CN108362431B - non-intrusive pressure detection method based on time delay interval between adjacent longitudinal waves - Google Patents
non-intrusive pressure detection method based on time delay interval between adjacent longitudinal waves Download PDFInfo
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
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Abstract
The invention discloses a non-intrusive pressure detection method and a non-intrusive pressure measurement system based on time delay intervals between adjacent longitudinal waves. The method selects the time delay interval between adjacent longitudinal waves (including the time delay interval between critical refraction longitudinal wave and first reflection longitudinal wave and between adjacent reflection longitudinal waves) as a measurement parameter; establishing a pressure measurement model of the relation between the pressure in the container and the time delay interval between adjacent longitudinal waves by utilizing the ultrasonic acoustic-elastic effect; by measuring the time delay interval, an estimate of the vessel pressure can be achieved. The method comprises the steps of simultaneously measuring the transition time of critical refraction longitudinal waves and a plurality of reflection longitudinal waves generated under the same excitation pulse by adopting a programmable shielding window technology and a TDC (digital time measuring chip), and then calculating to obtain the time delay interval between the adjacent longitudinal waves. The method can overcome the influence caused by the inconsistency of the starting vibration time of the ultrasonic probe, the inconsistency of the couplant, the ultrasonic excitation and receiving circuit, the probe fixing characteristic and the like, and improve the precision of pressure measurement.
Description
Technical Field
the invention belongs to the technical field of non-intrusive pressure detection, and particularly relates to a pressure container pressure detection method and a pressure container pressure measurement system based on time delay intervals between adjacent longitudinal waves.
background
the pressure equipment has wide application, relates to a plurality of fields of industrial production and is closely related to the life of people. Due to wide application background and large quantity, the equipment often bears inflammable, explosive, extremely toxic or corrosive media, and therefore serious safety and economic loss is often caused once accidents happen. The regular detection and maintenance of such equipment is one of measures for effectively reducing the occurrence of accidents, and the pressure detection is an important and effective technology.
Pressure sensing is largely divided into two categories, depending on whether the measuring device is in contact with the medium in the container, namely: intrusive pressure detection and non-intrusive pressure detection. The traditional interventional pressure detection method mainly comprises the following steps: a liquid column type pressure detection method, an elastic type pressure detection method, an electrical remote transmission type pressure detection method, and a physical property type pressure detection method. For the above-mentioned several methods of invasive pressure detection, it is often necessary to open holes in the container, and therefore, the following disadvantages may occur: 1) stress concentration is easily generated at the position of the opening, the stress peak value can reach 3-6 times of the stress of the film, and the service life of the container is shortened. 2) It is inconvenient to add additional test points. 3) Most pressure vessels do not allow for venting. For the above disadvantages, the non-intrusive pressure detection method is improved to a certain extent, and the non-intrusive pressure detection mainly includes: 1) strain method, i.e. indirectly reflecting pressure by the change in resistance of the strain gauge when subjected to a force. 2) Capacitive method, which performs pressure detection by measuring the change in dielectric constant caused by a change in pressure. 3) The ultrasonic method realizes pressure detection according to the change relation of signal amplitude and propagation speed of ultrasonic waves in a detected medium along with pressure, and therefore, according to the difference of a measurement principle and sensitive parameters, the ultrasonic method comprises two main categories: methods based on amplitude attenuation and methods based on wave velocity variation.
Although the traditional non-intrusive detection method avoids the structural damage of the measured object, some defects still exist. For the strain gauge method, an output signal is weak, the anti-interference capability is poor, and the main problems of plastic deformation and zero drift exist. Furthermore, the non-linearity problem at high strains and strain gage mounting also impose certain limitations on the application of this method. In the capacitance method, the dielectric constant is easily affected by the dielectric composition and temperature, and is easily affected by the electromagnetic environment, and is generally used for a small-diameter object. Ultrasonic pressure detection based on amplitude attenuation is susceptible to medium properties and temperature due to the propagation of ultrasonic waves in the medium. In addition, the installation mode of the probe and the couplant can introduce large interference, and when the wall of the container is thin, an incident signal and a reflected signal can be overlapped, so that a real received signal cannot be distinguished. The ultrasonic pressure detection based on the wave velocity change overcomes the influence caused by a medium, but factors such as probe installation, temperature, couplant and the like still have certain influence on the pressure detection precision.
Recently, pressure measurement methods based on wave velocity changes have been extensively studied, and different waveforms (critical refracted longitudinal waves, reflected longitudinal waves, rayleigh waves, etc.) are used for pressure detection and stress analysis, and the skilled person has conducted beneficial research in this regard, representing the results as follows:
The invention discloses a nondestructive pressure measuring method and a nondestructive pressure measuring device based on Rayleigh surface waves (application number CN200410066996.2), and provides a non-intrusive pressure measuring method based on Rayleigh surface waves.
The invention patent 'pressure vessel pressure detection method and measurement system based on reflected longitudinal waves' (application number: CN201410318440.1) provides a pressure vessel pressure detection method based on reflected longitudinal waves and a measurement model with temperature compensation.
the document "thin-walled container temperature and pressure measurement method based on Rayleigh waves" (academic edition, 2009, 43 (8): 1419-. (academic thesis)
The method and the exploration respectively adopt different types of ultrasonic waves to realize non-intrusive pressure detection, and the influence of temperature is improved. There are still some deficiencies to be improved. Firstly, the acoustoelastic effect of a pressure vessel is very weak and easily disturbed, the variation of the transit time caused by the pressure is very small, and the accurate measurement of the pressure depends on the high-precision measurement of the transit time. However, temperature, the properties of the ultrasonic probe, the installation of the probe, the ultrasonic excitation and reception circuit, the coupling agent, and the like all have great influence on the transit time, and how to reduce or eliminate the influence of the factors becomes a problem to be solved urgently. Although the measurement mode of using two-wave reference can reduce the influence of temperature, but can not completely eliminate, and a plurality of ultrasonic probes are needed, and the measurement device is complex. The modeling method based on multi-wave fusion integrates the information of each waveform, improves the measurement accuracy to a greater extent, but the working characteristics of coupling agent, probe installation, probe starting oscillation and the like, ultrasonic excitation and receiving circuits and the like have great influence on the ultrasonic transit time.
disclosure of Invention
The invention designs a set of ultrasonic pressure detection system based on TDC-GP22 aiming at the problems of the existing non-intrusive pressure detection method, and provides a pressure measurement method based on the time delay interval between adjacent longitudinal waves. According to the method, based on the relationship between the delay interval and the pressure of adjacent longitudinal waves and by combining the programmable shielding window technology and the TDC time digital chip, the influence of the starting time inconsistency of the ultrasonic probe, probe fixation, a coupling agent, an ultrasonic excitation and receiving circuit on the ultrasonic transit time is effectively eliminated, and the temperature interference is reduced. Based on the fusion modeling idea of a plurality of adjacent longitudinal wave time delay intervals, the influence of the measurement error of a single time delay interval on pressure detection is reduced. In addition, the time delay interval comprises information of temperature and pressure, and the temperature is contained in the measurement model as an implicit variable, so that the method can avoid detection of the temperature and simplify a measurement device.
The theoretical basis of the invention is as follows:
According to the sono-elastic effect, a variation of the pressure inside the container causes a critical refracted longitudinal wave LCRAnd the wave velocity of the reflected longitudinal wave is changed, and the propagation delay of the reflected longitudinal wave is changed, so that the delay interval between the adjacent longitudinal waves is also changed. The pipe wall usually has a certain thickness and can therefore be considered as being present as an outer pipe wall and an inner pipe wall. The invention selects the time delay interval between adjacent longitudinal waves (including the time delay interval between the critical refraction longitudinal wave and the first reflection longitudinal wave and the time delay interval between the adjacent reflection longitudinal waves) as a measurement parameter. The ultrasonic waves are generated by the excitation probe and then incident on the outer pipe wall of the pressure vessel at a critical angle, the path of which propagating in the pipe wall of the pressure vessel is shown in fig. 2.
When incident longitudinal wave is incident at a first critical angle, wave mode conversion occurs at the interface between the ultrasonic probe and the pressure vessel wall, and critical refracted longitudinal wave L is generated at the outer wallCRAnd refracted transverse wave, critical refracted longitudinal wave LCRthe outer pipe wall is propagated to the receiving probe to be received; the refracted transverse wave propagates in the pipe wall of the pressure container and is reflected at the inner pipe wall to generate a first inner wall reflected longitudinal wave Lre-I1st and a first reflected transverse wave Sre-1 st; according to Snell's law, the reflection angle of the first internal reflected longitudinal wave Lre-I1st is 90 degrees and propagates along the inner tube wall; the first reflected transverse wave Sre-1st continues to propagate in the pipe wall of the pressure container and is reflected again at the outer pipe wall to generate a first reflected longitudinal wave Lre-1st and a second reflected transverse wave Sre-2nd, wherein the first reflected longitudinal wave Lre-1st propagating along the outer pipe wall to the receiving probe, the second reflected transverse wave Sre-2nd continuing to propagate in the pressure vessel wall and being reflected again at the inner pipe wall, resulting in a second inner wall reflected longitudinal wave Lre-I2nd and a third reflected transverse wave Sre-3rd, the second inner wall reflected longitudinal wave Lre-I2nd propagating along the inner pipe wall, and the third reflected transverse wave Sre-3rd continuing to propagate in the pressure vessel wall, in such a way that the transverse wave propagating in the pressure vessel wall undergoes multiple reflections at the outer pipe wall and at the inner pipe wall, resulting in a plurality of reflected longitudinal waves propagating along the inner pipe wall and a plurality of reflected longitudinal waves propagating along the outer pipe wall, the receiving probe fixed to the outer pipe wall receiving the critically refracted longitudinal wave LCRAnd ultrasonic signals such as a first reflected longitudinal wave Lre-1st, a second reflected longitudinal wave Lre-2nd, a third reflected longitudinal wave Lre-3rd, and a fourth reflected longitudinal wave Lre-4 th.
the propagation of ultrasonic waves in the pressure vessel wall generates a critically refracted longitudinal wave and a plurality of reflected longitudinal waves. According to the acoustic elasticity theory, the thin shell theory and the relation between time delay and wave speed, the propagation time delay of the critical refraction longitudinal wave and the reflection longitudinal wave is in a linear relation with pressure and temperature. In the case of a constant pressure vessel and a constant pressure, the transit time interval of the two received signals is fixed. However, when the pressure changes, the interval between adjacent longitudinal waves changes. The time-of-flight interval between adjacent longitudinal waves will be linear with pressure and temperature, with the theoretical relationship being as follows:
Wherein, delta is the thickness of the pressure vessel wall, VSIs the velocity of the transverse wave, V, in the vesselLIs the longitudinal wave velocity in the container, and beta is the refraction angle of the ultrasonic wave. The relationship between the ultrasonic wave velocity and the pressure can be expressed as follows:
Wherein, is Δ VL、ΔVSIs the wave velocity variation of longitudinal waves and transverse waves,The wave velocity L of longitudinal wave and transverse wave in the initial state1、L2E is the elastic modulus, delta is the wall thickness of the container, R is the average radius of the container, and p is the pressure in the container. When the pressure condition changes, and the ultrasonic receiving probe receives a plurality of signals, the transit time interval between adjacent longitudinal waves changes, and a plurality of adjacent longitudinal wave delay intervals are generated, for example: Δ tLre1_L、ΔtLre2_1、ΔtLre3_2、ΔtLre4_3And the like.
The accuracy of pressure measurement depends on the accuracy of ultrasonic time delay measurement, and the accuracy and the reliability of measurement can be improved by adopting an information fusion method because the acoustic elastic effect of the pressure container is generally weaker and is easily influenced by interference factors. The pressure detection method of the invention can select the time delay interval (delta t) between the critical refraction longitudinal wave and the first reflection longitudinal waveLre1_L) The time delay interval (delta t) between the first reflected longitudinal wave and the second reflected longitudinal waveLre2_1) The time delay interval (delta t) between the second reflected longitudinal wave and the third reflected longitudinal waveLre3_2) And the time delay interval (delta t) between the third reflected longitudinal wave and the fourth reflected longitudinal waveLre4_3) And the isovariables are used as input variables of the pressure detection model and are fitted with the dependent variable container pressure to form the pressure detection model. Of course, the pressure measurement model may also be obtained by using a plurality of adjacent longitudinal wave delay intervals and temperatures as input variables. The model under the two modes is as follows:
p＝∑Ai·ΔtLrei_j+B·ΔT+C (3a)
p＝∑Ai·ΔtLrei_j+C (3b)
Wherein, the formula (3a) is a pressure measurement model including temperature compensation, the formula (3b) is a pressure measurement model not including temperature compensation, p is the pressure in the pressure container, Δ tLrei_jAnd delta T is the time delay interval of the ith and jth adjacent longitudinal waves and is the temperature variation.
In fact, however, the temperature information implied by the delay intervals between a plurality of adjacent longitudinal waves is utilized, so that the pressure estimation can be realized without measuring the temperature, namely, the pressure measurement model can directly adopt the formula (3b) without temperature independent variables.
Based on the theory, the invention adopts the following technical scheme:
The non-intrusive pressure detection method based on the time delay interval between adjacent longitudinal waves comprises the following steps:
1) Selecting a time delay interval between adjacent longitudinal waves as a measurement parameter, and arranging a pair of ultrasonic excitation and receiving probes on the outer surface of the pressure vessel; when the excitation wave excited by the excitation probe is incident from the outer surface of the pressure container at a first critical angle, the ultrasonic wave is reflected, refracted and subjected to wave mode conversion on the surface of the container for multiple times, and the receiving probe can sequentially receive the critical refracted longitudinal wave L propagating along the wall of the outer pipeCRAnd a plurality of reflected longitudinal wave signals; according to the sono-elastic effect, a variation of the pressure inside the container causes a critical refracted longitudinal wave LCRand the wave velocity change of the reflected longitudinal wave, which shows that the propagation delay of each longitudinal wave changes, so that the delay interval between adjacent longitudinal waves also changes;
2) Detecting time delay intervals between adjacent longitudinal waves under different container pressures, and constructing a pressure measurement model based on the time delay intervals between the adjacent longitudinal waves to obtain a relation between the pressure in the pressure container and the time delay intervals between the adjacent longitudinal waves;
3) and (3) calculating the pressure in the pressure container to be detected according to the pressure measurement model constructed in the step 2) and the time delay interval between adjacent longitudinal waves of the pressure container to be detected, thereby realizing the non-intrusive pressure detection of the pressure container.
Preferably, the method for measuring the time delay interval between adjacent longitudinal waves comprises the following steps: the method comprises the steps of simultaneously measuring the transition time of critical refraction longitudinal waves and a plurality of reflection longitudinal waves generated under the same excitation pulse by adopting a programmable shielding window technology and a TDC (digital time measuring chip), and then calculating to obtain the time delay interval between the adjacent longitudinal waves.
Preferably, the delay interval between adjacent longitudinal waves includes a delay interval between the critically refracted longitudinal wave and the first reflected longitudinal wave, and a delay interval between adjacent reflected longitudinal waves;
preferably, the expression of the pressure measurement model is as follows:
p＝∑Ai·ΔtLrei_j+C；
Wherein: Δ tLrei_jTime delay intervals of ith and jth adjacent longitudinal waves; a. theiIs Δ tLrei_jCorresponding fitting coefficients; p is Δ tLrei_jthe pressure in the corresponding pressure vessel to be tested.
The invention also aims to provide a pressure measurement system based on the time delay interval between adjacent longitudinal waves for realizing the method, which comprises a pressure test pump, a thermostat, an ultrasonic transmitting probe, a receiving probe and a TDC ultrasonic propagation time delay measurement device; the pressure test pump is connected with the inner cavity of the pressure container and is used for adjusting the pressure in the container; the pressure container is arranged in a constant temperature box, and the temperature of the pipe wall is controlled by the constant temperature box; the transmitting probe and the receiving probe are arranged on the outer surface of the pressure vessel, and a TDC-GP22 time digital chip is arranged in the TDC ultrasonic propagation delay measuring device and is used for receiving a plurality of longitudinal waves generated by the same ultrasonic excitation through the receiving probe.
the TDC time digital chip can realize the measurement of the transit time with higher precision and can carry out multiple measurements in a single measurement period. Therefore, the function can be used for measuring the time delay interval between adjacent longitudinal waves. The method can be used for acquiring signals for multiple times in a single excitation period, and effectively avoids the influence of factors such as probe excitation consistency, an ultrasonic excitation and receiving circuit, a coupling agent, temperature and the like on the transit time. The measuring device only needs a pair of excitation and receiving probes, thereby effectively simplifying the measuring device and the requirements on the installation of the probes.
Preferably, the pressure test pump is a manual pressure test pump, a digital pressure gauge is installed in the manual pressure test pump, and the pressure in the container is adjusted in a hydraulic pressure adjusting and controlling mode.
Preferably, the system further comprises an upper computer, wherein the pressure in the pressure container to be detected and the receiving time of each longitudinal wave are stored in the upper computer, and the upper computer is used for calculating the time delay interval between adjacent longitudinal waves and fitting a pressure calculation formula to realize pressure prediction based on the time delay interval between adjacent longitudinal waves.
compared with the background technology, the invention has the outstanding effects:
1) The time of flight of critical refraction longitudinal wave and multiple reflection longitudinal waves generated under the same excitation pulse can be measured by adopting programmable shielding window technology and TDC (digital time measuring chip). The method overcomes the ultrasonic transit time measurement error caused by the inconsistent starting time of the ultrasonic probe, and improves the measurement precision. The conventional measurement method is to measure the transit time of critical refracted longitudinal wave or reflected longitudinal wave under different excitation waves, and the oscillation starting time of the ultrasonic probe has certain fluctuation due to excitation voltage, temperature and the like, so that the transit time of each received wave is indirectly influenced.
2) the method adopts a pair of excitation and receiving probes, realizes the functions of a plurality of ultrasonic sensors (each received wave, including critical refraction longitudinal waves and each reflection longitudinal wave can be independently used for realizing pressure detection), and overcomes the influence of common mode factors such as couplant, excitation and receiving circuit noise and the like on the measurement of the transit time. The characteristics of the coupling agent, the excitation circuit and the receiving circuit are the same for each received waveform (critical refracted longitudinal wave and each reflected longitudinal wave), thereby overcoming the influence of the factors on the time delay interval between adjacent longitudinal waves.
3) The method has the idea of multi-sensor information fusion, takes a plurality of adjacent longitudinal wave time delay intervals as input variables, and can obtain higher pressure measurement precision under the condition that the measurement precision of a single time delay interval is not high.
4) By utilizing the temperature information implied by the time delay intervals between a plurality of adjacent longitudinal waves, the pressure estimation can be realized without measuring the temperature, thereby simplifying the measuring system.
5) the method takes the relative propagation distance between adjacent longitudinal waves as a measurement object, and reduces the influence on measurement caused by uneven temperature distribution on the surface of the pressure container.
Drawings
FIG. 1 shows a detection device for carrying out the method of the invention;
FIG. 2 is a schematic representation of the propagation of ultrasonic waves in a pressure vessel;
FIG. 3 is a schematic diagram of the received signal and the spacing between adjacent longitudinal waves;
FIG. 4a is a graph of test results (Δ t) for an embodiment of the present inventionLre1_L)；
FIG. 4b is a graph of test results (Δ t) for an embodiment of the present inventionLre2_1)；
FIG. 4c is a graph of test results (Δ t) for an embodiment of the present inventionLre3_2)；
FIG. 4d is a graph of test results (Δ t) for an embodiment of the present inventionLre4_3)；
FIG. 5 is a graph showing the accuracy of pressure measurement (Model _ Mul is the predicted pressure, and the upper and lower dashed lines are error bars of + 5% and-5%).
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.
In this embodiment, a pressure detection device based on a time delay interval between adjacent longitudinal waves for implementing the method of the present invention is shown in fig. 1. The device includes: cylindrical pressure vessel, manual pressure testing pump, thermostated container, pressure measurement system. The pressure detection system comprises a control and conditioning module, an ultrasonic transmitting probe and a receiving probe. The manual pressure test pump is provided with a digital pressure gauge, and the pressure in the container is regulated in a hydraulic regulation and control mode; the pressure container is arranged in a constant temperature box, and the temperature of the pipe wall is controlled by the constant temperature box; the transmitting probe and the receiving probe are arranged on the surface of the pressure vessel. The core of the control and conditioning module is a TDC ultrasonic propagation delay measuring device, a driving circuit, a receiving circuit and a TDC-GP22 time digital chip are arranged in the TDC ultrasonic propagation delay measuring device, the ultrasonic emission probe realizes mutual conversion of electric energy and acoustic energy by a piezoelectric wafer, and emits ultrasonic waves to the outer pipe wall of the pressure container under the control of the driving circuit. The ultrasonic wave is received by a receiving probe connected with a receiving circuit, and the receiving circuit can collect a plurality of longitudinal wave signals generated by the same ultrasonic wave excitation under the control of a TDC-GP22 time digital chip so as to measure the propagation delay of the ultrasonic wave in the pipe wall. According to the characteristic of single-shot multiple measurement in the TDC, high-precision measurement of the time delay interval between adjacent longitudinal waves can be realized.
In this device, ultrasonic waves are generated by the excitation probe and then incident on the outer tube wall of the pressure vessel at a critical angle, the path of which propagating in the tube wall of the pressure vessel is shown in fig. 2. The specific propagation process is as follows: when incident longitudinal wave is incident at a first critical angle, wave mode conversion occurs at the interface between the ultrasonic probe and the pressure vessel wall, and critical refracted longitudinal wave L is generated at the outer wallCRAnd refracted transverse wave, critical refracted longitudinal wave LCRThe outer pipe wall is propagated to the receiving probe to be received; the refracted transverse wave propagates in the pipe wall of the pressure container and is reflected at the inner pipe wall to generate a first inner wall reflected longitudinal wave Lre-I1st and a first reflected transverse wave Sre-1 st; the first reflected transverse wave Sre-1st continuing to propagate in the pressure vessel wall and being reflected again at the outer vessel wall, resulting in a first reflected longitudinal wave Lre-1st and a second reflected transverse wave Sre-2nd, the first reflected longitudinal wave Lre-1st propagating along the outer vessel wall to the receiving probe, the second reflected transverse wave Sre-2nd continuing to propagate in the pressure vessel wall and being reflected again at the inner vessel wall, resulting in a second inner wall reflected longitudinal wave Lre-I2nd and a third reflected transverse wave Sre-3rd, the second inner wall reflected longitudinal wave Lre-I2nd propagating along the inner vessel wall, and the third reflected transverse wave Sre-3rd continuing to propagate in the pressure vessel wall, in such a manner that the transverse wave propagating in the pressure vessel wall undergoes multiple reflections at the outer and inner vessel walls, resulting in a plurality of reflected longitudinal waves propagating along the inner vessel wall and a plurality of reflected longitudinal waves propagating along the outer vessel wall, the receiving probe fixed on the outer tube wall can receive the critical refraction longitudinal wave LCRAnd ultrasonic signals such as a first reflected longitudinal wave Lre-1st, a second reflected longitudinal wave Lre-2nd, a third reflected longitudinal wave Lre-3rd, and a fourth reflected longitudinal wave Lre-4 th.
After traveling a certain distance in the vessel wall, the ultrasonic signal enters the receiving probe, is received by the TDC through the receiving circuit and the transit time is internally calculated. The multiple timing function of the TDC is realized by shielding a time window, and the delay interval of adjacent longitudinal waves can be measured. When the time delay intervals between all the adjacent longitudinal waves cannot be obtained through one-time measurement, the time delay intervals between the adjacent longitudinal waves can be obtained through transmitting ultrasonic waves for multiple times. The pressure in the container is controlled by a manual pressure test pump, the manual pressure test pump adopts a SY-16 model, and the upper limit of the bearing pressure is 16 MPa; the temperature is adjusted by a thermostat, the GDW-50A thermostat of Shanghai and Shikuai instruments manufacturing Co., Ltd is adopted in the embodiment, the temperature control range of the equipment is 4-60 ℃, the adjustment resolution is +/-0.5 ℃, and the requirement is met. The actual reference temperature and reference pressure in the vessel were recorded using a thermocouple thermometer (TES13-15 thermocouple digital thermometer with a measurement range of-150 ℃ to 1370 ℃ and a detection resolution of + -0.1 ℃) and a standard digital pressure gauge (NY-YBS-C2 type precision digital pressure gauge, maximum range 10MPa, 0.2% FS), respectively. The testing pressure range is 0-9 MPa, and the temperature range is 24.2-32 ℃.
And the pressure in the pressure container to be detected and the receiving time of each longitudinal wave are stored in an upper computer and are used for calculating the time delay interval between adjacent longitudinal waves and fitting a pressure calculation formula, so that the pressure prediction based on the time delay interval between adjacent longitudinal waves is realized.
Based on the device, the correlation between the pressure of a certain cylindrical pressure container and the time delay interval of adjacent longitudinal waves is modeled and used for pressure prediction. The pressure detection method comprises the following specific implementation steps:
according to the method, a pressure detection device is installed according to the figure 1, and ultrasonic waves generated by an excitation probe are incident to the outer pipe wall of the pressure vessel to be detected at a first critical angle to be measured under different pressure vessel wall temperatures and vessel pressures. In this experiment, the transit time interval between adjacent longitudinal waves under the condition is measured using normal temperature (24.2 ℃) and normal pressure (0MPa) as reference temperature and reference pressure, and is used as a reference value under the reference condition. The temperature of the wall of the pressure container is controlled by a constant temperature box to be 25.0 ℃, 26.9 ℃, 28.5 ℃, 29.1 ℃, 30.2 ℃ and 32.0 ℃, and the time intervals of adjacent longitudinal wave transit time when the pressure in the pressure container is 0MPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa and 9MPa are respectively measured at each temperature point. Calculating different temperatures by combining adjacent longitudinal wave transition time intervals under the reference conditionTime delay intervals of adjacent longitudinal waves under the pressure and the degree. Under the experimental conditions, the selected time delay interval independent variables comprise: time delay interval (Δ t) between the first reflected longitudinal wave and the critical refracted longitudinal waveLre1_L) The time delay interval (delta t) between the second reflected longitudinal wave and the first reflected longitudinal waveLre2_1) The time delay interval (delta t) between the third reflected longitudinal wave and the second reflected longitudinal waveLre3_2) And the time delay interval (delta t) between the fourth reflected longitudinal wave and the third reflected longitudinal waveLre4_3)。
The obtained adjacent longitudinal wave time delay interval data delta t under different pressure and temperature conditionsLre1_L、ΔtLre2_1、ΔtLre3_2、ΔtLre4_3as shown in fig. 4.a) to 4.d), respectively. The method comprises the following steps of fitting to obtain a pressure measurement model based on adjacent longitudinal wave time delay intervals by taking adjacent longitudinal wave time delay interval data as independent variables and pressure in a pressure container to be detected as dependent variables, wherein the model adopts a multivariate linear structure:
p＝∑Ai·ΔtLrei_j+C；
Wherein: Δ tLrei_jTime delay intervals of ith and jth adjacent longitudinal waves; a. theiIs Δ tLrei_jcorresponding fitting coefficients; p is Δ tLrei_jThe pressure in the corresponding pressure vessel to be tested.
The specific pressure calculation model obtained by using least squares regression on the modeling data is as follows:
p＝-0.313·ΔtLre1_L+1.148·ΔtLre2_1+0.602·ΔtLre3_2
+0.166·ΔtLre4_3-0.110
In order to verify the prediction accuracy of the model, a pressure container with unknown pressure (namely the cylindrical pressure container for modeling) is tested, adjacent longitudinal wave time delay interval data are obtained as verification data and are substituted into the pressure calculation model obtained through modeling, and the current pressure in the pressure container is calculated. The verification result is shown in fig. 5, the pressure measurement errors are basically within the range of +/-5%, and high accuracy is achieved.
Therefore, the non-intrusive pressure detection method based on the time delay interval between adjacent longitudinal waves has the timing characteristic around the TDC and combines the pressure measurement advantages based on the wave speed change, so that the interference of the ultrasonic probe installation, the couplant, the ultrasonic excitation and receiving circuit, the temperature and other interference on the pressure detection is better solved. And the non-intrusive pressure detection device based on the time delay interval between adjacent longitudinal waves adopts the TDC as a timing unit, so that low-cost and high-precision pressure detection is realized. The measurement model established by adopting the time delay intervals between a plurality of adjacent longitudinal waves reduces the detection of temperature and simplifies the measurement system.
the above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (1)
1. A non-intrusive pressure detection method based on time delay intervals between adjacent longitudinal waves is characterized in that the method is realized by a pressure measurement system, and the pressure measurement system comprises a pressure test pump, a thermostat, an ultrasonic transmitting probe, an ultrasonic receiving probe and a TDC ultrasonic propagation time delay measurement device; the pressure test pump is connected with the inner cavity of the pressure container and is used for adjusting the pressure in the container; the pressure container is arranged in a constant temperature box, and the temperature of the pipe wall is controlled by the constant temperature box; the transmitting probe and the receiving probe are arranged on the outer surface of the pressure container, and a TDC-GP22 time digital chip is arranged in the TDC ultrasonic propagation delay measuring device and is used for receiving a plurality of longitudinal waves generated by the same ultrasonic excitation through the receiving probe;
The non-intrusive pressure detection method comprises the following steps:
1) Selecting a time delay interval between adjacent longitudinal waves as a measurement parameter, and arranging a pair of ultrasonic excitation and receiving probes on the outer surface of the pressure vessel; when the excitation wave excited by the excitation probe is incident from the outer surface of the pressure container at a first critical angle, the ultrasonic wave is reflected, refracted and subjected to wave mode conversion on the surface of the container for multiple times, and the receiving probe can sequentially receive the critical refracted longitudinal wave L propagating along the wall of the outer pipeCRand a plurality of reflected longitudinal wave signals; according to the sono-elastic effect, a variation of the pressure inside the container causes a critical refracted longitudinal wave LCRAnd the wave velocity change of the reflected longitudinal wave, which shows that the propagation delay of each longitudinal wave changes, so that the delay interval between adjacent longitudinal waves also changes;
2) Detecting time delay intervals between adjacent longitudinal waves under different container pressures, and constructing a pressure measurement model based on the time delay intervals between the adjacent longitudinal waves to obtain a relation between the pressure in the pressure container and the time delay intervals between the adjacent longitudinal waves;
3) Calculating the pressure in the pressure container to be detected according to the pressure measurement model constructed in the step 2) and the time delay interval between adjacent longitudinal waves of the pressure container to be detected, thereby realizing the non-intrusive pressure detection of the pressure container;
The method for measuring the time delay interval between adjacent longitudinal waves comprises the following steps: simultaneously measuring the transition time of critical refraction longitudinal waves and a plurality of reflection longitudinal waves generated under the same excitation pulse by adopting a programmable shielding window technology and a TDC digital time measurement chip, and then calculating to obtain the time delay interval between the adjacent longitudinal waves;
The time delay interval between the adjacent longitudinal waves comprises the time delay interval between the critical refraction longitudinal wave and the first reflection longitudinal wave and the time delay interval between the adjacent reflection longitudinal waves;
the expression of the pressure measurement model is as follows:
p＝∑Ai·ΔtLrei_j+C；
Wherein: Δ tLrei_jtime delay intervals of ith and jth adjacent longitudinal waves; a. theiIs Δ tLrei_jCorresponding fitting coefficients; p is Δ tLrei_jthe pressure in the corresponding pressure vessel to be tested.
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