Numerical studies on flow behavior of composite propellant slurry during vacuum casting

Rockets are powered by composite solid propellant, which is a heterogeneous system consisting of solid oxidizer and metallic fuel dispersed in a polymeric fuel binder matrix. The slurry casting technique under vacuum/gravity condition is well-established for performing a different class of large sized case bonded rocket motors. During propellant casting, the flow rate of slurry is a very critical parameter as it affects the product quality. The casting rate is governed by sufficient degassing and viscosity buildup due to the progress of cure reaction. In the present study, casting rate and casting time have been numerically evaluated for fixed and varying percentages of valve opening, different viscosity of slurry, and different pressure drop (driving force). The velocity profile of propellant slurry inside feeding pipe and valve has also been evaluated. Furthermore, to get a flawless grain and to predict the slurry casting rate, a microscopic analysis has been carried out to model the flow behaviour of composite propellant slurry, where the momentum conservation law has been applied to express the mathematical model in an analytical form. The resulting differential and algebraic equations have been solved numerically using MATLAB, computing software. The numerical analysis is useful for designing new casting set-up and for giving the idea of maximum casting rate, which is achievable for given casting set-up and rheological properties of propellant slurry.