Ultrasonic flow measuring device

Abstract

The invention relates to an ultrasonic flow measuring device, comprising a measuring tube, a first and a second ultrasonic transducer, which are arranged axially offset on the measuring tube and are designed as an ultrasonic actuator and an ultrasonic sensor, and a control and evaluation unit, in the operating state, the control and evaluation unit actuates the ultrasonic actuator in order to excite guided ultrasonic waves in the measuring tube and propagate therein in a guided manner in the axial extension direction in a combined waveguide comprising the measuring tube and the fluid, and the ultrasonic sensor receives the guided ultrasonic waves and determines the flow velocity of the fluid by evaluation. Advantageous excitation of the guided ultrasonic waves is achieved in that the ultrasonic actuator has a plurality of excitation structures in the axial extension direction, which are axially spaced apart from one another, by means of which ultrasonic waves are fed into the measuring tube, and in that the wave pattern of at least one predetermined wave pattern of the guided ultrasonic waves is excited in the measuring tube in a spatially distributed manner in the axial direction.

Description

Technical Field

[0001] This invention relates to an ultrasonic flow measurement device comprising a measuring tube, a first ultrasonic transducer, a second ultrasonic transducer, and a control and evaluation unit. The first and second ultrasonic transducers are arranged axially offset at the measuring tube. The first ultrasonic transducer is configured at least as an ultrasonic actuator, and the second ultrasonic transducer is configured at least as an ultrasonic sensor. In operation of the ultrasonic flow measurement device, the control and evaluation unit manipulates the ultrasonic actuators such that guided (or directed, i.e., geführte) ultrasonic waves are excited in the measuring tube through which fluid flows. The guided ultrasonic waves propagate guidedly in the measuring tube and the fluid along the axial extension direction of the measuring tube in a combined waveguide comprising the measuring tube and the fluid. The ultrasonic sensor receives the guided ultrasonic waves, and the control and evaluation unit determines the fluid flow velocity by evaluating the received guided ultrasonic waves. Furthermore, the invention relates to a method for determining at least one wave mode generated during flow measurement in the aforementioned ultrasonic flow measurement device. Background Technology

[0002] Flow measurement using ultrasound has been known for decades. Regardless of the specific measurement method used (e.g., run-time measurement, run-time difference measurement (in and out of the flow direction), frequency measurement / Doppler effect), flow measurement is always based on the action of ultrasound in the fluid flowing through the measuring tube, where the flow velocity of the fluid should be acquired.

[0003] In most ultrasonic flow measurement devices, the characteristic cross-sectional dimension of the measuring tube (diameter in a circular measuring tube) is significantly larger than the wavelength of the ultrasonic waves generated by the ultrasonic actuator. Typically, measures are implemented for beamforming. As a result, the ultrasonic waves propagating in the fluid within the measuring tube can be considered and described as free waves, in which the measuring tube plays no decisive role in their propagation except for reflections at the tube wall.

[0004] This changes in ultrasonic flow measurement devices with a measuring tube (whose characteristic cross-sectional dimensions are within the range of the ultrasonic wavelengths used). In this case, the wall of the measuring tube is always a geometric boundary condition to be considered for the motion and propagation of the ultrasonic waves, which then propagate as guided ultrasound in a combined or hybrid waveguide comprising the measuring tube and the fluid, thus guiding the ultrasound to move both through the measuring tube and through the fluid. Within the scope of this invention, this refers to ultrasonic flow measurement devices operating according to this principle.

[0005] To clarify, it should be noted that the functional principle upon which this invention is based differs from that of ultrasonic flow measurement devices with guided waves, where the guided propagation of ultrasound occurs only within the measuring tube. Ultrasound—depending on the type of excited ultrasound guided within the measuring tube—transfers to varying degrees from the measuring tube into the fluid, but continues to travel in the fluid as unguided ultrasound (i.e., free-space waves). Such flow measurement devices are also known as leaky Lamb wave flow measurement devices, which operate using guided Lamb waves in the measuring tube wall and utilize the resulting free-space ultrasound in the medium. Ultrasonic flow measurement devices operating on this principle are not within the scope of this invention.

[0006] Depending on the geometric and physical boundary conditions of the measuring tube, fluid parameters, and the frequency of the excitation ultrasound, different vibration modes can propagate along the waveguide comprising the measuring tube and the fluid. These wave modes possess different spatial and temporal propagation characteristics. The wave modes can be more or less advantageously selected. Summary of the Invention

[0007] The objective of this invention is to describe an ultrasonic flow measurement device of the type described above, which is capable of exciting and / or receiving guided ultrasonic waves in an advantageous manner, and to describe a method by which the advantageous vibration mode of the excited and guided ultrasonic waves can be determined.

[0008] In the ultrasonic flow measurement device described at the beginning, this task is first addressed by having an ultrasonic transducer, at least designed as an ultrasonic actuator, with multiple excitation structures spaced apart from each other in the axial extension direction of the measuring tube. By means of the excitation structures, ultrasonic waves are fed into the measuring tube through which the fluid flows, thereby spatially distributing at least one predetermined wave mode (or waveform pattern, i.e., Wellenmuster) of the ultrasonic waves guided in the measuring tube through which the fluid flows in the axial extension direction.

[0009] From the case of feeding ultrasonic waves into the fluid through a flow-through measuring tube using an excitation structure, it follows that the excitation structure somehow has a contact surface with the measuring tube and / or the fluid guided within it, wherein acoustic excitation of the measuring tube and / or the fluid is performed via the contact surface, thus energy transfer occurs here. In the free space created by the gaps between the excitation structures, no excitation of the measuring tube and / or the fluid occurs; active excitation is not performed in any way. In some cases, this may not prevent small parasitic excitations, but this does not contradict the teachings presented herein.

[0010] Sound waves propagating in specific vibration modes through the medium and along the axial extension of the measuring tube exhibit spatial (measuring tube extension) and temporal dependencies. If a specific location within the measuring tube is observed, temporal amplitude variations can be observed; if the entire measuring tube is observed at a specific point in time, the spatial orientation of the sound wave amplitude can be observed. Overall, at specific frequencies within a specific mode, ultrasound waves exhibit characteristic spatiotemporal features along the waveguide—from the ultrasonic actuator to the ultrasonic sensor—in the form of a measuring tube utilizing fluid flow.

[0011] A major advantage of the ultrasonic flow measurement device according to the invention is that multiple acoustic excitations can be performed—simultaneously or staggered in time—by means of multiple excitation structures spaced apart from each other at multiple locations viewed in the extension direction of the measuring tube. These excitations are selected such that they correspond precisely to the characteristic spatiotemporal characteristics, i.e., the waveform of the ultrasonic waves propagating through the measuring tube guided by the fluid flow, in accordance with a predetermined wave pattern.

[0012] By using multiple spaced-apart excitation structures, an extended, structured excitation layer is achieved along the extension direction of the measuring tube. This allows for the more specific excitation of one (or more) desired and therefore predetermined wave modes compared to using only a single excitation location (viewed along the extension direction of the measuring tube). The waveform of the desired, predetermined wave mode can actually be imprinted spatiotemporally into the flowing measuring tube. Consequently, higher selectivity in wave mode excitation is automatically achieved compared to a single excitation source, thus better automatic suppression of undesired wave modes. Even the intensity of wave mode propagation to the left and right of the excitation structure location can be influenced, thus enabling selective suppression of undesired wave modes in the direction of the ultrasonic sensor and selective promotion of desired (i.e., predetermined) wave modes in the direction of the ultrasonic sensor.

[0013] A preferred design of the ultrasonic flow measurement device is characterized in that the second ultrasonic transducer, configured as an ultrasonic sensor, is constructed substantially the same as the first ultrasonic transducer (i.e., having multiple excitation structures) configured as an ultrasonic actuator, such that the excitation structures function as acquisition structures (or capture structures). In particular, the second ultrasonic transducer is constructed identically to the first ultrasonic transducer configured as an ultrasonic actuator.

[0014] By implementing an ultrasonic sensor with multiple excitation structures that function as acquisition structures, it is possible in principle to selectively acquire and identify specific wave modes of guided ultrasonic waves, filter out unwanted wave modes in time and space, and evaluate this solely through the geometric arrangement of multiple excitation / acquisition structures, but also through time windows or through the sum of received signals appropriately delayed by each excitation / acquisition structure.

[0015] In another advantageous design, the first ultrasonic transducer is also configured as an ultrasonic sensor, and the second ultrasonic transducer is also configured as an ultrasonic actuator. Here, the implementation of the excitation structure is provided, for example, using a piezoelectric element, which can be used as either an actuator or a sensor as needed. Given that many ultrasonic flow measurement devices implement time difference measurement, i.e., performing time measurements in both the forward and reverse flow directions, the identical design of the first and second ultrasonic transducers is also meaningful. Preferably, the control and evaluation unit operates the first and second ultrasonic transducers such that the flow velocity of the fluid in the measuring tube is determined via time difference measurement.

[0016] In one improvement of the ultrasonic flow measurement device, the measuring tube is constructed as an acoustic coupler in the excitation structure region to improve acoustic transmission (impedance matching) from the excitation structure to the fluid in the measuring tube. In an alternative improvement, the measuring tube is formed by the excitation structure itself in the excitation structure region to transmit sound directly from the excitation structure to the fluid in the measuring tube.

[0017] There are very different possibilities for designing the ultrasonic flow measurement device with multiple excitation structures described above. Two different design concepts are described below.

[0018] The first conceptual design of the ultrasonic flow measurement device according to the invention is characterized in that the excitation structure is formed by at least two rings spaced apart from each other in the axial extension direction of the measuring tube and surrounding the measuring tube in the circumferential direction. A particularly simple arrangement is that, in the case of at least three rings, the rings are equidistant from each other.

[0019] In a preferred improvement of the ultrasonic flow measurement device, the ring is a separate ultrasonic actuator, and more particularly, the ultrasonic actuator can be individually controlled by a control and evaluation unit. It is this design that enables the time-staggered control of multiple excitation structures at multiple locations viewed along the extension direction of the measuring tube. These excitations are performed in such a way that they precisely generate the waveform of the ultrasonic waves propagating through the measuring tube guided by the fluid flow, representing a predetermined wave pattern. The advantage of the time-variable and individually controllable nature of the ring-shaped ultrasonic actuator lies in its adaptability to changing boundary conditions, such as when the fluid undergoes changes in its composition or temperature.

[0020] In one alternative design, multiple excitation structures designed as loops are simultaneously manipulated by a control and evaluation unit, which simplifies the design of the control and evaluation unit. In this case, the spacing between the individual loops must be chosen such that it precisely induces the waveform of the predetermined wave mode, which is guided by the measuring tube through which the ultrasound propagates.

[0021] As can be seen in the example, when a predetermined wave mode is excited in a measuring tube through which fluid flows, there are, in principle, two degrees of freedom to excite the spatiotemporal characteristics of the desired wave mode (at a specific frequency): the spatial spacing between the excitation structures and the temporal excitation time of each excitation structure (if it can be excited individually).

[0022] A special design of an ultrasonic flow measurement device that utilizes an excitation structure implemented as a ring is characterized by the ring being contacted and manipulated by the control and evaluation units via the inner and outer circumferential surfaces of the ring (radial operation mode), or by the control and evaluation units via two opposing base surfaces (axial operation mode); this is particularly meaningful when the excitation structure designed as a ring is a piezoelectric element or, in any case, has a piezoelectric element.

[0023] In another preferred design of the ultrasonic flow measurement device, the rings are supported in a common ring bracket, particularly connected to the common ring bracket via their outer circumferential surface. The common ring bracket at least partially contains a material that attenuates ultrasonic crosstalk between the rings. This approach has the advantage that the rings can be configured within the ring bracket, i.e., they can be held in place at the desired spacing before being mounted onto the measuring tube. This offers advantages in terms of operability, especially when it is a so-called clamping configuration.

[0024] In a preferred design of the control and evaluation unit of an ultrasonic flow measurement device, the loop of the ultrasonic actuator is manipulated with a time delay in the direction toward the ultrasonic sensor, so that the ultrasonic waves are amplified in a predetermined wave mode in the direction toward the ultrasonic sensor. This also achieves a certain degree of directional selectivity, namely, amplification of the ultrasonic waves in the direction from the ultrasonic actuator toward the ultrasonic sensor.

[0025] In a preferred design of an ultrasonic flow measurement device, the ultrasonic sensor and ultrasonic actuator are constructed with multiple excitation structures to selectively acquire a predetermined wave pattern. This is achieved by evaluating the received signals provided by the multiple acquisition structures in a time window or with a time delay, based on the propagation characteristics of the predetermined wave pattern. During time windowing, for example, the spatial spacing between the propagation velocity of the desired wave pattern and the maximum amplitude at a specific frequency can be used. If no received signal consistent with the propagation characteristics of the wave pattern is received within the time evaluation window, this indicates that the desired wave pattern is not present. When the signals acquired by different acquisition structures are time-delayed and subsequently added, an excess signal level may indicate the presence of the acquired predetermined wave pattern, while a deficiency signal level may indicate the absence of the predetermined wave pattern.

[0026] Based on the implementation of an ultrasonic flow measurement device with multiple ring excitation and acquisition structures, it can be clearly seen that multiple vibration modes can also be excited simultaneously. In the case of two rings, there are two degrees of freedom in the design of the excitation structure: the spatial spacing of the rings and the time-delayed excitation. Multiple excitation structures automatically bring more degrees of freedom in their design, allowing for the selective excitation of multiple modes and the selective acquisition of multiple modes.

[0027] A second concept of the ultrasonic flow measurement device according to the present invention is characterized in that the ultrasonic actuator includes a conical body with a central notch for accommodating a measuring tube, wherein the inner wall of the body formed by the notch is structured in the axial extension direction of the measuring tube by at least one recess extending in the circumferential direction of the measuring tube, and at least two protrusions formed by the at least one recess in the inner wall of the body form an excitation structure. An ultrasonic actuator is arranged at the base surface of the conical body, which feeds ultrasonic waves into the conical body, wherein the ultrasonic waves are at least partially reflected at the circumferential surface of the conical body and the guided ultrasonic waves are excited in the measuring tube through which the fluid flows via the protrusions of the inner wall of the body. In this design, the protrusions in the wall of the body form a contact surface for transmitting energy to the measuring tube / fluid.

[0028] Compared to the first concept of ultrasonic actuator design, the second concept has lower degrees of freedom because the protrusions in the substrate are fixedly mounted. Furthermore, the ultrasonic waves are generated solely by an ultrasonic actuator that feeds the waves into the conical substrate, where they are distributed by reflections at the circumferential surface and ultimately fed into the waveguide (measuring tube / fluid) via the protrusions in the substrate wall.

[0029] In a preferred design of the aforementioned ultrasonic flow measurement device, the ultrasonic actuator is designed as a ring, particularly a ring-shaped piezoelectric element. Preferably, the ring-shaped piezoelectric element is contacted by a control and evaluation unit via the inner and outer circumferential surfaces of the ring (radial excitation mode). Alternatively, the ring-shaped piezoelectric element is manipulated by the control and evaluation unit via two opposing base surfaces (axial excitation mode).

[0030] Regardless of whether the ultrasonic actuator is implemented according to the first or second concept, it is advantageous in any case that the ultrasonic actuator is implemented in multiple parts, allowing it to be radially inserted into the measuring tube, especially since the multiple parts are pivotally supported by one or more hinges. Thus, the ultrasonic actuator (and, if necessary, the ultrasonic sensor accordingly) can be subsequently mounted onto the measuring tube (clamp-on type) without requiring the free end of the conduit to push the ultrasonic transducer from there onto the measuring tube.

[0031] The task proposed at the beginning is also solved by a method for determining at least one wave mode generated during flow measurement in an ultrasonic flow measurement device, which is then used as a predetermined wave mode during operation of the ultrasonic flow measurement device. This is further illustrated by an ultrasonic flow measurement device comprising a measuring tube, a first ultrasonic transducer, a second ultrasonic transducer, and a control and evaluation unit. The first and second ultrasonic transducers are axially offset at the measuring tube, wherein the first ultrasonic transducer is at least configured as an ultrasonic actuator, and the second ultrasonic transducer is at least configured as an ultrasonic sensor. During operation of the ultrasonic flow measurement device, the control and evaluation unit manipulates the ultrasonic actuator to excite guided ultrasonic waves in the measuring tube through which fluid flows. The ultrasonic sensor receives the guided ultrasonic waves. The control and evaluation unit determines the flow velocity of the fluid by evaluating the received guided ultrasonic waves. The ultrasonic transducers, at least designed as ultrasonic actuators, have multiple excitation structures in the axial extension direction of the measuring tube, wherein the excitation structures are spaced apart from each other in the axial extension direction of the measuring tube. By means of an excitation structure, ultrasonic waves are fed into a measuring tube through which a fluid flows, such that the specific wave pattern of the ultrasonic waves excited and guided in the measuring tube through the fluid is spatially distributed in the axial extension direction of the measuring tube.

[0032] In order to selectively deduce favorable predetermined wave modes, the phase velocity and group velocity of the acoustic wave in the frequency range are determined for multiple wave modes, given the geometric and physical boundary conditions of the measuring tube through which the fluid flows. Then, a wave mode is selected as the predetermined wave mode that receives the highest evaluation at a specific frequency within the frequency range when evaluating at least one of the criteria mentioned below.

[0033] The smaller the difference between the phase velocity and the group velocity, the better the evaluation. This is especially advantageous when combined with another criterion: the closer the phase velocity and / or group velocity are to the speed of sound in the fluid, the better the evaluation. This criterion ensures that the guided wave is as planar as possible across the cross-section of the measuring tube.

[0034] The smaller the frequency dependence of phase velocity and group velocity, the better the evaluation. In this way, the dependence of frequency variation during excitation can be kept small.

[0035] The larger the minimum spacing in the phase velocities between different modes, the better the evaluation. In this way, it is ensured that the desired and therefore predetermined vibration modes have significantly different waveforms from other (i.e., undesirable) vibration modes, and thus good selective excitation and selective reception are possible.

[0036] The larger the minimum spacing in the group velocities between different modes, the better the evaluation. In this way, the desired mode has the most different running time performance compared to other vibration modes, making the mode as distinguishable as possible.

[0037] The more axisymmetric the model, the better the evaluation. This results in flow measurement with the least possible dependence on flow non-uniformity along the axis of the measuring pipe.

[0038] The more similar the relative changes in phase velocity and / or group velocity are to the relative changes in the velocity of sound in the fluid, the better the evaluation. Thus, the phase velocity and / or group velocity are kept as similar as possible to the velocity of sound in the fluid, even if the velocity of sound changes. This is advantageous in terms of conforming to a planar waveform, which is therefore preferred because it inherently averages the flow velocity profile (or flow velocity curve, i.e., Flussgeschwindigkeitsprofil) using this (in run-time difference measurements), and the flow velocity of the fluid can thus be determined independently of the flow velocity profile.

[0039] The less amplitude attenuation the mode experiences as it propagates in the fluid, the better the evaluation. This ensures good signal strength for the predetermined wave mode.

[0040] The more constant the amplitude of the pattern across the cross-section of the measuring tube, the better the evaluation. This criterion makes the measurement more independent of the flow non-uniformity of the fluid across the cross-section of the measuring tube.

[0041] An improved version of the method is configured to appropriately select the design of the excitation structure based on the found predetermined wave mode and the found specific frequency, especially the spatial spacing between the excitation structures along the axis of the measuring tube and / or the time interval of the excitation of the excitation structures.

[0042] An improvement to this method involves checking the suitability of the selected excitation structure design (including time manipulation of the structure). The check examines whether the amplitude achieved by the specific and therefore desired mode is large enough, if possible, greater than the amplitude of the undesired mode at a specific frequency. Therefore, the improved method is characterized by determining, for at least a predetermined wave mode, the amplitude of the generated sound wave at the excitation frequency based on the phase velocity of the generated sound wave within the frequency range, taking into account the geometric and physical boundary conditions of the fluid-through-measuring tube and the design of the excitation structure. If the amplitude of a specific wave mode does not reach a minimum, especially if the amplitude of the specific wave mode at a specific frequency is less than the amplitude of the undesired wave mode, the design of the excitation structure is abandoned and modified. In particular, this process is repeated until a design of the excitation structure that should no longer be abandoned is found.

[0043] A preferred design of this method is to perform a standard evaluation, i.e., to introduce the observed wave modes studied according to the standard into the evaluation sequence and score them, and to determine the best mode as the predetermined mode based on the total score obtained. It has proven feasible to use relative evaluation scales instead of absolute ones for each standard. For example, if four wave modes are studied, then a standard is calculated at the observed frequencies (e.g., the phase velocity is close to the speed of sound in the fluid), and the wave mode that best meets this standard receives a score of 4, the second best wave mode receives a score of 3, and so on.

[0044] If a particular criterion is particularly important, it proves advantageous to incorporate different criteria into the evaluation with different weights. In the evaluation example explained earlier, important criteria can be, for example, double-weighted in a relative evaluation scale.

[0045] If such a favorable predetermined wave mode is found at a specific frequency using the method shown above for determining a favorable predetermined wave mode, then the predetermined wave mode is excited at that specific frequency during the operation of the ultrasonic flow measurement device. Attached Figure Description

[0046] Specifically, there are now various possibilities for designing and improving the ultrasonic flow measurement device according to the invention and the method according to the invention. Therefore, reference is made, on the one hand, to the dependent patent claims which are subordinate to the independent patent claims, and on the other hand, to the following description of embodiments in conjunction with the accompanying drawings. In the drawings: Figure 1 An ultrasonic flow measurement device known from the prior art is schematically shown, which operates by utilizing guided ultrasonic waves. Figure 2 An embodiment of an ultrasonic flow measurement device with an ultrasonic actuator having multiple excitation structures is schematically shown. Figure 3 schematically illustrates an ultrasonic actuator with multiple excitation structures, acoustic coupling elements, and direct contact with the fluid. Figure 4 An ultrasonic actuator with equally spaced excitation structures is schematically shown. Figure 5 The excitation element, a ring-shaped structure, is schematically shown as a piezoelectric element with different contacts. Figure 6 schematically illustrates a multi-component ultrasonic actuator having sub-components that can pivotally support each other. Figure 7 An ultrasonic flow measurement device is schematically shown, which has an ultrasonic actuator and an ultrasonic sensor, both having a conical base with multiple excitation structures. Figure 8 The diagram illustrates, in more detail, the basis. Figure 7 Ultrasonic actuator. Figure 9 The method for determining a suitable wave pattern, which is used as a predetermined wave pattern when operating the ultrasonic flow measurement device shown above, is illustrated schematically. Figure 10 schematically illustrates the phase velocity and group velocity of different wave modes for a specific configuration of an ultrasonic flow measurement device. Figure 11 schematically illustrates the amplitude of the excited ultrasonic wave, depending on the excitation frequency and the applicable phase velocity, once in the positive propagation direction and once in the negative propagation direction. Detailed Implementation

[0047] The figure illustrates different aspects of an ultrasonic flow measurement device 1, which includes a measuring tube 2, a first ultrasonic transducer 3, a second ultrasonic transducer 4, and a control and evaluation unit 5. The first ultrasonic transducer 3 and the second ultrasonic transducer 4 are arranged axially offset at the measuring tube 2, and the first ultrasonic transducer 3 is configured at least as an ultrasonic actuator 6, and the second ultrasonic transducer 4 is configured at least as an ultrasonic sensor 7. During operation of the ultrasonic flow measurement device 1, the control and evaluation unit 5 manipulates the ultrasonic actuator 6 to excite guided ultrasonic waves 9 in the measuring tube 2 through which fluid 8 flows. The ultrasonic sensor 7 receives the guided ultrasonic waves 9, and the control and evaluation unit 5 determines the flow velocity v of the fluid 8 by evaluating the received guided ultrasonic waves 9.

[0048] Figure 1An ultrasonic flow measurement device 1, known from the prior art, is shown, which operates using guided ultrasonic waves 9. A measuring tube 2 and the fluid 8 guided within the measuring tube 2 together constitute a waveguide on which the guided ultrasonic waves 9 propagate. The propagation of the guided ultrasonic waves 9 in the waveguide is described by a wave equation, which, in solving, must take into account the geometric boundary conditions of the waveguide and, of course, other physical parameters of the components (e.g., the medium). It is well known that only specific waveforms, referred to as wave modes, can propagate stably in a waveguide. In the embodiment shown here, the flow velocity v of the fluid 8 is determined using the time-difference method, i.e., determining the signal travel time of the guided ultrasonic waves 9 by considering both the flow direction in which the fluid 8 flows and the flow direction against the flow direction. This has the advantage that, when calculating the fluid velocity v, identical components of the velocity of the ultrasonic waves 9 in the fluid 8, independent of the flow direction of the fluid 8, automatically cancel each other out.

[0049] According to Figure 1 In the ultrasonic flow measurement device 1 known from the prior art, there exists only a single, point-acting ultrasonic actuator 6 and a single, point-receiving ultrasonic sensor 7. According to the principle, the ultrasonic actuator 6 can only excite ultrasonic waves in a very non-specific manner, and according to the principle, the ultrasonic sensor 7 can only acquire ultrasonic waves in a very non-specific manner.

[0050] In contrast, the ultrasonic flow measurement device 1 shown in other figures operates with significant modifications. Other ultrasonic flow measurement devices 1 with ultrasonic actuators 6 or ultrasonic sensors 7 are characterized in that the ultrasonic transducer 3, designed at least as the ultrasonic actuator 6, has a plurality of excitation structures 10 in the axial extension direction of the measuring tube 2, wherein the excitation structures 10 are spaced apart from each other in the axial extension direction of the measuring tube 2. By means of the excitation structures 10, ultrasonic waves 9 are fed into the measuring tube 2 through which fluid 8 flows, thereby spatially distributing at least one predetermined wave mode of the ultrasonic waves 9 guided in the measuring tube 2 through which fluid 8 flows in the axial extension direction of the measuring tube 2. The excitation structure 10 has a contact surface 11 with the measuring tube 2 and / or the fluid 8 guided in the measuring tube 2, wherein acoustic excitation of the measuring tube 2 and / or the fluid 8 is performed via the contact surface 11.

[0051] Multiple acoustic excitations can be performed simultaneously or staggered in time by using multiple spaced-apart excitation structures 10 at multiple locations viewed along the extension direction of the measuring tube 2. These excitations are selected such that they precisely correspond to characteristic spatiotemporal characteristics, i.e., the waveform of the ultrasonic wave 9 propagating via the measuring tube 2 through which the fluid 8 flows, representing a predetermined wave mode. The multiple spaced-apart excitation structures 10 create an extended, structured excitation layer along the extension direction of the measuring tube 2, thereby enabling the more specific excitation of a desired (or multiple desired) and therefore predetermined wave mode. This is consistent with...Figure 1 This is advantageous compared to embodiments with only a single excitation location. Thus, by means of an excitation layer via an excitation structure 10 spatially distributed along the measuring tube 2, the desired, predetermined wave pattern can be spatiotemporally imprinted into the flowing measuring tube 2.

[0052] according to Figure 2 and Figure 7 The common feature of the embodiments is that the second ultrasonic transducer 4, configured as an ultrasonic sensor 7, is constructed in essentially the same way as the first ultrasonic transducer 2, configured as an ultrasonic actuator 6. The ultrasonic sensor 7 therefore also has multiple excitation structures 10, wherein the excitation structures 10 function as acquisition structures. According to... Figure 7 In one embodiment, the second ultrasonic transducer 4 is constructed in the same manner as the first ultrasonic transducer 3, which is configured as an ultrasonic actuator 6.

[0053] In all the ultrasonic flow measurement devices 1 shown in the figure, the first ultrasonic transducer 3 is also configured as an ultrasonic sensor 7, and the second ultrasonic transducer 4 is also configured as an ultrasonic actuator 6. This is meaningful because—as previously stated—the control and evaluation unit 5 operates the first ultrasonic transducer 3 and the second ultrasonic transducer 4 in such a way that the flow velocity v of the fluid 8 in the measuring tube 2 is determined by measuring the time difference of operation.

[0054] The embodiment of the ultrasonic flow measurement device 1 shown in the figure operates using a measuring tube 2 with an inner diameter significantly less than one centimeter. The measuring tube 2 is implemented in a flexible, hose-like manner, i.e., made of a perfluoroalkoxy polymer (i.e., an elastic plastic). In other designs not shown here, the measuring tube 2 is implemented mechanically rigidly, particularly made of metal, plastic, ceramic, or glass.

[0055] According to Figure 3a In the ultrasonic flow measurement device 1, the measuring tube 2 is configured as an acoustic coupler 12 in the region of the excitation structure 10 to improve the acoustic transmission of the fluid 8 from the excitation structure 10 to the measuring tube 2.

[0056] According to Figure 3b In the ultrasonic flow measurement device 1, the measuring tube 2 is formed by the excitation structure 10 itself in the region of the excitation structure 10, so as to transmit sound directly from the excitation structure 10 to the fluid 8 in the measuring tube 2. Therefore, the contact surface 11 has direct contact with the fluid 8.

[0057] According to Figure 2 to Figure 4 In the ultrasonic flow measurement device 1, the excitation structure 10 is formed by at least two rings spaced apart from each other in the axial extension direction of the measuring tube 2 and surrounding the measuring tube 2 in the circumferential direction. According to... Figure 2In the embodiment shown in Figure 3, the rings of the ultrasonic actuator 6 have different spacings from each other, and the ring spacing of the ultrasonic sensor 7 is different from the ring spacing of the ultrasonic actuator 6. Figure 2 According to Figure 4 In one embodiment, a different approach is used, where the spacing between the excitation structures 10, which are constructed as rings, is equidistant, thus offering advantages in manufacturing.

[0058] According to Figure 2 In the ultrasonic flow measurement device 1 of Figure 3, particularly great flexibility in terms of varying usage and boundary conditions is achieved, namely, the ring is a separate ultrasonic exciter 22, especially a separate piezoelectric element 13, and the ultrasonic exciter 22 can be individually controlled by the control and evaluation unit 5. Furthermore, the ultrasonic sensor 7 also incorporates a piezoelectric element 13, and the sensor signals of each acquisition structure 10 implemented as a piezoelectric element ring can be read individually.

[0059] Figure 5 Various excitation or acquisition structures 10, implemented as a toroidal piezoelectric element 13, are shown. According to... Figure 5 In the piezoelectric element 13 of a, the ring is contacted by the control and evaluation unit 5 via two opposing base surfaces 15 (axial mode). According to Figure 5 In the piezoelectric element 13 of b, the ring is contacted by the control and evaluation unit 5 via the inner and outer circumferential surfaces 14 of the ring (radial mode). Figure 5 c shows a ring-shaped piezoelectric element 13 having a layer 25, which is either designed as an adapter layer to better transmit ultrasonic waves (e.g., for use with...). Figure 2 and Figure 4 (for applications), or designed as an attenuation layer to prevent ultrasonic wave transmission (e.g., for applications based on...) Figure 7 and Figure 8 For applications where the bracket should also be directly installed at measuring tube 2 (not shown).

[0060] according to Figure 2 The multiple spaced-apart excitation structures 10 are achieved through the individual operability of the control and evaluation unit 5, which temporally staggers the excitation of multiple spaced-apart excitation structures 10 at multiple locations (viewed in the extension direction of the measuring tube 2). These excitations are performed such that they precisely induce the waveform of the ultrasonic wave 9, which propagates via the measuring tube 2 through which the fluid 8 flows, according to a predetermined wave pattern. The advantage of the time-variable and individual operability of the ring lies in its adaptability to changing operating conditions, such as when the fluid 8 changes or when only temperature changes.

[0061] According to Figure 4In the ultrasonic flow measurement device 1, multiple excitation structures 10 designed as loops are simultaneously controlled by the control and evaluation unit 5, which simplifies the design of the control and evaluation unit 5. In this case, the spacing between the individual loops must be chosen such that it accurately induces the waveform of the ultrasonic wave 9 propagating through the measuring tube 2 through which the fluid 8 flows in a predetermined wave mode.

[0062] According to Figure 2 In the ultrasonic flow measurement device 1, the ring of the ultrasonic actuator 6 is manipulated with a time delay in the direction toward the ultrasonic sensor 7, causing the ultrasonic wave 9 to be amplified in a predetermined wave mode in the direction toward the ultrasonic sensor 7. Conversely, in the direction opposite to the ultrasonic sensor 7, the generated wave amplitude is smaller because it does not superimpose in that propagation direction due to the time manipulation. Thus, significant directional selectivity is achieved.

[0063] According to Figure 2 The design of the ultrasonic transducer 4 in the ultrasonic sensor 7 achieves selective acquisition of a predetermined wave pattern by windowing or delaying the received signals provided by multiple acquisition structures 10 in time according to the propagation characteristics and wave pattern of the predetermined wave pattern. The signals acquired by two acquisition structures 10 of the ultrasonic sensor 7 can, for example, be added together, where the signal arriving first on the left side of the two acquisition structures 10 is delayed by an amount of time required for the ultrasonic signal 9 of the predetermined wave pattern to travel from the left side to the right side of the two acquisition structures 10. Only in the corresponding wave pattern can the signals be added based on the phase velocity depending on the wave pattern, thereby verifying the signal input in the expected and predetermined wave pattern based on the sum of the signal strengths.

[0064] Similarly, time windowing can be implemented, where signal inputs to the left of the two acquisition structures 10 trigger acquisition windows on the right side of the two acquisition structures 10. If no signal enters within this triggered window, the signal is not the ultrasonic wave 9 in the predetermined wave mode. This is based on the premise that the predetermined wave mode and its excitation frequency are carefully selected to achieve good distinguishability between the predetermined wave mode and other wave modes.

[0065] exist Figure 7 and Figure 8The ultrasonic flow measurement device 1 shown does not operate using a separate ring, but instead has a conical base 16 with a central notch 17 for accommodating a measuring tube 2. The inner wall 18 of the base 16, formed by the notch 17, is structured in the axial direction of the measuring tube 2 by recesses 19 extending circumferentially along the measuring tube 2. Protrusions 20 formed by the recesses 19 in the inner wall 18 of the base 16 form an excitation structure 10. An ultrasonic exciter 22 is arranged at the base surface 21 of the conical base 16, which feeds ultrasonic waves (indicated by arrows) into the conical base 16. The ultrasonic waves are at least partially reflected at the circumferential surface 23 of the conical base 16 and excited and guided by the protrusions 20 of the inner wall 18 of the base 16 within the measuring tube 2 through which the fluid 8 flows.

[0066] This implementation of the ultrasonic actuator 6 is slightly more constrained than that with a separate ring because the protrusion 20 is structurally robustly implemented in the conical base 16. Furthermore, the ultrasonic waves are generated solely by the ultrasonic actuator 22, which feeds the ultrasonic waves into the conical base 16, where they are distributed by reflection at the circumferential surface 23 in the base 16 and ultimately fed into the waveguide (measuring tube / fluid) via the protrusion 20 in the wall of the base 16.

[0067] Figure 6 illustrates an ultrasonic flow measurement device 1, in which an ultrasonic actuator 6 and / or an ultrasonic sensor 7 are implemented in multiple parts, allowing them to be radially inserted into a measuring tube 2. Specifically, the multiple parts are pivotally hinged to each other via one or more hinges 24. An adapter layer 25 is responsible for the optimal transmission of ultrasonic waves from the ultrasonic actuator 22 to the measuring tube 2 and to the fluid 8 within the measuring tube 2.

[0068] Figure 9 to Figure 1 1 illustrates a method 26 for determining at least one wave pattern generated during flow measurement in an ultrasonic flow measurement device 1. The ultrasonic flow measurement device 1 is an ultrasonic flow measurement device of the type described above, that is, it has a measuring tube 2, a first ultrasonic transducer 3, a second ultrasonic transducer 4, and a control and evaluation unit 5. The first ultrasonic transducer 3 and the second ultrasonic transducer 4 are arranged axially offset at the measuring tube 2, wherein the first ultrasonic transducer 3 is at least configured as an ultrasonic actuator 6, and the second ultrasonic transducer 4 is at least configured as an ultrasonic sensor 7. During operation of the ultrasonic flow measurement device 1, the control and evaluation unit 5 manipulates the ultrasonic actuator 6 such that guided ultrasonic waves 9 are excited in the measuring tube 2 through which fluid 8 flows.

[0069] The ultrasonic sensor 7 receives guided ultrasonic waves 9, and the control and evaluation unit 5 determines the flow velocity of the fluid 8 by evaluating the received guided ultrasonic waves 9. The ultrasonic transducer 3, designed as an ultrasonic actuator 6, has multiple excitation structures 10 in the axial extension direction of the measuring tube 2, wherein the excitation structures 10 are spaced apart from each other in the axial extension direction of the measuring tube 2. By means of the excitation structures 10, ultrasonic waves are fed into the measuring tube 2 through which the fluid 8 flows, such that the predetermined wave mode m_det of the guided ultrasonic waves 9 is excited in the measuring tube 2 in a spatially distributed manner in the axial extension direction of the measuring tube 2.

[0070] according to Figure 9 The method 26 is configured such that, for the geometric and physical boundary conditions bound of the measuring tube 2 through which the fluid 8 flows, the phase velocity c_ph and group velocity c_gr of the func(bound,f) acoustic wave in the frequency range are determined for multiple wave modes m. Such a wave mode is selected as a predetermined wave mode m_det, which obtains the highest evaluation eval_max at a specific frequency f_det within the frequency range when evaluating eval based on at least one of the following criteria krit: a) The smaller the difference between the phase velocity c_ph and the group velocity c_gr, the better. b) The closer the phase velocity c_ph and / or group velocity c_gr are to the speed of sound in the fluid, the better. c) The smaller the frequency dependence of phase velocity c_ph and group velocity c_gr, the better. d) The larger the minimum spacing in phase velocity c_ph between different modes m, the better; e) The larger the minimum spacing in the group velocity c_gr between different modes m, the better; f) The more axially symmetric the pattern m, the better.

[0071] g) The more similar the relative changes in phase velocity c_ph and / or group velocity c_gr are to the relative changes in the speed of sound of fluid 8, the better.

[0072] h) The smaller the amplitude attenuation of the mode as it propagates in the fluid, the better.

[0073] i) The more constant the amplitude of mode m is on the internal cross-section of measuring tube 2, the better.

[0074] Therefore, the result of this method is not only to determine the desired and thus predetermined wave pattern m_det, but also to determine the specific frequency f_det in which the predetermined wave pattern m_det is excited.

[0075] The significance of these standards has been explained in the general description section. Some of the standards are detailed in Figures 10 and 11.

[0076] Figure 10a The calculated phase velocity c_ph of the ultrasound is shown, and Figure 10b The calculated group velocity c_gr of the ultrasound is shown, with a frequency range of 0 to approximately 1 MHz. As boundary conditions, a straight measuring tube 2 made of a flexible perfluoroalkoxy polymer tube is chosen, having an outer diameter of 6.35 mm and an inner diameter of 4.35 mm. Furthermore, for water, a sound velocity of 1480 m / s and a fluid density of 1000 kg / m³ are assumed. For the external space of the measuring tube 2, air at normal pressure and temperature is assumed. This calculation does not depend on the specific design of the excitation structures 10, i.e., the spatial spacing between the excitation structures 10 and the possible time intervals in manipulating the excitation structures 10; it only concerns the wave modes that can propagate at a specific frequency of the excited wave under the selected geometric and physical boundary conditions of the measuring tube and the fluid.

[0077] As can be seen from Figure 10, both the phase velocity c_ph and the group velocity c_gr of wave mode m1 are close to the speed of sound of the fluid at 1480 m / s at a frequency of 480 kHz, which leads to good evaluations (plane wave) in criteria a) and b). Furthermore, mode m1 exhibits lower dispersion in both the phase velocity c_ph and the group velocity c_gr at this frequency, meaning that the phase velocity c_ph and the group velocity c_gr have lower dependence on the transmission wave frequency, and this also leads to good evaluations in criterion c).

[0078] At a frequency of 480 kHz, there is also a large gap between the phase velocity c_ph and the group velocity c_gr between wave mode m1 and the adjacent modes m2 and m3, which leads to good evaluation in terms of standard d) and g).

[0079] Not shown here but calculated, the relative changes in phase velocity c_ph and / or group velocity c_gr behave very similarly to the relative changes in the velocity of sound of fluid 8 (medium change), which leads to a good assessment in terms of standard g).

[0080] Overall, this observation yields a preferred result for wave mode m1, which is therefore selected as the predetermined wave mode m_det at a specific frequency f_det of 480 kHz, where wave mode m2 constitutes the interference factor due to its closest velocity. Utilizing the understanding that vibration mode m1 should be excited at the specific frequency f_det of 480 kHz, the excitation structure 10 can now be designed—based on the available degrees of freedom—in terms of its spatial arrangement along the axis of the measuring tube and / or in terms of its temporal excitation. In the current case, two excitation structures 10 with a spacing of 4.15 mm and an excitation delay of 2.74 microseconds were selected.

[0081] Here, it is helpful to answer the question of how the amplitudes of different modes m1 and m2 behave with each other under the same excitation, which cannot be derived from Figure 10. In particular, it is desirable that the amplitude of the predetermined mode be sufficiently high, for example, to achieve a good signal-to-noise ratio. For this purpose, the magnitude (or magnitude, i.e., Betrag) of the two-dimensional Fourier transform of the wavefunction is calculated as the amplitude A. ) This also incorporates the characteristics of the excitation structure, which in this case are two excitation structures with the mentioned spacing and the mentioned excitation delay.

[0082] Taking into account the design of the excitation structure 10, the two-dimensional Fourier transform of the generated ultrasonic wave is used. Module The magnitude A of the form—assuming the excitation is always the same—is encoded in grayscale and normalized to the 0 to 1 range in Figure 11.

[0083] Figure 11a The amplitude A of the generated ultrasonic wave is shown in relation to the direction of motion of the wave from the ultrasonic actuator 6 to the ultrasonic sensor 7. Conversely, Figure 11b The solution to the wave equation for the amplitude A of the ultrasonic wave generated by the ultrasonic actuator 6 moving away from the ultrasonic sensor 7 in the direction of motion (i.e., the opposite direction, away from the actual measurement segment) is shown.

[0084] In not only Figure 11a and Figure 11b In the middle, wave modes m1 and m2 both originate from... Figure 10a Transferred from the corresponding diagram. According to Figure 11a It can be clearly seen that wave mode m1 has a significantly higher amplitude in the direction toward the ultrasonic sensor 7 than the subfast wave mode m2, which greatly improves the temporal distinguishability of the two wave modes. Furthermore, the amplitude of wave mode m1 in the direction away from the ultrasonic sensor 7 is significantly suppressed compared to wave mode m2. Figure 11b This demonstrates that wave mode m1 provides good support for measurement tasks.

[0085] In this context, method 26 is configured such that, considering the geometric and physical boundary conditions of the measuring tube 2 through which the fluid 8 flows, and taking into account the design of the excitation structure 10, at least for a predetermined wave mode m_det, the amplitude A of the generated sound wave at the excitation frequency is determined based on the phase velocity c_ph of the generated sound wave within the frequency range, and if the amplitude A of a specific wave mode m_det does not reach a minimum value, the design of the excitation structure 10 is abandoned and modified. Here, the criterion for such a minimum value is that the amplitude A of a specific wave mode m_det (wave mode m1) must not be less than the amplitude A of an undesirable wave mode m2. This is not the case here, thus preserving the design of the excitation structure 10. If the result is unsatisfactory, the described checking process is repeated until a design of the excitation structure 10 that should no longer be abandoned is found.

[0086] A particularly simple way to implement method 26 is that the standard krit evaluation eval is performed by introducing the pattern m to be examined and studied according to the standard krit into the evaluation order rang and scoring it, and determining the best pattern as the specific pattern m_det based on the total score result sum_rang achieved.

[0087] If different criterions are given different levels of importance, these different criterions can be incorporated into the evaluation with different weights, which can be done very simply.

[0088] After executing method 26, the subordinate ultrasonic flow measurement device 1 operates in such a way that a predetermined wave mode m_det is excited using a specific frequency f_det within the frequency range. For this purpose, not only the excitation frequency but also the phase velocity of the predetermined wave mode should be considered, in the current case, the phase velocity of wave mode m1 at the specific frequency f_det of 480 kHz.

[0089] List of reference numerals 1. Ultrasonic flow measurement equipment 2 Measuring tube 3 First ultrasonic transducer 4 Second ultrasonic transducer 5. Control and Evaluation Unit 6. Ultrasonic actuator 7. Ultrasonic Sensor 8. Fluid 9. Guided ultrasound 10. Incentive Structure, Acquisition Structure 11 Contact Surface 12 Acoustic coupling components 13 Piezoelectric elements Circumference of the 14th ring 15 rings base surface 16 Conical Matrix 17. Central notch 18. Inner wall of the matrix 19. The concave part of the inner wall 20 Protrusions 21. Base surface of the conical matrix 22 Ultrasonic exciter 23. Peripheral surface of the conical base 24 Hinges 25 layers, adapter layer or attenuation layer 26 methods m_det Predefined wave mode m-wave mode c_ph phase velocity c_gr group velocity The geometric and physical boundary conditions of the measuring tube through which the fluid flows. f_det specific frequency Krit Standard Evaluation of eval standards eval_max is the highest evaluation A. The amplitude of the modulus of the two-dimensional Fourier transform of the wave function, considering the characteristics of the excitation structure. rang evaluation order sum_rang: Overall score result.

Claims

1. An ultrasonic flow measurement device (1) comprising a measuring tube (2), a first ultrasonic transducer (3), a second ultrasonic transducer (4), and a control and evaluation unit (5), wherein, The first ultrasonic transducer (3) and the second ultrasonic transducer (4) are arranged axially offset at the measuring tube (2), wherein the first ultrasonic transducer (3) is configured at least as an ultrasonic actuator (6), and the second ultrasonic transducer (4) is configured at least as an ultrasonic sensor (7). In the operating state of the ultrasonic flow measurement device (1), the control and evaluation unit (5) manipulates the ultrasonic actuator (6) such that guided ultrasonic waves (9) are excited in the measuring tube (2) through which fluid (8) flows, and the guided ultrasonic waves (9) propagate guidedly in the measuring tube (2) and the fluid (8) along the axial extension direction of the measuring tube (2) in a combined waveguide comprising the measuring tube (2) and the fluid (8). The ultrasonic sensor (7) receives the guided ultrasonic waves (9), and the control and evaluation unit (5) determines the flow velocity (v) of the fluid (8) by evaluating the received guided ultrasonic waves (9). Its features are, An ultrasonic transducer (3) designed as at least an ultrasonic actuator (6) has a plurality of excitation structures (10) in the axial extension direction of the measuring tube (2), wherein the excitation structures (10) are spaced apart from each other in the axial extension direction of the measuring tube (2), wherein ultrasonic waves are fed into the measuring tube (2) through which the fluid flows by means of the excitation structures (10), such that at least one predetermined wave mode (m_det) of the guided ultrasonic wave (9) is excited in the measuring tube (2) through which the fluid (8) flows in a spatially distributed manner in the axial extension direction of the measuring tube (2).

2. The ultrasonic flow measurement device (1) according to claim 1, characterized in that, The second ultrasonic transducer (4), configured as an ultrasonic sensor (7), is constructed in the same manner as the first ultrasonic transducer (3), configured as an ultrasonic actuator (6), such that the excitation structure (10) functions as an acquisition structure, especially the second ultrasonic transducer (4) being constructed in the same manner as the first ultrasonic transducer (3), configured as an ultrasonic actuator (6).

3. The ultrasonic flow measurement device (1) according to claim 1 or 2, characterized in that, The first ultrasonic transducer (3) is also configured as an ultrasonic sensor (7), and the second ultrasonic transducer (4) is also configured as an ultrasonic actuator (6). In particular, the control and evaluation unit (5) operates the first ultrasonic transducer (3) and the second ultrasonic transducer (4) such that the flow velocity (v) of the fluid (8) in the measuring tube (2) is determined by means of a time difference measurement.

4. The ultrasonic flow measurement device (1) according to any one of claims 1 to 3, characterized in that, The measuring tube (2) is mechanically rigid, especially made of metal, plastic, ceramic or glass, or the measuring tube is flexible, especially made of elastic plastic, especially made of perfluoroalkoxy polymer.

5. The ultrasonic flow measurement device (1) according to any one of claims 1 to 4, characterized in that, The measuring tube (2) is configured as an acoustic coupler (12) in the region of the excitation structure (10) to improve acoustic transmission from the excitation structure (12) to the fluid (8) in the measuring tube (2).

6. The ultrasonic flow measurement device (1) according to any one of claims 1 to 4, characterized in that, The measuring tube (2) is formed by the excitation structure (10) itself in the region of the excitation structure (10) to transmit sound directly from the excitation structure (10) to the fluid (8) in the measuring tube (2).

7. The ultrasonic flow measurement device (1) according to any one of claims 1 to 6, characterized in that, The excitation structure (10) is formed by at least two rings spaced apart from each other in the axial extension direction of the measuring tube (2) and surrounding the measuring tube (2) in the circumferential direction, wherein, in the case of at least three rings, the rings are equidistant from each other.

8. The ultrasonic flow measurement device (1) according to claim 7, characterized in that, The ring is a separate ultrasonic actuator, particularly a separate piezoelectric element (13), wherein the ultrasonic actuator can be individually operated by the control and evaluation unit (5).

9. The ultrasonic flow measurement device (1) according to claim 7 or 8, characterized in that, The ring is contacted by the control and evaluation unit (5) via the inner and outer circumferential surfaces (14) of the ring, or the ring is manipulated by the control and evaluation unit (5) via two opposing base surfaces (15).

10. The ultrasonic flow measurement device (1) according to any one of claims 7 to 9, characterized in that, The rings are supported in a common ring support, particularly connected to the common ring support via their outer peripheral surface (15), wherein the common ring support has at least partially a material that attenuates ultrasonic crosstalk between the rings.

11. The ultrasonic flow measurement device (1) according to any one of claims 7 to 10, characterized in that, The loop of the ultrasonic actuator (6) is manipulated in a time-delayed manner in the direction toward the ultrasonic sensor (7), such that the ultrasonic wave (9) is amplified in a predetermined wave mode in the direction toward the ultrasonic sensor (7).

12. The ultrasonic flow measurement device (1) according to any one of claims 7 to 11, further back to claim 2, is characterized in that, Selectivity in acquiring the waveform of the predetermined wave mode is achieved by having the received signals provided by a plurality of acquisition structures (10) be evaluated in time windowed or in time delayed according to the propagation characteristics and waveform of the predetermined wave mode.

13. The ultrasonic flow measurement device (1) according to any one of claims 1 to 6, characterized in that, The ultrasonic actuator (6) includes a conical base (16) with a notch (17) for receiving the center of the measuring tube (2), wherein the inner wall (18) of the base (16) formed by the notch (17) is structured in the axial extension direction of the measuring tube (2) by at least one recess (19) extending in the circumferential direction of the measuring tube (2), and at least two protrusions (20) formed by at least one recess (19) in the inner wall of the base (16) The excitation structure (10) is formed by arranging an ultrasonic exciter (22) on the base surface (21) of the conical base (16), the ultrasonic exciter feeding ultrasonic waves into the conical base (16), wherein the ultrasonic waves are at least partially reflected at the circumferential surface (23) of the conical base (16) and the guided ultrasonic waves (9) are excited in the measuring tube (2) through which the fluid (8) flows via a protrusion (20) on the inner wall (18) of the base (16).

14. The ultrasonic flow measurement device (1) according to claim 13, characterized in that, The ultrasonic exciter (22) is designed as a ring, particularly a ring piezoelectric element (13), wherein preferably, the ring piezoelectric element (13) is contacted by the control and evaluation unit (5) via the inner and outer circumferential surfaces (14) of the ring, or the ring piezoelectric element (13) is manipulated by the control and evaluation unit (5) via two opposing base surfaces (15).

15. The ultrasonic flow measurement device (1) according to any one of claims 1 to 14, characterized in that, The ultrasonic actuator (6) is implemented in multiple parts, which allows it to be radially inserted into the measuring tube (2), wherein the multiple parts are pivotally supported by one or more hinges (24).

16. The ultrasonic flow measurement device (1) according to any one of claims 1 to 15, characterized in that, The predetermined wave mode is determined by the method (26) according to any one of claims 17 to 21.

17. A method (26) for determining at least one wave pattern, said wave pattern being generated during flow measurement in an ultrasonic flow measurement device (1), wherein, The ultrasonic flow measurement device (1) includes a measuring tube (2), a first ultrasonic transducer (3), a second ultrasonic transducer (4), and a control and evaluation unit (5). The first ultrasonic transducer (3) and the second ultrasonic transducer (4) are axially offset at the measuring tube (2). The first ultrasonic transducer (3) is at least configured as an ultrasonic actuator (6), and the second ultrasonic transducer (4) is at least configured as an ultrasonic sensor (7). In operation of the ultrasonic flow measurement device (1), the control and evaluation unit (5) manipulates the ultrasonic actuator (6) such that guided ultrasonic waves (9) are excited in the measuring tube (2) through which the fluid (8) flows, and the guided ultrasonic waves (9) extend along the axial direction of the measuring tube (2) in a combined waveguide comprising the measuring tube (2) and the fluid (8). Guided propagation in the measuring tube (2) and fluid (8), wherein the ultrasonic sensor (7) receives the guided ultrasonic wave (9), and the control and evaluation unit (5) determines the flow velocity of the fluid (8) by evaluating the received guided ultrasonic wave (9), wherein the ultrasonic transducer (3), (4), designed at least as an ultrasonic actuator (6), has a plurality of excitation structures (10) in the axial extension direction of the measuring tube (2), wherein the excitation structures (10) are spaced apart from each other in the axial extension direction of the measuring tube (2), wherein the ultrasonic wave is fed into the measuring tube (2) through which the fluid (8) flows by means of the excitation structures (10), such that the wave type of the predetermined wave mode (m_det) of the guided ultrasonic wave (9) is excited in the measuring tube (2) through which the fluid flows in the axial extension direction of the measuring tube (2) in a spatially distributed manner. For the geometric and physical boundary conditions of the measuring tube (2) through which the fluid (8) flows, the phase velocity (c_ph) and group velocity (c_gr) of the sound wave in the frequency range are determined for multiple wave modes (m), and such wave modes are selected as predetermined wave modes (m_det) that obtain the highest evaluation (eval_max) at at least one of the following criteria (krit) at a specific frequency (f_det) in the frequency range: a) The smaller the difference between the phase velocity (c_ph) and the group velocity (c_gr), the better. b) The closer the phase velocity (c_ph) and / or the group velocity (c_gr) are to the speed of sound in the fluid, the better. c) The smaller the frequency dependence of the phase velocity (c_ph) and the group velocity (c_gr), the better. d) The larger the minimum spacing in the phase velocities (c_ph) between different modes (m), the better. e) The larger the minimum spacing in the group velocity (c_gr) between different modes (m), the better. f) The more axisymmetric the pattern (m) is, the better. g) The more similar the relative changes in the phase velocity (c_ph) and / or the group velocity (c_gr) are to the relative changes in the sound velocity of the fluid (8), the better. h) The smaller the amplitude attenuation of the mode as it propagates in the fluid, the better. i) The more constant the amplitude of the pattern (m) is on the internal cross-section of the measuring tube (2), the better.

18. The method (26) according to claim 17, characterized in that, Based on the found predetermined wave mode (m_det) and specific frequency (f_det), the design of the excitation structure (10) is selected, especially the spatial spacing between the excitation structures (10) along the axis of the measuring tube and / or the time interval of the excitation of the excitation structure (10).

19. The method (26) according to claim 18, characterized in that, Regarding the geometric and physical boundary conditions of the measuring tube (2) through which the fluid (8) flows, taking into account the design of the excitation structure (10), the amplitude (A) of the generated sound wave in the excitation frequency is determined according to the phase velocity (c_ph) of the generated sound wave in the frequency range for at least a predetermined wave mode (m_det), and if the amplitude (A) of a particular wave mode (m_det) does not reach a minimum value, especially if the amplitude (A) of the particular wave mode (m_det) is less than the amplitude (A) of an undesirable wave mode, the design of the excitation structure (10) is abandoned and modified, especially in which the process is repeated until a design of the excitation structure that should no longer be abandoned is found.

20. The method (26) according to any one of claims 17 to 19, characterized in that, The evaluation of the standard (krit) is thus carried out, that is, the observed pattern (m) studied according to the standard (krit) is introduced into the evaluation order (rang) and scored, and the best pattern is determined as the specific pattern (m_det) based on the obtained total score result (sum_rang).

21. The method (26) according to claim 20, characterized in that, Different criteria (krits) are incorporated into the evaluation with different weights.

22. The method (26) according to any one of claims 17 to 21, characterized in that, The specific frequency (f_det) within the frequency range is the frequency at which the specific mode (m_det) is excited.

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