This study examines smoke spread in an underground mall fire under the composite smoke control mode of a smoke barrier and a mechanical smoke exhaust system. The objective is to optimize the selection of smoke containment and exhaust methods in an underground mall in Fuxin City, China. A Fire Dynamics Simulator was used for numerical simulation to investigate the effects of the sagging height and spacing of smoke barriers on smoke containment, as well as the effects of size, number, and arrangement of smoke vents in the mechanical smoke exhaust system on the effectiveness of smoke exhaust. The results indicated that a smoke barrier with a sagging height of 1 m and a spacing of 5 m was effective in preventing the spread of high-temperature smoke. When the sagging height of the smoke barrier increased to 1.2 m, the smoke barrier effect was comparable to that of a 1 m height barrier. Regarding the mechanical smoke exhaust system, the size of the opening area of the smoke vent had no significant effect on the smoke exhaust effect. The best smoke exhaust effect was achieved when the number of smoke vents was 12. Additionally, the double-row setting of smoke vents was more efficient than the single-row setting. Combining a smoke barrier and a mechanical smoke exhaust system can provide a more effective smoke control compared to either system alone. Comprehensively, considering the effectiveness and economy of smoke containment and exhaust, the optimal combination of smoke containment and exhaust was determined to be a smoke barrier with a sagging height of 1 m and spacing of 5 m, and a mechanical smoke exhaust system with 12 smoke vents in a double-row arrangement.

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A 1:10 scale model tunnel with a length, height and width of 9 m, 0.6 m and 0.8 m, respectively, was set up in this paper. A water curtain system was installed in the model to investigate the effect of water curtain systems on smoke flow and heat propagation. A reduced-scale experimental and theoretical study was carried out by varying the heat release rate of the fire source, the water curtain pressure, and the number of water curtain rows. A series of tests were carried out for various setups to quantify each mechanism of interaction between the water mist and hot smoke, to propose a method for qualitatively analysing water curtain systems blocking the propagation of heat radiation and the flow of smoke from combustion, and to propose a method for predicting heat fluxes. The study found that the pressure of the water curtain, the number of rows, and the heat release rate of the fire source all had an effect on the smoke blocking effect of the water curtain system. This effect decreased as the heat release rate of the fire source increased and increased significantly with the pressure of the water curtain and the number of rows. The smoke blocking effect was quantified using conservation of momentum by establishing a dimensionless parameter R to represent the ratio of water curtain momentum to smoke momentum, as well as the ratio of heat flux before and after the water curtain to represent the smoke blocking capacity $$\delta$$ δ of the water curtain. The smoke blockage rate $$\delta$$ δ ranges between 40 and 75%, and the smoke blockage rate increases as the momentum R increases. Finally, in tunnel fires, a predictive model for the attenuation of heat radiation by water curtains has been developed, providing theoretical support for the quantitative study of the smoke and thermal blockage effects of water curtains, which is beneficial to the protection of human life in confined spaces.