CN113340380A - Method for detecting liquid level position based on surface wave mode conversion - Google Patents
Method for detecting liquid level position based on surface wave mode conversion Download PDFInfo
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- CN113340380A CN113340380A CN202110740213.8A CN202110740213A CN113340380A CN 113340380 A CN113340380 A CN 113340380A CN 202110740213 A CN202110740213 A CN 202110740213A CN 113340380 A CN113340380 A CN 113340380A
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- 239000007788 liquid Substances 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 13
- 238000007654 immersion Methods 0.000 claims abstract description 13
- 238000006073 displacement reaction Methods 0.000 claims abstract description 12
- 238000010897 surface acoustic wave method Methods 0.000 claims abstract description 10
- 230000005284 excitation Effects 0.000 claims description 6
- 230000001902 propagating effect Effects 0.000 claims description 5
- 230000000644 propagated effect Effects 0.000 claims description 3
- 238000001514 detection method Methods 0.000 abstract description 2
- 238000005259 measurement Methods 0.000 description 10
- 238000002604 ultrasonography Methods 0.000 description 7
- 230000007423 decrease Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000006124 Pilkington process Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002828 fuel tank Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/296—Acoustic waves
- G01F23/2962—Measuring transit time of reflected waves
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- Acoustics & Sound (AREA)
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- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
The invention discloses a method for measuring liquid level position based on surface wave mode conversion, which comprises the following steps: a cuboid waveguide rod is vertically inserted into the bottom of the liquid, and a model of surface waves is excited on the surface of the waveguide rod by ultrasonic vibration; receiving the arriving sound waves on the air wave guide rod and the immersion liquid wave guide rod; and (3) on the surface of the waveguide rod, taking the displacement of points along the acoustic wave propagation path to respectively obtain the surface acoustic wave velocity in the air waveguide rod and the Stoneley wave propagation velocity in the immersion waveguide rod. And determining the position of the liquid level by combining the time of the Stoneley wave reaching the bottom of the waveguide rod and the surface wave velocity, the Stoneley wave velocity and the position excited by the sound wave. The invention provides a reliable method for measuring the liquid level position and provides a guide basis for realizing the on-line detection of the liquid level position.
Description
Technical Field
The invention relates to the technical field of ultrasonic detection, in particular to a method for detecting a liquid level position based on surface wave mode conversion.
Background
The most traditional method of level measurement is the float method. This method is mainly measured by the principle that the float will decrease as the liquid level becomes lower. A particular measurement method is that the float changes with the liquid level as it increases or decreases. As the float changes, the resistive element carried by the float also changes. When the liquid is very little, the liquid level will become very low, so the floater will also decrease with the liquid level, and the resistance on the floater is also driven, at this time, the resistance value of the resistance will become very large. In case the circuit becomes large, the current will become small and the pointer will point to the small side of the liquid level. Another conventional method of measuring the liquid level is to measure with a hall element. The specific principle is that when the fuel quantity in the fuel tank is increased or decreased, the float changes along with the change of the liquid level, and the linear Hall element on the float is driven to change. When the liquid level becomes low, the float will lower as the liquid level becomes lower. The magnet on the float link will not be at a level at this time, and the magnetic flux between the hall element and the magnet, which is linearly output, will become large at this time, causing a change in the voltage dividing resistance, thereby pointing to the side where the liquid level is less.
The ultrasonic type is a method of detecting a liquid level using ultrasound, air-coupled ultrasound, a submerged ultrasonic sensor, and a time elapsed for guiding the ultrasound. Because of its simplicity of use, safety and reliability, it finds wide application in many applications. In the case of using air coupling and immersion ultrasound, maintenance is required on a regular basis. In contrast, ultrasound guided methods require minimal maintenance and can be robust in operation because the source of the ultrasound waves need not be exposed to the liquid tank for a long period of time. There are several types of guided ultrasound, such as surface waves, torsional waves, transverse waves, and the like. We are particularly concerned with surface waves, which are predominantly present in the surface of the structure, propagating along the surface of the waveguide rod. Further, the velocity of the surface wave is slow relative to the velocities of other guided waves, and therefore it is considered that the measurement accuracy can be improved, which is closely related to the time resolution of the measurement apparatus. Further, when the surface wave propagating waveguide is immersed in a liquid, the velocity of the surface wave decreases.
However, no studies have been made to measure the position of the liquid surface by using the mode conversion of the surface wave. In the industry, the liquid level position measurement often generates errors due to human factors, instrument factors, environmental factors and the like, which brings disadvantages to production and application and influences economic benefits to a certain extent.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the method for detecting the liquid level position based on the surface wave mode conversion, which can better position the liquid level position by using fewer measurement parameters, has higher measurement precision and can be used for industrial online monitoring.
The purpose of the invention is realized by the following technical scheme.
A method for detecting a liquid level position based on surface wave mode conversion comprises the following steps:
1) establishing a waveguide rod model: a cuboid waveguide rod is vertically inserted into the bottom of the liquid, and a model of surface waves is excited on the surface of the waveguide rod by ultrasonic vibration;
2) receiving the arriving surface acoustic wave on an air waveguide rod;
3) calculating the propagation speed of the surface wave according to the arrival time of the surface wave obtained in the step 2);
4) displacement is taken point by point in the acoustic wave propagation path of the immersion waveguide rod, and the speed of the Stoneley wave propagated by the acoustic wave on the solid-liquid surface is obtained according to the relationship between the arrival time and the position of the acoustic wave;
5) receiving an arriving stoneley wave at the bottom of the immersion waveguide rod;
6) and determining the position of the liquid level according to the Stoneley wave arrival time obtained in the step 5) and by combining the surface wave velocity, the Stoneley wave velocity and the position excited by the acoustic wave obtained in the step 3) and the step 4).
Further, in the model of the surface wave, the speed of sound wave propagation is obtained by different point displacement waveforms.
Further, the specific method for the propagation speed of the surface wave in the air wave guide rod in the step 3) is as follows:
when the surface wave is transmitted on the surface of the waveguide rod, partial displacement of an object can be caused, and the speed of surface wave transmission in the air waveguide rod is obtained by measuring the arrival time of the surface wave. Suppose that two points x are taken along the propagation direction of a surface wave1And x2At a distance Δ x1＝x2-x1. Surface wave arrival x1And x2Respectively at times t1，t2With a time difference of Δ t1＝t2-t1Thereby obtaining the propagation velocity V of the surface wave under the air loadair＝Δx1/Δt1。
Further, the specific method for the propagation speed of the stoneley wave on the solid-liquid surface in the step 4) is as follows:
the wave propagating on the solid-liquid surface is a stoneley wave. The propagation speed of the Stoneley wave on the solid-liquid surface can be obtained by measuring the displacement condition of the solid-liquid surface acoustic wave. Taking two points x along the Stoneley wave propagation direction3And x4Having a propagation distance Δ x2＝x4-x3(ii) a Stoneley wave arrival x3And x4Respectively at times t3，t4With a time difference of Δ t2＝t4-t3Thereby obtaining the propagation velocity V of the Stoneley wave on the solid-liquid surfaceliquid＝Δx2/Δt2。
Further, in the step 6), the liquid level position is determined according to the stoneley wave arrival time, the surface wave velocity, the stoneley wave velocity and the acoustic wave excitation position, and the specific method is as follows:
the arrival time of the Stoneley wave received by the bottom of the immersion liquid waveguide rod is T, and L is the distance between the excitation point and the bottom of the waveguide rod. Assuming the depth of H liquid, by the formula (L-H)/Vair+H/VliquidDetermining the liquid level position H, where VairIs the velocity of the surface wave in the air waveguide rod, VliquidIs the velocity of the surface wave in the liquid waveguide.
Compared with the prior art, the invention has the advantages that: the liquid level position can be judged by the propagation speed of the surface wave on the solid-liquid surface and the time when the sound wave reaches the bottom of the immersion waveguide rod through the propagation speed of the surface wave measured in advance on the air waveguide rod. The invention can better position the liquid level position by using less measurement parameters, has higher measurement precision and can be used for industrial online monitoring.
Drawings
FIG. 1 is a schematic flow chart diagram illustrating one embodiment of a method for detecting fluid level using surface wave mode conversion in accordance with the present invention;
FIG. 2 is a schematic view of a liquid level measurement model;
fig. 3 is an acoustic wave propagation waveform.
Detailed Description
The invention is described in detail below with reference to the drawings and specific examples.
As shown in fig. 1, which is a schematic flowchart of an embodiment of detecting a liquid level position by using surface wave mode conversion according to the present invention, a method for detecting a liquid level position based on surface wave mode conversion includes the following steps:
1) establishing a waveguide rod model: a cuboid waveguide rod is vertically inserted into the bottom of the liquid, and a model of surface waves is excited on the surface of the waveguide rod by ultrasonic vibration; part of the waveguide rod is immersed in the liquid, and the acoustic wave excitation position is placed in the air.
2) Receiving the arriving surface acoustic wave on an air waveguide rod;
3) calculating the propagation speed of the surface wave according to the arrival time of the surface wave obtained in the step 2); receiving a surface wave waveform at the air waveguide rod part along the surface wave propagation direction, and calculating the surface wave propagation speed; when the surface wave is transmitted on the surface of the waveguide rod, partial displacement of an object can be caused, and the speed of surface wave transmission in the air waveguide rod is obtained by measuring the arrival time of the surface wave. Suppose that two points x are taken along the propagation direction of a surface wave1And x2At a distance Δ x1＝x2-x1. Surface wave arrival x1And x2Respectively at times t1，t2With a time difference of Δ t1＝t2-t1Thereby obtaining the propagation velocity V of the surface wave under the air loadair＝Δx1/Δt1。
4) Taking point by point in acoustic wave propagation path of immersion waveguide rodDisplacement, namely obtaining the speed of the Stoneley wave transmitted by the sound wave on the solid-liquid surface according to the relation between the arrival time and the position of the sound wave; the wave propagating on the solid-liquid surface is a stoneley wave. The propagation speed of the Stoneley wave on the solid-liquid surface can be obtained by measuring the displacement condition of the solid-liquid surface acoustic wave. Taking two points x along the Stoneley wave propagation direction3And x4Having a propagation distance Δ x2＝x4-x3(ii) a Stoneley wave arrival x3And x4Respectively at times t3，t4With a time difference of Δ t2＝t4-t3Thereby obtaining the propagation velocity V of the Stoneley wave on the solid-liquid surfaceliquid＝Δx2/Δt2。
5) Receiving an arriving stoneley wave at the bottom of the immersion waveguide rod;
6) and determining the position of the liquid level according to the Stoneley wave arrival time obtained in the step 5) and by combining the surface wave velocity, the Stoneley wave velocity and the position excited by the acoustic wave obtained in the step 3) and the step 4).
The arrival time of the Stoneley wave received by the bottom of the immersion liquid waveguide rod is T, and L is the distance between the excitation point and the bottom of the waveguide rod. Assuming the depth of H liquid, by the formula (L-H)/Vair+-H/VliquidDetermining the liquid level position H, where VairIs the velocity of the surface wave in the air waveguide rod, VliquidIs the velocity of the surface wave in the liquid waveguide.
Fig. 2 is a schematic view of a liquid level measurement model. The waveguide rod is directly inserted into the bottom of the container, surface waves are excited through vibration, and sound waves are received through a receiver at the bottom;
fig. 3 is an acoustic wave propagation waveform. The vertical coordinate of a oscillogram received at the bottom of the immersion waveguide rod is acoustic displacement, and the horizontal coordinate is time;
the foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (5)
1. A method for detecting a liquid level position based on surface wave mode conversion is characterized by comprising the following steps:
1) establishing a waveguide rod model: a cuboid waveguide rod is vertically inserted into the bottom of the liquid, and a model of surface waves is excited on the surface of the waveguide rod by ultrasonic vibration;
2) receiving the arriving surface acoustic wave on an air waveguide rod;
3) calculating the propagation speed of the surface wave according to the arrival time of the surface wave obtained in the step 2);
4) displacement is taken point by point in the acoustic wave propagation path of the immersion waveguide rod, and the speed of the Stoneley wave propagated by the acoustic wave on the solid-liquid surface is obtained according to the relationship between the arrival time and the position of the acoustic wave;
5) receiving an arriving stoneley wave at the bottom of the immersion waveguide rod;
6) and determining the position of the liquid level according to the Stoneley wave arrival time obtained in the step 5) and by combining the surface wave velocity, the Stoneley wave velocity and the position excited by the acoustic wave obtained in the step 3) and the step 4).
2. The method of claim 1, wherein the model of the surface wave is characterized by a velocity of acoustic wave propagation derived from different point displacement waveforms.
3. The method for detecting the position of the liquid level based on the surface wave mode conversion as claimed in claim 1, wherein the specific method for the propagation speed of the surface wave in the air waveguide rod in the step 3) is as follows:
the surface wave can cause partial displacement of an object when propagating on the surface of the waveguide rod, the speed of surface acoustic wave propagation in the air waveguide rod is obtained by measuring the arrival time of the surface acoustic wave, and two points x are assumed to be taken along the propagation direction of the surface acoustic wave1And x2At a distance Δ x1＝x2-x1Surface wave arrival x1And x2Respectively at times t1，t2With a time difference of Δ t1＝t2-t1Thereby obtaining the propagation velocity V of the surface wave under the air loadair＝Δx1/Δt1。
4. The method for detecting the liquid level position based on the surface wave mode conversion as claimed in claim 1, wherein the specific method of the propagation speed of the stoneley wave on the solid-liquid surface in the step 4) is as follows:
the wave propagated on the solid-liquid surface is a Stoneley wave, the propagation speed of the Stoneley wave on the solid-liquid surface can be obtained by measuring the displacement condition of the solid-liquid surface acoustic wave, and two points x are taken along the propagation direction of the Stoneley wave3And x4Having a propagation distance Δ x2＝x4-x3(ii) a Stoneley wave arrival x3And x4Respectively at times t3，t4With a time difference of Δ t2＝t4-t3Thereby obtaining the propagation velocity V of the Stoneley wave on the solid-liquid surfaceliquid＝Δx2/Δt2。
5. The method of claim 1, wherein step 6) determines the liquid level position based on the stoneley wave arrival time, the surface wave velocity, the stoneley wave velocity, and the acoustic wave excitation position by:
the arrival time of the Stoneley wave received and arrived at the bottom of the dip waveguide rod is T, L is the distance between an excitation point and the bottom of the dip waveguide rod, and the depth of the H liquid is assumed to pass through the formula (L-H)/Vair+H/VliquidDetermining the liquid level position H, where VairIs the velocity of the surface wave in the air waveguide rod, VliquidIs the velocity of the surface wave in the liquid waveguide.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114910203A (en) * | 2022-06-21 | 2022-08-16 | 武汉大学 | Material surface stress detection method based on laser synchronous induction ultrasonic surface wave and air wave |
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Patent Citations (6)
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| CN103697966A (en) * | 2013-11-27 | 2014-04-02 | 浙江大学 | Device and method for measuring height of micro-amplitude liquid surface wave in real time |
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