• Droplet-scale combustion and spray physics dominate multiple studies from the 1950s to the 1970s, covering single-drop burning, evaporation, and droplet combustion dynamics in oxidizing environments [1], [5], [6], [7], [10], [12].

• Flame structure, radiation, and temperature fields serve as core diagnostics for flame behavior, illustrated by structural/radiative studies on hydrocarbon flames [8], [11], [15].

• Supersonic/high-speed combustion phenomena emerge as a recurring focus across mid-century symposia, highlighting challenges, reactions, and flow interactions in fast flames [2], [5].

• Combustion instability and explosion phenomena are explored through theoretical instability analyses and broader explosion phenomenology in early combustion conferences [14], [19].

• Heterogeneous and multicomponent fuels, along with soot and particulate processes, show a pattern of increasing fuel complexity and heterogeneous reaction zones in combustion research [13], [18].