Estimation of Flow Properties of Gelled Fuels with Regard to Propulsion Systems

Gelled fuels and propellants are shear-thinning non-Newtonian fluids. Their dependency of the shear viscosity the shear rate can be described with sufficient accuracy by an extended version of the Herschel-Bulkley in the whole rocket and ramjet propulsion-relevant shear-rate range. Additionally to the analytically generalized Reynolds number for fluids, which follow the extended Herschel-Bulkley equation, a method the estimation of critical Reynolds numbers (as a phenomenological approach) is presented. Both dimensionless numbers are useful for the characterization of the flow and partially also of the spray processes of gel fluids. The results show furthermore that both the shear-thinning property and the yield stress tend to stabilize the laminar flow and thus shift the critical Reynolds number to higher values when compared to Newtonian liquids.