Experimental study on the influence of layer number and initial ignition location on burning characteristic of multi-layer cable fire

A series of multi-layer cable fire tests were conducted to explore the effects of cable layer number and initial ignition location on the burning characteristics and propagation behavior. Characteristic parameters, such as flame morphological characteristics, flame spread behavior, temperature profile and heat release rate (HRR) were determined. Flame height and HRR was significantly increased with the increase of cable layer number. Within the current limited experimental range, maximum flame height and HRR of multi-layer cable fire scenario reached 640 cm and 1380 kW, respectively. Also, initial ignition location had obvious effect on multi-layer cable fire propagation pattern. In cable fire scenarios, flame spread exhibits upward, downward, and horizontal directions when ignition initiates at lower or upper layers. However, mid-layer ignition introduces a critical thermal melt droplet-driven propagation mechanism. Molten droplets are classified into four morphological types, and their accumulation may lead to pool-like fires. This work was performed to deepen our fundamental understanding of the combustion characteristics of large-scale multi-layer cable fires and provide some reference for related fire safety issues.