Energetic nano-sized particles have been shown to have a great potential for use in the aerospace propulsion applications. Some of the unique combustion properties of nano-particles such as very rapid ignition and short combustion times make them particularly valuable for propulsion systems; they can be included in solid fuels, solid propellants, or even as energetic gellant in liquid systems. However, due to the novelty of the application and rapid development of production techniques, there is no comprehensive understanding of what characteristics of a nano-sized particle are important in contributing to desirable performance and ease of processing into a final usable form. Previous studies have shown that HTPB-based solid fuels containing various types of nano-sized particles showed differing performance results when tested in the same hybrid rocket motor under identical conditions. Many of these particles have data available only on the basic composition (aluminum, boron, boron carbide, etc.), average diameter, and/or BET surface area. In order to better understand and correlate observed combustion behavior with intrinsic material properties, the particles of interest need to be better characterized. A variety of standard particle characterization techniques were applied to the fifteen types of particles examined in this study and the results tabulated. Some of the parameters measured were average particle diameter, specific surface area, amount of active content, and oxide layer thickness. Trends in propulsion performance measured using a parameter of great interest to the hybrid rocket community (fuel mass burning rate) in general matched trends in particle characteristics (i.e. active content, surface area), but there were some noticeable exceptions. This study indicates that there is still much more to learn about the correlation between physical and chemical properties and measured combustion performance. Other parameters that should be examined in the future include particle size distribution, degree of agglomeration, reactivity and thermal effects (oxidation rate, onset temperature for oxidation exotherm, heat release associated with any excess stored energy), etc.

Characterization of nano-sized particles for propulsion applications

Nanosized aluminum (16% by weight) was added into JP-10 and surfactant (2% by weight) was used to reduce the agglomeration of nanoparticles. Combustion of metalized fuel, as well as pure JP-10, was carried out in a small-scale combustor. The oxygen-to-fuel ratios were set to be 1.7, 1.8, and 1.9, respectively. An additional trial of water injection during combustion was also tested. The pressures at the combustion chamber and nozzle exit, along with the thrust, were measured during the combustion; and intervals of true values of the specific impulse were presented. The results showed that a relatively higher combustion efficiency was achieved with JP-10-based slurry by 3.0 to 9.0% when compared to pure JP-10. However, the specific impulse could be increased only when the combustion-induced heat release was improved enough to overcome the two-phase loss. Depositions at different positions were collected after combustion for deep analysis; and the results of the x-ray diffraction, thermogravimetry analysis,...

Anthony Hall

Papers

Gelled RP-1 Nanophase Aluminum Propellant