Study on smoke sealing effectiveness of the air curtain in exit bifurcated tunnel fires

Abstract

The feasibility of using a smoke prevention air curtain in the exit bifurcated tunnel was investigated through 1:10 scale model experiments. The results indicated that the jet velocity and heat release rate (HRR) significantly influenced the smoke sealing effectiveness of the air curtain. However, once the jet velocity reached a certain extent, the longitudinal fire location had a relatively limited effect on the smoke sealing effectiveness. Subsequently, numerical simulations were conducted to investigate the influence of the HRR, jet velocity, longitudinal velocity, and bifurcation angle on the smoke sealing efficiency of the air curtain. The simulations were based on the evacuation strategy of bifurcated tunnel under longitudinal ventilation, assuming no smoke backflow upstream of the fire. The findings revealed that the smoke sealing efficiency was positively correlated with the jet velocity, negatively correlated with the HRR and longitudinal velocity, and somewhat increased with the increase of bifurcation angle. Additionally, a prediction model was proposed for determining the optimal air curtain jet velocity in the bifurcated tunnel. This model was developed using dimensional analysis principles and taking into account various influencing factors, which can provide valuable insights for designing smoke control measures and enhancing safety in bifurcated tunnel fires.

Keywords

• Bifurcated tunnel
• Air curtain
• Smoke sealing efficiency
• Experiment
• FDS