Effect of nano particle addition on the regression rate of liquefying fuels

Abstract

Inclusion of solid additives such as metals or metal hydrides in hybrid rocket fuel formulations introduces the possibility of substantial increase in the specific impulse and density impulse performance. Moreover certain nanometer sized particles with proper surface treatment have the potential to enhance the mechanical properties of the fuel grain. Despite their advantages, powders with micrometer or nanometer sized particles could have an adverse effect on the regression rate of liquefying fuels. A substantial compromise in the regression rate is highly undesirable, since it could force the designer to the use the multiport grain approach. Since the viscosity of the melt layer has the most dominant influence on the entrainment regression rate, establishing the rheology of the paraffin wax based suspensions is the primary objective of this paper. The study focuses on a commonly used paraffin wax grade, FR5560, blended with a micron sized aluminum powder and a nanoclay powder typically used to reinforce thermoplastics. The viscosity measurements revealed that the effect of the micron size aluminum power on the viscosity is small even at high concentrations such as 60% by mass. It is also determined that the nanoclay has a much more pronounced effect on the suspension viscosity, resulting in a 10 fold increase in viscosity at a concentration level of 30% by mass. The results indicate that formulations with the micron size aluminum powder would retain the high regression rates of the neat paraffin wax. On the contrary, a significant drop in the regression rate for the nanoclay based formulations is expected.