Effects of Control Zone, Exhaust Rate and Station Extent on Smoke Dispersal during Emergency Concourse Fires in Underground Stations

Effective mass rapid transit plays an essential role in public transportation for sustainable urban development. This study investigates the temporary spreading behavior of smoke in the concourses of underground stations. The computational approach implements the software package FDS® 6.7.4 along with a post-processing visualization module (Smokeview) to simulate the smoke dispersal processes for determining the unsteady distributions of temperature and visibility during emergency concourse fires. The interfacial temperature between the lower air layer and upper smoke layer is employed to estimate the smoke layer height, as guided by NFPA-92B. The FDS predictions agree reasonably well with the measured fire plume temperatures at the heights of 7.0 m and 13.0 m above the fire source from the available literature in the time duration of 600 s for model verification. FDS calculations are then extended utilizing the validated computational model to explore the effects of the control area, exhaust rate and station size on the smoke spreading progressions. The simulated results reveal the effectiveness of installing static barriers to restrict smoke dispersal within a specific control space; however, the implementation of suitable mechanical exhaust system is required to extract the dense smoke out of the concourse. For the scenario of a high volume MRT underground station, the design adopting the smoke control area of 20 m × 15 m in conjunction with the exhaust rate of 15 m3/s can attain clear visibilities for emergency evacuation. However, the simulations show the inappropriateness of arranging the same design layout of control area and exhaust rate as safety measures of underground fires for a medium volume station.