An experimental device and test method for simulating leakage diffusion of a natural gas pipeline

Abstract

The application relates to an experimental device and a testing method for simulating natural gas pipeline leakage diffusion, and belongs to the technical field of natural gas pipeline leakage diffusion. The experimental device for simulating natural gas pipeline leakage diffusion comprises a natural gas cylinder, a methane concentration sensor, a soil pit, a simulation pipeline and an annular gradient support, the gas outlet of the natural gas cylinder is connected with one end of a pressure-resistant main hose through a first pressure-resistant branch hose, the other end of the pressure-resistant main hose is connected with a pipeline, the pipeline is provided with a simulation pipeline, the top of the simulation pipeline is provided with a leakage hole, a first electromagnetic valve is arranged in the leakage hole, and a plurality of methane concentration sensors are arranged above the simulation pipeline in a spaced mode. Beneficial effects: the sensors are arranged in the space near the top of the leakage hole in the soil and above the ground, a leakage monitoring area is formed above the leakage hole, a three-dimensional concentration field near the leakage hole under specific conditions can be obtained, and the diffusion law of natural gas from the soil to the atmosphere after the leakage of the buried natural gas pipeline can be understood.

Description

Technical Field

[0001] This invention belongs to the field of natural gas pipeline leakage and diffusion technology, specifically relating to an experimental apparatus and testing method for simulating natural gas pipeline leakage and diffusion. Background Technology

[0002] With the increasing consumption of natural gas each year, the spatial distribution of natural gas pipelines is becoming increasingly dense. Due to years of disrepair, underground pipelines are prone to accidents, and various other factors contribute to frequent natural gas pipeline leaks. Leaks in buried pipelines are particularly difficult to detect due to their concealment. Given sufficient time, leaked natural gas can easily spread through the soil to nearby spaces and explode. Therefore, effectively preventing the spread of leaked buried natural gas pipelines through the soil and the resulting threat to adjacent spaces has become an urgent problem to be solved.

[0003] Patent CN110056769A discloses a simulation experimental device and testing method for leaks in buried high-sulfur natural gas gathering and transmission pipelines. By varying factors such as burial depth, leakage pressure, and leakage orifice diameter, it simulates and tests the throttling and cooling effect during a leak in a buried high-sulfur natural gas gathering and transmission pipeline, providing field test data for the integration and layout optimization of distributed fiber optic leak monitoring systems for buried natural gas gathering and transmission pipelines. This patent primarily measures the temperature of the throttling and cooling effect during the pipeline leak process, but does not quantitatively detect the concentration of natural gas at the leak location.

[0004] Patent CN112733312A discloses a natural gas gathering and transmission pipeline leakage simulation device and method. Several sensor units are arranged in a specific manner in the space near the leak hole to form a leakage monitoring area. The sensor units can be selected from temperature sensors and / or concentration sensors according to testing needs, thereby monitoring the three-dimensional temperature field and / or toxic gas diffusion field near the leak hole, providing guidance for the selection of monitoring technology. This patent mainly performs quantitative detection of the leakage process of the gathering and transmission pipeline in the soil, but does not perform qualitative and quantitative detection of the process of leaked natural gas from the soil to the atmosphere. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an experimental apparatus for simulating the diffusion of natural gas pipeline leaks. By arranging sensors in the space above the leak point of the simulated pipeline, both within the soil and near the surface, a leak monitoring area is formed above the leak point. This allows the acquisition of a three-dimensional concentration field near the leak point under specific conditions, thereby enabling the study and understanding of the diffusion pattern of natural gas from the soil to the atmosphere after a buried natural gas pipeline leak.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: The experimental device for simulating the leakage and diffusion of natural gas pipelines includes: a natural gas cylinder, a methane concentration sensor, a pit, a simulated pipeline, and an annular gradient support. The outlet of the natural gas cylinder is connected to one end of a pressure-resistant main hose through a first pressure-resistant branch hose, and the other end is connected to the pipeline. The simulated pipeline is provided on the pipeline, and a leak port is provided at the top of the simulated pipeline. A first solenoid valve is installed in the leak port. The simulated pipeline is set in the pit. Multiple methane concentration sensors are arranged at intervals above the simulated pipeline. An annular gradient support is provided on the ground vertically above the simulated pipeline. Multiple methane concentration sensors are arranged at a gradient on the annular gradient support. The methane concentration sensors and the first solenoid valve are respectively connected to a computer through waterproof cables.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, it also includes a leak detection mechanism, which is a nitrogen cylinder, and the nitrogen cylinder is connected to the pressure-resistant main hose through a second pressure-resistant branch hose.

[0009] The beneficial effect of adopting the above-mentioned further solution is that it can expel gases from the soil and ensure the accuracy of the detection data.

[0010] Furthermore, the pressure-resistant main hose is equipped with a pressure reducing valve and a gas flow meter.

[0011] The beneficial effects of adopting the above-mentioned further solution are: the pressure reducing valve can adjust the gas pressure, and the gas flow meter can detect the gas flow rate.

[0012] Furthermore, a second solenoid valve is provided on the left end of the pipe near the simulated pipe, and a third solenoid valve is provided on the right end of the pipe near the simulated pipe. The second solenoid valve and the third solenoid valve are electrically connected to the computer.

[0013] The beneficial effect of adopting the above-mentioned further scheme is that it can control the opening and closing of the pipeline and the simulated pipeline inlet and outlet.

[0014] Furthermore, a pressure sensor is installed inside the simulated pipeline.

[0015] The advantage of adopting the above-mentioned further solution is that it enables the detection of pressure within the simulated pipeline.

[0016] The second objective of this invention is to provide a method for detecting natural gas pipelines using the experimental apparatus described above for simulating the leakage and diffusion of natural gas pipelines, comprising the following steps:

[0017] Step 1: Connect all components;

[0018] Step 2: Close the second and third solenoid valves and the first solenoid valve, connect the nitrogen cylinders to each other, and perform a leak detection.

[0019] Step 3: Without leaking air, place the simulated pipe in the pit and completely cover it with soil to ensure that the simulated pipe is set horizontally;

[0020] Step 4: Place methane concentration sensors every 30cm of soil above the simulated pipeline, then install multiple methane concentration sensors on the annular gradient bracket on the ground, and open the first solenoid valve to open the leak outlet.

[0021] Step 5: By connecting the nitrogen cylinder to the simulated pipeline, the gas in the soil is expelled. Then, the nitrogen cylinder is disconnected, the natural gas cylinder is connected to the simulated pipeline, and the first solenoid valve is closed to shut off the leak.

[0022] Step 6: Turn on the methane concentration sensor, pressure sensor, second solenoid valve, third solenoid valve and first solenoid valve, adjust the outlet pressure of the pressure reducing valve, and record the detection data of the methane concentration sensor through the computer.

[0023] Beneficial effects: By arranging sensors in the soil and near the surface above the leak point of a simulated pipeline, a leak monitoring area is formed above the leak hole. This allows for the acquisition of a three-dimensional concentration field near the leak hole under specific conditions, thus enabling the study and understanding of the diffusion pattern of natural gas from the soil to the atmosphere after a leak in a buried natural gas pipeline. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] The attached diagram lists the components represented by each number as follows:

[0026] 1. Nitrogen cylinder; 2. Natural gas cylinder; 3. Pressure-resistant main hose; 4. Pressure reducing valve; 5. Gas flow meter; 6. Pipeline; 7. Methane concentration sensor; 8. Second solenoid valve; 9. Third solenoid valve; 10. First solenoid valve; 11. Leakage port; 12. Waterproof cable; 13. First pressure-resistant branch hose; 14. Pit; 15. Simulated pipeline; 16. Annular gradient support; 17. Computer; 18. Pressure sensor; 19. Second pressure-resistant branch hose. Detailed Implementation

[0027] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1

[0029] like Figure 1As shown, this embodiment provides an experimental apparatus for simulating the leakage and diffusion of natural gas pipelines, including: a natural gas cylinder 2, a methane concentration sensor 7, a pit 14, a simulated pipeline 15, and an annular gradient support 16. The outlet of the natural gas cylinder 2 is connected to one end of a pressure-resistant main hose 3 via a first pressure-resistant branch hose 13, and the other end is connected to a pipeline 6. The simulated pipeline 15 is provided on the pipeline 6. A leak port 11 is provided at the top of the simulated pipeline 15. A first solenoid valve 10 is installed in the leak port 11. The simulated pipeline 15 is set in the pit 14. Multiple methane concentration sensors 7 are arranged at intervals above the simulated pipeline 15. An annular gradient support 16 is provided on the ground vertically above the simulated pipeline 15. Multiple methane concentration sensors 7 are arranged at a gradient on the annular gradient support 16. The methane concentration sensors 7 and the first solenoid valve 10 are respectively connected to a computer 17 via waterproof cables 12.

[0030] The experimental setup uses a simulated pipe 15 with a concentration sensor 7 installed above it to simulate the real three-dimensional methane concentration gradient near the leak point 11. The methane concentration sensor 7 is connected to a computer 17 via a waterproof cable 12, which is waterproofed to allow it to operate normally for extended periods buried in outdoor soil and transmit data to the computer 17 in real time via the waterproof shielded cable. The gas path of the simulated pipe 15 extends to the ground via an L-shaped pipe 6. The horizontal section of the pipe is threaded to the simulated pipe 15 with Teflon tape wrapped around it, minimizing the impact of the pipe on the natural gas leak flow field. Based on the analysis of flow characteristics, the stability of the flow in a pipe generally requires a diameter of more than 50 times the pipe diameter. Considering the relatively high flow velocity inside the pipe during the leak, high demands are placed on the dynamic response speed of the experimental testing instruments. Therefore, an experimental pipe section with a length of 4m, which is 120 times the pipe diameter, is used, which is sufficient to meet the stability requirements of the flow. The L-shaped pipe is mainly for the horizontal section of pipe 6 to connect to the simulated pipe 15, and the vertical section of pipe 6 to protrude above the ground to ensure safety when releasing residual gas inside the simulated pipe 15.

[0031] The methane concentration sensor 7 employs an infrared gas sensor, which has the advantage of utilizing the absorption characteristics of gases to specific infrared spectra for concentration measurement. It is oxygen-independent and free from sensor poisoning. It features both analog and digital signal output interfaces, directly outputting linearized and temperature-compensated gas concentration signals. The sensor's range is 0–100% VOL, and its operating temperature is -40–+70℃. The methane concentration sensor housing is explosion-proof; the cable interface is waterproof to prevent damage from flammable gas explosions and moisture in the soil. The waterproof cable 12 both powers the methane concentration sensor 7 and transmits its detection data back to the sensor.

[0032] The methane concentration sensor 7 is positioned centered on the leak outlet 11. Concentration sensors 7 are arranged near the leak outlet 11 to detect the diffusion of natural gas in the soil and atmosphere. Based on leakage models such as the point-source spherical unsteady-state model and the unsteady-state nonlinear Darcy flow model of natural gas in soil, the diffusion range of natural gas in the soil gradually increases from deep to shallow according to the burial depth. Therefore, according to the theoretical model, several layers of concentration sensors are arranged, with the spacing between sensors gradually increasing from deep to shallow. When natural gas diffuses from the soil into the atmosphere, it will form an approximately circular concentration range at the surface. Therefore, several layers of sensors are arranged at and above the surface to measure the concentration of natural gas. The distance between each layer of sensors should not be too close, as this will affect the diffusion flow field of natural gas and cause deviations in the measurement data.

[0033] A gas pressure sensor 18 is welded to the inner wall of the simulated pipe 15. This allows for real-time measurement of the gas pressure inside the buffer cylinder and connection to a computer 17 on the ground via a waterproof cable 12 outside the simulated pipe 15, without affecting the sealing of the simulated pipe 15. The interface between the gas pressure sensor 18 and the waterproof cable 12 is waterproofed. The waterproof cable 12 is run in parallel with the pipe 6, facilitating construction and preventing rainwater and moisture in the soil from affecting the measurement performance of the waterproof gas pressure sensor 18. Before each experiment, nitrogen is used to disperse the methane gas adsorbed in the soil pores, further reducing the influence of other gases on the experiment. A soil sampler removes soil of equal volume to the methane concentration sensor 7 and places it inside, ensuring the methane concentration sensor 7 is placed vertically. By installing two L-shaped pipes 6 at both ends of the simulated pipe 15 and controlling the leakage at the leak port 11 using a first solenoid valve 10, leakage can be prevented. Before the leak experiment officially begins, the simulated pipeline 15 is filled with natural gas. After opening the leak port 11 with the first solenoid valve 10, the actual situation of the initial stage of the leak can be better simulated. When conducting the experiment simulating natural gas leakage in the soil, gas path leak detection should be performed to check whether the gas path is leaking, so as to ensure that the leakage source of natural gas in the soil is from the leak port 11. The compressed nitrogen cylinder 1, pressure reducing valve 4, gas flow meter 5, pressure-resistant main hose 3, pipeline 6, and simulated pipeline 15 equipped with gas pressure sensor 18 and first solenoid valve 10 are connected in sequence. The pressure reducing valve 4 is opened, and nitrogen or air flows out of the compressed nitrogen cylinder 1, passes through the pressure reducing valve 4, gas flow meter 5, and pipeline 6 in sequence and enters the simulated pipeline 15. The outlet pressure of the pressure reducing valve is adjusted to about 0.1 MPa. After the gas flow of gas flow meter 5 basically reaches a steady state, if the difference in reading of gas pressure sensor 18 is less than 0.01 MPa, it is considered that there is no gas leakage in the gas path.

[0034] Gas pressure sensor 18, second solenoid valve 8, third solenoid valve 9, and first solenoid valve 10 are controlled and data cables 12, which are laid underground in parallel with the rigid pipe 6 and connected to the computer 17 on the ground. Simulated pipe 15 and several methane concentration sensors 7 are buried in the soil of the experimental site; part of pipe 6 and part of waterproof cable 12 are buried in the soil. Methane concentration sensors 7 installed on the ground surface are used to measure the concentration of leaked gas from the soil to the surface. Several layers of methane concentration sensors 7 installed in the atmosphere are used to measure the concentration of gas leaked from the soil into the atmosphere. The specifications of simulated pipe 15 meet the stability requirements of the flow, i.e., the length is more than 50 times the pipe diameter; in this experiment, a length of 4m and a diameter of [missing information] are selected. A 32mm simulated pipe is horizontally buried 0.9m underground. Leakage ports 11 with different orientations and diameters can be set at halfway along the length. In this experiment, there is one vertically upward-facing leakage port 11 with a diameter of 2mm. The diameter can be changed by the first solenoid valve 10. After one round of simulated leakage experiments, before the start of a new round of leakage experiments, the high-pressure nitrogen cylinder 1, the second pressure-resistant branch hose 19, the pressure reducing valve 4, the pressure-resistant main hose 3, the pipe 6, and the simulated pipe 15 are connected to form a gas channel. The leakage port 11 on the simulated pipe 15 is opened by the first solenoid valve 10. High-concentration methane gas is continuously injected into the simulated pipe 15 to disperse the methane gas adsorbed in the soil pores and soil particles, and then a new round of leakage experiments is carried out.

[0035] Example 2

[0036] An experimental setup for simulating the diffusion of natural gas pipeline leaks includes the following steps:

[0037] The first step is to dig an experimental pit 14 with a size of not less than 4m×4m×1m according to the experimental requirements, and level the bottom of the experimental pit.

[0038] The second step is to install the second solenoid valve 8, the third solenoid valve 9, the first solenoid valve 10 and the gas pressure sensor 18 on the simulated pipeline 15. After installation, the pressure-resistant main hose 3, the first pressure-resistant branch hose 13, the second pressure-resistant branch hose 19 and the pipe 6 are used to connect the simulated pipeline 15 to the nitrogen cylinder 1 and the natural gas cylinder 2.

[0039] The third step is to connect the computer 17 and the methane concentration sensor 7 via the waterproof cable 12 and put them into operation online.

[0040] Fourth step: Close the second solenoid valve 8 and the third solenoid valve 9 of the simulated pipeline 15, and at the same time close the first solenoid valve 10 of the leak port 11. Connect the second pressure-resistant branch hose 19 to the compressed nitrogen cylinder 1 and check whether the gas line is leaking. If it is leaking, the device should be repaired and adjusted.

[0041] Fifth step: Under the condition that the device is leak-proof, place the simulated pipe 15, which is equipped with the high-pressure second solenoid valve 8, the high-pressure third solenoid valve 9, the high-pressure first solenoid valve 10 and the gas pressure sensor 18, together with the pipe 6, at the bottom of the pit.

[0042] The sixth step is to crush the soil in the experimental site, sift out stones, plant roots and other debris, backfill the pit, and ensure that the simulated pipe and leak outlet are horizontal. After filling the pit 30cm, compact the soil with a rammer.

[0043] Step 7: When filling the pit 30cm, bury the methane concentration sensor 7. Use a soil sampler to remove soil of the same volume as the methane concentration sensor 7 and put the methane concentration sensor 7 in, while ensuring that the sensor is placed vertically.

[0044] Step 8: Using the annular gradient bracket 16, install the methane concentration sensor 7 on the ground surface directly above the pit 14 to detect the concentration of gas leaked into the atmosphere from the buried simulated pipeline 15.

[0045] Step 9: Complete the soil compaction and sensor placement for each layer, and prepare to start the experiment; connect compressed nitrogen cylinder 1, pressure reducing valve 4, gas flow meter 5, pressure-resistant main hose 3, second pressure-resistant branch hose 19, pressure-resistant hose 3, pipe 6, and simulated pipe 15, and open the high-pressure first solenoid valve 10 at the leak port 11 to expel the gas from the soil.

[0046] Step 10: Connect the natural gas cylinder 2 containing methane, pressure reducing valve 4, first pressure-resistant branch hose 13, gas flow meter 5, pressure-resistant main hose 3, pipeline 6, and simulated pipeline 15. Use the first solenoid valve 10 to close the leak 11 of simulated pipeline 15.

[0047] Step 11: Turn on methane concentration sensor 7, pressure sensor 18, high-pressure second solenoid valve 8 and high-pressure third solenoid valve 9. Use high-pressure first solenoid valve 10 to open the leak port 11 of the simulated pipeline 15. Adjust the pressure reducing valve 4 to adjust the outlet pressure and record it. The computer 17 continuously records the detection data of methane concentration sensor 7. After the methane concentration sensor detection data buried in the soil reaches a steady state, a round of simulated natural gas leakage in the soil is completed.

[0048] Step 12: After one round of simulated leakage experiments is completed and before the start of a new round of leakage experiments, connect the high-pressure nitrogen cylinder 1, the second pressure-resistant branch hose 19, the pressure reducing valve 4, the pressure-resistant main hose 3, the pipeline 6, and the simulated pipeline 15 to form a gas channel; use the first solenoid valve 10 to open the leak port 11 on the simulated pipeline 15, and continuously inject high-concentration methane gas into the simulated pipeline 15 to disperse the methane gas adsorbed in the soil pores and soil particles, and then conduct a new round of leakage experiments.

[0049] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An experimental apparatus for natural gas pipeline leak diffusion simulation, characterized in that, It comprises: A natural gas cylinder (2), a methane concentration sensor (7), a soil pit (14), an analog pipeline (15) and an annular gradient support (16), the gas outlet of the natural gas cylinder (2) is connected with one end of a pressure-resistant main hose (3) through a first pressure-resistant branch hose (13), and the other end is connected with a pipeline (6), the pipeline (6) is provided with the analog pipeline (15), the top of the analog pipeline (15) is provided with a leakage port (11), the leakage port (11) is provided with a first electromagnetic valve (10), the analog pipeline (15) is arranged in the soil pit (14), a plurality of methane concentration sensors (7) are arranged above the analog pipeline (15) at intervals, an annular gradient support (16) is arranged on the ground vertically above the analog pipeline (15), a plurality of methane concentration sensors (7) are arranged on the annular gradient support (16) in a gradient manner, and the methane concentration sensors (7) and the first electromagnetic valve (10) are connected with a computer (17) through waterproof cables (12) respectively; the plurality of methane concentration sensors (7) arranged in the soil pit (14) gradually increase from deep to shallow.

2. The experimental setup for natural gas pipeline leak diffusion simulation according to claim 1, characterized in that, It also comprises a gas leakage detection mechanism, which is a nitrogen cylinder (1), and the nitrogen cylinder (1) is connected with the pressure-resistant main hose (3) through a second pressure-resistant branch hose (19).

3. The experimental setup for natural gas pipeline leak diffusion simulation according to claim 2, characterized in that, The pressure-resistant main hose (3) is provided with a pressure reducing valve (4) and a gas flow meter (5).

4. The experimental setup for natural gas pipeline leak diffusion simulation according to claim 3, characterized in that, The pipeline (6) is provided with a second electromagnetic valve (8) near the left end of the analog pipeline (15), and a third electromagnetic valve (9) near the right end of the analog pipeline (15).

5. The experimental setup for natural gas pipeline leak diffusion simulation according to claim 4, characterized in that, The analog pipeline (15) is provided with a pressure sensor (18).

6. A test method for simulating natural gas pipeline leakage diffusion by using the experimental device for simulating natural gas pipeline leakage diffusion according to claim 5, comprising the following steps: Step 1: connect all parts; Step 2: close the second electromagnetic valve (8), the third electromagnetic valve (9) and the first electromagnetic valve (10), connect the nitrogen cylinder (1) with the nitrogen cylinder (1), and detect the gas leakage; Step 3: without gas leakage, place the analog pipeline (15) in the soil pit (14), and use soil to completely cover it to ensure that the analog pipeline (15) is arranged horizontally; Step 4: place a methane concentration sensor (7) above the analog pipeline (15) every 30 cm of filling soil, then install a plurality of methane concentration sensors (7) on the annular gradient support (16) on the ground, open the first electromagnetic valve (10) to open the leakage port (11); Step 5: connect the nitrogen cylinder (1) with the analog pipeline (15) to expel the gas in the soil, then disconnect the nitrogen cylinder (1), connect the natural gas cylinder (2) with the analog pipeline (15), and close the first electromagnetic valve (10) to close the leakage port (11). Step 6: Turn on the methane concentration sensor (7), the pressure sensor (18), the second solenoid valve (8), the third solenoid valve (9) and the first solenoid valve (10), adjust the outlet pressure of the pressure reducing valve (4), and record the detection data of the methane concentration sensor (7) through the computer (17).

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