Abstract: Experimental study of heavy naphtha combustion in tunnel under longitudinal ventilation was carried out in 1:10 reduced size tunnel model considering different fire heat release rates and longitudinal ventilation velocities. The longitudinal temperature distribution under the tunnel ceiling was measured, and the inclination angle of the flame was quantified. The results show that with the increase of longitudinal ventilation velocity, the temperature in the tunnel decreases as a whole, and the maximum temperature under the ceiling decreases gradually. Then an estimation model of the maximum temperature under the ceiling during heavy naphtha combustion in the tunnel under longitudinal ventilation is proposed. The inclination angle of flame increases with the increase of longitudinal ventilation velocity. When the longitudinal wind velocity is low (less than 1 m/s), the flame inclination angle increases obviously with the increase of longitudinal ventilation velocity. When the longitudinal wind velocity is faster (more than 1 m/s), the influence of the longitudinal ventilation velocity on the flame inclination angle is not obvious.

Key words: longitudinal ventilation, tunnel fire, heavy naphtha combustion, temperature profile, flame angle