Research On Combustion Mecharism Of Ultrafine Aluminum Nanocomposites Powder

Ultrafine aluminum nanocomposites powder is one kind of high performance composite materials with its surface coated or compounded to ensure its high-activity.With the characteristics of smaller size,larger specific surface area and imperfect surface coordinate bond,the chemical activity of nano-al powder increases significantly. The combustion performance of solid propellants and explosives may be significantly enhanced with nano-aluminum would be added as energetic materials. In this sense, it is scientifically justified to study the combustion properties and mechanism as well as its influencing of nano-aluminum powder.This paper presents a novel constant volume combustion system used for solid fuel burning test. Base on the system,The combustion properties of nano-aluminum was experimental studied base on the constant combustion system, as well computed with CHEMKIN package.The main results obtained are as follows:1) Set up a constant volume combustion system, with the work of designing,processing and checking the subsystem such as the burner, ignition system and test systems etc. Final results showed that this system is suitable for the experimental study of nano aluminum powder combustion mechanism.2) Base on the constant volume vessel, the influence of filling pressure to combustion performance of nano-Al particle was investigated by analyzing the flame structure, temperature and dynamic pressure in combustion vessel, as well as the microstructure and composition of combustion products. The experimental results showed that Al2O3 and AIN-polytypic were produced after the reaction between Al and air, and as the increase of ambient pressure, the reaction rate, as well as the peak pressure, increases. Also the time needs to reach peak pressure decreases, while the heat releases are roughly the same.3) Developing a quasi-steady-state nano-aluminum combustion model: the structure is composed of three combustion zones(inner, middle, and outer) bounded by four infinitesimally thin sheet which are the inner surface, the flame surface, the condensation surface and the outer boundary.Base on CHEMKIN,simulation was computed with the aluminum combustion mechanism including 8 components and 11 reactions. Results show that the higher the initial pressure, the faster the oxidant diffusion, the smaller the latent heat of vaporization,therefore,the faster the reaction rate. But pressure has no obvious effect for the generation of intermediate product. Similarly, the higher the initial temperature, the faster the oxidant diffusion, more steam produced from liquid aluminum evaporation, therefore,the faster the reaction rate. Unlike the pressure, the higher the initial temperature, the higher the intermediate generation peak and peak time appears earlier.