Effect of ambient temperature on the ignition and combustion process of single aluminium particles

This experimental work aims to examine the effects of ambient temperature on the ignition and combustion process of single aluminium particles (40-170 μm). Ambient temperatures considerably influence the particle ignition delay time, but the influence on the combustion time is limited. Particle ignition probability is very sensitive to the ambient temperature. The particle ignition probability can be improved by approximately 6.7 times by increasing the ambient temperature by approximately 300 K. As the diameter increases, the ignition probability increases firstly and then decreases in the experimental conditions of Cases 02-06. The diameter ranges for the particle ignition probability of >90% in the experimental conditions of Cases 03-06 can be extended by the high ambient temperature. Moreover, the aluminium particles with high unevenness level can be ignited easily, which should be resulted from the local flame near the raised part. The characteristic particle temperature is measured using the method of two-colour pyrometry. Experimental results show that the aluminium particle in these experimental conditions can barely burn in a pure diffusion-limited regime. The structure and components of the oxide film on the unignited particle show that the oxide film fracture is a key process for particle ignition.