Scaled experimental investigation of air curtain smoke confinement against stack effect in entrance/exit passageways

Fire-induced smoke movement in underground transportation facilities poses serious threats to occupant safety and ventilation efficiency. Entrance/exit passageways in metro stations, composed of alternating horizontal and inclined segments, exhibit complex buoyancy-driven flow behavior that challenges conventional smoke control strategies. In this study, the performance of air curtains as a sustainable and non-obstructive smoke control technology was experimentally investigated using a 1/10-scale platform. A series of controlled fire tests were conducted with systematic variations in heat release rate (HRR), passage inclination, nozzle slot width, injection angle, and air curtain position. The smoke-blocking efficiency E was used to quantify performance, and the interaction between jet momentum and buoyancy was characterized by the momentum ratio R . Results show that increasing HRR and slope angles intensify buoyant flows, thereby reducing E unless compensated by sufficient jet momentum. Slot width produced a non-monotonic effect due to coupled changes in jet velocity and flow rate, while the influence of injection angle became significant only after achieving jet stability. A critical threshold of momentum ratio, R c , was identified as the minimum requirement for preventing smoke penetration. The findings provide practical guidance for the design of energy-efficient, buoyancy-resistant ventilation systems in metro station passageways and similar semi-confined environments.