TUBE FOR A TRANSDUCER, TRANSDUCER COMPRISING SUCH A TUBE, AND MEASURING SYSTEM FORMED THEREWITH

Abstract

The tube is used to conduct a fluid flowing through the tube in a specified flow direction and for this purpose comprises a tube wall (110), which encloses a lumen (100*) of the tube, and an interference body (120), which is arranged within the tube but is nevertheless connected to the tube wall at an inner face of the tube wall facing the lumen. In the tube according to the invention, the tube wall has a maximum wall thickness (s.sub.max) of more than 1 mm and at least two mutually spaced sub-segments (100-1, 100-2) with a respective wall thickness (s.sub.110-1, s.sub.110-2) that deviates from said maximum wall thickness (smax), wherein the sub-segment (100-1) is positioned upstream of the interference body (120) in the flow direction, and the sub-segment (100-2) is positioned downstream of the sub-segment (100-1) in the flow direction.

Claims

1. A tube for conducting a fluid flowing through the tube in a predetermined flow direction, comprising: an, especially metallic and/or monolithic, tube wall (110), which encloses a lumen (100*) of the tube; and an, especially metallic and/or monolithic, bluff body (120), which is arranged within the tube, but is nevertheless connected thereto on an inner side of the tube wall facing the lumen (100*); the tube wall (110) having a maximum wall thickness (s.sub.max) measuring more than 1 mm, especially, more than 2 mm; and the tube wall (110) comprising at least two mutually spaced, especially, equally large and/or equally shaped sub-segments (110-1, 110-2), each having a wall thickness (s.sub.110-1, s.sub.110-2) deviating from the maximum wall thickness, especially, by more than 30% of said maximum wall thicknesses and/or by more than 1 mm, and measuring, especially, less than 1 mm and/or more than 0.1 mm, of these two sub-segments (110-1, 110-2) a first sub-segment (110-1) being positioned upstream of the bluff body (120) in the flow direction, and a second sub-segment (110-2) being positioned at least partially in the flow direction downstream of the sub-segment (110-1), especially, namely at least partially, in the region of the bluff body (120) and/or at least partially in the flow direction downstream of the bluff body (120).

2. The tube according to any one of the preceding claims, wherein the tube has a maximum first flow cross section (A.sub.1) that measures, especially, more than 20 mm.sup.2 and/or has a circular design.

3. The tube according to the preceding claim, wherein the tube, in at least one region adjoining the bluff body (120), especially, namely formed between the bluff body and the tube wall, has a second flow cross-section (A.sub.2) deviating from said maximum flow cross-section with respect to size and/or shape.

4. The tube according to the preceding claim, wherein, in a region located upstream of the bluff body (120) in the flow direction, but nevertheless downstream of the first flow cross-section (A.sub.1), the tube has a third flow cross-section (A.sub.3) which deviates both from the first flow cross-section (A.sub.1) and from the second flow cross-section (A.sub.2) and is, especially, circular and/or designed to be larger than the second flow cross section of the tube; and, in a region located downstream of the bluff body (120) in the flow direction, the tube has a fourth flow cross-section (A.sub.4) which deviates both from the first flow cross-section and from the second flow cross-section with respect to size and/or shape and is, especially, designed to be identical to the third flow cross-section and/or circular and/or designed to be larger than the second flow cross section of the tube.

5. The tube according to any one of the preceding claims, wherein the tube, upstream of the bluff body (120) in the flow direction, comprises an, especially, hollow cylindrical, first sub-segment (100-1) that encloses a cylindrical, especially, circular cylindrical, first region of the lumen, and the tube, downstream of the bluff body in the flow direction, comprises an, especially hollow cylindrical, second sub-segment (100-2) that encloses a cylindrical, especially, circular cylindrical, second region of the lumen.

6. The tube according to claims 4 and 5, wherein the first sub-segment (100-1) forms the third flow cross-section (A.sub.3); and wherein the second sub-segment (100-2) forms the fourth flow cross-section (A.sub.4).

7. The tube according to any of claims 5 to 6, wherein the tube, upstream of the first sub-segment (100-1) thereof in the flow direction, comprises a third sub-segment (100-3) that encloses a conical third region of the lumen, especially, forming a concentric reduction in the flow direction, and, especially, forms the first flow cross-section.

8. The tube according to claim 7, wherein the tube (100), downstream of the second sub-segment (100-2) thereof in the flow direction, comprises a fourth sub-segment (100-4) having a flow cross-section deviating from the flow cross-section of the second sub-segment (100-2).

9. The tube according to any one of the preceding claims, wherein the first sub-segment of the tube wall is circular and/or planar on an outer side facing away from the lumen; and/or wherein the second sub-segment of the tube wall is circular and/or planar on an outer side facing away from the lumen; and/or wherein the first and second sub-segments of the tube wall are equally large and/or equally shaped, especially, namely identical.

10. The tube according to any one of the preceding claims, wherein the tube wall and the bluff body are components of one and the same monolithic molded part; and/or wherein the tube wall and the bluff body are made of the same material.

11. The tube according to any one of the preceding claims, wherein the inner side of the tube wall has no weld seams; and/or wherein the tube wall is free of joints; and/or wherein the inner side of the tube wall has no protrusions; and/or wherein the inner side of the tube wall is smooth at least in the region of the sub-segments; and/or wherein tube wall has no apertures or openings.

12. The tube according to any one of the preceding claims, further comprising: a first connecting flange (130) surrounding a lateral first tube end (100+) on the inlet-side in the flow direction; and a second connecting flange (140) surrounding a second tube end (100#) on the outlet-side in the flow direction.

13. The tube according to the preceding claim, wherein the tube wall and the first and second connecting flanges are components of one and the same monolithic molded part.

14. The tube according to any one of the preceding claims, wherein the bluff body is configured to increase a flow velocity of a fluid flowing past and/or through and/or to decrease a static pressure prevailing in a fluid flowing past and/or through and/or to provoke a pressure difference, dependent on a volumetric flow, along a measuring section formed by means of the first and second sub-segments of the tube wall.

15. The tube according to any one of the preceding claims, wherein the bluff body is configured to induce vortices in the fluid flowing past, especially, in such a way that a Krmn vortex street is formed in the fluid flowing downstream of the bluff body and/or along a measuring section formed by means of the first and second sub-segments of the tube wall.

16. The tube according to any one of the preceding claims, wherein the bluff body is designed as a prismatically shaped disturbance body.

17. The tube according to any one of claims 1 to 15, wherein the bluff body is designed as an orifice plate, especially, namely as a standard orifice plate.

18. The tube according to any one of the preceding claims, produced by a metal injection molding (MIM) method.

19. A transducer for detecting at least one measurement variable of a flowing fluid, the transducer comprising: a tube (100) according to any one of the preceding claims; an, especially, piezoelectric or capacitive or optical, first sensor element (210), which is fixed to the first sub-segment of the tube wall and/or in the vicinity thereof and is configured to detect elastic deformations of said sub-segment and to convert these into a first sensor signal corresponding to said deformations, especially, using a voltage dependent on said deformation and/or an electrical current dependent on said deformation; and a second sensor element (220) that is, especially, piezoelectric or capacitive or optical and/or designed identically to the first sensor element, which is fixed to the second sub-segment of the tube wall and/or in the vicinity thereof and is configured to detect elastic deformations of said sub-segment and to convert these into a second sensor signal corresponding to said deformations, especially, using a voltage dependent on said deformation and/or an electrical current dependent on said deformation.

20. A measuring system for measuring at least one flow parameter that is, especially, variable over time, especially, a flow velocity and/or a volumetric flow, of a fluid flowing in a pipe, the measuring system comprising: a transducer (10) according to claim 19 for detecting pressure fluctuations in the flowing fluid, especially, namely for detecting pressure fluctuations in a Krmn vortex street formed in the flowing fluid, and/or for detecting a pressure drop occurring in the flowing fluid; and a measurement electronics unit (20), which is configured to receive and process the first sensor signal and the second sensor signal, especially, namely, to generate measurement values (X.sub.M) representing the at least one flow parameter.

Description

[0029] The invention as well as advantageous embodiments thereof are explained in more detail below based on exemplary embodiments shown in the figures of the drawing. Identical or identically acting or identically functioning parts are provided with the same reference signs in all figures; for reasons of clarity or if it appears sensible for other reasons, reference signs mentioned before are dispensed with in subsequent figures. Further advantageous embodiments or developments, in particular combinations of partial aspects of the invention that were initially explained only separately, furthermore result from the figures of the drawing and from the claims themselves.

[0030] The figures show in detail:

[0031] FIG. 1 in a side view, shows a measuring system formed by means of a transducer and a measurement electronics unit connected thereto for measuring a measurement variable of a fluid flowing in a pipe;

[0032] FIG. 2 in a top view, shows a transducer suitable for a measuring system according to FIG. 1;

[0033] FIGS. 3A, 3B in a sectional side view and a front view, respectively, show a variant of a transducer suitable for a measuring system according to FIG. 1; and

[0034] FIGS. 4A, 4B in a sectional side view and in a front view, respectively, show a further variant of a transducer suitable for a measuring system according to FIG. 1.

[0035] FIG. 1, 2, 3A, 3B, 4A or 4B are exemplary embodiments of a measuring system for measuring at least one measurement variable, which may optionally also be variable over time, especially, a flow parameter such as, e.g., a flow velocity v and/or a volumetric flow V, of a fluid flowing in the pipe. The pipe can be designed, for example, as an equipment component of a bottling facility, of a heat supply network or of a turbine circuit, so that the fluid can be, for example, an aqueous liquid, steam or, for example, also a condensate discharged from a steam line. However, fluid can also be, for example, (compressed) natural gas or a biogas, so that the pipe can also be a component of a natural gas or biogas plant or of a gas supply network, for example.

[0036] In order to detect the at least one measurement variable, the measuring system comprises a transducer 10, which is provided or designed for fluid to flow through in a flow direction during operation and/or to detect pressures that vary over time in the flowing fluid and/or a pressure drop occurring in the flowing fluid and/or pressure fluctuations in the flowing fluid, for example in a Krmn vortex street formed therein, and to convert it/them into two, for example electrical or optical, sensor signals s1, s2 corresponding thereto. In addition, the measuring system comprises a measurement electronics unit 20, which is configured to receive and process the aforementioned sensor signals, for example, namely, to generate measurement values X.sub.M representing the at least one flow parameter. As is apparent from FIG. 1, the measuring system for this purpose furthermore comprises a measurement electronics unit 20for example accommodated in a pressure-resistant and/or impact-resistant protective housing 200which is electrically connected to the transducer 10 or communicates with the transducer 1 during operation of the measuring system. The measurement electronics unit 20 is, especially, configured to receive and process the sensor signals s1, s2, for example, namely, to generate measurement values X.sub.M representing the at least measurement variable. The measurement values X.sub.M can be visualized on-site and/or transmittedby wire or in conformity with DIN 60381-1 via a connected field bus and/or wirelessly by radio or in conformity with IEEE 802.15.1 or IEEE 802.15.4to an electronic data processing system, such as a programmable logic controller (SPS) and/or a process control station. The protective housing 200 for the measurement electronics unit 20 may, for example, be produced from a metal, such as a stainless steel or aluminum, and/or by means of a casting method, such as an investment casting or die casting method (HPDC); it can however, for example, also be formed by means of a plastic molded part produced in an injection molding method. As is also illustrated in FIG. 1, the measuring system can also be designed, for example, as a compact measuring system in which the protective housing 200, together with the measurement electronics unit 20 arranged therein, is positioned directly at the transducer 10 and is connected rigidly, possibly also releasably, to the transducer 10for example by means of a neck-shaped connecting piece 300.

[0037] To conduct the flowing fluid, the transducer, as is also shown in FIGS. 3A and 3B, as well as 4A and 4B and is readily apparent from a combination of the figures, comprises a tube 100 including afor example metallic and/or monolithictube wall 110 enclosing a lumen 100* of the tube, and afor example metallic and/or monolithicbluff body 120 arranged inside the tube 100 or the lumen 100 thereof, but nevertheless connected thereto at an inner side of the tube wall 110 facing the lumen 100. Said bluff body 120 can be provided or configured, for example, to increase a flow velocity of a fluid flowing past and/or through and/or to decrease a static pressure prevailing in a fluid flowing past and/or through, for example also in such a way that in this way a pressure difference, dependent on a volumetric flow, is provoked in the flow direction. As an alternative or in addition, the bluff body can also be designed to induce vortices in the fluid flowing past, for example also in such a way that a Krmn vortex street is formed in the fluid flowing downstream of the bluff body. The tube wall and the bluff body can advantageously be made, for example, of the same material, for example, namely, a steel, optionally also a stainless steel, or a nickel-based alloy. According to a further embodiment of the invention, the tube wall and the bluff body are components of one and the same monolithic molded part. As a result, the tube wall can advantageously be kept free of jointswhich are usually complex to create and/or to testor undesirable or disruptive weld seams on the inner side of the tube wall can be avoided. According to a further embodiment of the invention, the tube is produced by a metal injection molding (MIM) method for this reason. In the metal injection molding method, initially a pasty, but nevertheless sprayable composition having a metal powder content of typically more than 90 wt. % (percent by weight) is produced from a fine metal powder and a likewise pulverulent plastic material and processed by means of an injection molding machinewhich is also suitable, for example, for conventional plastic injection moldingto form a molded part corresponding to the tube to be produced. Moreover, in the metal injection molding process, the plastic material is removed again from this molded part while retaining its shape, and the metal remaining in the molded part is finally sintered. By employing such a metal injection molding method for producing the tube, the tube wall 110, and last but not least also the sub-segments 110-1, 110-2 thereof, can be manufactured very precisely, possibly even while avoiding otherwise very complex reworking of the tube 100 or of the surfaces thereof.

[0038] According to another embodiment of the invention, the tube 100 further has, as is also indicated in FIGS. 3A and/or 3B or readily apparent from a combination of FIGS. 3A, 3B, 4A and 4B, a first flow cross-section A.sub.1for example, measuring more than 20 mm.sup.2 and/or having a circular designwhich at the same time corresponds to a maximum flow cross-section of the tube 100 (A1.fwdarw.Amax). In the case of a lumen 100 having only circular flow cross-sections, a diameter of the flow cross-section A.sub.1, for example also measuring more than 5 mm, also corresponds to a maximum diameter of the lumen 100*. For the purpose of incorporating the tube or the transducer formed therewith, according to a further embodiment of the invention the tube 100 can comprise a first connecting flange 130 receiving a first tube end 10+ on the inlet-side in the flow direction, and a second connecting flange 140 receiving a second tube end 10# on the outlet-side in the flow direction. As is also indicated in each of FIGS. 1, 3A and 4A, the tube wall 110 and connecting flanges 130, 140 may moreover also comprise, for example, components of one and the same monolithic molded part, for example also comprising the bluff body 120.

[0039] The tube 100 can further, for example, be designed so as to comprise, upstream of the bluff body 120 in the flow direction, a, for example also hollow cylindrical, first sub-segment 100-1 that encloses a cylindrical, optionally alsoas is indicated in each case in FIGS. 3A and 3B and 4A and 4B circular cylindrical first region of the lumen and, downstream of the bluff body 120 in the flow direction, comprises a, for example hollow cylindrical, second sub-segment 100-2 that encloses a cylindrical, for example circular cylindrical, second region of the lumen. According to a further embodiment of the invention, it is further provided that the tube 100, in addition to the aforementioned sub-segments 100-1, 100-2, upstream of the aforementioned sub-segment 100-1 in the flow direction, comprises a third sub-segment 100-3 that encloses a conical third region of the lumen, for example forming a concentric reduction in the flow direction, and optionally also forms the flow cross-section A.sub.1. Downstream of the aforementioned sub-segment 100-2 in the flow direction, the tube 100 can comprise a fourth sub-segment 100-4, which forms a diffuser or, in the flow direction, a widening, or else forms a throttle or, in the flow direction, a reduction and which has a flow cross-section that deviates from the flow cross-section of the sub-segment 100-2, for example that is increased or reduced compared to said flow cross-section of the sub-segment 100-2.

[0040] According to a further embodiment of the invention, the tube 100, as is indicated in each case in FIGS. 3A and 3B or is apparent from their combination, in at least one region adjoining the bluff body 120, for example also formed between the bluff body 120 and the tube wall 110, has a second flow cross-section A.sub.2 deviating from the aforementioned maximum flow cross-section A.sub.1 with respect to size and/or shape. Moreover, in a region located upstream of the bluff body 120 in the flow direction, but nevertheless downstream of the flow cross-section A.sub.1, the tube 100 can have a third flow cross-section A.sub.3for example, also designed to be larger than said flow cross section A.sub.2which deviates both from said flow cross-section A.sub.1 and from the aforementioned flow cross-section A.sub.2 with respect to the and/or shape, and, in a region located downstream of the bluff body 120 in the flow direction, a fourth flow cross-section A.sub.4for example, also designed to be identical to the aforementioned flow cross-section A.sub.3 and/or designed to be larger than the flow cross section A.sub.2which likewise deviates both from the flow cross-section A.sub.1 and from the flow cross-section A.sub.2 with respect to size and/or shape. The flow cross-section A.sub.3 and/or the flow cross-section A.sub.4 may also be designed to be circular, for example. In addition, the flow cross-section A.sub.3 can be formed by the aforementioned sub-segment 100-1 of the tube 100, and the flow cross-section A.sub.4 can be formed by the aforementioned sub-segment 100-2 of the tube 100.

[0041] In the case of the tube 100 according to the invention, the tube wall 110 has a maximum wall thickness s.sub.max measuring more than 1 mm, which, for example, is constant circumferentially or along an imaginary circumferential line, and at least two mutually spaced, especially in the flow direction, for example equally large and/or equally shaped, sub-segments (110-1, 110-2), each having a wall thickness s.sub.110-1 or s.sub.110-2 deviating from the aforementioned maximum wall thickness s.sub.max (namely being less compared thereto), of these two sub-segments, as is also apparent from FIGS. 3A and 4A, a first sub-segment 110-1 being positioned upstream of the bluff body 120 in the flow direction, and a second sub-segment 110-2 being positioned downstream of the sub-segment 110-1 in the flow directionfor example, namely, also at least partially in the region of the bluff body 120, optionally also partially in the flow direction downstream of the bluff body 120. The two sub-segments 110-1, 110-2 are provided, especially, so as to each receive at least one sensor element used for generating one of the aforementioned sensor signals or form corresponding sensor pockets of the tube. The sub-segments 110-1, 110-2 of the tube wall 110 can advantageously be accordingly designed to be equally large and/or equally shaped, for example, namely, identically designed, and/or be circular. Alternatively or in addition, the sub-segment 100-1 and/or the sub-segment 100-2 can be flat on a respective outer side facing away from the lumen, for example so as to allow the respective sensor element to be coupled as simply as possible to the respective sub-segment. As a result, the tube wall can advantageously also be designed, for example, so as not to have any apertures or openings and/or so as not to include any protrusions or so as to be smooth at least in the region of the sub-segments 110-1, 110-2.

[0042] According to a further embodiment of the invention, the transducer formed by means of the tube 100 accordingly comprises a first sensor element 210, which is fixed to the sub-segment 110-1 or in the vicinity thereof, for example integrally or adhesively, and is configured to detect elastic deformations of said sub-segment and convert these into a first sensor signal corresponding to said deformations, for example, namely, using a voltage dependent on said deformation and/or an electrical current dependent on said deformation. The transducer further comprises a second sensor element 220, for example also identical to the sensor element 210, which is fixed to the sub-segment 110-2 or in the vicinity thereof, for example, integrally or adhesively, and is configured to detect elastic deformations of said sub-segment and to convert these into a second sensor signal corresponding to said deformations, for example using a voltage dependent on said deformation and/or an electrical current dependent on said deformation. Each of the sensor elements 210, 220 may, for example, be designed as a piezoelectric, capacitive or also optical sensor element. The wall thickness s.sub.110-1, s.sub.110-2 of the aforementioned sub-segments 110-1, 110-2 is advantageously selected in each case in such a way that, during operation, a deformation sufficient for generating or processing the sensor signals s1, s2 is made possible, but nevertheless sufficient compressive strength of the tube is ensured, and can measure less than 1 mm and/or more than 0.1 mm, for example, and/or can also be selected in each case, for example, so as to deviate from the maximum wall thickness by more than 1 mm and/or by more than 30% of the maximum wall thicknesses. The aforementioned maximum wall thickness can, in turn, also be more than 2 mm, for example, namely, also more than 5 mm. According to a further embodiment of the invention, it is further provided that each of the sub-segments 110-1, 110-2 on the respective side facing away from the lumen 100* in each case has a largest diameter, which is not greater than a maximum diameter of the aforementioned flow cross-section A.sub.1 and/or is less than 20 mm.

[0043] According to another embodiment of the invention, the bluff body is configured to induce vortices in a fluid flowing past in such a way that a Krmn vortex street is formed in the fluid flowing downstream of the bluff body 120 and/or along a measuring section formed by means of the sub-segments 110-1, 110-2 of the tube wall 110, and/or the bluff body 120, as is also indicated in FIGS. 3A and 3B or apparent from their combination, is designed as a prismatically shaped disturbance body. The sub-segments 110-1, 110-2 of the tube wall 110 and the bluff body 120 are, especially, dimensioned and arranged in the process in such a way that the sub-segment 110-2 adjoins the lumen 100* of the tube 100 in a region, or makes contact with the fluid conducted in a region, that during operation of the measuring systemdesigned, for example, as a vortex flow meteris regularly taken up by the aforementioned Krmn vortex street, so that the pressure fluctuations detected by means of the sensor element 220 and caused by vortices shed at the bluff body 120 at a shedding rate (1/f.sub.Vtx) are periodic pressure fluctuations, and the sensor signal s2 has a signal frequency (f.sub.Vtx) corresponding to the shedding rate of said vortices. The measuring electronics unit 20 can accordingly further also be configured to ascertain a measurement variable to be detected, for example, namely, the flow velocity and/or the volumetric flow, based on the signal frequency of the sensor signal s2, optionally alsoas shown in the aforementioned JP-A 0682281taking into account also the sensor signal s1.

[0044] According to another embodiment of the invention, the bluff body 120 is provided or configured to provoke a pressure difference, dependent on a volumetric flow, along a measuring section formed by means of the aforementioned sub-segments 100-1, 100-2 of the tube wall 110, and/or the bluff body, as is also schematically shown in FIGS. 4A and 4B or is apparent from their combination, is designed as an orifice plate, for example, namely, as a standard orifice plate. The measuring electronics unit 20 may further also be configured to ascertain, based on the sensor signals s1, s2, the aforementioned pressure difference and, derived therefrom, measurement values for the at least one measurement variable to be detected.