An online monitoring method and system for high viscosity gas-liquid flow regimes

Abstract

The application discloses an online monitoring method and system for a high-viscosity gas-liquid material flow state, and the monitoring system comprises an acoustic emission probe, a preamplifier, a main amplifier, an acquisition card and a computer; stress change generated by gas-liquid flow and wall surface interaction is monitored, and is converted into a voltage signal; after relevant processing, the motion characteristics of the high-viscosity gas-liquid material are obtained; and the gas-liquid motion characteristics such as flow speed in the pipe, flow mode and gas-liquid composition are further obtained. The acoustic emission monitoring is a non-invasive detection method, has higher sensitivity and accuracy, does not need to install additional sensors on the pipe, reduces cost and improves monitoring reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-viscosity gas-liquid material flow state, and in particular to a detection method and system for online monitoring of the high-viscosity gas-liquid material flow state. BACKGROUND

[0002] In industrial production processes, the transportation of high-viscosity gas-liquid materials (liquid phase material viscosity is 1 x 10 3 ~ 1 x 10 6 mPa·s) is one of the common operations. Due to the high viscosity of such materials, there are often problems such as large flow resistance, easy blockage, and low transportation efficiency during pipeline transportation. Traditional monitoring methods, such as pressure sensors and flow meters, can provide information on the flow state of the material to some extent, but they usually have limited sensitivity to the viscosity and flow characteristics of the material, and in some cases it is difficult to accurately reflect the actual flow state of the material.

[0003] Monitoring the flow state of high-viscosity gas-liquid materials in pipelines is a technical challenge. Due to the poor light transmittance and strong adhesion of high-viscosity liquids, the flow characteristics of high-viscosity gas-liquid materials are complex and affected by many factors, including the viscosity, temperature of the material, and the material and shape of the pipeline. In addition, traditional visual monitoring techniques often require the installation of additional sensors on the pipeline, which not only increases the cost but also may affect the integrity of the pipeline and the flow of the material, and therefore cannot fully meet the needs.

[0004] Existing Acoustic Emission (AE) technology has been applied to various industrial monitoring fields, including structural health monitoring and fault diagnosis. Acoustic emission signals are elastic waves caused by changes in the microstructure of materials, which can reflect the flow of materials in the pipeline in real time. However, the application of acoustic emission technology to the flow state monitoring of high-viscosity gas-liquid materials requires solving technical problems such as signal collection and analysis.

[0005] In summary, the detection method and system for high-viscosity gas-liquid material flow state are very important for the structural design and operation control of the pipeline. SUMMARY

[0006] The purpose of the present application is to propose a detection method and system for high-viscosity gas-liquid material flow state. By analyzing the characteristics of acoustic emission signals, the flow state of the material can be accurately identified, including flow speed, flow pattern, gas-liquid composition, and possible blockage.

[0007] The present application is achieved by the following technical solutions:

[0008] In a first aspect, the present application provides an online monitoring method for high-viscosity gas-liquid material flow state, comprising at least the following steps:

[0009] (1) providing a first pipe with at least one acoustic emission sensor installed;

[0010] (2) installing the first pipe at the end or middle of a high-viscosity gas-liquid material conveying pipeline, so that the high-viscosity gas-liquid material can pass through the first pipe;

[0011] (3) continuously monitoring the acoustic signal, and performing at least 3-scale wavelet decomposition on the acoustic signal since the detail signal cannot be obtained by performing wavelet decomposition below 3 scales to obtain the acoustic signal energy in the characteristic frequency range of the acoustic signal;

[0012] (4) for a certain high-viscosity gas-liquid material to be monitored, first pass a plurality of groups of the high-viscosity gas-liquid material with known gas-liquid two-phase flow but different flow rates into the first pipe for continuous acoustic signal monitoring, and use the obtained acoustic signal energy to fit the undetermined coefficients in the following formula: E = x × VG y × VL z

[0013] wherein E is the acoustic signal energy of the acoustic signal in the characteristic frequency range, the unit is square of measured voltage volt V, VG is the gas phase flow rate of the gas-liquid material, m 3 / h, VL is the liquid phase flow rate of the gas-liquid material, m 3 / h, and the two-phase flow rate can be obtained by a flow meter

[0014] wherein x, y, z are the undetermined coefficients in the formula, x is 1 × 10 -7 ~ 1 × 10 -1 , y is 3-6, and c is 0.6-2;

[0015] (5) for the high-viscosity gas-liquid material to be monitored, use the first pipe with the acoustic emission sensor to obtain the acoustic signal energy in the characteristic frequency range of the acoustic signal, and calculate the two-phase flow rate of the high-viscosity gas-liquid material according to the formula fitted in step (4) to obtain the flow state of the high-viscosity gas-liquid material.

[0016] The time-domain waveform describes the change of the acoustic emission signal amplitude with time, and the signal intensity can be obtained by , wherein x n is the original acoustic emission signal sample value. The time-domain feature is directly extracted from the time sequence of the acoustic emission signal, and reflects the basic statistical properties and morphological features of the signal. The time-frequency domain analysis can provide the frequency information of the signal with time, and is suitable for analyzing non-stationary or rapidly changing signals.

[0017] Wavelet decomposition is an important time-frequency domain analysis method, which is realized by convolving the signal with a wavelet function. Specifically, by adjusting the scaling (controlling the frequency width) and translation (determining the time position) of the wavelet function, wavelet decomposition can analyze and obtain the local characteristics of the signal at multiple scales. The wavelet decomposition formula is as follows:

[0018]

[0019]

[0020] wherein A j (n) is the approximation coefficient of the jth scale; D j (n) is the detail coefficient of the jth scale; h(n) is the low-pass filter coefficient; g(n) is the high-pass filter coefficient; and k is the sampling index.

[0021] Preferably, the wavelet decomposition method selected in step (3) is the Daubechies wavelet basis function. Since the maximum acquisition frequency of the acoustic emission signal is 1000 kHz, according to the Nyquist sampling theory, the upper limit of the signal frequency is 500 kHz, and more preferably, wavelet decomposition is performed at more than 3 scales, and more preferably at 4-9 scales.

[0022] In a second aspect, the present application provides an online monitoring system for the flow state of high-viscosity gas-liquid material, which comprises at least one acoustic emission probe, a preamplifier, a main amplifier, an acquisition card and a computer. The acoustic emission probe is a piezoelectric sensor attached to the wall of a vertical pipeline, which is used to monitor the stress changes generated by the interaction of gas-liquid flow with the wall and convert them into voltage signals. After being amplified by the preamplifier and the main amplifier, the signals are transmitted to the acquisition card, which is then processed and analyzed by the computer to obtain parameters representing the flow state of the high-viscosity gas-liquid material in the pipeline.

[0023] Preferably, the amplification factor of the preamplifier is 60 dB, and the digital resolution of the acquisition card is 16 bits.

[0024] The present application uses acoustic emission signal monitoring technology to monitor the flow state of high-viscosity gas-liquid material in a pipeline. By analyzing the characteristics of the acoustic emission signal, this method can accurately identify the flow state of the material, including flow velocity, flow pattern, gas-liquid composition and possible blockage. Compared with traditional methods, the present application has higher sensitivity and accuracy, and does not require the installation of additional sensors on the pipeline, reducing costs and improving the reliability of monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a schematic diagram of the monitoring system structure of the present application.

[0026] Figure 2The wavelet decomposition and energy distribution of the acoustic emission signal from the annular flow are shown, where (a) is the wavelet decomposition of the acoustic emission signal from the annular flow; and (b) is the energy distribution of the wavelet decomposition of the acoustic emission signal from the annular flow (v). G =30m 3 / h,v L =0.5m 3 / h).

[0027] Figure 3 The wavelet decomposition energy distribution of acoustic emission signals under different gas / liquid flow rates is shown, where (a) L4; (b) L4+L5.

[0028] Figure 4 This is a comparison of the prediction performance of scale energy (L4+L5). Detailed Implementation

[0029] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0030] like Figure 1 As shown, the experimental system equipped with the monitoring system of the present invention includes a first pipe fitting 1, a plunger pump 2, an acoustic emission probe 3, a preamplifier 4, a main amplifier 5, a data acquisition card 6, and a computer 7. The acoustic emission probe 3, preamplifier 4, main amplifier 5, data acquisition card 6, and computer 7 constitute the monitoring system for the flow state of high-viscosity gas-liquid materials of the present invention. The plunger pump is located at the inlet section of the first pipe fitting 1 to control the flow rate of liquid delivered into the pipe. The acoustic emission probe 3 is located on the outer wall of the first pipe fitting 1. The acoustic emission probe 3 is connected to the preamplifier 4 to convert the acoustic signal into an electrical signal and transmit it to the preamplifier 4. The preamplifier 4 is connected to the main amplifier 5 to transmit the amplified signal to the main amplifier 5. The main amplifier 5 is connected to the data acquisition card 6 to transmit the further amplified signal to the data acquisition card. The data acquisition card 6 is connected to the computer 7 to analyze the acquired signals and obtain parameters characterizing the flow state of high-viscosity gas-liquid materials in the pipeline.

[0031] The detection of the flow state of high-viscosity gas-liquid materials in this embodiment is as follows:

[0032] The high-viscosity gas-liquid material generating system is composed of a gas / liquid supply system and a reactor system. The gas / liquid supply system delivers air / water to the reactor system, and the reactor system is composed of a feeding port, a reciprocating pump, a reactor and a discharge valve. The discharge valve is driven by a servo motor and the opening degree of the valve is adjusted by a computer. In the experiment, when the material enters the reactor system through the feeding port, the material is pressurized by the reciprocating pump and delivered to the reactor, and the material generated after the reaction is discharged into the main pipeline through the discharge valve. In each reaction process, the material in the main pipeline is high-viscosity gas-liquid material. In order to facilitate the subsequent gas-liquid separation of the high-viscosity gas-liquid material, the monitoring system provided by the application can collect the acoustic signals of the flow of the high-viscosity gas-liquid material, and the flow state can be obtained by comparison.

[0033] In the experiment, the upper limit of the signal frequency is 500 kHz, and 8 scale decompositions are carried out. The specific frequency range of each scale is: 250-500 kHz, 125-250 kHz, 62.5-125 kHz, 31.25-62.5 kHz, 15.625-31.25 kHz, 7.8125-15.625 kHz, 3.90625-7.8125 kHz, and 1.953125-3.90625 kHz.

[0034] Figures 2 to 4 The original acoustic signals monitored by the high-viscosity gas-liquid material flow state monitoring system and the characteristic parameters related to the motion of the gas-liquid after processing.

[0035] Figure 2 It is the energy distribution of the ring flow acoustic emission signal after wavelet decomposition. The 4th scale energy (31.25-62.5 kHz) and the 5th scale energy (15.625-31.25 kHz) of the wavelet decomposition analysis are characteristic scales in the ring flow of high-viscosity fluid, which can better reflect the flow characteristics of the ring flow. Therefore, the energy distribution of these two scales under different operating conditions is further explored. Figure 3 It is the wavelet decomposition of the acoustic emission signal of the 4th and 5th scales under different gas-liquid flow rates. (a) is the 4th scale, and (b) is the 4th and 5th scales. The results show that the 4th and 5th scales can better reflect the flow state. Under the same gas flow rate, whether the energy of the 4th scale or the sum of the energies of the 4th and 5th scales shows a good linear relationship with the liquid volume flow rate. Further considering that the 4th and 5th scales are significantly affected by the gas and liquid volume flow rates, which is mainly caused by the vibration and shear of the gas-liquid interface. Through least square fitting of the model parameters, the following empirical correlation is obtained The prediction effect of the correlation is shown in Figure 4 The experimental values conform to the above empirical correlation.

[0036] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An on-line monitoring method for high viscous gas-liquid flow regime, characterized in that, The method comprises at least the following steps: (1) providing a first pipe with at least one acoustic emission sensor; (2) installing the first pipe at the end or middle of a high-viscosity gas-liquid material conveying pipeline, so that the high-viscosity gas-liquid material can pass through the first pipe; (3) continuously monitoring acoustic signals, wavelet-decomposing the acoustic signals, and obtaining acoustic signal energy in a characteristic frequency range of the acoustic signals; (4) for a certain high-viscosity gas-liquid material to be monitored, first pass a plurality of groups of the high-viscosity gas-liquid material with known gas-liquid two-phase flow into the first pipe for continuous acoustic signal monitoring, and use the obtained acoustic signal energy to fit the undetermined coefficients in the following formula: ； wherein E is the sound signal energy of the sound signal in the characteristic frequency range, measured in volt V VG is the gas phase flow rate in the gas-liquid material, m 3 VL is the liquid phase flow rate in the gas-liquid material, m 3 x, y, z is the undetermined coefficient in the formula, x is 1×10 -7 ~ 1×10 -1 y is 3 ~ 6, z is 0.6 ~ 2;​​​​ (5) for the high-viscosity gas-liquid material to be monitored, use the first pipe with the acoustic emission sensor to obtain acoustic signal energy in a characteristic frequency range of the acoustic signals, and calculate the two-phase flow of the high-viscosity gas-liquid material according to the formula fitted in step (4) to obtain the flow state of the high-viscosity gas-liquid material.

2. The method for online monitoring of high viscous gas-liquid flow regime as claimed in claim 1 wherein, The high-viscosity gas-liquid material contains at least one polymer, and the polymer is low-density polyethylene or a copolymer of ethylene and at least two monomers of vinyl acetate, acrylic acid and its ester, and an olefin with more than 3 carbon atoms.

3. The method for online monitoring of high viscous gas-liquid flow regime as claimed in claim 1 wherein, The liquid phase material viscosity of the high-viscosity gas-liquid material is 1 x 10 3 ~ 1 x 10 6 MPa•s, the temperature is 20 ~ 400 ℃, and the pressure is 0.1 ~ 100 MPa.

4. The method for online monitoring of high viscous gas-liquid flow regime as claimed in claim 1 wherein, In step (3), the acoustic signal acquisition frequency is 10-1000 kHz, and the minimum value of the characteristic frequency range is >1 kHz and the maximum value is <80 kHz.

5. The method for online monitoring of high viscous gas-liquid flow regime as claimed in claim 1 wherein, In step (3), the wavelet decomposition method selected is a Daubechies wavelet basis function, and wavelet decomposition is performed at least 3 scales.

6. An on-line monitoring system for use in carrying out the method of claim 1 for high viscous gas-liquid flow regime, characterized by, The system comprises at least one acoustic emission probe, a preamplifier, a main amplifier, an acquisition card and a computer. The acoustic emission probe is a piezoelectric sensor attached to the first pipe, which is used to monitor the stress changes caused by the interaction of gas-liquid flow and wall, and convert them into voltage signals. After amplification by the preamplifier and the main amplifier, the signals are transmitted to the acquisition card, and then processed and analyzed by the computer to obtain parameters representing the flow state of the high-viscosity gas-liquid material in the pipeline.

7. The online monitoring system according to claim 6, wherein the first pipe is one of a straight pipe, an elbow pipe, an elbow, a reducing pipe, a flange, and a lens pad.

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