Investigation on ignition and combustion of a single Al and Al-Li alloy particle in hot oxidizing gas

Aluminum-lithium (Al-Li) alloy particles significantly accelerate ignition and suppress agglomeration, achieving optimized energy release within limited residence time compared against conventional Al particles. In this study, a series of flat flame experiments were performed to systematically investigate and compare the ignition and combustion characteristics of a single Al and Al-Li alloy particle with Li concentrations ranging from 2.5 wt.% to 10 wt.%. The ignition delay time, the micro-explosion delay time, and the combustion time were accurately measured by a developed image processing program through tracing the RGB chromatic information and cluster number of particles. Compared to Al particles, Al-Li alloy particles demonstrate observably reduced ignition delay time due to the preferential reaction of Li. Meanwhile, the addition of Li triggers the micro-explosion events, and their frequency shows a monotonic increase with higher Li concentrations and elevated ambient temperatures. The Al-Li alloy particles exhibit shorter combustion time than Al particles, and micro-explosion further accelerates the combustion process. Based on the experimental results, four predictive formulas of ignition delay time, micro-explosion delay time, normal combustion time and micro-explosion combustion time are established as functions of particle size, Li concentration, and ambient temperature. Furthermore, the combustion products from Al and Al-Li alloy particles were collected, and it was found that micro-explosion markedly decreased the product size and improved the combustion efficiency of particles.