Comments on: “Combustion of nano-sized aluminum particles in steam: Numerical modeling”, by V.B. Storozhev and A.N. Yermakov

Abstract

This comment points out the large discrepancy between the predictions of the recently published model by Storozhev and Yermakov (Storozhev and Yermakov, Combust. Flame 162 (2015) 4129–4137) and the large body of accumulated literature on aluminum combustion. Their model predicts burning times between 40-63 ms for a cloud of nanometric aluminum particles (20 or 50 nm) burning in steam at initial temperatures around 2300 K. These predictions are roughly two orders of magnitude larger than the measured combustion times of micron and submicron aluminum particles from various experiments, which are on the order or hundreds of microseconds to milliseconds. Experimentally measured flame speeds of aluminum flames in the products of hydrocarbon flames, and the burn rates of metal-water propellants, also point to much faster burning rates of aluminum particles in steam than predicted by this model. As such, the predictions of the model by Storozhev and Yermakov cannot be reconciled with the available experimental evidence.