Particle combustion rates for mechanically alloyed Al–Ti and aluminum powders burning in air

Abstract

Mechanically alloyed aluminum-rich powders of Al–Ti (10, 15, 20, and 25 atom% of Ti) were produced and their combustion was compared to that of aluminum and titanium powders of comparable sizes. A laminar lifted-flame aerosol burner developed recently was used in this research. The aerosols were produced and burned in air. Measured flame speeds were higher for the aerosols of Al–Ti mechanical alloys than for the aerosols of pure Al or Ti. The particle combustion rates were evaluated based on the comparison of the measured and calculated profiles of the flame radiation. To calculate radiation profiles a simple model of particle combustion was used, in which both the radiation intensity and particle burn time were expressed as power functions of the initial particle size. For all the powders, the burning particle radiation intensity was observed to be best described by a function proportional to the cube of the initial particle size. For aluminum aerosol, the best match between the experimental and calculated flame radiation profiles was observed for the linear particle combustion law, when the particle combustion time, t, was expressed as a function of the initial particle size, d, as t [ s ] = 310 d [ m ] . To match the experimental and calculated flame radiation profiles for the Al–Ti mechanical alloys, the combustion times of individual particles could be described by either d 1 or d 2 expressions. The burning time of mechanically alloyed particles increased with the increase of titanium concentration. The overall combustion times for aluminum particles are significantly longer than those for mechanically alloyed particles of Al–Ti of the same size.