EFFECT OF OXIDIZER PARTICLE ORIENTATION ON BURNING RATES OF COMPOSITE PROPELLANTS

摘要

Regarding center-perforated composite solid propellant grains, the radial linear burning rate of the propellant often depends on its location in the web. In most cases, the burning rate at the middle of the web is highest along the radial direction. This deviation of the linear burning rate along the radial direction is called the midweb anomaly, the hump effect, and so on. The phenomenon is the result of multiple factors (e.g., orientation of oxidizer particles, existence of binder layers, and the effect of those factors on combustion and heat conduction in the solid phase). The physical cause of this phenomenon has not been understood in sufficient detail. In this study, the effect of oxidizer particle orientation on the burning rate is studied. The particle orientation in inert solid propellant grains is observed by micro-focus X-ray computerized tomography. To simplify the indefinite shape of actual ammonium perchlorate particles, simple cylindrical inert particles were mixed into inert propellant slurry. As a result the particle orientations were observed in center-perforated and solid cylindrical inert grains. The orientation of the particles seemed to be along the isochronous surface, which is formed during the casting process. One physical correlation between the particle orientation and the mean or local burning rate is investigated by numerical simulation from the point of view of the combustion surface configuration, which is formed by the different burning rates of the propellant ingredients. The results of the simulation suggest that the orientation of oxidizer particles in line with the burning direction increase the mean burning rate by forming and developing uneven surfaces.