Effects of Ambient Temperature on Micro-Explosion Dynamics and Combustion Characteristics of Single Al-Mg-Li Particles in Hot Oxidizing Gas Flow

Micro-explosion during combustion of aluminum-based alloy particles fragments the Parent particle into multiple Child particles, thereby modifying the particle size distribution and subsequent combustion process. However, the quantitative relationship between micro-explosion characteristics and combustion enhancement under hot oxidizing conditions remains insufficiently clarified. In this study, high-speed imaging combined with automated particle tracking was used to investigate the micro-explosion and combustion behavior of single Al-Mg-Li particles in a premixed CH₄/air/O₂ gas flow at four ambient temperatures of approximately 900 ~ 1200 K. Particles were classified as micro-explosion particles (Parent/Child) or non-micro-explosion particles (Normal), and a parameter framework including micro-explosion probability (P), averaged fragmentation ratio (F_r), micro-explosion delay time (MDT), Child-particle acceleration (a-Child), and total combustion time was established. The results show that micro-explosion was the dominant disruptive combustion mode under all investigated conditions, with p = 74.58% ~ 82.08%. With increasing operating condition severity, P, F_r, and a-Child generally increased, while the MDT shifted toward shorter and more concentrated distributions. The mean MDT decreased from 423 μs in Case 1 to 331 μs in Case 4, and the median MDT decreased from 400 μs in Case 1 to 300 μs in Cases 2 ~ 4. The Child-particle combustion time was also shortened, with the median value decreasing from 600 μs to 300 μs. Compared with Normal particles, micro-explosion particles generally exhibited shorter total combustion times, with median reductions of 9%, 0%, 13%, and 9% from Case 1 to Case 4, respectively. These results indicate that micro-explosion tends to shorten the combustion duration of Al-Mg-Li particles, although this effect is not strictly monotonic with operating temperature and is also affected by fragmentation ratio, Child particle size distribution, and micro-explosion intensity. The established parameter framework and equivalent combustion time methodology provide a quantitative basis for evaluating micro-explosion-induced combustion enhancement of metal particles under engine-relevant conditions.