EA040471B1 - FLOW MEASUREMENT - Google Patents

Description

Precedence of this application is claimed by Australian Provisional Application No. 2017/900133, filed January 17, 2017, the entire contents of which are incorporated herein by reference.

Technical field

The invention relates to the measurement of flow rate.

The invention is described below in relation to flow measurement of irrigation water, although embodiments of the invention are applicable in other contexts, such as flow measurement of gas flow.

Background of the invention

A common way to measure the flow of water flowing through a pipe is to install a pair of acoustic transducers facing each other to limit the acoustic path. The path crosses the hollow interior of the pipe at an angle of 45° relative to the central axis of the pipe and separates this axis. Each transducer sends signals along an acoustic path and receives signals along it. The travel time of these signals in each direction along the acoustic path can be determined, starting from the output of said transducers. The difference between said transit times may be related to the average axial velocity of the fluid inside the pipe.

The velocity calculation is based on the assumption that the flow is parallel to the central axis of the pipe and the flow profile is laminar. Using physical analysis, a corresponding logical algorithm is obtained.

In practice, these assumptions do not correspond to reality. Turbulence results in flow regimes with velocity components that are not parallel to the central axis and the flow profile is not completely laminar. Thus, turbulence inside the pipe reduces the accuracy of the measurement.

To improve accuracy, a second pair of acoustic transducers is usually used to limit the second acoustic path, which at the pipe center line intersects at 90° with the previously mentioned first acoustic path. The common plane occupied by the two acoustic paths coincides with the center line of the pipe and is called the measurement plane. Of course, not absolute geometric accuracy is needed, but only a practical degree of accuracy, and therefore, in the art and in the present description, the expression measurement plane and similar terminology are used. As an example, according to the wording used in this document and in relation to a pipe with a diameter of 500 mm, two acoustic paths that intersect each other within 1 mm lie in a common plane.

While the addition of a second acoustic path is an improvement, turbulence is still a source of error. Therefore, it is still desirable to minimize turbulence affecting the flowmeter. For this, they usually provide:

on the upstream side of the flowmeter, a straight section of pipe, the length of which is at least ten pipe diameters; and on the downstream side of the flowmeter, a straight section of pipe whose length is at least four pipe diameters.

In many applications, the installation of such straight pipe sections is costly and/or even greater accuracy is desirable.

In addition to these conventional solutions, the applicant has previously developed improvements, such as those described in international patent applications published as WO2011/020143 A1 and WO2016/004471 A1.

WO2011/020143 A1 (the contents of which are incorporated herein by reference) describes a system of acoustic transducers forming mutually spaced, mutually parallel measurement planes for flow estimation. In addition, a system of transducers is described, which forms three measurement planes for flow evaluation, which intersect the center line of the pipe at different angles, so that the circular cross section of the pipe is divided into six sectors.

WO2016/004471 A1 (the contents of which are incorporated herein by reference) describes a tubular cavity that is likewise divided into sectors by measurement planes. Next to the device of the converters and downstream, a gate valve is installed. System identification is used to establish the connection between the flow rate, the position of the gate valve and the output signals from the transducers.

The expression system identification refers to a well-known technique for obtaining a system model based on experimental data. This technique consists in proposing an appropriate mathematical representation for the model of the corresponding system and a subsequent tuning process, during which the specific representation is optimized to ensure the most accurate reproduction of the experimental, time-fixed, and system-derived observations. The technique provides a means of comparing different models and classifying them according to their ability to reproduce the behavior of the system. System identification is a special subsection in the theory of mathematical systems, as well as in statistics.

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Despite the improvements made in the past by the Applicant, the authors of the present invention recognize that further improvements are possible. Preferred embodiments of the present invention are aimed at providing improved accuracy and/or a simpler and more convenient design.

Reference in this specification to a patent document or other material which is cited as prior art is not to be taken as an admission or suggestion that the document or material was known or that the information contained therein was part of the common knowledge at the priority date of any of the claims. invention formulas.

The essence of the invention

According to one aspect of the invention, an acoustic transducer system is provided for a flow meter, wherein the flow meter is designed to measure flow through the passage of a fluid, the system comprising a corresponding set of transducers for each face of an imaginary regular polygon, the transducer sets interconnected with a fluid transfer tubular cavity, each the set of converters, respectively, includes:

two acoustic transducers oriented to form an acoustic path lying in the measurement plane of the corresponding set, and two other acoustic transducers oriented to form another acoustic path lying in the measurement plane of the corresponding set, while the transducer sets are arranged in such a way that in cross section, perpendicular to the tubular cavity, the measuring plane of each corresponding set of transducers coincides with the corresponding face of an imaginary regular polygon.

A regular polygon has a flat shape formed by a sequence of straight line segments (called faces or sides), is equiangular (all angles are equal when measured) and equilateral (all sides are the same length). Regular polygons can have a convex profile or a star shape. Examples of regular polygons with a convex profile are triangles, squares, pentagons, hexagons, etc. Pentagrams or hexagrams are examples of regular star-shaped polygons.

Preferably, the acoustic path of each respective set substantially intersects another acoustic path of the respective set. Most preferably, the acoustic path of each respective set is substantially perpendicular to the other acoustic path of the respective set. The imaginary regular polygon may be substantially concentric with respect to the tubular cavity, and preferably convex. Most preferably, the imaginary polygon is a square.

Preferably, the measurement planes are substantially parallel to the tubular cavity.

The system may comprise transducer blocks, with each corresponding block having said two acoustic transducers and including a mounting device by means of which the corresponding block is installed as a block.

The system may contain four additional acoustic transducers oriented to limit two acoustic paths lying in a plane coinciding with the center line of the tubular cavity.

Preferably, each upstream acoustic transducer of the sets and four additional acoustic transducers lies in an upstream plane transverse to the tubular cavity, and each downstream acoustic transducer of the sets and four additional acoustic transducers lies in a downstream plane, transverse tubular cavity.

According to one aspect of the invention, a hardware system is also provided, including said system of acoustic transducers and a sensor for detecting the level of a fluid in a tubular cavity.

In addition, according to one aspect of the invention, a flow meter assembly is provided, including the specified system and a housing that defines a tubular cavity and supports acoustic transducers.

The housing preferably defines a respective mounting surface portion for each of the acoustic transducers of the sets, each of the mounting surface portions respectively being substantially perpendicular to the respective extreme portion of an imaginary regular polygon.

According to one aspect of the invention, a flow meter is also provided, including the specified system and logic device for applying a sequence of logical operations to the output signals received from the transducers, to provide an indication of the flow rate of the fluid medium.

Preferably, the sequence of logical operations is determined at least in part as a result of system identification.

In addition, according to one aspect of the invention, there is provided a transducer assembly for a flow meter, wherein the flow meter is designed to measure the flow rate of a fluid flow, the transducer assembly comprising:

an acoustic transducer for supplying signals along an acoustic path and receiving signals along it, another acoustic transducer for supplying signals along another acoustic path and receiving signals along another specified path, and a mounting device by means of which a block of transducers can be installed as a block and in interconnection with a tubular cavity for fluid transfer, wherein the acoustic paths mutually diverge from the transducer unit relative to the mounting device in such directions that at least three upstream transducer units can interact with:

at least three downstream transducer units, and a casing defining a tubular cavity to form said system.

Preferably, the acoustic paths mutually diverge from the transducer bank at an internal angle of 60° such that the upstream four transducer banks can communicate with the four downstream transducer banks and the imaginary regular polygon is a square.

According to another aspect, a system of acoustic transducers is provided in a water irrigation flow meter that is designed to measure water flow, wherein the system includes a corresponding set of transducers for each face of an imaginary regular polygon, the transducer sets being interconnected to a water transfer tubular cavity, and each set of transducers , respectively, includes:

two acoustic transducers oriented relative to each other to limit the acoustic path and lying in the measurement plane of the corresponding set, and two other acoustic transducers oriented relative to each other to limit the other acoustic path and lying in the measurement plane of the corresponding set, with the transducer sets arranged in such a way that, in a cross section perpendicular to the tubular cavity, the measuring plane of each corresponding set of transducers coincides with the corresponding face of an imaginary regular polygon.

Brief description of the drawings

In the following, an embodiment of the device is described solely by way of example with reference to the accompanying drawings, in which:

in fig. 1 shows the flow meter assembly in axial section;

in fig. 2 shows the same node in end view;

in fig. 3 shows a perspective view of this node;

in fig. 4 is a perspective view of FIG. 3, at a sharper angle;

in fig. 5 is a perspective view of another flow meter assembly;

in fig. 6 shows the installed transducer block for the assembly shown in FIG. 5, in axial section;

in fig. 7 is a perspective view of another flow meter assembly;

in fig. 8 shows another flow meter assembly, in axial section;

in fig. 9 shows the assembly in end view;

in fig. 10 is a perspective view of the assembly shown in FIG. 9;

in fig. 11 is a perspective view of the assembly shown in FIG. 1 with a butterfly valve attached thereto;

in fig. 12 shows another flow meter assembly in vertical axial section;

in fig. 13 shows the specified node in a horizontal axial section; and in FIG. 14 is a perspective view of the assembly shown in FIG. 1 with a knife gate valve attached to the assembly.

Detailed description

In FIG. 1-4 illustrate a flow meter assembly 1 comprising a tubular body 3 and an acoustic transducer system 5.

The body 3 defines a tubular cavity through which water flows. In this case, the cavity has a diameter D. The housing 3 may have structural fasteners (such as mounting flanges) within the same diameter D upstream and downstream of the transducers, allowing the assembly to be easily mounted along the length of the pipe. Alternatively, the transducers may be installed in a different way, providing a measurement of the flow through the tubular cavity of the pipe itself. Variants of the proposed system can be used in the context of non-circular pipes.

System 5 contains three sets 7, 9, 11, 13 of acoustic transducers.

The preferred views of the system 5 are applicable to flow measurement in any direction, although in this case flow in the direction of the arrow Q in FIG. 1.

Set 7 includes transducers 7a, 7b, 7c, 7d, installed in close proximity to

3. One upstream transducer 7a cooperates with one downstream transducer 7b (FIG. 4) to limit the acoustic path passing diagonally through the flat upper chord of the tubular cavity of the housing 3. Another upstream transducer 7b located symmetrically with respect to transducer 7a on the other side of the vertical (as shown in the drawings) center line CL of the system, in the same transverse plane as transducer 7a and in the same axial plane as transducer 7d. Transducer 7b interacts with downstream transducer 7c to form a different acoustic path. Both acoustic paths formed by the set 7 lie in the common measurement plane MP ₇ . Thus, the transducers 7a, 7b, 7c, 7d are located at the corners of an imaginary square, through which the acoustic paths pass from corner to corner, diagonally.

Set 9 includes transducers 9a, 9b, 9c, 9d. Converter 9a is installed adjacent to converter 7a, and similarly converter 9c is installed adjacent to converter 7c. The transducers 9b, 9d are mounted vertically below the transducers 9a, 9c, respectively. The transducer 9a cooperates with the transducer 9d to limit the acoustic path LS _9,1 , which diagonally intersects the vertical chord of the interior of the housing 3. Similarly, the transducers 9b, 9c interact to form a second acoustic path LS _9,2 , which diagonally intersects the same the chord. Said paths are preferably mutually perpendicular, as shown in FIG. 1.

Paths AC ₉ ,1, LS ₉ ,2 lie in the common plane MP ₉ measurements. Similarly, sets 11 and 13 form the MRC, MP ₁₃ measurement planes.

In a section passing across the interior of the body 3 (corresponding to FIG. 2), each measurement plane extends along a corresponding face of an imaginary square NRP regular polygon. The vertices of the NRP polygon are formed by the points where two measurement planes intersect each other.

The exemplary system 5 further includes a set of 15 acoustic transducers 15a, 15b, 15c, 15d forming a crossover pair of acoustic paths coinciding with the central axis SL of the tubular interior of the housing 3 to define the central plane of the MRS measurement. In this example, the central plane of the MPC is horizontal.

The authors of the present invention found that the described design is advantageous from the point of view of calculations, and from a constructive point of view.

The acoustic transducers are configured to generate output signals to which logic operations can be applied to determine the average axial velocity of the fluid along each of the measurement planes. Although the ability to apply logic operations may vary from system to system and depends on the type of fluid, laboratory tests conducted by the inventors unexpectedly showed that accurate flow measurements can be obtained by applying logic operations to the output signal obtained from transducers, which were developed as a result of system identification.

It has been found that the described acoustic transducer system takes into account the helical flow conditions known as swirl to a greater extent than existing detection devices. Whirl is one of the manifestations of turbulence.

Conventional transit time based flow measurement uses acoustic paths that traverse the axis of the pipe and is based on assumptions about the flow profile within the pipe. The preferred acoustic transducer system described includes acoustic paths that do not intersect a central axis, providing the data needed to compensate for the swirl.

Preferred embodiments of the invention are particularly advantageous in the context of round pipes (ie pipes having a circular cross section) in which swirl is more of a problem.

Some of the design advantages of the proposed transducer system are best illustrated in relation to the system example shown in FIG. 5 and 6. For convenience, reference numbers for components similar to those shown in FIGS. 1-4 remain the same.

Each adjacent pair of transducers may be installed within a single transducer block, for example transducer block 17' may include transducers 7c, 9c. Thus, to accommodate sixteen transducers from sets 7, 9, 11 and 13, eight mutually identical transducer blocks can be installed, for example, the presented block 17 is similar to block 17'.

The transducer unit 17 also includes a mounting device in the form of a mounting plate 19, by means of which said unit 17 can be mounted as a unit and in relationship with the tubular interior of the housing 3. The mounting plate 19 is curved to conform to the outer surface of the housing 3 and has through holes 21 , through which appropriate fastening means can be passed to ensure interaction with complementary holes 23 formed in the wall of the housing 3, while the part 25 of the block on which the

- 4 040471 transducers, exits through a complementary hole 27 through the wall of the housing 3. The part 25, on which the transducers are mounted, supports a pair of transducers, such as transducers 7c, 9c, directed to work at given angles. Gasket 29 surrounds and compresses opening 27 to provide a seal against leakage through said opening.

With appropriate adjustments to the mounting device, the same transducer unit 17 can be used in pipes of different diameters.

In FIG. 7 shows another example of node 1, in which mutually adjacent acoustic transducers are separated from each other by means of ribs providing flow separation. In this example, the flow separation ribs run parallel to the tubular interior of the housing 3, for example a rib 30 separates the transducers 7a, 9a from each other, while a rib 31 separates the transducers 9b, 11b from each other. The fins provide flow straightening and also limit swirl and effects in the cross section of the flow. Opposite the ribs 30 and 31 are similar ribs 30a and 31a. The ribs 30, 31, 30a and 31a may be of any appropriate shape and generally extend beyond the height of the transducers to improve the straightening of the water flow.

Other types of construction providing flow separation are possible. In the example shown in FIG. 8 and 9, the transducers 7a, 9a are separated by a flow separation structure having the form of a longitudinal protrusion 33 defining a mounting surface 35 substantially perpendicular to the upper face of an imaginary rectangular polygon NRP, and on which the transducer 7a can be mounted. Likewise, the protrusion 33 defines a surface 37 for mounting the transducer 9a substantially perpendicular to the side face of the NRP polygon. This design allows all sixteen installation points of the kits to use a common transducer and transducer mounting device. A similar effect can be achieved if each transducer mounting surface has a different (namely, non-perpendicular) general orientation, as shown in FIG. 10 for the corresponding portion of an imaginary rectangular polygon. As shown in FIG. 10, the longitudinal projections 41 have inclined mounting surfaces 43, 54, as opposed to the perpendicular mounting surfaces 35, 37 shown in FIG. 9.

In the examples shown in FIG. 1-7, each of the acoustic paths covers a respective range of flow, and thus each pair of facing acoustic transducers includes an upstream transducer and a downstream transducer, for example, a pair of 9b, 9c includes an upstream transducer 9b located before downstream converter 9c.

In the illustrated examples, the upstream transducers lie in a common plane transverse to the interior of the housing 3, while the downstream transducers lie in another common transverse plane. This generality is not significant. As shown in FIG. 8-9, transducers adjacent to each other, such as transducers 7a, 9a, can be axially displaced relative to each other. Preferably, the acoustic paths intersect with at least one common plane passing across the tubular cavity of the housing 3, i. e. preferably dimension L as shown in FIG. 8 is at least zero.

In FIG. 12 and 13 show a flow meter assembly similar to that shown in FIG. 1. Compared to the embodiment shown in FIG. 1, additional acoustic sensors 15a, 15b, 15c, 15d are axially displaced inward towards the center of the system so that they are located in the upstream and downstream planes UP, DP, in which the acoustic transducers of the sets are also located. This offset reduces the overall length of the flow detection system. This offset causes the acoustic paths AC ₁₅ , ₁ , AC ₁₅ , ₂ to intersect at an angle other than the normally preferred 90° angle. However, given the output from the acoustic transducers included in the kits, accurate flow measurements can be obtained.

The system shown in Fig. 12 further includes a water level sensor 39 for detecting a water level WL in the pipe. In this example, sensor 39 is a top-mounted acoustic sensor that sends and receives reflected signals along the vertical acoustic path AC ₃₉ . Other water level detection systems are possible, for example, a bottom-mounted sensor may be provided. The water level may be expressed in terms of the height measured upwards from the bottom of the pipe, or in terms of the height measured downwards from the open part of the pipe, or in other terms.

Preferred types of flowmeter provide processing of data received from the acoustic transducers, as well as from the sensor 39 to provide the ability to measure flow in fully filled pipes, as well as in pipes that are only partially filled.

The examples shown in FIG. 1-10 and 12-13 relate to measuring cocurrent flow through the body or pipe 3. Embodiments may also include attaching a flow control device or a closure to allow water to flow through the device. Such devices can be installed anywhere along the pipe 3 or at its end, depending on

Claims (5)

depending on requirements. In FIG. 11 and 14 show the use of typical flow control devices used in the art, but are not limited to those devices as will be appreciated by those skilled in the art. In FIG. 11 shows a butterfly valve 51 attached to the end of pipe 3. This valve is fully described in the embodiments discussed in Australian Patent No. 2012234917, the contents of which are incorporated herein in their entirety to avoid repetition and duplication of description for the reader. A pair of hinged sealed semi-circular plates 53 (only one of the plates is visible in Fig. 11) can be raised and lowered by means of rotary racks 55 mounted on an axis in a rotary threaded element 57, which is part of the activation device 59. The motor 61 rotates the threaded element 57 under the action of program control. In addition, if necessary, the motor 61 can be replaced by a hand lever. In FIG. 14 shows a knife gate valve 63 attached to the end of pipe 3. This valve is fully described in the embodiments described in PCT Application Nos. for the reader. The gate valve 65, which is slidable in sealing contact within the frame 67, can be raised and lowered by a lifting mechanism 69 connected to said frame. The engine 71 operates under the action of software control, raising and lowering the shutter 65 of the valve. Moreover, if necessary, the motor 71 can be replaced by a hand lever. Specialists in the art understand that the ideas of the present invention may go beyond the described examples. The invention is not limited to the described examples; more precisely, the invention is defined by the claims. By way of example, some embodiments may be implemented without using the set 15, and while in this example the measurement planes corresponding to the sets are parallel to the interior of the tubular body, other embodiments may not be. In this example, there are ten mutually facing pairs of acoustic transducers corresponding to ten acoustic paths. It has been found that, compared to other flow measurement systems, this system provides flow measurements that are less affected by cross-sectional flow effects and other manifestations of turbulence. Of course, the principles described may not be limited to the imaginary square, extending to other regular polygons, such as imaginary regular polygons having the form of pentagons or pentagrams, in which case similar computational and design advantages can be realized. CLAIM 1. A system of acoustic transducers for a flow meter used in water irrigation and configured to measure the flow rate of water, while the system contains a corresponding set (7, 9, 11, 13) of transducers for each face of an imaginary regular polygon, characterized in that the sets ( 7, 9, 11, 13) transducers are installed in the tubular cavity (3) for water transfer, and each of these sets (7, 9, 11, 13), respectively, contains: two acoustic transducers (7a, 7b) oriented so as to form with each other only one acoustic path lying in the measurement plane (MP ₇ ) of the corresponding set, and two other acoustic transducers (7c, 7d) oriented so as to form only one acoustic path with each other another acoustic path lying in the measurement plane (MP7) of the corresponding set, wherein said sets of transducers are located in such a way that in the cross section perpendicular to the tubular cavity (3), the measuring plane of each corresponding set of transducers coincides with the corresponding face of the specified imaginary regular polygon, moreover, the specified system contains blocks (17) of transducers, each corresponding block supports two of the indicated acoustic transducers (7a, 9a) and contains an installation means (19), with the help of which the corresponding block is installed in the form of a node on the inner side of the wall of the tubular cavity and (3). 2. The system of claim 1, wherein the acoustic path of each respective set substantially intersects another acoustic path of the respective set. 3. A system according to claim 1 or 2, wherein the acoustic path of each respective set is substantially perpendicular to the other acoustic path of the respective set. 4. System according to claim 1, 2 or 3, wherein said imaginary regular polygon is essentially concentric with respect to the tubular cavity (3). 5. A system according to any one of claims 1 to 4, wherein said imaginary regular polygon is convex. -