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建立了镁颗粒群着火的一维非稳态有限影响体模型,数值模拟颗粒群中镁颗粒的着火过程.研究表明,当镁颗粒表面反应加剧之后,颗粒相温度急剧上升,迅速达到着火,而其周围气相的温升速率却远小于颗粒的温升速率;在着火过程中气相温度只在颗粒表面附近升高比较明显,整体温度升高不大.分析了颗粒群内部参数和环境参数对镁颗粒群着火的影响.随颗粒浓度的增加,颗粒群变得易于着火,其着火时间变短,但颗粒浓度增大到一定程度后,继续增大该值将对颗粒群的着火起消极作用.环境压力对颗粒群着火的影响比较小,在1—5 atm范围内颗粒群的着火性能基本不变.气相中氧气浓度对颗粒群的着火性能影响也不显著,但当氧气浓度过小时,对着火过程的影响将大大增强.颗粒粒径、气相/颗粒相初温、辐射源温度对颗粒群着火的影响巨大,小粒径、高温度促使颗粒群快速着火.数值模拟与文献中试验结果的变化趋势相一致.
A one-dimensional unsteady finite element model of the ignition of magnesium particles was established to simulate the ignition process of magnesium particles in the particle swarm. The results show that when the surface reaction of magnesium particles aggravates, the temperature of the particle phase rapidly increases and reaches the ignition rapidly The rate of temperature rise around the gas phase is far less than the rate of temperature rise of the particles.The temperature of the gas phase rises only in the vicinity of the particle surface during the ignition process and the overall temperature rise is not significant.The effects of internal parameters and environmental parameters on the magnesium With the increase of the particle concentration, the particle group becomes easy to ignite and the ignition time becomes shorter, but after the particle concentration increases to a certain extent, continuing to increase the value will have a negative effect on the particle group’s ignition. The effect of ambient pressure on the ignition of the particle swarm is relatively small, and the ignition performance of the particle swarm is basically unchanged in the range of 1-5 atm.The oxygen concentration in the gas phase has no significant effect on the fire performance of the particle swarm, but when the oxygen concentration is too low, The impact of ignition process will be greatly enhanced.Particle size, the initial phase temperature of the gas phase / particle phase, the temperature of the radiation source on the particle group fire a huge impact, small particle size, high temperature to promote rapid particle swarm Ignition.Numerical simulation is consistent with the trend of the test results in the literature.