Experimental Study on Aluminum Dust Flame in Quenching Distance

A new experimental apparatus that can produce Aluminum dust flames stabilized in a Pyrex tube (L=˺̄1،5 m, d=˽̄4،5 cm) has been constructed. The quenching distance in aluminum dust clouds of particle size d32=˺́18 µm (Sauter mean diameter, d32) have been measured in a wide range of concentrations. Aluminum dust flow, which goes up in vertical Pyrex tube was ignited at the open end. Constant pressure flames propagating downwards were observed. Three different stages of flame propagation were observed: laminar, oscillating, and turbulent accelerating flames. It was found that in fuel-rich dust-oxygen-nitrogen and dust-oxygen-argon mixtures, the quenching distance is a very weak function of dust concentration. At the same time, the dependence of the quenching distance on oxygen concentration and type of carrier gas is observed. As a result, the minimum quenching distance is found to be about3 mm in air and decreases to 1 mm in mixtures of ˼˹̃ O30%. The substitution of nitrogen for argon in air decreases the minimum quenching distance from 4 to2 mm. The lean flammability limit for (˻˺̃ O211%N79%) is95 gr/m3 which decreases to90 gr/m ˼ for (˼˹̃ 30%O2 ، 70%N2) and increases to205 gr/m3 for (˻˺̃21%O2 ، 79%̃ Ar).

Keywords:

Quenching Distance , Flame , Concentration , Oxidizer and Aluminum