Effects of particle size of CL-20 on its thermal decomposition and combustion characteristics

As one of the typical high-energy components, CL-20 exhibits a particle size effect that the burning rate of CL-20 based propellant increases significantly with the increase of particle size within a certain pressure range. However, the essential mechanism of the particle size effect is still not clear. In this work, the influence and mechanism of particle size effect for CL-20 on its thermal decomposition and combustion are studied. The three types of CL-20 samples with the particle size distributions of 8.07–206.07 μm are adopted in the experiments. These CL-20 particles mainly display spindle-shaped and prickle-shaped structure. With the increase of particle size, the trigger condition for thermal decomposition becomes more difficult and the ignition delay time increases. Three-dimensional carbon skeletons are generated during the thermal decomposition of CL-20 particles. The carbon skeletons derived from small particles are scatted while those derived from large particles are connected into a whole. The combustion mode of large CL-20 particles is more inclined to porous medium combustion. Consequentially, it is pointed out that the essence of the particle size effect is the difference in the stability of the three-dimensional cage-like structure for CL-20 crystals with different particle sizes.