Study On Energy Release Charcteristics Of Aluminum Particles And Aluminum-Based Solid Propellants

Aluminum-based solid propellants are the primary fuel in solid rocket motors（SRM）.The addition of aluminum to the solid propellants not only improves the specific impulse and the explosion of the propellant,but also restrains the instabilities of combustion in SRM solid engine.In order to fully understand the combustion process and combustion mechanisms of aluminum and aluminum-based solid propellants,and to grasp the effects of different factors on combustion,through experimental tests and theoretical analysis,the energy release characteristics of aluminum particles and aluminum-based solid propellants were carried out.The research in this work provides a theoretical basis for the engineering application of solid propellants.First,all of physical and chemical properties testing methods were used to test the physical and chemical properties of micron-sized aluminum particles and aluminum-based solid propellants.The differences in microstructure and composition among different samples were mastered.The thermal oxidation characteristics and kinetic parameters of different samples were obtained by thermal analysis.As the particle size of the sample decreased,the activation energy of the sample decreased,the initial reaction temperature decreased,and the thermal oxidation degree deepened.During the oxidation process,the oxide layer of aluminum particles is transformed from amorphous alumina throughγ-Al₂O₃ toα-Al₂O₃,and the thickness of the oxide layer also increases from 3.96 nm to 320.15 nm.The ignition test of three kinds of aluminum particles commonly used in propellants was carried out by laser ignition test systems.It was found that the smaller the particle size of the sample,the larger the spectral intensity and the more energy release.As the oxidbillity of the atmosphere increases,the ignition delay time gradually decreases,and the combustion temperature and the combustion intensity also increase.As the pressure increases,the maximum combustion temperature and heat release rate of the sample gradually increase.The combustion and agglomeration characteristics of the aluminum particles during flow under different atmospheres and different particle concentrations were studied using a dynamic combustion test system.The results show that as the particle size decreases,the particle concentration increases,and the oxidbillity of the atmosphere increases,the energy release characteristics of the aluminum particles in dynamic combustion are better,and the burnout rate is higher,but the agglomeration phenomenon is also more obvious.The thermal decomposition characteristics of the ternary solid propellants were mastered by thermal analysis.In the ignition test,as the pressure increases,the release rate of oxidizing atmosphere increased,so that the ignition delay time is shortened,the burning rate increased,and the maximum combustion temperature increased.Three different forms of condensed phase products（small smoke oxide particles、aluminum shell and large agglomerates）were obtained by off-line analysis.According to the diffusion reaction mechanism of aluminum particles,the physical model including the heat transfer and chemical reaction process of the particles is established.The effects of particle size,initial temperatures and pressure on the ignition delay time of aluminum particles were obtained by Matlab and Chemkin calculation.At the same time,the formation and transformation relationship of different intermediates in the gas phase reaction were obtained.Through the model calculation,the obtained ignition delay time results are compared with the foreign authoritative experimental data and models,and the accuracy is greatly improved.In summary,by systematically studying the energy release characteristics and influence rules of aluminum particles and aluminum-based solid propellants,it provides necessary data and theoretical support for engineering applications.