Non-contact measuring method and device for medium pressure in pipeline based on laser ultrasound

Abstract

The invention provides a non-contact measurement method and device for medium pressure in a pipeline based on laser ultrasound, and belongs to the technical field of pressure measurement. The method comprises the following steps: adjusting a plane where an ultrasonic surface wave excitation light path and a detection light path are located to be perpendicular to a test pipeline; when the medium pressure in the test pipeline is zero, driving a laser light source to emit a laser pulse to excite an ultrasonic surface wave signal, and obtaining an ultrasonic surface wave initial frequency f0 by adopting a Fourier frequency analysis method; when the test pipeline is in a working state, namely the pipeline medium is pressurized, measurement is started, and the real-time frequency f of the ultrasonic surface wave is obtained; a pressurization test is carried out in the test pipeline, and the value of a coefficient k is obtained; and finally obtaining the real-time pressure P of the pipeline medium. The invention belongs to a novel mechanical sensor, can realize higher-precision measurement of the pressure of a medium in a pipeline, has the advantages of long-distance excitation and receiving, and can be applied to detection under severe conditions of acid, alkali, radiation and the like.

Description

Technical Field

[0001] The present invention relates to a non-contact measurement method and device for the pressure of the medium inside a pipeline based on laser ultrasound, belonging to the technical field of pressure measurement. Background Art

[0002] Ultrasonic pressure measurement can obtain the medium pressure information by detecting ultrasonic signals, and has the advantages of not disturbing the fluid flow field, having no mechanical inertia, fast transient response, strong dynamic measurement ability, and convenient installation. By studying the different acoustic characteristics of the liquid in the pipeline under different pressures, the relationship between pressure and ultrasonic sound speed is established through a large amount of test data, and finally the pressure value in the pipeline liquid is deduced by measuring the ultrasonic propagation speed.

[0003] In the current existing ultrasonic pressure measurement research, since the emission of longitudinal waves or transverse waves is relatively simple, ultrasonic longitudinal waves or transverse waves are basically used for measurement. For example, the invention patent "Non-invasive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology" with the patent number 2021116701497, the invention patent "A method for non-invasive detection of the fluid pressure in the liquid-filled pipeline of a hydraulic system" with the patent number 202310503782X, and the invention patent "An ultrasonic measurement device and measurement method for the pressure of the liquid medium inside a pipeline" with the patent number 2023105057043 propose a measurement method based on ultrasonic transverse waves.

[0004] The above methods and explorations are all based on ultrasonic longitudinal waves or transverse waves, but there are still some deficiencies that need to be improved urgently:

[0005] First of all, the acoustoelastic effect of the pressure vessel is very weak and is easily interfered. The change in the transit time caused by the pressure is very small. The accurate measurement of the pressure depends on the high-precision measurement of the transit time. The properties of the ultrasonic probe, the installation of the probe, the ultrasonic excitation and reception circuits, and the coupling agent will all have a greater impact on the transit time. The measurement accuracy of the existing ultrasonic pressure measurement methods is relatively low. At present, how to reduce or eliminate the influence of these factors has become an urgent problem to be solved.

[0006] Secondly, for pipelines of different sizes, installation bases of different sizes and types need to be designed, which is not convenient to use. Moreover, the working characteristics such as the coupling agent, the installation of the probe, the starting vibration of the probe, and the ultrasonic excitation and reception circuits will all have a greater impact on the measurement. These factors all affect the improvement of the ultrasonic pressure measurement accuracy and greatly limit its popularization and application. Summary of the Invention

[0007] The purpose of the present invention is to provide a non-contact measurement method and device for the pressure of the medium inside a pipeline based on laser ultrasound to solve the problem of relatively low measurement accuracy in the prior art when using longitudinal waves or transverse waves for measurement.

[0008] The technical solution of the present invention is as follows:

[0009] A non-contact measurement method for the pressure of the medium inside a pipeline based on laser ultrasound, comprising the following steps:

[0010] Step 1: Adjust the positions of the total reflection mirror and the focusing lens so that the laser pulse emitted by the laser light source is focused on the surface of the test pipeline to form an ultrasonic surface wave excitation optical path, and the detection point of the laser interferometer is focused on the surface of the test pipeline to form a detection optical path, and adjust so that the plane where the ultrasonic surface wave excitation optical path and the detection optical path are located together is perpendicular to the test pipeline;

[0011] Step 2: When the pressure of the medium inside the test pipeline is zero, drive the laser light source to emit a laser pulse. After the laser pulse is deflected by the total reflection mirror, it hits the outer surface of the test pipeline through the focusing lens, and two surface wave signals propagating periodically in opposite directions are excited in the pipe wall of the test pipeline. The laser interferometer remains in the working state and collects the ultrasonic surface wave signals propagating periodically in the pipe wall of the test pipeline until the ultrasonic surface wave signals decay to a level that the laser interferometer cannot detect, and the initial frequency f0 of the ultrasonic surface wave is obtained by using the Fourier frequency analysis method;

[0012] Step 3: Start the measurement when the test pipeline is in the working state, that is, when the pipeline medium is pressurized. Drive the laser light source to emit a laser pulse. After the laser pulse is deflected by the total reflection mirror, it hits the outer surface of the test pipeline through the focusing lens, and two surface wave signals propagating periodically in opposite directions are excited in the pipe wall of the test pipeline. The laser interferometer remains in the working state and collects the ultrasonic surface wave signals propagating periodically in the pipe wall until the ultrasonic surface signal wave decays to a level that the laser interferometer cannot detect, and the real-time frequency f of the ultrasonic surface wave is obtained by using the Fourier frequency analysis method;

[0013] Step 4: Conduct a pressure test experiment in the test pipeline and obtain the value of the comprehensive proportionality coefficient k;

[0014] Step 5: Obtain the real-time pressure P of the pipeline medium from the initial frequency f0 of the ultrasonic surface wave, the real-time frequency f of the ultrasonic surface wave, and the comprehensive proportionality coefficient k through the frequency-pressure calculation formula.

[0015] Further, in step 5, the real-time pressure P of the pipeline medium is obtained through the following frequency-pressure calculation formula:

[0016] P = k(f - f0)

[0017] Where k is the comprehensive proportionality coefficient between the propagation frequency of the ultrasonic array surface wave and the pipeline pressure, f is the real-time frequency, and f0 is the initial frequency.

[0018] Further, in step 4, specifically, a pressure test is carried out in the test pipeline. The magnitude of the internal pressure P is changed through a standard pressure source, multiple groups of propagation data of ultrasonic surface waves in the pipe wall are obtained, and frequency signals are extracted. Linear fitting is performed by the least square method to obtain the value of the comprehensive proportionality coefficient k.

[0019] Further, the laser light source uses a Q-switched laser.

[0020] Further, the laser light source, the total reflection mirror, the focusing lens, and the laser interferometer are not in contact with the test pipeline.

[0021] A non-contact measurement device for the pressure of the medium inside a pipeline based on laser ultrasound using the method described in any one of the above, including a laser light source, a total reflection mirror, a focusing lens, and a laser interferometer. The laser pulse emitted by the laser light source is reflected by the total reflection mirror and then converges on the surface of the test pipeline through the focusing lens to form an ultrasonic surface wave excitation optical path. Two ultrasonic surface waves in opposite directions are excited in the test pipeline by the laser pulse. The detection point of the laser interferometer is focused on the surface of the test pipeline to form a detection optical path, and the ultrasonic surface wave excitation optical path and the detection optical path are in the same plane perpendicular to the test pipeline.

[0022] Further, it also includes a computer host. The computer host drives the laser light source to emit laser pulses and analyzes the data collected by the laser interferometer, calculates the measurement data, stores the measurement data in the database, and displays it on the main interface of the program.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. For this non-contact measurement method and device for the pressure of the medium inside a pipeline based on laser ultrasound, the laser ultrasound transmits around the pipeline multiple times. Using the Fourier frequency analysis method, compared with conventional time difference methods and other methods, it can achieve higher-precision measurement of the pressure of the medium inside the pipeline. By using ultrasonic surface wave signals, the signals only propagate on the surface layer of the pipe wall and do not penetrate the medium inside the pipeline, and there is no need for special calibration for different media. At the same time, the laser light source and the laser interferometer can be placed far away from the test pipeline, having the advantages of remote excitation and reception, and can be applied to detection under harsh conditions such as acids, alkalis, and radiation, and has the potential for on-line detection and quality monitoring development in industry.

[0025] 2. For this non-contact measurement method and device for the pressure of the medium inside a pipeline based on laser ultrasound, the ultrasonic surface wave is generated by laser irradiation, eliminating the need to design a special fixture, being simple to use and having a low implementation difficulty; laser ultrasound does not require a coupling agent, and can eliminate the additional influences caused by probe installation, probe oscillation mode, and coupling agent in the conventional electro-ultrasonic measurement process.

[0026] III. The non-contact measurement method and device for the pressure of the medium inside the pipeline based on laser ultrasound have higher accuracy than the traditional ultrasonic time difference method because Fourier analysis collects ultrasonic multiple propagation signals. When compared with a piston pressure gauge of class 0.02 in the laboratory, the deviation between the system display value and the standard pressure value within the pressure range of (0 - 20) MPa is less than ±1% FS, indicating a significant improvement in metrological performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is a schematic illustration of the non-contact measurement method for the pressure of the medium inside the pipeline based on laser ultrasound according to an embodiment of the present invention;

[0028] Figure 2 FIG. is a schematic diagram showing the relationship between the measured stress of the aluminum alloy pipe wall and the propagation speed of the ultrasonic surface wave in the embodiment;

[0029] Figure 3 FIG. is a schematic structural diagram of the non-contact measurement device for the pressure of the medium inside the pipeline based on laser ultrasound in the embodiment;

[0030] Wherein: 1 - laser light source; 2 - total reflection mirror; 3 - focusing lens; 4 - test pipeline; 5 - laser interferometer; 6 - computer mainframe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] The embodiment provides a non-contact measurement method for the pressure of the medium inside the pipeline based on laser ultrasound, as Figure 1 , including the following steps,

[0033] Step 1: Adjust the positions of the total reflection mirror 2 and the focusing lens 3 so that the laser pulse emitted by the laser light source 1 is focused on the surface of the test pipeline 4 to form an ultrasonic surface wave excitation optical path, and the detection point of the laser interferometer 5 is focused on the surface of the test pipeline 4 to form a detection optical path. Adjust to make the plane where the ultrasonic surface wave excitation optical path and the detection optical path are located perpendicular to the test pipeline 4.

[0034] In step 1, the laser light source 1 uses a Q-switched laser. The laser light source 1, the total reflection mirror 2, the focusing lens 3, and the laser interferometer 5 are all not in contact with the test pipeline.

[0035] Step 2: When the pressure of the medium in the test pipeline is zero, drive the laser light source 1 to emit laser pulses. After the laser pulses are redirected by the total reflection mirror 2, they pass through the focusing lens 3 and hit the outer surface of the test pipeline 4, generating surface wave signals propagating periodically in two opposite directions inside the wall of the test pipeline 4. The laser interferometer 5 remains in working state to collect the ultrasonic surface wave signals propagating periodically in the wall of the test pipeline 4 until the ultrasonic surface wave signals decay to a level that the laser interferometer 5 can no longer detect. The initial frequency f0 of the ultrasonic surface wave is obtained by using the Fourier frequency analysis method.

[0036] Step 3: Start the measurement when the test pipeline is in the working state, i.e., when the pipeline medium is pressurized. Drive the laser light source 1 to emit laser pulses. After the laser pulses are redirected by the total reflection mirror 2, they pass through the focusing lens 3 and hit the outer surface of the test pipeline 4, generating surface wave signals propagating periodically in two opposite directions inside the wall of the test pipeline 4. The laser interferometer 5 remains in working state to collect the ultrasonic surface wave signals propagating periodically in the wall until the ultrasonic surface signal waves decay to a level that the laser interferometer 5 can no longer detect. The real-time frequency f of the ultrasonic surface wave is obtained by using the Fourier frequency analysis method.

[0037] Step 4: Conduct a pressure test experiment in the test pipeline and obtain the value of the comprehensive proportionality coefficient k. Specifically, conduct a pressure test experiment in the test pipeline, change the magnitude of the internal pressure P through a standard pressure source, obtain multiple sets of propagation data of ultrasonic surface wave signals in the pipeline wall, extract the frequency signals, and perform linear fitting by the least squares method to obtain the value of the comprehensive proportionality coefficient k.

[0038] Step 5: Obtain the real-time pressure P of the pipeline medium from the initial frequency f0 of the ultrasonic surface wave, the real-time frequency f of the ultrasonic surface wave, and the comprehensive proportionality coefficient k through the frequency-pressure calculation formula.

[0039] According to the principle of the interaction between laser and matter, two ultrasonic surface waves propagating in opposite directions can be excited when the laser pulses act on the outer wall of the pipeline. Since the pipeline is circular, the laser ultrasonic surface waves will propagate repeatedly around the pipeline. Therefore, the laser interferometer 5 will collect the periodic signals of the laser ultrasonic surface waves propagating around the pipeline until the laser ultrasonic surface waves decay to a level that the laser interferometer 5 can no longer detect. Since there is a theoretically linear relationship between the internal pressure P of the pipeline medium and the internal stress σ of the pipeline wall:

[0040] P = k1(σ - σ0)

[0041] where σ0 is the wall stress in the zero-pressure state and k1 is the proportionality coefficient between the internal pressure of the pipeline and the wall stress.

[0042] According to the acoustoelastic principle and through experimental verification, it is obtained that there is a linear relationship between the wall stress and the ultrasonic surface wave velocity:

[0043] Δσ = k2Δv → σ - σ0 = k2(v - v0)

[0044] Among them, k2 is the proportionality coefficient between the propagation speed of the ultrasonic surface wave and the wall stress of the pipe, v0 is the propagation speed of the ultrasonic surface wave in the zero-pressure state, and σ and v are the wall stress and the propagation speed of the ultrasonic surface wave when the pipe pressure is P.

[0045] When the outer circumference of the pipeline to be measured is D, the time interval of the periodic surface wave signal received by the laser interferometer 5 is: The frequency of the periodic surface wave signal it receives is That is:

[0046]

[0047] Among them, Δσ is the stress change amount, Δv is the velocity change amount, and f0 is the initial frequency of the ultrasonic surface wave in the zero-pressure state. In summary, it can be obtained that:

[0048] P = k(f - f0)

[0049] Among them, k is the comprehensive proportionality coefficient between the propagation frequency of the ultrasonic array surface wave and the pipe pressure.

[0050] For this non-contact measurement method of the pressure of the medium inside the pipe based on laser ultrasound, the laser ultrasound transmits around the pipe multiple times. Using the Fourier frequency analysis method compared with conventional time difference methods, it can achieve higher-precision measurement of the pressure of the medium inside the pipe. By using ultrasonic surface wave signals, the signals only propagate on the surface layer of the pipe wall without penetrating the medium inside the pipe, and there is no need for special calibration for different media. At the same time, the laser light source 1 and the laser interferometer 5 can be placed far away from the test pipeline 4, with the advantages of remote excitation and reception. The set distance depends on the focal lengths of the two optical paths, and it can be applied to detect in harsh conditions such as acids, alkalis, and radiation, and has the potential for on-line detection and quality monitoring development in industry.

[0051] For this non-contact measurement method of the pressure of the medium inside the pipe based on laser ultrasound, the ultrasonic surface wave is generated by laser irradiation, without the need to design a special fixture and is easy to use; laser ultrasound does not require a coupling agent, and can eliminate the additional influences caused by the probe installation, the probe oscillation mode, and the coupling agent during the conventional electro-ultrasonic measurement process.

[0052] Such as Figure 3, the embodiment also provides a non-contact measurement device for the pressure of the medium inside the pipeline based on laser ultrasound, which adopts the method described in any one of the above, and includes a laser light source 1, a total reflection mirror 2, a focusing lens 3 and a laser interferometer 5. The laser pulse emitted by the laser light source 1 is reflected by the total reflection mirror 2 and then converges on the surface of the test pipeline through the focusing lens 3 to form a laser light source optical path. The laser pulse excites ultrasonic surface waves in two opposite directions on the test pipeline. The detection point of the laser interferometer 5 focuses on the surface of the test pipeline 4 to form a laser interferometer optical path, and the laser pulse emission optical path and the detection optical path of the laser interferometer 5 are in the same plane perpendicular to the test pipeline 4.

[0053] It further includes a computer host 6. The computer host 6 drives the laser light source 1 to emit laser pulses and analyzes the data collected by the laser interferometer 5, calculates the measurement data, stores the measurement data in the database and displays it on the main program interface.

[0054] For this non-contact measurement method and device for the pressure of the medium inside the pipeline based on laser ultrasound, the laser interferometer 5 is located on the side of the test pipeline, and the detection point also focuses on the surface of the test pipeline 4. The laser interferometer 5 receives periodic ultrasonic surface wave signals propagating in the pipe wall of the test pipeline multiple times. The periodic surface wave signals collected by the laser interferometer 5 are extracted for their frequencies by using the Fourier transform method.

[0055] For this non-contact measurement method and device for the pressure of the medium inside the pipeline based on laser ultrasound, since the Fourier analysis collects the ultrasonic multiple propagation signals, it has higher accuracy than the traditional ultrasonic time difference method. Compared with a 0.02-level piston pressure gauge in the laboratory, the deviation between the system display value and the standard pressure value within the pressure range of (0 - 20) MPa is less than ±1% FS, and the metrological performance has been greatly improved.

[0056] This non-contact measurement method and device for the pressure of the medium inside the pipeline based on laser ultrasound belong to a new type of mechanical sensor. Based on laser ultrasound technology, it uses laser pulses to excite surface waves on the pipeline surface, and inversely calculates the pressure of the medium inside the pipeline by measuring the frequency of the ultrasonic surface waves, realizing non-contact measurement of the pressure of the medium inside the pipeline. At the same time, by using the characteristics of the cylindrical shape of the pipeline, the ultrasonic multiple propagation waveforms are obtained, and with the help of the Fourier frequency analysis method, the measurement accuracy is significantly improved. It can be used in the manufacturing of related facilities such as electric vehicles to realize the pressure measurement of the medium fluid inside the pipeline.

[0057] The above is only the preferred embodiment of the present invention. It should be noted that: for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A non-contact measurement method for medium pressure in a pipeline based on laser ultrasound, characterized in that: The following steps are included: Step 1, adjusting the positions of the total reflective mirror and the focusing lens so that the laser pulse emitted by the laser light source is focused on the surface of the test pipe and forms an ultrasonic surface wave excitation optical path, and the detection point of the laser interferometer is focused on the surface of the test pipe to form a detection optical path, and adjusting so that the plane where the ultrasonic surface wave excitation optical path and the detection optical path are located is perpendicular to the test pipe; Step 2, when the medium pressure in the test pipeline is zero, drive the laser light source to emit laser pulses, the laser pulses are deflected by the total reflection mirror, hit the outer surface of the test pipeline through the focusing lens, and excite two surface wave signals propagating periodically in opposite directions on the pipe wall of the test pipeline, the laser interferometer keeps working, collects the ultrasonic surface wave signals propagating periodically in the pipe wall of the test pipeline, until the ultrasonic surface wave signals decay to the point that the laser interferometer cannot detect them, and uses the Fourier frequency analysis method to obtain the initial frequency f0 of the ultrasonic surface wave; Step 3: When the test pipeline is in working state, i.e., when the pipeline medium is pressurized, measurement is started, and the laser light source is driven to emit laser pulses. After being deflected by the total reflective mirror, the laser pulses hit the outer surface of the test pipeline through the focusing lens, and two surface wave signals propagating periodically in opposite directions are stimulated in the pipe wall of the test pipeline. The laser interferometer remains in working state, and the ultrasonic surface wave signals propagating periodically in the pipe wall are collected until the ultrasonic surface signal wave decays to the point where the laser interferometer cannot detect it, and the real-time frequency f of the ultrasonic surface wave is obtained by the Fourier frequency analysis method; Step 4: Perform a pressure test in the test pipeline and obtain the value of the comprehensive proportional coefficient k; Step 5: The real-time pressure P of the pipeline medium is obtained by using the ultrasonic surface wave initial frequency f0, the ultrasonic surface wave real-time frequency f and the comprehensive proportional coefficient k through the frequency-pressure calculation formula.

2. The non-contact measurement method of the medium pressure in a pipeline based on laser ultrasound according to claim 1, characterized in that: In step 5, the real-time pressure P of the pipeline medium is obtained by the following frequency pressure calculation formula: P=k(f-f0) Wherein, k is the comprehensive proportional coefficient between the ultrasonic array surface wave propagation frequency and the pipeline pressure, f is the real-time frequency of the ultrasonic surface wave, and f0 is the initial frequency of the ultrasonic surface wave.

3. The non-contact measurement method of medium pressure in a pipeline based on laser ultrasound according to claim 1, characterized in that: In step 4, specifically, a pressurized test is carried out in the test pipe, the internal pressure P is changed by a standard pressure source, multiple sets of ultrasonic surface wave signal propagation data in the pipe wall are obtained, and the frequency signal is extracted. A linear fit is performed by the least squares method to obtain the value of the comprehensive proportional coefficient k.

4. The non-contact measurement method for medium pressure in a pipeline based on laser ultrasound according to any one of claims 1 to 3, characterized in that: The laser light source adopts Q-switched laser.

5. The non-contact measurement method for medium pressure in a pipeline based on laser ultrasound according to any one of claims 1 to 3, characterized in that: The laser light source, total reflective mirror, focusing lens and laser interferometer do not contact the test pipe.

6. A non-contact measuring device for medium pressure in a pipeline based on laser ultrasound using the method according to any one of claims 1 to 5, characterized in that: It includes a laser light source, a total reflection mirror, a focusing lens and a laser interferometer. The laser pulse emitted by the laser light source is reflected by the total reflection mirror and then converged on the surface of the test pipe through the focusing lens to form an ultrasonic surface wave excitation light path. The laser pulse excites two ultrasonic surface waves in opposite directions in the test pipe. The detection point of the laser interferometer is focused on the surface of the test pipe to form a detection light path, and the ultrasonic surface wave excitation light path and the detection light path are in the same plane perpendicular to the test pipe.

7. The non-contact measuring device for medium pressure in a pipeline based on laser ultrasound according to claim 5, characterized in that: It also includes a computer host, which drives the laser light source to emit laser pulses and analyzes the data collected by the laser interferometer, calculates the measurement data, stores the measurement data in a database, and displays it in the main interface of the program.

Images