PARTICLE SIZE EFFECTS ON CL20/GAP COMBUSTION: EXPERIMENTS AND THEORY

摘要

The present study deals with combustion characteristics of CL20/GAP propellants and particularly focuses on the influence of particle size on ballistics behavior. Combustion of CL20/GAP mixtures, with different CL20 particle sizes (5 to 300 μm), is experimentally studied by measuring burning rate via ultrasonic techniques. Experimental data obtained attest some significant size effects and distinctly show two regimes depending on particle size. For coarse particles, a high burning rate, high exponent mode is observed while with fine particles, a regime with lower burning rate and exponent is noticed. A comprehensive theoretical approach is used based on the sequential burning model. This model allows for a good prediction of propellant burning rate for coarse CL20. However, it fails for fine particle regime and overestimates pressure exponent, which hints that a non-sequential burning may occur. A possible scenario, relying on possibly enhanced particle/binder heat transfer that involves CL20 burning rate decrease, is then proposed: CL20 particles are actually thought to leave the surface virtually unreacted and burn only in gas phase. Development of an associated theoretical frame seems to confirm the proposed explanation and allows for a good prediction of the non-sequential regime.