No abstract

No abstract

Steady-state strand burner and laboratory-scale static fire motor experiments were used to determine the relative performance and viability of an environmentally friendly solid propellant composed of only nanoaluminum and frozen water. The nominal size of the nanoaluminum particles was 80 nm. The particles were homogeneously mixed with water to form pastes or colloids and then frozen. The measured parameters include burning rates, slag accumulation, thrust, and pressure. A system scaling study was performed to examine the effect of the size of the smallscale motors. The equivalence ratio was fixed at 0.71 for the strand burner and the laboratory-scale motor experiments. The effect of pressure on the linear burning rate was also examined. For an equivalence ratio of 0.71, the mixture exhibited a linear burning rate of 4.8 cm∕s at a pressure of 10.7 MPa and a pressure exponent of 0.79. Three motors of internal diameters in the range of 1.91-7.62 cm were studied. Grain configuration, nozzle throat diameter, and igniter strength were varied. The propellants were successfully ignited and combusted in each laboratory-scale motor, generating thrust levels above 992 N in the 7.62-cm-diam motor with a center-perforated grain configuration (7.62 cm length) and an expansion ratio of 10. For the 7.62 cm motor, combustion efficiency was 69%, whereas the specific impulse efficiency was 64%. Increased combustion efficiency and improved ease of ignition were observed at higher chamber pressures (greater than 8 MPa). Recent advances in nanosized energetic particles have enabled their use as major ingredients in propellants with enhanced properties and performance [17-23]. In the current investigation, the performance and viability of nanoaluminum (nAl) and ice (ALICE) propellants were examined. Safety tests such as electrostatic discharge, mechanical tensile tests, and impact tests have been performed and are reported elsewhere [24]. Both steady-state strand burner experiments and laboratory-scale hot-fire motor experiments were employed to obtain ballistics data. Linear and mass burning rates, slag accumulation, effect of motor size, thrust, and pressure

No abstract

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.

No abstract

No abstract

No abstract