Device for increasing flow rate in a fluid channel - Patents.com

Abstract

A fairing (302) in the form of a contoured restriction is submerged on the fluid channel surface (304 / 308) of the fluid channel (300) through which liquid flows, redistributing the velocity field and flow geometry upstream, and in some embodiments downstream, of discontinuities (110), thereby preventing flow separation (207), reducing the likelihood of cavitation, and increasing flow rate. Such discontinuities (110) include, but are not limited to, fittings such as L-fittings (100), T-fittings (1500), and Y-fittings, valve trims (1200), inlet regions to centrifugal pumps, and inlet regions to rotary valves, steps, constrictions, expansions, and ledges. The fairing (302) can be attached to the channel (300) or fabricated integrally with the channel (300).

Description

[Technical Field]

[0001] The present invention relates to fluid mechanics, and in particular to fairings for increasing the flow rate of fluid channels around fittings, valves, and other geometric discontinuities, for example to reduce or prevent cavitation. [Background technology]

[0002] Maximizing liquid flow rates through fluid management devices such as valves, pipes, instruments, pumps, etc. (collectively, fluid channels) is a long-standing industry challenge for designers. Limitations on flow rate are generally influenced by the physical properties and characteristics of the flowing fluid, such as static pressure, temperature, viscosity, surface tension, vapor pressure, presence of solids, and the geometry of the flow path, among other factors. Consideration of these factors leads to designs that reduce cavitation and pressure drop across components during operation at high flow rates.

[0003] Cavitation is a phenomenon in which pressure changes in a liquid lead to the formation of small vapor-filled cavities where the local pressure of the fluid is reduced below the liquid's vapor pressure. Later, when subjected to higher pressures, these cavities can collapse and generate shock waves. Collapsing cavities near metal or flow boundary surfaces cause cyclic stresses through repeated ruptures. This results in damage to the surface, in some cases substantial physical damage. Such pressure changes often occur near pipe bends and in other tortuous fluid channel paths where a sudden change in fluid flow direction occurs. Cavitation is a significant cause of component damage in several engineering contexts.

[0004] Extensive work in control valve design has resulted in several cavitation reduction devices and strategies, which in turn have led to guidance in the form of industry standards [1]. Currently available cavitation reduction devices and strategies include cage trim [2, 3], hardened trim materials to withstand the effects of cavitation [4], and generally increased overall size and volume of the transition region where cavitation and undesirable pressure drop occur. These devices and strategies often require specialized and expensive manufacturing techniques and / or contribute to increased costs due to the resulting increased size of the equipment.

[0005] Beyond applications in pipes, valves, instruments, and pumps, techniques for improving fluid flow have been employed in aviation for decades. For example, leading edge slats, Fowler flap designs, and vortex generators applied to specific locations on an airplane surface improve airflow characteristics. The dimpled surface of a golf ball provides another example of structural features configured to improve gas flow around an immersed object. In each of these examples, flow separation, i.e., the separation of fluid flowing away from the surface, is reduced, resulting in improved performance. Nevertheless, conventional liquid-carrying channels, such as pipes, fittings, and valves, are often damaged by cavitation. Thus, a need exists for devices for increasing the flow rate of fluid channels. Summary of the Invention [Means for solving the problem]

[0006] An embodiment of the present invention provides a device for increasing a flow rate of a fluid channel (300) in a downstream direction (310). The fluid channel has channel surfaces (304, 308). The channel surfaces are configured for liquid flow therealong. The channel surfaces include a discontinuity (110). The device includes a fairing (302). The fairing (302) defines respective fairing surfaces (312). The fairing surfaces are located entirely within the fluid channel. The fairing surfaces are configured for liquid flow therealong. The fairing surfaces extend from respective leading edges (400) of the fairing surfaces located upstream (306) of the discontinuity to respective trailing edges (402) of the fairing surfaces located downstream of the leading edges. The fairing surfaces extend at least as far as the discontinuity.

[0007] At the leading edge, the fairing surface is tangent to the channel surface. At the trailing edge, the fairing surface is tangent to the channel surface. The fairing surface follows a smooth transition curve between the leading and trailing edges.

[0008] Optionally, in any embodiment, the fairing surface follows a reverse curve that transitions smoothly between the leading and trailing edges.

[0009] Optionally, in any embodiment, the trailing edge of the fairing surface is not located further downstream than the discontinuity.

[0010] Optionally, in any embodiment, the trailing edge of the fairing surface is located downstream of the discontinuity.

[0011] Optionally, in any embodiment in which the trailing edge of the fairing surface is located downstream of the discontinuity, the fairing surface follows at least two cycles of the reverse curve.

[0012] Optionally, in any embodiment, the fluid channel defines a volume (109) configured for liquid flow therethrough, and at least a portion of the fairing surface between the leading edge and the trailing edge is displaced a positive distance, measured perpendicular to the downstream direction, into the volume of the fluid channel from an imaginary channel surface of the channel without the fairing.

[0013] Optionally, in any embodiment, the fluid channel defines a volume (109) configured for liquid flow therethrough, and at each location along the downstream direction, the fairing surface between the leading edge and the trailing edge is displaced a positive distance, measured perpendicular to the downstream direction, into the volume of the fluid channel from an imaginary channel surface of the channel without the fairing.

[0014] Optionally, in any embodiment, at each corresponding location along the downstream direction, the cross-sectional fluid flow area, measured perpendicular to the downstream direction of the fluid channel between the leading edge and the trailing edge and taking the fairing into account, is no greater than a hypothetical cross-sectional fluid flow area without the fairing.

[0015] Optionally, in any embodiment, the discontinuity is defined by a portion of a fluid channel that (a) has an L-shape, a T-shape, or a Y-shape, or (b) includes an inlet region to a centrifugal pump or rotary valve.

[0016] Optionally, in any embodiment, the fairing is configured for permanent or temporary installation in the fluid channel.

[0017] Optionally, in any embodiment, the fairing is formed as an integral part of the fluid channel.

[0018] Optionally, in any embodiment, the fairing surface is smooth.

[0019] Optionally, in any embodiment, the fairing surface is dimpled, roughened, or patterned.

[0020] Optionally, in any embodiment in which the fairing surface is recessed, roughened, or patterned, the fairing surface defines a surface pattern configured to cause the emission of an acoustic signal indicative of a predetermined flow characteristic of the fluid in response to a fluid flow therealong.

[0021] Optionally, in any embodiment, the fairing comprises a pin (900) about which the fairing is configured to pivot.

[0022] Optionally, in any embodiment, the fairing defines a hollow portion (1000) and an opening (1002) between the hollow portion (1000) and the fluid channel (300). The hollow portion (1000) and the opening (1002) are configured to emit an oscillating acoustic signal in response to fluid flow across the opening (1002).

[0023] Optionally, in any embodiment, the fairing defines a bladder (1102) in fluid communication with the control port (1106). The bladder is configured to change the shape of the surface (312) of the fairing 302 in response to inflation of the bladder (1102).

[0024] Optionally, in any embodiment in which the fairing defines a bladder, the fairing 312 defines at least one pressure sensing port (1108) fluidly coupled to a respective gauge port (1110).

[0025] Optionally, in any embodiment including a gauge port (1110), the gauge port (1110) is fluidly coupled to the control port (1106).

[0026] Optionally, in any embodiment, the fairing defines at least one passageway (1200-1202) through the fairing (302). Each passageway (1200-1202) fluidly connects a respective upstream portion to a respective downstream portion of the fairing (302). Each passageway (1200-1202) defines a respective upstream opening (1204-1206) and a respective downstream opening (1208-1210). Each passageway (1200-1202) is configured to allow at least a portion of the liquid flowing in the fluid channel (300) to bypass the complete contour of the fairing (302).

[0027] Optionally, in any embodiment, fairing (302) includes upstream portion (1300) and downstream portion (1302) joined together by pivoting hinge (1304). The upstream end of upstream portion (1300) is translationally attached to channel surface (304). The two portions (1300) and (1302) are configured to pivot in response to translation of the upstream end of upstream portion (1300), thereby extending pivoting hinge (1304), the downstream end of upstream portion (1300), and the upstream end of downstream portion (1302) further into fluid channel (300). Fairing (302) further includes spring (1318) configured to urge the upstream end of upstream portion (1300) toward a neutral position.

[0028] Optionally, in any embodiment, fairing (302) defines a first bladder (1402) and a second bladder (1404). The first bladder (1402) is in fluid communication with a port (1410) downstream of fairing (302) in fluid channel (300). The second bladder (1404) is in fluid communication with a port (1412) upstream of fairing (302) in fluid channel (300). The first and second bladders (1402-1404) are configured to automatically adjust the shape of fairing 302 based on the respective pressures at ports (1410-1412).

[0029] Optionally, in any embodiment, the channel surface includes a second discontinuity (1506). The device further includes a second fairing (1600). The second fairing (1600) defines a respective second fairing surface (1602). The second fairing surfaces are located entirely within the fluid channel. The second fairing surfaces are configured for liquid flow therealong. The second fairing surfaces extend from a leading edge (1604) of each of the second fairing surfaces (1606) located upstream of the discontinuity (1506) to a trailing edge (1608) of each of the second fairing surfaces located downstream of the leading edge. The second fairing surfaces extend at least as far as the discontinuity (1506).

[0030] At the leading edge (1604), the second fairing surface (1602) is tangent to the channel surface. At the trailing edge (1608), the second fairing surface (1602) is tangent to the channel surface. The second fairing surface (1602) follows a curve that smoothly transitions between the leading edge (1604) and the trailing edge (1608). The present invention further provides, for example, the following: (Item 1) 1. A device for increasing a flow rate of a fluid channel (300) in a downstream direction (310), the fluid channel having a channel surface (304, 308) configured for liquid flow therealong, the channel surface including a discontinuity (110), the device comprising: a fairing (302) defining a respective fairing surface (312), said fairing surface comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge (400) of each of the fairing surfaces located upstream (306) of the discontinuity to a trailing edge (402) of each of the fairing surfaces located downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; The fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge. (Item 2) Item 1. The device of item 1, wherein the fairing surface follows a reverse curve that transitions smoothly between the leading edge and the trailing edge. (Item 3) 3. The device of any of items 1-2, wherein the trailing edge of the fairing surface is not located further downstream than the discontinuity. (Item 4) 4. The device of any of items 1-3, wherein the trailing edge of the fairing surface is located downstream of the discontinuity. (Item 5) Item 5. The device of item 4, wherein the fairing surface follows a reversal curve of at least two cycles. (Item 6) 6. The device of any of items 1-5, wherein the fluid channel defines a volume (109) configured for liquid flow therethrough, and wherein at least a portion of the fairing surface between the leading edge and the trailing edge is displaced a positive distance, measured perpendicular to the downstream direction, into the volume of the fluid channel from an imaginary channel surface of the channel without the fairing. (Item 7) 7. The device of any of items 1-6, wherein the fluid channel defines a volume (109) configured for liquid flow therethrough, and at each location along the downstream direction, between the leading edge and the trailing edge, the fairing surface is displaced a positive distance, measured perpendicular to the downstream direction, into the volume of the fluid channel from an imaginary channel surface of the channel without the fairing. (Item 8) 8. The device of any of items 1-7, wherein at each corresponding location along the downstream direction, a cross-sectional fluid flow area, taking the fairing into account, measured perpendicular to the downstream direction of the fluid channel between the leading edge and the trailing edge is not greater than a hypothetical cross-sectional fluid flow area without the fairing. (Item 9) 9. The device of any of items 1-8, wherein the discontinuity is defined by a portion of the fluid channel that (a) has an L-shape, a T-shape, or a Y-shape, or (b) includes an inlet region to a centrifugal pump or a rotary valve. (Item 10) 10. The device of any of items 1-9, wherein the fairing is configured for permanent or temporary installation in the fluid channel. (Item 11) 11. The device of any of items 1-10, wherein the fairing is formed as an integral part of the fluid channel. (Item 12) 12. The device of any of items 1-11, wherein the fairing surface is smooth. (Item 13) 13. The device of any of items 1-12, wherein the fairing surface is dimpled, rough, or patterned. (Item 14) Item 14. The device of item 13, wherein the fairing surface defines a surface pattern configured to cause emission of an acoustic signal indicative of a predetermined flow characteristic of the fluid in response to a flow of fluid therealong. (Item 15) 15. The device of any of items 1-14, wherein the fairing comprises a pin (900), and the fairing is configured to pivot about the pin (900). (Item 16) A device described in any of items 1-15, wherein the fairing defines a hollow portion (1000) and an opening (1002) between the hollow portion (1000) and the fluid channel (300), and the hollow portion (1000) and the opening (1002) are configured to emit an oscillating acoustic signal in response to a fluid flow across the opening (1002). (Item 17) A device described in any of items 1-16, wherein the fairing defines a bladder (1102) in fluid communication with a control port (1106), and the fairing is configured to change the shape of a surface (312) of the fairing (302) in response to inflation of the bladder (1102). (Item 18) Item 18. The device of item 17, wherein the fairing (312) defines at least one pressure sensing port (1108) fluidly coupled to a respective gauge port (1110). (Item 19) Item 19. The device of item 18, wherein the gauge port (1110) is fluidly coupled to the control port (1106). (Item 20) A device described in any of items 1-19, wherein the fairing defines at least one passage (1200-1202) through the fairing (302), each passage (1200-1202) fluidly connecting a respective upstream portion to a respective downstream portion of the fairing (302), each passage (1200-1202) defining a respective upstream opening (1204-1206) and a respective downstream opening (1208-1210), each passage (1200-1202) configured to allow at least a portion of the liquid flowing within the fluid channel (300) to bypass the complete outer shape of the fairing (302). (Item 21) A device described in any of items 1-20, wherein the fairing (302) comprises an upstream portion (1300) and a downstream portion (1302) joined together by a pivoting hinge (1304), the upstream end of the upstream portion (1300) being attached to the channel surface (304) so ​​as to be able to move in translation, the two portions (1300) and (1302) being configured to pivot in response to translation of the upstream end of the upstream portion (1300), thereby extending the pivoting hinge (1304), the downstream end of the upstream portion (1300), and the upstream end of the downstream portion (1302) further into the fluid channel (300), and the fairing (302) further comprises a spring (1318) configured to urge the upstream end of the upstream portion (1300) toward a neutral position. (Item 22) The fairing (302) a first bladder (1402) in fluid communication with a port (1410) downstream of the fairing (302) in the fluid channel (300); a second bladder (1404) in fluid communication with a port (1412) upstream of the fairing (302) in the fluid channel (300); Define the 22. The device of any of items 1-21, wherein the first and second bladders (1402-1404) are configured to automatically adjust the shape of the fairing 302 based on the respective pressures at the ports (1410-1412). (Item 23) The channel surface includes a second discontinuity (1506), and the device comprises: a second fairing (1600) defining a respective second fairing surface (1602), said second fairing surface comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge (1604) of each of the second fairing surfaces (1606) located upstream of the discontinuity (1506) to a trailing edge (1608) of each of the second fairing surfaces located downstream of the leading edge, at least as far as the discontinuity (1506); At the leading edge (1604), the second fairing surface (1602) is tangent to the channel surface; At the trailing edge (1608), the second fairing surface (1602) is tangent to the channel surface; Item 23. The device of any of items 1-22, wherein the second fairing surface (1602) follows a curve that smoothly transitions between the leading edge (1604) and the trailing edge (1608). [Brief explanation of the drawings]

[0031] The present invention will be more fully understood by reference to the following detailed description of specific embodiments taken in conjunction with the drawings.

[0032] [Figure 1] FIG. 1 is a cross-sectional view of a fluid channel including a prior art 90° elbow and pipes leading into and out of the elbow.

[0033] [Figure 2] FIG. 2 is a cross-sectional view of the fluid channel of FIG. 1 including flow lines representing fluid flowing through the fluid channel according to the prior art.

[0034] [Figure 3] FIG. 3 is a cross-sectional view of a fluid channel according to one embodiment of the present invention, similar to the fluid channel of FIGS. 1 and 2, except with a fairing installed within the fluid channel.

[0035] [Figure 4] FIG. 4 is an enlarged view of the fairing of FIG. 3 including a portion of a fluid channel according to one embodiment of the present invention.

[0036] [Figure 5] FIG. 5 is a further enlarged view of the fairing of FIGS. 3 and 4 according to one embodiment of the present invention.

[0037] [Figure 6]FIG. 6 is a cross-sectional view of a fluid channel according to one embodiment of the present invention, similar to the fluid channel of FIGS. 3-5, except with a fairing installed within the fluid channel, in this case a variation of the fairing spanning the discontinuity.

[0038] [Figure 7] FIG. 7 is a cross-sectional view of the fluid channels and fairing of FIGS. 3-5 according to one embodiment of the present invention, illustrating the radii of curvature of the fairing surface at various locations between the leading and trailing edges of the fairing surface.

[0039] [Figure 8] FIG. 8 is a cross-sectional view of the fluid channel of FIGS. 1 and 2 according to the prior art, showing the radius of curvature of the surface of the channel without the fairing at locations corresponding to those in FIG.

[0040] [Figure 9] FIG. 9 is a cross-sectional view of a portion of the fluid channel of FIGS. 3-5, but with a fairing pivotally mounted about a pin, in accordance with one embodiment of the present invention.

[0041] [Figure 10] FIG. 10 is a cross-sectional view of a portion of the fluid channel of FIGS. 3-5, except with a fairing defining a hollow portion and an opening leading to the hollow portion, according to one embodiment of the present invention.

[0042] [Figure 11] FIG. 11 is a cross-sectional view of a portion of the fluid channels of FIGS. 3-5, except with a fairing including an inflatable bladder for changing the shape of the fairing and an optional pressure sensing port, according to one embodiment of the present invention.

[0043] [Figure 12]FIG. 12 is a cross-sectional view of a portion of the fluid channel of FIGS. 3-5, except with a fairing including one or more passages connecting respective upstream portions to respective downstream portions of the fairing, in accordance with one embodiment of the present invention.

[0044] [Figure 13] FIG. 13 is a cross-sectional view of a portion of the fluid channel of FIGS. 3-5, but with a fairing including two pivotally joined portions and a sliding bracket according to one embodiment of the present invention.

[0045] [Figure 14] FIG. 14 is a cross-sectional view of a portion of the fluid channels of FIGS. 3-5, except with a fairing including multiple bladders in fluid communication with respective ports in the fluid channels to automatically adjust the shape of the fairing based on the respective pressure at the ports in accordance with one embodiment of the present invention.

[0046] [Figure 15] FIG. 15 is a cross-sectional view of a fluid channel similar to that of FIG. 1, except for a T-junction including flow lines representing fluid flowing through the fluid channel according to the prior art.

[0047] [Figure 16] FIG. 16 is a cross-sectional view of the fluid channel of FIG. 15, but with a fairing installed within the fluid channel in accordance with an embodiment of the present invention.

[0048] [Figure 17] 17, 18, and 19 are top, side perspective, and side views, respectively, of an exemplary fairing according to an embodiment of the present invention. [Figure 18] 17, 18, and 19 are top, side perspective, and side views, respectively, of an exemplary fairing according to an embodiment of the present invention. [Figure 19] 17, 18, and 19 are top, side perspective, and side views, respectively, of an exemplary fairing according to an embodiment of the present invention.

[0049] [Figure 20] FIG. 20 is a graph characterizing pressure drop versus volumetric flow rate for an exemplary application of the fairing of FIGS. 17-19 in accordance with one embodiment of the present invention.

[0050] [Figure 21] FIG. 21 is a perspective view of a portion of a conventional multi-stage cavitation mitigation sphere and angle valve trim according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0051] Embodiments of the present invention introduce one or more fairings into the flow field of a fluid channel upstream and / or downstream of a geometric discontinuity that could otherwise lead to poor performance in the liquid flowing through the flow field. Such discontinuities include, but are not limited to, abrupt changes in direction (e.g., L, T, Y, valve trim, and the inlet or outlet regions of centrifugal pumps and rotary valves). While the flowing liquid may, but need not, have a free surface, the fairings are intended to be fully submerged in the liquid (at least when the fairing is performing its function). The presence of one or more fairings improves flow performance (facilitating higher flow rates for a given pressure drop, reducing flow separation, and / or reducing cavitation, etc.).

[0052] Through the use of hydrodynamically designed channel restrictions, fairings improve liquid flow characteristics where flow separation, cavitation, or other discontinuities would otherwise limit performance.

[0053] (definition) As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires.

[0054] A "fluid channel" is a passageway through which a liquid can flow. The term "liquid" includes slurries and liquids with suspended or entrained particles or gases. Examples of fluid channels include fittings (such as pipes, pumps, valves, and L-, T-, and Y-joints). A fluid channel encloses and supports a liquid flow perpendicular to the direction of fluid flow. A fluid channel defines a cross-sectional area and volume through which the liquid flows. Generally, the liquid contacts the inner surface of the fluid channel, but the liquid may define free surfaces that do not contact the inner surface of the fluid channel. For example, in a pipe that is only partially filled with liquid, the liquid contacts the inner surface of the pipe, typically the bottom surface, but the liquid also defines free surfaces that do not contact the inner surface of the pipe.

[0055] A "discontinuity" (also referred to herein as a "geometric discontinuity") is a geometric or other feature of a fluid channel that causes a change in the pressure of a fluid flowing through the fluid channel (other than pressure changes due to frictional losses experienced at the walls of the fluid channel). At a discontinuity, the flowing fluid streamlines are not tangent to the channel walls in the general direction of the flowing fluid. Often, a discontinuity is characterized by an abrupt change in the flow direction of the fluid moving through the channel relative to the overall length and / or direction of the fluid channel. Examples of discontinuities include, but are not limited to, L-joints, T-joints, Y-joints, steps, constrictions, expansions, ledges, valve trims, inlets to centrifugal pumps, and inlet and outlet regions to valves.

[0056] A "restriction" of a fluid channel is a region of the channel where the volume per unit length of the channel is reduced.

[0057] A "vena contracta" is a point in a fluid stream where the stream diameter is smallest and the fluid velocity is largest, such as in a stream exiting a nozzle. A vena contracta can occur at a flow restriction that occurs at a geometric discontinuity in a fluid channel. The flow streamlines cannot abruptly change direction at such a discontinuity, causing the streamlines to converge, resulting in flow thinning, flow separation, and ultimately, cavitation.

[0058] A "fairing" is a device that creates a contoured restriction in a fluid channel. The fairing can be a separate component from the channel that is attached to the inner surface of the channel, thereby forming the contoured restriction of the channel, or the fairing can be an integral geometric part of the channel, i.e., fabricated as a unit with the fluid channel.

[0059] A "reverse curve" (S-curve) is a curve to the left or right followed by a curve in the opposite direction.

[0060] "Resilient" means capable of being elastically deformed, absorbing energy, and recovering or springing back to shape upon removal of the load, releasing at least a portion of that energy.

[0061] A surface that is "concave along the direction of liquid flow" is one that expands outward along the path of liquid flow, as if the diameter of a pipe or tube were locally enlarged due to internal pressure.

[0062] A surface that is "convex along the direction of liquid flow" is one that causes the diameter of the pipe or tube to contract inward along the direction of liquid flow, as if locally squeezed due to external pressure. Thus, in an L-shape, as illustrated in Figure 1, the concave inner wall (e.g., at 101) has a larger radius than the radius of the convex inner wall (e.g., at 110). The fairing enlarges or otherwise modifies the convex surface.

[0063] An "integral" geometry or "integral" portion of a fluid channel describes a structure that is constructed as a part of the fluid channel. Such an integral geometry is distinguished from a structure that is formed separately from the fluid channel and then attached to the fluid channel.

[0064] (Fairing) As mentioned, embodiments of the present invention introduce one or more fairings into the flow field of a fluid channel upstream and / or downstream of a geometric discontinuity that may otherwise lead to poor performance in liquid flowing through the flow field. An upstream fairing is characterized in the direction of the flow streamlines by (a) a smooth transition from the inner surface of the fluid channel upstream of the discontinuity, and (b) a smooth transition to the inner surface at or downstream of the discontinuity.

[0065] The fairing may have a surface between the transition regions that is smooth, dimpled, roughened, or patterned with static geometric features. Such features may be required for assembly and installation to modulate (increase or decrease) turbulence levels, assist heat transfer, trap entrained solids or gases, or be designed to act as a Helmholtz resonator to emit an acoustic signal that can be measured to provide feedback on flow control.

[0066] The interior volume of the fairing need not be solid but may comprise a cavity or series of cavities. In some embodiments, the cavities within the fairing may be interconnected to one another, and / or to flow fields upstream and / or downstream of the fairing, and / or to fluid or gas reservoirs external to the fairing and flow field, and / or to instruments.

[0067] The cavities within the fairing may provide space for interconnection of the cavity with a fluid for temperature control and / or to house instruments for monitoring parameters related to fluid flow (such as liquid pressure, vapor pressure, viscosity, specific gravity, surface tension, temperature, and / or flow rate, etc.) The cavities within the fairing may also be connected to adjustable flaps that can be opened to direct the liquid moving through the cavity, thereby enabling improved performance across multiple fluid regimes.

[0068] The geometric characteristics of the fairing's surface may be selected according to parameters related to liquid flow, such as velocity, vapor pressure, viscosity, specific gravity, and surface tension. If a spline curve is used to describe the curvature of the fairing surface, the spline may be defined by a continuous polynomial of degree two or higher. However, the curvature of the fairing surface is not limited to a standard polynomial description, but may be represented by an ellipse, an involute, a catenary, an evolute, or any suitable mathematical or geometric representation, or portion thereof. Various functions, including polynomials, may be used to curve-fit the fairing to the expected flow profile.

[0069] The polynomial values ​​of the transition region of the fairing may be tailored to the desired flow rate and may vary in size and location based on the velocity, viscosity, vapor pressure, and / or other properties of the fluid.

[0070] Each fairing may have a single component or feature, or the fairing may be a composite of multiple components and / or features. The fairing or multiple fairings may span discontinuities and downstream regions.

[0071] (distinguishing from wings and conventional vehicle fairings) A fairing according to the present invention differs from a wing in at least the following respects: A wing is designed to reduce the radius of curvature of the flowing fluid and hold the flowing fluid closer to a pre-existing or desired geometric shape (sometimes a boundary) than the fluid would flow in the absence of the wing. In contrast, a fairing according to the present invention is configured to increase the radius of curvature of the flowing fluid and / or change the effective volume of the fluid channel at the point of discontinuity. A fairing can be viewed as changing the radius of curvature of the inner surface of the flow channel to more closely match the natural radius of curvature of the flowing fluid. Thus, a fairing is the opposite of a wing. While a wing is designed to modify the natural fluid flow path to conform to the geometric surface, a fairing modifies the geometric surface to more closely conform to the natural fluid flow path.

[0072] The wing does not touch an existing flow boundary, but rather is suspended within the flow when viewed in a plane perpendicular to the flow. The wing is therefore proximate, i.e., near but spaced from the flow boundary. In general, the fairing touches an existing flow boundary as described herein.

[0073] A wing does not redistribute the curvature of an existing flow boundary or redistribute the existing flow velocity profile. A fairing manipulates these characteristics.

[0074] The fairings described herein differ from conventional aircraft fairings, bicycle or motorcycle fairings, payload fairings, and cable fairings. An aircraft fairing is a structure that covers gaps or spaces between aircraft components to reduce form and interference drag and to improve appearance. A bicycle fairing is a full or partial covering for a bicycle to reduce aerodynamic drag or protect the rider from the elements. A motorcycle fairing is an outer shell placed over the frame of a motorcycle, particularly a racing or sport bike, whose primary purpose is to reduce aerodynamic drag. Secondary functions are to protect the rider from airborne hazards and wind-induced hypothermia, and to protect engine components in the event of an accident. Motorcycle fairings almost always include an integrated windshield. A payload fairing is a nose cone used to protect a spacecraft (launch vehicle payload) against dynamic pressure and aerodynamic heating during launch through the atmosphere. A cable fairing is a structure attached to a tow cable that is primarily designed to streamline the flow around the cable in a marine environment.

[0075] (Example problem) FIG. 1 is a cross-sectional view of a conventional 90° L-shaped fitting 100, with pipes 102 and 104 leading into and out of the L-shaped fitting 100. The L-shaped fitting 100 and pipes 102-104 collectively define a fluid channel 105. The general direction of fluid flow within the fluid channel 105 is indicated by axes 106 and 108. The fluid channel 105 defines a volume 109 through which liquid can flow. As can be seen in FIG. 1, the general direction of fluid flow changes abruptly at the L-shaped fitting 100, which, as discussed, can cause cavitation. The L-shaped fitting 100 introduces a discontinuity 110, exemplified here by a sharp corner. However, it should be noted that corner sharpness is relative. Even rounded corners can cause cavitation depending on the fluid flow characteristics, in conjunction with the corner geometry and / or dimensions. Thus, as used herein, the term "discontinuity" includes any location within a fluid channel where the direction of fluid flowing through the fluid channel suddenly changes and where, under anticipated operating conditions, that change in direction may cause cavitation (or otherwise adversely affect flow performance).

[0076] FIG. 2 is a cross-sectional view of the L-fitting 100 of FIG. 1 , excluding streamlines 200 representing fluid flowing through the L-fitting 100. Arrows 202 and 204 indicate the direction of fluid flow. Direction 202 abruptly changes to direction 204 at discontinuity 110. In the example shown in FIG. 2 , as a result of the abrupt change in direction, flow streamlines 200 are unable to follow the sharp edge of discontinuity 110, leading to a contraction 206, causing a pressure drop and flow separation 207 of streamlines 200 from the inner surface 208 of the fluid channel 105. At high flow velocities, the pressure drop and wall separation 207 can lead to cavitation and ultimately structural damage to the fluid channel 105.

[0077] Illustrative Embodiments FIG. 3 is a cross-sectional view of a fluid channel 300, similar to fluid channel 105 of FIGS. 1 and 2, according to an embodiment of the invention, except with a fairing 302 installed within the fluid channel 300. Arrows 306 and 310 indicate the upstream and downstream directions, respectively. As can be seen in FIG. 3, the fairing 302 provides a smooth transition from a portion of the fluid channel 300 upstream 306 of the discontinuity 110, e.g., the inner wall surface 304 of the pipe 102, to a portion of the fluid channel 300 downstream 310 of the discontinuity 110, e.g., the inner wall surface 308 of the pipe 104. The fairing 302 thus defines a transition region 311.

[0078] In contrast to the prior art, fairing 302 causes the fluid to flow smoothly and continuously follow fairing 302 surface 312 around transition regions and discontinuities 110, thereby increasing the fluid velocity at which flow separation from fluid channel surfaces 304 and / or 308 will occur and reducing cavitation for a given fluid velocity compared to the prior art. The improved flow behavior is evident from streamlines 314. For example, at 316, it can be seen that a locally higher velocity is maintained than in the prior art while wall contact is maintained.

[0079] 3 illustrates a device for increasing the flow rate of a fluid channel 300 in a downstream direction 310. The fluid channel 300 may be, for example, two pipes 102 and 104 joined by an L-shape 100, as discussed with reference to FIGS. 1 and 2 . The fluid channel 300 has a channel surface 304 / 308 configured so that fluid flows along the channel surface 304 / 308. The channel surface 304 / 308 may be an inner wall surface of the pipes 102 and 104, and a portion of the L-shape 100. The channel surface 304 / 308 includes a discontinuity 110, such as a sharp bend.

[0080] The device includes a first fairing 302. In normal use, the first fairing 302 should be fully submerged in the fluid flowing in the fluid channel 300. The first fairing 302 defines a respective fairing surface 312. The fairing surface 312 is located completely within the fluid channel 300. The fairing surface 312 is configured for fluid flow along the fairing surface 312.

[0081] Figure 4 is a close-up view of the fairing 302 of Figure 3, including a portion of the fluid channel 300. Figure 5 is a further close-up view of the fairing 302 alone. The fairing surfaces 312 extend from their respective leading edges 400, located upstream 306 of the discontinuity 110, to their respective trailing edges 402, located downstream 310 of the leading edges 400, at least as far as the discontinuity 110. Double arrow 404 (Figure 4) indicates the extent of the fairing surfaces 312.

[0082] The fairing 302 varies in thickness 406 over its length 408, where "thickness" refers to the dimension between the fairing surface 312 and the imaginary inner wall surface 304 of the fluid channel 300 without the fairing 302. Dimension 501 is an exemplary thickness of the fairing 302 at a point along the fairing surface 312. The fairing 302 tapers (i.e., becomes progressively thinner closer to) the leading edge 400, and ideally is as thin as possible given material, fabrication, and other practical constraints. In the embodiment shown in FIGS. 3-5 , the fairing surface 312 adjacent the leading edge 400 is convex and has a radius 408 ( FIG. 4 ).

[0083] In other embodiments, for example, as shown in the inset in FIG. 4 , the fairing surface 312 proximate the leading edge 400 may be in the form of a sloped, but straight, ramp 410 that forms a relatively small angle 412 with the channel surface 304. The angle 412 may be selected based on expected operating conditions and manufacturing practicalities. These factors may be traded off against one another. For example, the angle 412 may be selected to be thick enough to be economically manufactured, yet small enough to redirect the flowing fluid without significantly adversely affecting performance. Generally, the angle 412 is less than about 75°. In some embodiments, the angle 412 is less than about 60°, or less than about 40°, or less than about 30°, or less than about 25°, or less than about 7°.

[0084] In either case, i.e., curved, stepped, or straight, at the leading edge 400, the fairing surface 312 is referred to herein as being “tangent” to the channel surface 304. Tangent has its conventional mathematical and geometric meaning. However, as used herein, tangent also takes into account the practical aspects of manufacturing the fairing 302. The transition from the inner wall (channel surface) 304 to the fairing surface 312 should be smooth and continuous, to the extent practical. For example, because metals, plastics, and other practical materials cannot be made infinitely thin, if the fairing 302 is fabricated as a separate unit to be attached to the inner wall (channel surface) 304, the leading edge 400 may include a small but finite step 414, as shown in an enlarged view in FIG. 4 . Similarly, a straight leading edge 400 that meets the channel surface 304 at an angle 412 is considered to be tangent to the channel surface 304. All of the embodiments described herein are within the meaning of tangent. At the trailing edge 402, the fairing surface 312 is tangent to the channel surface 308, using the same definition of tangent as for the leading edge 400.

[0085] In some embodiments, for example, as shown in FIGS. 3-5 , the fairing surface 312 follows a reverse curve that smoothly transitions between the leading edge 400 and the trailing edge 402. For example, as best seen in FIG. 5 , in a first portion 500 of the fairing surface 312 proximate the leading edge 400, the fairing surface 312 follows a curve to the left 502 (when viewed in the downstream direction 310), and in a second portion 504, downstream of the first portion 500, the fairing surface 312 follows a curve to the right 506. The two portions 500 and 504 may be connected to each other by a straight portion 508, as shown in FIG. 5 . In this case, the curve reverses along or at the straight portion 508. Optionally, the two portions 500 and 504 may be connected to each other by a curved portion (not shown), or the two portions 500 and 504 may be directly connected to each other (not shown) and therefore tangent in the strict mathematical sense of the term.

[0086] In the embodiment shown in FIGS. 3-5 , the portion 500 (labeled in FIG. 5 ) of the fairing surface 312 proximate the leading edge 400 is concave to straight in the downstream direction 310. This portion 500 smoothly transitions from the channel surface 304 ( FIG. 4 ) upstream 306 of the discontinuity 110 to the trailing edge 402. The portion 504 ( FIG. 5 ) of the fairing surface 312 proximate the trailing edge 402 is convex to straight in the downstream direction 310. This portion 504 then transitions to the channel surface 308 proximate the discontinuity 110. As can be appreciated from FIG. 5 , the portion 500 of the fairing surface 312 proximate the leading edge 400 is configured to increase the radius of curvature of the flowing fluid, thereby directing the flowing fluid away from the channel surface 304. This results in an increase in the fluid velocity at which flow separation from the fairing surface 312 occurs and a reduction in cavitation for a given fluid velocity.

[0087] FIG. 6 is a cross-sectional view of a fluid channel 300 according to one embodiment of the invention, similar to the fluid channel of FIGS. 3-5 , except with a variation of a fairing (302) installed within the fluid channel 300. The trailing edge 402 of the fairing surface 312 described with respect to FIGS. 3-5 is not located farther downstream 310 than the discontinuity 110. However, in the variation of the fairing 302 shown in FIG. 6 , the trailing edge 402 of the fairing surface 312 is located downstream 310 of the discontinuity 110. In other words, the variation of the fairing 302 has been passed over the discontinuity 110. Among other attributes, the fairing of FIG. 6 promotes flow in either direction (310 or 306).

[0088] The fairing surface 312 of the modified fairing 302 shown in Figure 6 follows at least two cycles of the reverse curve, meaning that the curve reverses direction at least twice. The fairing surface 312 in Figure 6 reverses the curve direction (to the left) at or near point 600, and the fairing surface 312 reverses the curve again (this time to the right) at or near another point 602.

[0089] 7, fluid channel 300 defines volume 109 configured for liquid flow therethrough. At each location along downstream direction 310 of at least a portion of fairing surface 312 between leading edge 400 and trailing edge 402, as illustrated by the locations of arrows 700, 702, 704, and 706, fairing surface 312 is displaced into volume 109 of fluid channel 300 from an imaginary channel surface 708 of the channel without fairing 302 a positive distance, represented by the length of the arrow measured perpendicular to the downstream direction, i.e., the thickness of fairing 302. Thus, the fairing surface 312 follows a smoothly transitioning curve between the leading edge 400 and the trailing edge 402, and thus at least a portion of the fairing surface 312 between the leading edge 400 and the trailing edge 402, e.g., each of locations 700-706, is displaced a positive distance, measured perpendicular to the downstream direction 310, into the volume 109 of the fluid channel 300 from an imaginary channel surface 708 of the channel 300 without the fairing 302. As a result, fluid can flow without being closer to the imaginary channel surface 708 than the fairing surface 312.

[0090] FIG. 8 is a cross-sectional view of fluid channel 105, similar to fluid channel 300 of FIG. 7, except for the absence of fairing 302. As mentioned, fluid channel 105 defines an inner wall surface 808. Inner wall surface 808 coincides with imaginary channel surface 708 discussed with respect to FIG. 7. The locations of arrows 800-806 in FIG. 8 correspond to the locations of arrows 700-706 in FIG. 7. Of course, fluid channel 105 in FIG. 7 does not have a fairing. As a result, fluid can flow along inner wall surface 808. That is, fluid can flow closer to, and actually directly along, imaginary channel surface 808 in FIG. 8 than fluid can flow along imaginary channel surface 708 in FIG. 7.

[0091] 3, at multiple locations along the fairing surface 312, the fairing 302 causes fluid to flow a distance (e.g., distance 318) from the inner wall surface 304. Turning to FIG. 7, in some embodiments, at each corresponding location along the downstream direction 310, the fairing 302 between a point downstream of the leading edge 400, e.g., point 716 (FIG. 7), and a point upstream of the discontinuity, e.g., point 718, has a thickness 501 measured perpendicular to the downstream direction 310 that is greater than zero, which causes fluid to flow farther from the imaginary channel surface 708 than the fluid could flow from the inner wall surface 808 absent the fairing 302.

[0092] 6, at each corresponding location along the downstream direction 310, the fairing surface 312 between a point upstream of the discontinuity 110, e.g., point 604, and another point upstream of the trailing edge 402, e.g., point 606, has a thickness 608 measured perpendicular to the downstream direction 310 that is greater than zero, causing the fluid to flow farther from the imaginary channel surface 304 than it would from the inner wall surface 304 absent the fairing 302. Note that the downstream direction 310 changes (from horizontal to vertical in the example of FIG. 6) proximate the discontinuity 110.

[0093] Similarly, at each corresponding location along the downstream direction 310, the cross-sectional fluid flow area of ​​the fluid channel 300 (FIG. 3) measured perpendicular to the downstream direction 310 between the leading edge 400 and the trailing edge 402 and taking into account the fairing 302 is not greater than the hypothetical cross-sectional fluid flow area without the fairing 302 (FIG. 1 or 2).

[0094] The discontinuity 110 may be defined by a portion of the fluid channel 300 that has an L-shape, a T-shape, or a Y-shape. The discontinuity 110 may be defined by a portion of the fluid channel 300 that includes an inlet region to a centrifugal pump or a rotary valve.

[0095] The fairing 302 may be configured for permanent or temporary installation within the fluid channel 300. Alternatively, the fairing 302 may be formed as an integral part of the fluid channel 300.

[0096] The fairing surface 312 may be smooth, dimpled, rough, or patterned. The fairing surface 312 may define a surface pattern configured to trigger the emission of an acoustic signal in response to fluid flow along the fairing surface 312. The acoustic signal need not necessarily be audible to humans. The acoustic signal may be sonic, infrasonic, or ultrasonic. The acoustic signal may be indicative of a predetermined flow characteristic of the fluid, such as speed, velocity, pressure, or viscosity. For example, the frequency of the acoustic signal may be proportional to the speed of the fluid and / or the amplitude of the acoustic signal may be proportional to the amount of entrained solids in the fluid.

[0097] FIG. 9 is a cross-sectional view of a portion of a fluid channel 300, similar to the fluid channel 300 of FIGS. 3-5, except with variations regarding the fairing 302 mounted within the fluid channel 300, according to one embodiment of the present invention. In this embodiment, the fairing 302 is attached to a pin 900, about which the fairing 302 is configured to pivot. In a first version of this embodiment, the fairing 302 is configured to pivot only clockwise 902 from a neutral position. In a second version of this embodiment, the fairing 302 is configured to pivot only counterclockwise 904 from a neutral position. In a third version of this embodiment, the fairing 302 is configured to pivot both clockwise 902 and counterclockwise 904 from a neutral position. Optionally, any version of this embodiment includes a spring attached to the fairing 302 and configured to urge the fairing 302 toward the neutral position. In some cases, the spring is a torsion spring 906 wound around the pin 900.

[0098] In use, the fairing 302 automatically pivots about the pin 900 in response to the flow rate of the liquid flowing within the fluid channel 300. A high flow rate causes the fairing 302 to automatically pivot counterclockwise 904, thereby automatically conforming to the liquid flow streamlines and preventing the flow from separating from the channel surface 308, as discussed with respect to FIG.

[0099] FIG. 10 is a cross-sectional view of a portion of a fluid channel 300 according to one embodiment of the present invention, similar to the fluid channel of FIGS. 3-5 , except with another variation regarding the fairing 302 mounted within the fluid channel 300. In this embodiment, the fairing 302 defines a hollow portion 1000 and a neck and opening 1002 between the hollow portion 1000 and the fluid channel 300. The hollow portion 1000 and opening 1002 collectively form a Helmholtz resonator 1004. In response to fluid flowing across the mouth of the opening 1002, the Helmholtz resonator 1004 emits an oscillating acoustic signal that can be detected by an optional acoustic sensor 1006 and processed by an indicator circuit, a control circuit, a warning circuit, or other suitable circuitry (collectively shown at 1008). The acoustic sensor 1006 should be capable of sensing small differences in vibrations or pressure transmitted through the bounding wall of the fairing 302. The acoustic signal does not necessarily have to be audible to humans. The acoustic signal can be sonic, infrasonic, or ultrasonic. The dimensions and shape of hollow portion 1000 and / or opening 1002 can be selected to adjust Helmholtz resonator 1004 to emit an acoustic signal at a predetermined flow rate, for example, as a warning when the flow rate reaches or exceeds a safety value. Alternatively, the dimensions and shape of hollow portion 1000 and / or opening 1002 can be selected to resonate with the acoustic signal from cavitation, thereby amplifying the cavitation signal so that it can be detected by acoustic sensor 1006.

[0100] 11 is a cross-sectional view of a portion of a fluid channel 300, similar to the fluid channel 300 of FIGS. 3-5, except with yet another variation regarding the fairing 302 mounted within the fluid channel 300, in accordance with one embodiment of the present invention. In this embodiment, at least a portion 1100 of the fairing 302 is flexible, and in some cases resilient. The flexible portion 1100 forms a portion of a bladder 1102. The bladder 1102 defines a hollow portion 1104 in fluid communication with a control port 1106.

[0101] The bladder 1102 can be inflated or deflated by injecting or withdrawing fluid into or out of the hollow portion 1104 via a control port 1106. Inflating or deflating the bladder 1102 changes the shape of at least the flexible portion 1100 of the fairing 302, thereby changing the shape of the surface 312 of the fairing 302. The control port 1106 can be fluidly coupled to a drive mechanism, such as a piston (not shown), to change the shape of the fairing 302 under user or program control.

[0102] Optionally, or alternatively, the fairing 312 defines one or more pressure sensing ports, exemplified by pressure sensing port 1108, fluidly coupled to respective gauge ports, exemplified by gauge port 1110. The pressure sensing ports 1108 may be distributed longitudinally along the fairing 302 to measure respective pressures at various locations along the fairing 302. Each gauge port 1110 may be fluidly coupled to a pressure sensor or user-readable gauge (not shown), such as for monitoring pressure along the surface 312 of the fairing 302. Optionally, or alternatively, one or more of the gauge ports 1110 may be fluidly coupled to the control port 1106, such as directly or via a normalizing valve 1112, an amplifier 1114, or a piston 1116 (each of which is shown diagrammatically), to automatically inflate or deflate the bladder 1102 in response to pressure along the surface 312 of the fairing 302 or differences in pressure along the surface 312 of the fairing 302.

[0103] FIG. 12 is a cross-sectional view of a portion of a fluid channel 300 according to one embodiment of the invention, similar to the fluid channel of FIGS. 3-5 , except with yet another variation regarding the fairing 302 mounted within the fluid channel 300. In this embodiment, the fairing 302 defines one or more passages, represented by passages 1200 and 1202, therethrough. The passages 1200-1202 connect respective upstream portions to respective downstream portions of the fairing 302. Each passage 1200-1202 has a respective upstream opening, represented by upstream openings 1204 and 1206, and each passage 1200-1202 has a respective downstream opening, represented by downstream openings 1208 and 1210.

[0104] The passages 1200-1202 allow at least a portion of the liquid flowing in the fluid channel 300 to bypass the entire outer shape of the fairing 302. At relatively low flow rates, a significant portion or all of the liquid flowing in the fluid channel 300 can flow through the passage 1200, which is closest to the interior wall surface 304 of the pipe 102. As the flow rate increases, additional portions of the liquid flowing in the fluid channel 300 flow through additional passages 1200-1202, which are progressively farther from the interior wall surface 304 of the pipe 102. For example, at higher flow rates, a portion of the liquid flowing in the fluid channel 300 can flow through the passage 1200, and an additional portion of the liquid flowing in the fluid channel 300 flows through the passage 1202, which is next-closest to the interior wall surface 304 of the pipe 102. Thus, the fairing 302 automatically adapts to various flow rates without any moving parts.

[0105] FIG. 13 is a cross-sectional view of a portion of a fluid channel 300, similar to the fluid channel of FIGS. 3-5, according to one embodiment of the invention, except with another variation regarding the fairing 302 mounted within the fluid channel 300. In this embodiment, the fairing 302 includes an upstream portion 1300 and a downstream portion 1302 joined end to end by a pivoting hinge 1304. The downstream end of the downstream portion 1302 is attached to the inner wall surface 304 of the pipe 102 via a fixed bracket 1308 by a second pivoting hinge 1306. The upstream end of the upstream portion 1300 is attached to the inner wall surface 304 of the pipe 102 via a pivoting portion 1310 and a sliding bracket 1312. The sliding bracket 1312 is translatable longitudinally, parallel to the direction of flow, as indicated by a double arrow 1314.

[0106] As the sliding bracket 1312 translates toward the fixed bracket 1308, the two portions 1300 and 1302 of the fairing 302 pivot, as indicated by the arrows. As a result, the pivoting hinge 1304, and the downstream end of portion 1300, and the upstream end of portion 1302 extend further into the flow stream of the fluid channel 300, as indicated by the dashed line 1316, thereby reducing the radius of the flow stream. Translating the sliding bracket 1312 away from the fixed bracket 1308 at least partially withdraws the pivoting hinge 1304, the downstream end of portion 1300, and the upstream end of portion 1302 from the flow stream of the fluid channel 300, as indicated by the solid line. A spring 1318 urges the sliding bracket 1312 toward a neutral or initial position.

[0107] Liquid flowing within the fluid channel 300 pushes the sliding bracket 1312 and one portion 1300 of the fairing 302 toward the fixed bracket 1308, compressing the spring 1318 and making the curve of the fairing 302 more aggressive. If the liquid flow rate decreases, the spring returns the sliding bracket 1312 and the portion 1300 of the fairing 302 toward their neutral or initial position. Thus, the fairing of FIG. 13 can be used as a flow rate regulator.

[0108] Mounting the spring 1318 on a cam (not shown) gives the spring a non-linear spring constant. With a hysteresis spring constant, the fairing 302 can be used as a safety device or to limit the flow rate through the fluid channel 300. Application of such an embodiment involves presetting the hysteresis spring constant to a value that allows a flow rate up to a predetermined value, but the fluid channel and fairing 302 can, at least theoretically, sustain a higher flow rate. The predetermined flow rate can be selected to protect other equipment or piping, or the predetermined flow rate can be set to a higher flow rate and the hysteresis spring constant can then be adjusted to allow the increased flow rate.

[0109] FIG. 14 is a cross-sectional view of a portion of a fluid channel 300 according to one embodiment of the present invention, similar to the fluid channel of FIGS. 3-5 , except with yet another variation regarding the fairing 302 mounted within the fluid channel 300. In this embodiment, at least a portion 1400 of the fairing 302 is flexible, and in some cases resilient. The flexible portion 1400 forms part of multiple bladders, represented by bladders 1402 and 1404. Each bladder 1402-1404 defines a respective hollow portion, represented by hollow portions 1406 and 1408. The hollow portions 1406-1408 are in fluid communication with respective ports, represented by ports 1410 and 1412, downstream and upstream of the fairing 302 within the fluid channel 300 via respective channels, represented by channels 1414 and 1416, to automatically adjust the shape of the fairing 302 based on the respective pressures at the ports 1410-1412.

[0110] Optionally, hollow portions 1406 and 1408 are communicatively coupled to one another, such as via a one-way valve 1418, to standardize the pressure within hollow portions 1406-1408, such as when the pressure in one of hollow portions 1408 exceeds a predetermined value.

[0111] (Fairing at the confluence of fluid flows) The fairing 302 in Figures 3-7 and 9-14 is described in the context of an L-shape. However, the principles of the fairing 302 also apply to other types of pipes, such as T-shaped fittings, Y-shaped fittings, and other fittings with multiple input ports where multiple fluid streams are joined together, such as to produce a single outlet. Figure 15 is a cross-sectional view of a T-shaped fitting 1500 with two input ports 1502 and 1504. Like Figure 2, Figure 15 includes streamlines 200 to represent the fluid flowing through the T-shaped fitting 1500. The line pattern of the streamlines 200 represents example flow velocities, as shown in the legend in Figure 15. The flow velocities shown in Figures 15 and 16 are meant to be representative in nature and are described based on analytical modeling of flow behavior in hypothetical examples. Flow velocities in other examples may be higher, lower, or extend over a range different from those shown in Figures 15 and 16.

[0112] Arrows 202 and 204 indicate the direction of fluid flow. As a result of the two abrupt changes in direction, flow streamlines 200 are unable to follow the sharp edges of discontinuities 110 and 1506, leading to a contraction 206, resulting in a pressure drop and flow separation 207 of streamlines 200 from the inner surface 208 of the fluid channel.

[0113] The problem illustrated in Figure 15 can occur in many contexts, including in rotary and three-way valves, overflow channels, and discharge or release headers. Sharp corners in the entry and exit areas of headers, valves, etc., and slots in rotary valves are discontinuous, and the resulting sudden change in direction of liquid flow can lead to contractions, resulting in pressure drops and flow separation from the inner surfaces, as discussed with respect to Figures 1, 2, and 15. In high liquid velocity flows, the pressure drop and wall separation can lead to cavitation and ultimately structural damage.

[0114] 16 is a cross-sectional view of fluid channel 300, similar to the fluid channel of FIG. 15, except with two fairings 302 and 1600 installed within fluid channel 300 (one fairing 302 and 1600 per input port 1502 and 1504). As discussed with reference to FIGS. 3-5, fairings 302 and 1600 provide a smooth transition from the respective portions of fluid channel 300 upstream of discontinuities 110 and 1506 to the respective portions of fluid channel 300 downstream of discontinuities 110 and 1506. Fairings 302 and 1600 thus define respective transition regions.

[0115] The second fairing surface 1602 extends from a leading edge 1604 of the second fairing surface 1602 located upstream 1606 of the discontinuity 1506 to a trailing edge 1608 of the second fairing surface 1602 located downstream of the leading edge 1604, at least as far as the discontinuity 1506.

[0116] The fairings 302 and 1600 cause the fluid to flow smoothly and continuously follow the surfaces 312 and 1602 of the fairings 302 and 1600 around the transition regions and discontinuities 110 and 1506, thereby increasing the fluid velocity at which flow separation from the surfaces of the fluid 300 channel will occur and reducing cavitation for a given fluid velocity compared to the prior art. The improved flow behavior is evident from the streamlines 1610.

[0117] (Fairing shape) 17, 18, and 19 are a top view, a side perspective view, and a side view, respectively, of an exemplary fairing 1700 according to an embodiment of the present invention. As can be seen in FIG. 17, the longitudinal axis 1702 of the fairing 1700 is curved, although in other embodiments, the longitudinal axis is straight. Concave areas 1704 and 1706 on portions of a surface 1708 of the fairing 1700 are also visible in FIG.

[0118] Analytical characterization of flow rate versus pressure drop indicates that when hydrocarbons are pumped at high volumetric flow rates at the confluence of fluid flow applications using the fairings of Figures 17-19, a 50% reduction in pressure drop for a given flow rate can be equated to approximately 25% more volumetric flow for the same pumping energy (pressure drop) required. A typical characterization of this performance is shown in Figure 20.

[0119] (Fairing in control valve cage trim assembly) With the proliferation of 3D printing technology, fairings, as described herein, can be fabricated into control valve cage trim assemblies and other components with corresponding improvements in fluid performance. Current cage trim designs are considered limited to flowpath geometries manufactured using traditional methods and include a feature set that includes drilled holes, wire-cut square-profile channels, and features that can be milled from outside the trim's cylinder. However, fairings according to the present disclosure can be incorporated into valve trim with a one-piece design, such as via additive manufacturing methods.

[0120] Conventional cavitation mitigation designs can be improved with the addition of fairings as described herein. For example, a portion of a conventional multi-stage cavitation mitigation sphere and angle valve trim 1200 is shown in FIG. 21 (a diagram attributed to Flowserve Corporation). Fairings (not shown) can be fabricated or installed at sharp changes in direction within the valve trim 2100.

[0121] (References) [1]SA-RP75.23-1995-Recommended Practice-Considerations for Evaluating Control Valve Cavitation, Instrument Society of America, 1995, Research Triangle Park, North Carolina.

[0122] [2] Monsen, J., “Liquid Flow in Control Valves,” Valin® blog, 1 / 30 / 2017, https: / / www.valin.com / resources / blog / liquid-flow-control-valves-choked-flow-cavitation-and-flashing.

[0123] [3] Roth, KW, Stares, JA, “Avoid Control Valve Application Problems with Physics-based Models,” Hydrocarbon Processing, August 2001.

[0124] [4] Stares, J., “Control Valve Cavitation, Damage Control,” Dresser-Masoneilan publication, February 2007.

[0125] Although the present invention is described through the exemplary embodiments set forth above, modifications to and variations of the illustrated embodiments may be made without departing from the inventive concepts disclosed herein. For example, although specific parameter values, such as angles, may be recited in connection with the disclosed embodiments, within the scope of the present invention, the values ​​of all parameters may vary over a wide range to suit different applications. Unless otherwise indicated in the context or understood by one of ordinary skill in the art, terms such as "about" mean within ±20%.

[0126] As used herein, including in the claims, the term "and / or" when used in connection with a list of items means one or more of the items in the list, i.e., at least one of the items in the list, but not necessarily every item in the list. As used herein, including in the claims, the term "or" when used in connection with a list of items means one or more of the items in the list, i.e., at least one of the items in the list, but not necessarily every item in the list. "Or" does not mean "exclusive or."

[0127] The disclosed aspects, or portions thereof, may be combined in ways not listed above and / or not explicitly claimed. In addition, the embodiments disclosed herein may be suitably implemented in the absence of any element not specifically disclosed herein. Thus, the present invention should not be considered as limited to the disclosed embodiments.

[0128] As used herein, numerical terms such as "first," "second," and "third" are used to distinguish respective fairings from one another and are not necessarily intended to indicate any particular order or total number of fairings in any particular embodiment. Thus, for example, a given embodiment may include only a second fairing and a third fairing.

Claims

1. 1. A method of increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the method comprising: and disposing a fairing adjacent the discontinuity, the fairing defining a respective fairing surface free of ridges perpendicular to the downstream direction, the fairing surface comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; The fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge.

2. The method of claim 1 , wherein the fairing surface follows a reverse curve that smoothly transitions between the leading edge and the trailing edge.

3. The method of claim 1 , wherein the trailing edge of the fairing surface is located no further downstream than the discontinuity.

4. The method of claim 1 , wherein the trailing edge of the fairing surface is located downstream of the discontinuity.

5. The method of claim 3 , wherein the fairing surface follows at least two cycles of a countercurve.

6. 2. The method of claim 1, wherein the fluid channel defines a volume configured for liquid flow therethrough, and wherein positioning the fairing comprises positioning the fairing such that at least a portion of the fairing surface between the leading edge and the trailing edge is displaced into the volume of the fluid channel a positive distance measured perpendicular to the downstream direction from an imaginary channel surface of the channel without the fairing.

7. 2. The method of claim 1, wherein the fluid channel defines a volume configured for liquid flow therethrough, and wherein positioning the fairing includes positioning the fairing such that at each location along the downstream direction, between the leading edge and the trailing edge, the fairing surface is displaced into the volume of the fluid channel a positive distance, measured perpendicular to the downstream direction, from an imaginary channel surface of the channel without the fairing.

8. The method of claim 1, wherein positioning the fairing includes positioning the fairing such that at each corresponding location along the downstream direction, between the leading edge and the trailing edge, the cross-sectional fluid flow area measured perpendicular to the downstream direction of the fluid channel, taking the fairing into account, is not greater than a hypothetical cross-sectional fluid flow area without the fairing.

9. 10. The method of claim 1, wherein the discontinuity is defined by a portion of the fluid channel that (a) has an L-shape, a T-shape, or a Y-shape, or (b) includes an inlet region to a centrifugal pump or a rotary valve.

10. The method of claim 1 , wherein positioning the fairing adjacent the discontinuity comprises temporarily installing the fairing within the fluid channel.

11. The method of claim 1 , wherein disposing the fairing adjacent the discontinuity comprises forming the fairing as an integral part of the fluid channel.

12. The method of claim 1 , wherein the fairing surface is smooth.

13. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; The fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge, and the fairing surface is dimpled, roughened, or patterned.

14. 14. The device of claim 13, wherein the fairing surface defines a surface pattern configured to cause emission of an acoustic signal indicative of a predetermined flow characteristic of the fluid in response to a flow of liquid therealong.

15. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; the fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge; The device, wherein the fairing comprises a pin, the fairing configured to pivot about the pin.

16. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; the fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge; the fairing defines a hollow portion and an opening between the hollow portion and the fluid channel, the hollow portion and the opening configured to emit an oscillating acoustic signal in response to fluid flow across the opening.

17. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; the fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge; The device, wherein the fairing defines a bladder in fluid communication with a control port, the fairing configured to change the shape of a surface of the fairing in response to inflation of the bladder.

18. The device of claim 17 , wherein the fairing defines at least one pressure sensing port fluidly coupled to a respective gauge port.

19. The device of claim 18 , wherein the gauge port is fluidly coupled to the control port.

20. 2. The method of claim 1, wherein the fairing defines at least one passage therethrough, each passage fluidly connecting a respective upstream portion to a respective downstream portion of the fairing, each passage defining a respective upstream opening and a respective downstream opening, each passage configured to allow at least a portion of liquid flowing in the fluid channel to bypass the complete contour of the fairing.

21. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; the fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge; the fairing comprises an upstream portion and a downstream portion joined together by a pivoting hinge, an upstream end of the upstream portion being translatably attached to the channel surface, the two portions being configured to pivot in response to translation of the upstream end of the upstream portion, thereby extending the pivoting hinge, the downstream end of the upstream portion, and the upstream end of the downstream portion further into the fluid channel, the fairing further comprising a spring configured to urge the upstream end of the upstream portion toward a neutral position.

22. A device for increasing a flow rate of a fluid channel in a downstream direction, the fluid channel having a channel surface configured for liquid flow therealong, the channel surface including a discontinuity, the device comprising: a fairing defining a respective fairing surface, said fairing surfaces comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the fairing surfaces upstream of the discontinuity to a trailing edge of each of the fairing surfaces downstream of the leading edge at least as far as the discontinuity; At the leading edge, the fairing surface is tangent to the channel surface; at the trailing edge, the fairing surface is tangent to the channel surface; the fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge; The fairing is a first bladder in fluid communication with a port in the fluid channel downstream of the fairing; a second bladder in fluid communication with a port in the fluid channel upstream of the fairing; Define the The device, wherein the first and second bladders are configured to automatically adjust the shape of the fairing based on the respective pressures at the ports.

23. The channel surface includes a second discontinuity, and the method further comprises: and disposing a second fairing defining a respective second fairing surface, the second fairing surface comprising: located entirely within the fluid channel; configured for liquid flow therealong; extending from a leading edge of each of the second fairing surfaces upstream of the discontinuity to a trailing edge of each of the second fairing surfaces downstream of the leading edge at least as far as the discontinuity; at the leading edge, the second fairing surface is tangent to the channel surface; at the trailing edge, the second fairing surface is tangent to the channel surface; The method of claim 1 , wherein the second fairing surface follows a curve that smoothly transitions between the leading edge and the trailing edge.

24. The method of claim 1, wherein the fairing surface is recessed, rough, or patterned.

25. The method of claim 24, wherein the fairing surface defines a surface pattern configured to cause the emission of an acoustic signal indicative of predetermined flow characteristics of the fluid in response to a flow of fluid therealong.

26. The method of claim 1, wherein the fairing comprises a pin and the fairing is configured to pivot around the pin.

27. ​​The method of claim 1, wherein the fairing defines a hollow portion and an opening between the hollow portion and the fluid channel, the hollow portion and the opening being configured to emit an oscillating acoustic signal in response to fluid flow across the opening.

28. The method of claim 1, wherein the fairing defines a bladder in fluid communication with a control port, and the fairing is configured to change the shape of a surface of the fairing in response to inflation of the bladder.

29. The method of claim 28, wherein the fairing defines at least one pressure sensing port fluidly coupled to a respective gauge port.

30. The method of claim 29, wherein the gauge port is fluidly coupled to the control port.

31. The method of claim 1, wherein the fairing comprises an upstream portion and a downstream portion joined together by a pivoting hinge, the upstream end of the upstream portion being attached to the channel surface so as to be movable parallel to the channel surface, the two portions being configured to pivot in response to parallel movement of the upstream end of the upstream portion, thereby extending the pivoting hinge, the downstream end of the upstream portion, and the upstream end of the downstream portion further into the fluid channel, and the fairing further comprises a spring configured to urge the upstream end of the upstream portion into a neutral position.

32. The fairing is a first bladder in fluid communication with a port in the fluid channel downstream of the fairing; a second bladder in fluid communication with a port in the fluid channel upstream of the fairing; Define the 10. The method of claim 1, wherein the first and second bladders are configured to automatically adjust the shape of the fairing based on the respective pressures at the ports.

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