Experimental study on inhibiting methane-coal dust explosion by APP-diatomite composite explosion suppressant in the pipe network

2.1 Experimental apparatus

As shown in Fig. 1, the experimental setup consists of an experimental pipe network system, dynamic data acquisition system, powder spraying system, and ignition system. The experimental piping system consists of several carbon steel pipes with different lengths and inner diameters of 300 mm, each of which is connected by flanges. The size of the pipe network is 4500 mm × 3600 mm, the volume of the explosion chamber is 30 L, the explosion chamber is separated from the pipe connection by polytetrachloroethylene film, and the maximum pressure resistance of the pipe network is 2.5 MPa. The two outlets of the pipe network are closed with flanges as well as a PTFE membrane for explosion relief. The pipe is equipped with several sensor sockets of size M20 x 1.5 for simultaneous insertion of pressure sensors, temperature sensors, and flame sensors. The various components are connected to the piping using female threads, and the airtightness of the unit is improved by installing silicone gaskets at the connection between each component and its corresponding piping. The dynamic data acquisition system mainly includes a QSY8124 pressure sensor (range: 0–10 MPa), NANMAC transient temperature sensor (range: 0–2000 K), CKG100 light-sensitive high-precision flame sensor, and TST6300 dynamic data acquisition instrument. The response times of the pressure sensor, temperature sensor, and flame sensor were 1 ms, 10 ms, and 1 ms, respectively, and the accuracy of the data acquisition device was 0.2 % FS with a continuous acquisition frequency of 10 KHz/CH. The powder spraying system utilizes the gas storage cylinder to provide the driving gas N₂ and the air pump to control the powder spraying pressure. The ignition system mainly includes a DX-GDH high-energy igniter, high-energy spark plug, high-voltage and high-temperature-resistant cable, power supply cable, and external trigger device. The ignition control box is connected to the external trigger wire. The spark plug is placed at the front of the explosion chamber, with an ignition voltage of about 2200 V and a single energy storage of 30J. Let the distance between two flame sensors be L. Record the flame wave passing through two neighboring sensors at different moments t₁ and t₂, then the flame propagation speed is calculated using $v=\frac{\text{L}}{t_2-t_1}$ .

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Fig. 1

Experimental pipe network system.

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2.2 Experimental conditions

Set APP relative to diatomite mass fraction of 25 %, 30 %, 35 %, 40 %, and 45 % for methane-coal dust composite explosion suppression experiments (Liu et al., 2023). The methane concentration was set to 9.5 %, the Daltonton partial pressure method was used for gas distribution, and after compounding, the mass concentration of the composite detonation inhibitor was set to 0.0625 g/L, and the mass concentration of coal dust was 0.125 g/L (Guo et al., 2024). Coking coal with an explosion index of 31.56 % in the Sihe Coal mine was selected as a coal sample in this experiment. Through electron microscope scanning and industrial analysis, the moisture, ash, and volatile content of the coal dust sample are 1.56 %, 12.06 %, and 30.06 %, respectively. The particle size distribution of coal dust is shown in Fig. 2.

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Fig. 2

Particle size distribution and SEM image of pulverized coal.

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2.3 Experimental process

Before each test, the powder is evenly placed at the bottom of the pipeline (see Fig. 1b), the explosion chamber is separated from the pipeline with a polytetrachloroethylene film, and then the explosion chamber is vacuumed and gas test gas with a volume fraction of 9.5 % is injected. There is normal pressure air in the pipeline, after the completion of the gas distribution, the air inlet and the burst outlet are closed at the same time. After standing for 30 s, the air pump is opened, the driving gas N₂ in the gas storage tank is rapidly ejected, and the explosion suppressive powder in the pipeline is blown up. After a stationary period of 600 ms, turn on the switch of the external trigger device, and ensure that the igniter and the data acquisition system start to work simultaneously. After the signal light on the device, press the trigger button on the external trigger device to trigger the ignition. After the end of the experiment, the exhaust gas in the pipeline will be discharged, the gas washing work will be carried out in the pipeline, and the next test will be carried out after completion.

2.4 Powder characterization

Fig. 3 shows the electron microscope scanning images of APP, diatomite, and composite powder. From Fig. 3b, it can be seen that diatomite as the carrier of the composite inhibitor showed a disc shape, with fine circular pores distributed on the surface of the disc the pore distribution was more uniform, and the porosity was more developed. As can be seen in Fig. 3c, the crystal structure of the composite powder was highly similar to the structure of diatomite, but its surface was partially covered by APP particles, making its morphology irregular. In the process of explosion suppression, the pores on the surface of the diatomaceous earth not covered by APP particles can adsorb coal dust, free radicals, and so on. Diatomite in the composite powder not only made up for the defects of APP without pores but also improved the phenomenon that monomer APP is easy to agglomerate and stick.

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Fig. 3

SEM images of (a) APP, (b) diatomite, and (c) APP/diatomite composite powder.

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The XRD spectra of diatomite, APP, and diatomite-APP are shown in Fig. 4. The XRD characteristic diffraction peaks of the composite powders were basically the same as those of diatomite, and the characteristic diffraction peaks of APP can be observed at 2θ of 14.404°, 16.736°, 18.384°, 20.124°, and 45.578°, respectively. The results of the study show that the composite powder contained diatomite and APP.

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Fig. 4

XRD patterns of explosion inhibitors.

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3.1 Explosion overpressure

The use of a self-constructed test pipe network to test the single APP, a single diatomite, and different loadings of composite explosion suppression of the monitoring points of the effect of explosion suppression.

Fig. 5 shows the inhibition effect of inhibitors with different compounding ratios on explosion overpressure in monitoring point 1 and monitoring point 2. As shown in Fig. 5a and b, in the absence of explosive suppressants, the influence of complex pipelines, monitoring point 1 and monitoring point 2 of the blank group of overpressure shock waves in the propagation process of both multiple superposition and attenuation. The first overpressure peak at both monitoring points appeared at the beginning of the reaction, with the thermal decomposition of the raised coal dust cloud under the action of high temperature and high pressure, a sufficient amount of combustible gases were generated and participated in the reaction, the overpressure value increased again, and the second overpressure peak appeared, and the second overpressure peak was significantly larger than the first overpressure peak, indicating that the secondary explosion of methane and coal dust occurred in the branch pipe 1 (Zhao et al., 2021). The violent reaction accumulated mainly in the early stages of the explosion, with minor fluctuations in the later stages mainly due to the influence of the reverse overpressure shock wave in the other lines.

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Fig. 5

Overpressure time history curve of different compound ratio suppressors at monitoring point 1 and monitoring point 2.

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After adding the explosion suppressant, monitoring point 1 and monitoring point 2 in the secondary explosion of coal dust and methane characteristics disappear, the overpressure time curve has become “single peak” characteristics, and the overpressure time curve is more gently fluctuating. Overpressure decreased significantly and peak time reached a significant increase in about 1.7 s overpressure down to 0 MPa, the end of the explosion suppression reaction. The overpressure time curve into a “single peak” was mainly due to the suppression of the explosion suppression agent to inhibit the second explosion of methane and coal dust reaction, in the process of suppression of explosion suppression in the explosion suppression powder diluted coal dust and oxygen concentration, so that the coal dust did not reach the conditions of the second explosion. The overpressure time curve of monitoring point 2 after the suppression of explosion fluctuations was slightly larger than the degree of fluctuation of monitoring point 1, mainly due to the location of monitoring point 2 was backward, more sensitive to the impact of the reverse overpressure shock wave than the monitoring point 1.

A comparison of the addition of single-component explosion suppressant found that the addition of APP overpressure peak was slightly smaller than the addition of diatomite overpressure peak, and the addition of APP overpressure peak came later than diatomite explosion suppressant, composite powder overpressure peak was lower than single-component explosion suppressant. In monitoring point 1, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.248 MPa, 0.227 MPa, 0.218 MPa, 0.207 MPa, 0.211 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decrease was 49.7 %, 54.0 %, 55.8 %, 58.1 % and 57.2 %, respectively. In monitoring point 2, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.209 MPa, 0.201 MPa, 0.194 MPa, 0.173 MPa, 0.183 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 55.2 %, 56.9 %, 58.4 %, 62.9 %, 60.7 %, respectively. Therefore, the 40 wt% loading rate of the compound explosive suppressant overpressure peak in monitoring point 1 and monitoring point 2 of the largest decline, the best effect of suppressing overpressure shock wave.

Fig. 6 shows the inhibition effect of inhibitors with different compounding ratios on explosion overpressure in monitoring point 3 and monitoring point 4.

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Fig. 6

Overpressure time history curve of different compound ratio suppressors at monitoring point 3 and monitoring point 4.

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As shown in Fig. 6c and d, in the absence of a suppressant, the time interval between the first overpressure peak and the second overpressure peak at monitoring point 3 and monitoring point 4 in branch pipe 2 was extended compared to monitoring point 1 and monitoring point 2. The main reason was that the location of monitoring point 1 and monitoring point 2 was close to the source of the explosion, the temperature of the explosion was higher, and the high temperature near the source of the explosion could be transferred to the location of monitoring point 1 and monitoring point 2 more quickly to provide a heat source for the secondary explosion of monitoring point 1 and monitoring point 2. It took some time for the heat source to conduct monitoring point 3 at the right-angle pipe bends and monitoring point 4 near the bursting vents. As a result, the time interval between the occurrence of the first overpressure peak and the second overpressure peak at monitoring point 3 and monitoring point 4 in branch 2 had lengthened. The location also led to a prolonged time to peak overpressure at monitoring points 3 and 4, and the violent reaction was mainly concentrated in the middle of the explosion.

After adding the explosion inhibitor, coal dust, and methane secondary explosion characteristics disappeared, monitoring point 3 and monitoring point 4 at different compound ratios of the overpressure time curve trend were similar, showing a single peak characteristics of the overpressure time curve were more gentle fluctuations, compared to the blank group of the overpressure peak value decreased significantly and peak time increased significantly. Monitoring point 3 overpressure was fully suppressed by 1.75 s and monitoring point 4 overpressure was fully suppressed by 1.5 s. Monitoring point 4 overpressure peak than monitoring point 3 overpressure peak was lower, monitoring point 4 overpressure can be suppressed earlier mainly due to the location of monitoring point 4 was close to the explosion release port and the location of the explosion from the source of the more distant, subject to the other pipeline shock wave back to the superposition of the role of the smaller. At the same time, the overpressure shockwave flowed through monitoring point 4, passing through the bifurcation of the pipeline as well as being subjected to oxygen consumption, resulting in a more significantly suppressed overpressure in monitoring point 4 compared to monitoring point 3.

A comparison of the addition of single-component explosion suppressant found that the addition of APP overpressure peak was slightly smaller than the addition of diatomite overpressure peak, and the addition of APP overpressure peak came later than the diatomite explosion suppressant, composite powder overpressure peak was lower than a single component of the explosion suppressant. In monitoring point 3, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.226 MPa, 0.211 MPa, 0.198 MPa, 0.183 MPa and 0.189 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 51.8 %, 55.0 %, 57.8 %, 61.0 %, and 59.7 %, respectively. In monitoring point 4, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.119 MPa, 0.114 MPa, 0.111 MPa, 0.103 MPa, 0.107 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 67.0 %, 68.4 %, 69.3 %, 71.5 %, and 70.4 %, respectively. Therefore, the 40 wt% loading rate of the compound explosive suppressant overpressure peak in monitoring point 3 and monitoring point 4 of the largest decline, the best effect of suppressing overpressure shock wave.

Fig. 7 shows the inhibition effect of inhibitors with different compounding ratios on explosion overpressure in monitoring point 5 and monitoring point 6. As shown in Fig. 7e and f, in the absence of explosive suppressants, the shock wave evolution process at monitoring point 6 was more complex than at monitoring point 5, with more overpressure fluctuations occurring at the later stages of monitoring point 6. The number of overpressure extreme points occurring in monitoring point 6 was more than that in monitoring point 5, mainly because monitoring point 6 was affected by the superposition of overpressure shock waves in other pipelines more than monitoring point 5. After the first overpressure peak, both monitoring points experienced a secondary explosion due to the incomplete methane-coal dust reaction and the resulting high temperature that would trigger the residue reaction again, and the two monitoring points reached the overpressure peak at similar times.

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Fig. 7

Overpressure time history curve of different compound ratio suppressors at monitoring point 5 and monitoring point 6.

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After adding the explosion suppression agent, suppressed the secondary explosion of methane coal dust, similar to other monitoring points, the overpressure time curve had only one peak, after reaching the peak, the overpressure was a decreasing trend, the two monitoring points in about 1.75 s dropped to 0 MPa, the end of the suppression of the explosion of the end of the time was not much different. However, the location of monitoring point 6 was closer to the source of the explosion compared to the location of monitoring point 5, so the peak overpressure after the addition of the detonation suppression agent monitoring point 6 came earlier than monitoring point 5.

A comparison of the addition of single-component explosion suppressant found that the addition of APP overpressure peak was slightly smaller than the addition of diatomite overpressure peak, and the addition of APP overpressure peak came later than the diatomite explosion suppressant, composite powder overpressure peak was lower than a single component of the explosion suppressant. In monitoring point 5, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.187 MPa, 0.183 MPa, 0.170 MPa, 0.151 MPa and 0.160 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 54.8 %, 55.8 %, 59.0 %, 63.5 %, and 61.3 %, respectively. In monitoring point 6, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.180 MPa, 0.172 MPa, 0.168 MPa, 0.160 MPa and 0.165 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 52.8 %, 55.0 %, 56.0 %, 58.2 %, and 56.9 %, respectively. Therefore, the 40 wt% loading rate of the compound explosive suppressant overpressure peak in monitoring point 5 and monitoring point 6 of the largest decline, the best effect of suppressing overpressure shock wave.

Fig. 8 shows the inhibition effect of inhibitors with different compounding ratios on explosion overpressure in monitoring point 7 and monitoring point 8. As shown in Fig. 8g and h, in the absence of explosive suppressants, the two monitoring points in the branch pipe 4 reached the first overpressure peak due to the action of the forward shock wave, followed by a second overpressure peak in the two monitoring points. Monitoring point 7 of the second overpressure peak was greater than the first overpressure peak, mainly due to the lifted coal dust cloud of coal dust under the action of high temperature and high-pressure thermal decomposition, the production of a sufficient number of combustible gases and participating in the reaction, resulting in the value of the overpressure increases again. However, the second overpressure peak at monitoring point 8 was significantly lower compared to the first overpressure peak. The main reason was that monitoring point 8 was raised by the concentration of coal dust cloud reduced, and monitoring point 8 was in the explosion relief port, part of the pressure loss, and due to the decreasing oxygen content in the pipeline, resulting in a reduction in the power of the secondary explosion, which led to the monitoring of the second overpressure peak at point 8 compared to the first overpressure peak was low.

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Fig. 8

Overpressure time history curve of different compound ratio suppressors at monitoring point 7 and monitoring point 8.

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After adding the inhibitor, the secondary explosion of gas and coal dust at the two monitoring points was suppressed, and similar to the other monitoring points, the overpressure time-course curves showed the characteristic of a “single peak”. At monitoring point 7, about 1.75 s, the explosion overpressure was completely suppressed, at monitoring point 8, about 1.6 s, the explosion overpressure dropped to 0 MPa, monitoring point 8 by the location of the impact of the peak overpressure, resulting in lower peak overpressure, and thus suppression of the peak overpressure after the explosion was also lower, suppression of the explosion used for a shorter period.

A comparison of the addition of single-component explosion suppressant found that the addition of APP overpressure peak was slightly smaller than the addition of diatomite overpressure peak, and the addition of APP overpressure peak came later than the diatomite explosion suppressant, composite powder overpressure peak was lower than a single component of the explosion suppressant. In monitoring point 7, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.235 MPa, 0.222 MPa, 0.213 MPa, 0.200 MPa and 0.208 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 50.4 %, 53.1 %, 55.1 %, 57.8 %, and 56.1 %, respectively. In monitoring point 8, the peak overpressure of 25 wt%, 30 wt%, 35 wt%, 40 wt%, and 45 wt% of the compounded explosion suppressant was 0.153 MPa, 0.149 MPa, 0.146 MPa, 0.135 MPa, 0.141 MPa, respectively. Compared to the first overpressure peak without detonation suppressant, the decreases was 59.0 %, 60.0 %, 60.6 %, 63.6 %, and 62.12 %, respectively. Therefore, the 40 wt% loading rate of the compound explosive suppressant overpressure peak in monitoring point 7 and monitoring point 8 of the largest decline, the best effect of suppressing overpressure shock wave.

From the above experimental results: whether it was a single-component explosion suppressant or a multi-component composite powder explosion suppressant, both can suppress the secondary explosion of methane-coal dust. The main reason was that the explosion suppressant raised during the explosion suppression process diluted the concentration of coal dust and oxygen, making the coal dust not reach the conditions for the secondary explosion. After adding the explosive suppressant, the overpressure time history curves exhibit a “single peak” characteristic. This change primarily results from the suppressant inhibiting the forward propagation of the explosive shock wave, it reduces the instances of shock wave reflections against the pipeline walls and diminishes the influence of opposing overpressure shock waves from other lines. Consequently, the multiple oscillations formed by oppositely propagating shock waves are also diminished, leading to a significant decrease in the peak overpressure values at various monitoring points. Thus, after the addition of the suppressant, multiple peak overpressures disappear, and the overpressure time history curves show a “single peak” characteristic.

Through the above analysis, it is concluded that: adding an APP explosion suppressor is better than adding a diatomite explosion suppressor to inhibit shock wave explosion overpressure. The composite powder has a synergistic inhibition effect on methane-coal dust explosion shock wave propagation. Among them, 40 wt% loading of the compound explosive suppressant inhibition of overpressure shock wave is the most effective. The maximum reduction in peak explosion overpressure for the 40 wt% loaded composite suppressant is 71.5 % at monitoring point 4.

In addition, the data summarized in Fig. 9 reveals that the maximum pressure at Monitoring Point 1 before the explosion suppression was 0.493 MPa. Monitoring Point 7 followed with a pressure of 0.474 MPa, indicating that the pressure at Point 7 is less than that at Point 1. After the suppression, the explosive pressure pattern remained consistent. The reason lies in the shock wave's behavior as it passes through monitoring point 7. Due to the bifurcation in the pipeline, the shock wave experiences attenuation. Consequently, the pressure loss is greater at this point compared to monitoring point 1. Therefore, the pressure measurements at point 7, both before and after the detonation, remain lower than those at point 1. Monitoring points 4 and 8 exhibited the lowest explosion pressure. After suppression, they displayed the same pattern. The reason lies in their locations; they are the farthest from the explosion source and closest to the vent. Consequently, the pressure at points 4 and 8, both before and after suppression, remained lower than at other monitoring points. The pressure at the three monitoring points before and after the suppression is greater than the pressure at point two. Due to the geometric changes of the pipeline, shock waves flowing through right-angled pipes will cause dramatic changes in fluid dynamics. This phenomenon creates a zone of overpressure, resulting in pressures at the three monitoring points being consistently higher than that at point two. The analysis concludes that, unlike the behavior observed in long straight pipes or spherical explosions, shock waves do not simply diminish with distance in various pipe structures. Instead, they exhibit multiple instances of overpressure fluctuations, increasing and decreasing repeatedly during propagation. Therefore, the conclusions obtained from the explosion suppression experiment in the pipe network are more universal.

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Fig. 9

Peak value of overpressure before and after explosion suppression at each monitoring point.

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3.2 Flame velocity

Fig. 8 shows the peak flame propagation velocity of diatomite, APP, and different compound ratios of suppressors in branch pipe 1 to branch pipe 4 and the curve of the time to reach the peak flame propagation velocity. The peak flame propagation velocity of the blank group in branch pipe 1 to branch pipe 4 was 348.7 m·s⁻¹, 368.1 m·s⁻¹, 385.6 m·s⁻¹, 342.6 m·s⁻¹, respectively. From branches 1 to 4 in the figure, it can be seen that the addition of diatomite and APP can significantly reduce the flame propagation speed, and APP had a better effect on flame propagation speed. It can be found that, compared with the condition of the blank group, the peak flame propagation velocity showed a decreasing trend with the increase of the composite powder compound ratio. The peak flame propagation velocities of 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% compound suppressors in branch pipe 1 was 37.1 m·s⁻¹, 34.3 m·s⁻¹, 33.0 m·s⁻¹, 28.9 m·s⁻¹ and 30.8 m·s⁻¹, respectively. The decreases was 89.4 %, 90.2 %, 90.5 %, 91.7 %, and 91.2 % respectively. The peak flame propagation velocities of 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% compound suppressors in branch pipe 2 was 38.8 m·s⁻¹, 36.3 m·s⁻¹, 35.9 m·s⁻¹, 30.1 m·s⁻¹ and 33.2 m·s⁻¹, respectively. The decreases was 88.9 %, 89.6 %, 89.7 %, 91.4 %, and 90.5 %, respectively. The peak flame propagation velocities of 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% compound suppressors in branch pipe 3 was 42.6 m·s⁻¹, 40.1 m·s⁻¹, 38.3 m·s⁻¹, 33.2 m·s⁻¹ and 35.9 m·s⁻¹, respectively. The decreases was 89.0 %, 89.6 %, 90.1 %, 91.4 %, and 90.7 %, respectively. The peak flame propagation velocities of 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% compound suppressors in branch pipe 4 was 36.5 m·s⁻¹, 35.9 m·s⁻¹, 34.2 m·s⁻¹, 26.8 m·s⁻¹ and 29.5 m·s⁻¹, respectively. The decreases was 89.3 %, 89.5 %, 90.0 %, 92.2 %, and 91.4 %, respectively. Among them, the flame propagation velocity of 40 wt% composite powder in each branch pipe decreased the most.

According to the above experimental results, the effect of APP on flame propagation of gas-coal dust explosion is better than that of diatomite, and the composite powder has a synergistic effect on flame propagation of methane-coal dust explosion. Among them, the compound powder of 40 wt% has the best effect of inhibiting the spread of explosion flame. The peak flame propagation velocity of 40 wt% composite powder in branch pipe 1, branch pipe 2, branch pipe 3, and branch pipe 4 decreased by 91.7 %, 91.4 %, 91.4 %, and 92.2 % respectively, and the largest decrease was 92.2 % in branch pipe 4.

In addition, in terms of flame wave velocity, it can be seen from Fig. 10 that the order of flame propagation velocity before explosion suppression is branch pipe 3, branch pipe 2, branch pipe 1, branch pipe 4. After explosion suppression, the propagation velocity of each branch pipe flame wave is the same as that before explosion suppression. The flame wave velocity in branch pipe 3 was the largest because the pressure loss at monitoring points 3 and 4 in branch pipe 3 was the largest. The flame front acceleration gradient in branch pipe with greater pressure loss was larger and the flame front propagation speed was higher, while the flame front acceleration gradient in branch pipe with smaller pressure loss was smaller and the flame front velocity was lower. Therefore, according to the different structures of the pipeline, the flame wave propagation speed will increase and decrease with the change in the pipeline. Therefore, the conclusions obtained from the explosion suppression experiment in the pipeline network are more universal. In the future, explosion prevention and control can be carried out in specific locations according to the geometric mechanism of the actual pipe network, which provides an effective means for ensuring the safe operation and emergency rescue of the pipeline system.

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Fig. 10

Inhibition effect of different compound ratio inhibitors on flame velocity.

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