Computational estimation on the propulsion performance of polycyclic hydrocarbons

Abstract

Polycyclic hydrocarbons have great potential as advanced high-energy-density (HED) fuels, and their physicochemical and propulsion properties are highly important for propulsion purposes. In this work, the fuel properties including density, melting point, boiling point, critical temperature/pressure, enthalpy of vaporization, enthalpy of fusion, enthalpy of combustion and specific impulse of three families of polycyclic hydrocarbons (a, cyclopropyl and methyl-substituted derivatives of tri-, tetra- and penta-cyclic hydrocarbons; b, [n]prismanes; and c, homocubanes) were evaluated by combining the group contribution and quantum chemical methods. The applied method properly predicts the physicochemical properties of polycyclic hydrocarbons, which are highly dependent on their molecule structures. For category (a), the hydrocarbons with low H/C ratio generally have higher density, volumetric specific impulse and volumetric combustion heat. Importantly, for all three families of polycyclic hydrocarbons, introducing additional strained rings (cyclopropyl ring or cyclobutyl ring) in molecules remarkably improves their density and specific impulse, which are highly appropriate for volume-limited aerospace vehicles to extend the flight range and increase the payload. The study on the relationship between the propulsion performance and structure characteristics of these hydrocarbons will give the general rule for the rational design of HED fuels.