Flame spread over cables in a utility tunnel: Effect of longitudinal wind and inclination angle

• The effect of longitudinal wind and inclination angle on cable fire was revealed. • A predicted model for cable flame spread rate was established. • The heat transfer process during the cable flame spread was discussed. Tables in utility tunnels pose a major fire hazard. This work aims to provide a comprehensive understanding of the effects of cable inclination angle and longitudinal wind ( U ∞ ) on the flame spread behaviors of cables in a utility tunnel. Flame inclination angle ( β ) increases with the increase of cable inclination angle and longitudinal wind speed, while the amplification decreases as the longitudinal wind speed increases. Both flame length ( x f ) and pyrolysis length ( x p ) increase linearly with sinθ when U ∞ is smaller than 0.65 m/s and they also increase with the increase of longitudinal wind speed. The increasing inclination angle and longitudinal wind speed contribute to the increasing flame spread rates. The flame spread rate accelerates significantly when the longitudinal wind speed and inclination angle are 0.65 m/s and 12° respectively. In addition, a model based on heat transfer analysis was established to predict the flame propagation rate under different cable inclination angles, and the experimental results were in good agreement with the predicted results. The results of the study contribute to cable fire risk assessment, which is beneficial for cable fire prevention and control in utility tunnels.