CN114518190A - Non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology - Google Patents

Abstract

The invention discloses a non-intrusive pipeline liquid pressure measurement method based on an ultrasonic longitudinal wave reflection technology; the method utilizes the difference of sound velocity of liquid in the pipe wall under different pressure and temperature to indirectly measure the pressure value of the liquid in the pipeline; the measurement error caused by ultrasonic transducer installation, couplant and circuit delay is eliminated by using the longitudinal wave reflection time of the ultrasonic waves in the pipe wall, the accurate measurement of the transmission time of the liquid in the pipeline is realized, and a corresponding mathematical model of the transmission time and the temperature of the liquid in the pipeline and the pressure value of the liquid in the pipeline is established. The measuring device adopts a circuit design structure with an MS1030 time digital conversion chip as a main part and high-speed ADC data acquisition as an auxiliary part to measure the ultrasonic transmission time, takes a microprocessor as a core, and converts the time and the temperature of ultrasonic transmission and signal receiving into pressure values through corresponding mathematical calculation and displays the pressure values, thereby effectively solving the problem of non-intrusive pressure measurement required by special occasions.

Description

Non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology

technical field

The invention belongs to the technical field of pressure measurement and calibration, in particular to a non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology.

Background technique

The pressure vessel type refers to a closed device that contains gas or liquid and carries a certain pressure. With economic development and social progress, pressure vessels have been deeply integrated into people's production and life, such as various process and reaction equipment in the metallurgical and pharmaceutical industries; boilers and gas liquefaction facilities in the power and energy fields; Reactor force shell; pressure cooker, liquefied gas tank, etc. in daily life. Generally speaking, pressure vessels are installed in harsh environments such as high pressure and high temperature, and the media they carry are mostly flammable, explosive and highly corrosive substances. Once leakage, damage or failure occurs due to various reasons during operation, it will cause casualties and economic losses, and directly threaten the safety of life and property of the general public. Therefore, pressure detection has special value and significance in production activities. In practical applications, it is necessary to monitor and dynamically control the internal pressure of pressure vessels in real time, which can not only eliminate potential safety hazards in time, but also help improve the production efficiency of enterprises.

The traditional pressure detection methods are interventional, and the characteristic load cell must be in full contact with the measured medium. Generally, a hole is made on the measured object, and then the measured pressure is led to the sensitive element of the pressure detection instrument through the pipeline. Interventional pressure measurement is widely used because of its reliability, high precision and low price, but it has the following disadvantages: 1) Stress concentration is easy to occur at the opening, and the peak stress can reach 3 to 6 times that of the film stress, which reduces the service life of the container . 2) It is inconvenient to add additional test points. 3) Most pressure vessels do not allow openings. For the above drawbacks, non-intrusive stress detection methods have been improved to a certain extent.

Non-intrusive pressure measurement can be divided into strain pressure measurement method, optical fiber pressure measurement method, capacitive pressure measurement method and ultrasonic pressure measurement method according to different working principles. The principle of the strain gauge pressure measurement method is to directly paste the strain gauge on the tube wall of the pressure vessel, and its resistivity will change correspondingly with the mechanical deformation caused by the change of the internal pressure of the vessel, so as to realize the pressure measurement. The method has good state characteristics, small mechanical hysteresis, and can measure small strains, but the anti-interference ability is crossed, there is plastic deformation and zero drift, serious nonlinearity, and low measurement accuracy. The principle of the optical fiber pressure measurement method is that under the action of pressure change, the stress applied to the optical fiber perpendicular to the axis direction will cause the optical fiber to microbend and deform, thereby changing the amplitude of light. Variety. This method is not subject to electromagnetic interference, fast response, and heat resistance. However, due to its high cost and high technical requirements for installation, its application range is very limited. The principle of the capacitive pressure measurement method is that when the pressure changes, the dielectric constant will also change accordingly, and then the pressure value can be obtained by substituting it into the relationship model between the two. The dielectric constant is easily affected by the medium composition and temperature, and is easily affected by the electromagnetic environment, and is generally used for objects with small diameters. The ultrasonic pressure detection based on amplitude attenuation is easily affected by the properties and temperature of the medium due to the propagation of ultrasonic waves in the medium. In addition, the installation method of the transducer and the couplant will introduce large interference. When the container wall is thin, the incident signal will overlap with the reflected signal, making it impossible to distinguish the real received signal. Ultrasonic pressure detection based on wave velocity changes overcomes the influence of the medium, but factors such as transducer installation, temperature, and couplant still have a certain impact on the pressure detection accuracy.

The ultrasonic pressure measurement method has been highly valued by scholars at home and abroad. Different waveforms (critical refracted longitudinal wave, reflected longitudinal wave, Rayleigh wave, etc.) are used for pressure detection and stress analysis, and fruitful scientific research results have also been achieved, as follows:

CN201810113906.2 A non-intrusive pressure detection method based on the time delay interval between adjacent longitudinal waves;

Wu Yingsi. Research on non-intrusive pipeline pressure detection mechanism based on ultrasonic guided wave acoustoelastic effect [D]. Inner Mongolia Agricultural University, 2019.

The above methods and explorations use different types of ultrasonic waves to achieve non-invasive pressure detection and improve the effect of temperature. But there are still some shortcomings that need to be improved. First of all, the acoustoelastic effect of the pressure vessel is very weak and easily disturbed, the change 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, the temperature, the properties of the ultrasonic transducer, the installation of the transducer, the ultrasonic excitation and receiving circuit, and the couplant will all have a great influence on the transit time. How to reduce or eliminate the influence of these factors has become an urgent problem to be solved. . Although the measurement method using two-wave reference can reduce the influence of temperature, it cannot completely eliminate it, and requires multiple ultrasonic transducers, and the measurement device is complicated. The modeling method based on multi-wave fusion integrates the information of each waveform and greatly improves the measurement accuracy. and so on will have a greater impact on the ultrasonic transit time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology, propose a method for accurately measuring the ultrasonic longitudinal wave propagation velocity of pipeline liquid, and indirectly measure the liquid pressure in metal pipelines based on the principle that the speed of sound will change with the liquid pressure. Pressure value.

The technical solution adopted in the present invention is that, based on the ultrasonic longitudinal wave reflection technology, the non-intrusive pipeline liquid pressure measurement method realizes the measurement process through a pressure measurement device, and the device includes an automatic pressure calibrator, a pair of ultrasonic transducers, Temperature sensor, high and low temperature box and ultrasonic time measuring device. High and low temperature box and automatic pressure calibrator are respectively used to control the temperature and pressure value of pipeline liquid when the ultrasonic time measuring device is calibrated. The ultrasonic transducer and temperature sensor are installed in the pipeline. Surface, ultrasonic time measurement is used to excite ultrasonic waves and receive and record the time value of multiple reflected longitudinal waves, and inversely calculate the pressure value.

The feature of the present invention also lies in:

Among them, the non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology is specifically implemented according to the following steps:

Step 1: Arrange a pair of ultrasonic transmitting and receiving transducers and temperature sensors on the outer surface of the pressure vessel. When the ultrasonic transmitting transducer excites an ultrasonic wave, the ultrasonic longitudinal wave transmits and reflects multiple times inside the pipeline. By measuring the reflections respectively The reflection propagation time of the wave in the pipe wall and the total reflection propagation time of the pipe wall and the liquid are calculated, the propagation time of the reflected wave in the pipe liquid is calculated, and the temperature value is measured at the same time;

Step 2, under the same pipeline, liquid medium, and at the same temperature, record each time node of transmission and reflection of ultrasonic transmission in the pipeline under different pressures, and save the pressure value and the temperature value together;

Step 3, under the same pipeline, liquid medium, and under the same pressure, record each time node of transmission and reflection of ultrasonic transmission in the pipeline at different temperatures, and save the pressure value and the temperature value together;

Step 4, according to the data obtained in steps 2 and 3, establish a corresponding pressure measurement model;

Step 5, according to the pressure measurement model established in step 4 and the transmission time and temperature of the liquid in the pressure pipeline to be measured, calculate the pressure value in the pipeline to be measured;

The pressure prediction model in step 4 is: calculated by linear interpolation at temperature T, each pressure corresponds to calibration time point t _j :

t _j =t _i +(TT _i )*((t _i+1 -t _i )/(T _i+1 -T _i )) (1)

From the time point t _j , the pressure value is calculated using linear interpolation:

P=P _j +(tt _j )*((P _j+1 -P _j )/(t _j+1 -t _j )) (2);

Wherein, the final ultrasonic propagation time measured in step 1 is the back and forth reflection time of the inner wall of the pipeline in the liquid in the pipeline;

The temperature sensor is close to the surface of the pipeline, and the temperature sensor is also provided with a thermal insulation layer.

The beneficial effects of the present invention are:

The non-intrusive pipeline liquid pressure measurement method based on the ultrasonic longitudinal wave reflection technology of the present invention adopts the TOFD ultrasonic transducer, has the characteristics of high damping, high resolution, narrow frequency band and high receiving sensitivity, and improves the accuracy and reliability of the measurement. At the same time, it is equipped with a curved wedge with the same outer diameter as the pipe, which improves the transmittance of ultrasonic waves and facilitates installation. Solve the measurement error caused by circuit delay, inconsistent start-up time of ultrasonic transmission, transducer installation, ultrasonic couplant, and tube wall transmission time; directly measure the propagation speed of ultrasonic waves in the liquid, rather than the time change of transmission in the tube wall , effectively improve the measurement resolution and accuracy of pressure measurement; use the temperature sensor with external heat insulation treatment to reduce the influence of ambient temperature on the measurement and avoid the opening of the pipeline, so that the temperature of the liquid measured outside the tube can approach the real liquid temperature to the greatest extent. temperature, effectively reducing the measurement error.

Description of drawings

Fig. 1 is the propagation path of ultrasonic wave in pipeline liquid in the non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology of the present invention;

Fig. 2 is the system structure diagram of the pressure measurement device in the non-intrusive pipeline liquid pressure measurement method based on the ultrasonic longitudinal wave reflection technology of the present invention;

FIG. 3 is a diagram showing the installation position of the equipment in the non-intrusive pipeline liquid pressure measurement method based on the ultrasonic longitudinal wave reflection technology of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention designs a set of ultrasonic pressure detection device with temperature measurement compensation based on domestic MS1030 digital time conversion, and proposes a method for accurately measuring the propagation velocity of ultrasonic longitudinal waves in pipeline liquid. Pressure value of liquid; this method uses ultrasonic longitudinal wave secondary reflection combined with MS1030 time digital chip time and temperature measurement, which can effectively eliminate transducer fixation, inconsistent start-up time of ultrasonic transducer, couplant, electronic circuit and other common modes The influence of factors on the measurement of the propagation time of ultrasonic waves in the pipeline liquid; since the temperature has a great influence on the supersonic speed of the liquid, this design uses PT1000 AA-grade platinum resistance on the outside of the pipe wall to measure the liquid temperature in the pipeline.

The propagation path of ultrasound in the pipeline is shown in Figure 1; the transmitting ultrasonic transducer T emits incident wave A1 perpendicular to the pipe wall, and when passing through the junction of the pipeline and the liquid, it will generate transmitted wave A2 and reflected wave A', transmitted wave A2 The transmitted wave A3 and the reflected wave B1 are generated at the junction of the liquid and the pipe wall; the transmitted wave A3 is transmitted through the pipe wall to the receiving transducer R, the time at this time is recorded as t0, and the reflected wave is generated at the junction of the pipe wall and the outside air B2 and B2 generate B3 at the junction of the pipe wall and the liquid, and the time when B3 transmits to the transducer through the pipe wall is recorded as t1; the reflected wave B1 passes through the liquid and the pipe wall to generate a reflected wave B5, and B5 is transmitted to the pipe through the liquid medium The transmitted wave B6 is generated at the junction of the wall and the liquid, and the time record of B6 passing through the pipe wall to the receiving transducer R is t2; the transmission time of the reflected waves B2 and B3 is t1-t2, and the transmission time of the reflected waves B1, B5, B6 is t3-t1, the accurate transmission time of ultrasonic waves in the liquid is Δt=(t3-t1)-(t1-t2)/2;

The propagation speed of ultrasound is not only related to the pressure of the liquid, but also the temperature of the liquid has a great influence on the propagation speed of the ultrasound. Therefore, this system uses AA-grade PT1000 platinum resistance to test the temperature of the liquid. In order to make the test temperature better close to the real temperature of the liquid, The outside of the temperature probe is insulated except for the contact surface with the pipeline. Taking ultrasonic transmission time and liquid measurement temperature as input parameters and pressure as output, the pressure calculation model is established by bilinear interpolation method:

In the formula, f(x, y) is the final pressure value divided by calculation, x is the ultrasonic transmission time, y is the measured liquid temperature value, XF and YF are the ultrasonic transmission time and liquid temperature corresponding to the calibration point, respectively, f (XF, YF) is the pressure value corresponding to the calibration point;

The non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology specifically includes the following steps:

Step 1: Arrange a pair of ultrasonic transmitting and receiving transducers and temperature sensors on the outer surface of the pressure vessel. When the transmitting transducer excites ultrasonic waves, the ultrasonic longitudinal waves are transmitted and reflected multiple times inside the pipeline, and the required time nodes are recorded. . Each transmission and reflection time node in the pipeline will change with temperature and pressure;

Step 2, under the same pipeline, liquid medium, and at the same temperature, record each time node of transmission and reflection of ultrasonic transmission in the pipeline under different pressures, and save the pressure value and the temperature value together;

Step 3, under the same pipeline, liquid medium, and under the same pressure, record each time node of transmission and reflection of ultrasonic transmission in the pipeline at different temperatures, and save the pressure value and the temperature value together;

Step 4: According to the data obtained in Step 2 and Step 3, under the condition that the pipeline and the liquid remain unchanged, the calculation model of the pressure can be constructed by the bilinear interpolation method, and the calculation model of the pressure can be calculated by the ultrasonic propagation speed and the temperature value of the liquid in the pipeline. The liquid pressure value in the outlet pipe;

Step 5: Repeat steps 2 and 3 to carry out a variety of pipelines and liquid media, and save the data; select the program through the program during measurement, and then measure the corresponding pipeline liquid pressure value.

Figure 2 is the specific structure of the pressure detection device of the present invention, including human-computer interaction, microprocessor and DSP digital signal processing, data acquisition, ultrasonic transmitting and receiving circuits, MS1030 time data conversion, temperature acquisition and ultrasonic transmitting and receiving transducers constitute. The human-computer interaction system includes a 5-inch lcd touch screen, and communicates with the host computer through RS232 to control the operation of the system. The system functions include pressure measurement, pressure reset and pressure calibration. The microprocessor controls the ultrasonic transmitting circuit to emit 110V high-voltage pulses through PWM waves to excite the transmitting transducer to generate ultrasonic waves. The receiving ultrasonic transducer converts the received ultrasonic waves into electrical signals, which are filtered and amplified by the receiving circuit, and then sent to the MS1030 digital time conversion circuit and data acquisition circuit. The data acquisition circuit quantizes the received signal, performs FIR filtering processing through DSP, and uploads the collected and processed temperature data to the microprocessor; the microprocessor uses the time signal converted by MS1030 to process the amplitude of the DSP- The time data is corrected to obtain reliable ultrasonic propagation time and liquid temperature in the pipeline liquid. Through the bilinear difference method, the real-time pressure value of the liquid in the current pipeline can be calculated using the calibration data stored in the system. The system uses a 2.5MHz TOFD ultrasonic transducer, and each data is collected 50 times at a frequency of 100Hz. The abnormal values in each measurement are removed by FIR low-pass filter and median average filtering method, which can make the system The time measurement accuracy is within 0.1ns.

The steps to calibrate the device are as follows:

The calibration system is shown in Figure 3. The model of the high and low temperature test chamber is FBS400L, the temperature control accuracy is ±0.5°C, and the display accuracy is ±0.1°C. The automatic pressure pump is a portable automatic pressure calibration bench of CWY-1060, with a range of 6MPa. , the pressure control accuracy is 0.05, all of which fully meet the required requirements; the set temperature is controlled by a constant temperature box, and the temperature is measured at the temperature points of 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C, respectively. Transmission time of ultrasound in pipeline liquid under pressure of 0MPa, 0.5MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa, 5.5MPa, 6MPa. Each time the temperature is switched, it is necessary to wait for half an hour after the temperature reaches the set point to ensure that the temperature in the liquid in the pipeline is consistent with the temperature in the incubator, and the transmission time data, pressure data, temperature data of ultrasonic transmission in the liquid will be measured in the system The measurement data is saved;

Taking the above saved data as calibration data, the real-time ultrasonic transmission time Δt in the pipeline liquid and the data T of the temperature sensor are input data, and the real-time pressure value is calculated through the bilinear insertion algorithm model;

First, through the calibration number, linear interpolation is used to calculate the calibration time point tj for each pressure at the temperature T:

t _j =t _i +(TT _i )*((t _i+1 -t _i )/(T _i+1 -T _i )) (1)

Through the calculated calibration time point t _j , the pressure value is calculated again using the linear interpolation method:

P=P _i +(t _i )*((P _i+1 -P _i )/(t _i+1 -t _i )) (2)

Finally, in order to verify the accuracy of the model, the test pipeline is placed at ambient temperature, the automatic pressure calibration table is pressurized to different pressure values, and the values displayed on the ultrasonic pressure gauge are compared. The pressure measurement error is basically Within the range of 2% value, a high measurement accuracy is achieved.

Claims (5)

1. The non-intrusive pipeline liquid pressure measurement method based on the ultrasonic longitudinal wave reflection technology is characterized in that a measurement process is achieved through a pressure measurement device, the device comprises a full-automatic pressure calibration instrument, a pair of ultrasonic transducers, a temperature sensor, a high-low temperature box and an ultrasonic time measurement device, the high-low temperature box and the full-automatic pressure calibration instrument are respectively used for the ultrasonic time measurement device to calibrate and control the temperature and the pressure value of pipeline liquid, the ultrasonic transducers and the temperature sensor are installed on the surface of a pipeline, ultrasonic time measurement is used for exciting ultrasonic waves, receiving and recording the time value of multiple reflection longitudinal waves, and the pressure value is calculated in a reverse mode.

2. The method for measuring the liquid pressure of the non-intrusive pipeline based on the ultrasonic longitudinal wave reflection technology is characterized by comprising the following steps:

step 1, arranging a pair of ultrasonic transmitting and receiving transducers and a temperature sensor on the outer surface of a pressure container, when the ultrasonic transmitting transducer excites a primary ultrasonic wave, transmitting and reflecting ultrasonic longitudinal waves for multiple times in a pipeline, calculating the propagation time of the reflected waves in the pipeline liquid by respectively measuring the reflection propagation time of the reflected waves in the pipeline wall and the total reflection propagation time of the pipeline wall and the liquid, and measuring a temperature value;

step 2, recording each time node of transmission and reflection of the ultrasound in the pipeline under different pressures under the same pipeline, liquid medium and temperature, and storing the pressure value and the temperature value together;

step 3, recording all time nodes of transmission and reflection of the ultrasound in the pipeline at different temperatures under the same pipeline, liquid medium and pressure, and storing a pressure value and a temperature value together;

step 4, establishing a corresponding pressure measurement model according to the data acquired in the step 2 and the step 3;

and 5, calculating the pressure value in the pipeline to be tested according to the pressure measurement model established in the step 4 and the transmission time and temperature of the liquid in the pipeline to be tested.

3. The method for measuring the liquid pressure in the non-intrusive pipeline based on the ultrasonic longitudinal wave reflection technology as recited in claim 2, wherein the pressure prediction model in the step 4 is as follows: calculating the calibration time T corresponding to each pressure at the temperature T by linear interpolation_j：

t_j＝t_i+(T-T_i)*((t_i+1-t_i)/(T_i+1-T_i)) (1)

Passing through the time point t_jCalculating the pressure value by using a linear interpolation method:

P＝P_j+(t-t_j)*((P_j+1-P_j)/(t_j+1-t_j)) (2)。

4. the method for measuring the liquid pressure in the non-intrusive pipeline based on the ultrasonic longitudinal wave reflection technology as recited in claim 2, wherein the final ultrasonic propagation time measured in the step 1 is the time of the back and forth reflection of the inner wall of the pipeline in the liquid in the pipeline.

5. The non-intrusive pipeline liquid pressure measurement method based on ultrasonic longitudinal wave reflection technology as recited in claim 1, wherein the temperature sensor is tightly attached to the surface of the pipeline, and a heat-insulating layer is further arranged outside the temperature sensor.

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