Numerical Study of the Effect of Different Transverse Fire Locations on Smoke Mass Flow Rate in Tunnel Fires

Wall restriction is an important factor affecting flame space development, air entrainment and heat transfer. To investigate the smoke characteristics in the one-dimensional horizontal spreading stage at different transverse fire locations in tunnel, FDS was used to simulate and analyze the smoke mass flow rate. The results show that the average smoke mass flow rate is positively correlated with distance from fire source to sidewall and heat release rate (HRR). The maximum smoke temperature rises decay exponentially along the longitudinal direction of the tunnel. Based on dimensional analysis, a prediction model is proposed to predict the average smoke mass flow rate in one-dimensional horizontal spreading stage in tunnel. For wall fires, predicted mass flow rate is 1.29 times of Zukoski model via generalizing the "mirror" effect. For non-wall fires, the dimensionless smoke mass flow is proportional to the 0.19 power of the dimensionless HRR. Besides, the reliability of the prediction model is verified by comparing with full-scale and reduced-scale experiments.