Droplet combustion studies on two novel energetic propellants, an RP-1 surrogate fuel, and their blends

Abstract

Droplet combustion behaviour of an RP-1 surrogate fuel (RP-1-s), its constituents, and two novel energetic fuels – 1,3-bishomocubane dimer (BHCD) and bis(nitratomethyl)-1-3-bishomocubane (DNMBHC) was investigated. The novel energetic fuels, envisioned as potential fuels in rocket propulsion were observed to be completely miscible with RP-1-s. Experiments were also conducted on a 10% w/w mixture of BHCD in RP-1-s (BHCD10) and a 10% w/w mixture of DNMBHC in RP-1-s (DNMBHC10). Tests were carried out under ambient atmospheric conditions using the suspended droplet method. The combustion behaviour of RP-1-s as characterized by the burn rate constants and flame dimensions was found to lie between those of its constituent fuels – methylcyclohexane (MCH), n-dodecane, and isocetane. Condensed phase pyrolysis leading to droplet swelling and eventually microexplosion were observed for both BHCD and DNMBHC, and their blends with RP-1-s. DNMBHC was found to combust almost 3.5 times as fast as RP-1-s while BHCD was found to combust slightly slower than RP-1-s. Both BHCD and DNMBHC were found to be extremely sooty as compared to RP-1-s. The intensity of sooting is however expected to be much lower in an actual scenario where liquid oxygen would be used for combustion, and the droplet sizes are small. The potential of the novel energetic compounds DNMBHC and BHCD to serve as additives to RP-1-s for performance enhancement was assessed to be worthy of further exploration.