A multi-sensor arrangement method for pipeline leak detection

Abstract

The application provides a multi-sensor arrangement method for pipeline leakage detection, and belongs to the field of pipeline leakage detection. The multi-sensor arrangement method firstly establishes a positioning equation of a leakage hole position according to the basic principle of the transient flow reflection method, secondly changes the position of a sensor to determine an optimal point of the sensor arrangement, and finally changes the arrangement number of the sensor according to the obtained optimal point of the sensor arrangement to further determine the optimal arrangement number of the sensor. The application proposes a positioning equation suitable for multi-sensor positioning based on the transient flow reflection method, and the arrangement method of the multi-sensor can significantly improve the positioning accuracy for the pipeline leakage hole.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pipeline leakage detection, and relates to a multi-sensor arrangement method for pipeline leakage detection. BACKGROUND

[0002] With the rapid development of infrastructure construction in China, the construction of water supply networks is also being continuously carried out. However, most of the water supply networks in China were built in the mid-20th century. Due to long-term service and lack of maintenance, water supply pipelines have different forms and degrees of leakage. Pipeline leakage has caused great losses to the national economy, and has also caused great safety hazards and energy waste. Improving the pipeline leakage positioning method and enhancing the precision have become a problem to be solved.

[0003] The purpose of the pipeline detection system is to quickly determine the pipeline leakage position and leakage size, and to make emergency treatment to reduce the economic loss of users. The current pipeline leakage detection technology can be divided into three categories: external detection method, wall detection method and internal flow state detection method. The internal flow state detection method has the advantages of easy analysis, accurate positioning, small noise signal interference, etc., and has been widely applied.

[0004] The method relied on by the present application is the transient flow reflection method, that is, when the valve of the pipeline is closed, the fluid pressure in the pipeline will also change, thereby causing the transient flow of the fluid in the pipeline. It is one of the commonly used methods in the internal flow state detection method of the pipeline. This method has the advantages of fast response speed and high positioning accuracy. However, at present, the pipeline leakage detection based on the transient flow reflection method mostly arranges sensors at the valve at the end of the pipeline, and determines the specific leakage position of the pipeline by analyzing the waveform characteristics of the superimposed reflection wave and water hammer wave. This sensor arrangement method also has some significant shortcomings, such as: the pipeline leakage detection system in Dong Peiling. Pipeline leakage monitoring comprehensive simulation experiment system research [Hubei: Wuhan University of Technology, 2016.] has poor positioning accuracy for leakage position detection. So far, there is little research on the influence of sensor arrangement position and sensor quantity on the positioning accuracy of the leakage point, and therefore there is a lack of theoretical basis for the selection of sensor arrangement position and sensor quantity. Therefore, how to improve the positioning accuracy of the transient flow method has become a problem to be solved in the current pipeline leakage detection field. SUMMARY

[0005] To solve the above problems, the present application provides a multi-sensor arrangement method for pipeline leakage detection.

[0006] The technical scheme adopted by the present application is:

[0007] A method for multi-sensor arrangement of pipeline leakage, first, according to the basic principle of transient flow reflection method, a positioning equation of the leakage hole position is established, second, the position of the sensor is changed to determine the preferred point of the sensor arrangement, and finally, according to the preferred point of the sensor arrangement obtained, the arrangement number of the sensor is changed to determine the optimal sensor arrangement number. The specific steps are as follows:

[0008] First, according to the basic principle of transient flow reflection method, the positioning equation of the leakage hole is established.

[0009] According to the principle of transient flow reflection method, when the valve is closed, the pressure wave generated by the valve will propagate along the pipeline at a speed of 1000m / s. The pressure wave propagating along the pipeline contains leakage information, so the pressure sensor installed on the pipeline can capture the pressure wave containing the leakage information, and the leakage can be detected. And according to the time difference of the pressure wave generated by the leakage and transmitted to the end of the pipeline and then transmitted back, the position of the leakage hole can be obtained. According to the above basic principle of transient flow reflection method, the positioning equation of the leakage hole position is established.

[0010] In the traditional leakage hole positioning based on transient flow reflection method, the sensor is arranged at the outlet of the pipeline.

[0011] According to the principle of transient flow reflection method, the flow rate of the fluid in the pipeline is much smaller than the propagation speed of the pressure wave, so it can be ignored.

[0012] However, the above method has the problem of insufficient positioning accuracy, so the present application proposes an improved scheme, which changes the arrangement position and arrangement number of the sensor, and modifies the traditional transient flow reflection method to make it suitable for multi-sensor leakage hole positioning. The modified leakage hole positioning equation is updated as:

[0013] (1)

[0014] In the formula, x is the length of the leakage hole from the inlet of the pipeline; v is the propagation speed of the pressure wave in the pipeline; n is the number of sensors; L is the total length of the pipeline; l i is the distance of the sensor from the inlet of the pipeline; i=1, 2, …, n; t xi is the time of the pressure wave generated after the valve is closed, transmitted from the outlet of the pipeline to the position of the leakage hole, and then reflected to the i(i=1, 2, …, n)th sensor.

[0015] Therefore, the positioning error of the leakage hole can be calculated by the following formula:

[0016] (2)

[0017] In the formula, x *is the actual measured position of the pipe leakage hole; ε is the positioning error of the leakage hole.

[0018] Secondly, several three-dimensional models of the pipe with leakage holes in different positions are established in the three-dimensional modeling software, and the geometric model files are output.

[0019] Thirdly, the geometric model established in the second step is imported into the Fluent module of the ANSYS Workbench software platform to simulate the pipe leakage, and the boundary conditions such as fluid-related parameters and leakage hole position are set, which are as follows:

[0020] In order to obtain the variation law of the positioning error of the leakage hole under different numbers and arrangement positions of sensors, the pipe leakage and detection are simulated in the Fluent module of the ANSYS Workbench software platform, and the pipe-related parameters are set. According to the actual use, the pipe parameters in the simulation include: fluid density (kg / m 3 ), fluid elastic modulus (Pa), fluid Poisson's ratio, fluid density variation range, inlet pressure (KPa), outlet pressure (KPa), time step (s), and turbulence intensity, etc.

[0021] Further, the solver based on the turbulence model is established in the Fluent module, the grid is divided, the boundary conditions are set, and the numerical simulation is performed to obtain the pressure distribution and flow field distribution of the pipe. When dividing the grid of the pipe model with a leakage hole, attention should be paid to grid refinement at the leakage hole to ensure the accuracy of numerical simulation.

[0022] Fourthly, the sensor is arranged at the outlet of the pipe when the leakage hole is located between the inlet and outlet of the pipe. The position of the leakage hole is calculated according to the traditional transient flow reflection positioning formula, and compared with the actual position of the pipe leakage hole to obtain the corresponding positioning error.

[0023] Fifthly, under the condition that the position of the leakage hole is fixed, the position of the sensor is changed, and the numerical simulation is performed. The position of the leakage hole is calculated according to the modified transient flow reflection positioning formula, and compared with the actual position of the pipe leakage hole. Then the relationship between the sensor position and the positioning error is obtained, and several positions with smaller positioning error are selected as the preferred points for arranging the sensors.

[0024] Sixthly, after determining the preferred points for arranging the sensors, the number of the arranged sensors is changed, and the positioning error of the leakage hole is calculated according to the modified transient flow reflection positioning equation. The relationship between the number of sensors and the positioning error is studied under the condition that the position of the leakage hole is fixed, and the preferred arrangement number of several sensors is obtained.

[0025] Further, the position of the leakage hole is changed to explore the relationship between the number of sensors and the positioning error when the leakage occurs at different positions, and the positioning accuracy of the conventional transient flow reflection method is compared to determine the optimal number of sensor arrangements globally.

[0026] The beneficial results of the present application are:

[0027] The present application proposes a positioning equation based on the transient flow reflection method for multi-sensor positioning. A multi-sensor arrangement method for pipeline leakage is proposed, which can significantly improve the positioning accuracy for pipeline leakage holes. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Principle diagram of transient flow reflection method of multi-sensor arrangement

[0029] Figure 2 Specific implementation flowchart of the method of the present application

[0030] Figure 3 When the leakage hole is 6m away from the inlet, the relationship between the positioning error and the sensor arrangement position is shown in the figure

[0031] Figure 4 Comparison figure of different sensor positions on different position leakage hole positioning error DETAILED DESCRIPTION

[0032] In order to make the application purpose, implementation scheme and advantages of the method of the present application more clear and explicit, the method of the present application is described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0033] A multi-sensor arrangement method for pipeline leakage detection is provided in some embodiments of the present specification. Taking a 15m long pipeline as an example, the method comprises the following steps:

[0034] Step 1: As shown in Figure 1 1, 2 and 3 are leakage hole, sensor and valve respectively. According to the basic principle of transient flow reflection method, the leakage hole positioning equation is established. When a single sensor is arranged at the end of the pipeline, when multiple sensors are arranged between the beginning and end of the pipeline, the leakage hole positioning equation is formula (1).

[0035] Step 2: Establish a three-dimensional structure model of the pipeline with a leakage hole, and output a geometric model file. According to the actual situation, the pipeline model parameters established are shown in Table 1 as follows:

[0036] Table 1 Related parameters of pipeline model

[0037]

[0038] Step 3: The established geometric model is imported into the Fluent module of the ANSYS Workbench software platform, and fluid-related parameters are set. The fluid-related parameters set in the Fluent module are shown in Table 2:

[0039] Table 2 Fluid-related parameters in the Fluent module

[0040]

[0041] Further, in the Fluent module, each boundary condition is set, numerical simulation is performed, and the pressure distribution and flow field distribution of the pipeline are obtained.

[0042] To simplify the calculation, the mesh is set to polyhedral mesh, which can greatly reduce the number of meshes, shorten the calculation time and improve the calculation efficiency, unlike the traditional tetrahedral mesh and hexahedral mesh. At the same time, in order to improve the accuracy of the calculation, the mesh of the leakage hole of the pipeline needs to be encrypted, the leakage hole diameter is set to 10mm, and the BOI method, i.e. the influence body method, is selected to encrypt the mesh. The BOI method can encrypt the whole area without splitting the initial geometry. In order to ensure the stability of the calculation, the numerical simulation is performed in the order of first steady-state simulation and then transient simulation based on the steady-state simulation results.

[0043] The remaining boundary conditions are as follows: the inlet and outlet are both pressure boundary conditions, the pressure difference is 500KPa, and the state boundary condition calculation of all models is calculated using a turbulence model. The mesh amplitude of the polyhedral mesh division is not more than 5mm, and the mesh amplitude of the BOI encryption is not more than 1mm. The expansion layer is set to 5 layers.

[0044] Step 4: Only the sensor is set at the outlet, numerical simulation is performed, the leakage hole position is calculated according to the traditional transient flow reflection method positioning equation, and the positioning error is calculated by comparing with the preset leakage hole.

[0045] The simulation is divided into 14 groups, and the leakage hole position obtained by the traditional method of arranging the sensor at the end of the pipeline is simulated at x1=1m, x2=2m, …, x 14 =14m. The positioning error can be solved by using formula (2), and the finally obtained positioning error when the leakage hole is at different positions is shown in Table 3:

[0046] Table 3 Relationship between leakage hole position and positioning error when the sensor position is fixed

[0047]

[0048] Step 5: With the leak hole position fixed, change the sensor position and make numerical simulation, and calculate the corresponding positioning error according to the modified transient flow reflection positioning formula. Then the relationship between the sensor position and the positioning error is obtained, and several positions with smaller positioning error are selected as the preferred points of sensor arrangement. When the leak hole is at 6m, the positioning error of different sensor positions appears as shown in Figure 3 the case, and it is found that when the sensor is arranged at about 0.5m and 1.5m from the outlet, the positioning error is significantly reduced, so these two places are the preferred points of sensor arrangement. In view of this phenomenon, the position of the leak hole is changed, and the leak hole positions are changed to x5=5m, x6=6m, …, x 11 =11m respectively, and the positioning error is calculated respectively, and the relationship between the sensor arrangement position and the positioning error under different leak hole positions is shown in Figure 4 the figure. As can be seen from the figure, for the whole, the above two preferred points of sensor arrangement still hold.

[0049] Step 6: When the leak hole position is at 6m, change the number of sensor arrangement according to the preferred points of sensor arrangement in step 5, and obtain the relationship between the number of sensor arrangement and the positioning error, which is shown in Table 4:

[0050] Table 4 Relationship between the number of sensors and the positioning error when the leak hole position is fixed

[0051]

[0052] As can be seen from the above table, when the number of sensors increases to 3, increasing the number of sensors will not significantly improve the positioning accuracy, and in order to save cost, the number of sensors can be controlled at 2-3.

[0053] Further, the position of the leak hole is changed, and the relationship between the number of sensors and the positioning error when the leak occurs at different positions is shown in Table 5, and the sensor arrangement scheme in this table is the same as Table 4.

[0054] Table 5 Relationship between the number of sensors and the positioning error when the leak occurs at different positions

[0055]

[0056] As can be seen from the above table, when the leak hole is at different positions, scheme 2, i.e. 2-sensor positioning, has a significant reduction in positioning error compared to single-sensor positioning, while if scheme 3, i.e. 3-sensor positioning, is used, the positioning error is not significantly reduced, and the cost is greatly increased.

[0057] The application proposes a double sensor arrangement method for arranging sensors at 1.5 m from a pipeline outlet and at 0.5 m from the pipeline outlet to carry out leakage hole positioning, which greatly reduces the positioning error, and the positioning error is less than 2% except that the leakage occurs near 1 m and 2 m from the pipeline inlet, and the improvement effect is obvious.

[0058] The above is the ideal embodiment according to the method of the application. Through the above description, relevant personnel can make various changes and modifications without deviating from the scope of the method of the application. The technical scope of the application is not limited to the content in the specification, and the technical scope of the method of the application must be determined according to the scope of claims.

Claims

1. A multi-sensor arrangement method for pipeline leak detection, characterized by, The multi-sensor arrangement method first establishes a positioning equation of the leakage hole position according to the basic principle of the transient flow reflection method, then changes the position of the sensor to determine the preferred point of the sensor arrangement, and finally changes the arrangement number of the sensor according to the preferred point of the sensor arrangement obtained, and further determines the optimal sensor arrangement number; the specific steps are as follows: Firstly, the positioning equation of the leakage hole is established according to the basic principle of the transient flow reflection method; According to the basic principle of the transient flow reflection method, the leakage hole positioning formula based on the traditional transient flow reflection method is improved, and the arrangement position and arrangement number of the sensor are changed to make it suitable for the leakage hole positioning of the multi-sensor; The corrected leakage hole positioning equation is: (1)； wherein: x is the length of the leak hole from the pipe inlet; v is the propagation speed of the pressure wave in the pipe; n is the number of sensors; L is the total length of the pipe; l i is the distance of the sensor from the pipe inlet; i = 1, 2,..., n; t xi is the time for the pressure wave generated after the valve is closed to be transmitted from the pipe outlet to the leak hole location, and then reflected from the leak hole to the i (i = 1, 2,..., n)th sensor. Therefore, the positioning error of the leakage hole is calculated by the following formula: (2) ； wherein: x * is the actual measured position of the pipe leak hole, i.e. the length of the leak hole from the outlet of the pipe; and ε is the positioning error of the leak hole. Secondly, a plurality of three-dimensional models of the pipeline with the leakage hole in different positions are established in the three-dimensional modeling software, and the geometric model file is output; Thirdly, the geometric model established in the second step is imported into the Fluent module of the ANSYS Workbench software platform to simulate the pipeline leakage, and the boundary conditions including the fluid related parameters and the leakage hole position are set; Fourthly, in the case that the leakage hole is located between the inlet and outlet of the pipeline and the sensor is arranged at the outlet of the pipeline, the leakage hole position is calculated according to the traditional transient flow reflection method positioning formula, and compared with the actual pipeline leakage hole position to obtain the corresponding positioning error; Fifthly, in the case that the leakage hole position is fixed, the sensor position is changed, the leakage hole position is calculated according to the corrected transient flow reflection method positioning formula, and compared with the actual pipeline leakage hole position to obtain the relationship between the sensor position and the positioning error, and a plurality of positions with small positioning error are selected as the preferred points of the sensor arrangement; Sixthly, after the preferred points of the sensor arrangement are determined, the number of the arranged sensors is changed, the positioning error of the leakage hole is calculated according to the corrected transient flow reflection method positioning equation, the relationship between the number of the sensors and the positioning error is studied in the case that the leakage hole position is fixed, and a plurality of preferred arrangement numbers of the sensors are obtained; The position of the leakage hole is changed, the relationship between the number of the sensors and the positioning error is explored when the leakage occurs in different positions, and compared with the positioning accuracy of the traditional transient flow reflection method to determine the optimal arrangement number of the sensors.

2. A multi-sensor arrangement method for pipeline leak detection according to claim 1, characterized in that, The third step, according to the actual use, the simulation of the pipe related parameters including: fluid density (kg / m 3 ), fluid elastic modulus (Pa), fluid poisson's ratio, fluid density variation range, import pressure (KPa), export pressure (KPa), time step (s) and turbulence intensity.

3. A multi-sensor arrangement method for pipeline leak detection according to claim 1, characterized in that, In the third step, the solver based on the turbulent flow model is established in the Fluent module, the grid is divided, the boundary conditions are set, the numerical simulation is performed, and the pressure distribution and flow field distribution of the pipeline are obtained; when the grid division of the pipeline model with the leakage hole is performed, it is necessary to pay attention to the grid encryption at the leakage hole.

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