Flammability Characterization of a Polysulfide Based Ramjet Fuel

Abstract

ABSTRACT This research program seeks to understand how the proportions of the fuel ingredients affect the ignition and decomposition characteristics of a novel solid ramjet fuel. The approach involves an ingredient mixture study that varies the proportions of three fuel components over a 10% range: epoxy cured polysulfide polymer, sulfur, and a perfluoropolyether. The primary objective of this work is to demonstrate the manipulation of the lower flammability limit and the thermal desorption species of the various formulations as a direct result of the doping fractions of sulfur and perfluoropolyether. Laboratory experiments include closed cup flash point testing and pyrolysis gas chromatography mass spectroscopy. The results show that, for the conditions investigated, both sulfur and perfluoropolyether act to decrease the lower flammability limit when added to polysulfide fuel. Low ignition temperature species including hydrogen sulfide are desorbed from sulfur-doped formulations. The mole fractions of diluent species decrease with the addition of either sulfur or perfluoropolyether. These experiments isolate the fundamental fuel properties by decoupling fuel behavior from combustor operating parameters such as geometry, chamber pressure, air temperature, and flux. Understanding relationships between the controlling mechanisms of solid fuel ramjet performance and fundamental fuel properties can aid in design prior to static firings.