Study On Thermal Analysis, Ignition And Combustion Characteristics Of AP/HTPB Base Bleed Propellant

One of the commonly used methods to improve large-caliber artillery range is to design exhaust device in the bottom of the projectile. The working principle:high temperature gas is produced at the combustion of base bleed propellant, continuing going through the low-pressure recirculation zone from nozzle of stern. With increased pressure and reduced base drag, the target is achieved to increase projectile range. The most commonly used base bleed propellant is AP/HTPB. It is a kind of the high polymer adhesive and oxidant of dual-composition composite propellant.In this paper, based on the background of related content of base bleed projectile, mainly on the thermal decomposition, ignition and combustion of AP/HTPB base bleed propellant, experiments and numerical simulation are studied. The main contents are as follows:(1) Thermal decomposition experiments of the extinguished AP/HTPB base bleed propellant are carried by using DSC and TG-DTG at a heating rate of20℃/min and40℃/min, the experimental results are comparatively analyzed with the original AP/HTPB base bleed propellant and thermal decomposition characteristics are investigated. Based on thermal decomposition rate equation and Arrehenius equation, the kinetic parameters were estimated.(2) The high-temperature gas jet device is designed, the high-speed video system and the thermocouple temperature measuring device is used to study ignition delay characteristics and burning rate of AP/HTPB base bleed propellant under the effect of high temperature gas jet. The simplified model of ignition delay period and burning rate of AP/HTPB base bleed propellant is established, the theoretical calculation results are in good agreement with the experimental data.(3) The closed bomb test system is used to study the burning rate of AP/HTPB base bleed propellant in the pressure range of50～200MPa, the index formula of line burning rate and pressure is calculated. Based on genetic optimization algorithm, the optimization design model of burning rate is established and the calculation result is more close to experimental results.(4) Two dimensional unsteady mathematical model of the base bleed flow field under condition of transient depressurization is established and numerical simulation is conducted. The temporal-spatial distribution discipline of pressure, temperature, density and velocity of base bleed combustion chamber are obtained. It has certain reference value to control combustion stability of base bleed unit.