Study On Pyrolysis,Ignition And Combustion Characteristics Of Several Typical Hydrogen Storage Materials

Hydrogen storage materials as a solid rocket propellant component or additive has been widely concernedcan,which can effectively improve the solid rocket propellant energy level.However,the hydrogen storage material itself ignition and combustion characteristics have not yet been fully revealed.In this paper,an experimental system of ignition of hydrogen storage material based on laser radiation ignition was set up.Several typical hydrogen storage materials were ignited and burned experimentally.The minimum ignition power,ignition delay time,rapid heating rate,Surface temperature distribution,combustion flame color and structure,flame evolution and combustion mechanism.The content of this paper includes:(1)Research on ignition and combustion characteristics of metal hydride.The ignition experiments were carried out on the two kinds of metal hydrides,Al H3 and Mg H2,respectively,under natural convection conditions at normal temperature and pressure.The experimental results of Al H3 showed that aluminum hydride decomposed after heated by laser,the first released hydrogen was ignited and showed a light blue flame,and the precipitated aluminum was heated and melted by the laser and the gas phase flame.The temperature remained almost unchanged during the melting.Then aluminum particles were gasified and combustion,dispersed in the hydrogen flames;Finally,the sample away from the laser and quenching occurs.With the laser ignition power density increased,the ignition delay time of aluminum hydride got shorten.The experimental results of Mg H2 show that the combustion process under laser irradiation includes the stages of thermal decomposition,hydrogen combustion,elemental combustion of magnesium and quenching.Magnesium hydride rapidly raises and decomposes hydrogen and magnesium elements under the action of laser light.The hydrogen combustion presents a light blue flame,and the elemental magnesium melts at the same time.The molten elemental magnesium is gasified under the combined action of laser radiation and hydrogen combustion heat feedback,The stress causes the powder to crumble;at the same time,gaseous magnesium undergoes a gas phase reaction upon exposure to oxygen,deflagrates and produces a yellow flame.As the laser ignition power density increases,the ignition delay time of magnesium hydride shortens,and the faster the deflagration occurs,the more deflagration times.(2)Study on Ignition and Combustion Characteristics of Complex Hydride.Thelaser ignition and combustion experiments of Al(BH4)3·n EDA(n = 1,2,3)were made,we can know that the ignition delay time is very short,about 2.0ms,and the minimum ignition energy is about 0.3~0.5m J.There are three consecutive stages for the combustion process of Al(BH4)3·n EDA,including dehydrogenation,hydrogen and impurity combustion,dehydrogenation skeleton combustion;the combustion products mainly include CO2 and H2 O,excluding NO2.(3)Borane hydrogen storage materials ignition and combustion characteristics.Laser ignition experiments were carried out on three methylamine borane respectively.The experimental results show that the dimethylamine borane is not easy to ignited,a trimethylamine borane ignition and combustion process are similar,including thermal decomposition,gas ignition,diffusion combustion and quenching stage;A The borane is thermally decomposed and ignites in the gas phase.Under natural convection,the combustion becomes violent and the flame front expands outward.As the material is depleted,the combustion stops.Monomethylamine borane combustion process in the blue flame,compared with trimethylamine borane,monomethyl amine borane combustion process more stable.