CN117705353A - Long-distance pumping pipeline blocking state identification method based on fiber bragg grating sensing - Google Patents
Long-distance pumping pipeline blocking state identification method based on fiber bragg grating sensing Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 description 15
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Abstract
The invention discloses a method for identifying the blocking state of a long-distance pumping pipeline based on fiber bragg grating sensing, which specifically comprises the following steps: step 1, arranging FBG strain sensors, and obtaining a wavelength value lambda in a gangue pumping working state B The method comprises the steps of carrying out a first treatment on the surface of the Step 2, according to lambda B The wavelength change value delta lambda of the reflected light wave of the fiber Bragg grating is calculated B And will delta lambda B The change amount delta epsilon converted into axial strain a The method comprises the steps of carrying out a first treatment on the surface of the Step 3, changing the axial strain change delta epsilon obtained in the step 2 a The time is converted into strain acceleration value epsilon a (t); step 4, utilizing the strain acceleration value epsilon' obtained in the step 3 a (t) the degree of clogging of the cross section of the pipe is classified according to the clogging grade. The invention converts the strain of directly measuring the blocking state of the long-distance gangue pumping pipeline into indirect measurement, and improves the accuracy of the identifying result of the blocking state of the pipeline.
Description
Technical Field
The invention belongs to the technical field of pipeline transportation, and relates to a method for identifying a blocking state of a long-distance pumping pipeline based on fiber bragg grating sensing.
Background
Strain is one of important parameters reflecting the running state of a pipeline conveying system, and is a key for identifying the blocking state of the long-distance gangue pumping pipeline, accurately testing and obtaining the micro deformation of the long-distance gangue pumping pipeline, and implementing strain detection is a key for identifying the blocking state of the long-distance gangue pumping pipeline. At present, for the identification method of the blocking state of the long-distance gangue pumping pipeline, the traditional method is to paste the traditional strain sensor on the surface of the pipeline axially to identify the blocking state of the long-distance gangue pumping pipeline, however, the traditional identification method has the following defects: the common strain measurement method is to paste strain gauges on the surface of a pipeline, and the sizes and the dead weights of the traditional strain gauges and the transmission cables can have certain influence on the flow field and the pumping power performance on the surface of the pipeline because the pipeline is in an operating state, so that the accuracy of the identification result is influenced.
Disclosure of Invention
The invention aims to provide a method for identifying the blocking state of a long-distance pumping pipeline based on fiber bragg grating sensing, which converts the strain of directly measuring the blocking state of the long-distance gangue pumping pipeline into indirect measurement, and improves the accuracy of the identifying result of the blocking state of the pipeline.
The technical scheme adopted by the invention is that the method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing specifically comprises the following steps:
step 1, arranging FBG strain sensors on a pumping pipeline, and obtaining wavelength value lambda of the FBG strain sensors in a gangue pumping working state B ；
Step 2, according to the wavelength value lambda measured in step 1 B The wavelength change value delta lambda of the reflected light wave of the fiber Bragg grating is calculated B And will delta lambda B The change amount delta epsilon converted into axial strain a ；
Step 3, utilizing the relation principle of FBG vibration sensor strain and acceleration to change the axial strain change delta epsilon obtained in the step 2 a The time is converted into strain acceleration value epsilon a (t)；
Step 4, utilizing the strain acceleration value epsilon' obtained in the step 3 a (t) the degree of clogging of the cross section of the pipe is classified according to the clogging grade.
The invention is also characterized in that:
the specific process of the step 1 is as follows:
arranging a plurality of FBG strain sensors at measuring points on the surface of a pipeline, namely, paving the FBG strain sensors right above the wall surface of a pumping pipeline by using a surface pasting method, fixing a grating region by using epoxy resin, sequentially connecting each FBG strain sensor in series, connecting one end of one FBG strain sensor positioned at the end with an FBG demodulator, connecting the FBG demodulator with a display by a jumper wire, and displaying a wavelength value lambda by the display after the grouting pump is started B 。
The specific process of the step 2 is as follows:
step 2.1, calculating the wavelength variation delta lambda of the reflected light wave of the fiber Bragg grating fed back by the FBG strain sensor by adopting the following formula (1) B ：
In the method, in the process of the invention,the initial wavelength of the fiber Bragg grating;
step 2.2, under the condition of changing the external temperature, the shift of the central wavelength of the reflection spectrum is influenced by the change of the stress field of the fiber bragg grating sensor and by the change of the temperature field, thereby obtaining the wavelength change value delta lambda of the reflection light wave of the fiber bragg grating in the temperature change state B The following formula (2) shows:
the change delta epsilon of the axial strain of the area where the FBG strain sensor grating is located under the condition of changing the external temperature is obtained by the method (2) a The following formula (3) shows:
wherein: delta T is the temperature difference;for axial strain sensitivity coefficient, alpha T Is the temperature sensitivity coefficient.
The specific process of the step 3 is as follows:
the strain signal is subjected to first order derivative for time t, namely the strain rate is obtained by differentiating the strain signal:
wherein L is 0 For the original length of the fiber, L (t) is the length of the fiber at each time t, v (t) is the speed at which the fiber is drawn at each time t;
then the second derivative is obtained for the time t of the strain signal, namely the strain acceleration epsilon' is obtained by the secondary differentiation of the strain signal a (t)：
Where a (t) is the acceleration at which the fiber is stretched at each time t.
In the step 4, the blockage grades are classified into a severe blockage L4, a general blockage L3, a slight blockage L2 and an unblocked blockage L1;
when the strain acceleration value is [ epsilon ] a (t) s＝0 ，ε″ a (t)s ＝20％ ]When the blockage grade is L1;
when the strain acceleration value is [ epsilon ] a (t) s＝20％ ，ε″ a (t) s＝40％ ]When the blockage grade is L2;
when the strain acceleration value is [ epsilon ] a (t) s＝40％ ，ε″ a (t) s＝60％ ]When the blockage grade is L3;
the strain acceleration value is [ epsilon ] a (t) s＝60％ ，ε″ a (t) s＝100％ ]When the clogging grade was L4.
The beneficial effects of the invention are as follows:
1. the invention provides a strain measurement method based on fiber gratings (fiber bragg grating, FBG), which converts the strain of directly measuring the blocking state of a long-distance gangue pumping pipeline into indirect measurement, considers the influence of temperature on the fiber gratings, eliminates the sensitivity of the fiber gratings to the temperature strain, introduces multi-channel data, and has time sequence, so that the data base of the identification method is more scientific;
2. the method can detect the blocking degree of the long-distance gangue pumping pipeline in real time and can rapidly guide the dredging operation of the pipeline; the method is not affected by pipe quality, and the components of the long-distance gangue pumping pipeline are not required to be disassembled when the fiber bragg grating sensor is installed, so that the normal operation of the long-distance gangue pumping pipeline is not affected;
3. the invention designs a corresponding blocking class grading and blocking identification method aiming at the blocking degree (including multi-channel data) of the long-distance gangue pumping pipeline, and provides a basis for more accurately identifying the blocking degree of the long-distance gangue pumping pipeline.
Drawings
FIG. 1 is a fiber grating sensing schematic diagram of an FBG strain sensor used in a fiber grating sensing-based long-distance pumping pipeline blocking state identification method;
FIG. 2 is a state diagram of an FBG strain sensor stuck on a pipeline in a method for identifying the blocking state of a long-distance pumping pipeline based on fiber bragg grating sensing;
FIG. 3 is a schematic diagram of the arrangement of FBG strain sensors in the method for identifying the blocking state of a long-distance pumping pipeline based on fiber grating sensing;
fig. 4 is a time domain diagram of strain acceleration in the method for identifying the blocking state of the long-distance pumping pipeline based on fiber grating sensing.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
Example 1
The invention discloses a method for identifying the blocking state of a long-distance pumping pipeline based on fiber bragg grating sensing, which specifically comprises the following steps:
step 1, arranging FBG strain sensors at measuring points on the surface of a pipeline, namely laying the FBG strain sensors right above the wall surface of the pipeline by using a surface pasting method, fixing a grating area by using epoxy resin, sequentially connecting the FBG strain sensors in series, selecting one end of each of the FBG strain sensors to be connected with an FBG demodulator, connecting the FBG demodulator with a display through a jumper wire, and displaying a wavelength value lambda on the display when a grouting pump is started B ；
The sensing principle of the FBG strain sensor is shown in fig. 1.
The incident light is a broadband spectrum containing a plurality of wavelengths, when the incident light is incident to the grating region, only light waves with specific wavelengths are reflected, and light waves with other wavelengths are not affected and directly propagate along the optical fiber through the grating position, wherein the wavelength of the reflected light waves is Bragg wavelength, and the wavelength lambda is B The expression is:
λ B ＝2n eff ∧ (1)
wherein: lambda (lambda) B The reflection wavelength of the fiber Bragg grating; Λ is the period of the grating; n is n eff Is the effective refractive index of the grating. The main factors determining the reflection wavelength of the grating are ∈n eff . When the fiber grating sensor is subjected to external force to cause deformation of the grating area, the axial strain of the grating is changed, and the alpha and the n are caused eff And also changes, ultimately resulting in lambda B A change; when the temperature of the grating changes, the optical fiber material thermally expands or contracts to generate strain, thereby causing lambda B Is a variation of (c).
Step 2, using FBG sensing principle to measure wavelength lambda B And subtracting the shifted wavelength values to obtain a wavelength difference value, and converting the wavelength difference value into a strain value variation delta epsilon a ；
Based on the spectral information of the wavelength, the light intensity and the like of the light wave collected by the FBG strain sensor, the change of the wavelength of the light wave returned by the sensor in the experimental process is calculated, and the change value delta lambda of the wavelength of the reflected light wave B The expression:
wherein:the initial wavelength of the fiber Bragg grating; Δλ (delta lambda) B The wavelength variation value of the reflected light wave is the fiber Bragg grating.
Under the condition of changing the external temperature, the deviation of the central wavelength of the reflection spectrum is influenced by the change of the stress field of the fiber bragg grating sensor and by the change of the temperature field, so that the wavelength change expression in the temperature change state can be obtained.
The strain value expression of the area where the FBG strain sensor grating is located under the condition of changing the external temperature is obtained by the expression (3):
wherein: delta epsilon a Is the variation of axial strain; delta T is the temperature difference;for axial strain sensitivity coefficient, alpha T Is the temperature sensitivity coefficient.
Step 3, utilizing the relation principle of the strain and the acceleration of the FBG vibration sensor to change the strain value delta epsilon a The time is converted into strain acceleration value epsilon a (t)；
The vibration signal is a high-frequency component of strain, the frequency and the amplitude of the vibration signal can be obtained through Fourier transformation by high-speed sampling of a strain measurement value, and the strain acceleration signal is indirectly obtained by measuring the strain due to the fact that the acceleration is relatively sensitive in a high-frequency range.
The strain signal obtained by converting the wavelength signal measured by the fiber bragg grating is derived twice from time to obtain a strain rate signal and a strain acceleration signal.
The strain signal is subjected to first order derivative for time t, namely the strain rate is obtained by differentiating the strain signal:
wherein L is 0 For the original length of the fiber, L (t) is the length of the fiber at each time t, and v (t) is the speed at which the fiber is drawn at each time t.
And then, obtaining a second derivative for the time t of the strain signal, namely obtaining the strain acceleration by performing secondary differentiation on the strain signal:
where a (t) is the acceleration at which the fiber is stretched at each time t.
Step 4, using Table 1 to obtain strain acceleration value ε a (t) dividing the degree of clogging of the cross section of the pipe into ranges according to the clogging grades (L1 to L4).
Example 2
Based on the embodiment 1, the specific process of the step 4 is as follows:
the blockage levels are divided into four levels of severe blockage (L4), general blockage (L3), slight blockage (L2) and unblocked (L1); the criteria for the classification of the clogging grade are shown in Table 1, with strain acceleration values [ ε ] a (t) s＝0 ，ε″ a (t) s＝20％ ]The blocking range of the non-blocking (L1), namely the pipeline cross section, is 0-20%; the strain acceleration value is [ epsilon ] a (t) s＝20％ ，ε″ a (t) s＝40％ ]Slight blockage (L2) means that the blockage range of the pipeline cross section is 20% -40%; the strain acceleration value is [ epsilon ] a (t) s＝40％ ，ε″ a (t) s＝60％ ]The method comprises the steps of carrying out a first treatment on the surface of the The common blockage (L3) is that the blockage range of the pipeline cross section is 40% -60%; the strain acceleration value is [ epsilon ] a (t) s＝60％ ，ε″ a (t) s＝100％ ]The method comprises the steps of carrying out a first treatment on the surface of the The severe blockage (L4) is that the blockage range of the pipeline cross section is 60-100 percent.
Table 1 blocking range class classification table
| Range of strain acceleration values | Degree of blockage of pipeline cross section | Grade of blockage |
| 0≤ε″ a (t)＜2 | 0≤s<20％ | Unblocking (L1) |
| 2≤ε″ a (t)＜4 | 20％≤s<40％ | Slight blockage (L2) |
| 4≤ε″ a (t)＜6 | 40％≤s<60％ | General plug (L3) |
| ε″ a (t)≥6 | 60％≤s<100％ | Severe blockage (L4) |
In the formula epsilon% a (t) -different monitoring point strain acceleration values; s=i% -degree of blockage of the cross section of the pipeline.
Example 3
The experimental platform selects a steel pipeline with the length of 15.5m and the diameter of 50mm, two ends of the pipeline are respectively connected with a water storage tank, the water storage tanks are connected with a grouting pump through high-pressure hoses, the front end of the grouting pump is also connected to the pipeline through the high-pressure hoses, and the grouting pump starts grouting when the experiment starts and is used for simulating the real working state of the long-distance gangue pumping pipeline. Considering the smoothness of the layer of the pipeline wall surface, the layout positions of the FBG strain sensors are paved as follows.
Firstly, when the FBG strain sensor is paved right above the pipeline wall surface by a surface pasting method, in order to avoid uneven stress cracking of the sensor grid area during pasting, the paving thickness of the sensor is more than 10 times of the diameter of the sensor; next, FBG strain sensors are horizontally stuck and laid along the pipe, and the grating area is fixed by epoxy resin, as shown in fig. 2.
The method comprises the steps of customizing an FBG serial scheme by considering the wavelength division multiplexing property of an FBG strain sensor, then fixing a grating region by using epoxy resin, avoiding the corrosion of fluid to an optical fiber grating and the influence of too thick, too much or too little adhesive layer on the optical fiber grating, placing the optical fiber grating sensor at a wall A point (FBG-H01) of a long-distance gangue pumping pipeline to receive vibration signals flowing from the pipeline by gangue in the pipeline according to the consideration, and analyzing and processing the frequency of wavelength signals by a monitoring host; the point A is arranged at the center of a straight pipe of the long-distance gangue pumping pipeline; setting a monitoring point B (FBG-H02) 2.2m away from the point A on the pipe wall, and monitoring the wavelength signal intensity at the point B; the point B is arranged at one side of the point A along the flowing direction of the gangue; a monitoring point C (FBG-H03) is arranged 4.4m away from the point B in the direction from the point A to the point B, points D (FBG-H04) and E (FBG-H05) are respectively arranged on the left side and the right side of the valve (namely on the two sides of the valve in the gangue flow direction), a distance of 0.5m is reserved between the D, E points, and a monitoring point F (FBG-H06) is arranged 1.1m away from the point E in the direction from the point D to the point E. And detecting a wavelength signal intensity peak point X of the section, wherein the wavelength average amplitude of the point is a criterion for detecting the pipeline blockage degree of the section. Fig. 3 shows a manner of attaching the FBG strain sensor to the pipe wall.
Serial FBG strain sensors (FBG H01-FBG H06) are customized according to the pre-buried positions and the strain measurement ranges of the FBG strain sensors, the serial numbers, the central wavelength configuration and the serial connection modes of the sensors are shown in table 2, and the sensors are distinguished through a wavelength division multiplexing technology.
Table 2FBG strain sensor configuration schematic table
And the FBG strain sensor is used for measuring the strain acceleration of the pipe wall under different valve flow states, and a time domain diagram of the strain acceleration change trend is shown in figure 4.
And acquiring the blockage strain acceleration data of the long-distance gangue pumping pipeline under the working conditions through the FBG strain sensor, and performing time domain analysis. The change trend of different monitoring points for gangue blockage monitoring along the length direction of the pipe is approximately the same, the strain acceleration of the sensor after the blockage position is linearly increased in different trends, and when the strain acceleration value at the FBG-H05 monitoring point is-4.70, namely the blockage is avoided (L1); when the strain acceleration value at the FBG-H05 monitoring point is 0.59, namely no blockage (L1) occurs; strain acceleration value at FBG-H05 monitoring point is 3.58, i.e. slight blockage (L2); the strain acceleration value at the FBG-H05 monitoring point is 3.67, namely slight blockage (L2); the strain acceleration value at the FBG-H05 monitoring point is 4.70, namely the general blockage (L3); when the strain acceleration value at the FBG-H05 monitoring point is 6.13, namely the serious blockage (L4); the strain acceleration value at the FBG-H05 monitoring point was 7.05, i.e. severe plugging (L4).
Claims (5)
1. The method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing is characterized by comprising the following steps of: the method specifically comprises the following steps:
step 1, arranging FBG strain sensors on a pumping pipeline, and obtaining wavelength value lambda of the FBG strain sensors in a gangue pumping working state B ；
Step 2, according to the wavelength value lambda measured in step 1 B The wavelength change value delta lambda of the reflected light wave of the fiber Bragg grating is calculated B And will delta lambda B The change amount delta epsilon converted into axial strain a ；
Step 3, utilizing the relation principle of FBG vibration sensor strain and acceleration to change the axial strain change delta epsilon obtained in the step 2 a The time is converted into strain acceleration value epsilon a (t)；
Step 4, utilizing the strain acceleration value epsilon' obtained in the step 3 a (t) the degree of clogging of the cross section of the pipe is classified according to the clogging grade.
2. The method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing according to claim 1, wherein the method comprises the following steps: the specific process of the step 1 is as follows:
arranging a plurality of FBG strain sensors at measuring points on the surface of a pipeline, namely, paving the FBG strain sensors right above the wall surface of a pumping pipeline by using a surface pasting method, fixing a grating region by using epoxy resin, sequentially connecting each FBG strain sensor in series, connecting one end of one FBG strain sensor positioned at the end with an FBG demodulator, connecting the FBG demodulator with a display by a jumper wire, and displaying a wavelength value lambda by the display after the grouting pump is started B 。
3. The method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing according to claim 2, wherein the method comprises the following steps of: the specific process of the step 2 is as follows:
step 2.1, calculating the wavelength variation delta lambda of the reflected light wave of the fiber Bragg grating fed back by the FBG strain sensor by adopting the following formula (1) B ：
In the method, in the process of the invention,the initial wavelength of the fiber Bragg grating;
step 2.2, under the condition of changing the external temperature, the shift of the central wavelength of the reflection spectrum is influenced by the change of the stress field of the fiber bragg grating sensor and by the change of the temperature field, thereby obtaining the wavelength change value delta lambda of the reflection light wave of the fiber bragg grating in the temperature change state B The following formula (2) shows:
the change delta epsilon of the axial strain of the area where the FBG strain sensor grating is located under the condition of changing the external temperature is obtained by the method (2) a The following formula (3) shows:
wherein: delta T is the temperature difference;for axial strain sensitivity coefficient, alpha T Is the temperature sensitivity coefficient.
4. The method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing according to claim 3, wherein the method comprises the following steps of: the specific process of the step 3 is as follows:
the strain signal is subjected to first order derivative for time t, namely the strain rate is obtained by differentiating the strain signal:
wherein L is 0 For the original length of the fiber, L (t) is the length of the fiber at each time t, v (t) is the speed at which the fiber is drawn at each time t;
and then, obtaining a second derivative for the time t of the strain signal, namely obtaining the strain acceleration epsilon' a (t) by twice differentiating the strain signal:
where a (t) is the acceleration at which the fiber is stretched at each time t.
5. The method for identifying the blocking state of the long-distance pumping pipeline based on fiber bragg grating sensing according to claim 4, wherein the method comprises the following steps of: in the step 4, the blockage grades are classified into a severe blockage L4, a general blockage L3, a slight blockage L2 and an unblocked blockage L1;
when the strain acceleration value is [ epsilon ] a (t) s＝0 ，ε″ a (t) s＝20％ ]When the blockage grade is L1;
when the strain acceleration value is [ epsilon ] a (t) s＝20％ ，ε″ a (t) s＝40％ ]When the blockage grade is L2;
when the strain acceleration value is [ epsilon ] a (t) s＝40％ ，ε″ a (t) s＝60％ ]When the blockage grade is L3;
the strain acceleration value is [ epsilon ] a (t) s＝60％ ，ε″ a (t) s＝100％ ]When the clogging grade was L4.
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