粉末燃料冲压发动机内镁颗粒群着火模型

Ignition model of pulverized magnesium particle cloud in powdered fuel ramjet

对粉末燃料冲压发动机中镁颗粒群的着火过程进行了研究,建立了镁颗粒群的非稳态着火模型,数值模拟了镁颗粒群的着火过程。研究表明,颗粒相温度先缓慢升高,表面反应加剧之后,温度才急剧上升,很短时间内着火成功;而着火过程中气相温度整体升高不大,其温度总是低于颗粒相温度且升温很慢,特别是着火阶段后期,气相的升温速率远小于颗粒相的升温速率,分析了各种参数变化对颗粒群着火的影响。随颗粒浓度的增加,颗粒群的着火时间缩短;但当颗粒浓度太大时,颗粒群将不能着火成功。气相中氧气浓度对着火的影响很小,特别是颗粒浓度大的情况,氧气浓度对着火几乎没有影响。辐射源温度和气相初始温度对颗粒群着火的影响很大,两者的温度高,则颗粒群着火时间将大大缩短,但当颗粒浓度很高时,气相初温变化对颗粒群着火时间的影响将不再显著。颗粒粒径对颗粒群着火的影响较复杂,颗粒浓度大时,小颗粒颗粒群易于着火,而颗粒浓度小时,大颗粒颗粒群着火时间更短。

The ignition process of pulverized magnesium particle cloud in powdered fuel ramjet was studied.An unsteady ignition model of magnesium particle cloud was established.Behavior of ignition of magnesium particle cloud was numerically simulated.The studies show that the temperature of particle phase rises slowly firstly,after the surface reaction accelerated,it rises rapidly and soon ignites successfully.However,The gas temperature rises unobviously during the ignition process,its temperature rises slowly and is always lower than the particle phase temperature,especially in the end stage of the ignition process,the rising rate of gas temperature is much slower than that of particle phase.The effects of various parameters on the ignition of magnesium particle cloud were analyzed.The ignition time delay of particle cloud was reduced with the increase of particle phase concentration.However,when the particle concentration is too large,the particle cloud will not be able to ignite successfully.The effect of oxygen concentration in the gas phase on ignition of particle cloud is unsignificant,oxygen concentration has almost no effect on the ignition time delay especially when the particle concentration is huge.The radiation source temperature and the initial temperature of gas phase have great influences on the ignition of particle cloud.If these two temperature increase,the ignition time of magnesium particle cloud would be significantly reduced.But when the particle concentration is very high,the effect of initial temperature of gas phase on ignition of particle cloud will be no longer significant.The effect of particle size on ignition of particle cloud is complex.When the particle concentration is huge,the small size particle cloud will be easy to ignite.When the particle concentration is small,the ignition time of big size particle cloud will be short.