KR20010034606A - Gas meter dust filter - Google Patents

Abstract

The present invention relates to a gas meter having an inner portion through which gas flows and comprising an ultrasonic measuring tube in a longitudinal axis and at least two ultrasonic transducers spaced along the longitudinal axis thereof. The invention comprises an enlarged portion with respect to the dimensions of the active surface of the transducer between each ultrasonic transducer and the inner portion of the measuring tube, the meter further comprising at least one enlargement to filter for dust particles carried by the gas. And at least one element disposed in the enlarged portion and extending over the entire inner width of the enlarged portion, the element being discharged by the transducer in at least one portion having a width greater than the dimension of the active surface of the transducer. Ultrasound is passed through.

Description

Gas Meter with Dust Collector Filter {GAS METER DUST FILTER}

Gases for which the flow rate is to be measured are known to contain a significant amount of various dust particles.

Over time, dust will accumulate in the various parts of the gas meter, and these parts are not intended to receive dust particles.

Thus, when dust particles accumulate in the ultrasonic transducer, the dust is often known to cause the ultrasonic transducer to fail and adversely affect the linearity of the ultrasonic measurements performed.

Dust traps are provided in the ultrasonic measuring tube upstream of the meter to reduce the volume of dust carried by the gas flow.

However, these dust traps are not always effective because they allow the lighter dust particles to pass through and accumulate on either side or one side of the converter.

Therefore, it was necessary to find an effective solution to the problem caused by dust.

The present invention relates to a gas meter having an ultrasonic measuring tube having a longitudinal axis, comprising at least two ultrasonic transducers spaced along a longitudinal direction and an inner portion through which gas flows.

1 is a schematic longitudinal sectional view of an ultrasonic gas meter according to the present invention;

2 is an enlarged longitudinal sectional view of the measuring tube and ultrasonic transducer shown in FIG. 1 according to the first embodiment;

3 is an enlarged longitudinal sectional view of the measuring tube and ultrasonic transducer shown in FIG. 1 according to a second embodiment;

4 is an enlarged longitudinal sectional view of the measuring tube and ultrasonic transducer shown in FIG. 1 according to a third embodiment;

5 is an enlarged partial view of the enlarged portion 50 shown in FIG.

FIG. 6 shows a variant of the enlarged portion 50 of FIG. 4.

7 is a schematic longitudinal sectional view of a modification of the measuring tube shown in FIGS. 1 to 4.

FIG. 8 is an enlarged view of an enlarged portion in which elements forming a screen are disposed according to a variant of that shown in FIG. 7; FIG.

9 is a longitudinal sectional view of a second modified embodiment of the measuring tube shown in FIGS. 1 to 7;

10 is a longitudinal sectional view of a third modified embodiment of the measuring tube shown in FIGS.

11 is a cross-sectional view of the measuring tube shown in FIG. 10.

12 is a longitudinal sectional view of a fourth modified embodiment of the measuring tube shown in FIGS.

The present invention relates to a gas meter including an ultrasonic measuring tube having an inner portion through which gas flows and an ultrasonic measuring tube in a longitudinal axis, and at least two ultrasonic transducers spaced along the longitudinal axis, wherein each ultrasonic transducer and an inner portion of the measuring tube are provided. And an enlarged portion with respect to the dimensions of the active surface of the transducer, wherein the meter is also disposed in at least one enlarged portion to filter for dust particles carried by the gas and over the entire inner width of the enlarged portion. And at least one element extending over, wherein the element is adapted to pass ultrasonic waves emitted by the transducer in at least one portion having a width greater than the dimensions of the active surface of the transducer.

The filtering element by placing an element in front of one or both sides of the transducer having a surface in contact with the gas flow provided to the ultrasonic wave, the width of which is greater than the dimensions of the active surface of the transducer to form a screen for filtering dust particles. Even if the same dimensions as the active surface of the transducer, dusts are dispersed over a larger surface area. Thus, even after a certain time, the filtering element becomes less clogged.

According to one embodiment of the invention, the element forming the filtering screen is arranged relative to the transducer.

The element forming the filtering screen can be arranged at least in front of the upstream side of the transducer or in front of the transducer, depending on the structure of the gas meter, more particularly the transducer and the enlarged parts, and the measuring tube.

The gas meter preferably includes at least one obstruction disposed in the longitudinal direction on the inner side of the measuring tube to form at least one annular passage for gas flow.

The measuring tube comprises a gas inlet and an outlet, each of which is mounted between one of the enlarged parts and the measuring tube.

Each of the gas inlet and the outlet has a gas passageway at a position where gas enters and exits the measuring tube, and the vertical line of the passage cross section is inclined 90 degrees about the longitudinal axis.

Such orientation of the gas inlet and outlet can lead to a better gas flow direction than in the prior art whereby the dust particles are carried by this flow.

In this way, the dust particles are less directed towards the transducer than in the prior art.

If the gas meter with the inlet and outlet oriented as above comprises an obstacle as described above, the gas flow becomes more straight and the dust particles moving with the flow remain at a certain distance from the converter, thereby contaminating the converter. Risk is reduced.

The elements forming the filtering screen are made of a material made of synthetic resin or metal fibers.

The material may be in the form in which the fibers form a sieve or in which the fibers are entangled and dispersed in their total volume.

The measuring tube may, for example, have an ellipsoid, tubular shape or a longitudinal cross section.

Other features and advantages of the present invention will become more apparent from the description of the embodiments given by way of example only with reference to the accompanying drawings.

As shown in FIG. 1, the ultrasonic gas meter, schematically indicated at 10, includes a housing 12 connected to an inlet 14 and an outlet 16 for gas flow.

The ultrasonic measuring block 18 comprises a measuring tube 20 embodied in the form of a tube having a longitudinal axis ′ ′ embedded in the housing 12, with two ultrasonic transducers 22, 24 at both ends of the measuring tube. It is arranged along the longitudinal axis.

The gas flow (indicated by the arrow in the figures) enters the housing 12 through the hole 14 and impinges on the wall of the ultrasonic measuring block 18 disposed opposite the hole to allow the gas flow to flow between the ultrasonic measuring block and the housing. It is distributed in the inner space.

The gas flow is directed to the bottom of the housing and enters through a hole 26 formed in the measuring block in the housing.

The downward movement of the gas and its flow back up towards the hole 26 causes a significant portion of the heavy particles carried in the gas flow to be removed from the gas flow.

Ultrasonic measurement of gas flow is carried out while the gas flow introduced into the ultrasonic measuring tube 20 exits through the inlet 27 embodied in the form of an annular hole and also through the outlet 28 embodied in the form of an annular hole. Is performed.

The inlet 27 and the outlet 28 have an inclination with respect to the longitudinal axis in the example in which the vertical line of the passage section is shown in Figs.

The gas flow rises again through the chimney 29 and exits the measuring block 18, which is arranged at right angles to the measuring block and in communication with the outlet 16 of the gas meter.

As shown in FIG. 1 and in more detail in FIGS. 2 to 4, the gas meter corresponds to an ultrasonic transducer corresponding between the respective ultrasonic transducers 22 and 24 and the inside of the measuring tube 20 through which the gas flows. And portions 30 and 32 forming a housing and a support for the dragon.

Thus, each inlet 27 and outlet 28 in the form of an annular hole is disposed between the enlarged portions and the measuring tube 20.

Each of the portions 30, 32 has an enlarged transverse dimension compared to the transverse dimension of the active surface of the transducers.

For example, each of the aforementioned portions has a generally outer cylindrical shape that has a cylindrical shape and includes inner recesses 34, 36 equipped with a corresponding ultrasonic transducer.

Each of the above sections comprises outer circumferential flanges 38, 40, which extend in a cylindrical shape and provide cylindrical free spaces 42, 44 in front of each transducer, the free space of the transducers. It has a transverse dimension which is enlarged to a transverse dimension of the active surface.

Considering the structure of the measuring tube and the flow inside the measuring tube which carries the dust directly to the active surface of the transducer 24, at least one free space 44 is arranged in front of the downstream transducer 24. It is preferable to place the element 46 (see FIG. 2).

The element 46 is arranged in contact with the transducer and extends transversely across the width of the free space or the entire inner transverse dimension to act as a filter to prevent dust carried by the gas in front of the transducer from reaching the transducer. To form.

The filtering element is arranged at the bottom of the free space and is fixed by, for example, bonding to the annular portion 32a of the portion 32 surrounding the transducer 24.

The filtering element is made of a material formed from fibers of metal or synthetic resin.

Each fiber constitutes an obstacle that prevents dust particles from passing across the fibers.

It is necessary to provide a sufficient number of fibers to ensure accurate filtering.

The filter may be in the form of a body in which dust particles are dispersed on an almost flat surface.

The material may be, for example, a cloth of stainless steel with a metal fiber diameter of 25 microns and a space of 16 microns.

However, in order to make the present invention more efficient, it is desirable to provide a material which can be made into a filter in which dust particles are dispersed in the internal space.

Thus, filters made of weaving fibers can accumulate more dust before clogging than filters in the form of sieves.

Such materials may be cotton or flannel.

More particularly, the material may be a product sold by 3M Corporation as "FILTRETE 50g".

The fiber density in the material may be from 10 to 500 g / m 2, with a specific gravity of 50 g / m 2 and a thickness of 2 mm.

The size of the fibers is an important parameter, it is desirable to have fine fibers for a given spacing between the fibers, because the porosity of the filter must be larger.

The sectors in which the ultrasonic waves emitted by the transducer 24 are accommodated are indicated by dashed lines in FIG. 2.

The transverse dimension of the surface of the filtering element 46 is larger than that of the active surface of the transducer, with the filtering element first buried in a material transparent to the ultrasonic wave and the ultrasonic waves emitted by the transducer 24 are transverse to the active surface of the transducer. It is disposed in an area passing over a portion of the transverse dimension that is larger than the directional dimension.

As a result, even if a given volume of dust particles accumulate in the filtering element and partially block the holes, sufficient free passages provided by the filtering element for the ultrasonic wave remain so that the passage of the ultrasonic wave is not excessively reduced.

However, when the filtering element is disposed with respect to the transducer of FIG. 2 and the material of the filtering element is in the form of dust dispersed in the internal space, the density of the material of the filtering element is increased so that the amount of dust is excessively large so that ultrasonic waves are not excessively attenuated. While reducing its longitudinal dimension or thickness.

Indeed, for a given amount of dust, the ultrasonic waves propagate and the volume of the material in which the dust accumulates is increased, and the fibers are also spaced at larger intervals than before, resulting in a "dilution" effect of the dust and the material being less than at a reduced material thickness. It allows more freedom to propagate within.

The effect of filtering remains almost the same.

It should be noted that as the thickness of the material increases while the material remains the same density, the filtering effect is increased but the ultrasound is further reduced.

The structure of the measuring tube and / or the enlarged portion and / or the filtering element is such that, in the absence of dust, ultrasonic waves pass through the filtering element for a portion of the transverse dimension of the filtering element, such as the transverse dimension of the active surface of the transducer, It is configured to have a significant influence on the transmission of the ultrasonic wave and the flow rate measurement when the ultrasonic wave is substantially blocked at the portion of the filtering element through which the ultrasonic wave passes with the same volume of dust as described above.

The filtering element 46 located in front of the transducer 24 makes it possible to eliminate turbulent conditions present in the gas flow, which, when occurring in front of the transducer, adversely affects the linearity of the measurement.

In another embodiment of the present invention, as shown in FIG. 3, a filtering element 48, similar to the filtering element 46, is located in the free space 42 of the enlarged portions 30, 32 so as to provide a transducer for dust. 22) Protect.

This prevention can be useful when the meter is subjected to severe dust clogging tests or when the meter is used to meter a particularly dusty gas.

According to the third preferred embodiment shown in FIG. 4, each of the generally enlarged cylindrical portions 50, 52 comprises a cylindrically extending outer circumferential surface flange 54, 56 and cylindrically in front of each transducer. Free space portions 58, 60 are provided.

The longitudinal dimensions of the flanges 54, 56 and free spaces 58, 60 are larger than those of the flanges 38, 40 and free spaces 42, 44 of FIG. 2.

Thus, the extension of the internal free spaces to the enlarged portions 50, 52 may enable the respective filtering elements 62, 64 to be arranged at a distance from the corresponding transducers 22, 24, thereby filtering. There is an area of free space in which gas resides between the element and the corresponding transducer.

The free space 58 and / or 60 may have a plurality of sieve-shaped filtering elements eccentric along a longitudinal axis, the fibers and spacing of the filtering elements being transversely between two successive filtering elements. It can be eccentric and collect more dust than using this type of filter.

In this structure, two types of filtering elements are combined by placing a "volume" filter (in the form of dust particles dispersed in the inner space) away from the transducer to improve filtering reliability and by placing a sieve-shaped filter between them. Is very desirable. In fact, the dust particles are clearly stopped by the filter in the form of a sieve even if they are not stopped by the "volume" filter.

It is also conceivable to mount a single thick filtering element in the free space in front of the transducer.

FIG. 5 shows a partial enlargement of the part 50 shown in FIG. 4, showing a part of the part, the remaining part being obtained symmetrically about the longitudinal axis ′ ′.

In this figure, the filtering element 62 is sandwiched between a flange 54 with a washer 57 and a jaw 55 formed integral with the end of the flange, for example by ultrasonic welding.

FIG. 6 shows a variant of the enlarged portion 50 of FIG. 4, in which the flange 66 extends into the cylindrical portion of the enlarged portion 68 so as to become freely spaced in the enlarged portion of the enlarged shape opposite the transducer. Provide 70.

The filtering elements 62 are arranged at a distance from the transducer in this open space.

FIG. 7 is a variant of the measuring tube shown in FIGS. 1 to 4, which takes the form of an elliptical rotor 72 as disclosed in French Patent No. 2 683 046.

The ellipsoid of FIG. 7 is structurally different from that of French Patent No. 2 683 046. That is, the flow of fluid is realized through holes formed in the wall of the conduit 72 and not around the transducers.

Each of the two enlarged portions 74, 76 used as a housing for the ultrasonic transducers 78, 80 has progressively spaced internal free spaces 82, 84, in which filtering elements 86, 88 are located. Are arranged, and the filtering element is similar to that described with reference to FIGS. 4 to 6.

Two annular holes 90, 92 used as inlets and outlets for gas flow in the inside of the measuring tube 72 are mounted between the measuring tube and the enlarged portions 74, 76.

Each of these holes has a gas passage portion at a position where gas flow is introduced into and discharged from the measuring tube 72, and the vertical line N of the passage portion is inclined at an angle α varied from 90 ° with respect to the longitudinal axis X '.

For example the angle of inclination is 45 °.

Moreover, a long cone 94 of conical shape with rounded protrusions is arranged on the longitudinal axis VII '.

The obstacle together with the inner wall of the measuring tube defines an annular passage 96.

Thanks to the orientation in the vertical line N with respect to the gas passage portion and the annular shape of the passage 96 at the position where the gas flow enters and exits the measuring tube 72, the gas flow passes through the channel and is accompanied by dust. Are moved on the trajectory away from the transducers 78 and 80.

With this structure, the filtering element 86 located in front of the upstream transducer 78 accumulates less dust, while the filtering element 88 located in front of the downstream transducer 80 has a filtering element as shown in FIG. It can be seen that the dust layer 98 is formed in the vicinity of.

FIG. 8 shows another variant of an enlarged portion 100 that can be used with the measuring tube 72 of FIG. 7, where the free space portion 102 is in the form of a cylindrical space portion, at the bottom of the space portion. Filtering element 86 is disposed with respect to transducer 78.

9 shows another configuration of the ultrasonic meter 110, wherein the measuring block 112 (embedded in the outer housing) is disclosed and shown in European Patent Application No. 0 682 773.

This measuring block comprises a tubular measuring tube 114 provided with an inlet 116 and an outlet 118, the vertical line of the inlet and outlet gas passages from the measuring tube forming 90 ° with respect to the longitudinal axis ′ ′. do.

An improvement on this structure is to form the holes 116 and 118 at an angle of less than 90 ° with respect to the longitudinal axis VII 'so that the gas flow and dust particles are separated in the area where the transducer is mounted.

The long obstacle 120 is disposed along the longitudinal axis inside the measuring tube 114 to form an annular passage 122 through which gas flows.

Two enlarged portions 124 and 126 are formed at an angle of 90 [deg.] With respect to the longitudinal axis VII 'so that the ultrasonic transducers 128 and 130 embedded in these portions can be offset.

Ultrasound emitted by these transducers is reflected by the walls 132, 134 of the annular passageway 122.

The two filtering elements 136, 138 described above with reference to the figures are mounted at both ends of the obstacle 120.

The transducer may place the filtering elements in a portion of the enlarged portions 124, 126 in a position 90 ° inverted from the position shown in FIG. 9.

The gas meter 140 shown in the longitudinal direction in FIG. 10 includes a measuring tube 142 having a longitudinal axis ′ ′, and the cross section shown in FIG. 11 is rectangular.

Two portions 144 and 146 enlarged relative to the dimensions of the ultrasonic transducers 148 and 150 are mounted to one of the walls 142 of the walls of the measuring tube inclined with respect to the longitudinal axis VII '.

The transducers 148 and 150 are mounted on the bottom of the enlarged portions 144 and 146 that receive them, and the filtering elements 152 and 154 in accordance with those described with reference to FIG. 4 are free cylindrical portions 156 and 158 spaced apart from the transducers. )

Ultrasound emitted by one of the transducers propagates along the trajectory of V or W.

The function of the meter when the trajectory of the ultrasonic waves has the shape of W is described in EP 0 521 855.

Two transducers can be arranged on the opposite wall 142b of the measuring tube, or one of the transducers can be mounted on the wall 142a and the other transducer can be mounted on the opposite wall 142b so that the two transducers They are arranged in a straight line by an imaginary straight line YY 'perpendicular to each other and are inclined to less than 90 degrees when cut in the longitudinal axis direction (Fig. 12).

It is also possible to use a rectangular measuring tube structure in which the enlarged parts receive ultrasonic transducers arranged at opposite ends of the measuring tube.

Claims (15)

Ultrasonic measuring tubes (20; 72; 114; 142) having an inner portion through which gas flows and having a longitudinal axis (XX '), and at least two ultrasonic transducers (22, 24; 78, 80; 128, 130) spaced along the longitudinal axis; 148,150, comprising a portion 30, 32; 50, 52; 68; 74, 76 enlarged with respect to the dimensions of the active surface of the transducer between each ultrasonic transducer and the inside of the measuring tube; The meter also includes at least one element (46, 48; 62, 64; 86) disposed in at least one enlarged portion to filter out dust particles carried by the gas and extending over the entire inner width of the enlarged portion. 88; 136,138; 152,154. Gas meter according to claim 1, characterized in that said at least one element (46,48) forming a filtering screen is arranged with respect to the transducer. The gas meter of claim 1, wherein at least one element (62,64; 86,88; 136,138; 152,154) forming the filtering screen is arranged at a distance from the transducer. 4. Gas meter according to any one of the preceding claims, characterized in that at least one element (48; 62; 86; 136; 152) forming the filtering screen is arranged in front of the upstream transducer. 4. Gas meter according to any one of the preceding claims, characterized in that at least one element (46; 64; 88; 138; 154) forming the filtering screen is arranged in front of the downstream converter. 6. The at least one obstruction of any one of claims 1 to 5, disposed longitudinally within the measuring tube to transport dust from the ultrasonic transducers at a distance and to form at least one annular passageway for gas flow. Gas meter comprising (94; 120). The measuring tube according to any one of claims 1 to 6, wherein the measuring tube includes an inlet (27; 90; 116) and an outlet (28; 92; 118) for gas flow, and the inlet and outlet are enlarged with the measuring tube. A gas meter each formed between one of the sections. 8. The gas inlet and outlet of claim 7, wherein the gas inlet and outlet have a passage for gas flow at a position where the gas flows into and out of the measuring tube, the vertical line of the passage being inclined at an angle that is changed at 90 ° with respect to the longitudinal axis direction. Gas meter, characterized in that. 8. The gas meter according to claim 7, wherein the gas inlet and the outlet have a passage section for gas flow at a position where the gas flow enters and exits the measuring tube, and the vertical line of the passage section is 90 degrees with respect to the longitudinal axis direction. . 10. The gas meter of claim 1, wherein at least one element forming the filtering screen is made of a material made of metal or plastic fibers. 11. The gas meter of claim 10, wherein the material is in the form of fibers forming a sieve. 11. The gas meter of claim 10, wherein the material is in the form of spaced and dispersed fibers in the volume. 13. Gas meter according to any one of the preceding claims, characterized in that the measuring tube is in the form of an elliptical rotor (72). 13. Gas meter according to any one of the preceding claims, characterized in that the measuring tube is a tube (20; 114). The gas meter according to any one of claims 1 to 12, wherein the measuring tube (142) has a rectangular cross section.