Smoke Control Strategy and Design Criterion in Tunnel Fire Hazards Using Point Extraction Ventilation: Experimental Analysis and Theoretical Modeling

The hot and toxic smoke is a major reason for deaths and injuries in tunnel fire hazards, therefore, it is of vital importance for safe evacuation to effectively control the smoke. This paper proposed a smoke control strategy, i.e., completing smoke extraction, and developed the design criterion of exhaust rate based on small-scale experiments and theoretical analysis. The heat release rate (HRR), damper length, and interval were considered. Experimental results showed the critical exhaust rate for completing smoke extraction rose with the increase in HRR and declined with a growing damper interval. Besides, it first rapidly decreased and then turned to be smooth with rising damper length. Subsequently, the ratio of the suction force, F_d to the force, F_s was adopted to determine the completing smoke extraction using force analysis. The results illustrated that the HRR and damper interval barely affect the relative magnitude between the suction force, F_d, and the force, F_s. It was linearly dependent on the dimensionless damper length and then exponentially grew. The critical length of the damper was 0.1 m. Finally, a prediction model was established, and the evaluated results deviated from the experimental data within 15%.