Study on temperature distribution and CO diffusion induced by cable fire in L-shaped utility tunnel

Abstract

Numerical simulation study was conducted to investigate temperature distribution and CO diffusion induced by cable fire in a L-shaped utility tunnel. The maximum ceiling temperature in region I of tunnel decreases as horizontal distance from the fire source rises, while temperature in region II first increases and then decreases. Larger cable inclination angle (θ) leads to lower temperature in region I, while the conclusion is reverse in region II. An equation is proposed to predict maximum temperature rise along the tunnel ceiling. As vertical height rises, the maximum temperature above the fire source first drops and then rises for larger inclination angle. The vertical maximum temperature increases as fire source power or ventilation velocity rises under most conditions. For stable fire, the CO concentration shows "V-shaped" variation with a change in horizontal distance from the fire source under most conditions. The CO concentration is higher when the ventilation is conducted compared with no ventilation condition. The influences of fire source power on the CO concentration is not obvious. The low CO concentration area significantly increases to half of region I as inclination angle rises to 4°. Research results will contribute to fire hazard evaluation and safety design of utility tunnels.