Molecular Simulation For The Physical Properties Of The Gel Hydrazine Propellants

Hydrazine is a kind of good propellant, with the advantages of low viscosity and high combustion energy value. The gelled hydrazine propellants can reduce the high freezing point of hydrazine, and make it convenient for storage and transportation. Combustion adjuvant suspended in the gelled hydrazine propellants stably, which improve the overall energy and specific impulse value. In this study, hydroxyethyl cellulose(HEC) and carboxymethyl cellulose nitrate(CMCN) are chosen as the gels. Aluminum hydride(AlH3) with high density and high energy is chosen as the combustion adjuvant. The physical properties of hydrazine-gel/hydrazine-gel-AlH3 are studied by molecular dynamics(MD) and mesoscopic dynamics(MM) using Material Studio 6.0. The molecular interactions are analyzed to explain the change of the physical properties.At first, the hydrazine binary mixture systems with 10%(the quality percentage, as followed), 20%, 30% HEC/CMCN were built. Properties such as the density(D), the glass transition temperature(Tg) and structural mechanics performance were calculated. The radial distribution function(RDF) and the free volume fraction(FFV) between hydrazine and HEC/CMCN were analyzed to explain the change of the properties. From the results, the density of the gelled hydrazine propellants increased and FFV decreased as the HEC/CMCN content increase. The stronger attractive forces between HEC/CMCN and hydrazine were, the closer of the polymer chains, which leaded to the volume of those systems reducing. The gels miscible with hydrazine enhanced the structural strength of the propellants. The g(r) rose with the increase of the HEC/CMCN, which means the force of the interaction is large. The strong interaction force reduced the movement of the molecular chains, which leaded to the glass transition temperature increased.Second, the structural mechanics performance and the density of hydrazine-HECAlH3 systems were calculated. From the results of mechanics performances, the values of elastic coefficient matrix had large different, which means the ternary systems present stress anisotropy. As shown in density distribution of the AlH3, AlH3 were distributed around the gels mainly, due to the higher interaction between the HEC/CMCN and AlH3. The interaction energy between AlH3 and gelled hydrazine plays a crucial role in determining the compatibility. When the consent of the gels was 20%, the systems showed larger unit mass of energy, and the more AlH3 distributed around the gel.From the study results of binary and ternary systems, the value of all properties were similarly, which means that HEC and CMCN are suitable to improve the properties of liquid hydrazine. The findings demonstrate that molecular dynamics simulation method is a powerful technique for studying the influence of gels on the hydrazine.