Flowmeter using ultrasound

Abstract

The invention relates to an ultrasonic flowmeter (1) comprising a measuring tube (10), through which a flow chamber (11) extends and through the latter a flow medium can flow in at least one flow direction along a longitudinal axis (L), wherein a first ultrasonic transducer (12) is set up at a first position (I) and at least one second ultrasonic transducer (13) or at least one reflection surface is set up at a second position (II) in order to emit an ultrasonic wave (14) into the flow chamber (11) and to receive the emitted ultrasonic wave (14) from the relevant other ultrasonic transducer (12, 13) or the reflection surface again so as to form an ultrasonic propagation path, and wherein an inner wall segment (15) is set up in the measuring tube (10), the emitted ultrasonic wave (14) impinging on and reflecting off said inner wall segment. According to the invention, the inner wall segment (15) has a diffraction structure (16), at which the emitted ultrasonic wave (14) can be diffracted, thereby generating at least one diffraction maximum (B). The invention furthermore relates to a method for operating such an ultrasonic flowmeter (1).

Description

[0001] Kassel, November 20, 2025

[0002] Lawyer's file SIK24167P1WO

[0003] Official file number

[0004] NN

[0005] Applicant:

[0006] SIKA Dr. Siebert & Kühn GmbH & Co. KG

[0007] Struthweg 7-9

[0008] 34260 Kaufungen, Germany

[0009] Representative:

[0010] WALTHER PATENT

[0011] Walther ■ Bayer ■ Faber Heimradstraße 2 34130 Kassel, DE

[0012] FLOW METER WITH THE

[0013] USE OF ULTRASOUND

[0014] The invention relates to an ultrasonic flow meter with a measuring tube through which a flow chamber extends and which can be permeated by a flow medium in at least one flow direction along a longitudinal axis, wherein a first ultrasonic transducer is arranged at a first position and at least one second ultrasonic transducer or at least one reflective surface is arranged at a second position to emit an ultrasonic wave into the flow chamber and to receive the emitted ultrasonic wave from the other ultrasonic transducer or the reflective surface, forming an ultrasonic propagation path, and wherein an inner wall segment is arranged in the measuring tube at which the emitted ultrasonic wave strikes and is reflected. The invention further relates to a method for operating such an ultrasonic flow meter. PRINCIPAL ART

[0015] From DE 10 2006 019 146 B3, an ultrasonic flow meter is known, comprising a measuring tube through which a flow chamber extends, through which a fluid flows. A first ultrasonic transducer at a first position and a second ultrasonic transducer at a second position are configured to emit an ultrasonic wave into the flow chamber and to receive the emitted ultrasonic wave from the other transducer. The ultrasonic sensors are arranged at an angle on the outside of the measuring tube to generate the oblique propagation of the ultrasonic wave through the measuring tube. The ultrasonic wave can be emitted by the first ultrasonic transducer and received by the second ultrasonic transducer, and vice versa.If a fluid flows along its longitudinal axis through the flow chamber of the measuring tube, the fluid carries the ultrasound wave to the receiving ultrasound transducer faster than if the sound propagates against the flow direction. The resulting time-of-flight differences can be evaluated by electronics to determine the flow velocity of the fluid within the flow chamber of the measuring tube.

[0016] The flow meter described above is a so-called clamp-on ultrasonic flow meter. This means that the ultrasonic transducers are mounted on the outside of the measuring tube. Coupling wedges are used to transfer the sound energy into the tube wall and from there into the flow medium. However, this design is associated with increased losses and inaccuracies compared to direct contact between the transducers and the flow medium due to the multiple material transitions along the ultrasonic path. In contrast, when considering an ultrasonic flow meter with direct contact between the sound-emitting surfaces of the ultrasonic transducers and the flow medium—that is, with the ultrasonic transducers mounted inside the measuring tube—the arrangement of the transducers and reflectors presents a challenge. For example, if the transducers are to be...As in DE 10 2006 019 146 B3, to create a V-shaped sound path, the ultrasonic transducers must be arranged at an angle to the longitudinal axis in the measuring tube. Disadvantageously, this creates a dead space volume for the flowing medium in front of the sound-emitting surfaces of the ultrasonic transducers, to the side of the actual flow diameter.

[0017] EP 3 800 448 B1 discloses a further embodiment of an ultrasonic flow meter, comprising a measuring tube through which a flow chamber extends, through which a flow medium can flow, wherein a first ultrasonic transducer at a first position and a second ultrasonic transducer at a second position are arranged such that a W-shaped wave propagation of the ultrasonic wave is generated between the ultrasonic transducers. To influence the propagation of the ultrasonic wave in the flow channel, a flow limiting element is provided, which is arranged between two of a total of three reflectors;wherein the flow limiting element comprises a first wedge with a first inclined surface, and wherein a first wedge has a first plurality of teeth projecting from the first inclined surface, wherein the flow channel has an outlet opening, and wherein the flow channel comprises an inlet opening, the inlet opening being arranged opposite the outlet opening and a fluid path extending from the inlet opening to the outlet opening, wherein the three reflectors comprise a first reflector, the first reflector being arranged among the three reflectors closest to the outlet opening;wherein the three reflectors comprise a second reflector, the second reflector being positioned closest to the inlet opening among the three reflectors, the flow restrictor being inserted between the first and second reflectors, the flow channel having a fourth wedge with a fourth inclined surface, the fourth wedge having at least one tooth projecting from the fourth inclined surface, and the fourth wedge being positioned between the second reflector and the inlet opening. The remaining flow cross-section is significantly narrowed, primarily by the flow restrictor, resulting in pressure losses in the flow meter.

[0018] EP 1 096 236 A2 and DE 39 41 544 A1 disclose ultrasonic flow meters with ultrasound emission into the flow chamber at an angle to the longitudinal axis. The sound waves can be transmitted directly into the flow medium, but this disadvantageously creates dead zones in front of the ultrasonic transducers, which negatively affect the flow of the medium.

[0019] REVELATION OF THE INVENTION

[0020] The object of the present invention is therefore to create an ultrasonic flow meter that can be easily constructed and that enables the smallest possible flow resistance for the flow medium flowing through the measuring tube, without creating large dead water areas.

[0021] This problem is solved starting from an ultrasonic flow meter according to the preamble of claim 1 and starting from a method according to claim 13 in conjunction with the respective characterizing features. Advantageous embodiments of the invention are specified in the dependent claims. With regard to the ultrasonic flow meter, the invention includes the technical teaching that the inner wall segment has a diffraction structure at which the incident ultrasonic wave can be diffracted by generating at least one diffraction maximum.

[0022] The core concept of the invention is the use of a diffraction structure such that the reflection of the ultrasound wave by the diffraction structure produces an effect as if the ultrasound transducer were arranged obliquely on the measuring tube, or as if an angled mirror were arranged in the inner wall of the measuring tube, allowing the ultrasound wave to reflect at an angle. The invention thus takes advantage of the fact that, with a macroscopically flat structure of the inner wall segment in the measuring tube, an angled reflection can be created solely by means of a microscopic diffraction structure incorporated into the inner wall segment, without the microstructure having any influence on the flow resistance. For example, the microstructure has dimensions of less than 1 mm on the inner wall segment, while the measuring tube has a flow chamber with a diameter of 20 mm.Therefore, the inner wall segment with the diffraction structure has no significant or technically relevant influence on the flow behavior of the fluid medium.

[0023] Diffraction occurs when structures exposed to a wave, such as an ultrasound wave, have wavelengths on the order of the wavelength. The wavelength A of a wave can be determined by the equation A = c / f, where c is the propagation speed of the wave in the medium and f is the frequency of the ultrasound wave. The lattice constant of the desired microstructure can then be calculated using the wavelength. When a plane wave encounters a slit whose width is close to the wavelength, diffraction occurs behind it. In this phenomenon, the wave components reinforce and weaken each other through constructive and destructive interference at specific angles that depend on the width of the slit and the wavelength. This results in a diffraction pattern with a central intensity maximum and decreasing secondary maxima around it.In a diffraction grating with multiple slits, primary diffraction maxima form at fixed angles. Smaller secondary maxima also develop around these primary maxima. If the slit width were infinitely small, the amplitude of the primary maxima would be the same at all angles. However, since the slits have a certain width, the effect of a single slit is superimposed, and the amplitude of the maxima is bounded by an envelope curve. If the slits, or more generally the diffraction elements of the diffraction pattern, are laterally symmetric, the envelope curve is also symmetric. The same applies to asymmetry.

[0024] The inner wall segment with the diffraction structure described above forms a reflection grating. In this grating, diffraction occurs through reflection at a periodic structure, equivalent to a multiple slit. During reflection, the incident wave is diffracted into different orders, which is advantageous compared to a transmission grating because the latter does not incur transmission losses. If, instead of directing the majority of the wave's energy to the zeroth diffraction order in a reflection grating, a reflection-phase grating with preferential reflection can be used. This is also known as a blaze grating. The term "phase grating" means that, instead of varying the amplitude as in a multiple-slit grating, the phase of the wave is varied by the grating. In the case of the blaze grating, this is achieved through a sawtooth-like structure and the resulting periodically varying path length for the wave.The embodiments that are advantageous according to the invention are described in more detail below as further features of the invention.

[0025] Regarding the first diffraction order, the following can be assumed: When a sound wave strikes objects where only zeroth-order diffraction occurs, the sound waves behave as in a normal geometric reflection. However, if a higher diffraction maximum of m = 1 or higher occurs (likewise m = -1 or lower), the type and direction of wave propagation differ from that observed in a simple reflection. The term "diffraction" therefore usually refers to these latter phenomena. For this reason, in this document, phrases such as "at least one diffraction maximum" mean at least one diffraction maximum other than the first diffraction order (e.g., m = 1).

[0026] The measuring tube can be manufactured from either metal or plastic, incorporating plastic diffraction elements. A coating on these elements can achieve high reflectivity. Various coating processes can be used, such as electroplating, sputtering, or vapor deposition. Suitable coating materials include metals, ceramics, and DLCs.

[0027] The diffraction pattern features diffraction elements that are periodically repeating along a longitudinal axis of the measuring tube. The inner wall segment can be formed as a single piece, materially identical to the measuring tube itself, thus forming part of the inner wall of the measuring tube, or the inner wall segment can be designed as a separate element and applied to the inside of the measuring tube. The diffraction elements themselves can also be formed as a structure on the inner surface of the measuring tube, or they can be located on the surface of a replaceable inner wall segment that is inserted into the measuring tube as a separate component. Alternatively, the inner wall segment with the diffraction pattern can be manufactured or produced as part of the inner surface of the measuring tube by machining, etching, or stamping processes, or directly during the manufacturing of the measuring tube using injection molding.

[0028] The periodic repetition of the diffraction elements is designed such that they repeat periodically along the longitudinal axis and have a transverse extension, thus forming a segment of the otherwise circular flow space. However, it is also conceivable that the diffraction elements extend with the internal curvature within the flow space, for example, by forming a corrugated or prism structure that either forms a flat surface or is shaped like a trough on the inside of the flow space. In particular, the periodic repetition in the present example measuring tube can be mirrored from the center of the tube.

[0029] To achieve the effect of a one-sided diffraction maximum, extending at an angle to one side relative to the ultrasound wave directed perpendicularly onto the diffraction structure, the diffraction structure incorporates diffraction elements with an asymmetric, particularly triangular, groove profile and / or a blaze grating or a step-shaped reflection phase grating. The triangular groove profile itself can form a blaze grating, and the elements of the profile can be asymmetrically designed.

[0030] It should be noted that, in principle, it is also conceivable that the triangular elements could be symmetrical. However, the envelope of the diffraction maxima would then have an equally large maximum on both sides, which would be less efficient because the same amount of energy would be reflected on both sides of the grating. With an asymmetrical structure, the maximum on one desired side is larger, resulting in a greater proportion of usable energy for signal acquisition.

[0031] Such grating structures enable the symmetrical or asymmetrical reflection of the ultrasound wave with an enhanced lateral diffraction maximum that can extend at an angle to the perpendicular. If the ultrasound transducers transmit the ultrasound wave perpendicularly onto the diffraction structure, the reflected sound wave can propagate away from the diffraction structure at an angle, resulting, for example, in a W-shaped sound wave propagation pattern between the two ultrasound transducers mounted at an angle to each other in the measuring tube. It has been shown that not only a triangular groove profile, particularly in the form of a blaze grating, enables such enhanced lateral diffraction with a diffraction maximum, but also a step-shaped reflection phase grating.

[0032] The first and second ultrasonic transducers are designed to generate an ultrasonic wave with a defined wavelength, whereby the periodically repeating, triangular groove profile has principal dimensions that lie in the range of the wavelength. These principal dimensions relate, for example, to the grating constant (i.e., the spacing within which the periodic structure repeats), the height of the groove profile, and / or the widths of the groove profile's flanks, with the grating constant being the crucial dimension.

[0033] Thus, one of the flanks of the triangular groove profile Is, relative to the longitudinal axis of the measuring tube, can have an angle which, relative to the wavelength in the flow medium used, corresponds to half the diffraction angle of one of the diffraction orders of the grating structure. This is how the desired effect of the blaze grating can be created and utilized according to the invention. This same flank can be made longer than the other flank to increase the efficiency of the reflection, thereby exploiting an asymmetry.

[0034] The first and second ultrasonic transducers are arranged in conjunction with the measuring tube such that they are diametrically opposite the arrangement of the diffraction structure, allowing the ultrasonic wave to be transmitted perpendicularly to the diffraction structure. This offers the advantage that the ultrasonic transducers, with their acoustically active surface, can form part of the inner flow wall of the flow chamber without creating dead zones. Furthermore, the perpendicular incidence of the ultrasonic wave on the diffraction structure allows the diffraction maximum to be generated through usable diffraction effects, creating the W-shaped path of the ultrasonic wave between the first and second ultrasonic transducers.

[0035] The ultrasonic transducers, or rather their sound emission surfaces, can have a curved surface shape corresponding to the inner wall of the pipe. This can further reduce the potential flow resistance, since the inner wall of the pipe essentially retains a cylindrical flow resistance despite the inserted inner wall segment with the diffraction structure.

[0036] In addition to direct contact with the pipe interior, the ultrasonic transducers can also be positioned externally on or within the pipe wall to further reduce potential flow resistance, as the ultrasonic wave can penetrate the wall of the measuring tube. The path of the ultrasonic wave between the first and second transducers can thus exhibit a W-shape, formed by two outer sound wave paths perpendicular to the surface and two diffraction maxima at a diffraction angle. These diffraction maxima reflect off an intermediate surface opposite the diffraction pattern. This intermediate surface is located between the two ultrasonic transducers and therefore lies in the plane of symmetry of the W-shaped sound wave path.

[0037] In addition to the aforementioned sound paths in a common plane, other sound paths are conceivable that do not necessarily have to lie in a plane. For example, it is possible to achieve approximately helical sound paths by tilting the diffraction structure in combination with a spatially adapted arrangement of the diffraction elements and the ultrasound transducers.

[0038] For example, when water flows through the ultrasonic flow meter, it can emit and / or receive an ultrasonic wave with a frequency of 0.5 MHz to 10 MHz, 1 MHz to 5 MHz, 1.5 MHz to 3 MHz, and / or 2.1 MHz, with 1 MHz being a particularly important possible frequency. Analogous to the above ratio A = c / f, the main dimensions of the triangular groove profile can have a grid constant of 0.16 mm to 5.93 mm, 0.5 mm to 4 mm, 0.5 mm to 2 mm, 0.7 mm to 1 mm, and / or 0.92 mm. The triangular groove profile can have a height of 0.02 mm to 4.2 mm and / or 0.1 mm to 1 mm and / or 0.2 mm to 0.5 mm and / or 0.28 mm.The flank of the groove profile located on the side onto which the ultrasound wave is to be reflected can have a flank angle of 0° to 45° and / or a flank angle of 20° to 30° and / or a flank angle of 25° relative to the longitudinal axis of the measuring tube, and / or the flank not located on the side onto which the ultrasound wave is to be reflected can have a flank angle of 0° to 90° and / or of 30° to 50° and / or of 40°.

[0039] To adapt the ultrasonic flow meter to changes in the acoustic properties of the medium, which can occur, for example, due to temperature changes, the frequency of the emitted ultrasound can be adjusted. Therefore, the ultrasonic transducers can be designed to generate different frequencies. While the transducers are primarily intended for generating a specific frequency, this frequency can also be varied within a certain range around that frequency, albeit with some signal loss.

[0040] The object of the invention is further achieved by a method for operating an ultrasonic flow meter, comprising a measuring tube through which a flow chamber extends and which is permeated by a flow medium in at least one flow direction along a longitudinal axis, wherein a first ultrasonic transducer is arranged at a first position and at least one second ultrasonic transducer or at least one reflective surface is arranged at a second position, which emit an ultrasonic wave into the flow chamber and wherein the emitted ultrasonic wave is received by the respective other ultrasonic transducer or the reflective surface forming an ultrasonic propagation path, and wherein an inner wall segment is arranged in the measuring tube at which the emitted ultrasonic wave strikes and is reflected, wherein the method provides at least the following further steps: designing the inner wall segment as a diffraction structure;Sending the ultrasound wave onto the diffraction structure and generating at least one diffraction maximum due to diffraction occurring at the diffraction structure.

[0041] In particular, the ultrasound wave is sent from a perpendicular direction onto the diffraction structure, whereby the emitted ultrasound wave is reflected at the diffraction structure and reflected at an angle to the perpendicular direction predominantly towards the diffraction maximum.

[0042] The diffraction pattern can also be formed locally opposite the two ultrasonic transducers on the inner surface of the flow chamber, particularly if the transducers emit an ultrasonic wave perpendicularly, so that it strikes the opposite position in the flow chamber. In this respect, it would also be sufficient to insert two inner wall segments with the diffraction pattern of smaller dimensions opposite each other into the measuring tube, so that the intermediate surface on the side between the two ultrasonic transducers also only requires a finite extent. Then the W-shaped propagation of the ultrasonic wave between the two ultrasonic transducers can be generated.

[0043] PREFERRED EXAMPLE OF THE INVENTION

[0044] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show:

[0045] Figure 1 shows a schematic representation of the measuring tube with the flow chamber and the two ultrasound transducers arranged on the measuring tube, with the propagation of the ultrasound wave in a W-shape shown as an example.

[0046] Figure 2 shows detail X according to Figure 1 in an enlarged view.

[0047] Figure 3 shows a schematic representation of the reflection of the ultrasound wave from the perpendicular towards a lateral diffraction maximum and

[0048] Figure 4 shows a schematic view of a step-shaped reflection phase grating.

[0049] Figure 1 shows a cross-sectional view through a flow meter 1 according to the invention and for measuring the flow velocity of a fluid through a measuring tube 10, into which a flow chamber 11 is provided through which the fluid flows. Ultrasound is used for this purpose, for which a first ultrasonic transducer 12 and a second ultrasonic transducer 13 are arranged in the measuring tube 10. The first ultrasonic transducer 12 is located at position I, and downstream, the second ultrasonic transducer 13 is located at position II. The two positions I and II for the arrangement of the ultrasonic transducers 12 and 13 are arranged one after the other in the direction of flow, with respect to the longitudinal axis L of the measuring tube 10.

[0050] The ultrasonic transducers 12 and 13 are designed to emit and receive an ultrasonic wave 14. When the measuring tube 10 is filled with the flowing medium, the ultrasonic wave 14 travels in the direction of flow with a shorter transit time than when the ultrasonic wave 14 is transmitted from the rear ultrasonic transducer 13 against the flow direction to the front ultrasonic transducer 12. From this difference in transit time, the flow velocity of the flowing medium can be determined using measuring electronics (not shown). The flowing medium can be a hydraulic fluid or a thermal fluid.

[0051] The ultrasonic transducers 12, 13 are arranged in a straight, non-tilted configuration within the measuring tube 10, so that the emitted ultrasonic wave 14 can strike the opposite side in the flow chamber 11 perpendicularly. This achieves the advantage that no geometric interruption is created within the measuring tube 10 for the flow medium in the flow chamber 11. The propagation of the ultrasonic wave 14 between the first ultrasonic transducer 12 and the second ultrasonic transducer 13 nevertheless follows a W-shaped path, with the ultrasonic wave 14 being reflected on the opposite side by an inner wall segment 15, and an intermediate reflection occurring at an intermediate surface 21.

[0052] To achieve the W-shaped propagation effect of the ultrasound wave 14 between the two ultrasound transducers 12, 13, the inner wall segment 15 is designed with a diffraction structure 16 according to the invention. The ultrasound wave 14 emitted perpendicular to this structure can be diffracted by generating at least one diffraction maximum B. This occurs at the two reflection areas opposite the ultrasound transducers 12, 13 on the diffraction structure 16. In contrast, for reflection at the intermediate surface 21, it is sufficient that a simple specular reflection occurs, following the principle "angle of incidence equals angle of reflection".

[0053] Figure 2 shows an enlarged view of detail X according to Figure 1. Detail X shows the diffraction structure 16 consisting of the periodically repeating diffraction elements 18. The diffraction elements 18 have an asymmetrical, triangular groove profile 19, and the groove profile 19 obtains its asymmetry from a broad flank 19.1 and an adjoining narrow flank 19.2. The two flanks of the groove profile 19 have a width that forms the so-called grating constant 17 and each forms a roof edge of height h.

[0054] The broad flank 19.1 and the narrow flank 19.2 each have flank angles oc1 and a2, which are shown plotted in Figure 2. When an ultrasonic wave strikes the diffraction structure 16 from the perpendicular, a lateral diffraction maximum is formed, as shown in more detail below in conjunction with Figure 3.

[0055] The wide flank 19.1 and the narrow flank 19.2 can be designed such that their spatial extent in the direction of the longitudinal axis L of the measuring tube 10 is smaller than the sound wavelength A used due to the selected sound frequency.

[0056] Figure 3 shows the diffraction elements 18 in their periodic sequence, wherein the diffraction elements 18 form triangular groove profiles 19 with broad flanks 19.1 and narrow flanks 19.2. The grating constant 17 and the height h are also shown.

[0057] When the ultrasound wave 14 encounters the periodically repeating structure of the successive diffraction elements 18, the schematically depicted diffraction maximum B is formed, whereby the intensity of the sound wave emitted at the diffraction angle y depends in particular on the flank angle a1. This is the case because the aforementioned envelope of the diffraction maxima itself has a maximum at an angle to the perpendicular S that depends on al. Advantageously, the grating constant 17 is chosen such that the diffraction angle y corresponds to the angle 2*a1 of specular reflection. Indirectly, however, the intensity of the considered diffraction maximum also depends on the flank angle a2, since this determines both the length of the flank 19.1 and the height h of the diffraction element.

[0058] For example, the ultrasonic wave 14 can have a frequency of 2.1 MHz, with the dimensions according to the illustration in Figure 3, i.e., in particular the widths of the flanks 19.1, 19.2, as well as the grating constant 17 and also the height h of the diffraction elements, corresponding approximately to the wavelength of the ultrasonic wave 14 in water. Thus, the grating constant can be, for example, 0.92 mm, while the height of the groove profile 19 is, for example, 0.28 mm.

[0059] To enable the sound to be focused on the receiving ultrasound transducer, the described dimensions and angles of the diffraction elements can be changed along the longitudinal axis so that they are adapted to the emission angle or incidence angle.

[0060] Figure 4 shows an alternative embodiment of the diffraction structure 16 as a step-shaped reflection phase grating 20. If an ultrasonic wave 14 with wavelength X is transmitted to or projected onto the phase grating 20, and the grating has a height of 1 / 4 of wavelength X, a lateral diffraction maximum B can also be achieved with such a grating structure 20. This lateral diffraction maximum has a higher intensity than the vertically reflected wave, which is largely canceled out by destructive interference, even if the ultrasonic wave 14 is transmitted to the phase grating 20 from the perpendicular direction S. The crucial point is that the lateral diffraction maxima are stronger than the vertically reflected wave, meaning that the energy is "redirected" into the latter. Therefore, a step-shaped reflection phase grating 20 can also serve as an embodiment of the inner wall segment 15 according to the invention.

[0061] The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of

[0062] Variants are conceivable that utilize the presented solution even in fundamentally different designs. All features and / or advantages arising from the claims, the description, or the drawings, including constructive details or spatial arrangements, can be essential to the invention, both individually and in various combinations.

[0063] Reference symbol list:

[0064] I Flow meter

[0065] 10 measuring tube

[0066] II Flow space

[0067] 12 first ultrasound transducer

[0068] 13 second ultrasound transducer

[0069] 14 Ultrasound wave

[0070] 15 Interior wall segment

[0071] 16 Diffraction structure

[0072] 17 Lattice constant

[0073] 18 Diffraction element

[0074] 19 triangular furrow profile

[0075] 19.1 wider flank

[0076] 19.2 narrow flank

[0077] 20 reflection phase gratings

[0078] 21 Intermediate surface al Flank angle of the broad flank a2 Flank angle of the narrow flank

[0079] X wavelength y diffraction angle h height

[0080] S Perpendicular

[0081] B Diffraction maximum

[0082] L Longitudinal axis

[0083] X Detail

[0084] I first position

[0085] II second position

Claims

Claims:

1. Ultrasonic flow meter (1) with a measuring tube (10) through which a flow chamber (11) extends and which can be permeated by a flow medium in at least one flow direction along a longitudinal axis (L), wherein a first ultrasonic transducer (12) is arranged at a first position (I) and at least one second ultrasonic transducer (13) or at least one reflective surface is arranged at a second position (II) to emit an ultrasonic wave (14) into the flow chamber (11) and to receive the emitted ultrasonic wave (14) from the respective other ultrasonic transducer (12, 13) or the reflective surface, forming an ultrasonic propagation path, and wherein an inner wall segment (15) is arranged in the measuring tube (10) at which the emitted ultrasonic wave (14) strikes and is reflected, characterized in that the inner wall segment (15) has a diffraction structure (16),where the emitted ultrasound wave (14) is diffractable, generating at least one diffraction maximum (B).

2. Ultrasonic flow meter (1 ) according to claim 1 , characterized in that the diffraction structure (16) has diffraction elements (18) which are formed in a periodically repeating manner along a longitudinal axis (L) of the measuring tube (10).

3. Ultrasonic flow meter (1) according to claim 2, characterized in that that the diffraction elements (18) have a symmetrical or asymmetrical and / or triangular groove profile (19) and / or a blaze grating or a step-shaped reflection phase grating (20).

4. Ultrasonic flow meter (1 ) according to one of claims 1 to 3, characterized in that the first and second ultrasonic transducers (12, 13) are designed to generate an ultrasonic wave (14) with a defined wavelength (X), wherein the periodically repeating triangular groove profile (19) has principal dimensions that correspond to the wavelength (X) or are at least in the range of the wavelength (X).

5. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the triangular groove profile (19) has a wide flank (19.1) and a narrow flank (19.2), thereby creating the asymmetry.

6. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the first and second ultrasonic transducers (12, 13) in connection with the measuring tube (10) are arranged diametrically opposite the diffraction structure (16), so that the ultrasonic wave (14) can be directed onto the diffraction structure (16) from a perpendicular (S).

7. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the diffraction structure (16) is designed such that a lateral diffraction maximum (B) can be formed when an ultrasonic wave (14) strikes from the perpendicular (S).

8. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the path of the ultrasonic wave (14) between the first and second ultrasonic transducer (12, 13) has a W-shape, wherein the W-shape is formed from two outer sound wave paths from the perpendicular (s) and two diffraction maxima (B) extending at a diffraction angle (y).

9. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the first and second ultrasonic transducers (12, 13) are designed to emit and / or receive ultrasonic waves (14) with a frequency of 0.5 MHz to 10 MHz and / or 1 MHz to 5 MHz and / or 1.5 MHz to 3 MHz and / or 2.1 MHz.

10. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the main dimensions of the triangular groove profile (19) have a grid constant (17) of 0.16 mm to 5.93 mm and / or of 0.5 mm to 4 mm and / or of 0.5 mm to 2 mm and / or of 0.7 mm to 1 mm and / or of 0.92 mm.

11. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the triangular groove profile (19) has a height (h) of 0.02 mm to 4.2 mm and / or 0.1 mm to 1 mm and / or 0.2 mm to 0.5 mm and / or 0.28 mm.

12. Ultrasonic flow meter (1) according to one of the preceding claims, characterized in that the wide flank (19.1) relative to the longitudinal axis (L) of the measuring tube (10) has a flank angle (a1) of 0° to 45° and / or a flank angle of 20° to 30° and / or a flank angle of 25° and / or the narrow flank (19.2) has a flank angle (oc2) of 0° to 90° and / or of 30° to 50° and / or of 40°.

13. Method for operating an ultrasonic flow meter (1), comprising a measuring tube (10) through which a flow chamber (11) extends and which is permeated by a flow medium in at least one flow direction along a longitudinal axis (L), wherein a first ultrasonic transducer (12) is arranged at a first position (I) and at least one second ultrasonic transducer (13) or at least one reflective surface is arranged at a second position (II), which emit an ultrasonic wave (14) into the flow chamber (11) and wherein the emitted ultrasonic wave (14) is received by the respective other ultrasonic transducer (12, 13) or the reflective surface, forming an ultrasonic propagation path, and wherein an inner wall segment (15) is arranged in the measuring tube (10) on which the emitted ultrasound wave (14) strikes and is reflected, the procedure comprising at least the following further steps: Design of the inner wall segment (15) as a diffraction structure (16); Emitting the ultrasound wave (14) perpendicular to the diffraction structure (16) and Generating at least one diffraction maximum (B) due to diffraction occurring at the diffraction structure (16), wherein the diffraction maximum (B) to the perpendicular (S) includes a diffraction angle (y).

14. Method according to claim 13, characterized in that the ultrasound wave (14) is emitted from a perpendicular (S) onto the diffraction structure (16), wherein the emitted ultrasound wave (14) is reflected at the diffraction structure (16) and is reflected at an angle to the perpendicular (S) predominantly in the direction of the diffraction maximum (B).

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