CN110631957A - Device and method for detecting liquid level fluctuation characteristics based on acoustic signals - Google Patents
Device and method for detecting liquid level fluctuation characteristics based on acoustic signals Download PDFInfo
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- CN110631957A CN110631957A CN201910815457.0A CN201910815457A CN110631957A CN 110631957 A CN110631957 A CN 110631957A CN 201910815457 A CN201910815457 A CN 201910815457A CN 110631957 A CN110631957 A CN 110631957A
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- 239000007788 liquid Substances 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000010363 phase shift Effects 0.000 claims abstract description 42
- 238000004891 communication Methods 0.000 claims abstract description 4
- 238000012545 processing Methods 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 claims description 5
- 230000036962 time dependent Effects 0.000 claims description 4
- 230000005284 excitation Effects 0.000 claims description 2
- 239000012530 fluid Substances 0.000 abstract description 9
- 238000001514 detection method Methods 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 abstract 1
- 230000003746 surface roughness Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 239000000523 sample Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/24—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting acoustical wave
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N2011/006—Determining flow properties indirectly by measuring other parameters of the system
- G01N2011/0073—Determining flow properties indirectly by measuring other parameters of the system acoustic properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/022—Liquids
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Abstract
The invention discloses a device and a method for detecting liquid level fluctuation characteristics based on acoustic signals, and belongs to the acoustic technology. The detection device comprises a signal emitting module, a signal detecting module and a processor, wherein the signal emitting module comprises a signal generator and a sound source transducer, one or more acoustic signals can be emitted, and the receiver comprises a microphone which can be used as an acoustic receiver, and one or more acoustic signals can be detected after reflection from a small target area of the liquid surface. The processor can be in data communication with the transmitter or receiver via a cable or wirelessly, the processor indicating fluctuations over time in the local height of the liquid surface in the target area as a function of phase shift changes between the transmitted and received acoustic signals. The invention overcomes the disadvantage of detecting the fluctuation characteristic of the fluid interface by an invasive method and a system, reduces the data fuzziness caused by environmental change and enlarges the application range.
Description
Technical Field
The invention relates to a device and a method for detecting liquid level fluctuation characteristics based on acoustic signals, and belongs to the field of acoustic detection.
Background
An example of an interface between two fluids is the free surface of a liquid (second fluid) under a gaseous atmosphere (first fluid). The liquid may be relatively static with surface fluctuations caused by wind. The liquid may flow in a conduit or channel and also have surface undulations caused by turbulence. Monitoring the flow conditions of free surface flow is important in many applications, such as river flood monitoring, water and waste treatment and flow control in petrochemical and food processing plants.
The prior art has primarily captured detailed surface fluctuations of the fluid interface through the use of invasive conductivity probes. Although these probes can collect fluctuations in water flow and produce their own surface fluctuations, this collection may obscure the data. The use of an acoustic device to measure the relative position of the water surface, with the acoustic source and acoustic receiver located above the free surface of the liquid, without the need to probe the sensor into the liquid, has great advantages in some liquid-inaccessible condition measurements (e.g., measuring the fill level of a corrosive liquid storage tank).
Disclosure of Invention
In order to solve the problem of detecting the fluctuation characteristics of the liquid level, the invention provides a device and a method for detecting the fluctuation characteristics of the liquid level based on an acoustic signal, which solve the fluctuation of the local height of the liquid surface in a target area along with time, and the fluctuation of the measured height can be used for deducing the flow characteristics (surface roughness, flow depth, flow speed, volume flow speed and the like) of the liquid.
The technical scheme of the invention is as follows: an apparatus for detecting a liquid level fluctuation characteristic based on an acoustic signal, comprising a signal transmission module for generating an acoustic signal and transmitting the acoustic signal from a first known point to a point on a liquid surface; the signal receiving module is used for receiving the acoustic signal which reaches a second known point after being reflected from the surface of the liquid; a processor for processing the detected acoustic signals, monitoring changes in phase shift between the transmitted and received acoustic signals, and using the changes in phase shift to indicate fluctuations in the height of the liquid surface; the signal transmitting module and the signal receiving module are fixed above a target area to be detected and are respectively connected with the processor;
the signal transmitting module comprises a signal generator and a transducer, and the signal receiving module comprises an acoustic signal receiver, a transducer and a wireless communication module.
The method for detecting the liquid level fluctuation characteristic by using the device comprises the following specific steps:
s1, the signal transmitting module transmits the acoustic signal from the sound source to at least one target area on the liquid surface;
s2, after the acoustic signal is reflected from the target area, an acoustic receiver in the signal receiving module receives the acoustic signal;
s3, the processor periodically processes the detected acoustic signals, measures phase shifts of the transmitted and received acoustic signals, determines phase change information based on a first phase shift of the first acoustic signal and a second phase shift of the second acoustic signal and uses the phase shifts to indicate fluctuations in local elevation of the liquid interface in the target region over time.
Wherein the first fluid is a gas and the second fluid is a liquid; the interface is the free surface of the liquid; since the liquid is flowing and the characteristics of the liquid are derived from the measured phase shift changes, the measured height fluctuations can be used to infer the flow characteristics are surface roughness, flow depth, flow rate, volumetric flow rate, etc. by appropriate calibration.
The acoustic signal transmitted by the signal generator comprises a sine wave, the phases of the transmitted acoustic signal and the received acoustic signal are compared over several sine wave periods to obtain a phase shift measurement at a given time, the phase shift being determined by a hilbert transform of the transmitted acoustic signal and the received acoustic signal; the first acoustic signal is an acoustic signal emitted at a first time, the second acoustic signal is an acoustic signal emitted at a second time, the first phase shift represents a time-dependent phase shift of the first acoustic signal between the first time and its reflection, and the second phase shift represents a time-dependent phase shift of the second acoustic signal between the second time and its reflection.
Based on the measured phase shift change, the known distances of the acoustic source and acoustic receivers, and the known heights of the acoustic receivers relative to the interface, a wave height change at the target region is determined.
The invention has the beneficial effects that:
1. the disadvantage of detecting the fluctuation characteristic of the fluid interface by an invasive method and a system is overcome, and the data fuzziness caused by environmental change is reduced.
2. The application range is expanded, and the method can be used for measuring the flow characteristics of some dangerous liquids;
3. the local height of the liquid surface in the target region is detected as a function of time, and the measured height fluctuations can be used to infer liquid flow characteristics, such as surface roughness, flow depth, flow rate, volumetric flow rate, etc.
Drawings
FIG. 1 is a schematic diagram of a detection device for detecting the fluctuation characteristics of a liquid level based on an acoustic signal;
FIG. 2 is a flow chart for detecting the characteristics of a liquid level fluctuation based on an acoustic signal;
FIG. 3 is a graph of the level fluctuation detected by acoustic signals;
FIG. 4 is a schematic diagram of phase shift versus wave height;
FIG. 5 is a graph of the relationship between wave height and flow rate.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
Example 1: in order to accurately acquire the local dynamic fluctuation of the fluid, a detection device as shown in fig. 1 is installed above a target area, and the device for detecting the fluctuation of the surface of the liquid comprises: comprising a signal transmitting module for generating an acoustic signal and transmitting the acoustic signal from a first known point to a point on the surface of the liquid; the signal receiving module is used for receiving the acoustic signal which reaches a second known point after being reflected from the surface of the liquid; a processor for processing the detected acoustic signals, monitoring changes in phase shift between the transmitted and received acoustic signals, and using the changes in phase shift to indicate fluctuations in the height of the liquid surface; the signal transmitting module and the signal receiving module are fixed above a target area to be detected and are respectively connected with the processor; the signal emitting module includes a signal generator and a sound source transducer that can emit one or more acoustic signals, the signal receiving module includes a microphone that can act as an acoustic receiver, a transducer, and a wireless communication module that can detect the one or more acoustic signals after reflection from a small target area of the liquid surface, a processor that can communicate data via cable or wirelessly with the transmitter or receiver, the processor being a mobile personal computer, handheld device or other computing device (containing a display) that controls the transmitter to emit the acoustic signals for an extended period of time, the processor triggering the receiver to receive the acoustic signals reflected back from the surface and process the received signals on a continuous or pseudo-continuous basis. These can be achieved using conventional existing equipment.
In implementations where the apparatus can perform dynamic surge detection of hydraulic flow in shallow water channels, rivers, partially filled pipes and other non-pressurized pipes, the signal emitting module and the signal receiving module can be mounted under bridges on rivers, on top of pipes or above their own platforms, as determined by the actual situation. Detection process as shown in fig. 2, the acoustic transmitter in the signal transmission module transmits an acoustic signal from a first known point to a point on the surface of the liquid. After reflection from the liquid surface, an acoustic receiver in the signal detection module receives the acoustic signal at a second known point, and a processing module periodically processes the detected signal, monitors the change in phase shift between the transmitted and received acoustic signals, and uses the change in phase shift to indicate the fluctuation in liquid surface height at that point, with the change in measured liquid surface fluctuation height of the acoustic signal versus time as shown in FIG. 3. Determining phase change information based on the first phase shift and the second phase shift if the liquid surface is stationary or when two acoustic signals are presentBeing reflected at least at the same location, the value of the first phase shift is the same as the value of the second phase shift, and thus a phase change of value 0 indicates that the spot has not fluctuated or has fluctuated for one period. If the surface of the liquid is displaced vertically, the value of the first phase shift is different from the value of the second phase shift, and therefore the value of the phase change is changed, which can indicate the surface fluctuation in an arbitrary proportion. As shown in fig. 4, the principle of phase shift and fluctuation height is explained by calculating hilbert transform of transmitted and received acoustic data, and transmitting an acoustic signal Ve(t) and reception Vr(t) the hilbert transform of the acoustic signal is defined by:
Aeand ArAmplitude, w, of transmitted and received acoustic data, respectivelysIs the excitation frequency of the transmitter, and phisIs the phase of the acoustic data transmitted at time t-0. The processing module determines the phase shift of each acoustic data by means of a hilbert transform, here by taking the natural logarithm of the ratio of the analysis signals between the transmitted and the received acoustic data, where IM is the imaginary part:
the liquid fluctuation height can be calculated according to the following formula:
where h is the height of the receiver above the surface, since the speed of sound in air is known, and can be obtained by measuring the time of flight of the acoustic signal transmitted from the acoustic source and received by the acoustic receiver after following the interface reflection. D is a transmitter anddistance between receivers, LbIs the path length of the acoustic signal to the surface of the liquid. L isbThis can be given by:
Lb＝ΔL+La
wherein L isaIs the path length of the acoustic signal to the liquid surface at another time, Δ L is the change in the two reflected paths:
Δ h is related to the phase shift as follows:
where θ represents the acoustic incident angle, λ is the wavelength, Δ θ is the variation of the acoustic incident angle, and when Δ θ is sufficiently small:
the processor uses the results to scale the phase fluctuation to a spatial surface fluctuation.
The local height of the liquid surface in the target region fluctuates with time, and the measured height fluctuations can be used to infer liquid flow characteristics (surface roughness, flow depth, flow rate, volumetric flow rate, etc.). The relationship between flow rate and wave height is illustrated here by experimental data: as shown in fig. 5, the experimental results of the root mean square fluctuation height of the liquid surface and the average flow velocity v (vertical axis) in the experimental water flow. The strong correlation between the two variables means that the wave height can be used to estimate the average flow velocity in a real channel.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (5)
1. An apparatus for detecting a fluctuation characteristic of a liquid level based on an acoustic signal, characterized in that: comprising a signal transmitting module for generating an acoustic signal and transmitting the acoustic signal from a first known point to a point on the surface of the liquid; the signal receiving module is used for receiving the acoustic signal which reaches a second known point after being reflected from the surface of the liquid; a processor for processing the detected acoustic signals, monitoring changes in phase shift between the transmitted and received acoustic signals, and using the changes in phase shift to indicate fluctuations in the height of the liquid surface; the signal transmitting module and the signal receiving module are fixed above a target area to be detected and are respectively connected with the processor;
the signal transmitting module comprises a signal generator and a transducer, and the signal receiving module comprises an acoustic signal receiver, a transducer and a wireless communication module.
2. A method for detecting liquid level fluctuation characteristics based on acoustic signals is characterized in that: the method comprises the following specific steps:
s1, the signal transmitting module transmits the acoustic signal from the sound source to at least one target area on the liquid surface;
s2, after the acoustic signal is reflected from the target area, an acoustic receiver in the signal receiving module receives the acoustic signal;
s3, the processor periodically processes the detected acoustic signals, measures phase shifts of the transmitted and received acoustic signals, determines phase change information based on a first phase shift of the first acoustic signal and a second phase shift of the second acoustic signal and uses the phase shifts to indicate fluctuations in local elevation of the liquid interface in the target region over time.
3. The method and the device for detecting the liquid level fluctuation characteristic based on the acoustic signal according to claim 2, wherein: the first acoustic signal is an acoustic signal emitted at a first time, the second acoustic signal is an acoustic signal emitted at a second time, the first phase shift represents a time-dependent phase shift of the first acoustic signal between the first time and its reflection, and the second phase shift represents a time-dependent phase shift of the second acoustic signal between the second time and its reflection.
4. The method and the device for detecting the liquid level fluctuation characteristic based on the acoustic signal according to claim 2, wherein: the phase shift is calculated in relation to the height of the fluctuation of the liquid interface as follows: calculating a Hilbert transform of a transmitted and received acoustic signal, the transmitted acoustic signal Ve(t) and the received acoustic signal Vr(t) hilbert transform:
Ae(t) and Ar(t) amplitude of the transmitted and received acoustic data, w, respectivelysIs the excitation frequency of the signal generator, and phisIs the phase of the acoustic data transmitted at time t-0, the processor determines the phase shift of each acoustic signal, Δ φ (t), by means of a Hilbert transform, by taking the natural logarithm of the ratio of the analysis signals between the transmitted and received acoustic signals, where IM is the imaginary part:
the liquid fluctuation height Δ h is calculated according to the following formula:
where h is the height of the signal receiver above the liquid surface, D is the distance between the signal generator and the signal receiver, LbIs the path length of the acoustic signal to the liquid surface:
Lb＝ΔL+La
wherein L isaIs another time acoustic signal to the liquidThe path length of the surface, Δ L, is the variation of two reflected paths:
Δ h is related to the phase shift as follows:
λ is the wavelength, θ represents the acoustic incident angle, Δ θ represents the variation of the acoustic incident angle, and the processor uses the result to scale the phase fluctuation to a spatial surface fluctuation.
5. The method and the device for detecting the liquid level fluctuation characteristic based on the acoustic signal according to claim 2, wherein: the height h of the signal receiver above the liquid surface is obtained by measuring the time of flight of the acoustic signal received from the signal generator and by the signal receiver after following the interface reflection.
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- 2019-08-30 CN CN201910815457.0A patent/CN110631957A/en active Pending
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| CN2637709Y (en) * | 2003-08-14 | 2004-09-01 | 冉训 | Well drilling liquid level ultrasonic wave monitoring device |
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| WO2012117261A1 (en) * | 2011-03-03 | 2012-09-07 | University Of Bradford | Methods and apparatus for detection of fluid interface fluctuations |
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