Study on combustion characteristics of cables with spacing arrangement under different external radiation conditions

Abstract

A series of experiments was conducted to explore the influence of cable spacing on combustion characteristics in real cable installation, considering various external radiation intensities (30, 50 kW/m²) and cable spacings (0, 2.5, 5 cm). A comparative analysis of the combustion characteristics (such as heat release rate (HRR), combustion gas, and mass loss) was conducted, and the HRR calculation for cables that were not fully filled in the sample tray was revised as well. It could be found that with the increasing radiation intensities, the peak concentrations of CO and CO₂ increased (O₂ concentration decreased), and the interval between the two peaks shortened. The HRR curves of cables with different spacings all presented two peaks under two radiation intensities. The max-peak HRR occurs at D_d = 2.5 cm, and the double max-peak HRRs are 582 kW/m² and 407 kW/m² under radiation intensities of 50 kW/m² and 35 kW/m², respectively. This is because when D_d = 0 cm, the thermal feedback effect between cables is relatively enhanced, while the air entrainment between the cables is weakened. When D_d = 5 cm, the thermal feedback effect is weakened. When D_d = 2.5 cm, both the air entrainment and the thermal feedback are strengthened, and the peak HRR occurs. The above results could provide data to support fire safety design and the emergency response to cable laying.