To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion chara...To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion characteristics and flame propagation characteristics of methane in pipeline and coal mine tunnel are studied by using an explosion test system,combined with FLACS software,under different vented conditions.The numerical simulation results of methane explosion are basically consistent with the physical experiment results,which indicates that the numerical simulation for methane explosion is reliable to be applied to the practice.The results show that explosion parameters(pressure,temperature and product concentration)of methane at five volume fractions have the same change trend.Nevertheless,the explosion intension of 10.0%methane is the largest and that of 9.5%methane is relatively weak,followed by 11.0%methane,8.0%methane and 7.0%methane respectively.Under different vented conditions,the pressure and temperature of methane explosion are the highest in the pipeline without a vent,followed by the pipeline where ignition or vent position is in each end,and those are the lowest in the pipeline with ignition and vent at the same end.There is no significant effect on final product concentration of methane explosion under three vented conditions.For coal mine tunnel,it is indicated that the maximum explosion pressure at the airproof wall in return airway with the branch roadway at 50 m from goaf is significantly decreased while that in intake airway does not change overwhelmingly.In addition,when the branch roadway is longer or its section is larger,the peak pressure of airproof wall reduces slightly.展开更多
To investigate the flame and overpressure characteristics of methane–air explosion with different obstacle configurations,an experimental study has been conducted,taking account of the number of obstacles,obstacle di...To investigate the flame and overpressure characteristics of methane–air explosion with different obstacle configurations,an experimental study has been conducted,taking account of the number of obstacles,obstacle distance from ignition source,and stream-wise and cross-wise obstacle positions.The results show that the flame speed and peak overpressure increase with the increasing number of obstacles,while the time to reach the peak is not fully determined by it.And the configuration having the farthest obstacle produces a higher overpressure and takes a longer time to reach the peak,but a slower flame propagation speed is obtained.Similar explosion characteristics are also observed in the configurations with two obstacles fixed at different stream-wise positions.Furthermore,the experimental results demonstrate that the peak overpressures and flame speeds in configurations with central or staggered obstacles are relatively higher,which should to be avoided in practical processes to minimize the risk associated with methane–air explosion.展开更多
A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar ...A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.展开更多
基金Project(51674193)supported by the National Natural Science Foundation of ChinaProject(2019-JLM-9)supported by the Natural Science Foundation of Shaanxi Province,ChinaProject(2019-M-663780)supported by the Postdoctoral Science Foundation,China。
文摘To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion characteristics and flame propagation characteristics of methane in pipeline and coal mine tunnel are studied by using an explosion test system,combined with FLACS software,under different vented conditions.The numerical simulation results of methane explosion are basically consistent with the physical experiment results,which indicates that the numerical simulation for methane explosion is reliable to be applied to the practice.The results show that explosion parameters(pressure,temperature and product concentration)of methane at five volume fractions have the same change trend.Nevertheless,the explosion intension of 10.0%methane is the largest and that of 9.5%methane is relatively weak,followed by 11.0%methane,8.0%methane and 7.0%methane respectively.Under different vented conditions,the pressure and temperature of methane explosion are the highest in the pipeline without a vent,followed by the pipeline where ignition or vent position is in each end,and those are the lowest in the pipeline with ignition and vent at the same end.There is no significant effect on final product concentration of methane explosion under three vented conditions.For coal mine tunnel,it is indicated that the maximum explosion pressure at the airproof wall in return airway with the branch roadway at 50 m from goaf is significantly decreased while that in intake airway does not change overwhelmingly.In addition,when the branch roadway is longer or its section is larger,the peak pressure of airproof wall reduces slightly.
基金supported by the National Natural Science Foundation of China (Nos.51106044 and 51176021)the Research Foundation of Education Bureau of Henan Province of China (No.14A410007)
文摘To investigate the flame and overpressure characteristics of methane–air explosion with different obstacle configurations,an experimental study has been conducted,taking account of the number of obstacles,obstacle distance from ignition source,and stream-wise and cross-wise obstacle positions.The results show that the flame speed and peak overpressure increase with the increasing number of obstacles,while the time to reach the peak is not fully determined by it.And the configuration having the farthest obstacle produces a higher overpressure and takes a longer time to reach the peak,but a slower flame propagation speed is obtained.Similar explosion characteristics are also observed in the configurations with two obstacles fixed at different stream-wise positions.Furthermore,the experimental results demonstrate that the peak overpressures and flame speeds in configurations with central or staggered obstacles are relatively higher,which should to be avoided in practical processes to minimize the risk associated with methane–air explosion.
基金Supported by the National Natural Science Foundation of China (51176181)the National Basic Research Program of China (2012CB719704)
文摘A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.
