Study on the smoke sealing efficiency of air curtain and maximum ceiling temperature rise under longitudinal ventilation in bifurcated tunnel

Due to the ever-growing development and construction of municipalities, the underground tunnel structures raises the probability of traffic accidents and the fire risks. The effects of different longitudinal ventilation velocities and air curtain spouting angles (ASA) on the temperature distribution and maximum ceiling temperature rise in a scaled bifurcated tunnel were investigated experimentally and numerically with different heat release rates. Induced by synergistic effect of longitudinal ventilation and air curtain, the maximum ceiling temperature in the fire zone was shifted. The high temperature ranges of ceiling expanded as ASA increased. The smoke sealing effect (SSE) of different ASA ranged from 0.6 to 0.82, and the 15 degrees showed a more stable SSE. Besides, based on the Li model, the factor theta of ASA was introduced for predicting the maximum ceiling temperature rise, which is consistent with the experimental data. Comparison between the experiments and the simulations showed good agreement.