Flow Sensor, Method and Flowmeter for Determining Speeds of Phases of a Multi-Phase Medium

Abstract

A flow sensor for a multi-phase medium flowmeter has a sensor carrier, and the sensor carrier has at least one first sensor array. The at least one first sensor array has a first permittivity sensor for determining a first permittivity of a multi-phase medium, a second permittivity sensor for determining a second permittivity of the medium, a density sensor for determining a density of the medium, and a first sensor axis. The first permittivity sensor, the second permittivity sensor, and the density sensor are arranged on the sensor carrier along the first sensor axis, and the first permittivity sensor and the second permittivity sensor are spaced apart with a permittivity sensor distance.

Claims

1. A flow sensor for a flowmeter, wherein the flowmeter is designed for determining speeds of phases of a multi-phase medium, the flow sensor comprising: a sensor carrier having at least one first sensor array; the at least one first sensor array has a first permittivity sensor for determining a first permittivity of a multi-phase medium, a second permittivity sensor for determining a second permittivity of the medium, a density sensor for determining a density of the medium, and a first sensor axis; the first permittivity sensor, the second permittivity sensor, and the density sensor are arranged on the sensor carrier along the first sensor axis; and the first permittivity sensor and the second permittivity sensor are spaced apart with a permittivity sensor distance.

2. A flow sensor according to claim 1, wherein respective sensitive areas of the first permittivity sensor, the second permittivity sensor, and the density sensor are smaller than smallest flow structures of the medium.

3. A flow sensor according to claim 1, wherein the density sensor is arranged between the first permittivity sensor and the second permittivity sensor.

4. A flow sensor according to claim 1, wherein the sensor carrier is a printed circuit board.

5. A flow sensor according to claim 4, wherein at least the first permittivity sensor a capacitance sensor.

6. A flow sensor according to claim 5, wherein the capacitance sensor has a first electrode and a second electrode for determining a capacitance of the medium.

7. A flow sensor according to claim 6, wherein at least the first electrode is a trace of the printed circuit board.

8. A flow sensor according to claim 7, wherein at least the trace is passivated by amorphous carbon.

9. A flow sensor according to claim 1, wherein the density sensor is a piezo sensor.

10. A flow sensor according to claim 9, wherein the piezo sensor is a film bulk acoustic wave resonator.

11. A flow sensor according to claim 1, wherein the density sensor is a capacitive micromechanical ultrasound transducer.

12. A flow sensor according to claim 1, wherein the sensor carrier has a recess and the density sensor is arranged in the recess.

13. A flow sensor according to claim 1, wherein at least one of the first permittivity sensor, the second permittivity sensor, and the density sensor is a microsensor.

14. A flow sensor according to claim 1, wherein the sensor carrier has a second sensor array with a second sensor axis and the first sensor axis and the second sensor axis differ from one another.

15. A method for determining speeds of phases of a multi-phase medium, comprising: immersing a flow sensor according to claim 1 into a flowing multi-phase medium; determining a first permittivity curve with the first permittivity sensor, determining a second permittivity curve with the second permittivity sensor, and determining a density curve of the medium with the density sensor; and determining at least one speed of a phase of the medium from the first permittivity curve, the second permittivity curve, and the density curve using a correlation method.

16. The method according to claim 15, wherein the correlation method includes the following steps: detecting a permittivity change in the first permittivity curve, the permittivity change being detected in the second permittivity curve; determining a permittivity change interval between the permittivity change in the first permittivity curve and in the second permittivity curve, determining a speed of the one permittivity change using the permittivity change interval and the permittivity sensor distance; and assigning the speed of the permittivity change to a speed of a phase of the medium using the density curve and/or the first permittivity curve and/or the second permittivity curve.

17. A flowmeter for determining speeds of phases of a multi-phase medium in a measuring tube, the flowmeter comprising: a sensor control; a measuring tube; and at least one first flow sensor; the at least one first flow sensor is designed according to claim 1; the sensor control is designed for carrying out a method according to claim 15; and the at least one first flow sensor is arranged at a first measuring position on the measuring tube so that when a multi-phase medium flows through the measuring tube, the medium flows around the flow sensor, the flow sensor has a first immersion depth in the medium, and the first sensor axis has a component parallel to a direction of flow of the medium.

18. A flowmeter according to claim 17, wherein the measuring tube is designed so that the at least first flow sensor can be inserted and removed during operation.

19. A flowmeter according to claim 17, wherein the sensor control has at least one resonant circuit having a resonance frequency, the first permittivity sensor is a part of the resonant circuit, and the first permittivity of the medium is determined using the resonance frequency.

20. A flowmeter according to claim 17, wherein the flowmeter has a second flow sensor at a second measuring position having a second immersion depth, and the second measuring position differs from the first measuring position and/or the second immersion depth differs from the first immersion depth.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 illustrates a first embodiment of a flowmeter having two flow sensors.

[0049] FIG. 2a and FIG. 2b illustrate a first embodiment of a flow sensor.

[0050] FIG. 3 illustrates a second embodiment of a flow sensor.

[0051] FIG. 4 illustrates a second embodiment of a flowmeter having one flow sensor.

[0052] FIGS. 5a-5c plot measuring signals of the flow sensor.

[0053] FIG. 6 illustrates a flow chart of a method.

DETAILED DESCRIPTION

[0054] FIG. 1 shows essential features of a first embodiment of a flowmeter 1 in an abstracted perspective sectional view. The flowmeter 1 has a sensor control 2, a measuring tube 3 and two flow sensors 4. Since the flow meter 1 is in operation, a multi-phase medium 5 flows through the measuring tube 3. The multi-phase medium 5 essentially has the phases water, oil and gas. The individual phases have different flow structures, which differ in their flow speeds and flow directions from one another. However, the medium 5 flows in its entirety in a total flow direction 6 through the measuring tube 3. In FIG. 1, an oil bubble 7 and a gas bubble 8 embedded in water 9 represent the flow structures of the medium 5 by way of example.

[0055] The flow sensor 4 has a sensor carrier 10 and this has a sensor array 11. The sensor array 11 has a sensor axis 12 and comprises a first permittivity sensor 13 for determining a first permittivity, a second permittivity sensor 14 for determining a second permittivity of the medium 5, and a density sensor 15 for determining a density of the medium 5. The sensors 13, 14 and 15 are arranged on the sensor axis 12 in such a manner that the density sensor 15 lies between the first permittivity sensor 13 and the second permittivity sensor 14.

[0056] One of the two flow sensors 4 is arranged at a first measuring position 16 on the measuring tube 3 so that the medium 5 flows around it. It has a first immersion depth into the medium 5 and its sensor axis 12 has a parallel component to a flow direction of the medium 5. The other of the two flow sensors 4 is arranged at a second measuring position 17 on the measuring tube 3 so that the medium 5 also flows around it. It has a second immersion depth into the medium 5 that is different from the first immersion depth and its sensor axis 12 has a parallel component to a flow direction of the medium 5. In this embodiment, the sensor axes 12 have, in particular, a parallel component to the total flow direction 6. In an alternative embodiment of the flowmeter, at least one of the two flow sensors is arranged on the measuring tube 3 rotated by 90 about its sensor axis.

[0057] FIG. 2a shows, in an abstracted perspective representation, essential features of the flow sensor 4. FIG. 2b is a sectional view of FIG. 2a, from which the electrical connections of the sensors 13, 14 and 15 with the sensor control 2 are also shown. The section is taken along a plane in which the sensor axis 12 is located. The flow sensor 4 is a first embodiment. As already described, the flow sensor 4 has the sensor carrier 10 with the sensor array 11. The sensor array 11 has the sensor axis 12, the first permittivity sensor 13, the second permittivity sensor 14 and the density sensor 15. The sensors 13, 14 and 15 are arranged on the sensor axis 12. The two permittivity sensors 13 and 14 are spaced apart with the permittivity sensor distance d, and the density sensor 15 is located between them.

[0058] The sensor carrier 10 is a printed circuit board. A circuit board, like the present one, consists of an electrically insulating plate-shaped carrier which is provided with a copper layer on each side. The material of the carrier is FR-4 in the present case. Traces are produced, for example, by selectively etching away the copper layers. Electrical connections between the two sides of the carrier are produced by vias.

[0059] The first permittivity sensor 13 and the second permittivity sensor 14 are designed identically, which is why only the first permittivity sensor 13 is considered below. The first permittivity sensor 13 is formed as a capacitance sensor having a first electrode 18 and a second electrode 19 for determining a capacitance of the medium 5. Each of the electrodes 18 and 19 is a trace of the circuit board. Since the capacitance of the medium 5 is determined at the electrodes 18 and 19, the electrodes 18 and 19 taken together are the sensitive area of the permittivity sensor 13. The width b and the length/of each of the electrodes 18 and 19 is b=1=0.5 mm. The distance a between the first electrode 18 and the second electrode 19 is a=0.2 mm. Thus, the sensitive region of the first permittivity sensor is smaller than smallest flow structures of the medium 5.

[0060] The sensor carrier 10 has a recess 20, in which the density sensor 15 is arranged. In this embodiment, the density sensor 15 is designed as a piezo sensor. Since a density of the medium 5 is determined on the side of the density sensor 15 that is completely in contact with the medium 5, this side is the sensitive region of the density sensor 15. The width b and the length/of this side are also b=1=0.5 mm. Thus, the sensitive area of the density sensor 15 is smaller than smallest flow structures of the medium 5.

[0061] By arranging the density sensor 15 in the recess 20 and forming the permittivity sensors 13 and 14 as traces, the surface of the flow sensor 4 is approximately flat. Since the traces of the permittivity sensors 13 and 14 could be damaged in direct contact with the medium 5, the traces are passivated. The passivation is carried out by a passivation layer 21 of amorphous carbon. FIG. 2b shows that the thickness of the passivation 21 is dimensioned such that the density sensor 15 is in direct contact with the medium 5 and the surface of the sensor array 11 is flat.

[0062] Furthermore, the electrical connection of the sensors 13, 14 and 15 with the sensor control 2 can also be seen in the sectional representation of the flow sensor 4. The electrical connection is effected by means of vias 22 and traces 23. In this case, the sensors 13, 14 and 15 are directly contacted by the vias 22, whereby no further traces are provided on the side of the sensor carrier 10 on which the electrodes 18 and 19 are arranged, which could impair determination of capacitance of the medium 5. The last section of the electrical connection is not represented by the traces 23, but by lines in abstracted form.

[0063] The sensor control 2 is designed for controlling the sensors 13, 14 and 15 of both flow sensors 4. This includes, in particular, determining permittivities of the medium 5 with each of the four permittivity sensors 13 and 14 and determining densities of the medium 5 with each of the two density sensors 15.

[0064] Since the sensor control 2 is designed identically with respect to the four permittivity sensors 13 and 14, the configuration of the sensor control with respect to the first permittivity sensor 13 is described below.

[0065] To determine a first permittivity of the medium 5 with the first permittivity sensor 13, the sensor control 2 has an electrical LC resonant circuit 24 with a resonance frequency. The first permittivity sensor 13 is a part of the resonant circuit 24. Since the electrodes 18 and 19 together with the medium 5 form a capacitor with a capacitance in which the medium 5 is a dielectric, the permittivity sensor 13 contributes to the capacitive component of the resonant circuit 24. The sensor control 2 determines the first permittivity of the medium 5 from the resonance frequency, taking into account that the resonance frequency depends on the capacitance and the capacitance on the permittivity of the medium 5.

[0066] In order to determine a second permittivity of the medium 5 with the second permittivity sensor 14, the sensor control 2 is configured accordingly.

[0067] FIG. 3 shows essential features of a second embodiment of a flow sensor 4 in an abstracted perspective view. The flow sensor 4 has a sensor carrier 10 with two sensor arrays 11. Each of the two sensor arrays 11 is identical to the sensor array of the first embodiment of a flow sensor 4. In the second embodiment illustrated in FIG. 3, the sensor axes 12 are aligned parallel to one another. The small size of the sensitive areas of the sensors 13, 14 and 15 with respect to the flow structures of the medium 5 makes possible the small distance of the sensor arrays 11 shown in FIG. 3. In conjunction with the parallel alignment of the sensor axes 12, determinations of permittivities and densities by the sensor arrays 11 have redundancies, which improves a measuring accuracy. In a third embodiment of the flow sensor 4, the sensor axes 12 of the sensor arrays 11 are not aligned parallel but perpendicular to one another, i.e. different, whereby the sensor axes 12 span a plane and the sensor arrays 11 are sensitive to flow speeds in directions different from one another.

[0068] FIG. 4 shows a second embodiment of a flowmeter 1. In contrast to the first embodiment, the second embodiment has only one flow sensor 4, and the sensor control 2 is designed correspondingly to the control of only one flow sensor. The rest of the second embodiment is identical to the first embodiment.

[0069] The sensor control 2 is designed to carry out a method with the method steps shown in FIG. 6 during operation of the flowmeter 1.

[0070] In a first method step 25, a first permittivity curve .sub.r,1 is determined with the first permittivity sensor 13, a second permittivity curve .sub.r,2 is determined with the second permittivity sensor 14, and a density curve of the medium 5 is determined with the density sensor 15. The first permittivity curve is shown in FIG. 5a, the density curve in FIG. 5b and the second permittivity curve in FIG. 5c.

[0071] In a second method step 26, speeds of phases of the multi-phase medium 5 are determined using a correlation method on the first permittivity curve .sub.r,1, the second permittivity curve .sub.r,2 and the density curve .

[0072] The correlation method includes specifying a permittivity limit value .sub.r,0 and a density limit value .sub.0. Considering that the permittivity of water is .sub.r,water=80, of oil is .sub.r,oil=2.5 and of gas is .sub.r,gas=1, and that the density of water is .sub.water=1000 kg/m.sup.3, of oil is .sub.oil=800 kg/m.sup.3, and of gas =1 kg/m.sup.3, the permittivity limit value is specified as .sub.r,0=40 and the density limit value is specified as .sub.0=500 kg/m.sup.3. The phase water is assumed above the permittivity limit value .sub.r,0, and the phase of oil or gas are below it. The phase water or oil is assumed above the density limit .sub.0, and the phase gas is assumed below it.

[0073] The second method step 26 has a plurality of sub-method steps.

[0074] In a first sub-method step 27, decreases in permittivity from above to below the permittivity limit value .sub.r,0 are detected in the first permittivity curve .sub.r,1, namely a first decrease in permittivity at time t.sub.2, and a second decrease in permittivity at time t.sub.6. These decreases in permittivity are also detected in the second permittivity curve .sub.r,2 at the times t.sub.1, and t.sub.5.

[0075] In a second sub-method step 28, permittivity change intervals t.sub.1=(t.sub.2t.sub.1) and t.sub.2=(t.sub.6t.sub.5) are determined between the decreases in permittivity in the first permittivity curve .sub.r,1 and in the second permittivity curve .sub.r,2, and using the permittivity change intervals t.sub.1 and t.sub.2 and the permittivity sensor distance d, speeds v.sub.1=d/t.sub.1 and v.sub.2=d/t.sub.2 of the decreases in permittivity are determined.

[0076] In a third sub-method step 29, speeds of the decreases in permittivity v.sub.1 and v.sub.2 are assigned to speeds of phases of the multi-phase medium 5 using the density curve and the first permittivity curve .sub.r,1 and the second permittivity curve .sub.r,2.

[0077] Since, during the first decrease in permittivity, the density curve remains above the density limit value .sub.0, it is oil and the speed v.sub.1=d/t.sub.1 is assigned to the oil bubble 9. Since, in the case of the second decrease in permittivity, the density curve runs from above to below the density limit value .sub.0, this is gas and the velocity v.sub.2=d/t.sub.2 is assigned to the gas bubble 10.

[0078] Thus, the flowmeters 1 are designed according to both embodiments for determining speeds of phases of a multi-phase medium.