CORIOLIS FLOW METER WITH FLOW TUBE INCLUDING INSERTS

Abstract

A Coriolis flow meter (100) comprises a driver (180) coupled to a flow tube (800,900), the driver (180) configured to oscillate the flow tube in a drive direction, a pick-off sensor (170L, 170R) coupled to the flow tube (800,900), configured to measure a movement of the flow tube (800,900), and the flow tube (800,900) comprises a conduit (852) having an interior surface (854), and a plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b), each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) being coupled to at least a first position (858) on the interior surface (854) of the conduit (852).

Claims

1. A Coriolis flow meter (100) comprising: a driver (180) coupled to a flow tube (800, 900), the driver (180) configured to oscillate the flow tube (800, 900) in a drive direction; a pick-off sensor (170L, 170R) coupled to the flow tube (800,900), configured to measure a movement of the flow tube (800,900); and the flow tube (800,900) comprising: a conduit (852) having an interior surface (854); and a plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b), each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) being coupled to at least a first position (858) on the interior surface (854) of the conduit (852).

2. The Coriolis flow meter (100) as claimed in claim 1, wherein the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) are shaped as rods.

3. The Coriolis flow meter (100) as claimed in claim 1, wherein the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) are shaped as fins.

4. The Coriolis flow meter (100) as claimed in claim 1, wherein the first position (858) of at least one of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) is within an active portion of the conduit (852).

5. The Coriolis flow meter (100) as claimed in claim 1, wherein the first position (858) on the interior surface (854) of the conduit (852) is within a bend (802a, 802b) of the conduit (852).

6. The Coriolis flow meter (100) as claimed in claim 1, wherein each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) extends across at least 25 percent of a diameter of the conduit (852).

7. The Coriolis flow meter (100) as claimed in claim 1, wherein each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) includes a first end coupled to the first position (858) and a second end that is coupled to at least a second position on the interior surface (854) of the conduit (852).

8. The Coriolis flow meter (100) as claimed in claim 1, wherein a diameter of the conduit (852) is at least 2 inches.

9. The Coriolis flow meter (100) as claimed in claim 1, wherein the plurality of inserts (956a, 956b) includes a first insert (956a) having a first longitudinal extent (902a) and a second insert (956b) having a second longitudinal extent (902b), the first longitudinal extent (902a) being offset 45 degrees or more from the second longitudinal extent (902b).

10. A method of assembling a Coriolis flow meter (100), the method comprising: providing a flow tube (800,900); coupling a driver (180) to the flow tube (800,900), the driver (180) configured to oscillate the flow tube (800,900) in a drive direction; and coupling a pick-off sensor (170L, 170R) coupled to the flow tube (800,900), the pick-off sensor (170L, 170R) configured to measure a movement of the flow tube (800,900), wherein the flow tube (800,900) comprises a conduit (852) having an interior surface (854), and a plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b), each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) being coupled to at least a first position (858) on the interior surface (854) of the conduit (852).

11. A method as claimed in claim 10, wherein the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) are shaped as rods.

12. A method as claimed in claim 10, wherein the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) are shaped as fins.

13. A method as claimed in claim 10, wherein the first position (858) on the interior surface (854) of the conduit (852) is within an active portion of the conduit (852).

14. A method as claimed in claim 10, wherein the first position (858) on the interior surface (854) of the conduit (852) is within a bend (802a, 802b) of the conduit (852).

15. A method as claimed in claim 10, wherein each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) extends across at least 25 percent of a diameter of the conduit (852).

16. A method as claimed in claim 10, wherein each respective insert of the plurality of inserts (856a, 856b, 856c, 856d, 956a, 956b) includes a first end coupled to the first position (858) and a second end that is coupled to at least a second position on the interior surface (854) of the conduit (852).

17. A method as claimed in claim 10, wherein a diameter of the conduit (852) is at least 2 inches.

18. The method as claimed in claim 10, wherein the plurality of inserts (956a, 956b) includes a first insert (956a) having a first longitudinal extent (902a) and a second insert (956b) having a second longitudinal extent (902b), the first longitudinal extent (902a) being offset 45 degrees or more from the second longitudinal extent (902b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

[0031] FIG. 1 depicts a flow meter 100, in accordance with an embodiment;

[0032] FIG. 2 depicts moving flow tubes 200, in accordance with an embodiment;

[0033] FIG. 3A depicts a moving flow tube 300, in accordance with an embodiment;

[0034] FIG. 3B depicts a plot 350, in accordance with an embodiment;

[0035] FIG. 4A depicts moving flow tubes 400, in accordance with an embodiment;

[0036] FIG. 4B depicts a plot 450, in accordance with an embodiment;

[0037] FIG. 5A depicts fluid flow 500, in accordance with an embodiment;

[0038] FIG. 5B depicts fluid flow 550, in accordance with an embodiment;

[0039] FIG. 6 depicts plot 600, in accordance with an embodiment;

[0040] FIG. 7A depicts fluid flow 700, in accordance with an embodiment;

[0041] FIG. 7B depicts fluid flow 720, in accordance with an embodiment;

[0042] FIG. 7C depicts fluid flow 740, in accordance with an embodiment;

[0043] FIG. 7D depicts fluid flow 760, in accordance with an embodiment;

[0044] FIG. 8A depicts a flow tube 800, in accordance with an embodiment;

[0045] FIG. 8B depicts a detail 850 of flow tube 800, in accordance with an embodiment;

[0046] FIG. 9 depicts flow tube 900, in accordance with an embodiment; and

[0047] FIG. 10 depicts method 1000, in accordance with an embodiment.

DETAILED DESCRIPTION

[0048] FIGS. 2-10 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the Application. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the Application. Those skilled in the art will appreciate that the features described below may be combined in various ways to form multiple variations of the Application. As a result, the Application is not limited to the specific examples described below, but only by the claims and their equivalents.

[0049] FIG. 2 depicts moving flow tubes 200. Moving flow tubes 200, which comprise flow tubes 130, 130′ of flow meter 100, oscillate in the first out-of-phase bend mode (drive mode) with no fluid flow in the Figure. As may be seen in FIG. 1, pick-off sensors 170R, 170L are coupled to flow tubes 130, 130′ on either side of driver 180 to measure the displacement of flow tubes 130, 130′ as they vibrate. Under no flow conditions, such as those depicted in FIG. 2, pick-off sensors 170R, 170L provide symmetric, in phase signals. After fluid flow begins through the vibrating tubes, however, a Coriolis force is induced on the tubes.

[0050] The equation for the Coriolis force is as follows:

{right arrow over (F)}=−2m{right arrow over (ω)}×{right arrow over (V)},  (Equation 1)

where {right arrow over (F)} is the Coriolis force, m is the mass, {right arrow over (ω)} is the angular rotation, and {right arrow over (V)} is the velocity of the fluid. The Coriolis force with fluid flow in the out-of-phase bend mode may be seen in moving flow tube 300 of FIG. 3A. Two example force vector diagrams including angular momentum {right arrow over (ω)}, the velocity {right arrow over (V)}, and the Coriolis force {right arrow over (F)} are overlaid over moving flow tube 300 on FIG. 3A on either side of driver 180.

[0051] The Coriolis force distribution along moving flow tube 300 during the out-of-phase bend mode is depicted in plot 350 of FIG. 3B. In plot 350, the X-axis is the distance along the axis of flow tube 130 and the Y-axis is the Coriolis force. Overlaid on plot 350 are the example locations of pick-off sensors 170L, 170R and driver 180. It may be seen that the Coriolis force vector {right arrow over (F)} points in opposite directions on either side of the driver.

[0052] FIG. 4A depicts moving flow tubes 400. Moving flow tubes 400 comprise two flow tubes 130, 130′ in out-of-phase bending mode with fluid flow. FIG. 4B depicts plot 450 comprising the phases detected at pick-off sensors 170L and 170R during fluid flow. As may be seen in plot 450, the phase difference between the motion detected at pick-off sensors 170L and 170R is phase offset Δφ. Phase offset Δφ is directly proportional to mass flow rate {dot over (m)} of the fluid under test:

{dot over (m)}∝FCF×Δφ,  (Equation 2)

and FCF (grams per second/microsecond) is the meter flow calibration factor. The flow calibration factor FCF is often determined by the manufacturer under test conditions.

[0053] Turbulent and laminar flow is determined by the Reynolds number

[00001]$\begin{array}{cc}Re=\frac{\rho \mathrm{VD}}{\mu },& \left(\mathrm{Equation}3\right)\end{array}$

where, ρ is density, V is velocity, D is diameter, and μ is viscosity. A fluid is approximately laminar when the Reynolds number Re is below 2000, and turbulent when it is above 4000. When the Reynolds number Re is between 2000 and 4000, the fluid is in a transition zone between turbulent and laminar.

[0054] Equation 1 assumes that the fluid velocity {right arrow over (V)} term is uniform throughout the tube. However, the assumption of uniform fluid velocity {right arrow over (V)} only applies to fluids in the turbulent flow regime. Fluids in the laminar flow regime have velocities that vary across the flow tube diameter.

[0055] For example, FIGS. 5A and 5B depict fluid flow 500 and fluid flow 550 respectively. Fluid flows 500 and 550 depict velocity {right arrow over (V)} profiles (length of horizontal arrows) across the diameter of flow tube 130 (oriented vertically) for turbulent and laminar fluid flows, respectively. The flows in FIGS. 5A and 5B represent fluids with the same mass m and angular rotation {right arrow over (ω)}. As may be seen in FIGS. 5A and 5B, the velocity vectors α1 and α2 positioned along the central axes of the flow tube have the same magnitude under laminar flow and turbulent flow. Therefore, along the central axis of a flow tube, fluids under laminar and turbulent flows produce approximately the same effective Coriolis force {right arrow over (F)}.

[0056] Along the boundaries of fluid flows 500 and 550, however, velocity vector β1 is depicted for laminar flow, and velocity vector β2 is depicted for turbulent flow. For turbulent flow, velocity vectors β2 and α2 are approximately the same. However, for laminar flow, inner velocity vector α1 is greater than outer velocity vector β1. Because turbulent flow velocity vector β2 is greater than laminar flow vector β1, a fluid under laminar flow will therefore produce less effective Coriolis force {right arrow over (F)} for a fluid under turbulent flow. Therefore, the mass flow {dot over (m)} determined for fluid flow 550, the fluid under laminar flow conditions, may be less than the mass flow {dot over (m)} determined for fluid flow 500, the fluid under turbulent flow conditions.

[0057] FIG. 6 depicts plot 600, which demonstrates the low flow error effect. Plot 600 includes a Y-axis comprising a volume error percentage, and an X-axis comprising a Reynolds number. In plot 600, it may be seen that fluids with Reynolds numbers below 100,000 include an increasing amount of negative volume error, which may be attributed to undermeasurement due to laminar flow.

[0058] FIGS. 7A, 7B, 7C, and 7D depict fluid flows 720, 740, 760, and 780, respectively, around an obstacle 702. As may be seen, the fluid, which enters FIGS. 7A to 7D from the left in laminar flow, exits the Figures to the right after diverting around obstacle 702. In FIG. 7A, the fluid has a Reynolds number Re that is less than 1, and the fluid resumes laminar flow after passing obstacle 702. In FIG. 7B, the fluid has a Reynolds number Re that is between 1 and 30, which produces a little bit of vortex activity before resuming laminar flow after passing obstacle 702. In FIG. 7C, the fluid has a Reynolds number Re that is between 30 and 1000, and the fluid produces more vortexes to form a von Karman vortex trail after passing obstacle 702. In FIG. 7D, the fluid has a Reynolds number Re that is greater than 1000, and the fluid becomes turbulent for some distance along the flow tube after passing obstacle 702.

[0059] In an embodiment of the application, a flow tube with inserts is used to generate turbulence in the fluid to reduce the volume error for fluids with Reynolds numbers below 100,000, similar to obstacle 702 in FIG. 7D. For example, FIG. 8A depicts a cutaway view of flow tube 800, and FIG. 8B depicts a detail of a flow tube 800 for a Coriolis flow meter 100 in accordance with an embodiment. As described above, Coriolis flow meter 100 comprises a driver 180 coupled to a flow tube, for example flow tube 700, the driver 180 configured to oscillate the flow tube 800 in a drive direction. The Coriolis flow meter 100 further comprises a pick-off sensor 170L, 170R coupled to the flow tube 800, configured to measure a movement of the flow tube 800.

[0060] It should be appreciated that while the Coriolis flow meter 100 described above comprises a dual flow conduit flow meter, it is well within the scope of the present invention to implement a single, or any other multiple conduit flow meter. Furthermore, while the flow conduits 130, 130′ are shown as comprising a curved flow conduit configuration, the present invention may be implemented with a flow meter comprising one or more straight flow conduits. Therefore, the particular embodiment of the Coriolis flow meter 100 described above is merely one example and should in no way limit the scope of the present invention.

[0061] Flow tube 800 includes a conduit 852 having an interior surface 854. In embodiments, the conduit 852 may have a circular cross section, an oval cross section, or any other cross section known to those of skill. In the example of flow tube 800, with the conduit 852 including a circular cross section, the interior surface 854 is a cylindrical surface with four bends.

[0062] Flow tube 800 further comprises a plurality of inserts, each respective insert of the plurality of inserts being coupled to at least a first position on the interior surface of the conduit. For example, FIG. 8B depicts plurality of inserts 856a, 856b, 856c, 856d, and FIG. 8A depicts further plurality of inserts along other sections of flow tube 800. Each respective insert of the plurality of inserts 856a, 856b, 856c, 856d is coupled to a respective position, for example first position 858 for insert 856a, on the interior surface 854 of the conduit 852.

[0063] By placing the plurality of inserts 856a, 856b, 856c, 856d along an interior surface 854 of the flow tube 800, it may be possible to provide turbulent flow within the Coriolis flow meter 100, thereby reducing the errors generated when a fluid under measurement exhibits laminar flow.

[0064] The example of flow tube 800 is not intended to be limiting. As those of skill in the art will readily understand, flow tube 800 may include any number of inserts 856a, 856b, 856c, 856d to increase turbulent flow.

[0065] In embodiments, the first position 858 of at least one of the plurality of inserts 856a, 856b, 856c, 856d may be positioned in an active portion of the flow tube 800. For example, at least one of the plurality of inserts 856a, 856b, 856c, 856d may be positioned in a portion of flow tube 800 that is driven to oscillate by driver 180, such as the portion of flow tube 800 between brace bars 140 and 140′ in FIG. 1.

[0066] By providing inserts 856a, 856b, 856c, 856d in the active portions of flow tube 800, it may be possible to provide turbulent flow where the Coriolis forces are the strongest, and where the pick-off sensors 170L, 170R tend to be positioned. This may minimize the errors generated due to undermeasurement of fluids under laminar flow for Coriolis flow meter 100.

[0067] In embodiments, the first position 858 of at least one of the plurality of inserts 856a, 856b, 856c, 856d is within a bend of the conduit. For example, at least one of the plurality of inserts 856a, 856b, 856c, 856d may be positioned in a portion of bend 802a or 802b, which may be seen in FIGS. 8A and 8B, respectively.

[0068] By providing inserts 856a, 856b, 856c, 856d within a bend portion 802a, 802b of flow tube 800, it may be possible to produce turbulent flow where it may provide the greatest area of turbulent flow in a fluid under test. This may further help minimize the errors generated due to undermeasurement of fluids under laminar flow for Coriolis flow meter 100.

[0069] In embodiments, each respective insert of the plurality of inserts 856a, 856b, 856c, 856d may extend across at least 25 percent of a diameter of the conduit 852. By providing inserts 856a, 856b, 856c, 856d that do not connect to two separate portions of the interior surface 854, it may be possible to maximize turbulent flow without causing alignment problems that may result if an insert is connected at two separate portions to interior surface 854 during manufacturing flow tube 800.

[0070] As those of skill will readily understand, however, each respective insert of the plurality of inserts 856a, 856b, 856c, 856d may span any portion of the diameter of the conduit 852. In embodiments, for example, the plurality of inserts 856a, 856b, 856c, 856d may extend across at least 30, 50, 70, or 100 percent of a diameter of the conduit 852.

[0071] In further embodiments, however, one or more inserts of the plurality of inserts 856a, 856b, 856c, 856d may include a first end coupled to the first position and a second end that is coupled to at least a second position on the interior surface of the conduit. In examples, any insert of the plurality of inserts 856a, 856b, 856c, 856d may be positioned to pass through the central axis of flow tube 800. In further examples, however, any insert of the plurality of inserts 856a, 856b, 856c, 856d may be positioned across a cross-section of the flow tube without passing through the central axis of flow tube 800.

[0072] In embodiments, the plurality of inserts 856a, 856b, 856c, 856d may be shaped as rods. For example, plurality of inserts 856a, 856b, 856c, 856d may comprise long, thin members with circular cross sections.

[0073] In further embodiments, the plurality of inserts 856a, 856b, 856c, 856d may be shaped as fins. In examples, the fins may comprise substantially planar inserts with a longitudinal direction extending along the axis of the flow tube.

[0074] In further embodiments, other shapes or orientations of inserts 856a, 856b, 856c, 856d that provide turbulent flow in the fluid under test, and/or allow for low-cost manufacturing may be possible, as will be understood by those of skill.

[0075] In embodiments, a diameter of flow tube 800 conduit 852 may be at least 2 inches. This may provide for improved meter accuracy in larger meters, which are more likely to experience laminar flow causing undermeasurement of fluids under test.

[0076] In embodiments, the plurality of inserts 856a, 856b, 856c, 856d may include a first insert having a first longitudinal extent and a second insert having a second longitudinal extent, the first longitudinal extent being offset 45 degrees or more from the second longitudinal extent. For example, FIG. 9 depicts a cross-sectional view of flow tube 900, in accordance with an embodiment. In FIG. 9, it may be seen that first insert 956a has a first longitudinal extent 902a and second insert 956b has a second longitudinal extent 902b. In embodiments, first insert 956a and second insert 956b may be positioned along the same or different locations along the longitudinal length of flow tube 900. First longitudinal extent 902a is oriented to be offset 45 degrees or more from second longitudinal extent 902b.

[0077] By orienting one or more inserts of the plurality of inserts 956a, 956b in different directions, it may be possible to improve the ability for flow tube 900 to create turbulent flow of fluids under test.

[0078] FIG. 10 depicts method 1000, in accordance with an embodiment. Method 1000 may be executed to assemble a Coriolis flow meter in accordance with an embodiment.

[0079] Method 1000 begins with step 1002. In step 1002, a flow tube is provided. For example, flow tube 800 comprising conduit 852 having an interior surface 854, and plurality of inserts 856a, 856b, 856c, 856d, each respective insert of the plurality of inserts 856a, 856b, 856c, 856d being coupled to at least a first position 858 on interior surface 854 of the conduit 852 may be provided, as described above.

[0080] In embodiments, flow tube 800 may be formed by drilling, machining, wire electrical discharge machining, one or more holes through conduit 852. Each respective insert of the plurality of inserts 856a, 856b, 856c, 856d may then be inserted into a respective hole of the plurality of holes, and welded, brazed, or otherwise coupled to the conduit 852, thereby sealing the flow tube 800 from fluid leaks.

[0081] In further embodiments, flow tube 800 may be fabricated via injection molding.

[0082] Method 1000 continues with step 1004. In step 1004 a driver is coupled to the flow tube, the driver configured to oscillate the flow tube in a drive direction. For example, driver 180 may be coupled to flow tube 800 to oscillate flow tube 800 in the drive direction, as described above, using any coupling technique known to those of skill.

[0083] Method 1000 continues with step 1006. In step 1006 a pick-off sensor is coupled to the flow tube, the pick-off sensor configured to measure a movement of the flow tube.

[0084] For example, pick-off sensor 170L, 170R may be coupled to flow tube 800 to measure the movement of flow tube 800 using any coupling technique known to those of skill.

[0085] Method 1000 may allow for the assembly of a Coriolis flow meter that lacks the undermeasurement problems found in flow meters with fluids under test that have Reynolds numbers Re below 100000, and therefore tend to exhibit laminar flow.

[0086] In embodiments of method 1000, the plurality of inserts may be shaped as rods, as described above.

[0087] In embodiments of method 1000, the plurality of inserts may be shaped as fins, as described above.

[0088] In embodiments of method 1000, the first position of at least one of the plurality of inserts may be positioned in an active portion of the conduit, as described above.

[0089] In embodiments of method 1000, the first position of at least one of the plurality of inserts may be positioned within a bend of the conduit, as described above.

[0090] In embodiments, each respective insert of the plurality of inserts may extend across at least 25 percent of a diameter of the conduit, as described above.

[0091] In embodiments, each respective insert of the plurality of inserts may include a first end coupled to the first position and a second end coupled to at least a second position on the interior surface of the conduit, as described above.

[0092] In embodiments, a diameter of the conduit may be at least 2 inches, as described above.

[0093] In embodiments, the plurality of inserts 956a, 956b may include a first insert 956a having a first longitudinal extent 902a and a second insert 956b having a second longitudinal extent 902b, the first longitudinal extent 902a being offset 45 degrees or more from the second longitudinal extent 902b.

[0094] Thus, although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. Accordingly, the scope of the embodiments described above should be determined from the following claims.