Interactions among synthesis, rheology, and atomization of a gelled propellant

Abstract

Gelled propellants are alternative propellants for aerospace propulsion displaying favorable characteristics of the conventional solid and liquid propellants. Non-Newtonian rheology is their definitive characteristic. We examine the interactions among processing conditions, rheology, and atomization performance of gelled Jet A1 propellant. The knowledge of propellant rheology enables control over flow through the delivery system and the droplet size. Rheological measurements reveal a highly shear thinning but viscoelastic gel and facilitate the design of an atomizer to induce very high shear rates by the short time scale impingement of microjets of air. The atomizer could achieve instant breakup of the gel at low to moderate supply pressures. Complementary viscosity flow curves obtained from the pipe flow stage of delivery system revealed the extent of viscosity reduction prior to atomization and established the dependence of droplet size on the gel mass flow rate and viscosity. Our investigations show that high gellant concentrations and processing temperatures lead to the dominant expression of elasticity in the resulting gels and concomitant increase in droplet size.