BOUNDARY LAYER MODELLING OF THE HEAT TRANSFER PROCESSES FROM IGNITERS TO ENERGETIC MATERIALS

摘要

Current ignition models used in internal ballistics codes assume that heat transfer is primarily due to convection, and radiation in the case of electrothermal ignition. However, many other thermophysical and thermochemical effects in the boundary layer surrounding propellant grains play an important, if not a dominant, role in energy transfer leading to ignition. Modelling was conducted to estimate the heat transfer due to thermophysical and thermochemical effects within thermal boundary layers. Heat transfer by black powder combustion gases was compared with that due to condensing metal (copper) vapour. These heat transfer rates were then applied to propellant in order to predict ignition delay times, which were then compared to experimental ignition delay times. Convective heat transfer has also been estimated and direct comparisons made with heat transfer due to thermophysical and thermochemical effects.