Flow meters using ultrasound

Abstract

Ultrasonic flow meter (1), comprising a measuring tube (10) through which a flow chamber (11) extends and which can be permeated by a flow medium (20) in at least one flow direction (111), 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 (16), 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 ultrasonic propagation path (16) extends perpendicular (16a) and transverse (16b) to the flow direction (111). exhibits.

Description

[0001] The invention relates to an ultrasonic flow meter with a measuring tube through which a flow space extends and through which a flow medium can flow in at least one flow direction, wherein a first ultrasonic transducer is arranged at a first position and at least one second ultrasonic transducer or at least one reflection surface is arranged at a second position in order to emit an ultrasonic wave into the flow space and to receive the emitted ultrasonic wave again from the other ultrasonic transducer or reflected from the reflection surface to form an ultrasonic propagation path, and wherein an inner wall segment is arranged in the measuring tube at which the emitted ultrasonic wave strikes and reflects. STATE OF THE ART

[0002] From DE 10 2006 019 146 B3 an ultrasonic flow meter has become known, comprising a measuring tube through which a flow space extends through which a flow medium flows, wherein a first ultrasonic transducer at a first position and a second ultrasonic transducer at a second position are arranged to emit an ultrasonic wave into the flow space and to receive the emitted ultrasonic wave from the other ultrasonic transducer.

[0003] The ultrasonic sensors are arranged at an angle on the measuring tube to generate the oblique path 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 the longitudinal axis through the flow space of the measuring tube, the fluid transports the ultrasonic wave with the flow to the receiving ultrasonic transducer more quickly than if the sound propagates against the flow direction. The resulting time-of-flight differences can be evaluated by evaluation electronics to determine the flow velocity of the fluid in the flow space of the measuring tube.

[0004] However, there are disadvantages to arranging the two ultrasonic transducers at an angle to the longitudinal axis on the outside of the measuring tube, since the ultrasound must penetrate the tube wall.

[0005] EP 3 800 448 B1 discloses a further embodiment of an ultrasonic flowmeter, comprising a measuring tube through which a flow chamber extends, through which a flow medium can flow. 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 occurs 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 restricting element comprises a first wedge having a first inclined surface, and wherein a first wedge has a first plurality of teeth protruding from the first inclined surface, wherein the flow channel has an outlet opening, and wherein the flow channel comprises an inlet opening, wherein the inlet opening is arranged opposite the outlet opening and a fluid path extends from the inlet opening to the outlet opening, wherein the three reflectors comprise a first reflector, wherein the first reflector is arranged closest to the outlet opening among the three reflectors;wherein the three reflectors comprise a second reflector, the second reflector being arranged closest to the inlet opening among the three reflectors, the flow-limiting element being inserted between the first reflector and the second reflector, the flow channel having a fourth wedge with a fourth inclined surface, the fourth wedge having at least one tooth protruding from the fourth inclined surface, and the fourth wedge being arranged between the second reflector and the inlet opening. The remaining flow cross-section is significantly constricted, primarily by the flow-limiting element, resulting in pressure losses in the flowmeter.

[0006] Ultrasonic flow meters are among the most precise and versatile instruments for measuring the flow of liquids and gases. They utilize the property of ultrasonic waves to move through various media at a characteristic speed, which is influenced by the flow velocity of the medium.

[0007] The basic principle of ultrasonic flow measurement is based on three essential techniques: In the time-of-flight method, two ultrasonic transducers send and receive signals along and against the flow direction, with the time-of-flight difference being used to calculate the flow velocity. The Doppler method, on the other hand, measures frequency changes in ultrasonic waves reflected by particles or gas bubbles in the medium and is therefore particularly suitable for media containing particles or air bubbles. The cross-correlation method analyzes the delay between correlated signals from different transducers, making it ideal for irregular flows.

[0008] Technological advances such as multi-path technology and clamp-on ultrasonic measurement significantly expand the application possibilities of these devices. Multi-path technology utilizes multiple ultrasonic paths to compensate for flow irregularities, such as turbulence or asymmetrical profiles, thus increasing measurement accuracy. Clamp-on technology allows the ultrasonic transducers to be attached to pipes from the outside using mounting elements, making them ideal for applications where intervention in the pipe system is undesirable.

[0009] Clamp-on ultrasonic measurement typically works according to the time-of-flight principle. Sound waves are transmitted through the pipe wall into the medium, reflected by the opposite pipe wall, and then measured. The time-of-flight difference between waves traveling in the direction of flow and waves traveling against the flow is used to calculate the flow velocity. Compared to inline measurements, where sensors are positioned directly in the medium and thus provide highly accurate results, the clamp-on method is non-contact and avoids interventions in the pipe system. However, it presents challenges such as signal loss due to reflections at interfaces.

[0010] Insert-in solutions represent a hybrid between invasive inline devices and non-contact clamp-on systems. They require sensors to be inserted into the pipeline through special openings or valves, allowing them to have direct contact with the medium. This offers the advantage of a less invasive installation compared to inline devices, but also presents specific challenges. Geometric changes in the pipe wall caused by insert-in sensors can create cavities and dead-water zones, causing flow disturbances, deposits, and inaccuracies. Pressure losses arise from flow resistance and turbulence, which are particularly prevalent with poorly positioned or non-aerodynamically shaped sensors.

[0011] Clamp-on technology also has specific disadvantages, such as the problem of structure-borne noise. Ultrasonic waves can also travel through the pipe wall, causing unwanted interference. Reflections at interfaces caused by differences in acoustic impedance, as well as air pockets that attenuate or scatter sound waves, present further challenges. At typical frequencies between 1 MHz and 10 MHz, even small air pockets can cause significant signal loss.

[0012] Optimizations such as the use of high-quality coupling materials, frequency matching, and advanced signal processing can help minimize these disadvantages. Overall, clamp-on ultrasonic measurement offers a flexible and non-contact solution for flow measurements, especially in applications where hygienic or operational requirements prohibit opening the pipe system.

[0013] Ultrasonic flow meters are widely used in industries including water supply, energy, chemical and petrochemical, and food and beverage. However, challenges remain, such as accuracy in difficult media, sensitivity to flow profiles, and adaptation to extreme operating conditions. Future developments will focus on miniaturizing the sensors, expanding measurement capabilities for heterogeneous media, and improving energy efficiency and robustness.

[0014] 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-water zones in front of the ultrasonic transducers, which negatively influence the flow of the flow medium. DISCLOSURE OF THE INVENTION

[0015] The object of the present invention is therefore to create an ultrasonic flowmeter that is simple to construct and that enables the lowest possible flow resistance for the flow medium flowing through the measuring tube. In particular, the invention aims to minimize pressure loss in insert sensors. Ideally, the flowmeter should only exhibit a pressure loss corresponding to the pipe section of its nominal diameter.

[0016] This object is achieved by an ultrasonic flowmeter according to the preamble of claim 1 in conjunction with the respective characterizing features. Advantageous developments of the invention are specified in the dependent claims.

[0017] The invention includes the technical teaching that the ultrasound propagation path has sections perpendicular and transverse to the flow direction.

[0018] The solution to the problem is, first of all, a clever choice of the ultrasound propagation path, because the paths perpendicular and transverse to the flow direction form an M-shape and not a W-shape. The M-shape is in the Fig. 2 to 4 are represented as a line. Strictly speaking, it is an inverted, upside-down M, as shown.

[0019] The M-shape has several advantages: The sensor end faces are largely designed to fit the inner wall of the pipe, so that they do not have any significant deviation from the inner wall contour of the rest of the measuring pipe, and the areas of dead water in cavities and projections are minimized.

[0020] Another advantage is that the M-shape allows measuring sections perpendicular to the flow, which makes it possible to measure the sound speed of the fluid, which is particularly dependent on temperature and purity.

[0021] The invention is therefore directed to an ultrasonic flow meter having a measuring tube through which a flow space extends and through which a flow medium can flow in a flow direction, wherein a first ultrasonic transducer is arranged at a first position and at least one second ultrasonic transducer or at least one reflection surface is arranged at a second position in order to emit an ultrasonic wave into the flow space and to receive the emitted ultrasonic wave again from the respective other ultrasonic transducer or the reflection surface to form 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 ultrasonic propagation path has paths perpendicular and transverse to the flow direction.

[0022] The ultrasound propagation path is M-shaped, with an inner "V" section of the M-shape running obliquely to the flow direction and outer I-sections of the M-shape running perpendicular to the flow direction.

[0023] At least one or more inner wall segments can form at least one or more cavities which are at least partially or completely covered by form-fitting cover surfaces for separating the fluid in the flow space and the ultrasonic transducer and each fluidically separate a volume of space within the cavity from the flow space.

[0024] Furthermore, it is provided that the cover surfaces are formed from a membrane which allows the volume of the cavity to be filled with the flow medium flowing through the flow space.

[0025] The membrane can form a sheet with openings and / or perforations and / or be sieve-like. Alternatively, at least one tube can be provided for ventilating the cavity, connecting the space volume with the flow medium inside the tube. Advantageously, two tubes are provided, arranged one behind the other in the direction of flow, thus enabling a constant fluid exchange in the cavity, despite a substantially closed cover surface.

[0026] Alternatively, the space can be filled with a potting compound, and the cover surface can be formed from the potting compound. The potting compound can have the same or similar sound velocity characteristics as the flow medium.

[0027] The flow medium can be a gas or a liquid. It is also conceivable for the flow medium to be a phase mixture and / or to contain gaseous, liquid, and / or solid components. For example, the flow medium can be formed at least partially by H2O.

[0028] The potting compound can behave like polyurethane and / or like “AptFlex F7” and / or have this.

[0029] It is also conceivable that the thickness of the membrane corresponds to half the wavelength of the sound in the membrane material, or an integer multiple thereof. This makes it possible for the membrane to become particularly permeable to sound of the frequency used. This achieves a lambda / 2 conduction, which ensures that the membrane's characteristic sound impedance is almost invisible, thus becoming acoustically transparent. PREFERRED EMBODIMENT OF THE INVENTION

[0030] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows: Fig. 1 an ultrasonic flowmeter with two ultrasonic transducers arranged on the outside of the measuring tube, Fig. 2 an ultrasonic flowmeter with vertically incoming or receiving ultrasonic transducers for forming an M-shape in the ultrasonic propagation path, with two cavities being incorporated in the inner contour of the measuring tube, Fig. 3 an ultrasonic flow meter with two cavities in the inner contour of the measuring tube, which are filled with a casting compound and Fig. 4 an ultrasonic flowmeter with two cavities in the inner contour of the measuring tube, which are covered with a membrane that is permeable to sound and fluids.

[0031] Fig. 1 shows how the Fig. 2, Fig. 3 and Fig. 4 an ultrasonic flow meter 1, with a measuring tube 10, through which a flow space 11 extends and through which a flow medium 20 can flow in a flow direction 111, wherein a first ultrasonic transducer 12 at a first position I and at least one second ultrasonic transducer 13 or at least one reflection surface at a second position II are arranged to emit an ultrasonic wave 14 into the flow space 11 and to receive the emitted ultrasonic wave 14 from the other ultrasonic transducer 12, 13 or the reflection surface to form an ultrasonic propagation path 16, and wherein an inner wall segment 15 is arranged in the measuring tube 10, at which the emitted ultrasonic wave 14 strikes and reflects, see in particular the Fig. 2 to 4. The ultrasonic transducers 12, 13 according to the Fig. 1 are attached to the outside of the measuring tube 10 by means of holding elements 3, so that an oblique sounding of the ultrasonic wave is possible, which is part of the state of the art.

[0032] As in Fig. As shown in Figure 2, large cavities 17 in front of the reflectors at the tips of the M-shape would be disadvantageous. According to the invention, these cavities are removed from the flow dynamics by cover surfaces 18, 19.

[0033] As in Fig. 3 and Fig. As shown in Figure 4, the cover surfaces 18, 19 are provided with a form-fitting connection to the inner pipe wall. Consequently, the flow medium 20 experiences an almost normal pipe section with a simply continued inner pipe wall.

[0034] There are two options for filling the cavities: Firstly, the cavity can be filled with a potting compound 24 with an ultrasonic propagation velocity characteristic comparable to the propagation velocity characteristic in the flow medium 20. The potting compound "AptFlex F7" may be particularly suitable, as it exhibits similar acoustic behavior to conventional flow media that contain water or are similar to water. Secondly, the space behind the cover surface 18, 19 can be filled by the flowing fluid. This generally maintains the same ultrasonic propagation velocity, although the perforation in the membrane can be designed to allow fluid exchange to occur in the cavity, i.e., behind the membrane.

[0035] AptFlex F7 is a special polyurethane-based potting compound commonly used in ultrasound technology. Distributed by Precision Acoustics Ltd, it primarily serves as an acoustically optimized material for applications requiring low attenuation and good acoustic impedance matching.

[0036] AptFlex F7 features low acoustic attenuation, which ensures high signal quality and low losses during ultrasonic transmission. It also provides good acoustic impedance matching, which is particularly important for minimizing reflections at interfaces. It also allows for the use of a flexible and durable material, making it particularly suitable for use in rugged and variable environments.

[0037] AptFlex F7 is also easy to process; it is supplied in liquid form and cures to a flexible, solid material. AptFlex F7 is used for encapsulation and protection of ultrasonic sensors. AptFlex F7 is often used to protect ultrasonic sensors from mechanical damage, moisture, and other environmental factors. AptFlex F7 can also serve as an acoustic coupling medium, particularly in the manufacture of ultrasonic arrays or acoustic elements. In research and development, AptFlex F7 can be used in ultrasound technology and related fields to enable precise measurements.

[0038] The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of variants are conceivable, which utilize the presented solution even in fundamentally different embodiments. All features and / or advantages apparent from the claims, the description, or the drawings, including structural details or spatial arrangements, may be essential to the invention both individually and in a wide variety of combinations. List of reference symbols: 1 ultrasonic flow meter 3 Holding element 10 measuring tube 11 Flow space 12 ultrasonic transducers 13 ultrasonic transducers 14 Ultrasonic wave 15 inner wall segment 16 Ultrasonic propagation path 16a vertical section 16b transverse route 17 Cavity 18 deck area 19 Cover area 20 Flow medium 21 room volume 22 Membran 23 tubes 24 Potting compound 111 Flow direction QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2006 019 146 B3

[0002] EP 3 800 448 B1

[0005] EP 1 096 236 A2

[0014] DE 39 41 544 A1

[0014]

Claims

[1] Ultrasonic flowmeter (1), comprising a measuring tube (10) through which a flow space (11) extends and through which a flow medium (20) can flow in at least one flow direction (111), 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 reflection surface is arranged at a second position (II) in order to emit an ultrasonic wave (14) into the flow space (11) and to receive the emitted ultrasonic wave (14) from the respective other ultrasonic transducer (12, 13) or the reflection surface to form an ultrasonic propagation path (16), and wherein an inner wall segment (15) is arranged in the measuring tube (10) at which the emitted ultrasonic wave (14) impinges and is reflected, characterized by that the ultrasound propagation path (16) has sections perpendicular (16a) and transverse (16b) to the flow direction (111). [2] Ultrasonic flowmeter (1) according to claim 1, characterized by that the ultrasonic propagation path (16) is M-shaped, wherein an inner "V" section of the M-shape is designed to run obliquely to the flow direction (111) and outer I-sections of the M-shape are designed to run perpendicular to the flow direction (111). [3] Ultrasonic flowmeter (1) according to claim 1 or 2, characterized by in that at least one or more inner wall segments (15) form cavities (17) which are at least partially or completely covered by form-fitting cover surfaces (18, 19) for separating the fluid in the flow space (11) and the ultrasonic transducer (12, 13) and which each fluidically separate a spatial volume (21) within the cavity (17) from the flow space (11). [4] Ultrasonic flowmeter (1) according to one of claims 1 to 3, characterized bythat the cover surfaces (18, 19) are formed from a membrane (22) which allows the space volume (21) of the cavity (17) to be filled with the flow medium (20) flowing through the flow space (11). [5] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the membrane (22) forms a sheet body with openings and / or perforations and / or is designed like a sieve. [6] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that at least one tube is provided which connects the space volume (21) with the flow medium (20) in the interior of the tube. [7] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the space volume (21) is filled with a casting compound (24) and the cover surface (18,19) is formed from the casting compound (24). [8] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the casting compound (24) has the same or similar sound velocity characteristics as the flow medium. [9] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the flow medium (20) is a gas. [10] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the flow medium (20) is a liquid. [11] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the flow medium (20) is a phase mixture and / or has gaseous, liquid and / or solid components. [12] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the flow medium (20) is at least partially formed by H2O. [13] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the casting compound (24) behaves like polyurethane and / or like “AptFlex F7” and / or has components thereof or consists of these. [14] Ultrasonic flowmeter (1) according to one of the preceding claims, characterized by that the thickness of the membrane (22) corresponds to half the wavelength of the sound in the material of the membrane (22) or an integer multiple thereof.

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