Performance Analysis of Novel Propellant Oxidizers using Molecular Modelling and Nozzle Flow Simulations

Search for alternate fuels for improvement in rocket engine performance is a topic of ever-growing interest and discussion in the research community. The primary target of this paper is to present novel compounds in view of their possible use as oxidizers in propulsion applications using molecular modeling calculations and supersonic flow simulations. Carbon-based heterocyclic compounds tend to have strained molecular structures leading to high heats of formation and energetic behavior. In the present work, molecular modeling calculations for molecules of 37 such potential propellant oxidizers are presented. Density functional theory (B3LYP) was employed for the geometry optimization of the proposed molecular structures using the 6-311++G(d,p) basis set.
Heats of formation of the compounds were calculated using the molecular modeling results. Appropriate propellant compositions were considered with the proposed compounds as oxidizer components and Ideal specific impulse (Ivac,ideal*) was calculated for each composition assuming isentropic flow, computed using the NASA CEA software package. To predict the actual delivered specific impulse (Ivac,act*), supersonic nozzle flow simulations of equilibrium product gases of each propellant composition have been carried out using OpenFOAM. The standard k-epsilon turbulence model for compressible flows including rapid distortion theory (RDT) based compression term, has been employed. As the problem is inherently transient in nature, local time stepping (LTS)
methodology has been further implemented to reach a steady-state solution. These simulations accounted for divergence losses, turbulence losses and boundary layer losses and gave a more realistic estimation of the specific impulse. It was observed that the Ivac,act* for all propellant compositions lie between 88% to 91% of the corresponding ideal value. The newly proposed oxidizers showed considerable improvement in propulsion performance as compared to ammonium perchlorate which is currently the most widely used oxidizer in solid rocket motors. The maximum improvement observed in Isp was 24 s.