Study on rheological properties of composite propellant slurry in the mixing process by using experimental and numerical simulation

Researchers have extensively focused on the safety of the solid propellant preparation process, particularly the mixing process that was deemed critical for the safety of the entire procedure. Herein, the rheological curves of propellants at different stages of mixing are obtained experimentally. The obtained curves are fitted using the Herschel-Bulkley non-Newtonian model. CFD calculations were performed using this data, allowing us to obtain the pressure and velocity evolution within the fluid domain during mixing. Such calculations are then used to assess the variation in the homogeneity of the mixture over time. Experimental evidence reveals that the viscosity of the composite propellant slurry is 32 Pa s after the addition of fine-grained ammonium perchlorate (AP). The propellant slurry tends to be 15 Pa s at the end of mixing. Both the morphology and elemental analysis of the slurry demonstrated that the fine AP is more distributed near the coarse AP. In contrast, the aluminum powder is distributed more evenly within the propellant matrix. Moreover, theoretical simulation input parameters are obtained using the Herschel-Bulkley model fitting. Numerical simulation results show that the paddle and the inner wall are more prone to a sudden increase in pressure and velocity concentration due to the shear effect, and the mixing homogeneity and safety analysis of the propellant slurry can be visualized in a short time period.