A strain-based method and system for non-invasive monitoring of pipe flow pulsations

Abstract

The application provides a kind of pipeline gas flow pulsation non-destructive monitoring method and system based on strain, it is related to compressor technical field, including steps: measuring the circumferential strain and axial strain of pipeline;Strain and stress relationship of biaxial stress is calculated using Hook's law;Obtain the circumferential stress and axial stress relationship through pressure vessel theory;Obtain the internal pressure and strain relationship through circumferential stress and axial stress and strain and stress relationship;Drift correction value is calculated by circumferential strain and axial strain;The relationship between strain and stress, pressure vessel theory and drift correction value are used to calculate the dynamic pressure value in pipeline.The application constructs strain drift calculation algorithm, real-time correction is carried out to the strain drift phenomenon that appears in field strain measurement, to accurately reconstruct pipeline pulsation pressure, the comprehensive strain drift of multi-factor influence is corrected, the correction algorithm of pipeline strain drift is proposed, and the pulsation pressure in pipeline is accurately reconstructed based on drift correction strain.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and in particular to a strain-based non-destructive monitoring method and system for pipeline airflow pulsation. Background Technology

[0002] Airflow pulsation is caused by the intermittent intake and exhaust of compressor cylinders, resulting in periodic changes in gas velocity and pressure within the pipeline. Airflow pulsation is prevalent in many industrial applications, such as oil refining and chemical industries. It can lead to pipeline noise, vibration, and pressure fluctuations, and can also affect the measurement accuracy of flow meters and sensors, thus impacting the stability and efficiency of industrial production and even causing safety accidents. Therefore, monitoring and controlling airflow pulsation is essential. Pipeline airflow pulsation monitoring has significant practical implications. First, it helps understand the state of gas flow within the pipeline, providing fundamental data and a basis for pipeline design and optimization. Second, monitoring pipeline airflow pulsation allows for the timely detection of anomalies within the pipeline, enabling timely measures to prevent safety accidents. Furthermore, it can provide insights into energy transfer and loss during gas transportation. Pipeline airflow pulsation monitoring is a crucial technology and an indispensable component in ensuring system safety and operational efficiency.

[0003] Pipeline airflow pulsation monitoring can directly reflect the airflow state within the pipeline, ensuring the safe and stable operation of the system. Traditional airflow pulsation monitoring methods involve pre-drilling or later opening holes in the pressure pipeline, immersing a pressure sensor into the fluid being measured, and obtaining airflow pulsation parameters. This method obviously has many drawbacks: (1) the measurement point cannot be arbitrarily changed; (2) stress concentration occurs at the opening location; (3) it increases the risk of gas leakage; (4) it is limited by pressure sensor technology; and (5) replacing the pressure sensor requires system shutdown. Non-destructive testing (NDT) can improve the safety and reliability of monitoring. It does not require modifications inside the pipeline and will not interfere with the gas flow within the pipeline, allowing for safer and more reliable monitoring of airflow pulsation. NDT technology can achieve high-precision airflow pulsation monitoring, accurately measuring parameters such as the frequency and amplitude of airflow pulsation, thus improving the accuracy of monitoring data. NDT methods do not require periodic sensor replacement or maintenance, thus reducing monitoring and maintenance costs. In summary, NDT airflow pulsation monitoring has advantages such as safety, high precision, and low cost.

[0004] Strain drift refers to the deviation in the output signal of a resistance strain gauge due to factors such as temperature and mechanical stress. This deviation causes a discrepancy between the strain gauge's output signal and the actual strain, thus affecting the accuracy and reliability of the measurement results. Therefore, strain drift correction is unavoidable in applications requiring high-precision measurements.

[0005] The existing published literature, "An Investigation into Non-Invasive Pressure Measurement Methods," is characterized by: including a pipeline and a resistance strain gauge circuit; the strain gauges include circumferential strain gauges and circumferential strain gauges; the strain gauges are attached to the outer surface of the pipeline being measured; when the pipeline is deformed by internal pressure, the strain gauges deform along with the wall surface; the strain deformation causes a change in the resistance of the strain gauges, thereby obtaining the deformation parameters of the wall surface; and the airflow pulsation inside the pipeline is indirectly obtained based on the deformation parameters of the strain gauges.

[0006] It is evident that the existing technology does not take into account the causes of strain drift in sufficient depth, only considering temperature drift. Temperature drift can be compensated by temperature self-compensating strain gauges or by calculation. Temperature self-compensating strain gauges have a self-compensating temperature range, and the temperature self-compensation function of the strain gauge will fail if the temperature exceeds this range. In addition, strain drift is not only caused by temperature, but also by other factors, and the lack of drift compensation calculation leads to inaccurate monitoring results. Summary of the Invention

[0007] This invention provides a strain-based non-destructive monitoring method for pipeline airflow pulsation, aiming to solve the problem in the prior art where temperature drift is compensated by temperature self-compensating strain gauges, but the lack of drift compensation calculation leads to inaccurate monitoring results.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a strain-based non-destructive monitoring method for pipeline airflow pulsation, comprising the following steps:

[0009] Measure the circumferential strain at a specific location in the pipeline. With axial strain ;

[0010] Through the circumferential strain Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain ;

[0011] Calculate the circumferential strain using Hooke's law Axial strain With circumferential stress Axial stress relation;

[0012] The internal pressure and circumferential stress of the pipeline are calculated using the aforementioned pressure vessel theory. or axial stress Relationship;

[0013] Through the internal pressure and circumferential stress of the pipe or axial stress The relationship between the circumferential strain and the circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain in the pipeline is obtained.

[0014] The dynamic pressure value inside the pipeline is calculated based on the relationship between the internal pressure and strain of the pipeline.

[0015] Preferably, the circumferential strain Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain The steps include:

[0016] Obtain the circumferential drift With axial drift With circumferential strain With axial strain Relationship;

[0017] Based on the compressor base frequency F Sampling frequency f, based on one period circumferential strain With axial strain Calculate circumferential drift With axial drift ;

[0018] Through the circumferential drift With axial drift Obtain the circumferential strain after drift correction Axial strain ;

[0019] Calculate the corrected circumferential strain With axial strain difference.

[0020] Preferably, the step of obtaining the circumferential drift... With axial drift Circumferential strain compared to test values and axial strain The relationship, specifically expressed as:

[0021] ;

[0022] in, , —Poisson's ratio of the material.

[0023] Preferably, the step of basing the compressor's base frequency F Sampling frequency f, based on one period circumferential strain With axial strain Calculate circumferential drift With axial drift The specific expression is:

[0024] ;

[0025] in, , ... ... From 1 to The measured value of axial strain; , ... ... From 1 to Circumferential strain measurement value; , ... ... From 1 to Axial drift; , ... ... From 1 to Circumferential drift.

[0026] Preferably, the calculated corrected circumferential strain Axial strain The difference, specifically expressed as:

[0027] .

[0028] Preferably, the strain-stress relationship for calculating biaxial stress using Hooke's law is specifically expressed as follows:

[0029] ;

[0030] in: —Poisson's ratio of the material; E —Material elastic modulus.

[0031] Preferably, the internal pressure and circumferential stress of the pipeline are calculated using the pressure vessel theory. or axial stress Relationship, including steps:

[0032] According to pressure vessel theory, in the biaxial stress caused by the internal pressure on the outer surface of the pipe, the circumferential stress... Axial stress It is twice the pressure of the pipe, and it conforms to the following relationship with the internal pressure of the pipe:

[0033] ;

[0034] in, p —Pipe internal pressure; —Pipe inner diameter; —Outer diameter of the pipe.

[0035] Preferably, the circumferential stress and axial stress Relationships, and circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain is obtained through the following expression:

[0036] .

[0037] Preferably, the dynamic pressure value within the calculated pipeline is specifically expressed as follows:

[0038] ;

[0039] in, p This represents the dynamic pressure value within the pipeline.

[0040] The present invention also provides a strain-based non-destructive monitoring system for pipeline airflow pulsation, comprising:

[0041] Circumferential and axial strain gauges are used to measure the circumferential strain at a specific location in the pipeline. With axial strain ;

[0042] A drift correction module is used to correct the circumferential strain. Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain ;

[0043] The strain processing module is used to calculate the circumferential strain using Hooke's law. Axial strain With circumferential stress Axial stress relation;

[0044] The stress processing module is used to calculate the internal pressure and circumferential stress of the pipeline based on the pressure vessel theory. or axial stress Relationship;

[0045] The pipeline pressure handling module is used to handle the internal pressure and circumferential stress of the pipeline. or axial stress The relationship between the circumferential strain and the circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain in the pipeline is obtained.

[0046] The pressure output module is used to calculate the dynamic pressure value inside the pipeline based on the relationship between the internal pressure and strain of the pipeline.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] This invention constructs a strain drift calculation algorithm to correct the strain drift phenomenon that occurs in field strain measurement in real time, so as to accurately reconstruct the pipeline pulsating pressure, thereby obtaining the corrected strain and stress and the relationship between internal pressure and strain. It realizes the correction of comprehensive strain drift affected by multiple factors. Based on the drift correction strain, the pulsating pressure in the pipe is accurately reconstructed, which improves the error caused by drift and greatly improves the pipeline monitoring effect. Attached Figure Description

[0049] Figure 1 A diagram of the signal acquisition system provided by this invention;

[0050] Figure 2 The strain gauge layout diagram provided by this invention;

[0051] Figure 3 The experimental physical diagram provided for this invention;

[0052] Figure 4 The experimental results provided by this invention are shown in the figure. Detailed Implementation

[0053] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0054] This invention addresses the issue of non-destructive measurement of airflow pulsation and pressure within pipelines when it is impossible to install invasive pressure sensors for measurement without damaging the existing pipeline structure, or when existing pressure sensors fail and cannot be replaced, resulting in the inability to monitor pipeline pressure.

[0055] For the purpose of understanding and explanation, a strain-based non-destructive monitoring method and system for pipeline airflow pulsation according to an embodiment of the present invention will be described in detail below.

[0056] like Figure 1 As shown, the present invention provides a strain-based non-destructive monitoring method for pipeline airflow pulsation, comprising the following steps:

[0057] S1: Measure the circumferential strain at a specific location on the pipeline. and axial strain Two strain gauges are connected to a 1 / 4 bridge to measure circumferential and axial strain.

[0058] S2: Drift correction calculation. Based on one period. circumferential strain measurement value and axial strain measurement values Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain .

[0059] Circumferential drift With axial drift Circumferential strain compared to test values and axial strain And satisfy the following relationship:

[0060] ;

[0061] in, , —Poisson's ratio of the material.

[0062] Based on the compressor base frequency F Hz, sampling frequency f Hz, based on one cycle circumferential strain measurement value and axial strain measurement values Calculate the circumferential drift With axial drift The specific expression is:

[0063] ;

[0064] in, , ... ... From 1 to The measured value of axial strain; , ... ... From 1 to Circumferential strain measurement value; , ... ... From 1 to Axial drift; , ... ... From 1 to Circumferential drift.

[0065] Then, the circumferential strain measurement value after drift correction is obtained. and axial strain measurement values And calculate the difference between the two after correction. .

[0066] S3: For the biaxial stress state caused by internal pressure, calculate the circumferential strain according to Hooke's law for isotropic materials. Axial strain With circumferential stress Axial stress The relationship, specifically, is as follows:

[0067] ;

[0068] In the formula: —Poisson's ratio of the material; E —Material elastic modulus.

[0069] S4: Calculate the internal pressure and circumferential stress of the pipeline using pressure vessel theory. or axial stress The relationship is as follows: According to pressure vessel theory, in the biaxial stress caused by the internal pressure on the outer surface of a pipe, the circumferential stress is twice the axial stress, and it conforms to the following relationship with the internal pressure of the pipe:

[0070] ;

[0071] In the formula: p —Pipe internal pressure; —Pipe inner diameter; —Outer diameter of the pipe.

[0072] S5: Based on steps S3 and S4, the strain caused by internal pressure can be calculated to have the following relationship:

[0073] ;

[0074] S6: Calculate the dynamic pressure value in the pipeline based on the relationships in steps S2, S3, S4, and S5:

[0075] ;

[0076] in, p This represents the dynamic pressure value within the pipeline.

[0077] In practical applications, strain drift is not only caused by temperature, but also by the following reasons: (1) Temperature change. Temperature change can cause thermal expansion and contraction of the strain gauge itself, which can lead to strain drift. Temperature change can also cause changes in physical parameters such as the elastic modulus and linear expansion coefficient of the material, which can also interfere with strain measurement. (2) Mechanical stress. The strain gauge is affected by mechanical stress during operation, such as vibration, impact, and pressure. These mechanical stresses can cause deformation or changes in the internal structure of the strain gauge, which can lead to drift in the output signal of the strain gauge. (3) Electromagnetic interference. The strain gauge sensor is affected by external electromagnetic fields during operation, which can affect the circuit operation and signal transmission of the sensor, leading to drift in the strain output signal. (4) Installation error. The installation position, orientation, and fixing method of the strain gauge can affect its output signal, which can lead to strain drift. (5) Time drift. Time drift refers to the change in the output signal of the strain gauge after long-term use. Due to factors such as aging of the strain gauge material, fatigue of mechanical parts, and lifespan of electronic components, the performance of the sensor may change, which can lead to time drift.

[0078] like Figure 4 As shown in (a), the measured values ​​of circumferential strain and axial strain exhibit different degrees of drift, and this drift is not solely due to temperature drift but is a comprehensive drift influenced by multiple factors. Without drift correction, the measured values ​​will affect the calculated pulsating pressure. The results after drift correction are as follows... Figure 4 As shown in (b), the exhaust pressure is 110 MPa and the pulsating pressure amplitude is approximately 9.5 MPa.

[0079] like Figure 1-3 As shown, the present invention also includes a strain-based pipeline airflow pulsation non-destructive monitoring system, comprising a strain gauge, a bridge module, a pressure transmitter, a power supply module, a signal acquisition module, a digital signal processing module, and a computer.

[0080] The circumferential strain gauge and the axial strain gauge are each connected to a 1 / 4 bridge to measure the circumferential strain at a specific location in the pipeline. With axial strain The signal acquisition module receives axial strain and axial strain signals; the signal processing module includes a drift correction module, a strain processing module, a stress processing module, and a pipeline pressure processing module. The drift correction module is used to process circumferential strain... Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain The strain processing module is used to calculate circumferential strain using Hooke's Law. Axial strain With circumferential stress Axial stress Relationship; Stress processing module, used to calculate the internal pressure and circumferential stress of pipelines using pressure vessel theory. or axial stress Relationship; Pipeline pressure handling module, used to manage pipeline internal pressure and circumferential stress or axial stress Relationships, and circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain is obtained; the pressure value output module is used to calculate the dynamic pressure value in the pipeline through the relationship between the internal pressure and strain of the pipeline.

[0081] The above-described embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A strain-based non-destructive monitoring method for pipeline airflow pulsation, characterized in that, Including the following steps: Measure the circumferential strain at a specific location in the pipeline. With axial strain ; Through the circumferential strain Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain ; Calculate the circumferential strain using Hooke's law Axial strain With circumferential stress Axial stress relation; Calculation of internal pressure and circumferential stress in pipelines using pressure vessel theory. or axial stress Relationship; Through the internal pressure and circumferential stress of the pipe or axial stress The relationship between the circumferential strain and the circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain in the pipeline is obtained. The dynamic pressure value inside the pipeline is calculated based on the relationship between the internal pressure and strain of the pipeline. The circumferential strain Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain The steps include: Obtain circumferential drift With axial drift With circumferential strain With axial strain Relationship; Based on the compressor base frequency F Sampling frequency f, based on one period circumferential strain With axial strain Calculate circumferential drift With axial drift ; Through the circumferential drift With axial drift Obtain the circumferential strain after drift correction Axial strain ; Calculate the corrected circumferential strain With axial strain difference.

2. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 1, characterized in that, The acquisition of circumferential drift With axial drift With circumferential strain With axial strain The relationship, specifically expressed as: ； in, , —Poisson's ratio of the material.

3. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 1, characterized in that, The method based on the compressor base frequency F Sampling frequency f, based on one period circumferential strain With axial strain Calculate circumferential drift With axial drift The specific expression is: ； in, , ... ... From 1 to The measured value of axial strain; , ... ... From 1 to Circumferential strain measurement value; , ... ... From 1 to Axial drift; , ... ... From 1 to Circumferential drift.

4. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 1, characterized in that, The calculated corrected circumferential strain With axial strain The difference, specifically expressed as: 。 5. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 4, characterized in that, The circumferential strain is calculated using Hooke's law. Axial strain With circumferential stress Axial stress The relationship, specifically expressed as: ； in: —Poisson's ratio of the material; E —Material elastic modulus.

6. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 5, characterized in that, The internal pressure and circumferential stress of the pipeline are calculated using pressure vessel theory. or axial stress Relationship, including steps: According to pressure vessel theory, in the biaxial stress caused by the internal pressure on the outer surface of a pipe, the circumferential stress... Axial stress It is twice the pressure of the pipe, and it conforms to the following relationship with the internal pressure of the pipe: ； in, p —Pipe internal pressure; —Pipe inner diameter; —Outer diameter of the pipe.

7. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 6, characterized in that, Through the internal pressure and circumferential stress of the pipe or axial stress The relationship between the circumferential strain and the circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain in a pipeline is obtained through the following expression: 。 8. The strain-based non-destructive monitoring method for pipeline airflow pulsation as described in claim 7, characterized in that, The specific expression for calculating the dynamic pressure value within the pipeline is as follows: ； in, p This represents the dynamic pressure value within the pipeline.

9. A strain-based non-destructive monitoring system for pipeline airflow pulsation, characterized in that, include: Circumferential and axial strain gauges are used to measure the circumferential strain at a specific location in the pipeline. With axial strain ; A drift correction module is used to correct the circumferential strain. Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain ; The strain processing module is used to calculate the circumferential strain using Hooke's law. Axial strain With circumferential stress Axial stress relation; The stress processing module is used to calculate the internal pressure and circumferential stress of pipes using pressure vessel theory. or axial stress Relationship; The pipeline pressure handling module is used to control the internal pressure and circumferential stress of the pipeline. or axial stress The relationship between the circumferential strain and the circumferential strain Axial strain With circumferential stress Axial stress The relationship between internal pressure and strain in the pipeline is obtained. The pressure output module is used to calculate the dynamic pressure value inside the pipeline based on the relationship between the internal pressure and strain of the pipeline. The circumferential strain Axial strain Calculate the drift value, and use the drift value to adjust the circumferential strain. Axial strain Make corrections to obtain the corrected circumferential strain. Axial strain The steps include: Obtain circumferential drift With axial drift With circumferential strain With axial strain Relationship; Based on the compressor base frequency F Sampling frequency f, based on one period circumferential strain With axial strain Calculate circumferential drift With axial drift ; Through the circumferential drift With axial drift Obtain the circumferential strain after drift correction Axial strain ; Calculate the corrected circumferential strain With axial strain difference.

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