically simple and compact, but sometimes requires counterweights to provide balance. In other embodiments, the outer stator undergoes planetary motion about the inner rotor.
Some embodiments of the rotary machines are operated such that the rotor spins but does not orbit. For example, in some embodiments the rotor spins but can be held at a specific eccentricity relative to the stator, and the stator can also be allowed to spin, so that the rotor and stator each revolve around their respective longitudinal axes. In such embodiments, even though the rotor and stator are each spinning (i.e. rotating) about their respective longitudinal axes, the relative motion of the components is basically the same as in corresponding fixed stator embodiments where the rotor spins and orbits within the stator.
In at least some embodiments, holding the rotor and stator at a fixed eccentricity and having these components spin about their longitudinal axes, rather than having one of them orbit, can significantly reduce problems with vibration and make the machine more balanced in operation.
With such rotary machine designs, one approach is to drive the rotor, for example by coupling it to a motor via a drive shaft, and allowing the rotation of the rotor to drive rotation of the stator. In other embodiments, the stator could be driven instead of the rotor. In another approach, the eccentricity is still fixed, but instead of the rotor driving the stator (or vice versa), a gear set is used, and both the rotor and the stator are driven via gears.
For downhole pump or artificial lift applications, a carrier (such as carrier 630 in
For downhole pump or artificial lift applications of rotary machines in which the stator is fixed and rotor is configured to spin and orbit within the stator, a drive-string is typically coupled to the rotor and drives the rotor to spin and orbit. For machines where the rotor has a helical profile and an elliptical shape (n=2), the rotor orbits at a radius equal to the eccentricity and it orbits twice as fast as it spins. Thus, with a fixed stator the drive-string also orbits at the same frequency and radius as the rotor. When the eccentricity is fixed and the rotor and stator each spin about their longitudinal axes, a drive-string used to drive the rotor (or stator) to spin would not need to orbit. This simplifies the drive-string design and operation, and can reduce the failures due to vibration in this region of the overall pump system.
For downhole pump, artificial lift and similar applications, there are a number of ways a system incorporating pumps of the type described herein could be deployed. For example, the pump can be top-driven where the motor is at the surface and is coupled to the rotor (or stator or gear system) via a drive-string (for example, as shown in
In some embodiments of the rotary machines the rotor and/or the stator are plastic. In some embodiments, the rotor and/or the stator can be metal. In some embodiments, depending on the application, the rotor and/or stator can be made from ceramic, elastomeric or other suitable materials or combinations of materials. The material(s) of the rotor can be the same as, or different from, the material(s) of the stator.
Ellipse 810 also rotates eccentrically within stator cavity 815, as if it is attached at its centre C to the head of radial arm 820 that rotates about a fixed end X. Circle 840 is the locus of the head of radial arm 820 as it rotates about fixed end X. Ellipse 810 rotates eccentrically at angular velocity ω2 in a counter-clockwise direction relative to a frame of reference in which fixed end X is stationary. The eccentricity, E, is the distance between centre C of ellipse 810 and X. Eccentricity E can be defined as the distance between the axis of rotation and the axis of symmetry. Radius R is the length “a” of the semi-major axis of ellipse 810 minus eccentricity E. Radius R is also equivalent to the average of the major and minor radii of the ellipse, i.e. (a+b)/2.
In some embodiments of rotary machines, the inverse apex (or ridge or crest) of the corresponding helical stator is always in contact with the outer surface of helical elliptical rotor during a complete revolution of elliptical rotor. This can be achieved by configuring geometric configuration 800 such that the difference between the semi-major axis of the rotor with elliptical cross-section (shown in
a−b=2E
In other words, in such embodiments: a=(R+E) and b=(R−E).
In variations of some of the helical trochoidal rotary machines described herein, the rotor and stator profiles can be offset along the normals of their planar transverse cross-sections. For example, in some such embodiments where the rotor is hypotrochoidal and undergoes planetary motion relative to a stator that is shaped as an outer envelope of that rotor, the rotor and stator can have cross-sectional profiles that are inwardly offset. For example,
In multi-stage embodiments of helical trochoidal rotary machines, if the rotor and stator pitch and all dimensions (including a, b and E, R and O as shown in
Referring again to
The distance between these points along the circular arc is the stator arc length (AS), and the shortest distance between these two points is the sweep width of the inverse apex region. On the rotor, contact with the inverse apex region 940 of the stator occurs between points 960 and 965. The distance between points 960 and 965 around the rotor crest is the rotor arc length (AR), and the shortest distance between these two points is the sweep width (WR) of the rotor.
For a helical rotor-stator assembly, contact between the rotor and stator occurs along curves that are the locus of contact points between the rotor and stator in each transverse “cross section”. For non-offset trochoid generating points in the envelope (i.e. the stator “inverse apex” of a hypotrochoid with outer envelope, or the “rotor tips” of an epitrochoid with inner envelope), this locus is a true helix. For offset trochoid generating points, the contact point moves across the arc length of the stator or rotor. This contact curve deviates from the true helix, but is visually substantially similar. The locus of contact points between trochoid and envelope is more complex; in most embodiments, it sweeps across a substantially longer arc, so the contact path is a distorted helix. It is then “interrupted” as the contact point crosses the trochoid generating point. The resulting contact curves are discrete segments, roughly helical in appearance, but not true helices. These have a different slope than the continuous curve of the trochoid generating contact, and “bridge” points on that contact to form closed chambers.
As can be seen, in embodiments such as the one illustrated in
The degree of offset can be selected to give desirable relative rotor and stator profiles. In particular, the degree of offset can be selected to achieve particular design objectives that can be advantageous both physically and also in relation to operation of the rotary machine.
A helical trochoidal pump can be characterized by three geometric factors: radius (R), eccentricity (E), and offset (O). In general terms, the radius and offset dictate the size of the pump, and the eccentricity dictates the cross-sectional shape (e.g. amount of elongation) of the elliptical (or offset elliptical) rotor. Another factor or parameter that can be used to characterize the machine geometry is the eccentricity ratio, as defined in equation (1). The effect of modifying these geometric factors is analyzed further below.
Solids handling capability relates to the capability of a rotary positive displacement machine, such as a pump, to be able transport fluids containing solids (e.g. hard particulates such as sand, fines, small rocks etc.) with a reduced tendency for jamming of the machine and/or with a reduced tendency for wear on one or more of the components of the machine. Various approaches can be used to improve the solids handling capability of the helical trochoidal rotary machines described herein.
One approach that can be used to improve the solids handling capability of the above-described rotary machines is to incorporate features on the fluid-facing surfaces of the rotor and/or stator that can accommodate, trap and/or transport solids. In some embodiments, the solids-handling features are indentations in the rotor or stator surface. Functionally, in some pump embodiments and end-use applications thereof, such features can act as a temporary trap for solids. The features can provide a place for solids to go, so they are not caught or squeezed between the contact surfaces when the stator slides by the rotor as a liquid containing the solids is pumped. The solids can exit the features and be entrained once again in the liquid as it moves along the fluid chambers created between the rotor and stator. In some embodiments and end-use applications, solids-handling features also cause additional turbulence in the flow of the fluid being pumped, and this can facilitate clearing of solids from the features so that they are entrained in the fluid as the fluid moves along the chambers and are discharged from the pump (along with the fluid) at the outlet. For example, using a grooved or “rifled” helical rotor or stator in helical trochoidal rotary pumps can allow solids to be accommodated in these grooves during operation of the pump, instead of being forced between the rotor and stator surfaces where they may cause wear of pump components and/or cause the machine to jam.
There is an array of options for solids-handling features that can be incorporated into a helical trochoidal rotary machine. For example, for various embodiments of helical trochoidal rotary machines with solids-handling features, selections can be made from each of the following categories:
Some examples of helical rotors and stators incorporating solids-handling features are described in reference to
Grooves or other solids-handling features on the rotor and/or stator can have various cross-sectional profiles. Some examples of different cross-sectional profiles for solids-handling features (shown on a helical rotor with an approximately elliptical cross-section) are shown in the cross-sectional views of
Solids-handling features, such as those described above, can be positioned along various paths on the rotor and/or stator. For example,
In some embodiments, grooves or other solids-handling features on the rotor can follow the demarcation path between the tip and flank of the rotor—in other words they can be positioned along the boundary between the rotor tip and flank. Equation (2) can be used to describe this demarcation path. In embodiments of the rotary machines, higher wear rates tend to occur in this region, so, at least in some embodiments, placing a groove or other solids handling feature(s) along this path can be advantageous.
Solids-handling features, such as those described above, can be positioned at various locations around the outer surface of a helical rotor or inner surface of a helical stator (e.g. relative to the rotor tip or stator inverse apex), and they can be positioned symmetrically or not. For example,
Some embodiments of the rotary machines operate with a small clearance between the helical rotor and stator, but without seals between them. In some embodiments it can be desirable to dispose a dynamic seal between these components to reduce leakage of fluid between stages. Sealing in helical trochoidal rotary machines is discussed in U.S. Pat. No. 10,844,859, which is incorporated by reference herein.
In some embodiments of helical trochoidal rotary machines, various rotor seal and/or stator seal configurations can be used to improve the solids handling capability of the machines. For example, the following can be considered in selecting a rotor seal configuration that can improve the solids handling capability of such rotary machines. Similar considerations can be applied to stator seals.
Positioning and Asymmetry: Dynamic seals can be positioned either on the leading tip/flank, or trailing tip/flank of the rotor.
Seal Range or Span: For example, in terms of seal width, a dynamic seal can start somewhere on the rotor tip and end somewhere in the flank. The seal range could include a portion, half, or most of the rotor tip.
Seal Face: The exposed seal surface can be shaped to match the rotor or stator profile, or the surface of the seal can have grooves, protrusions and/or other features to aid in solids handling or fines control. The seal surfaces can include other materials, such as bristles, hairs, broom-like features, and/or durable but flexible synthetic materials.
Function: The seal can be configured to serve more as a scraper, rather than being designed primarily to reduce fluid slip.
Seal cavity shape: The shape of the seal cavity that a dynamic seal sits within has implications on the reactive forces that the seal can exert on the pump contact surfaces. Depending on the mechanism chosen to provide reactive forces, the choice of seal cavity shape can have implications on the dynamic response of the pump. For example, in some embodiments it can be advantageous to use an asymmetric seal on the tip of the rotor and/or the stator inverse apex.
Solids collecting in the tail-end of the fluid chambers in some embodiments of helical trochoidal rotary machines can be a cause of abrasive wear. In some embodiments, this tail-end region is a long, tapered region with a high surface-area:volume ratio. Thus, this region can have a high negative impact on wear properties, with relatively little positive impact on volumetric flow. Thus, minimizing or at least reducing this region—or equivalently, maximizing or at least increasing the angular difference between the rotor and stator surface angles at contact locations—can, at least in some embodiments, be beneficial for improving solids handling performance.
This can be accomplished, for example, by selecting machine geometry parameters, including for example pump eccentricity (E) as well as (in at least some embodiments more importantly) pitch, so that the fluid chambers have dimensions and shape that are more conducive to handling solids with less tendency for wear. As pitch can have a significant impact on pump performance characteristics, a change in pitch will generally necessitate large changes in cross-sectional geometry, if particular pump characteristics are to be maintained. For example, decreasing pitch (which beneficially increases the angularity of the tail-ends of the fluid chambers) proportionally decreases the volumetric flow per revolution. A proportional increase in cross-sectional area can be used in order to achieve the same volumetric flow. This implies that a helical trochoidal rotary pump with superior solids handling, but equivalent theoretical flow rate, would generally tend to be radially larger. For some applications, it may not be possible to accommodate a pump with a larger radius. For example, for pumps that are required to be compatible with existing oil well assemblies, there may be limit to how far pitch can be adjusted before the pump exceeds the sizing constraints.
Changes to the eccentricity ratio, E/(R−O), of helical trochoidal rotary pumps also alter the shape of the rotor and stator—and therefore the shape of the fluid chambers and the rotor-stator contact angularity—for example, as described above in reference to
As described above in reference to
Pairing this orientation of such pumps with various intake geometries can aid in keeping solids, such as sand and fines, away from the contact surfaces and regions that tend to wear within the pump. For example, if the intake plumbing through which the fluid is drawn into the pump is a tornado shape that causes solids to migrate towards the outside and then enter into the horizontally oriented pump such that solids are mainly at the bottom, this can divert solids away from the sliding parts that otherwise tend to be subject to wear.
In some embodiments of helical trochoidal rotary pumps, the rotor and stator can be supported and geared such that the rotor and stator are held at a fixed position relative to one another, and optionally so that the input crank rotates both the rotor and stator. In some embodiments, the gap between the rotor and stator can be held constant. In some embodiments, the size of this gap can be selected such that it is larger than the solids contained in the fluid that the pump is intended to transport.
Much of the description herein has focused on embodiments of helical trochoidal rotary machines with a trochoidal rotor (and particularly on pumps with an elliptical or approximately elliptical rotor) and corresponding outer envelope stator cavity. In other embodiments, helical trochoidal rotary machines can have an epitrochoidal stator cavity profile and corresponding rotor (inner envelope) profile that are each swept along helical paths. These embodiments have the same relative motion of the rotor and stator (with the same orbit and spin) as machines with a trochoidal rotor and corresponding outer envelope stator cavity. The present approach can be applied to generate embodiments of helical rotary machines based on a hypotrochoidal or epitrochoidal rotor, where the components have more than two or three lobes.
In various embodiments, the rotor and/or optionally the stator can be rotated using any suitable drive mechanism.
Much of the description herein has focused on embodiments of helical trochoidal rotary machines in which the rotor and stator pitch and all dimensions (including a, b and E, R and O as shown in
In other multi-stage embodiments, the rotor-stator geometry can be varied, in a continuous or stepwise manner, along the axis of the rotary machine. In some embodiments, such variations can cause the volume of the fluid chambers to vary along the axis of the machine, such as may be desirable for compressor or expander applications, for example. In other embodiments, it can be advantageous to vary the geometry of the rotor-stator along the axis of the rotary machine, while keeping the volume of the fluid chambers formed between the helical rotor and the stator approximately the same along a length of the rotor-stator assembly. The various approaches to solids handling described above (e.g. use of rifling and/or other features on the rotor and/or stator, modified configuration of seals, and/or selection of machine geometry and/or orientation) can also be applied in helical trochoidal rotary machines in which the rotor-stator geometry varies along the axis of the rotary machine.
Similarly, the various approaches to solids handling described herein can be applied rotary machines that have similar trochoidal geometries, but where the rotor and stator are not helicized, such as for example rotary machines described in U.S. Pat. No. 10,087,758, which is incorporated by reference herein. In various embodiments of such machines, solids-handling features can be incorporated into the fluid-facing surface of the stator or rotor. For example,
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention can be practiced without these particulars. In other instances, well-known elements have not been shown or described in detail to avoid unnecessarily obscuring the description. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive sense.
Unless the context clearly requires otherwise, throughout the description and the claims:
Unless otherwise indicated, words that indicate directions such as “vertical”, “transverse”, “horizontal”, “upward”, “downward”, “forward”, “backward”, “inward”, “outward”, “vertical”, “transverse”, “left”, “right”, “front”, “back”, “top”, “bottom”, “below”, “above”, “under”, and the like, used in this description, depend on the specific orientation of the apparatus described and illustrated. The subject matter described herein can assume various orientations. Accordingly, these directional terms are not strictly defined and should not be interpreted narrowly.
Where a component is referred to above, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which perform the function of the described component.
Specific examples of systems, methods and apparatus have been described herein for purposes of illustration. These are only examples. The technology provided herein can be applied to systems other than the example systems described above. Many alterations, modifications, additions, omissions, and permutations are possible within the practice of this invention. This invention includes variations on described embodiments that would be apparent to the skilled addressee, including variations obtained by: replacing features, elements and/or acts with equivalent features, elements and/or acts; mixing and matching of features, elements and/or acts from different embodiments; combining features, elements and/or acts from embodiments as described herein with features, elements and/or acts of other technology; and/or omitting combining features, elements and/or acts from described embodiments.
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.
This application is related to and claims priority benefits from U.S. Provisional Patent Application Ser. No. 63/135,069 filed Jan. 8, 2021, entitled “Helical Trochoidal Rotary Machines with Improved Solids Handling”. The '069 application is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63135069 | Jan 2021 | US |
