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The explosion characteristics and composite flame propagation characteristics of shock wave induced sedimentary coal dust were studied, the characteristics of coal dust rolling under the initial shock wave of different intensities were analyzed, and the acceleration mechanism of composite impact flame was discussed.
Author
PEI Bei1, ZHANG Ziyang1, PAN Rongkun1, YU Minggao2, CHEN Liwei1, WEN Xiaoping1
Unit
1. Henan Collaborative Innovation Center for Coal Safety Production of Henan Polytechnic University; State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University
Research background
Gas explosions are the "number one killer" that affects the safe production of coal mines. Major explosion accidents in coal mines are often caused by the joint participation of gas and coal dust in the explosion, and the shock wave generated by the gas explosion continuously sucks the coal dust deposited around the roadway during the propagation process, forming an unevenly distributed flammable dust cloud, which is subsequently ignited by the high temperature flame surface and spreads in the form of uninterrupted explosion, resulting in a gas/coal dust explosion with higher destructiveness.
The existing research mainly focuses on explosive characteristics such as explosion overpressure and flame propagation speed when gas/coal dust coexist. Since the coal mine gas/coal dust explosion flame is a complex formed by the shock wave-guided coal dust cloud flame, the shock wave intensity has an important impact on the coiling effect of the deposited coal dust, and there are currently few studies on the formation and acceleration of the composite impact flame. To this end, it is necessary to further study the coal dust coil suction characteristics at different explosion intensities to reveal its effect on the acceleration of gas/coal dust explosion flames.
Excerpt
In the fully transparent plexiglass pipeline, the explosion characteristics of induced sedimentary coal dust and the propagation characteristics of composite flame under the conditions of explosion intensity were studied from the aspects of explosion overpressure, flame propagation speed, flame temperature and composite flame evolution law, and the characteristics of coal dust roll turbulence were analyzed by using synchronous control system, high-speed camera system and high-speed particle imaging velocimetry system (PIV).
The experimental results show that under three working conditions, with the increase of methane volume fraction, the explosion overpressure and pressure rise rate increase significantly, the pressure peak is reduced at the moment of arrival, and when the volume fraction exceeds 8.5%, the pressure curve and pressure rise rate curve have obvious oscillation characteristics. The propagation speed of the composite flame is much greater than that of pure gas explosion, and the propagation velocity-position curve of the composite flame is characterized by fluctuating upwards; The closer the volume fraction of methane is to the equivalent ratio, the higher the explosion overpressure, wavefront flow rate, flame front temperature and its temperature rise rate; When the methane volume fraction is 9.5% and 8.5%, the composite flame is "barb-shaped", and then the flame acceleration occurs soon after; After the methane volume fraction is reduced to 8.5%, the brightness of the composite flame decreases, and the structure shows the morphological characteristics of fragmentation and discontinuity.
PIV test shows that when the methane volume fraction is 9.5%, the initial explosion intensity is high, the wavefront flow rate is fast, the pulverized coal can move rapidly with the shock wave as a whole, and the overall turbulence intensity of the winch area is high, which greatly accelerates the mixing speed of pulverized coal and air, and promotes the combustion of pulverized coal. The combination of high shock wavefront flow rate and flame front temperature is the reason for the continuous acceleration of the methane/coal dust composite flame.
Partial picture
Experimental system
Particle size distribution and SEM image of pulverized lignite coal
Three intensity shock waves induce the explosion pressure-time curve of deposited coal dust
Three intensity shock waves induce the explosion pressure rise rate-time curve of deposited coal dust
Temperature-time curve of 3 intensity shock waves inducing deposited coal dust explosion flames
The peak temperature of the flame and the arrival time change with the shock wave intensity curve
Three intensity shock waves induce the temperature rise rate-time curve of the deposited coal dust explosion flame
The maximum temperature rise rate of the composite flame and its arrival moment change with the volume fraction of methane
Three intensity shock waves induce coal dust explosion flame propagation velocity-time curve
Three intensity shock waves induce the propagation velocity-propagation distance curve of the deposited coal dust explosion flame
Three intensity shock waves induced deposited coal dust explosion flame structure image
Illustration of the PIV experimental system
Three intensity shock waves induce coal dust explosion instantaneous velocity field and vortex magnitude field
Methane/coal dust explosion composite flame acceleration mode
About the Author
Pei Bei, female, born on September 28, 1982, Tangyin, Henan, doctor of engineering, associate professor, master supervisor, first-class registered fire engineer, registered safety engineer, teacher of the Department of Fire Engineering of the School of Safety Science and Engineering of Henan Polytechnic University, mainly engaged in teaching and research in fire and explosion protection, school-level backbone teacher. He has won 4 provincial and ministerial science and technology awards and published more than 50 academic papers.
Research Directions
Fire and explosion protection
Key results
Committed to the research of gas-liquid two-phase medium explosion suppression theory and technology, a number of innovative achievements have been made, and a comprehensive protection technology system with additive-containing dual fluid inertized fine water mist explosion suppression and disaster reduction suitable for well lanes and extraction pipe networks has been formed, providing safe, clean and efficient explosion suppression and disaster reduction technology for coal mines.
source:
PEI Bei,ZHANG Ziyang,PAN Rongkun,et al. Flame propagation characteristics of sedimentary coal dust explosion induced by shock waves of different intensities[J]. Journal of China Coal Society,2021,46(2):498-506.]
PEI Bei,ZHANG Ziyang,PAN Rongkun,et al. Flame propagation characteristics of deposited coal dust explosion induced by shock waves of different intensities[J]. Journal of China Coal Society,2021,46(2):498-506.
Editor-in-charge: Qian Xiaojing
Editor:Guo Xiaowei
Review: Chang Chen
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