Ignition and propagation test device under dynamic flow of low-concentration coal mine gas pipeline

Abstract

The invention relates to an ignition and propagation test device under dynamic flow of a low-concentration coal mine gas pipeline, and belongs to the technical field of coal mine gas conveying safety. The testing device comprises a coal mine gas high-pressure gas storage bottle, a switch valve, a pressure reducing valve, an air compressor, a gas conveying pipeline, a mass flow controller, an air inlet valve, a pipeline model, an emptying valve, a magnetic driving fan, a circulating pipeline, a honeycomb flow homogenizer, a pitot tube, an electrode needle, a narrow pulse generator, a high-voltage power supply, a high-voltage probe, a current probe, an oscillographic recorder and a schlieren instrument. And a high-speed camera and a computer. The device solves the problem that the flow working condition cannot be simulated in the prior art, the influence of different flow speeds, pressures and pressure relief conditions on gas ignition and flame propagation can be researched, and an experimental basis is provided for pipeline conveying safety. The method has the advantages that ignition energy quantification, flame propagation visualization and explosion venting characteristic analysis in the flowing state are achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal mine gas conveying safety, and particularly relates to a low-concentration coal mine gas pipeline dynamic flow ignition and propagation test device. BACKGROUND

[0002] Low-concentration coal mine gas (referring to gas with methane volume concentration greater than or equal to 3% and less than 30%) is a kind of unconventional gas resource rich in methane. Traditionally, low-concentration gas is often directly discharged due to poor economy and high utilization technology difficulty, which not only causes energy waste but also aggravates the greenhouse effect. Through direct combustion utilization technology, it can be converted into heat or electric energy, realizing "waste into treasure", reducing methane emission and providing clean energy to promote the green transformation of coal mines. However, methane and oxygen coexist in low-concentration coal mine gas, and the methane concentration is usually within the flammable limit range, making it have the characteristics of flammability and explosiveness. At present, such coal mine gas is generally transported by pipeline to power stations or boiler rooms for large-scale utilization. Pipeline transportation has the advantages of high efficiency, wide coverage and low cost. However, if the gas encounters static electricity, sparks or other fire sources during pipeline transportation, it is easy to cause fire and explosion accidents, resulting in serious property loss, personnel injury and even forced shutdown of coal mines. In recent years, there have been consecutive explosion accidents of extracted gas pipeline transportation in Shanxi, Chongqing and Henan, causing serious personnel injury and property loss. This safety hazard makes the safe transportation of low-concentration coal mine gas by pipeline a key bottleneck restricting its effective utilization. Therefore, the research on the accidental ignition and propagation of low-concentration coal mine gas in the pipeline under the condition of dynamic flow and the corresponding prevention methods can not only reveal the ignition and propagation characteristics and laws of low-concentration coal mine gas pipeline under dynamic flow, but also provide reliable experimental basis and technical guidance for preventing coal mine gas pipeline explosion accidents and realizing the safe transportation and utilization of coal mine gas.

[0003] At present, the experimental research on the ignition and propagation of low-concentration coal mine gas by pipeline at home and abroad mainly focuses on static pipeline environment and basic research on propagation law, and fails to reflect the gas flow dynamic working condition of actual coal mine gas pipeline transportation. In addition, the mechanism of the interaction between gas flow and flame propagation has not been revealed. Moreover, the research on the ignition energy of coal mine gas under flow state has not been carried out, and the relevant experimental data is very lacking. The present application is designed to carry out a variety of experimental schemes to study the ignition and propagation of low-concentration coal mine gas under dynamic flow of pipeline. SUMMARY

[0004] The purpose of the present application is to provide a low-concentration coal mine gas pipeline dynamic flow ignition and propagation test device. The device can carry out simulation experiment research on the ignition and propagation of low-concentration coal mine gas under flow state and its prevention methods and technology.

[0005] The technical solutions of the present application are as follows:

[0006] A low-concentration coal mine gas pipeline dynamic flow ignition and propagation test device comprises:

[0007] A gas pipeline transportation scene simulation system comprises a coal mine gas high-pressure storage cylinder, an on-off valve, a pressure reducing valve, a methane mass flow controller, an air compressor, an air mass flow controller, a gas conveying pipeline, an air inlet valve, a pipeline model, an emptying valve, a magnetic drive fan, a circulating pipeline, a honeycomb flow uniformizer, and a Pitot tube.

[0008] A minimum ignition energy measurement system comprises a high-voltage power supply, a narrow pulse generator, an electrode needle, a first high-voltage probe, a second high-voltage probe, a current probe, and an oscilloscope.

[0009] A high-speed schlieren photography system comprises a schlieren instrument, a high-speed camera, and a computer.

[0010] The pipeline model is connected with the circulating pipeline to form a closed loop, and the magnetic drive fan drives the circulation of the gas; the electrode needle is installed inside the pipeline model; the light path of the schlieren instrument passes through the quartz window of the pipeline model.

[0011] In the above technical solution, the circulating pipeline is coaxially connected with the pipeline model, the honeycomb flow uniformizer is arranged at the inlet of the pipeline model, and the probe length of the Pitot tube is adjustable to measure the flow rate at different positions.

[0012] In the above technical solution, the narrow pulse generator is connected with the computer through a USB interface, receives pulse width and frequency instructions, and controls the high-voltage power supply to output an adjustable voltage signal.

[0013] In the above technical solution, the first high-voltage probe and the second high-voltage probe are respectively connected with the lines at both ends of the electrode needle, and the current probe is connected in series in the electrode needle circuit, and the three are synchronously connected with the oscilloscope.

[0014] In the above technical solution, the schlieren instrument comprises a mercury lamp light source, a pinhole diaphragm, a first mirror, a first concave mirror, a second concave mirror, a second mirror, and a knife edge, light rays are focused on the knife edge after being reflected through the quartz window of the pipeline model, and the high-speed camera photographs the light spot cut by the knife edge.

[0015] In the above technical solution, the tip of the electrode needle is located in the field of view of the light path of the schlieren instrument passing through the quartz window.

[0016] In the above technical solution, a detachable pressure relief port structure is arranged on the pipeline model to study the influence of the pressure relief characteristics on the flame propagation.

[0017] In the technical scheme, the computer synchronously receives voltage / current data of the oscillograph and flame propagation images of the high-speed camera, and analyzes ignition energy and flow field characteristics.

[0018] In the technical scheme, the side of the pipeline model is provided with symmetrical quartz windows, and the schlieren instrument light path vertically passes through the window plane.

[0019] In the technical scheme, the circulating pipeline is made of pressure-resistant stainless steel, and the working pressure range is 0.1-1 MPa.

[0020] Beneficial effects:

[0021] The present application provides a kind of low concentration coal mine gas pipeline dynamic flow under the ignition and propagation test device of fire, can be more comprehensive real-time record to the development process of the behavior of coal mine gas flowing in pipeline, fire when spark and flame propagation etc., and can conveniently control experimental conditions.The present application can monitor the voltage and current data of the two ends of ignition electrode by high pressure probe and current probe, so as to obtain spark energy by calculation;The ignition process of electrode needle area can be photographed by high-speed schlieren camera system, which is used to determine whether ignition is successful and to photograph the propagation process of flame after ignition.The device has the characteristics of convenient operation and complete function, and has great significance for in-depth understanding of the ignition and propagation law of low concentration coal mine gas under pipeline dynamic flow.Using the device, research on coal mine gas pipeline transportation ignition and explosion can be carried out, the scene of low concentration coal mine gas being accidentally ignited during transportation can be simulated, and the ignition and flame propagation dynamics of low concentration coal mine gas in flow and scientific and effective control method are explored.

[0022] The present application is a kind of low concentration coal mine gas pipeline dynamic flow under the ignition and propagation test device of fire.The device can be used for: (1) studying the influence of different flow velocity, flow flux, flow pressure and other factors on the ignition characteristics and law of low concentration coal mine gas in pipeline, and further improving the ignition and explosion mechanism of low concentration coal mine gas flowing in pipeline;(2) studying the influence of pressure relief port characteristics, pressure relief mode and other factors on the flame propagation and pressure relief characteristics of low concentration coal mine gas in pipeline, and developing the explosion relief method and technology of low concentration coal mine gas in pipeline;(3) studying the influence of different pipeline conditions on the ignition, flame propagation and pressure relief law of low concentration coal mine gas;(4) realizing the visualization research of low concentration coal mine gas ignition, flame propagation and pressure relief process in pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0024] Figure 1 It is a low concentration coal mine gas pipeline dynamic flow under the structure diagram of the fire and propagation test device of the present application;

[0025] Figure 2 It is a pipeline model structure and schlieren system schematic diagram.

[0026] In the figure: 1 is a coal mine gas high-pressure gas cylinder, 2 is an on-off valve, 3 is a pressure reducing valve, 4 is a methane mass flow controller, 5 is an air compressor, 6 is an air mass flow controller, 7 is a gas pipeline, 8 is an air inlet valve, 9 is a pipeline model, 10 is an emptying valve, 11 is a magnetic drive fan, 12 is a circulating pipeline, 13 is a honeycomb flow straightener, 14 is a pitot tube, 15 is a high-voltage power supply, 16 is a narrow pulse generator, 17 is an electrode needle, 18 is a first high-voltage probe, 19 is a second high-voltage probe, 20 is a current probe, 21 is an oscilloscope recorder, 22 is a high-speed camera, 23 is a mercury lamp light source, 24 is a pinhole diaphragm, 25 is a first mirror, 26 is a first concave mirror, 27 is a second concave mirror, 28 is a second mirror, 29 is a knife edge, and 30 is a computer. DETAILED DESCRIPTION

[0027] The present application will be described in detail below in combination with the drawings and specific embodiments. However, the following embodiments are only limited to the explanation of the present application, and the protection scope of the present application should include the entire content of the claims, and through the description of the following embodiments, those skilled in the art can fully realize the entire content of the claims of the present application.

[0028] Embodiment:

[0029] A low concentration coal mine gas pipeline dynamic flow under the structure diagram of the fire and propagation test device of the present application, including a gas pipeline transportation scene simulation system, a low concentration coal mine gas minimum ignition energy measurement system, a high-speed schlieren camera system;

[0030] The gas pipeline transportation scene simulation system includes a coal mine gas high-pressure gas cylinder 1, an on-off valve 2, a pressure reducing valve 3, a methane mass flow controller 4, an air compressor 5, an air mass flow controller 6, a gas pipeline 7, an air inlet valve 8, a pipeline model 9, an emptying valve 10, a magnetic drive fan 11, a circulating pipeline 12, a honeycomb flow straightener 13, and a pitot tube 14.

[0031] The low concentration coal mine gas minimum ignition energy measurement system comprises a high voltage power supply 15, a narrow pulse generator 16, an electrode needle 17, a first high voltage probe 18, a second high voltage probe 19, a current probe 20 and an oscillograph 21.

[0032] The high-speed schlieren photographing system comprises a schlieren instrument, a high-speed camera 22 and a computer 30.

[0033] The coal mine gas high-pressure gas cylinder 1 provides the required concentration of gas for the experiment, and the air provided by the air compressor 5 is used to dilute the high-concentration gas to form low-concentration gas in consideration of safety; the on-off valve 2 is installed on the coal mine gas high-pressure gas cylinder 1 and is used to control the opening and closing of the coal mine gas high-pressure gas cylinder 1; the methane mass flow controller 4 and the air mass flow controller 6 are installed on the gas conveying pipeline 7 and are used to control and display the flow of gas and air; the pipeline model 9 is used to simulate the pipeline in the low-concentration coal mine gas conveying scene in reality; the pitot tube 14 is installed in the pipeline model 9 and is used to measure the flow rate of the gas in the pipeline; the high voltage power supply 15 is used to provide high voltage for the electrode needle 17; the electrode needle 17 is installed inside the pipeline model 9 and is used to conduct high voltage and generate an electric spark at the tip; the narrow pulse generator 16 is connected with the control interface of the high voltage power supply 15 and controls the voltage signal output by the high voltage power supply 15 by adjusting the pulse width and pulse frequency; the first high voltage probe 18 and the second high voltage probe 19 are used to measure the voltage signal in the circuit between the two electrodes when the electrode needle 17 generates a spark; the current probe 20 is used to measure the current signal in the circuit when the electrode needle 17 generates a spark; the oscillograph 21 is used to collect and record the current and voltage signals of the first high voltage probe 18, the second high voltage probe 19 and the current probe 20; the schlieren instrument comprises a mercury lamp light source 23, a pinhole diaphragm 24, a first reflector 25, a first concave mirror 26, a second concave mirror 27, a second reflector 28 and a knife edge 29; after the high-brightness light source generated by the schlieren optical system emits light, a point light source is formed through the small hole, the light is reflected by the first reflector 25, the reflected light is reflected by the first concave mirror 26 to form parallel light, the light passes through the quartz window on the pipeline model cavity and then irradiates the second concave mirror 27, the light reflected by the second concave mirror 27 irradiates the second reflector 28, the light reflected by the second reflector 28 is focused on the knife edge 29, the light cut by the knife edge 29 is photographed by the high-speed camera 22, and the image signal is transmitted to the computer 30. The high-speed camera 22 reflects the characteristics of gas ignition and flame propagation front by photographing the image of the flow field density change provided by the schlieren optical system.

[0034] Further, the specific structure of the test device is as follows: the pipeline model 9 and the circulating pipeline 12 model are connected to form a closed pipeline system; the magnetic force driven fan 11 drives the low concentration gas in the closed pipeline to flow, simulates the pipeline transportation of the coal mine gas; the pipeline is provided with an emptying valve 10, which facilitates the replacement of the air in the pipeline and the ventilation after the experiment to exhaust the experimental gas; the pitot tube 14 measures the gas flow rate in the pipeline, the probe length of the pitot tube 14 is changed to measure the gas flow rate at different positions; the schlieren optical system is generated by the parallel light of the point light source and the lens, and can pass through the side of the pipeline model 9 with a quartz window; the high-voltage power supply 15 is connected with the electrode needle 17 through a cable; the narrow pulse generator 16 is connected with the computer 30 through a cable, the output signal of the narrow pulse generator 16 is controlled by the computer software, further, the narrow pulse generator 16 is connected with the high-voltage power supply 15 through a cable, and the output voltage signal and the current signal of the high-voltage power supply 15 are adjusted; the high-voltage probe and the current probe 20 are connected with the oscillograph 21 through a cable; when the flame flow field density in the field of view of the quartz window is uneven, the parallel light will be deflected to different degrees when passing through, and is focused on the schlieren knife edge 29, so that the flame area with different density gradients can be recorded by the lens of the high-speed camera 22, so that the position of the flame propagation front and the flow field structure are displayed.

[0035] Further, the working process of the device is as follows:

[0036] Research on the minimum ignition energy of low concentration coal mine gas under the dynamic flow of the pipeline:

[0037] 1, open the switch valve 2 of the coal mine gas high pressure gas cylinder 1, adjust the pressure reducing valve 3 to reduce the gas output pressure, open the methane mass flow controller 4, manually set the required flow. Open the switch valve of the air compressor 5, open the air mass flow controller 6, manually set the required flow; 2, open the air inlet valve 8 of the pipeline model 9, and open the air exhaust valve 10 of the pipeline model 9, the gas and air mixture is introduced into the pipeline model 9 from the air inlet valve 8 at a stable flow rate, after a period of time, the air in the pipeline model 9 is replaced by the gas and air mixture, the air inlet valve 8 and the air exhaust valve 10 are closed, the methane mass flow controller 4 and the air mass flow controller 6 are closed, the magnetic drive fan 11 is opened, and after the gas flow rate in the pipeline model 9 is stable, the pitot tube 14 detects the gas flow rate data; 3, open the high voltage power supply 15, make the high voltage power supply 15 in standby state, open the computer 30, the computer 30 supplies power and instruction control to the narrow pulse generator 16 through the USB interface, debug the instruction software of the narrow pulse generator 16 on the computer 30, set the pulse parameters such as pulse width and frequency; 4, open the schlieren instrument mercury lamp light source 23, the light emitted by the schlieren instrument mercury lamp light source 23 becomes parallel light after passing through the pinhole diaphragm 24, the first reflecting mirror 25 and the first concave mirror 26, when passing through the quartz window on the side of the pipeline model 9, ensure that the tip area of the electrode needle 17 is in the schlieren shooting field of view, open the high-speed camera 22, set the resolution, shooting frame rate and exposure time parameters on the matching software; 5, manually start the high-speed camera 22 matching software to enter the shooting mode, further, manually click the send command of the narrow pulse generator 16 matching software, save the voltage data and current data recorded by the oscilloscope 21, replay and analyze the flow field image of the tip area of the electrode needle 17 recorded by the high-speed camera 22, calculate the ignition energy according to the discharge time, voltage data and current data record; 6, the experiment is over, close the magnetic drive fan 11, the switch valve 2 of the coal mine gas high pressure gas cylinder 1, the air compressor 5, the high-speed camera 22, the schlieren instrument mercury lamp light source 23, the narrow pulse generator 16, the high voltage power supply 15 and the oscilloscope 21.

[0038] Further, the working process of the device is as follows:

[0039] Research on low concentration coal mine gas flame propagation under pipeline dynamic flow:

[0040] 1, open the switch valve 2 of the coal mine gas high pressure gas cylinder 1, then adjust the pressure reducing valve 3 to reduce the gas output pressure, open the methane mass flow controller 4, manually set the required flow. Open the switch valve of the air compressor 5, open the air mass flow controller 6, manually set the required flow; 2, open the air inlet valve 8 of the pipeline model, at the same time open the emptying valve 10 of the pipeline model 9, the gas and air mixture is passed into the pipeline model 9 from the air inlet valve 8 at a stable flow rate, after a period of time, the air in the pipeline model 9 is completely replaced by the gas and air mixture, close the air inlet valve 8 and the emptying valve 10, close the methane mass flow controller 4 and the air mass flow controller 6, open the magnetic drive fan 11, after the gas flow rate in the pipeline model 9 is stable, record the gas flow rate data detected by the pitot tube 14; 3, open the high voltage power supply 15, make the high voltage power supply 15 in standby state, open the computer 30, the computer 30 supplies power and instruction control to the narrow pulse generator 16 through the USB interface, debug the instruction software of the narrow pulse generator 16, set the pulse parameters such as pulse width and frequency; 4, open the schlieren instrument mercury lamp light source 23, the light emitted becomes parallel light after passing through the pinhole diaphragm 24, the first reflecting mirror 25 and the first concave mirror 26, when passing through the quartz window on the side of the pipeline model 9, ensure that the tip area of the electrode needle 17 is in the schlieren shooting field of view, open the high-speed camera 22, set the resolution, shooting frame rate and exposure time parameters on the matching software; 5, manually start the high-speed camera 22 matching software to enter the shooting mode, further, manually click the send command of the narrow pulse generator 16 matching software, replay and analyze the flame propagation flow field image recorded by the high-speed camera 22; 6, after the experiment is completed, close the magnetic drive fan 11, the switch valve 2 of the coal mine gas high pressure gas cylinder 1, the air compressor 5, the high-speed camera 22, the mercury lamp light source 23, the narrow pulse generator 16, the high voltage power supply 15 and the oscilloscope recorder 21.

[0041] The above description is merely a specific implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-concentration coal-mine gas pipeline dynamic flow ignition and propagation test device, characterized in that, The whole experimental device comprises: Gas pipeline delivery scene simulation system: composed of coal mine gas high-pressure gas cylinder (1), on-off valve (2), pressure reducing valve (3), methane mass flow controller (4), air compressor (5), air mass flow controller (6), gas pipeline (7), inlet valve (8), pipeline model (9), emptying valve (10), magnetic drive fan (11), circulating pipeline (12), honeycomb flow straightener (13) and pitot tube (14); Minimum ignition energy measurement system: composed of high-voltage power supply (15), narrow pulse generator (16), electrode needle (17), first high-voltage probe (18), second high-voltage probe (19), current probe (20) and oscilloscope recorder (21); High-speed schlieren photography system: composed of schlieren instrument, high-speed camera (22) and computer (30); The pipeline model (9) is connected with the circulating pipeline (12) to form a closed loop, and the magnetic drive fan (11) drives the gas to circulate; the electrode needle (17) is installed inside the pipeline model (9); the light path of the schlieren instrument passes through the quartz window of the pipeline model (9).

2. The apparatus of claim 1, wherein, The circulating pipeline (12) is coaxially connected with the pipeline model (9), the honeycomb flow straightener (13) is arranged at the inlet of the pipeline model (9), and the probe length of the pitot tube (14) is adjustable to measure the flow rate at different positions.

3. The apparatus of claim 1, wherein, The narrow pulse generator (16) is connected with the computer (30) through a USB interface, receives pulse width and frequency instructions, and controls the high-voltage power supply (15) to output an adjustable voltage signal.

4. The apparatus of claim 1, wherein, The first high-voltage probe (18) and the second high-voltage probe (19) are respectively connected with the two ends of the electrode needle (17), and the current probe (20) is connected in series in the loop of the electrode needle (17), and the three are synchronously connected with the oscilloscope recorder (21).

5. The apparatus of claim 1, wherein, The schlieren instrument comprises a mercury lamp light source (23), a pinhole diaphragm (24), a first mirror (25), a first concave mirror (26), a second concave mirror (27), a second mirror (28) and a knife edge (29), light rays are focused on the knife edge (29) after being reflected through the quartz window of the pipeline model (9), and the high-speed camera (22) photographs the light spot cut by the knife edge (29).

6. The apparatus of claim 5, wherein, The tip of the electrode needle (17) is located in the field of view region where the light path of the schlieren instrument passes through the quartz window.

7. The apparatus of claim 1, wherein, A detachable pressure relief port structure is arranged on the pipeline model (9) to study the influence of pressure relief characteristics on flame propagation.

8. The apparatus of claim 1, wherein, The computer (30) synchronously receives the voltage / current data of the oscilloscope recorder (21) and the flame propagation image of the high-speed camera (22), and correlates and analyzes the ignition energy and the flow field characteristics.

9. The apparatus of claim 1, wherein, The side surface of the pipeline model (9) is provided with symmetrical quartz windows, and the light path of the schlieren instrument vertically passes through the window plane.

10. The apparatus of claim 1, wherein, The circulating pipeline (12) is made of pressure-resistant stainless steel, and the working pressure range is 0.1-1 MPa.

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