Combustion of Nanoaluminum and Water Propellants: Effect of Equivalence Ratio and Safety/Aging Characterization (original) (raw)
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Feasibility Study and Demonstration of an Aluminum and Ice Solid Propellant
45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2009
Aluminum-water reactions have been proposed and studied for several decades for underwater propulsion systems and applications requiring hydrogen generation. Aluminum and water have also been proposed as a frozen propellant, and there have been proposals for other refrigerated propellants that could be mixed, frozen in situ, and used as solid propellants. However, little work has been done to determine the feasibility of these concepts. With the recent availability of nanoscale aluminum, a simple binary formulation with water is now feasible. Nanosized aluminum has a lower ignition temperature than micronsized aluminum particles, partly due to its high surface area, and burning times are much faster than micron aluminum. Frozen nanoscale aluminum and water mixtures are stable, as well as insensitive to electrostatic discharge, impact, and shock. Here we report a study of the feasibility of an nAl-ice propellant in small-scale rocket experiments. The focus here is not to develop an optimized propellant; however improved formulations are possible. Several static motor experiments have been conducted, including using a flight-weight casing. The flight weight casing was used in the first sounding rocket test of an aluminum-ice propellant, establishing a proof of concept for simple propellant mixtures making use of nanoscale particles.
Effect of nano-aluminium in plateau-burning and catalyzed composite solid propellant combustion
Combustion and …, 2009
Nano-aluminium particles of 50nmsize,producedatthislaboratory,areaddedtocompositesolidpropellantsbasedonammoniumperchlorateandhydroxyl−terminatedpoly−butadienebinderthatexhibitplateauburningratetrendsandthoseincludingburningratecatalysts.Thenano−aluminizedpropellantburningratesarecomparedwithcorrespondingmicro−aluminizedandnon−aluminizedonesinthe1−12MPapressurerange.Themid−pressureextinctionofthematrixescontainingthefine−sizedammoniumperchlorateparticlesinthepropellantalongwiththebinderisinvestigatedinallthecasestounderstandthemechanismofplateau−burning.Further,thevariationsinaluminiumcontent,thealuminiumsize(withinnano−andmicro−ranges),bimodalcombinationofnano−andmicro−aluminiumareconsidered.Ferricoxideandtitaniumdioxidearetheburningratecatalystsconsidered.Largescaleaccumulationofaluminiumisobservednotonlyinmicro−aluminizedmatrixes,butalsoinnano−aluminizedonesasclustersof1−5lmsize.Sincealuminiumisaddedattheexpenseofthecoarseammoniumperchlorateparticlestopreservethetotal−solidsloadinginthepresentformulations,additionofmicroaluminiumdecreasestheburningrate;whereas,nano−aluminizedpropellantsexhibit50 nm size, produced at this laboratory, are added to composite solid propellants based on ammonium perchlorate and hydroxyl-terminated poly-butadiene binder that exhibit plateau burning rate trends and those including burning rate catalysts. The nano-aluminized propellant burning rates are compared with corresponding micro-aluminized and non-aluminized ones in the 1-12 MPa pressure range. The mid-pressure extinction of the matrixes containing the fine-sized ammonium perchlorate particles in the propellant along with the binder is investigated in all the cases to understand the mechanism of plateau-burning. Further, the variations in aluminium content, the aluminium size (within nano-and micro-ranges), bimodal combination of nano-and micro-aluminium are considered. Ferric oxide and titanium dioxide are the burning rate catalysts considered. Large scale accumulation of aluminium is observed not only in micro-aluminized matrixes, but also in nano-aluminized ones as clusters of 1-5 lm size. Since aluminium is added at the expense of the coarse ammonium perchlorate particles to preserve the total-solids loading in the present formulations, addition of microaluminium decreases the burning rate; whereas, nano-aluminized propellants exhibit 50nmsize,producedatthislaboratory,areaddedtocompositesolidpropellantsbasedonammoniumperchlorateandhydroxyl−terminatedpoly−butadienebinderthatexhibitplateauburningratetrendsandthoseincludingburningratecatalysts.Thenano−aluminizedpropellantburningratesarecomparedwithcorrespondingmicro−aluminizedandnon−aluminizedonesinthe1−12MPapressurerange.Themid−pressureextinctionofthematrixescontainingthefine−sizedammoniumperchlorateparticlesinthepropellantalongwiththebinderisinvestigatedinallthecasestounderstandthemechanismofplateau−burning.Further,thevariationsinaluminiumcontent,thealuminiumsize(withinnano−andmicro−ranges),bimodalcombinationofnano−andmicro−aluminiumareconsidered.Ferricoxideandtitaniumdioxidearetheburningratecatalystsconsidered.Largescaleaccumulationofaluminiumisobservednotonlyinmicro−aluminizedmatrixes,butalsoinnano−aluminizedonesasclustersof1−5lmsize.Sincealuminiumisaddedattheexpenseofthecoarseammoniumperchlorateparticlestopreservethetotal−solidsloadinginthepresentformulations,additionofmicroaluminiumdecreasestheburningrate;whereas,nano−aluminizedpropellantsexhibit80-100% increase in the burning rate under most conditions. The near-complete combustion of nano-aluminium close to the burning surface of the propellant provides heat feedback that controls the burning rate. Midpressure extinctions of matrixes and plateau burning rates of propellants are washed out when nano-aluminium is progressively added beyond 50% in bimodal aluminium blends, but low pressure-exponents are observed in the nano-aluminized propellant burning rates at elevated pressures. Adjusting the plasticizer content in the binder alters the pressure range of plateau burning rates in non-aluminized propellants. Catalysts increase the burning rate by 50−10050-100% in non-aluminized and micro-aluminized propellants, but in nano-aluminized propellants, the lm-sized catalyst does not affect the burning rate significantly; whereas, the nanometre size catalysts increases the burning rate merely by 50−1005-15%.
A survey is offered of the present status of microaluminized propellants industrially used worldwide in most space applications, but new directions are also pointed out making profitable use of the nanoaluminized formulations currently tested in many propulsion laboratories. Different industrialand research-type solid rocket propellants, of the well-known family oxidizer/Al/inert binder, were characterized up to 70 bar. The oxidizer was AP, AN or a mixture of the two, while the inert binder was typically HTPB. In general, the tested propellants feature the same nominal composition but implement different grain size distributions of the oxidizer and/or metal fuel. The basic properties of all formulations are compared to those of a standard composite propellant certified for flight.
Pre and post-burning analysis of nano-aluminized solid rocket propellants
Aerospace Science and Technology, 2007
Nano-aluminized propellants are investigated and compared with corresponding micro-aluminized propellants in order to evaluate the actual pros and cons in the use of metal nano-powders for solid rocket applications. A detailed characterization of the original metal powder and condensed combustion products is performed and discussed. Under the explored operating conditions, the results confirm that nano-aluminized propellants show larger steady burning rate, without significant change in pressure sensitivity, and lower aggregation/agglomeration phenomena in combustion products. Combustion efficiency is in turn favored by those factors reducing the importance of aggregation/agglomeration phenomena in the combustion process.
Nano Aluminum Energetics: The Effect of Synthesis Method on Morphology and Combustion Performance
Propellants, Explosives, Pyrotechnics, 2011
Nanoscale aluminum based energetic composites were prepared using polytetrafluoroethylene (PTFE) as an oxidizer, and optimized according to the maximum experimentally observed flame propagation rate in an instrumented burn tube. Optimization of the aluminum-based composites was performed using nanometric aluminum from two manufacturers, Argonide Corporation and Novacentrix, and the combustion results represent the first direct comparison of these two materials in a burn tube configuration. Argonide aluminum was found to consist of many fused spheres of nano aluminum mixed with some larger micron sized particles. Novacentrix aluminum consisted of spherical particles with a closer particle size distribution. The propagation rate optimized wt.-% aluminum powder values were 50 and 44.5 for Novacentrix and Argonide, respectively. At the optimized conditions, the time to steady propagation for both Argonide and Novacentrix were similar, however the startup time for the Novacentrix based mixtures was more sensitive to changes in the mixture ratio. The presence of micron sized aluminum and lower surface area, but higher active content in the Argonide mixtures resulted in lower propagation rates, pressurization rates and peak pressures but higher total impulse values. It was found that peak pressure is not the sole determining factor in propagation rate, but the highest pressurization rates correlate with propagation rate.
Combustion of Bimodal Aluminum Particles and Ice Mixtures
International Journal of Energetic Materials and Chemical Propulsion, 2012
The combustion of aluminum with ice is studied using various mixtures of nano-and micrometersized aluminum particles as a means to generate high-temperature hydrogen at fast rates for propulsion and power applications. Bimodal distributions are of interest in order to vary mixture packing densities and nascent alumina concentrations in the initial reactant mixture. In addition, the burning rate can be tailored by introducing various particle sizes. The effects of the bimodal distributions and equivalence ratio on ignition, combustion rates, and combustion efficiency are investigated in strand experiments at constant pressure and in small lab-scale [1.91 cm (0.75 in.) diameter] static firedrocket-motor combustion chambers with center-perforated propellant grains. The aluminum particles consisted of nanometer-sized particles with a nominal diameter of 80 nm and micron-sized particles with nominal diameters of 2 and 5 µm. The micron particle addition ranged from 0% to 80% by active mass in the mixture. Burning rates from 1.1 (160 psia) to 14.2 MPa (2060 psia) were determined. From the small scale motor experiments, thrust, C * , Isp, and C * and Isp efficiencies are provided. From these results, mechanistic issues of the combustion process are discussed. In particular, overall lean equivalence ratios that produce flame temperatures near the melting point of alumina resulted in considerably lower experimental C * and Isp efficiencies than equivalence ratios closer to stoichiometric. The substitution of micron aluminum for nanometer aluminum had little effect on the linear burning rates of Al/ice mixtures for low-mass substitutions. However, as the mass addition of micron aluminum increased (e.g., beyond 40% 2-µm aluminum in place of 80-nm aluminum), the burning rates decreased. The effects of bimodal aluminum compositions on motor performance were minor, although the experimental results suggest longer combustion times are necessary for complete combustion.
Combustion of micro aluminum–water mixtures
Combustion and Flame, 2013
An experimental investigation on the combustion behavior of micro-sized aluminum (lAl)-water mixtures was conducted. It was easily ignited and self-deflagrated on lAl and liquid water when using a paper shell tube. Linear burning rates of quasi-homogeneous mixtures of lAl and liquid water as a function of pressure, mixture composition, density and environment gas medium were measured. Steadystate burning rates were obtained at room temperature using a windowed vessel for a pressure range of 1-80 bar in a nitrogen atmosphere, particle size of 0.5 Â 30 Â 30 lm and overall mixture equivalence ratios from 0.67 to 2.0. The pressure exponent was obtained as 0.47 at room temperature and compared to the case of nano-sized aluminum (nAl) and liquid water. When a wire was inserted into the sample, for increasing local heat transfer, burning rates were found to be faster.
Overview of Al-based nanoenergetic ingredients for solid rocket propulsion
Defence Technology, 2018
The introduction of nano-sized energetic ingredients first occurred in Russia about 60 years ago and arose great expectations in the rocket propulsion community, thanks to the higher energy densities and faster energy release rates exhibited with respect to conventional ingredients. But, despite intense worldwide research programs, still today mostly laboratory level applications are reported and often for scientific purposes only. A number of practical reasons prevent the applications at industrial level: inert native coating of the energetic particles, nonuniform dispersion, aging, excessive viscosity of the slurry propellant, possible limitations in mechanical properties, more demanding safety issues, cost, and so on. This paper describes the main features in terms of performance of solid rocket propellants loaded with nanometals and intends to emphasize the unique properties or operating conditions made possible by the addition of the nano-sized energetic ingredients. Steady and unsteady combustion regimes are examined.