MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severit...MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severity,the Hartmann device and spherical pressure vessel were used to test ignition energy and explosion pressure,respectively.The results showed that the ignition sensitivity of ZrH_(2),TiH_(2) and MgH_(2) gradually increased.When the concentration of MgH_(2) is 83.0 g/m^(3) in Hartmann device,the ignition energy attained a minimum of 10.0 mJ.The explosion pressure of MgH_(2) were 1.44 times and 1.76 times that of TiH_(2) and ZrH_(2),respectively,and the explosion pressure rising rate were 3.97 times and 9.96 times that of TiH_(2) and ZrH_(2),respectively,through the spherical pressure vessel.It indicated that the reaction reactivity and reaction rate of MgH_(2) were higher than that of TiH_(2) and ZrH_(2).In addition,to conduct in edepth theoretical analysis of ignition sensitivity and explosion severity,gas production and combustion heat per unit mass of ZrH_(2),TiH_(2) and MgH_(2) were tested by mercury manometer and oxygen bomb calorimetry.The experimental results revealed that MgH_(2) had a relatively high gas production per unit mass(5.15 mL/g),while TiH_(2) and ZrH_(2) both had a gas production of less than 2.0 mL/g.Their thermal stability gradually increased,leading to a gradual increase in ignition energy.Furthermore,compared with theoretical combustion heat,the combustion ratio of MgH_(2),TiH_(2) and ZrH_(2) was more than 96.0%,with combustion heat value of 29.96,20.94 and 12.22 MJ/kg,respectively,which was consistent with the explosion pressure and explosion severity test results.展开更多
In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers...In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas flows across the gob and the working areas and may result in a condition where an oxygen deficient mixture or a methane accumulation in the gob flows into the face area. Computational Fluid Dynamics(CFDs) modeling was carried out to analyze this phenomenon and its impact on the development of an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the formation of Explosive Gas Zones(EGZs) are directly affected by atmospheric pressure changes. In the location where methane zones interface with mine air, EGZ fringes may form along the face and in the bleeder entries. These findings help assess the methane ignition and explosion risks associated with fluctuating atmospheric pressures.展开更多
基金This work was greatly supported by the Natural Science Foundation of China(11802272)the Open Research Fund Program of Science and Technology on Aerospace Chemical Power Laboratory(STACPL220181B01).
文摘MgH_(2),TiH_(2),and ZrH_(2) are three typical metal hydrides that have been gradually applied to composite explosives and propellants as additives in recent years.To evaluate ignition sensitivity and explosion severity,the Hartmann device and spherical pressure vessel were used to test ignition energy and explosion pressure,respectively.The results showed that the ignition sensitivity of ZrH_(2),TiH_(2) and MgH_(2) gradually increased.When the concentration of MgH_(2) is 83.0 g/m^(3) in Hartmann device,the ignition energy attained a minimum of 10.0 mJ.The explosion pressure of MgH_(2) were 1.44 times and 1.76 times that of TiH_(2) and ZrH_(2),respectively,and the explosion pressure rising rate were 3.97 times and 9.96 times that of TiH_(2) and ZrH_(2),respectively,through the spherical pressure vessel.It indicated that the reaction reactivity and reaction rate of MgH_(2) were higher than that of TiH_(2) and ZrH_(2).In addition,to conduct in edepth theoretical analysis of ignition sensitivity and explosion severity,gas production and combustion heat per unit mass of ZrH_(2),TiH_(2) and MgH_(2) were tested by mercury manometer and oxygen bomb calorimetry.The experimental results revealed that MgH_(2) had a relatively high gas production per unit mass(5.15 mL/g),while TiH_(2) and ZrH_(2) both had a gas production of less than 2.0 mL/g.Their thermal stability gradually increased,leading to a gradual increase in ignition energy.Furthermore,compared with theoretical combustion heat,the combustion ratio of MgH_(2),TiH_(2) and ZrH_(2) was more than 96.0%,with combustion heat value of 29.96,20.94 and 12.22 MJ/kg,respectively,which was consistent with the explosion pressure and explosion severity test results.
基金the financial support of the National Institute for Occupational Safety and Health–United States(No.211-2014-60050)
文摘In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas flows across the gob and the working areas and may result in a condition where an oxygen deficient mixture or a methane accumulation in the gob flows into the face area. Computational Fluid Dynamics(CFDs) modeling was carried out to analyze this phenomenon and its impact on the development of an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the formation of Explosive Gas Zones(EGZs) are directly affected by atmospheric pressure changes. In the location where methane zones interface with mine air, EGZ fringes may form along the face and in the bleeder entries. These findings help assess the methane ignition and explosion risks associated with fluctuating atmospheric pressures.
