Online monitoring method and system for flow state of high-viscosity gas-liquid material

Abstract

The invention discloses an on-line monitoring method and system for the flow state of a high-viscosity gas-liquid material, and the method comprises the steps: monitoring the stress change generated by the action of gas-liquid flow and a wall surface through a monitoring system comprising an acoustic emission probe, a pre-amplifier, a main amplifier, an acquisition card and a computer, converting the stress change into a voltage signal, and transmitting the voltage signal to a server; after relevant treatment, the motion characteristics of the high-viscosity gas-liquid material are obtained, and the gas-liquid motion characteristics such as the flow speed, the flow mode and the gas-liquid composition in the pipe are further obtained. Acoustic emission monitoring is a non-intrusive detection method, higher sensitivity and accuracy are achieved, additional sensors do not need to be installed on the pipeline, cost is reduced, and monitoring reliability is improved.

Description

Technical Field

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

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

[0003] Monitoring the flow status of highly viscous gas and liquid materials in pipelines is a technical challenge. Due to the poor light transmittance and strong adhesion of highly viscous liquids, the flow characteristics of highly viscous gas and liquid materials are complex and affected by many factors, including the viscosity of the material, temperature, material and shape of the pipeline, etc. In addition, traditional visual monitoring technology often requires the installation of additional sensors on the pipeline, which not only increases costs, but may also affect the integrity of the pipeline and the flow of materials, 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, fault diagnosis, etc. Acoustic emission signals are elastic waves caused by changes in the internal microstructure of the material, which can reflect the flow of materials in the pipeline in real time. However, applying acoustic emission technology to the flow state monitoring of high-viscosity gas and liquid materials requires solving technical problems such as signal collection and analysis.

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

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

[0007] The present invention is achieved through the following technical solutions:

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

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

[0010] (2) installing the first pipe fitting 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 fitting;

[0011] (3) Continuously monitor the acoustic signal. Since detailed signals cannot be obtained by performing wavelet decomposition with a scale lower than 3, the acoustic signal is decomposed by at least 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, firstly, multiple groups of high-viscosity gas-liquid materials with known gas-liquid two-phase flow rates but different flow rates are respectively passed into the first pipe for continuous acoustic signal monitoring, and the obtained acoustic signal energy is used 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, and its unit is the square of the measured voltage volt V, VG is the gas phase flow rate in the gas-liquid material, m 3 / h, VL is the liquid phase flow rate in the gas-liquid material, m 3 / h, the two-phase flow rate can be obtained by the flow meter

[0014] Among them, x, y, and z are the coefficients to be determined in the formula, and x is 1×10 -7 ~1×10 -1 , y is 3 to 6, c is 0.6 to 2;

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

[0016] The time domain waveform describes the change of the acoustic emission signal amplitude over time, and its signal strength can be measured by We get, where x n is the sample value of the original acoustic emission signal. The time domain features are directly extracted from the time series of the acoustic emission signal, reflecting the basic statistical properties and morphological characteristics of the signal. The time-frequency domain analysis can provide the frequency information of the signal over time, which is suitable for analyzing non-steady-state or rapidly changing signals.

[0017] Wavelet decomposition is an important time-frequency domain analysis method, which is achieved by convolving the signal with the 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 formula for wavelet decomposition is as follows:

[0018]

[0019]

[0020] In the formula, 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; k is the sampling index.

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

[0022] In the second aspect, the present invention provides an online monitoring system for the flow state of high-viscosity gas-liquid materials, the system comprising 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 pipe, which is used to monitor the stress changes caused by the flow of gas and liquid and the action of the wall, and convert it into a voltage signal, which is amplified by the preamplifier and the main amplifier and then transmitted to the acquisition card, and then processed and analyzed by the computer to obtain parameters characterizing the flow state of the high-viscosity gas-liquid materials 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 invention uses acoustic emission signal monitoring technology to monitor the flow state of high-viscosity gas-liquid materials in pipelines. By analyzing the characteristics of acoustic emission signals, the method can accurately identify the flow state of materials, including flow velocity, flow pattern, gas-liquid composition, and possible blockage conditions. Compared with traditional methods, the present invention has higher sensitivity and accuracy, and does not require the installation of additional sensors on the pipeline, which reduces costs and improves the reliability of monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0028] Figure 4 It is a comparison of the prediction effects of scale energy (L4+L5). DETAILED DESCRIPTION

[0029] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0030] like Figure 1 As shown, a test system provided with the monitoring system of the present invention comprises a first pipe fitting 1, a plunger pump 2, an acoustic emission probe 3, a preamplifier 4, a main amplifier 5, an acquisition card 6 and a computer 7. Among them, the acoustic emission probe 3, the preamplifier 4, the main amplifier 5, the acquisition card 6 and the computer 7 constitute the monitoring system of the flow state of the high-viscosity gas-liquid material of the present invention. The plunger pump is arranged at the feed inlet section of the first pipe fitting 1 to control the flow rate of the liquid transported into the pipe. The acoustic emission probe 3 is arranged 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 wave 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 acquisition card 6 to transmit the further amplified signal to the acquisition card, and the acquisition card 6 is connected to the computer 7 to analyze the collected signal to obtain the parameters characterizing the flow state of the high-viscosity gas-liquid material in the pipeline.

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

[0032] The high-viscosity gas-liquid material production system is composed of an air / liquid supply system and a reactor system. The air / liquid supply system transports air / water to the reactor system. The reactor system is composed of a feed port, a reciprocating pump, a reactor, and a discharge valve. The discharge valve is driven by a servo motor, and the valve opening is adjusted by a computer. During the experiment, when the material enters the reactor system through the feed port, the reciprocating pump pressurizes the material and transports it to the reactor. The material produced after the reaction enters the main pipeline through the discharge valve. In each reaction process, the material in the main pipeline is a high-viscosity gas-liquid material. In order to facilitate the subsequent gas-liquid separation of the high-viscosity gas-liquid material, the monitoring system proposed by the present invention can collect the acoustic signal of the flow of the high-viscosity gas-liquid material, and its flow state can be obtained by comparison.

[0033] During the experiment, the signal frequency upper limit was 500kHz, and it was decomposed into 8 scales. The specific frequency range of each scale was: 250-500kHz, 125-250kHz, 62.5-125kHz, 31.25-62.5kHz, 15.625-31.25kHz, 7.8125-15.625kHz, 3.90625-7.8125kHz, and 1.953125-3.90625kHz.

[0034] Figures 2 to 4 The original sound signal monitored by the high-viscosity gas-liquid material flow state monitoring system and the related characteristic parameters representing the gas-liquid movement obtained after processing.

[0035] Figure 2 The energy distribution of the annular flow acoustic emission signal after wavelet decomposition. The 4th scale energy (31.25-62.5kHz) and the 5th scale energy (15.625-31.25kHz) of the wavelet decomposition analysis are characteristic scales in the annular flow of high-viscosity fluids, which can better reflect the flow characteristics of the annular flow. Therefore, the energy distribution of these two scales under different operating conditions was further explored. Figure 3 The energy distribution of the 4th and 5th scales of the wavelet decomposition of the acoustic emission signal under different gas-liquid flow rates, (a) is the 4th scale, (b) is the 4th and 5th scales. The results show that the 4th and 5th scales can better reflect the flow state. Under any same gas flow rate, both the energy of the 4th scale and the sum of the energy of the 4th and 5th scales show 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, this is mainly caused by the vibration and shear of the gas-liquid interface. The model parameters were fitted by the least squares method and obtained. This empirical correlation. The predictive effect of this correlation is as follows Figure 4 Its experimental value is consistent with the above empirical correlation formula.

[0036] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. An online monitoring method for the flow state of high-viscosity gas-liquid materials, characterized in that: The method comprises at least the following steps: (1) providing a first pipe having at least one acoustic emission sensor installed therein; (2) installing the first pipe fitting 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 fitting; (3) Continuously monitor the acoustic signal, perform wavelet decomposition on the acoustic signal, and obtain the acoustic signal energy in the characteristic frequency range of the acoustic signal; (4) For a certain high-viscosity gas-liquid material to be monitored, firstly, multiple groups of high-viscosity gas-liquid materials with known gas-liquid two-phase flow rates are respectively passed into the first pipe for continuous acoustic signal monitoring, and the obtained acoustic signal energy is used to fit the undetermined coefficients in the following formula: E=x×VG y ×VL z Wherein E is the acoustic signal energy of the acoustic signal in the characteristic frequency range, and its unit is the square of the measured voltage volt V, VG is the gas phase flow rate in the gas-liquid material, m 3 / h, VL is the liquid phase flow rate in the gas-liquid material, m 3 / h; x, y, z are the coefficients to be determined in the formula, x is 1×10 -7 ~1×10 -1 , y is 3 to 6, z is 0.6 to 2; (5) For the high-viscosity gas-liquid material to be monitored, the first pipe with an acoustic emission sensor is used to obtain the acoustic signal energy in the characteristic frequency range of the acoustic signal, and the two-phase flow rate of the high-viscosity gas-liquid material is calculated according to the formula fitted in step (4), thereby obtaining the flow state of the high-viscosity gas-liquid material.

2. The online monitoring method for the flow state of high-viscosity gas-liquid materials according to claim 1 is characterized in that: The high-viscosity gas-liquid material contains at least one polymer, which is low-density polyethylene, or a copolymer of at least two monomers of ethylene and vinyl acetate, acrylic acid and its ester, and an olefin with a carbon number greater than 3.

3. The online monitoring method for the flow state of high-viscosity gas-liquid materials according to claim 1 is characterized in that: The liquid phase viscosity of the high-viscosity gas-liquid material is 1×10 3 ~1×10 6 mPa·s, temperature is 20~400℃, and pressure is 0.1~100MPa.

4. The online monitoring method for the flow state of high-viscosity gas-liquid materials according to claim 1 is characterized in that: In the step (3), the acquisition frequency of the acoustic signal is 10 to 1000 kHz, and the minimum value of the characteristic frequency range is greater than 1 kHz and the maximum value is less than 80 kHz.

5. The online monitoring method for the flow state of high-viscosity gas-liquid materials according to claim 1 is characterized in that: The wavelet decomposition method selected in step (3) is the Daubechies wavelet basis function, and preferably at least 3-scale wavelet decomposition is performed.

6. An online monitoring system for the flow state of high-viscosity gas-liquid materials for implementing the method of claim 1, characterized in that: The system includes 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 fitting. It is used to monitor the stress changes caused by the gas-liquid flow and the wall action, and convert it into a voltage signal. After amplification by the preamplifier and the main amplifier, it is transmitted to the acquisition card, and then processed and analyzed by the computer to obtain parameters characterizing the flow state of high-viscosity gas-liquid materials in the pipeline.

7. According to the online monitoring system of claim 6, the first pipe fitting is one of a straight pipe, a curved pipe, an elbow, a reducer, a flange, and a lens pad.

Images