Full-scale experiment and CFD simulation on smoke movement and smoke control in a metro tunnel with one opening portal

• We carried out full-scale tests in a partly underground metro tunnel with one opening portal in Chongqing, China.
• The maximum temperature and temperature distribution under the metro tunnel ceiling were investigated during the tests.
• We conducted CFD simulations in the full-scale metro tunnel.
• The smoke movement characteristic was analyzed under mechanical ventilation situations.
• The evacuation routes decided by the operation modes of the emergency vents on the top of the tunnel were analyzed.

Three full-scale model experiments were conducted in a unidirectional tube, which is a part of a metro tunnel with one end connected to an underground metro station and the other end opened to outside in Chongqing, PR China. Three fire HRRs, 1.35 MW, 3 MW and 3.8 MW were produced by pool fires with different oil pan sizes in the experiments. Temperature distributions under the tunnel ceiling along the longitudinal direction were measured. At the same time, CFD simulations were conducted under the same boundary conditions with the experiments by FDS 5.5. In addition, more FDS simulation cases were conducted after the FDS simulation results agreed with the experimental results. The simulation results show that the smoke temperature and the decay rate of the temperature distribution under the tunnel ceiling along the longitudinal direction increase as HRR increases. The smoke exhausts effectively from the tunnel under mechanical ventilation system, whether the emergency vent is activated as a smoke exhaust or an air supply vent. The operation mode of the mechanical ventilation system depends on the evacuation route.