Combustion and Conversion Efficiency of Nanoaluminum-Water Mixtures

An experimental investigation on the combustion behavior and conversion efficiency of nanoaluminum and liquid water mixtures was conducted. Burning rates and chemical efficiency of aluminum-water and aluminum-water-poly(acrylamide-co-acrylic acid) mixtures were quantified as a function of pressure (from 0.12 to 15 MPa), nominal aluminum particle size (for diameters of 38, 50, 80, and 130 nm), and overall equivalence ratios (0.67 < φ < 1.0) under well-controlled conditions. Chemical efficiencies were found to range from 27 to 99% depending upon particle size and sample preparation. Burning rates increased significantly with decreased particle size attaining rates as high as 8 cm/s for the 38 nm diameter particles above approximately 4 MPa. Burning rate pressure exponents of 0.47, 0.27, and 0.31 were determined for the 38, 80, and 130 nm diameter particle mixtures, respectively. Also, mixture packing density varied with particle size due to interstitial spacing, and was determined to affect the burning rates at high pressure due to inert gas dilution. The presence of approximately 3% (by mass) poly(acrylamide-co-acrylic acid) gelling agent to the nAl/H2O mixtures had a small, and for many conditions, negligible effect on the combustion behavior.