Improved Ultrasonic Flowmeter

Abstract

An ultrasonic flow measurement system (1) includes a flow tube (11), an ultrasonic damping layer (12), an ultrasonic transmitter (13) covered by the ultrasonic damping layer, and an ultrasonic receiver (14) covered by the ultrasonic damping layer, characterized in that the ultrasonic damping layer includes: - a first damping portion (121) at least partially located between the ultrasonic transmitter and the ultrasonic receiver, and - a second damping portion (122) at least partially located between the ultrasonic transmitter and the ultrasonic receiver. Wherein, the first damping portion and the second damping portion of the ultrasonic damping layer are spaced apart from each other by a distance (d) in the axial direction (A) of the flow tube.

Description

[0001] Specification

[0002] The present invention relates to an ultrasonic flow measurement system, comprising:

[0003] - a flow tube for a fluid whose flow velocity is to be determined;

[0004] - an ultrasonic damping layer (or damping layer) provided on the outer side of the flow tube and substantially surrounding the flow tube, the speed of sound in the material of the flow tube being higher than the speed of sound in the material of the ultrasonic damping layer;

[0005] - an ultrasonic transmitter provided on the outer side of the flow tube and covered by the ultrasonic damping layer, the ultrasonic transmitter being configured to transmit an ultrasonic signal through the fluid in a transmission phase, and

[0006] - an ultrasonic receiver provided on the outer side of the flow tube and covered by the ultrasonic damping layer, the ultrasonic receiver being configured to receive the transmitted ultrasonic signal in a reception phase.

[0007] WO 2017 / 061870 A1 discloses, in the name of the same applicant, an ultrasonic flow measurement system comprising a flow tube, at least two ultrasonic transducer circuits, at least one receiving circuit, a control device and an ultrasonic damping layer. The flow tube is for a fluid whose flow velocity is to be determined. At least two ultrasonic transducer circuits are provided on the outer side of the flow tube, wherein at least one of the at least two ultrasonic transducer circuits comprises an ultrasonic transmitter configured to transmit an ultrasonic signal through the fluid in a transmission phase, and wherein at least another of the at least two ultrasonic transducer circuits comprises an ultrasonic receiver configured to receive the transmitted ultrasonic signal in a reception phase. The receiving circuit is for reading out the ultrasonic receiver in the reception phase. The control device is connected to the at least two ultrasonic transducer circuits and the at least one receiving circuit. The flow measurement system comprises an ultrasonic damping layer provided on an outer sheath of the flow tube, wherein the ultrasonic damping layer is provided to substantially surround the outer sheath of the flow tube and is in contact with both the ultrasonic transmitter and the ultrasonic receiver. The speed of sound in the flow tube material is significantly higher than the speed of sound in the ultrasonic damping layer material.

[0008] As explained in WO 2017 / 061870 A1, using a transmitter in contact with the flow tube causes the ultrasonic waves to propagate parallel to the longitudinal axis of the flow tube. Scholte waves occur at the interface between the solid (i.e., the flow tube) and the fluid (i.e., the fluid to be measured, liquid or gas). Stoneley waves occur at the interface between the solid (flow tube) and the solid (ultrasonic damping layer). Due to the different speeds of sound in the materials of the flow tube and the ultrasonic damping layer, at least some of the waves that do not interact with the fluid arrive at the receiver later than the waves that interact with the fluid, improving the signal-to-noise ratio and thus the measurement accuracy.

[0009] However, depending on the environment in which the measurement is carried out, the measurements achieved using the ultrasonic flow measurement system of WO 2017 / 061870 A1 may still not be optimal. Therefore, there is a need for an improved ultrasonic flow measurement system.

[0010] Accordingly, it is an object of the present invention to provide an improved ultrasonic flow measurement system. More specifically, it is an object of the present invention to provide an ultrasonic flow measurement system having a higher signal-to-noise ratio and / or a smaller size.

[0011] To achieve this object, an ultrasonic flow measurement system is provided according to the present invention, wherein the ultrasonic damping layer includes a first damping portion located at least partially between the ultrasonic transmitter and the ultrasonic receiver and a second damping portion located at least partially between the ultrasonic transmitter and the ultrasonic receiver. The first damping portion and the second damping portion of the ultrasonic damping layer are spaced apart from each other by a certain distance in the axial direction of the flow tube.

[0012] Therefore, when viewed in the axial direction of the flow tube, i.e., in the direction from the transmitter to the receiver (or vice versa), the ultrasonic damping layer is interrupted. In other words, the first damping portion and the second damping portion do not contact each other. In other words, there is a cut-off portion, a gap or a "void" between the first damping portion and the second damping portion.

[0013] The separation of the first damping portion from the second damping portion, i.e., the presence of a cut-off portion, a gap or a void in the axial direction of the flow tube, prevents "bulk acoustic waves", such as the Stoneley wave or at least a large part thereof, from reaching the receiver after they are emitted by the transmitter. Accordingly, the signal-to-noise ratio received by the receiver is improved, thus achieving the object of the present invention.

[0014] Furthermore, as will be explained in more detail below, compared with the prior art, the thickness and / or volume of the ultrasonic damping layer can be reduced while achieving a signal-to-noise ratio similar to that of the prior art. Therefore, the present ultrasonic flow measurement system can be miniaturized, which is of course beneficial if a small flow rate through a flow tube with a small diameter (e.g., 0.001 mm to 30 mm, or preferably 0.1 mm to 10 mm) is to be measured. However, a thinner ultrasonic damping layer is also beneficial for flow tubes with a larger diameter.

[0015] US 2012 / 222492 A1 discloses a system with an ultrasonic flowmeter. The ultrasonic flowmeter includes a first ultrasonic transducer disposed around a fluid flow path, and a pressure balancing system configured to pressure balance the first ultrasonic transducer relative to the fluid flow pressure along the fluid flow path. It should be noted that the present invention uses ultrasonic surface waves. An important function of the damping layer according to the present invention is to generate a solid-solid surface that forms a Stoneley wave, and to damp and delay the Stoneley wave. A Scholte wave appears at the interface between the solid and the fluid (i.e., the fluid to be measured, liquid or gas). A Stoneley wave appears at the interface between the solid (flow tube) and the solid (ultrasonic damping layer). Since the sound velocities in the flow tube and the ultrasonic damping layer materials are different, at least a part of the Stoneley wave that does not interact with the fluid (usually only partially damped) arrives at the receiver later than the Scholte wave that does interact with the fluid, thereby improving the signal-to-noise ratio and thus the measurement accuracy. US 2012 / 222492 A1 ensures that the transducers communicate only through the fluid in the conduit and does not describe the use of surface waves.

[0016] US 2014 / 311253 A1 discloses an ultrasonic sensor that includes: an annular ultrasonic vibrator disposed on the outer peripheral surface of a conduit through which a trace amount of substance flows, vibrating by applying a high-frequency signal and generating a high-frequency signal by receiving the vibration, and a pair of damping members arranged to grip and fix the ultrasonic vibrator, wherein an annular soft and uniform fitting member having a width along the conduit greater than the width of the ultrasonic vibrator is provided between the inner peripheral surface of the ultrasonic vibrator and the outer peripheral surface of the conduit, and the fitting member is made of a material having a sound propagation speed substantially equal to the sound propagation speed of the substance flowing in the conduit. US 2014 / 311253 A1 requires that the "vibrator" and the "damping members" be separated from the tube by the "annular soft and uniform fitting member", while the present invention requires direct contact between the transducer and the tube and between the damping layer and the tube. The "annular soft and uniform fitting member" of US 2014 / 311253 A1 does not allow direct contact between the transducer and the tube, thus interfering with the generation of ultrasonic surface waves. The "annular soft and uniform fitting member" is not applicable to devices using surface waves because it prevents direct contact between the transducer and the tube.

[0017] Preferably, the first and second damping portions do not contact each other anywhere in order to obtain the highest signal-to-noise ratio during measurement.

[0018] The fluid for which the flow rate is to be determined can be a liquid or a gas or a mixture, including suspensions, dispersions, solutions, emulsions, and aerosols.

[0019] Both the ultrasonic transmitter and the ultrasonic receiver are "covered" by an ultrasonic damping layer. That is, at least the crystal that receives and transmits signals is covered or surrounded by the ultrasonic damping layer. Of course, the wires or other components associated with the ultrasonic receiver and transmitter can extend from the ultrasonic damping layer. The ultrasonic damping layer can be made of one material, or it can be composed of multiple materials, such as fillers, optionally in multiple layers. Such layers can be substantially concentric.

[0020] In one embodiment, the distance is defined between the first end face of the first damping part and the second end face of the second damping part, both of whose end faces face the truncated part or void or gap, and the distance between them is less than 10 millimeters, such as about 9 millimeters or less, such as about 8 millimeters or less, 7 millimeters or less, or 6 millimeters or less. Although for larger devices, the distance may also be larger, such as about 30 millimeters or less, 20 millimeters or less or 15 millimeters or less. Preferably, the distance is less than 5 millimeters, such as between 0.1 millimeter and 5 millimeters, such as about 0.1 millimeter or about 0.5 millimeter, or about 1 millimeter. Since the first damping part and the second damping part are spaced apart from each other and do not contact each other, the distance between the facing end faces of the respective damping parts is greater than 0 millimeter. For practical reasons, it can be imagined that the distance is at least 0.5 millimeter, such as between 0.5 millimeter and 5 millimeters or between 0.5 millimeter and 10 millimeters.

[0021] A large distance between any transmitter and receiver will have a negative impact on the signal-to-noise ratio. The applicant has also found that an excessive distance between the first damping part and the second damping part will have a negative impact on the signal-to-noise ratio. Therefore, preferably, the distance between the first end face of the first damping part facing the truncated part and the second end face of the second damping part facing the truncated part is less than 90% of the distance between the receiver and the transmitter, such as less than 50%. Preferably, the distance between the first end face of the first damping part and the second end face of the second damping part is less than 10% of the distance between the receiver and the transmitter, more preferably less than 5%, such as 1% or even less.

[0022] In one embodiment, the first end face of the first damping part facing the truncated part has a substantially flat surface and / or the second end face of the second damping part facing the truncated part has a substantially flat surface. Preferably, each end face has a flat surface because this is easy to manufacture.

[0023] However, in an alternative embodiment, the first end face of the first damping portion facing the truncation portion has a curved shape, such as convex, concave, or sinusoidal, and / or the second end face of the second damping portion facing the truncation portion has a curved shape, such as convex, concave, or sinusoidal. Preferably, the shapes of the end faces are substantially mirror-symmetrical. For example, if one end face is convex, the other end face is preferably concave, such that the distance between the end faces is substantially constant at each cross-section of the ultrasonic damping layer. In yet another embodiment, both the first end and the second end have similar (curved) shapes, such as both being convex, concave, or sinusoidal.

[0024] In an embodiment where the end faces are flat, the angle between the axial direction of the flow tube and the first end face of the first damping portion facing the truncation portion is between 135° and 45°, particularly between 100° and 80°, and / or the angle between the axial direction of the flow tube and the second end face of the second damping portion facing the truncation portion is between 135° and 45°, particularly between 100° and 80°. Preferably, the angle between the second end face of the second damping portion facing the truncation portion and the axial direction of the flow tube is substantially equal to the angle between the first end face of the first damping portion and the axis of the flow tube, such that the distance between the two damping portions is the same in all cross-sections. Preferably, the angle between the axial direction of the flow tube and the first face of the first damping portion and the second face of the second damping portion is approximately 90°. If the above angles are different, preferably the first and second damping portions do not contact each other anywhere to obtain the highest signal-to-noise ratio during measurement.

[0025] In one embodiment, a truncation portion, gap, or "void" having at least semi-impermeable acoustic properties is provided between the first damping portion and the second damping portion of the ultrasonic damping layer. In the context of the present application, the term "at least semi-impermeable acoustic properties" means that each truncation portion has a relatively high acoustic penetration resistance, such that an acoustic signal cannot easily be transmitted from the first damping portion to the second damping portion, and only a small portion (e.g., less than half and preferably none at all) of the acoustic signal present in the first damping portion is transmitted to the second damping portion, and vice versa. This helps to improve the signal-to-noise ratio of the measurement system. It should be specifically noted that the phrase "at least semi-impermeable" includes the phrase "impermeable".

[0026] Examples of truncation portions having at least semi-impermeable acoustic properties are relatively vacuum (i.e., a truncation portion having a negative pressure relative to the environment), air truncation portions, and foam material truncation portions having a closed-cell structure. When the acoustic impermeable truncation portion consists of (relative) vacuum and / or includes air, it can be said that there is a "void" or "gap" between the first and second damping portions. When a foam material truncation portion (having a closed-cell structure) or another material is present between the first and second damping portions, it can be said that the "void" or "gap" is filled with foam material.

[0027] In one embodiment, the thickness of the ultrasonic damping layer is less than six times the radius of the flow tube. In prior art systems, this ratio is typically at least 10 or 20 in order to achieve a signal-to-noise ratio that allows for proper measurements. For the systems disclosed in the present disclosure, this ratio can be as low as 6 or less, thereby allowing for a thinner measurement system. The ultrasonic receiver and the ultrasonic transmitter are preferably always covered by the ultrasonic damping layer. Depending on the type of transmitter / receiver used and the radius of the flow tube, the ratio between the thickness of the ultrasonic damping layer and the radius of the flow tube may be higher or lower. Generally speaking: the thinner the flow tube, the higher this ratio.

[0028] In one embodiment, the distance between the ultrasonic receiver and the first end face of the first damping part facing the cut-off part and the distance between the ultrasonic receiver and the second end face of the second damping part facing the cut-off part are greater than 0.1 mm, and / or wherein the distance between the ultrasonic transmitter and the first end face of the first damping part facing the cut-off part and the distance between the ultrasonic transmitter and the second end face of the second damping part facing the cut-off part are greater than 0.1 mm. That is to say, the "gap" (empty or filled) and the distance between each ultrasonic receiver and the ultrasonic transmitter are preferably greater than 0.1 mm, for example greater than 0.5 mm, greater than 1 mm, greater than 5 mm and / or greater than 10 mm.

[0029] In one embodiment, the ultrasonic damping layer includes a third damping part, disposed between the first damping part and the second damping part and spaced apart from the first damping part and the second damping part in the axial direction of the flow tube. When the third damping part is present between the ultrasonic transmitter and the ultrasonic receiver (as viewed in the axial direction of the flow tube), it can be said that there are two "gaps" (filled or empty) between the ultrasonic transmitter and the ultrasonic receiver. If (in the case of two damping parts) a part of the signal is transmitted from the first damping part to the second damping part, then providing the third damping part between the first damping part and the second damping part may introduce a second "obstacle" to the signal compared to the case of only two damping parts, such that a smaller part of the signal is transmitted from the first damping part via the third damping part to the second damping part (and vice versa). Optionally, even more damping parts may be provided between the first damping part and the second damping part, such as a fourth damping part, a fifth damping part, etc.

[0030] In one embodiment, the ultrasonic flow measurement system further comprises at least one second ultrasonic transmitter and / or at least one second ultrasonic receiver, wherein the ultrasonic damping layer comprises at least one additional damping portion spaced apart from both the first damping portion and the second damping portion in the axial direction of the flow tube, wherein the additional damping portion is at least partially positioned between one of the ultrasonic receivers or ultrasonic transmitters and the at least one second ultrasonic transmitter or the at least one second ultrasonic receiver. This will be explained in more detail below with reference to the accompanying drawings.

[0031] In one embodiment, the ultrasonic damping layer is made of an epoxy resin material, preferably a dark color, for example, black. The ultrasonic damping layer can also be made of a potting material, such as epoxy resin or polyurethane.

[0032] In one embodiment, the ultrasonic flow measurement system further comprises an outer sleeve disposed outside the ultrasonic damping layer. For example, if the acoustically non-penetrable truncation portion consists of a relative vacuum, the sleeve can help maintain the relative vacuum in the space between the first damping portion and the second damping portion. In addition, the sleeve can ensure that the space between the first damping portion and the second damping portion remains uncontaminated, and contamination may gradually reduce the improved measurement accuracy. The outer sleeve is preferably thin, for example, having a thickness less than the thickness of the ultrasonic damping layer. Preferably, the outer sleeve has a low acoustic conductivity.

[0033] In one embodiment, the ultrasonic flow measurement system further comprises a receiving circuit arranged to read out the ultrasonic receiver during the receiving phase of the system.

[0034] In one embodiment, the ultrasonic flow measurement system further comprises a control device connected to the receiving circuit, the ultrasonic transmitter, and the ultrasonic receiver.

[0035] In one embodiment, the ultrasonic transmitter and / or the ultrasonic receiver is implemented as an ultrasonic transducer that can operate as both a transmitter and a receiver. This allows, for example, flow measurement in two directions, depending on the operating mode of the transducer.

[0036] In one embodiment, the ultrasonic transmitter and / or the ultrasonic receiver is formed as a ring oscillator, preferably covering the entire circumference of the flow tube. This allows measurement of the flow rate in the entire internal volume of the flow tube.

[0037] In one embodiment, the damping layer completely surrounds the flow tube in the circumferential direction. In particular, the ultrasonic transducers (transmitters and receivers) are also surrounded by the damping layer. In a preferred embodiment, the damping layer is approximately circular, or has other geometric shapes, such as approximately triangular, square, or hexagonal. The surface does not need to be smooth; the applicant has found that small deviations on the surface do not have a negative impact on performance, and surface roughness can improve performance.

[0038] The ultrasonic transducer is preferably in acoustic contact with the outer sheath of the flow tube, for example because it is directly connected thereto or is provided thereon via an acoustically conductive (preferably thin) layer.

[0039] The damping layer preferably extends in the circumferential direction of the entire flow tube. In this case, it can be said that the flow tube and the ultrasonic transducer are surrounded by a second larger tube made of the material of the ultrasonic damping layer. The inner side of the second larger tube formed by the damping layer is in complete contact with the partial outer sheath of the flow tube that extends between the outermost ultrasonic transducers. In a preferred embodiment, the damping layer has a substantially equal thickness in the circumferential direction at the position of the transducer. In another embodiment, the damping layer has a substantially equal thickness in the axial direction from the first end face to the second end at any part.

[0040] In one embodiment, the speed of sound in the material of the flow tube is greater than 2000 m / s, particularly greater than 2500 m / s, and more specifically between 3000 m / s and 7000 m / s.

[0041] In one embodiment, the speed of sound in the material of the ultrasonic damping layer is greater than 1000 m / s, particularly greater than 1500 m / s, and more specifically between 2000 m / s and 3000 m / s.

[0042] In one embodiment, the flow measurement system is designed to measure the flow rate of a fluid having a speed of sound in the range of 1000 m / s and 2000 m / s. At this time, the speed of sound in the ultrasonic damping layer material is between 2000 m / s and 3000 m / s, and the speed of sound in the flow tube material is greater than 3000 m / s. Preferably, the flow measurement system is designed such that the speed of sound of each of the damping layer, the flow tube, and the flow rate to be measured is significantly different from each other, for example, differing by approximately 500 m / s or even 1000 m / s. For example, if the system is designed for a fluid with a speed of sound of about 1800 m / s, the speed of sound of the damping layer may be about 2300 m / s, while the speed of sound of the flow tube material may be about 3300 m / s.

[0043] In one embodiment, the difference between the speed of sound in the flow tube and the speed of sound in the damping layer can be of the same order of magnitude, and even substantially the same as the difference between the speed of sound in the damping layer and the speed of sound in the flow rate to be measured. For example, if the speed of sound in the flow tube is about 4500 m / s and the speed of sound in the damping layer can be designed to be about 3000 m / s, then this flow measurement system is suitable for a medium with a speed of sound in the range of 1000 m / s to 2000 m / s, particularly a medium with a speed of sound of about 1500 m / s.

[0044] In one embodiment, each of the ultrasonic transmitter and the ultrasonic receiver is an ultrasonic transducer arranged to transmit an ultrasonic signal through the fluid during its respective transmission phase and to receive a signal transmitted from the other ultrasonic transducer during its respective reception phase. In this way, the transducer can be alternately excited to transmit ultrasonic waves, which are detected by the other unexcited oscillator. The time required for the ultrasonic waves to propagate upstream, the time required for the new ultrasonic waves to propagate downstream, and the time difference therebetween are used to determine the flow velocity and / or mass flow rate in the flow tube. For this purpose, advantageously, the flow measurement system includes a multiplexer circuit arranged to selectively connect the at least one receiving circuit to one of the at least two ultrasonic transducers. In one embodiment, the at least two transducers are arranged to alternately transmit the ultrasonic signal, and the multiplexer circuit is arranged to alternately connect each of the at least one receiving circuits to one of the non-transmitting ultrasonic transducers. Time delays, time errors, and / or time offsets occurring in at least one receiving circuit adversely affect the accuracy of the flow velocity measurement. In the case where the flow measurement system includes a multiplexer circuit, these time delays, time errors, and / or time offsets can be compensated, i.e., filtered out, the multiplexer circuit being arranged to selectively connect the at least one receiving circuit to one of the non-transmitting transducers.

[0045] In one embodiment, the damping layer comprises epoxy resin or a composite thereof. The damping layer can also be made of a potting compound, preferably comprising or consisting of epoxy resin, polyurethane, or a composite material. The ultrasonic damping layer can be made of cured epoxy resin, particularly selected from bisphenol A epoxy resin, bisphenol F epoxy resin, phenolic epoxy resin, aliphatic epoxy resin, and glycidylamine epoxy resin. The epoxy resin can be cured by homopolymerization or by an epoxy hardener selected from amines, acid anhydrides, phenols, and thiols. In one embodiment, the damping layer can be a potting material, preferably epoxy resin or a composite thereof, or polyurethane or a polyurethane composite, and the flow tube can comprise a material other than (stainless) steel, Teflon, PEEK, glass, or ceramic. In another embodiment, the epoxy resin can be colored, preferably black. In yet another embodiment, the damping layer can comprise a potting material, preferably epoxy resin or a composite thereof, or polyurethane or a polyurethane composite, and / or can comprise multiple layers. For example, these layers can be defined in the radial or axial direction. These layers can be concentric. There can also be a layer in direct contact with the receiver or transmitter and different layers elsewhere. In an alternative embodiment, the damping layer can be made of any material other than epoxy resin or a composite thereof. As previously mentioned, the damping layer can be made of a potting material, preferably epoxy resin or a composite thereof, or polyurethane or a polyurethane composite.

[0046] Suitable materials for the flow tube can be metals, such as (stainless steel) steel pipes. Other materials for the flow tube can also be considered, such as Hastelloy, or non-metals, such as polytetrafluoroethylene, PEEK, glass or ceramic materials. In one embodiment, the flow tube is a metal, such as (stainless steel) steel pipe, Hastelloy, or a non-metal, such as polytetrafluoroethylene, PEEK, glass or ceramic materials, and the damping material is a material without epoxy resin or its composite.

[0047] In one embodiment, the damping layer is designed such that in use, the speed of sound in the damping layer material substantially exceeds the speed of sound in the fluid whose flow rate is to be determined.

[0048] In a relatively simple embodiment that is relatively easy to manufacture, the ultrasonic transducer (i.e., ultrasonic receiver and / or ultrasonic transmitter) includes a piezoelectric element. The piezoelectric element can include a relatively thin piezoelectric film. Alternatively, polyvinylidene fluoride or polyvinylidene fluoride (PVDF) material can be used. PVDF has a very strong piezoelectric effect and is particularly suitable for generating voltage when the material is set to vibrate. In addition, it is conceivable to use PZT (lead zirconate titanate) elements, a ceramic crystal that can be used as a transmitter and / or receiver.

[0049] In one embodiment of the present invention, the assembly of the flow tube, ultrasonic transmitter and ultrasonic receiver is completely molded in the epoxy resin or epoxy resin composite as described above, or in another potting material including polyurethane or polyurethane composite, while ensuring a certain distance between the first damping part and the second damping part, and the device for connecting the tube to the outside world remains uncovered. In this way, an improved ultrasonic flowmeter can be provided in a relatively easy and cost-effective manner. The above components can be inserted into a hollow tube mold, and then the uncured epoxy resin or epoxy resin composite or another potting material including polyurethane or polyurethane composite can be poured between the components and the inner sheath of the tube mold. After curing, the tube mold can be removed.

[0050] In one embodiment, the ultrasonic transducer (ultrasonic transmitter and receiver) is at least substantially completely disposed around the flow tube. In this way, a substantially rotationally symmetric signal is obtained, and if the flow is not completely uniform, the average value of the flow will be substantially determined.

[0051] In one embodiment, the flow tube is a straight tube to achieve a substantially uniform flow in the flow tube.

[0052] The present invention will now be explained in more detail by describing several feasible embodiments as shown in the accompanying drawings. In the drawings:

[0053] Figure 1is a schematic isometric view of an ultrasonic flow measurement system according to the present invention, in which the ultrasonic damping layer is omitted to clearly show the other components of the system;

[0054] Figure 2 is a schematic cross-sectional view of a first embodiment of an ultrasonic flow measurement system according to the present invention;

[0055] Figure 3 is a schematic cross-sectional view of a second embodiment of an ultrasonic flow measurement system according to the present invention;

[0056] Figure 4 is a schematic cross-sectional view of a third embodiment of an ultrasonic flow measurement system according to the present invention; and

[0057] Figures 5a and 5b show measurement results obtained using an ultrasonic flow measurement system of the prior art and an embodiment of an ultrasonic flow measurement system according to the present invention.

[0058] Figure 1 shows an embodiment of an ultrasonic flow measurement system 1, in which the ultrasonic damping layer is omitted to more clearly show the other components of the system 1. As Figure 1 shown, the ultrasonic flow measurement system 1 includes a flow tube 11, a first ultrasonic transducer 13, here in the form of a first ultrasonic transmitter, and a second ultrasonic transducer 14, here in the form of a first ultrasonic receiver. The ultrasonic flow measurement system 1 may further include a third ultrasonic transducer 16, here for example in the form of a second ultrasonic receiver, respective acoustic conduction layers 131, 141, 161 associated with one of the ultrasonic transducers 13, 14, 16, respective electrical connections 132, 142, 162 associated with one of the ultrasonic transducers 13, 14, 16, and a controller 22.

[0059] The flow tube 11 of the ultrasonic flow measurement system 1 is for a fluid whose flow velocity is to be determined. The fluid can be a gas or a liquid or a mixture, including suspensions, dispersions, solutions, emulsions, and aerosols, and flows through the flow tube 11. The ultrasonic flow measurement system 1 may be most suitable for measuring the flow velocity of a gas. The flow tube 11 has an inlet I, an outlet O, and an outer side 111. The "normal" flow direction of the fluid in the flow tube 11 will be from the inlet I to the outlet O. The flow tube 11 is preferably straight, at least in the part where the ultrasonic flow measurement system 1 is provided. The radius of the flow tube 11 can be, for example, between 0.1 mm and 10 mm, for example between 1 mm and 10 mm or for example between 0.5 mm and 1 mm. The axial direction of the flow tube 11 is denoted by the reference numeral A.

[0060] The ultrasonic flow measurement system 1 includes at least one ultrasonic transmitter 13 and at least one ultrasonic receiver 14. Preferably, both the transmitter 13 and the receiver 14 are embodied as more general ultrasonic transducers, with at least two transducers spaced apart from each other. An ultrasonic transducer is a device that can be used at least as a transmitter or a receiver (or both simultaneously). Thus, when the ultrasonic flow measurement system 1 is described herein as including at least one receiver 14 and at least one transmitter 13, this means that when the system is in use and includes at least two transducers, at least one transducer operates in the transmit mode (i.e., as a transmitter), and at least one transducer operates in the receive mode (i.e., as a receiver).

[0061] The ultrasonic transmitter 13 is arranged on the outer side 111 of the flow tube 11 for transmitting an ultrasonic signal through the fluid during the transmission phase (transmit mode). Associated with the ultrasonic transmitter 13 is an acoustic conduction layer 131, which is arranged between the crystal of the transmitter 13 and the outer side 111 of the flow tube 11 to optimally transmit the acoustic signal emitted by the transmitter to the internal volume of the flow tube 11 to reach the fluid contained therein, such that the acoustic signal can ultimately be carried by the fluid. Further associated with the ultrasonic transmitter is a wiring 132 connecting the transmitter 13 and the controller 22, such that signals (e.g., steering signals) can be sent from the controller 22 to the transmitter 13 and / or vice versa. Although this figure shows physical wiring, it should be noted that signals between the transmitter 13 and the controller 22 can of course alternatively be sent via a wireless communication device (and the same applies to signals between the controller 22 and any other receiver / transmitter / transducer).

[0062] The ultrasonic receiver 14 is arranged on the outer side 111 of the flow tube 11 for receiving the ultrasonic signal emitted (and carried by the fluid) by the ultrasonic transmitter 13 during the reception phase (receive mode). Associated with the ultrasonic receiver 14 is an acoustic conduction layer 141, which is arranged between the crystal of the receiver and the outer side 111 of the flow tube 11 to optimally receive the acoustic signal present in the internal volume of the flow tube 11. The ultrasonic receiver 14 is a wiring 142 connecting the receiver 14 and the controller 22, such that signals (e.g., steering signals or signals corresponding to the received measurement) can be sent from the controller 22 to the receiver 14 and / or vice versa.

[0063] A third ultrasonic transducer 16, which is configured here, for example, to operate as a second ultrasonic receiver, is provided on the outer side 111 of the flow tube 11 and is configured to receive, in a receiving phase (receiving mode), ultrasonic signals that have been emitted by the ultrasonic transmitter 13 (and carried by the fluid). Associated with the ultrasonic receiver 16 is an acoustic conduction layer 161, which is arranged between the crystal of the receiver 16 and the outer side 111 of the flow tube 11 to optimally receive the acoustic signals present in the internal volume of the flow tube 11. Further associated with the ultrasonic receiver 16 is a wiring 162 that connects the receiver 16 and the controller 22, such that signals (e.g., steering signals or signals corresponding to received measurement results) can be sent from the controller 22 to the receiver 16 and / or vice versa. Advantageously, by providing two ultrasonic receivers 14, 16, more accurate fluid flow measurements can be performed, since now two signals can be measured and errors can be minimized. That is to say, any measurement inherently has an error range. By making two measurements and averaging the error ranges, a more accurate measurement can be obtained.

[0064] It should be noted that the third transducer 16 can alternatively operate as an ultrasonic transmitter, for example, and can also measure the flow rate when the flow direction is reversed (e.g., when the fluid flows in the direction from the outlet O to the inlet I). The receiver 14 can then, for example, receive the signals emitted by the transmitter 16.

[0065] Further optionally, even more transducers can be provided. For example, more than one transmitter can be provided, such as two, three, four, or even more transmitters, and / or more than one receiver can be provided, such as two, three, four, or even more receivers.

[0066] Alternatively, the second transducer 14 and the first transducer 13 can operate as ultrasonic transmitters, while the third transducer operates as an ultrasonic receiver. The receiver then receives the signals emitted by both the first transmitter and the second transmitter. In other words, the ultrasonic flow measurement system 1 can include two transmitters and at least one, for example, one, two, or three receivers.

[0067] The controller 22 is arranged to communicate with each of the transducers 13, 14, 16 and is configured to control the operation of the ultrasonic flow measurement system, such as steering and / or manipulation.

[0068] Now turning Figure 2 to, similar components are denoted by the same reference numerals and will not be described in detail again.

[0069] Compared with Figure 1 Figure 2Shows an ultrasonic damping layer 12, for example, made of an epoxy resin material preferably in a dark color, such as black. The ultrasonic damping layer 12 is provided on the outer side 111 of the flow tube 11 and substantially surrounds the flow tube 11. The thickness t12 of the ultrasonic damping layer 12 is preferably less than 6 times the radius r11 of the flow tube 11. In this regard, it should be noted that these drawings are not necessarily drawn to scale. That is, in embodiments of the present invention, the radius r11 of the flow tube 11 can be much smaller (or much larger) than depicted here compared to the thickness t12 of the ultrasonic damping layer 12. The speed of sound in the material of the flow tube 11 is higher than the speed of sound in the material of the ultrasonic damping layer 12. The ultrasonic damping layer 12 covers the ultrasonic transmitter 13 and the ultrasonic receiver 14.

[0070] The ultrasonic damping layer 12 at least includes a first damping portion 121 and a second damping portion 122, which are spaced apart by a distance d in the axial direction A of the flow tube 11. That is, the first damping portion 121 includes a first end face 1211 and a second end face 1212 facing a cut-off portion, gap or void (i.e., facing the cut-off portion), and the second damping portion 122 also includes a first end face 1221 and a second end face 1222 facing the cut-off portion, gap or void, wherein the first end face 1211 of the first damping portion 1211 facing the cut-off portion faces and is spaced apart from the second end face 1222 of the second damping portion 122 facing the cut-off portion, so that a cut-off portion 15 having at least semi-impermeable acoustic properties is defined therebetween.

[0071] For example, the cut-off portion 15 may consist of a relative vacuum, include air, and / or include a foam material having a closed-cell structure.

[0072] Each of the first damping portion 121 and the second damping portion 122 is positioned to respectively surround the ultrasonic transmitter 13 and the ultrasonic receiver 14, so that when viewed from the axial direction A of the flow tube 11, the cut-off portion 15 having semi-impermeable acoustic properties is positioned between the transmitter 13 and the receiver 14.

[0073] All end faces 1211, 1212, 1221, 1222 of all damping portions 121, 122 here have flat surfaces. A first angle α1 is defined between the first end face 1211 of the first damping portion facing the cut-off portion and the longitudinal axis A of the flow tube 11. A second angle α2 is defined between the second end face 1222 of the second damping portion facing the cut-off portion and the longitudinal axis A of the flow tube 11. Preferably, the angles α1, α2 are the same and approximately 90°. For example, the angles α1, α2 are respectively between 135° and 45°, especially between 100° and 80°, such as 90°.

[0074] The distance d between the first damping part 121 and the second damping part 122 is defined between the first end face 1211 of the first damping part 121 facing the cut-off part and the second end face 1222 of the second damping part 122 facing the cut-off part (which faces the first end face 1211 of the first damping part 121). Preferably, the distance is less than 10 mm, for example less than 5 mm, for example between 0.5 mm and 5 mm.

[0075] The distance between the ultrasonic transmitter 13 and the cut-off part 15 having at least semi-impermeable acoustic properties is preferably greater than 0.1 mm, for example greater than 5 mm. That is, the distance d131 between the ultrasonic transmitter 13 and the first end face 1211 of the first damping part 121 facing the cut-off part is preferably greater than 0.1 mm, while the distance d132 between the ultrasonic transmitter 13 and the second end face 1222 of the second damping part 122 facing the cut-off part is also preferably greater than 0.1 mm.

[0076] The distance between the ultrasonic receiver 14 and the cut-off part 15 having at least semi-impermeable acoustic properties is preferably greater than 0.1 mm. That is, the distance d142 between the ultrasonic receiver 14 and the first end face 1211 of the first damping part 121 facing the cut-off part is preferably greater than 0.1 mm, while the distance d141 between the ultrasonic receiver 14 and the second end face 1222 of the second damping part 122 facing the cut-off part is also greater than 0.1 mm.

[0077] Now turning to Figure 3 , similar components are again denoted by the same reference numerals and will not be described in full detail again. Figure 3 Angles and distances are not marked in Figure 2 to make the figure easier to understand. However, the angles and distances can of course be defined in the same way between different components of the ultrasonic flow measurement system 1 as described with reference to

[0078] Figure 3 Differences from Figure 2 are that the third damping part 123 of the ultrasonic damping layer 12 is arranged between the first ultrasonic transmitter 13 and the first ultrasonic receiver 14 in Figure 3 . Seen from the axial direction A of the flow tube 11, the third damping part 123 is spaced apart from both the first damping part 121 and the second damping part 122. In other words, the first end face 1231 of the third damping part 123 does not contact the second end face 1222 of the second damping part 122 facing the cut-off part, and the second end face 1232 of the third damping part 123 does not contact the first end face 1211 of the first damping part 121 facing the cut-off part. Therefore, two cut-off parts 15 having at least semi-impermeable acoustic properties are arranged here between the ultrasonic receiver 14 and the ultrasonic transmitter 13.

[0079] Figure 3 And Figure 2 Another difference between Figure 3 is that a third ultrasonic transducer 16 is provided in Figure 1 which is also shown in Figure 1 and has been described with reference to

[0080] Due to the presence of an additional ultrasonic transducer 16, here the third ultrasonic transducer 16, which can be, for example, a receiver or a transmitter, there is also an additional damping portion, here the fourth damping portion 124. The fourth damping portion 124 is spaced apart from the first damping portion 121 and the second damping portion 122 (and also from the third damping portion 123 here) in the axial direction A of the flow tube 11 to define a cut-off portion 15 having at least semi-impermeable acoustic properties between the second damping portion 122 and the fourth damping portion 124. The fourth damping portion 124 is at least partially positioned between the third transducer 16 and the ultrasonic receiver 14 such that the cut-off portion 15 is also positioned between the third transducer 16 and the ultrasonic receiver 14 (when viewed in the axial direction A of the flow tube 11).

[0081] Figure 3 Further shown in

[0082] is that the second end face 1242 of one of the damping portions (here the fourth damping portion 124) facing the cut-off portion can be curved, here convex. Additionally, the first end face 1221 of one of the damping portions (here the second damping portion 122) can be curved, here concave. The shapes of a pair of end faces 1242, 1221 facing the cut-off portion match each other such that the distance d between the end faces 1242, 1221 is constant over any cut-off portion of the ultrasonic damping layer 12. Although the curved shapes are shown here as concave or convex, of course other curved shapes are conceivable.

[0082] Also visible in Figure 3 is the outer sleeve 20 of the ultrasonic flow measurement system 1, which is arranged outside the ultrasonic damping layer 12. The outer sleeve 20 can be provided, for example, to allow for a relative vacuum to exist in the cut-off portion 15.

[0083] Now turning to Figure 4 similar components are again denoted by the same reference numerals and will not all be described in detail again.

[0084] Figure 4Four ultrasonic transducers 13, 14, 16, 17 are shown, but it can well be imagined that the ultrasonic flow measurement system 1 according to the invention includes more than four ultrasonic transducers. The four ultrasonic transducers may for example include a first ultrasonic transmitter 13, a second ultrasonic transmitter 17, a first ultrasonic receiver 14 and a second ultrasonic receiver 16. Then, in Figure 4 In an embodiment of, when viewed in the axial direction A of the flow tube 11, the two transmitters are followed by the two receivers.

[0085] However, multiple receivers and transmitters may also be provided in a "mixed" order, for example, when viewed in the direction from the inlet I to the outlet O, they are in turn transmitter, receiver, transmitter and receiver.

[0086] Alternatively, for example, it may also be three receivers and one transmitter, or three transmitters and one receiver. Or three receivers and two transmitters and so on.

[0087] Between two adjacent ultrasonic transducers 13, 14, 16, 17, at least one cut-off part 15 having semi-impermeable acoustic properties is preferably provided. Each cut-off part 15 is defined by the corresponding end faces of the damping parts 121, 122, 124, 125 of the ultrasonic damping layer 12.

[0088] However, when two adjacent ultrasonic transducers are of the same type, for example, both are transmitters or both are receivers, there is no need for a cut-off part 15 having semi-impermeable acoustic properties between them per se. On the other hand, when two adjacent ultrasonic transducers are of different types, for example, one transmitter and one receiver, it is highly recommended to use a cut-off part 15 having semi-impermeable acoustic properties between them.

[0089] In Figure 4 In an embodiment of, a first angle α1 between the end face of the fifth damping part 125 and the axial direction A of the flow tube 11 is less than 90°, while a second angle α2 between the end face of the first damping part 121 and the axial direction A of the flow tube 11 is greater than 90°. However, as shown in the figure, although the angle values are different, the distance d between the end faces is constant, which is preferred.

[0090] However, a constant distance between two end faces facing each other is not necessary per se. That is, as shown at the end faces 1222 and 1211 for example, they both face a gap, void or cut-off part, where the end faces are conical and the distance between them is greater on the outer side of the ultrasonic damping layer 12 than on the inner side. However, also on the inner side, the end faces 1222, 1211 are spaced apart.

[0091] Although the end faces 1222, 1211 facing the truncated part may be conical and have a flat surface, they may also be conical and have a curved shape, as shown, for example, between the end faces 1221, 1242 of the first damping part 121 and the third damping part 124 facing the truncated part.

[0092] Turning now to FIGS. 5a and 5b, a comparative test between the prior art measurement system of WO 2017 / 061870 A1 (FIG. 5a) and an embodiment of the measurement system according to the present invention (FIG. 5b) is shown. The embodiment of the measurement system according to the present invention is made by creating a 1 mm gap between an ultrasonic transmitter and an ultrasonic receiver in a device as described in the prior art, which has been previously used to record the data depicted in FIG. 5a. The ultrasonic transmitter is set to emit ultrasonic waves, and the ultrasonic receiver is set to receive the signals of the transmitter using standard electronic settings. A counter records time in arbitrary units. It can be clearly seen that, compared to a system without a truncated part, gap or void (FIG. 5a), the setup of the ultrasonic flow measurement system with a truncated part, gap or void (FIG. 5b) records a significantly better signal-to-noise ratio.

[0093] Those skilled in the art will understand that the present invention has been explained above with reference to preferred embodiments of the present invention. However, the present invention is not limited to these embodiments.

[0094] Therefore, various modifications can be made to the present invention within the framework of the present invention without departing from the spirit of the present invention. The scope of protection sought is defined in the appended claims.

[0095] List of reference numerals

[0096] 1 – Ultrasonic flow measurement system

[0097] 11 – Flow tube

[0098] 111 – Outer side of the flow tube

[0099] 12 – Ultrasonic damping layer

[0100] 121 – First damping part

[0101] 1211 – First end face of the first part facing the truncated part

[0102] 1212 – Second end face of the first part

[0103] 122 – Second damping part

[0104] 1221 – First end face of the second part

[0105] 1222 – Second end face of the second part facing the truncated part

[0106] 123 – The third damping part

[0107] 1231 – The first end face of the third part

[0108] 1232 – The second end face of the third part

[0109] 124 – Another damping part

[0110] 1241 – The first end face of the said another part

[0111] 1242 – The second end face of the said another part facing the truncated part 125 – Another damping part

[0112] 1251 – The first end face of the said another part facing the truncated part

[0113] 1252 – The second end face of the said another part

[0114] 13 – The first ultrasonic transmitter

[0115] 131 – The acoustic conduction layer

[0116] 132 – The wiring

[0117] 14 – The first ultrasonic receiver

[0118] 141 – The acoustic conduction layer

[0119] 142 – The wiring

[0120] 15 – The truncated part with at least semi - impenetrable acoustic properties

[0121] 16 – The second ultrasonic receiver

[0122] 161 – The acoustic conduction layer

[0123] 162 – The wiring

[0124] 17 – The second ultrasonic transmitter

[0125] 172 – The wiring

[0126] 20 – The outer sleeve

[0127] 22 – The controller

[0128] A – The axial direction of the flow tube

[0129] O – The outlet opening of the flow tube

[0130] I – The inlet opening of the flow tube

[0131] d – The distance between the first end face of the first damping part and the second end face of the second damping part

[0132] d131 – The distance between the first end face of the first damping part and the first emitter

[0133] d132 – The distance between the second end face of the second damping part and the first emitter

[0134] d141 – The distance between the second end face of the second damping part and the first receiver

[0135] d142 – The distance between the first end face of the first damping part and the first receiver

[0136] r11 – The radius of the flow tube

[0137] t12 – The thickness of the ultrasonic damping layer

[0138] α1 – The angle between the first end face of the first damping part and the axial direction of the flow tube

[0139] α2 – The angle between the second end face of the second damping part and the axial direction of the flow tube

Claims

1. An ultrasonic flow measurement system (1), comprising: - A flow tube (11) for a fluid whose flow velocity is to be determined; - An ultrasonic damping layer (12) provided on the outer side (111) of the flow tube (11) and substantially surrounding the flow tube (11), the speed of sound in the material of the flow tube (11) being higher than the speed of sound in the material of the ultrasonic damping layer (12); - An ultrasonic transmitter (13) provided on the outer side (111) of the flow tube (11) and covered by the ultrasonic damping layer (12), the ultrasonic transmitter (13) being configured to transmit an ultrasonic signal through the fluid in a transmission phase, wherein a Stoneley wave appears at the interface between the flow tube (11) and the ultrasonic damping layer (12), and - An ultrasonic receiver (14) provided on the outer side (111) of the flow tube (11) and covered by the ultrasonic damping layer (12), the ultrasonic receiver (14) being configured to receive the transmitted ultrasonic signal in a reception phase, characterized in that the ultrasonic damping layer (12) comprises: - A first damping part (121) at least partially located between the ultrasonic transmitter (13) and the ultrasonic receiver (14), and - A second damping part (122) at least partially located between the ultrasonic transmitter (13) and the ultrasonic receiver (14), wherein the first damping part (121) and the second damping part (122) of the ultrasonic damping layer (12) are spaced apart from each other by a distance d in the axial direction (A) of the flow tube (11) by a truncated portion, wherein the truncated portion prevents the Stoneley wave or at least a large part thereof from reaching the ultrasonic receiver (14) after being emitted by the ultrasonic transmitter (13), and the flow tube (11) is a continuous flow tube (11), and the distance d is defined between a first end face (1211) of the first damping part (121) facing the truncated portion and a second end face (1222) of the second damping part (122) facing the truncated portion, the second end face (1222) of the second damping part (122) facing the first end face (1211) of the first damping part (121), the distance d being less than 10 mm, or wherein at least one truncated portion (15) having at least semi-impermeable acoustic properties is provided between the first damping part (121) and the second damping part (122) of the ultrasonic damping layer (12).

2. The ultrasonic flow measurement system according to claim 1, wherein, The distance d is less than 5 mm.

3. The ultrasonic flow measurement system according to claim 1, wherein, The distance d is between 0.1 mm and 5 mm.

4. The ultrasonic flow measurement system according to claim 1, wherein, The first end face (1211) of the first damping part (121) facing the truncated portion has a flat surface and / or wherein the second end face (1222) of the second damping part (122) facing the truncated portion has a flat surface.

5. The ultrasonic flow measurement system according to claim 4, wherein, The angle α1 between the axial direction (A) of the flow tube (11) and the first end face (1211) of the first damping part (121) facing the truncated part is between 135° and 45°, and / or the angle α2 between the axial direction (A) of the flow tube (11) and the second end face (1222) of the second damping part (122) facing the truncated part is between 135° and 45°.

6. The ultrasonic flow measurement system according to claim 5, wherein, The angle α1 is between 100° and 80°.

7. The ultrasonic flow measurement system according to claim 5, wherein, The angle α2 is between 100° and 80°.

8. The ultrasonic flow measurement system according to claim 5, wherein, The angle α2 is 90°.

9. The ultrasonic flow measurement system according to claim 1, wherein, The first end face (1211) of the first damping part (121) facing the truncated part has a curved shape, and / or the second end face (1222) of the second damping part (122) facing the truncated part has a curved shape.

10. The ultrasonic flow measurement system according to claim 9, wherein, The curved shape is convex, concave or sinusoidal.

11. The ultrasonic flow measurement system according to claim 9, wherein, The truncated part (15) consists of relative vacuum.

12. The ultrasonic flow measurement system according to claim 9, wherein, The truncated part (15) includes air.

13. The ultrasonic flow measurement system according to claim 1, wherein, The truncated part (15) includes a foam material with a closed-cell structure.

14. The ultrasonic flow measurement system according to claim 1, wherein, The thickness (t12) of the ultrasonic damping layer (12) is less than 6 times the radius (r11) of the flow tube (11).

15. The ultrasonic flow measurement system according to claim 1, wherein, The distance (d142) between the ultrasonic receiver (14) and the first end face (1211) of the first damping part (121) facing the truncated part and the distance (d141) between the ultrasonic receiver (14) and the second end face (1222) of the second damping part (122) facing the truncated part are greater than 0.1 mm, and / or the distance (d131) between the ultrasonic transmitter (13) and the first end face (1211) of the first damping part (121) and the distance (d132) between the ultrasonic transmitter (13) and the second end face (1222) of the second damping part (122) are greater than 0.1 mm.

16. The ultrasonic flow measurement system according to claim 1, wherein, The ultrasonic damping layer (12) includes a third damping part (123) disposed between the first damping part (121) and the second damping part (122) and spaced apart from the first damping part (121) and the second damping part (122) in the axial direction (A) of the flow tube (11).

17. The ultrasonic flow measurement system according to claim 1, comprising at least one second ultrasonic transmitter (17) and / or at least one second ultrasonic receiver (16), wherein the ultrasonic damping layer (12) includes at least one additional damping part (124, 125) spaced apart from the first damping part (121) and the second damping part (122) in the axial direction (A) of the flow tube (11), and wherein the additional damping part (124, 125) is at least partially positioned between one of the ultrasonic receiver (14) or the ultrasonic transmitter (13) and the at least one second ultrasonic transmitter (17) or the at least one second ultrasonic receiver (16).

18. The ultrasonic flow measurement system according to claim 4, wherein, The two flat surfaces have the same shape.

19. The ultrasonic flow measurement system according to claim 1, further comprising an outer sleeve (20) disposed outside the ultrasonic damping layer (12).

20. The ultrasonic flow measurement system according to any one of the preceding claims 1 to 19, wherein, The ultrasonic damping layer (12) comprises a potting material.

Images