Measuring tube for use in an ultrasonic measuring device, and ultrasonic measuring device

Abstract

The invention relates to a measuring tube (1) for use in an ultrasonic measuring device (10), comprising: - a measuring tube body (2), wherein the measuring tube body (2) has a first and second measuring portion (MA1, MA2), the measuring tube body (2) having a first measuring portion contour (MK1) in the first measuring portion (MA1) and a second measuring portion contour (MK2) in the second measuring portion (MA2), the first measuring portion contour (MK1) differing from the second measuring portion contour (MK2); the measuring tube body (2) has an inlet portion (EA), an outlet portion (AA), and a first transition portion (ÜA1) between the inlet portion (EA) and the first measuring portion (MA1), the first and second measuring portions (MA1, MA2) being separated by a second transition portion (ÜA2); a first transition portion contour (ÜK1) changes from the first measuring portion contour (MK1) into the second measuring portion contour (MK2) in the flow direction; and the measuring tube body (2) has a third transition portion (ÜA3) between the outlet portion (AA) and the second measuring portion (MA2). The invention also relates to an ultrasonic measuring device (10).

Description

[0001] Measuring tube for use in an ultrasonic measuring device and ultrasonic measuring device

[0002] The invention relates to a measuring tube for use in an ultrasonic measuring device and an ultrasonic measuring device for determining a medium property.

[0003] There are numerous ultrasound-based measuring devices. Lamb wave technology occupies a special position among them. It enables the generation and reception of ultrasound by transducer elements located outside the process, thus protecting these elements from aggressive media and eliminating the need for bores, pockets, or recesses in the measuring tube. Furthermore, the large-area vibration excitation of the tube wall, compared to conventional ultrasound technology, couples the acoustic energy into a correspondingly large area of ​​the adjacent medium, making the resulting sound beam relatively robust against particles (solids) and bubbles (gas inclusions) contained in the flow.

[0004] For certain measuring instruments, especially flow meters, it is advantageous to have off-center measuring paths. Such measuring paths allow, firstly, better coverage of the different areas of the measuring cross-section (outer, transition, inner regions), and secondly, reduce sensitivity to changes in the flow profile due to Reynolds number-dependent effects and upstream flow disturbances.

[0005] To implement such off-center measurement paths, especially those based on Lamb waves, cost-effectively, ideally with only two ultrasonic transducers, the measuring tube requires flat, parallel outer surfaces. Therefore, it is necessary to design at least parts of the measuring tube with flat sections.

[0006] Several ultrasonic flowmeters are already known in which measuring tubes with planar sections are used. For example, DE 198 23 165 A1 discloses an ultrasonic flowmeter with a measuring tube that has a square or rectangular inner cross-section in one measuring range. The end flanges of the ultrasonic flowmeter each have an opening with a quasi-conical shape that tapers towards the square or rectangular inner cross-section. DE 198 23 165 A1 aims to provide a measuring tube that can be fully emitted by clampable ultrasonic transducers. Furthermore, by selecting the appropriate tube wall geometry, a number of parallel ultrasonic beams can be generated to radiate the flow within the measuring tube in such a way that parallel summation is possible instead of Gaussian chord summation of individual paths.DE 10 2017 115 431 A1 discloses a measuring device with a measuring tube which has a substantially rectangular internal cross-section in a measuring section and a non-rectangular internal cross-section in a connecting section. A transition section located between the measuring section and the connecting section has an internal cross-section identical to that of the measuring section at one end and an internal cross-section identical to that of the connecting section at the other. The internal cross-section of the transition section changes continuously along its entire length between the two ends. Thus, the transition between areas with different internal cross-sections is smooth and without hard, abrupt transitions or steps.This prevents increased flow separation and thus uneven flow profiles, high turbulence and pressure losses, which can distort measurements.

[0007] Furthermore, EP 3 388 794 A1 describes a measuring device for measuring the flow velocity of a fluid using a measuring tube. This tube has a rectangular measuring section, an inlet section with a first superelliptical transition shape, and an outlet section with a second superelliptical transition shape. The purpose of EP 3 388 794 A1 is to provide a measuring tube with a particularly homogeneous transition geometry from the circular section to the rectangular measuring section, thus preventing flow separation and achieving improved flow velocity measurement quality despite its short overall length.

[0008] Numerous manufacturing technologies exist for producing measuring tubes with planar outer surfaces, such as conventional internal machining (milling), wire EDM of an internal profile, extrusion of an internal profile, additive manufacturing, or investment casting combined with abrasive polishing. All these methods share the common characteristics of long production times and / or the need for a large amount of raw material to achieve the desired measuring cross-section. The transitions from the process connections, which are typically circular, to the section containing the ultrasonic measuring paths represent the most critical and complex part of the measuring tube, as a continuous and therefore fluid-mechanically efficient geometric transition must be created. Consequently, the production of such measuring tubes is expensive and often not competitive.

[0009] Ultrasonic flowmeters are known that operate using a so-called two-path arrangement. This measurement is performed using two or more pairs of ultrasonic transducers. This arrangement has the advantage that measurement inaccuracies in flow profiles that are not completely symmetrical, especially those that are not completely rotationally symmetrical, can be partially compensated for. Such disturbances are caused by components that are connected to a pipeline and subsequently form part of the pipe or are defined as pipe elements. This includes, among others, elbows, valves, and pumps. Depending on the type of disturbance, it is therefore recommended to maintain a certain minimum distance when positioning the ultrasonic flowmeter, as otherwise a device-specific upper limit for measurement accuracy can no longer be guaranteed.

[0010] However, there are known applications where this minimum distance, the so-called inlet section, cannot be maintained. In such applications, significant measurement errors occur due to the incomplete flow profile. In this case, the customer also lacks information regarding the accuracy and reliability of the measurement, which would allow them to assess and evaluate the quality of the data obtained.

[0011] US20190186967A1 discloses a flow measurement system with an ultrasonic flow meter as the flow meter and transmitter electronics configured to determine exactly one dimensionless quantity PF (“profile factor”) from four locally determined flow velocities and, depending on the PF, to determine a correction quantity MF (“meter factor”) to correct the measured value of the flow velocity of the medium.

[0012] DE19717940A1 discloses a method for determining the vortex intensity of the medium to be monitored for an ultrasonic flow meter. In this method, a ratio between the angular momentum and longitudinal momentum of the medium is used to determine the vortex intensity, which is then used to correct the measured flow rate.

[0013] EP0804717B1 aims to provide an ultrasonic flowmeter with improved measurement accuracy. This is achieved by determining a current Reynolds number, for which an operating flow profile is first recorded as a function of several measured values ​​of the medium's flow velocity, in order to account for the influence of inlet effects. It has been shown that such methods assume that a flow profile is already essentially formed and does not deviate significantly from rotational symmetry.

[0014] DE102013106108A1 discloses a method for determining a compensated flow rate in which, taking into account a distance of the measuring setup to the disturbance, the type of disturbance and optionally the Reynolds number, the correction factor to be applied is determined and used for determining the flow rate.

[0015] A disadvantage of the aforementioned prior art is that, in addition to the determined local measurements of the flow velocity-dependent quantity, further information is always required to identify the flow profile in order to determine a unique correction value suitable for the given situation. The undisclosed DE 10 2024 117 335.1 solves this problem by using multiple ultrasonic transducers that span at least three different signal paths through the medium channel. This allows for the generation of a large number of local measurement tuples specific to the given flow profile. Based on these, the influence of flow asymmetry can be corrected from the measurement results. This is particularly advantageous for ultrasonic measuring devices with a small nominal diameter ( <DN25, insbesondere <DN15) gibt es jedoch keine geeigneten Messrohre, welche die Anforderungen der DE 10 2024 117 335.1 erfüllen.

[0016] The invention is based on the objective of providing a remedy.

[0017] The problem is solved by the measuring tube according to claim 1 and the ultrasonic measuring device according to claim 11.

[0018] The measuring tube according to the invention for use in an ultrasonic measuring device, comprising:

[0019] - a measuring tube body, wherein the measuring tube body has a first and second measuring section, wherein the measuring tube body has a first measuring section contour in the first measuring section, wherein the measuring tube body has a second measuring section contour in the second measuring section, wherein the first measuring section contour differs from the second measuring section contour, wherein the measuring tube body has an inlet section and an outlet section, wherein the measuring tube body has a first transition section between the inlet section and the first measuring section, wherein the first and second measuring sections are separated by a second transition section, wherein a first transition section contour changes from the first measuring section contour in the flow direction until it assumes the second measuring section contour, wherein the measuring tube body has a third transition section between the outlet section and the second measuring section.

[0020] The measuring tube according to the invention allows two ultrasound pairs, offset in the direction of flow, to be arranged on the measuring tube body. These pairs have measuring paths of different lengths, and their measuring paths are subject to different influences from the current flow profile as they pass through the medium. This also makes it possible to preferably form symmetrically intersecting measuring paths, which allow asymmetrical flow components in the medium, e.g., due to upstream flow disturbances, to be largely compensated for inherently.

[0021] The invention solves the problem that, given the requirement to implement measurement paths of different lengths and covering different flow regions, and the limitation of the minimum possible widths of the transducer elements, the transducer elements can no longer be arranged within a single measurement section. According to the invention, this problem is solved by a measuring tube in which the ultrasonic transducer pairs can be arranged in two measurement sections offset in the flow direction.

[0022] Advantageous embodiments of the invention are the subject of the dependent claims.

[0023] One embodiment provides that the measuring tube body in the first measuring section has an (outer) planar first, second and third surface, wherein in a first cross-section through the measuring tube body in the first measuring section a first straight line lying in the first planar surface, a second straight line lying in the second planar surface and a third straight line lying in the third planar surface span a triangle, in particular an isosceles triangle.

[0024] One embodiment provides that in the first cross-section the first straight line and the second straight line span an angle α, with 20° < α < 32°, in particular 22° < α < 28° and preferably 26°.

[0025] One embodiment provides that the first, second and / or third surface (each) has a width B and preferably a wall thickness of 0.5 to 1 millimeter, wherein the width B is such that 2.7 < B < 3.3 millimeters, and preferably B = 3 millimeters.

[0026] One embodiment provides that the measuring tube body in the second measuring section has an (outer) planar fourth and fifth surface, wherein the second measuring section contour assumes an oval basic shape, which is designed such that the fourth and fifth surfaces run parallel to each other at least section by section.

[0027] One embodiment provides that the measuring tube body has an inlet section contour in the inlet section, wherein the inlet section contour assumes a (circular) round basic shape, wherein the measuring tube body has an outlet section contour in the outlet section, wherein the outlet section contour assumes a (circular) round basic shape, and wherein the inlet section contour and the outlet section contour are identical.

[0028] One embodiment provides that the measuring tube is designed such that it is self-emptying at an inclination of less than or equal to 3°, and in particular at least at an inclination of 3° relative to the horizontal. Another embodiment provides that the measuring tube body has a curvature in its first cross-section with a radius of curvature R, in particular exactly three curvatures, each with a radius of curvature R, where the radius of curvature R is such that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters, and preferably R = 2.1 millimeters.

[0029] One embodiment provides that the measuring tube body has an inner first circumference in the first measuring section, wherein the measuring tube body has an inner second circumference in the second measuring section, wherein the measuring tube body has an inner third circumference in the inlet section, wherein the first, second and third circumferences do not deviate from each other by more than 3%, in particular not by more than 1.5%.

[0030] One embodiment provides that the measuring tube body has an inner fourth circumference in the second transition section, wherein the first, second and fourth circumferences do not differ from each other by more than 3%, in particular not by more than 1.5%.

[0031] The ultrasound measuring device according to the invention for determining a medium property comprises:

[0032] - a measuring tube, in particular produced by means of a hydroforming process, according to one of the preceding claims, wherein the measuring tube is configured to guide a medium;

[0033] - at least two pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least two pairs of ultrasonic transducers comprise a first pair of ultrasonic transducers arranged in the first measuring section, wherein the first pair of ultrasonic transducers has a first and second transducer element, wherein the first transducer element is arranged on the second surface, wherein the second transducer element is arranged on the third surface, wherein the first and second transducer elements form a 2-crossbeam arrangement, wherein the at least two pairs of ultrasonic transducers comprise a second pair of ultrasonic transducers arranged in the second measuring section, wherein the second pair of ultrasonic transducers has a first and a second transducer element, wherein the first transducer element is arranged on the fourth surface, wherein the second transducer element is arranged on the fifth surface.wherein the first and second converter elements form a 1-crossbeam arrangement;

[0034] - measuring electronics which are electrically connected to the at least two pairs of ultrasonic transducers, wherein the measuring electronics are configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and

[0035] - a housing, wherein the housing surrounds the at least two pairs of ultrasonic transducers.

[0036] There can be at least one surface on which two transducer elements are arranged, their sound paths directed towards each other. The aim is to select the ultrasonic wave generated and measured in this way to determine a reference signal, since the ultrasonic wave does not travel through the medium and is therefore not influenced by it, but moves exclusively within the pipe wall or on the pipe surface. With the reference signals determined in this way (or quantities derived from them, such as amplitude or transit time), effects such as temperature or material influence can later be compensated for to a certain extent.

[0037] One embodiment provides that the at least two pairs of ultrasound transducers comprise a third pair of ultrasound transducers, which is arranged in the second measuring section, wherein the transducer elements of the third ultrasound transducer form a 1-crossbeam arrangement, wherein the at least two pairs of ultrasound transducers comprise a fourth pair of ultrasound transducers, which is arranged in the first measuring section, wherein the transducer elements of the fourth ultrasound transducer form a 2-crossbeam arrangement.

[0038] One embodiment provides that the transducer elements are each configured to couple ultrasonic waves into the medium, wherein the measuring tube body has an inner lateral surface which, in the first measuring section, has a planar and parallel inner surface to the first, second and third surfaces, and wherein, in the second measuring section, the inner lateral surface has a planar and parallel inner surface to the fourth and fifth surfaces, and wherein the transducer elements are each arranged on the measuring tube such that a principal axis of the coupling ultrasonic wave intersects one of the inner surfaces and / or a principal axis of the respective transducer elements intersects at least one of the inner surfaces orthogonally.

[0039] One embodiment provides that the measuring tube body has a plane of symmetry in the first measuring section, whereby the respective principal axes of the ultrasonic waves generated by means of the first and second transducer elements intersect in the plane of symmetry.

[0040] One embodiment provides that the ultrasonic measuring device has a main axis of the measuring device which runs perpendicular to a longitudinal axis of the measuring tube, wherein the measuring tube is arranged in the housing such that the main axis of the measuring device intersects the plane of symmetry with an angle β, wherein the angle β is such that 50° < β < 70°, in particular 55° < β < 65° and preferably β = 60°.

[0041] The invention is explained in more detail with reference to the following figures. They show:

[0042] Fig. 1 : a perspective view of a partially schematic embodiment of an ultrasonic measuring device according to the invention;

[0043] Fig. 2: a first cross-section through a first measuring section of the design of the measuring tube according to Fig. 1;

[0044] Fig. 3: a second cross-section through a second measuring section of the design of the measuring tube according to Fig. 1; and

[0045] Fig. 4: a partial section of the first cross-section through the measuring tube according to Fig. 1 .

[0046] Fig. 1 shows a perspective view of a partially schematic embodiment of an ultrasonic measuring device 10 according to the invention. The ultrasonic measuring device 10 shown comprises an embodiment of the measuring tube 1 according to the invention for guiding a medium. Fig. 2 shows a first cross-section Q1 through a first measuring section MA1 of the embodiment of the measuring tube 1 according to Fig. 1. Fig. 3 shows a second cross-section Q2 through a second measuring section of the embodiment of the measuring tube 2 according to Fig. 1. Fig. 4 shows a partial section of the first cross-section Q1 through the measuring tube 2 according to Fig. 1.

[0047] The measuring tube 1 for use in an ultrasonic measuring device 10 comprises a measuring tube body 2. The measuring tube body 2 can be made of a metal (e.g., (stainless) steel), a plastic, glass, a ceramic, and / or a glass fiber reinforced or otherwise filled plastic. The measuring tube body 2 is preferably metallic. The measuring tube body 2 includes a medium channel through which the medium to be examined is guided. The measuring tube body 2 also has an inner surface iMF in contact with the medium and an outer surface äMF that does not come into contact with the medium. The measuring tube body 2 preferably has a thickness of 0.4 to 3 millimeters, particularly 0.7 to 1.75 millimeters, and a nominal diameter of less than DN25, particularly less than DN15, and preferably DN8.

[0048] The measuring tube body 2 has a first and second measuring section MA1, MA2. A measuring section is a subsection of the measuring tube body 2 designed to accommodate transducer elements for generating the ultrasonic measuring device. The first and second measuring sections MA1, MA2 are located offset in the direction of flow. The measuring tube body 2 exhibits a measuring tube thickness deviation of less than ±3% from a target measuring tube thickness or from a mean measuring tube thickness in the first and second measuring sections MA1, MA2.

[0049] The measuring tube body 2 has a first measuring section contour MK1 in the first measuring section MA1, which is constant throughout the entire first measuring section MA1. The first measuring section contour MK1 can be the outer or inner line of the measuring tube body 2 in a first cross-section Q1. Furthermore, the measuring tube body 2 has a second measuring section contour MK2 in the second measuring section MA2, which is constant throughout the entire second measuring section MA2. The second measuring section contour MK2 can also be the outer or inner line of the measuring tube body 2 in a second cross-section Q2.

[0050] According to the invention, the first measuring section contour MK1 differs from the second measuring section contour MK2. That is, the first measuring section contour MK1 in the first cross-section Q1 assumes a shape (e.g. circular, angular, oval, etc.) that differs from the shape of the second measuring section contour MK1 in the second cross-section Q2.

[0051] The shape of the first measuring section contour MK1 and the second measuring section contour MK2 are, in principle, freely selectable within the degrees of freedom. For example, the first measuring section MK1 can have a hexagonal shape. This is feasible for measuring tubes with a nominal diameter larger than DN15. Further measuring sections can also be provided. For instance, a third and fourth measuring section can be offset from the first and second measuring sections in the flow direction.

[0052] Furthermore, the measuring tube body 2 has an inlet section EA and an outlet section AA. The measuring tube body 2 typically has a process connection (e.g., a flange, a threaded fitting, etc.) in both the inlet section EA and the outlet section AA, via which the ultrasonic flow meter 10 can be connected to a process line. The illustrated measuring tube body 2 has a circular inlet section contour EK and outlet section contour AK in both the inlet and outlet sections EA and AA, respectively. The inlet section contour EK and outlet section contour AK each have a (circular) basic shape. The two basic shapes can be identical, as shown. This can result from the fact that the measuring tube body 2 is formed from a (conventional) cylindrical outlet tube using a hydroforming process. No transducer elements are arranged in the inlet and outlet sections EA and AA.

[0053] The measuring tube body 2 has a first transition section ÜA1 between the inlet section EA and the first measuring section MA1. Within this transition section, the measuring tube body 2 assumes a second transition section contour ÜK2, which changes in the flow direction from the inlet contour until it reaches the first measuring section contour MK1. The second transition section contour ÜK2 can take the form of a superellipse. The first transition section ÜA1 has a minimum transition section length, which is chosen such that reflected ultrasonic waves (packets) do not superimpose the evaluation windows. The minimum transition length can be greater than or equal to N / 2 ■ 1.5 • Ida, where N = number of wave trains in the excitation signal and Ida = wavelength of the Lamb wave (e.g., Ida = 1.5 mm and N = 8). The same can apply to further transition sections.

[0054] The first and second measuring sections MA1 and MA2 are separated by a second transition section ÜA2. Within the second transition section ÜA2, the measuring tube body 2 assumes a first transition section contour ÜK1 that varies in the flow direction. This contour changes from the first measuring section contour MK1 in the flow direction until it assumes the second measuring section contour MK2. The first transition section contour ÜK1 can take the form of a superellipse.

[0055] Furthermore, the measuring tube body 2 has a third transition section ÜA3 between the outlet section AA and the second measuring section MA2, in which the measuring tube body 2 assumes a third transition section contour ÜK3 that changes in the flow direction, starting from the second measuring section contour MK2 until it assumes the outlet contour AK. The third transition section contour ÜK3 can assume the form of a superellipse.

[0056] The measuring tube body 2 can be manufactured using an internal high-pressure forming process (also called hydroforming) that meets the requirements of DIN 8584-7. For this purpose, a conventional hollow cylindrical tube suitable for internal high-pressure forming (= starting tube, e.g., a metal tube) can be formed into the final shape of the measuring tube body 2 by means of tensile-compressive forming. In this process, a liquid (usually a water-oil emulsion) is introduced into the tube under pressure, causing it to deform and assume the predetermined shape of the tool.

[0057] Further cost savings can be achieved if the ultrasonic measuring device requires internal surfaces with very high surface quality, or low roughness, due to its use in hygiene-relevant applications, particularly in the food industry. For this purpose, pre-polished tubes can be used, whose surface quality is only slightly affected by hydrostatic cold forming. This eliminates the need for a final, costly polishing process of the entire measuring tube 1, which is equipped with process connections.

[0058] In the first measuring section MA1, the measuring tube body has an (outer) planar first, second, and third surface PF1, PF2, and PF3. The first, second, and third surfaces PF1, PF2, and PF3 each have a width B perpendicular to the longitudinal axis of the measuring tube body 2 and a length L along the longitudinal axis of the measuring tube body 2. The longitudinal extent is greater than the transverse extent. In the first cross-section Q1, a first straight line G1 lying in the first planar surface PF1, a second straight line G2 lying in the second planar surface PF2, and a third straight line G3 lying in the third planar surface PF3 define a triangle, in particular an isosceles triangle. The first cross-section Q1 intersects the first measuring section MA1 through the measuring tube body 2. In the illustrated embodiment, the first, second and third surfaces PF1, PF2, PF3 are the only planar surfaces in the first measuring section MA1.

[0059] The first straight line G1 and the second straight line G2 form an angle α, where 20° < α < 32°, in particular 22° < α < 28°, and preferably 26°. The same applies to the first straight line G1 and the third straight line G3. The second straight line G2 and the third straight line G3 form an angle β, for which α = 180° - 2 • α. By choosing a triangle as the basic shape for the first measuring contour 1, a two-traverse transducer element arrangement can be realized, in which the ultrasonic waves passing through the medium are reflected once at the inner surface of the measuring tube body 2 before being received at the receiving ultrasonic transducer.

[0060] The width B must be between 2.7 and 3.3 millimeters, preferably B = 3 millimeters. The width B of the planar surfaces PF1, PF2, PF3 is selected such that it provides space for exactly one transducer element in the circumferential direction of the measuring tube body 2. The length L of the planar surfaces PF1, PF2, PF3 is preferably selected such that at least two transducer elements can be arranged offset along the longitudinal direction of the surface. The choice of width B also depends on the wall thickness. If the width is too small, the directivity decreases. If the width B is too large, the near field can become too long. As the wall thickness decreases, the wavelength, and thus the required minimum transducer width—and therefore also the minimum width B—scales downwards proportionally.

[0061] According to the illustrated embodiment, the measuring tube body 2 in the second measuring section MA2 has an (outer) planar fourth and fifth surface PF4, PF5. The second measuring section contour MK2 assumes an oval basic shape, which is designed such that the fourth and fifth surfaces PF4, PF5 run parallel to each other at least partially. The fourth and fifth surfaces PF4, PF5 are each configured to accommodate at least one transducer element.

[0062] The measuring tube 1 is designed in such a way that the first measuring section contour MK1, the second measuring section contour MK2 and the first transition contour ÜK are chosen so that it is self-emptying when the measuring tube 1, in particular the ultrasonic measuring device 10, is inclined at an inclination of < 3°, in particular at an inclination of 3°, relative to a horizontal.

[0063] Furthermore, the measuring tube body 2 can have a curvature with a radius of curvature R in the first cross-section Q1, in particular exactly three curvatures, each with a radius of curvature R. For the radius of curvature R, it holds that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters, and preferably R = 2.1 millimeters.

[0064] The self-draining capability of an ultrasonic measuring device 10 or a measuring tube 1 in general is an essential requirement, especially in hygienic applications. Furthermore, the hygiene standard ASME BPE, for example, requires that radii of curvature maintain a minimum radius of 3 millimeters. However, this is not feasible, particularly with measuring tubes 1 according to the invention, which have small nominal diameters and multiple planar surfaces intended for transducer elements. For example, the measuring tube body 2, with a nominal diameter of DN8 and an angle α of 26° in the first cross-section Q1, has a radius of curvature of approximately 2.1 millimeters. The angle α of 26° must be maintained to ensure a constant inner circumference (resulting in a constant wall thickness despite hydroforming) along the measuring tube body 2, while simultaneously allowing a transducer element with a width of 3 millimeters to be attached to the planar surfaces.However, by selectively choosing the individual contours, self-emptying can be achieved when the measuring tube 1 or the ultrasonic measuring device 10 is tilted.

[0065] Furthermore, the measuring tube body 2 can have a curvature with a radius of curvature R in the second cross-section Q2, in particular exactly two curvatures, each with a radius of curvature R. For the radius of curvature R, 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters, and preferably R = 2.84 millimeters.

[0066] The measuring tube body 2 has an inner first circumference U1 in the first measuring section MA1, an inner second circumference U2 in the second measuring section MA2, and an inner third circumference U3 in the inlet section EA. The shape of the measuring tube body is chosen such that the first, second, and third circumferences U1, U2, U3 do not deviate from each other by more than 3%, and in particular not by more than 1.5%. Furthermore, the measuring tube body 2 has an inner fourth circumference U4 in the second transition section ÜA2, which deviates from the first, second, and fourth circumferences U1, U2, U4 by no more than 3%, and in particular not by more than 1.5%. The illustrated configuration of the measuring tube body 2 has an (inner) circumference that is essentially constant along the entire measuring tube body. Essentially constant means that deviations from a mean circumference are no more than 3%, and in particular not by more than 1.5%.Provided that the first, second, and third circumferences U1, U2, and U3 are essentially identical, it can be ensured, particularly when using an internal high-pressure forming process, that the wall thickness of the measuring tube body 2 remains unchanged in the measurement-relevant areas of the measuring sections MA1 and MA2 after forming. This means that during forming, the total length of the respective measuring sections MA1 and MA2 is increased as much as possible and only slightly, without locally falling below the required minimum circumferential elongation. Thus, especially when using the measuring tube 1 in ultrasound-based measuring devices 10, robust ultrasound signals (e.g., in the form of Lamb waves) can be generated and evaluated.

[0067] The embodiment shown in Figures 1 to 4 comprises at least two pairs of ultrasonic transducers, in particular for generating and / or receiving surface acoustic waves, preferably Lamb waves. Each pair of ultrasonic transducers comprises two transducer elements, one of which is configured to generate an ultrasonic wave and the other to receive the generated ultrasonic wave that has passed through the medium or the measuring tube body. Alternatively, both transducer elements forming the pair of ultrasonic transducers can be configured to generate and receive ultrasonic waves, respectively. Furthermore, at least one transducer element of the pair of ultrasonic transducers can be configured to receive the ultrasonic wave from a transducer element not belonging to the pair.

[0068] It is known that measuring tube bodies inherently exhibit Lamb wave modes, namely mixed pressure and shear wave vibrations, in which the tube wall of the measuring tube body undergoes, or can undergo, Lamb wave-forming vibrations. In this process, the tube wall is deflected both radially and longitudinally along the measuring tube body 2. These Lamb waves can be either symmetrical (SO, S1, S2, ... Sn) or asymmetrical (AO, A1, A2, ... An). The generation and detection of Lamb wave modes is already prior art, as demonstrated, for example, in patents US6575043B1 and US4735095B.

[0069] The at least two pairs of ultrasonic transducers comprise a first pair of ultrasonic transducers – with a first and second transducer element W11, W12 – which is arranged in the first measuring section MA1. The first transducer element W11 is arranged on the second surface PF2, and the second transducer element W12 is arranged on the third surface PF3. Together, the first and second transducer elements W11, W12 form a two-crossbeam arrangement. This means that the ultrasonic wave generated, for example, by the first transducer element W11 and coupled into the medium or medium channel, is reflected once by the inner surface iMF of the measuring tube body 2 on its way to the second transducer element W21. The first surface PF2 is free of a transducer element. The inner surface PIF1, parallel to the first surface PF2 and also planar, in contact with the medium, is configured as a reflective surface.

[0070] Furthermore, the at least two pairs of ultrasonic transducers comprise a second pair of ultrasonic transducers – with a first and a second transducer element W21, W22 – which is arranged in the second measuring section MA2. The first transducer element W21 is arranged on the fourth surface PF4, and the second transducer element W22 is arranged on the fifth surface PF5. Because the fourth and fifth surfaces PF4, PF5 are parallel to each other, the first and second transducer elements W21, W22 together form a 1-crosshead arrangement. This means that an ultrasonic wave generated, for example, by the first transducer element W21 propagates directly to the second transducer element W22 without first changing its transmission direction, e.g., due to reflection at the inner surface of the measuring tube body 2.

[0071] The inventive design of the measuring tube 10 allows for measurement configurations, when the transducer elements are arranged on the planar surfaces provided for this purpose, in which the ultrasonic waves used to investigate the medium properties traverse measurement paths of varying lengths and are also exposed to different flow profile influences. This makes it possible to realize ultrasonic measuring devices with small nominal diameters that are suitable for applying correction algorithms such as those taught, for example, in DE 10 2024 117 335.1.

[0072] The measuring tube body 1 has a plane of symmetry SE in the first measuring section MA1. A central longitudinal axis of the measuring tube body 1 lies in the plane of symmetry SE. The measuring tube body 1 can also be designed such that the plane of symmetry SE describes the second measuring section MA2 in a mirror-symmetric manner. This measuring tube geometry offers the advantage that axial forces, for example induced by different thermal expansions between the measuring tube and the housing, can be absorbed more effectively without the measuring tube deforming laterally.

[0073] The first and second transducer elements W11 and W12 are each configured to generate ultrasonic waves whose principal axes HA1 and HA2 intersect the plane of symmetry SE. In other words, a signal path describing the main path of the propagating ultrasonic wave is deflected at the intersection of the inner surface of the measuring tube body 2 and the plane of symmetry due to reflection.

[0074] The at least two pairs of ultrasound transducers also include a third pair of ultrasound transducers.

[0075] - with a first and second transducer element W31, W32 - which is arranged in the first measuring section MA1. The first transducer element W31 is arranged on the third surface PF3 and the second transducer element W32 is arranged on the second surface PF2. The third pair of ultrasonic transducers is arranged such that a 2-crosshead arrangement is formed.

[0076] Fig. 2 shows a first cross-section Q1 through the first transducer element W11 of the first ultrasonic transducer pair and the first transducer element W31 of the third ultrasonic transducer pair. The first cross-section Q1 does not differ significantly from a cross-section through the second transducer element W12 of the first ultrasonic transducer pair and the second transducer element W32 of the third ultrasonic transducer pair.

[0077] Furthermore, the at least two ultrasound transducer pairs include a fourth ultrasound transducer pair.

[0078] - with a first and second transducer element W41, W42 - which is arranged in the second measuring section MA2. The first transducer element W41 is arranged on the fifth surface PF5 and the second transducer element W42 is arranged on the fourth surface PF4. The fourth pair of ultrasonic transducers is arranged such that a 1-transverse arrangement is formed.

[0079] Fig. 3 shows a second cross-section Q2 through the first transducer element W21 of the second ultrasonic transducer pair and the first transducer element W41 of the fourth ultrasonic transducer pair. The second cross-section Q2 does not differ significantly from a cross-section through the second transducer element W22 of the second ultrasonic transducer pair and the second transducer element W42 of the fourth ultrasonic transducer pair.

[0080] The transducer elements of the individual ultrasonic transducer pairs can be connected directly or indirectly to the measuring tube body 2. For example, so-called coupling elements can be provided, which are arranged between the transducer element and the measuring tube body 2 and are designed and configured such that a driver signal excites a Lamb wave in the measuring tube body 2. The driver signal is provided by measuring electronics 100, which are electrically connected to at least two ultrasonic transducer pairs, and in particular to all ultrasonic transducer pairs. The measuring electronics 100 are configured at least to determine the medium property as a function of at least one measured value per ultrasonic transducer pair. Furthermore, the measuring electronics 100 are configured to generate the driver signal and provide it to the corresponding transducer elements.The medium property can be a flow rate, a speed of sound, a density, a viscosity, or a quantity derived from the aforementioned medium properties.

[0081] Furthermore, a housing 30 is provided, which surrounds the at least two pairs of ultrasonic transducers and is designed to protect the transducer elements and, optionally, the measuring electronics 100 from environmental influences. The measuring electronics 100 can alternatively be arranged in a so-called transmitter housing (not shown), the interior of which is separate from the interior of the housing 30. The ultrasonic measuring device is a single measuring unit, not merely a combination of at least two ultrasonic measuring devices offset in the flow direction and differing in cross-sectional shapes within the measuring section.

[0082] The ultrasonic measuring device 10 has a measuring device principal axis MHA, which runs perpendicular to a measuring tube longitudinal axis MLA of the measuring tube 1. The measuring device principal axis MHA is the axis that—when the ultrasonic measuring device 10 is horizontally oriented—runs perpendicular to a horizontal and parallel to a direction of gravity. The measuring device principal axis MHA typically passes—if present—through a connector, a transmitter adapter, and / or a transmitter housing (not shown) or parallel to a transmitter housing longitudinal axis. The measuring device principal axis MHA can also, or alternatively, lie in a plane of symmetry of the housing 30.According to the advantageous embodiment, the measuring tube 1 is arranged in the housing 30 such that the plane of symmetry SE of the measuring tube body 2 intersects the main axis MHA of the measuring instrument 10 at an angle β, where the angle β is such that 50° < β < 70°, in particular 55° < β < 65°, and preferably β = 60°. The measuring tube body 2 is therefore tilted circumferentially by the angle β in the housing 30 and fixed in position. This described tilting of the measuring tube serves to ensure self-emptying at the smallest possible angle of inclination of the entire device (i.e., the ultrasonic measuring device) to the horizontal.

[0083] REFERENCE MARK LIST

[0084] Measuring tube 1

[0085] Measuring tube body 2

[0086] Case 30

[0087] Measuring electronics 100

[0088] Cross section Q1, Q2

[0089] Measuring section MA1, MA2

[0090] Measuring section contour MK1, MK2

[0091] Inlet section EA

[0092] Outlet section AA

[0093] Transition section ÜA1, ÜA2, ÜA3

[0094] Measuring section MA1, MA2 planar surface PF1, PF2, PF3, PF4, PF5

[0095] Straight G1, G2, G3

[0096] Scope U1, U2, U3, U4

[0097] Converter element W11, W12, W21, W22 planar inner surface PIF1, PIF2, PIF3, PIF4, PIF5 inner lateral surface iMF

[0098] Plane of symmetry SE

[0099] Main axis HA1, HA2, HA3, HA4, HA5

[0100] Width B

[0101] MHA

Claims

PATENT CLAIMS 1. Measuring tube (1) for use in an ultrasonic measuring device (10), comprising: - a measuring tube body (2), wherein the measuring tube body (2) has a first and second measuring section (MA1, MA2), wherein the measuring tube body (2) has a first measuring section contour (MK1) in the first measuring section (MA1), wherein the measuring tube body (2) has a second measuring section contour (MK2) in the second measuring section (MA2), wherein the first measuring section contour (MK1) differs from the second measuring section contour (MK2), wherein the measuring tube body (2) has an inlet section (EA) and an outlet section (AA), wherein the measuring tube body (2) has a first transition section (ÜA1) between the inlet section (EA) and the first measuring section (MA1), wherein the first and second measuring sections (MA1, MA2) are separated by a second transition section (ÜA2), wherein a first transition section contour (ÜK1) changes from the first measuring section contour (MK1) in the flow direction until it meets the second assumes measuring section contour (MK2),wherein the measuring tube body (2) has a third transition section (ÜA3) between the outlet section (AA) and the second measuring section (MA2).

2. Measuring tube according to claim 1, wherein the measuring tube body (2) in the first measuring section (MA1) has an (outer) planar first, second and third surface (PF1 , PF2, PF3), wherein in a first cross-section (Q1) through the measuring tube body (2) in the first measuring section (MA1) a first straight line (G1) lying in the first planar surface (PF1), a second straight line (G2) lying in the second planar surface (PF2) and a third straight line (G3) lying in the third planar surface (PF3) span a triangle, in particular an isosceles triangle.

3. Measuring tube according to claim 1 or 2, wherein in the first cross-section (Q1) the first straight line (G1) and the second straight line (G2) span an angle α, with 20° < α < 32°, in particular 22° < α < 28° and preferably 26°.

4. Measuring tube according to claim 2 or 3, wherein the first, second and / or third surface (each) has a width B, wherein the width B is such that 2.7 < B < 3.3 millimeters, in particular B = 3 millimeters.

5. Measuring tube according to one of the preceding claims, wherein the measuring tube body (2) in the second measuring section (MA2) has an (outer) planar fourth and fifth surface (PF4, PF5), wherein the second measuring section contour (MK2) assumes an oval basic shape which is designed such that the fourth and fifth surfaces (PF4, PF5) run parallel to each other at least section by section.

6. Measuring tube according to one of the preceding claims, wherein the measuring tube body (2) has an inlet section contour (EK) in the inlet section (EA), wherein the inlet section contour (EK) assumes a (circular) round basic shape, wherein the measuring tube body (2) has an outlet section contour (AK) in the outlet section (AA), wherein the outlet section contour (AK) assumes a (circular) round basic shape, wherein the inlet section contour (EK) and the outlet section contour (AK) are identical.

7. Measuring tube according to one of the preceding claims, wherein the measuring tube (1) is designed such that it is self-emptying at an inclination of < 3°, in particular at least at an inclination of 3°, relative to a horizontal.

8. Measuring tube according to one of the preceding claims, wherein the measuring tube body in the first cross-section (Q1) has a curvature with a radius of curvature R, in particular exactly three curvatures, each with a radius of curvature R, wherein for the radius of curvature R it holds that 1 < R < 4 millimeters, in particular 2 < R < 3 millimeters and preferably R = 2.1 millimeters.

9. Measuring tube according to one of the preceding claims, wherein the measuring tube body (2) has an inner first circumference (U1) in the first measuring section (MA1), wherein the measuring tube body (2) has an inner second circumference (U2) in the second measuring section (MA2), wherein the measuring tube body (2) has an inner third circumference (U3) in the inlet section (EA), wherein the first, second and third circumferences (U1, U2, U3) do not deviate from each other by more than 3%, in particular not by more than 1.5%.

10. Measuring tube according to claim 9, wherein the measuring tube body (2) has an inner fourth circumference (U4) in the second transition section (ÜA2), wherein the first, second and fourth circumferences (U1 , U2, U4) do not differ from each other by more than 3%, in particular not by more than 1.5%.

11. Ultrasonic measuring device (10) for determining a medium property, comprising: - a measuring tube (1), in particular produced by means of a hydroforming process, according to one of the preceding claims, wherein the measuring tube (1) is configured to carry a medium; - at least two pairs of ultrasonic transducers, in particular for generating and / or receiving acoustic surface waves, preferably Lamb waves, wherein the at least two pairs of ultrasonic transducers comprise a first pair of ultrasonic transducers arranged in the first measuring section (MA1), wherein the first pair of ultrasonic transducers has a first and second transducer element (W11, W12), wherein the first transducer element (W11) is arranged on the second surface (PF2), wherein the second transducer element (W12) is arranged on the third surface (PF3), wherein the first and second transducer elements (W11, W12) form a 2-crossbeam arrangement, wherein the at least two pairs of ultrasonic transducers comprise a second pair of ultrasonic transducers arranged in the second measuring section (MA2), wherein the second pair of ultrasonic transducers has a first and a second transducer element (W21, W22), wherein the first transducer element (W21) is arranged on the fourth surface (PF4),wherein the second transducer element (W22) is arranged on the fifth surface (PF5), wherein the first and second transducer elements (W21 , W22) form a 1-crossbeam arrangement; - a measuring electronics (100) which is electrically connected to the at least two pairs of ultrasonic transducers, wherein the measuring electronics (100) is configured to determine the medium property as a function of at least one measured value per pair of ultrasonic transducers; and - a housing (30) wherein the housing (30) surrounds the at least two pairs of ultrasonic transducers.

12. Ultrasound measuring device according to claim 11, wherein the at least two pairs of ultrasound transducers comprise a third pair of ultrasound transducers which is arranged in the second measuring section (MA2), wherein the transducer elements of the third ultrasound transducer form a 1-crossbeam arrangement, wherein the at least two pairs of ultrasound transducers comprise a fourth pair of ultrasound transducers which is arranged in the first measuring section (MA1), wherein the transducer elements of the fourth ultrasound transducer form a 2-crossbeam arrangement.

13. Ultrasonic measuring device according to claim 11 or 12, wherein the transducer elements (W11 , W12, W21 , W22) are each configured to couple ultrasonic waves into the medium, wherein the measuring tube body (1) has an inner lateral surface (iMF) which in the first measuring section (MA1) has a planar and parallel inner surface (PIF1, PIF2, PIF3) corresponding to the first, second and third surfaces (PF1, PF2, PF3), wherein the inner lateral surface (iMF) in the second measuring section (MA2) has a planar and parallel inner surface (PIF4, PIF5) corresponding to the fourth and fifth surfaces (PF4, PF5), wherein the transducer elements (W11, W12, W21, W22) are each arranged on the measuring tube (1) such that a principal axis (HA1, HA2, HA3, HA4) of the coupling ultrasonic wave intersects at least one of the inner surfaces (PIF1, PIF2, PIF3, PIF4, PIF5) or a principal axis of the respective transducer elements (W11, W12, W21, W22) intersects at least one of the intersects the inner surfaces (PIF1 , PIF2, PIF3, PIF4, PIF5) orthogonally.

14. Ultrasonic measuring device according to claim 13, wherein the measuring tube body (1) has a plane of symmetry (SE) in the first measuring section (MA1), wherein the respective principal axes (HA1 , HA2) of the ultrasonic waves generated by means of the first and second transducer element (W11 , W12) intersect in the plane of symmetry (SE).

15. Ultrasonic measuring device according to claim 12, wherein the measuring tube body (1) has a plane of symmetry (SE) in the first measuring section (MA1), wherein the ultrasonic measuring device (10) has a measuring instrument principal axis (MHA) which is perpendicular to a measuring tube longitudinal axis of the measuring tube (1), wherein the measuring tube (1) is arranged in the housing (30) such that the measuring instrument principal axis (MHA) intersects the plane of symmetry (SE) at an angle β, wherein the angle β is such that 50° < β < 70°, in particular 55° < β < 65° and preferably β = 60°.

Images