Effects of oxygen concentration on combustion of aluminum in oxygen/nitrogen mixture streams

Abstract

The authors studied the ignition temperature of a solid cylinder of aluminum with an original oxide coating placed in a stagnation region of oxygen/nitrogen mixture streams over a wide range of oxygen concentration of the streams. The sample temperature during combustion and the flame structure of burning aluminum were measured. The burning rates of aluminum based on the experimental results were also estimated. The study showed, firstly, the ignition temperature of the aluminum sample was almost constant irrespective of the oxygen concentration when the sample was heated at a constant rate up to its ignition. Secondly, with an increase of the oxygen concentration, the peak positions of Al and AlO emissions shifted to the aluminum surface in the flame zone. Thirdly, the burning rates of aluminum depended on the sample temperature and slightly on the oxygen concentration. The mass transfer number of aluminum was much smaller than those of various hydrocarbon fuels in air.