WO2009074162A1

WO2009074162A1 - Ultrasonic type fluid flow measurement apparatus

Info

Publication number: WO2009074162A1
Application number: PCT/EP2007/010751
Authority: WO
Inventors: Morten Storgaard Nielsen
Original assignee: Siemens Aktiengesellschaft
Priority date: 2007-12-10
Filing date: 2007-12-10
Publication date: 2009-06-18

Abstract

The present invention provides an apparatus (10, 100) for measuring a flow characteristic of a fluid (92, 192) flowing through a conduit. The apparatus (10, 100) comprises a tube (12, 112) forming a portion of said conduit and comprising hexagonal corners (50-60, 150-160). Each of the hexagonal corners (50-60, 150-160) is defined by two surfaces (62-84, 162-172) adapted for clamping on a transducer thereto. The apparatus (10, 100) further includes a plurality of pairs of transducers (14-36, 114-136) clamped on exteriorly to the tube (12, 112) on said surfaces (62-84, 162-172). These pairs of transducers (14-36, 114-136) comprise means for transmitting ultrasonic energy for propagation therebetween, and said pairs of transducers used for measuring said flow characteristic in dependance on the propagation time. The transducers (14-36, 114-136) of each of said pairs are located in relative upstream-downstream positions along the tube (12, 112), defining a chordal measurement path (38-48, 138-148) therebetween through said fluid (92, 192).

Description

ULTRASONIC TYPE FLUID FLOW MEASUREMENT APPARATUS

The present invention relates to fluid flow measurement and in particular to ultrasonic measurement of a flow rate of a fluid flowing through a conduit.

An ultra-sound based flow measurement device, also referred to as an ultra-sound flow-meter, is a device used for measuring flow characteristics, such as the flow-rate of a fluid flowing through a conduit. The measurement principle primarily involves measurement of velocity of the fluid based upon propagation times of ultrasonic energy emitted and received by a pair of transducers located at relative upstream-downstream positions along the conduit.

Based upon construction, ultra-sound flow-meters may be classified as those comprising spool-piece type transducers and those comprising clamp-on type transducers. Spool-piece transducers are wetted transducers that can be installed by drilling and tapping the conduit, which typically comprises a cylindrical tube, at the points of measurement. Spool-piece type flow-meters suffer from the disadvantage causing a disturbance in the fluid flow since the transducers are in direct contact with the flowing fluid. Further the associated manufacturing and installation costs of spool-piece type flow-meters are much higher than the clamp-on type.

A clamp-on type flow-meter uses ultra-sound transducers that are attached to the outer periphery of the conduit, to make measurements from the exterior of the conduit. This construction is relatively simple, and advantageously obviates the problems associated with the wetted transducers. However, clamp-on type ultra-sound flow-meters usually function as one path meter, i.e. capable of measurement only along the center-plane of the conduit. This is because of the inherent limitations of ultrasonic refraction at the surface of the conduit. One path measurements result in bad linearity and poor adjustments to odd installation conditions.

It is an object of the present invention to provide an improved apparatus for fluid flow measurement.

The above object is achieved by an apparatus for measuring a flow characteristic of a fluid flowing through a conduit, said apparatus comprising: - a tube forming a portion of said conduit and comprising hexagonal corners, each of said hexagonal corners being defined by two surfaces adapted for clamping on a transducer thereto, and - a plurality of pairs of transducers clamped on exteriorly to the tube on said surfaces, said pairs of transducers comprising means for transmitting ultrasonic energy for propagation therebetween, and said pairs of transducers used for measuring said flow characteristic in dependance on the propagation time, wherein the transducers of each of said pairs are located in relative upstream-downstream positions along the tube, defining a chordal measurement path therebetween through said fluid.

The underlying idea of the present invention is to use both surfaces of the hexagonal corners for clamping on the transducers, so as to provide multiple path out-of-plane flow measurements using a clamp-on type flow-meter, which was not possible hitherto as discussed above. The proposed design provides easy manufacture, and is also less costly than an ordinary spool-piece type flow-meter.

In one embodiment, said tube is generally cylindrical and comprises bulges on the circumference thereof that provide the surfaces that define said hexagonal corners. The bulges can be advantageously formed on an existing cylindrical fluid carrying tube, and hence provide an inexpensive design. In another embodiment, said tube has a hexagonal cross- sectional profile. The sides of the hexagon provide suitable surfaces for clamping on the transducers to the tube.

In a particularly preferred embodiment, the flow characteristic is measured along six chordal paths defined between six pairs of transducers clamped on to the surfaces defining said hexagonal corners of the tube. Such multiple path measurements provide better linearity than that of one- path flow-meters and also allows for lesser dependence on installation.

The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1 is a schematic sectional front view of a flow measurement apparatus having a cylindrical tube with bulges defining hexagonal corners for clamping on transducers thereto,

FIG 2 is a schematic longitudinal sectional view of the apparatus shown in FIG 1,

FIG 3 is a schematic sectional front view of a flow measurement apparatus having a hexagonal tube for clamping on transducers thereto, and

FIG 4 is a schematic longitudinal sectional view of the apparatus shown in FIG 3.

The embodiments described herein below provide an apparatus which enables the use of clamp-on type ultra-sound transducers for multiple path out-of-plane measurement of a fluid flow characteristic. In accordance with the principles of the invention, the conduit carrying the fluid comprises a tube having hexagonal corners, each corner being defined by two surfaces. Both surfaces of the hexagonal corners are used for clamping a transducer, such that each pair of these clamped-on transducers define, between themselves, a chordal measurement path through the fluid. Specific embodiments of the above-described idea are illustrated below.

Referring jointly to FIG 1 and FIG 2, a flow measurement apparatus 10 (also referred to as a flow-meter) is illustrated for measurement of a flow characteristic, such as a flow-rate of a fluid 92, according to one embodiment of the present invention. FIG 1 is a cross-sectional view of a section I-I of the apparatus 10 indicated in FIG 2. FIG 2 represents a longitudinal sectional view of a section II-II of the apparatus 10 indicated in FIG 1.

The fluid 92 is shown to flow in a direction represented by arrows 86 and 88 in FIG 2, through a conduit. The portion of the conduit where the flow measurement is intended to be made comprises a tube 12 having hexagonal corners 50, 52, 54, 56, 58 and 60. In this embodiment, the tube 12 is generally cylindrical, having bulges at various points along its circumference that define these hexagonal corners 50, 52, 54, 56, 58 and 60. Each of the hexagonal corners is formed by two surfaces. For example, the corner 50 is defined by surfaces 62 and 64, the corner 52 is defined by surfaces 66 and 68, the corner 54 is defined by surfaces 70 and 72, the corner 56 is defined by surfaces 74 and 76, the corner 58 is defined by surfaces 78 and 80, and the corner 60 is defined by surfaces 82 and 84. Each of the above surfaces that define the hexagonal corners provides a suitable surface adapted for clamping on a transducer thereto.

For ultrasonic measurement of flow rate of the fluid 92, multiple pairs of transducers are clamped to the exterior of the tube 12, the transducers of each pair being located in relative upstream-downstream positions along the tube 12, and defining , between themselves, a measurement path through the fluid 92. As illustrated, using the proposed design, six such pairs of transducers may be clamped on to the tube 12 on the surfaces mentioned above. Thus, as shown, the pair of transducers 14 and 24 are clamped on to surfaces 62 and 72 respectively, defining a measurement path 38 between themselves through the fluid 92. Other pairs include the pair of transducers 16 and 30 that are clamped on to surfaces 64 and 78 respectively defining a measurement path 46 therebetween, the pair of transducers 18 and 28 that are clamped on to surfaces 66 and 76 respectively defining a measurement path 42 therebetween, the pair of transducers 20 and 34 that are clamped on to surfaces 68 and 84 respectively defining a measurement path 40 therebetween, the pair of transducers 22 and 32 that are clamped on to surfaces 70 and 80 respectively defining a measurement path 44 therebetween, and the pair transducers 36 and 26 that are clamped on to surfaces 82 and 74 respectively defining a measurement path 48 therebetween. It should be noted that the transducers of each pair are clamped on to surfaces that are parallel to each other. This provides appropriate mounting of the transducers for measurement along these measurement paths while taking into account the inherent properties of ultrasonic refraction at the surface of the tube 12.

As in case of conventional ultra-sound transducers, the transducers of each pair comprise ultrasonic energy emitters and receivers, i. e. means for transmitting ultrasonic energy for propagation between the respective transducers. The pairs of transducers are used for measuring said flow characteristic in dependance on the propagation time of the ultra-sonic energy waves through the fluid 92. The propagation time of these ultrasonic waves is indicative of the velocity of the fluid 92 along a plane containing the pair. In accordance with the shown embodiment of the present invention, the six pairs of transducers may be used to measure fluid velocity along six planes of measurement. Unlike in case of conventional clamp-on type flow-meters, in the present embodiment, the planes of measurement do not pass through the center of the conduit. Such measurements that are not along the center-plane of the conduit are also referred to as out-of-plane measurements. Since the six measurement paths 38, 40, 42, 44, 46 and 48 do not pass through the center plane of the tube 12, they are also referred to as chordal measurement paths. As used herein, the term ^vchordal measurement path' , or ^λchordal path' is defined as a flow measurement path across a conduit that does not pass through the center plane of the conduit.

The flow-rate of the fluid 92 may be computed by integrating the velocity information obtained along these multiple measurement paths with respect to the cross-sectional area of the tube 12. Such multiple path measurements of flow rate provide better linearity than that of one-path flow-meters and also allows for lesser dependence on installation.

The above described design thus provides a six-path flow meter that is less complex easier to manufacture than existing spool-piece type flow-meters. The bulges can be advantageously formed on an existing cylindrical fluid carrying tube, and hence provide an inexpensive design.

Alternately, the tube having bulges that define hexagonal corners may be manufactured separately, and inserted between an existing fluid carrying tube at a desired measurement location, so as to form a continuous conduit for fluid flow. Another advantage of the present invention lies in the fact that the transducers and their electronics are based upon existing clamp-on flow-meters and thus may be used in the present invention without substantial modification. Also, as mentioned above, the multi-path design enables less dependence on installations, and further allows the undisturbed upstream and downstream length to be shorter.

Referring now jointly to FIG 3 and FIG 4, a flow measurement apparatus 100 is illustrated for measurement of a flow characteristic, such as a flow-rate of a fluid 192, according to another embodiment of the present invention. FIG 3 is a cross-sectional view of a section III-III of the apparatus 100 indicated in FIG 4. FIG 4 represents a longitudinal sectional view of a section IV-IV of the apparatus 100 indicated in FIG 3.

The fluid 192 is shown to flow in a direction represented by arrows 186 and 188 in FIG 4, through a conduit. The portion of the conduit where the flow measurement is intended to be made comprises a tube 112 having hexagonal corners 150, 152, 154, 156, 158 and 160. In this embodiment, the tube 112 comprises a hexagonal cross-sectional profile. Each of the hexagonal corners is defined by two adjacent surfaces of the hexagonal tube 112. For example, the corner 150 is defined by surfaces 162 and 164, the corner 152 is defined by surfaces 164 and 166, the corner 154 is defined by surfaces 166 and 168, the corner 156 is defined by surfaces 168 and 170, the corner 158 is defined by surfaces 170 and 172, and the corner 160 is defined by surfaces 172 and 162. Each of the surfaces 162, 164, 166, 168, 170 and 172 provides a suitable surface adapted for clamping on a transducer thereto.

As in the earlier embodiment, multiple pairs of transducers are clamped to the exterior of the tube 112, for ultrasonic measurement of flow rate of the fluid 192. The transducers of each pair are located in relative upstream-downstream positions along the tube 112, and defining, between themselves, a measurement path through the fluid 192. As illustrated, in this embodiment, six such pairs of transducers may be clamped on to the tube 12 on the surfaces mentioned above. Thus, as shown, the pair of transducers 114 and 124 are clamped on to surfaces 162 and 168 respectively, defining a measurement path 138 between themselves through the fluid 192. Other pairs include the pair of transducers 116 and 130 that are clamped on to surfaces 164 and 170 respectively defining a measurement path 146 therebetween, the pair of transducers 118 and 128 that are clamped on to surfaces 164 and 170 respectively defining a measurement path 142 therebetween, the pair of transducers 120 and 134 that are clamped on to surfaces 166 and 172 respectively defining a measurement path 140 therebetween, the pair of transducers 122 and 132 that are clamped on to surfaces 166 and 172 respectively defining a measurement path 144 therebetween, and the pair of transducers 136 and 126 that are clamped on to surfaces 162 and 168 respectively defining a measurement path 148 therebetween. It should be noted that the transducers of each pair are clamped on to surfaces that are parallel to each other. This provides appropriate mounting of the transducers for measurement along these measurement paths while taking into account the inherent properties of ultrasonic refraction at the surface of the tube 112.

The transducers shown in FIG 3 and FIG 4 are functionally similar to the transducers illustrated in FIG 1 and FIG 2 and are capable of performing out-of-plane velocity and flow-rate measurements as described earlier. As in the earlier described embodiment, the six measurement paths 138, 140, 142, 144, 146 and 148 do not pass through the center plane of the tube 112 and are hence, chordal measurement paths. The flow-rate of the fluid 192 may be computed by integrating the velocity information obtained along these multiple measurement paths with respect to the cross-sectional area of the tube 112.

The above described embodiment provides an alternative design to provide six-path path out-of-plane flow measurements in accordance with the underlying idea of the present invention, and hence provides the same advantages mentioned earlier.

Summarizing, the present invention provides an apparatus for measuring a flow characteristic of a fluid flowing through a conduit. The apparatus comprises a tube forming a portion of said conduit and comprising hexagonal corners. Each hexagonal corner is defined by two surfaces adapted for clamping on a transducer thereto. The apparatus further includes a plurality of pairs of transducers clamped on exteriorly to the tube on said surfaces. These pairs of transducers comprise means for transmitting ultrasonic energy for propagation therebetween, and said pairs of transducers used for measuring said flow characteristic in dependance on the propagation time. The transducers of each of said pairs are located in relative upstream-downstream positions along the tube, defining a chordal measurement path therebetween through said fluid.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

Claims

Patent claims

1. An apparatus (10, 100) for measuring a flow characteristic of a fluid (92, 192) flowing through a conduit, said apparatus (10, 100) comprising:

- a tube (12, 112) forming a portion of said conduit and comprising hexagonal corners (50-60, 150-160), each of said hexagonal corners (50-60, 150-160) being defined by two surfaces (62-84, 162-172) adapted for clamping on a transducer thereto, and

- a plurality of pairs of transducers (14-36, 114-136) clamped on exteriorly to the tube (12, 112) on said surfaces (62-84, 162-172), said pairs of transducers (14-36, 114-136) comprising means for transmitting ultrasonic energy for propagation therebetween, and said pairs of transducers used for measuring said flow characteristic in dependance on the propagation time, wherein the transducers (14-36, 114-136) of each of said pairs are located in relative upstream- downstream positions along the tube (12, 112), defining a chordal measurement path (38-48, 138-148) therebetween through said fluid (92,192) .

2. The apparatus (10) according to claim 1, wherein said tube (12) is generally cylindrical and comprises bulges on the circumference thereof that provide the surfaces (62-84) that define said hexagonal corners (50-60) .

3. The apparatus (100) according to claim 1, wherein said tube (112) has a hexagonal cross-sectional profile .

4. The apparatus (10, 100) according to any of the preceding claims, wherein the flow characteristic is measured along six chordal paths (38-48, 138-148) defined between six pairs of transducers (14-36, 114- 136) clamped on to the surfaces (62-84, 162-172) defining said hexagonal corners (50-60, 150-160) of the tube (12, 112) .