CN107402232B - Method for measuring dynamic explosion limit parameters of combustible gas - Google Patents
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Abstract
The invention belongs to the technical field of industrial safety, and provides a method for measuring dynamic explosion limit parameters of combustible gas, aiming at solving the problems that the parameters of dynamic explosion limit characteristics cannot be measured and the like. Calculating the flow velocity of the gas which can be filled in the blasting tube when the gas is simultaneously fed; pumping the experimental device into a vacuum state, opening a combustible gas source and an air source, and filling the mixed gas into the blasting tube within the expected time; continuously ventilating to keep the mixed gas in a flowing state in the pipeline; starting a high-voltage discharger for ignition, triggering a data acquisition recorder and a high-speed camera at the same time, acquiring explosion pressure parameters if the mixed gas is ignited, recording flame propagation of dynamic explosion of the mixed gas and reducing the concentration of combustible gas to carry out the next experiment by observing whether the mixed gas is ignited, and increasing the concentration of the combustible gas if the mixed gas is not ignited to carry out the next experiment; and cleaning the pipeline by using an air compressor. Mainly aims at the determination of dynamic explosion limit and other explosion characteristic parameters of industrial gas. The error is reduced; the research of combustible gas dynamic explosion is convenient to carry out.
Description
Technical Field
The invention belongs to the technical field of industrial safety, and particularly relates to a method for measuring dynamic explosion limit parameters of combustible gas, which can be directly used for experimental research methods for measuring characteristic parameters such as dynamic explosion limit of combustible gas in industrial production and transportation.
Background
In the prior art, research on combustible gas combustion explosion by colleges and universities and research institutes is basically carried out under a static condition, most of conventional static explosion experimental devices at home and abroad are improved by adopting a device mode proposed by the U.S. Ministry of mines H.F. Coward in 1952, and if the conventional static explosion experimental devices are structurally composed of a combustible gas supply system, an air intake system, an ignition system, a vacuum pumping system and an explosion tube, the test precision is high, but the visual effect is poor, no gas mixing system exists, the uniform mixing degree of combustible gas and air is just one of factors influencing the explosion parameters of the combustible gas, the experiment is carried out under the static condition and is not consistent with the dynamic condition of the combustible gas in actual production life, the conventional experimental test on combustible gas explosion usually adopts a partial pressure type air intake method, the explosion tube is pumped to a vacuum state, a certain volume of the combustible gas is introduced, and then the air is introduced to enable the explosion tube to be in a normal pressure state, so that the partial pressure type air intake method is limited only suitable for the static explosion experiment of the combustible gas. The test parameters of combustible gas explosion under static conditions have certain guiding significance on actual fire and explosion prevention work, but cannot be directly applied. The dynamic explosion of combustible gas can be researched, so that many problems of fire in modern industry can be solved, practical and reliable basis is provided for fireproof and explosion-proof work, the function conversion problem of gas explosion can be explored, and a road is opened up for researching the application of gas explosion flowing in a pipeline.
At present, the research on combustible gas combustion explosion in various colleges and universities and research institutes in China is limited only in the aspect of static explosion characteristic parameters, only national standards of the people's republic of China exist in China, GB/T12474-2008 ' method for determining explosion limit of combustible gas in air ', the standard specifies a method for determining the explosion limit of the combustible gas under the conditions of normal temperature and normal pressure, the used gas inlet means is a conventional partial pressure method, and the determined explosion limit is the explosion limit of the combustible gas under the static conditions. However, the determination of the dynamic explosion limit of combustible gases is still lacking in technical means. Therefore, an experimental method for measuring the dynamic explosion characteristics of combustible gas is urgently needed.
Disclosure of Invention
The invention provides a method for measuring dynamic explosion limit parameters of combustible gas, aiming at solving the problems that the research on the explosion characteristics of the combustible gas under the dynamic condition can not be realized at present, and particularly, the parameters of the dynamic explosion limit characteristics can not be measured.
The invention is realized by the following technical scheme: the method for measuring the dynamic explosion limit parameters of the combustible gas comprises the steps of measuring the dynamic explosion limit parameters of the combustible gas, measuring the dynamic explosion characteristic parameters of the combustible gas, and measuring the dynamic explosion limit parameters of the combustible gas, the minimum ignition energy, the maximum dynamic explosion pressure and the pressure rising rate of the combustible gas, the dynamic explosion flame propagation speed of the combustible gas and the microstructure of a flame front vibration surface; measuring a method for simultaneously introducing combustible gas and air; the specific determination method comprises the following steps:
(1) Calculating the flow rate required by the fact that the combustible gas and the air in different proportions can be filled with the blasting tube within 15-20s when the combustible gas and the air are simultaneously fed;
(2) Starting a high-voltage discharger, a data acquisition recorder and a high-speed camera;
(3) The explosion pipeline is vacuumized by a vacuum pump, and the pressure change in the pipeline is less than or equal to 1KPa within 5 minutes;
(4) Opening a combustible gas source and an air source, adjusting a flow meter according to the flow and the air inlet time of the combustible gas and the air calculated in the step (1), and filling the mixed gas of the combustible gas and the air in the air inlet time to the explosion tube;
(5) After the mixed gas is filled in the detonating tube, continuously introducing the two gases for 5-10s according to the flow of the combustible gas and the air calculated in the step (1) so as to keep the mixed gas in a flowing state in the pipeline;
(6) Starting an ignition electrode for ignition, triggering a data acquisition recorder and a high-speed camera at the same time, observing whether mixed gas is ignited or not through an observation window on a detonation tube, acquiring explosion pressure parameters in the detonation tube when the mixed gas is ignited, recording flame propagation of dynamic explosion of the mixed gas, reducing the concentration alpha of combustible gas in the mixed gas for next experiment, increasing the concentration alpha of the combustible gas in the mixed gas for next experiment, and testing the dynamic explosion limit of the combustible gas;
(7) Cleaning the pipeline by using an air compressor for at least 3 times, and continuing to perform the next experiment from the step (2);
wherein: and (2) calculating the flow rate in the step (1) according to the set measuring range of the gas flowmeter, the scale requirement of the gas flowmeter and the volume of the blasting tube. The vacuum degree of the explosion pipeline is-90.55 KPa.
In the step (6), the concentration alpha of the combustible gas in the mixed gas is that the upper limit of the static explosion limit of the combustible gas is not more than alpha and not more than the lower limit of the static explosion limit of the combustible gas; the mixed gas to be tested in the explosion tube is ignited by adopting an ignition electrode arranged in the pipeline and a high-voltage discharger; and triggering the acquisition of explosion characteristic parameter data while igniting the mixed gas to be detected in the blasting tube.
The specific data acquisition method comprises the following steps: the dynamic explosion limit of the combustible gas is that the ignition state of the mixed gas is observed through an observation window on the detonating tube, the data acquisition recorder records the explosion pressure parameter, and according to GB/T12474-2008 'method for determining the explosion limit of the combustible gas in the air', the calculation formula of the upper (lower) limit of the explosion of the combustible gas is as follows: maximum (small) concentration of combustible gas at which explosion occurs
And minimum (large) concentration at which no explosion occurs
Average value of (i), i.e.
The minimum ignition energy of the combustible gas dynamic explosion is determined by changing the ignition voltage of an electric spark generator; the maximum pressure of the dynamic explosion of the combustible gas is obtained by recording through a piezoelectric sensor and a data acquisition recorder, and the maximum pressure rising rate is obtained by calculating through the change of pressure and time recorded in the data recorder; shooting a dynamic explosion flame propagation process of the combustible gas by a high-speed camera to calculate the flame propagation speed; and observing and analyzing the microstructure of the flame front vibration surface of the combustible gas dynamic explosion by using a schlieren instrument.
The schlieren instrument is the schlieren instrument for current conventional detection.
The detection device based on the method for determining the dynamic explosion limit parameters of the combustible gas comprises an air inlet pipeline and an explosion pipeline which are connected through a communicating pipe, wherein the air inlet pipeline is formed by connecting an air source, a combustible air source and a vacuum pump to one side of a first gas mixer, and the other side of the first gas mixer is connected with a secondary gas mixer; a drying device and a gas flowmeter I are connected between the air source and the first gas mixer; a gas flowmeter II is connected between the combustible gas source and the first gas mixer; a flame arrester is connected between the first gas mixer and the second gas mixer; the explosion pipeline is formed by connecting an explosion tube with 2 observation windows on the side wall with a flame observation tube flange, an ignition electrode is arranged at the air inlet end of the explosion tube and is connected with a high-voltage discharger through a high-voltage wire, a vacuum pressure gauge is arranged between the air inlet of the explosion tube and the ignition electrode, 2 piezoelectric sensors are connected above the explosion tube, and the piezoelectric sensors are connected with a data acquisition recorder; and the bottom of the flame observation tube is provided with an explosion venting port.
The first gas mixer is a jet mixer based on a Venturi tube, the jet mixer is formed by sequentially connecting an air inlet pipe, a contraction pipe, a throat pipe and a diffusion pipe in the middle of 2 flanges I, the length of the air inlet pipe is 60mm, the length of the contraction pipe is 113.39mm, the contraction angle of the contraction pipe is 20 degrees, the length of the throat pipe is 20mm, the length of the diffusion pipe is 280.75mm, the diffusion angle of the diffusion pipe is 8 degrees, and the thicknesses of the air inlet pipe, the contraction pipe, the throat pipe and the diffusion pipe are 2mm;
the secondary gas mixer is a static mixer based on folded-face porous disks, the static mixer is a cylinder connected with a 2-end flange II, a plurality of groups of disks provided with through holes are arranged in the cylinder at intervals, and each group of disks are narrow-angle folded-face porous disks and wide-angle folded-face porous disks which are arranged at intervals; the narrow-angle folded-surface porous disc is characterized in that 9 chords are evenly distributed on the disc, the diameter perpendicular to the chords is divided into 10 equal parts, two ends of the diameter perpendicular to the chords on the disc are respectively provided with a round hole I with the radius of 2mm, the 9 chords are provided with folded surfaces with the angle of 90 degrees, strip-shaped through holes are symmetrically arranged on the left side and the right side of the intersecting line of the folded surfaces and the disc, the width of each strip-shaped through hole is 3mm, the distance between the outer side of each strip-shaped through hole and the periphery of the disc is 2.5mm, and the distance between the inner sides of the left strip-shaped through hole and the right strip-shaped through hole is 5mm; the wide-angle folding-surface porous disc is characterized in that 4 chords are evenly distributed on the disc, the diameter perpendicular to the chords is divided into 5 equal parts, two ends of the diameter perpendicular to the chords on the disc are respectively provided with a round hole II with the radius of 4mm, folding surfaces with the angle of 127 degrees are arranged on the 4 chords, a through hole with the middle communicated with the middle is arranged on an intersecting line of the folding surfaces and the disc, the width of the through hole is 2mm, and the distance between two ends of the through hole and the periphery of the disc is 3mm.
The distance between the vacuum pressure gauge and the air inlet of the blasting tube is 80mm, the distance between the ignition electrode and the air inlet of the blasting tube is 150mm, and the distance between the ignition electrodes is 2mm; the distances between the 2 piezoelectric sensors and the air inlet of the blasting tube are respectively 300mm and 850mm, and the distances between the 2 observation windows and the air inlet of the blasting tube are respectively 150mm and 800mm.
The length of the blasting tube is 1400mm, the inner diameter of the blasting tube is 60mm, the wall thickness of the blasting tube is 8mm, and the blasting tube is made of 304 stainless steel; the outer diameter of the flame observation tube is 90mm, the inner diameter of the flame observation tube is 60mm, the length of the flame observation tube is 1000mm, and the flame observation tube is made of organic glass; the communicating pipe is a 1/2 stainless steel pipe. The cylinder length is 700mm, and the internal diameter is 60mm, and the wall thickness is 15mm, and the disc diameter of narrow angle folded surface porous disc and wide angle folded surface porous disc is 60mm, and is 1mm thick. The thickness of the flange, the flange I and the flange II is 15mm.
The first observation window is opposite to the ignition electrode and is used for observing the discharge condition of the electrode, and the second observation window is used for observing whether the flame is spread to the right side after ignition; the two piezoelectric sensors are used for monitoring the explosion pressure of the front part and the rear part of the combustible gas under the condition of dynamic explosion, and an explosion pressure curve is displayed on a computer screen through a data acquisition recorder.
The device comprises an explosion tube, a flame observation tube, an ignition electrode, a vacuum pressure gauge, piezoelectric sensors, a data acquisition recorder, a high-voltage discharger and observation windows, wherein the ignition electrode is positioned on two sides of the explosion tube and connected with the high-voltage discharger; for the safety in the experimental process, the right side of the flame observation tube is provided with an explosion venting hole.
Compared with the prior art, the method is mainly used for measuring the dynamic explosion limit parameters of the combustible gas in the production and transportation processes of the industrial gas. The method can also be used for measuring the dynamic explosion characteristic parameters of the combustible gas in the production and transportation processes of the industrial gas, and carrying out measurement and experimental research work on the minimum ignition energy, the maximum dynamic explosion pressure and the maximum pressure rise rate of the combustible gas, the dynamic explosion flame propagation speed of the combustible gas and the microstructure of the dynamic explosion flame front vibration surface of the combustible gas.
(1) The method for simultaneously feeding two gases is adopted, the traditional two-step partial pressure gas feeding method is abandoned, and the flow meter is used for controlling the quantity of the two gases, so that the research on the dynamic explosion of the combustible gas is facilitated; (2) The secondary gas mixer can fully mix the combustible gas and the air, so that errors caused by nonuniform gas mixing to test data are reduced; (3) The explosion tube formed by connecting the explosion tube and the flame observation tube realizes the normal flow of the mixed gas of the combustible gas and the air in the pipeline on the premise of economic safety and uninterrupted air intake; (4) The flame observation tube made of organic glass is convenient for observing and shooting the flame propagation condition caused by the dynamic explosion of the combustible gas; and (5) the structure is simple, and the operation is convenient.
The invention uses the flowmeter to simultaneously feed the combustible gas and the air under normal temperature and normal pressure, fully mixes the combustible gas and the air by the secondary gas mixer, ignites and discharges by the high-voltage discharger under the condition of continuous gas feeding, measures factors such as explosion limit, minimum ignition energy, explosion pressure and the like of the combustible gas, and can shoot the propagation condition of flame and the microstructure of the flame front vibration surface under the dynamic explosion of the combustible gas by using the high-speed camera and the schlieren instrument.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention;
fig. 2 is a schematic structural diagram of a detection device of the method for determining the dynamic explosion limit characteristics of combustible gas according to the invention, wherein: 1-an air source; 2-a drying device; 3-gas flowmeter I; 4-a first gas mixer; 5-flame arrestors; 6-a secondary gas mixer; 7-vacuum pressure gauge; 8-a piezoelectric sensor; 9-data acquisition recorder; 10-burning and exploding the tube; 11-flame viewing tube; 12-a vacuum pump; 13-a combustible gas source; 14-gas flow meter II; 15-a high voltage discharger; 16-an ignition electrode; 17-an observation window; 18-venting the explosion port;
FIG. 3 is a schematic diagram of a first gas mixer, wherein: 4.1-flange I; 4.2-air inlet pipe; 4.3-shrink tube; 4.4-throat; 4.5-diffusion tube;
FIG. 4 is a schematic diagram of the structure of the secondary gas mixer, in which 6.1-flange II; 6.2-narrow angle folding surface porous disc; 6.3-wide angle folding surface porous disc; 6.4-cylinder;
FIG. 5 is a schematic view of a narrow angle folding porous disc structure, wherein: 6.21-strip through holes; 6.22-round hole I;
FIG. 6 is a schematic view of a wide angle folding porous disc structure, wherein: 6.31-round hole II; 6.32-through holes;
FIG. 7 is a schematic view of the structure of an explosive tube;
fig. 8 is a schematic diagram of the speed measurement of a high-speed camera.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings; it should be understood that the preferred embodiments are illustrative of the invention only and are not limiting upon the scope of the invention.
Fig. 1 is a schematic flow chart of a testing method provided in an embodiment of the present invention, as shown in the figure: the method for measuring the dynamic explosion limit parameters of the combustible gas comprises the steps of measuring the dynamic explosion limit parameters of the combustible gas, measuring the dynamic explosion characteristic parameters of the combustible gas, and measuring the dynamic explosion limit parameters of the combustible gas, the minimum ignition energy, the maximum dynamic explosion pressure and the pressure rising rate of the combustible gas, the dynamic explosion flame propagation speed of the combustible gas and the microstructure of a flame front vibration surface; the specific determination method comprises the following steps:
(1) Calculating the flow rate required by the fact that the combustible gas and the air in different proportions can be filled with the blasting tube within 15-20s when the combustible gas and the air are simultaneously fed;
(2) Starting an electric spark generator, a data acquisition recorder and a high-speed camera;
(3) The explosion pipeline is vacuumized by a vacuum pump, and the pressure change in the pipeline is less than or equal to 1KPa within 5 minutes;
(4) Opening a combustible gas source and an air source, adjusting a flowmeter according to the flow and the air inlet time of the combustible gas and the air calculated in the step (1), and filling a mixed gas of the combustible gas and the air in the air inlet time to a detonating tube;
(5) After the mixed gas is filled in the detonating tube, continuously introducing the two gases for 5-10s according to the flow of the combustible gas and the air calculated in the step (1) so as to keep the mixed gas in a flowing state in the pipeline;
(6) Starting an ignition electrode for ignition, triggering a data acquisition recorder and a high-speed camera at the same time, observing whether the mixed gas is ignited or not through an observation window on a detonation tube, acquiring explosion pressure parameters in the detonation tube if the mixed gas is ignited, recording flame propagation of dynamic explosion of the mixed gas, reducing the concentration alpha of the combustible gas in the mixed gas for next experiment, and increasing the concentration alpha of the combustible gas in the mixed gas for next experiment if the mixed gas is not ignited, so as to test the dynamic explosion limit of the combustible gas;
taking methane as an example, when the dynamic explosion lower limit of methane is detected, the concentration of methane is tested for the first time and is increased by 0.5% if no explosion occurs, methane with the concentration of 5.3% is tested if methane with the concentration of 5.5% explodes, methane with the concentration of 5.2% is tested if methane with the concentration of 5.3% explodes, methane with the concentration of 5.2% does not explode in the first test and is continuously tested for 4 times, if methane with the concentration of 5.2% does not explode in the 5 times, the experiment is ended, and the experiment result is recorded; if the methane with the concentration of 5.3% does not explode, testing the methane with the concentration of 5.4%, if the methane does not explode, continuously testing for 4 times, if the methane with the concentration of 5.4% does not explode for 5 times, ending the test, and recording the test result; if the methane with the concentration of 5.5% does not explode, the test method is the same as the above to continue the test;
(7) Cleaning the pipeline by using an air compressor for at least 3 times, and continuing to perform the next experiment from the step (2);
wherein: and (2) calculating the flow rate in the step (1) mainly according to the set measuring ranges of different gas flowmeters, the scale requirements of the gas flowmeters and the volume of the detonating tube of 4L. To ensure the accuracy of the gas inlet, the flow rate of the gas is in accordance with the calibration requirements of the flowmeter, and table 1 lists the flow rates of two combustible gases at different ratios.
Table 1: flow rates of two combustible gases at different ratios
The vacuum degree of the explosion tube is atmospheric pressure according to the geographical position of the laboratory, and the vacuum degree of the pipeline is-90.55 KPa because a vacuum pressure gauge is used.
In the step (6), the variation range of the concentration alpha of the combustible gas in the mixed gas is mainly determined on the basis of the static explosion limit of the combustible gas, and is that the upper limit of the static explosion limit of the combustible gas is less than or equal to alpha and less than or equal to the lower limit of the static explosion limit of the combustible gas; for example, the methane concentration may vary from 5% to 15% and the hydrogen concentration may vary from 4% to 75.6%. Ignition of the mixed gas to be detected in the explosion tube is realized by adopting an ignition electrode arranged in the pipeline and a high-voltage discharger; and triggering the acquisition of explosion characteristic parameter data while igniting the mixed gas to be detected in the blasting tube.
The specific data acquisition method comprises the following steps: the dynamic explosion limit of the combustible gas is that the ignition state of the mixed gas is observed through an observation window on the detonating tube, the data acquisition recorder records the explosion pressure parameter, and according to GB/T12474-2008 'method for determining the explosion limit of the combustible gas in the air', the calculation formula of the upper (lower) limit of the explosion of the combustible gas is as follows: maximum (small) concentration of combustible gas at which explosion occurs
And minimum (large) concentration at which no explosion occurs
Average value of (i), i.e.
Calculating combustible gas dynamic explosionA limit; the minimum ignition energy of the dynamic explosion of the combustible gas is obtained by adjusting the discharge voltage of an electric spark generator and increasing or decreasing the ignition energy for igniting the mixed gas, so as to determine the minimum ignition energy required by the explosion of the combustible gas with different concentrations, the maximum pressure of the dynamic explosion of the combustible gas is obtained by recording through a piezoelectric sensor and a data acquisition recorder, and the pressure rising rate is obtained by calculating through the pressure recorded in the data recorder and the change of time; shooting a dynamic explosion flame propagation process of the combustible gas by a high-speed camera to calculate the flame propagation speed; and observing and analyzing the microstructure of the flame front vibration surface of the combustible gas dynamic explosion by adopting a conventional schlieren instrument.
As shown in fig. 2, the detection device based on the method for determining the dynamic explosion limit characteristics of combustible gas includes an air inlet pipeline and an explosion pipeline which are connected by a communicating pipe, wherein the air inlet pipeline is formed by connecting an air source 1, a combustible air source 13 and a vacuum pump 12 to one side of a first gas mixer 4, and connecting the other side of the first gas mixer with a secondary gas mixer 6; a drying device 2 and a gas flowmeter I3 are connected between the air source 1 and the first gas mixer 4; a gas flowmeter II 14 is connected between the combustible gas source 13 and the first gas mixer 4; a flame arrester 5 is connected between the first gas mixer 4 and the second gas mixer 6; the explosion pipeline is characterized in that an explosion pipe 10 with 2 observation windows 17 in the side wall is in flange connection with a flame observation pipe 11, an ignition electrode 16 is arranged at the air inlet end of the explosion pipe 10, the ignition electrode 16 is connected with a high-voltage discharger 15 through a high-voltage wire, a vacuum pressure gauge 7 is arranged between the air inlet of the explosion pipe 10 and the ignition electrode 16, 2 piezoelectric sensors 8 are connected above the explosion pipe 10, and the piezoelectric sensors 8 are connected with a data acquisition recorder 9; the bottom of the flame observation tube 11 is provided with an explosion venting port 18.
As shown in fig. 3, the first gas mixer is a jet mixer based on a venturi tube, the jet mixer is formed by sequentially connecting an air inlet pipe 4.2, a contraction pipe 4.3, a throat pipe 4.4 and a diffusion pipe 4.5 in the middle of 2 flanges I4.1, the air inlet pipe is 60mm long, the contraction pipe is 113.39mm long, the contraction angle of the contraction pipe is 20 degrees, the throat pipe is 20mm long, the diffusion pipe is 280.75mm long, the diffusion angle of the diffusion pipe is 8 degrees, and the thicknesses of the air inlet pipe, the contraction pipe, the throat pipe and the diffusion pipe are 2mm;
as shown in fig. 4, the secondary gas mixer is a static mixer based on a folded porous disc, the static mixer is a 2-end flange II 6.1 connected cylinder 6.4, a plurality of groups of discs provided with through holes are installed in the cylinder 6.4 at intervals, and each group of discs are a narrow-angle folded porous disc 6.2 and a wide-angle folded porous disc 6.3 at intervals; as shown in fig. 5, the narrow-angle folding-surface porous disc 6.2 is formed by evenly distributing 9 chords on the disc, dividing the diameter perpendicular to the chords into 10 equal parts, arranging round holes I6.22,9 with the radius of 2mm at two ends of the diameter perpendicular to the chords on the disc, arranging folding surfaces with the angle of 90 degrees on the chords, symmetrically arranging strip-shaped through holes 6.21 on the intersecting line of the folding surfaces and the disc at left and right sides, wherein the width of each strip-shaped through hole 6.21 is 3mm, the distance between the outer side of each strip-shaped through hole and the periphery of the disc is 2.5mm, and the distance between the inner sides of the left strip-shaped through hole and the right strip-shaped through hole is 5mm; as shown in FIG. 6, the wide-angle folding-surface porous disc 6.3 is a disc with 4 chords evenly distributed thereon, the diameter perpendicular to the chords is divided into 5 equal parts, two ends of the diameter perpendicular to the chords on the disc are respectively provided with a round hole II6.31 with the radius of 4mm, the 4 chords are provided with folding surfaces with the angle of 127 degrees, the intersecting line of the folding surfaces and the disc is provided with a through hole 6.32 with the middle communicated, the width of the through hole is 2mm, and the distance between the two ends of the through hole and the periphery of the disc is 3mm.
The distance between the vacuum pressure gauge and the air inlet of the blasting tube is 80mm, the distance between the ignition electrode and the air inlet of the blasting tube is 150mm, and the distance between the ignition electrodes is 2mm; the distances between the 2 piezoelectric sensors and the air inlet of the blasting tube are respectively 300mm and 850mm, and the distances between the 2 observation windows and the air inlet of the blasting tube are respectively 150mm and 800mm.
The length of the blasting tube is 1400mm, the inner diameter of the blasting tube is 60mm, the wall thickness of the blasting tube is 8mm, and the blasting tube is made of 304 stainless steel; the outer diameter of the flame observation tube is 90mm, the inner diameter of the flame observation tube is 60mm, the length of the flame observation tube is 1000mm, and the flame observation tube is made of organic glass; the communicating pipe is a 1/2 stainless steel pipe. The cylinder length is 700mm, and the internal diameter is 60mm, and the wall thickness is 15mm, and the disc diameter of narrow angle folded surface porous disc and wide angle folded surface porous disc is 60mm, and is 1mm thick. The thickness of the flange, the flange I and the flange II is 15mm.
The first observation window is opposite to the ignition electrode and is used for observing the discharge condition of the electrode, and the second observation window is used for observing whether the flame is spread to the right side after ignition; the two piezoelectric sensors are used for monitoring the explosion pressure of the front part and the rear part of the combustible gas under the condition of dynamic explosion, and the explosion pressure curve is displayed on a computer screen through a data acquisition recorder.
The device comprises an explosion tube, flame observation tubes, ignition electrodes, a vacuum pressure gauge, piezoelectric sensors, a data acquisition recorder, a high-voltage discharger and observation windows, wherein the explosion tube consists of the ignition electrodes, the high-voltage discharger and the observation windows; for the safety in the experimental process, the right side of the flame observation tube is provided with an explosion venting hole.
The length of the combustion and explosion tube is 1400mm, the inner diameter is 60mm, the volume of the combustion and explosion tube is 30 multiplied by pi multiplied by 1400 to be approximately equal to 4L, the two gases are filled in the combustion and explosion tube within 20s, 4/20=0.2L/s =12L/min, taking methane as an example, 5% methane is entered, so the flow rate of methane is 12L/min multiplied by 5% =0.6L/min, the flow rate of air is 12-0.6=11.4L/min, according to the precision of the two gas flow meters, the precision of the methane flow meter is 0.1L/min per cell, the precision of the air flow meter is 0.5L/min, in order to ensure the accuracy of air intake, the flow rate of methane is 0.6L/min when 5% methane gas is tested, the flow rate of air is 11.5L/min, 20s of methane is admitted according to the flow rate, and the concentration of methane is 20s
Test example 1: taking methane as an example, the dynamic explosion limit of the methane is determined by using the method disclosed by the invention, and the experimental data are shown in tables 2 and 3.
Table 2: dynamic upper explosive limit of methane
| Volume/%) | Methane flow rate/L/min | Air flow rate/L/min | Time/s | Whether or not to explode |
| 14 | 1.8 | 11 | 19 | √ |
| 14.5 | 1.7 | 10 | 21 | √ |
| 15 | 2.3 | 13 | 16 | √ |
| 17 | 2.6 | 12.5 | 16 | √ |
| 17.3 | 2.4 | 11.5 | 18 | × |
| 17.1 | 2.7 | 13 | 16 | ××××× |
GB/T12474-2008 & lt & ltcombustible gas explosion limit in air & gt, according to national Standard of the people's republic of China
Determination of method, dynamic explosion upper limit of methane
Table 3: dynamic lower explosive limit of methane
| Volume/%) | Methane flow rate/L/min | Air flow rate/L/min | Time/s | Whether or not to explode |
| 6 | 0.7 | 11 | 18 | √ |
| 5.5 | 0.5 | 8.5 | 27 | √ |
| 5.0 | 0.6 | 11.5 | 20 | × |
| 5.3 | 0.7 | 12.5 | 18 | √ |
| 5.2 | 0.6 | 11 | 21 | ××××× |
According to the national standard of the people's republic of China, GB/T12474-2008' determination of explosion limit of combustible gas in air
Method, dynamic explosion lower limit of methane
Maximum pressure and maximum rate of pressure rise in dynamic detonation: the maximum explosive pressure of combustible gas refers to the maximum explosive pressure of a combustible gas, which is determined by a series of experiments under different concentrations. The maximum pressure rise rate refers to the maximum slope of the curve of the explosion pressure as a function of time measured during the explosion. The data testing instrument comprises a piezoelectric sensor and a data acquisition recorder, after mixed gas in the pipeline explodes, the generated pressure is converted into a pressure signal through the piezoelectric sensor to form an electric signal, and a curve of pressure change in the pipeline is displayed through the data acquisition recorder in an electric signal mode. The recorded data is the data of the electric signal, and the maximum pressure of the combustible gas dynamic explosion can be calculated by converting the voltage value into the pressure value according to the following formula:
in the formula (I); u shape m -the voltage at the output of the charge amplifier in the recorder, mv;
S q is provided with -sensitivity set by the charge amplifier in the recorder, 10Pc/unit;
K v -the amplification set by the charge amplifier in the recorder, 300mv/unit;
S q -sensitivity of the calibrated piezoelectric sensor.
Flame propagation speed: continuously shooting flame propagation pictures of dynamic explosion of a plurality of combustible gases in a pipeline by using a high-speed camera, processing by matlab software to obtain the displacement movement of the flame, determining the time delta t between the pictures according to the frame number F adjustable by the camera, and calculating the propagation speed of the flame, wherein the calculation formula is as follows: time Δ t:
the camera shooting range d can be determined according to the camera focal length and the field angle 1. Assume that the total number of pixels in the x or y direction is M, N.
Size actually represented by one pixel of the camera: n = d/M
The coordinate of the image point S' of the object point S on the imaging surface can be obtained as (X) 0 ，Y 0 ) Thus, the actual coordinates (n × X) of the S point can be obtained 0 ，n×Y 0 ) To be provided withAnd next frame coordinate (X) 1 ，Y 1 ) And corresponding actual point coordinates (n X) 1 ，n×Y 1 ) And the moving distance of the S point between two continuous frames is as follows:
the object distance OD is measured using the gaussian imaging formula 1/f =1/u +1/v (f is the focal length, u is the object distance, and v is the image distance), and the imaging angle 2 can be calculated, thereby calculating the coordinates of the S point. The image distance OD' is:
and S 'D' = (X) 0 -M/2)×n 0 (n 0 In μm for the size of each pixel):
the distance that the S point moves between two consecutive frames is:
the flame propagation velocity can be calculated as
Claims (10)
1. A method for measuring dynamic explosion limit parameters of combustible gas comprises the steps that the dynamic explosion characteristic parameters of the combustible gas comprise the dynamic explosion limit and the minimum ignition energy of the combustible gas, the maximum pressure and the pressure rising rate of the dynamic explosion of the combustible gas, the propagation speed of the dynamic explosion flame of the combustible gas and the microstructure of a flame front vibration surface; the method for simultaneously feeding combustible gas and air is adopted; the method is characterized in that: the specific determination method comprises the following steps:
(1) Calculating the flow rate required by the fact that the combustible gas and the air in different proportions can be filled with the blasting tube within 15-20s when the combustible gas and the air are simultaneously fed;
(2) Starting a high-voltage discharger, a data acquisition recorder and a high-speed camera;
(3) The explosion pipeline is vacuumized by a vacuum pump, and the pressure change in the pipeline is less than or equal to 1KPa within 5 minutes;
(4) Opening a combustible gas source and an air source, adjusting a flow meter according to the flow and the air inlet time of the combustible gas and the air calculated in the step (1), and filling the mixed gas of the combustible gas and the air in the air inlet time to the explosion tube;
(5) After the mixed gas is filled in the detonating tube, continuously introducing the two gases for 5-10s according to the flow of the combustible gas and the air calculated in the step (1) so as to keep the mixed gas in a flowing state in the pipeline;
(6) Starting an ignition electrode for ignition, triggering a data acquisition recorder and a high-speed camera at the same time, observing whether mixed gas is ignited or not through an observation window on a detonation tube, acquiring explosion pressure parameters in the detonation tube when the mixed gas is ignited, recording flame propagation of dynamic explosion of the mixed gas, reducing the concentration alpha of combustible gas in the mixed gas for next experiment, increasing the concentration alpha of the combustible gas in the mixed gas for next experiment, and testing the dynamic explosion limit of the combustible gas;
(7) Cleaning the pipeline by using an air compressor for at least 3 times, and continuing to perform the next experiment from the step (2);
wherein: and (2) calculating the flow rate in the step (1) according to the set measuring range of the gas flowmeter, the scale requirement of the gas flowmeter and the volume of the blasting tube.
2. The method for determining the dynamic explosion limit parameter of a combustible gas according to claim 1, wherein: the vacuum degree of the explosion pipeline is-90.55 KPa.
3. The method for determining the dynamic explosion limit parameter of a combustible gas according to claim 1, wherein: in the step (6), the concentration alpha of the combustible gas in the mixed gas is that the upper limit of the static explosion limit of the combustible gas is not more than alpha and not more than the lower limit of the static explosion limit of the combustible gas; the mixed gas to be tested in the explosion tube is ignited by adopting an ignition electrode arranged in the pipeline and a high-voltage discharger; and triggering the acquisition of explosion characteristic parameter data while igniting the mixed gas to be detected in the blasting tube.
4. The method for determining the dynamic explosion limit parameter of a combustible gas according to claim 1, wherein: the specific data acquisition method comprises the following steps: the combustible gas dynamic explosion limit is obtained by observing the ignition state of the mixed gas through an observation window on the detonating tube, recording explosion pressure parameters by a data acquisition recorder and calculating the combustible gas dynamic explosion limit; the minimum ignition energy of the combustible gas dynamic explosion is determined by changing the ignition voltage of an electric spark generator; the maximum pressure of the dynamic explosion of the combustible gas is obtained by recording through a piezoelectric sensor and a data acquisition recorder, and the pressure rising rate is obtained by calculating through the change of pressure and time recorded in the data recorder; shooting a dynamic explosion flame propagation process of the combustible gas by a high-speed camera to calculate the flame propagation speed; and observing and analyzing the microstructure of the flame front vibration surface of the combustible gas dynamic explosion by using a schlieren instrument.
5. The detection device based on the method for determining the dynamic explosion limit parameters of the combustible gas according to any one of claims 1 to 4, which comprises an air inlet pipeline and an explosion pipeline which are connected by a communicating pipe, and is characterized in that: the air inlet pipeline is characterized in that one side of the first gas mixer (4) is connected with an air source (1), a combustible air source (13) and a vacuum pump (12), and the other side of the first gas mixer is connected with the secondary gas mixer (6); a drying device (2) and a gas flowmeter I (3) are connected between the air source (1) and the first gas mixer (4); a gas flowmeter II (14) is connected between the combustible gas source (13) and the first gas mixer (4); a flame arrester (5) is connected between the first gas mixer (4) and the second gas mixer (6); the explosion pipeline is characterized in that an explosion pipe (10) with 2 observation windows (17) arranged on the side wall is connected with a flame observation pipe (11) through a flange 0, an ignition electrode (16) is arranged at the air inlet end of the explosion pipe (10), the ignition electrode (16) is connected with a high-voltage discharger (15) through a high-voltage wire, a vacuum pressure gauge (7) is arranged between the air inlet of the explosion pipe (10) and the ignition electrode (16), 2 piezoelectric sensors (8) are connected above the explosion pipe (10), and the piezoelectric sensors (8) are connected with a data acquisition recorder (9); the bottom of the flame observation tube (11) is provided with an explosion venting port (18).
6. The detecting device based on the method for determining the dynamic explosion limit parameter of combustible gas as claimed in claim 5, wherein: the first gas mixer is a jet mixer based on a Venturi tube, the jet mixer is formed by sequentially connecting an air inlet pipe (4.2), a contraction pipe (4.3), a throat pipe (4.4) and a diffusion pipe (4.5) in the middle of 2 flanges I (4.1), the length of the air inlet pipe is 60mm, the length of the contraction pipe is 113.39mm, the contraction angle of the contraction pipe is 20 degrees, the length of the throat pipe is 20mm, the length of the diffusion pipe is 280.75mm, the diffusion angle of the diffusion pipe is 8 degrees, and the thicknesses of the air inlet pipe, the contraction pipe, the throat pipe and the diffusion pipe are 2mm;
the secondary gas mixer is a static mixer based on folded-face porous disks, the static mixer is a 2-end flange II (6.1) connected cylinder (6.4), a plurality of groups of disks provided with through holes are installed in the cylinder (6.4) at intervals, and each group of disks are arranged at intervals of a narrow-angle folded-face porous disk (6.2) and a wide-angle folded-face porous disk (6.3); the narrow-angle folding-surface porous disc (6.2) is characterized in that 9 chords are evenly distributed on the disc, the diameter perpendicular to the chords is divided into 10 equal parts, round holes I (6.22) with the radius of 2mm are respectively arranged at two ends of the diameter perpendicular to the chords on the disc, folding surfaces with the angle of 90 degrees are arranged on the 9 chords, strip-shaped through holes (6.21) are symmetrically arranged on the left and right sides of the intersection line of the folding surfaces and the disc, the width of each strip-shaped through hole (6.21) is 3mm, the distance between the outer side of each strip-shaped through hole and the periphery of the disc is 2.5mm, and the distance between the inner sides of each left strip-shaped through hole and the right strip-shaped through hole is 5mm; the wide-angle folding-surface porous disc (6.3) is characterized in that 4 chords are evenly distributed on the disc, the diameter perpendicular to the chords is divided into 5 equal parts, two ends of the diameter perpendicular to the chords on the disc are respectively provided with a round hole II (6.31) with the radius of 4mm, folding surfaces with the angle of 127 degrees are arranged on the 4 chords, a through hole (6.32) with the middle communicated is arranged on an intersecting line of the folding surfaces and the disc, the width of the through hole is 2mm, and the distance between two ends of the through hole and the periphery of the disc is 3mm.
7. The detecting device based on the method for determining the dynamic explosion limit parameter of combustible gas as claimed in claim 5, wherein: the distance between the vacuum pressure gauge and the air inlet of the blasting tube is 80mm, the distance between the ignition electrode and the air inlet of the blasting tube is 150mm, and the distance between the ignition electrodes is 2mm; the distances between the 2 piezoelectric sensors and the air inlet of the blasting tube are respectively 300mm and 850mm, and the distances between the 2 observation windows and the air inlet of the blasting tube are respectively 150mm and 800mm.
8. The apparatus for detecting the dynamic explosion limit specific parameter of a combustible gas according to claim 5, wherein: the length of the blasting tube is 1400mm, the inner diameter of the blasting tube is 60mm, the wall thickness of the blasting tube is 8mm, and the blasting tube is made of 304 stainless steel; the outer diameter of the flame observation tube is 90mm, the inner diameter of the flame observation tube is 60mm, the length of the flame observation tube is 1000mm, and the flame observation tube is made of organic glass; the communicating pipe is a 1/2 stainless steel pipe.
9. The detecting device based on the method for determining the dynamic explosion limit parameter of combustible gas as claimed in claim 6, wherein: the cylinder length is 700mm, and the internal diameter is 60mm, and the wall thickness is 15mm, and the disc diameter of narrow angle folded surface porous disc and wide angle folded surface porous disc is 60mm, and is 1mm thick.
10. The detecting device based on the method for determining the dynamic explosion limit parameter of a combustible gas according to claim 5 or 6, wherein: the thickness of the flange 0, the flange I and the flange II is 15mm.
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