Study On Smoke Flow With Semi-transverse Smoke Extraction In Tunnel Fire

With the economic development and accelerated urbanization, subway, for its largetraffic volume, fast, punctual, safety, low energy consumption, easy traffic, and comfort,has been widely used around the world. At the same time, the subway fire accidentsoccur frequently, which has brought catastrophic losses to the society. Toxic and hightemperature smoke is the main factor to threaten the human lives, so that the smokecontrol in tunnel fire is the most critical thing. Currently, there are few studies of thesemi-transverse smoke exhaust, such as how to set up a smoke vent of semi-transversesmoke exhaust system, the specification has not yet provided, so the research on theproblems of the semi-transverse smoke exhaust has important theoretical significanceand practical engineering application value.This paper summarized the research experience and achievements of domestic andforeign tunnel semi-transverse smoke exhaust, and based on the project of ChongqingScientific Committee of "Subway Tunnel fire smoke control theoretical research"(CSTC2009BB6193) and the project of Chongqing Public security bureau scientificresearch of “Subway fire smoke flow and staff evacuation simulation”, and choose aSubway Interval Tunnel which is in Chongqing as a prototype, designing areduced-scale Subway Interval Tunnel model experiment table with the length of15mand the ratio of1:10according to Froude-number Model, then carry out a series of testsaiming at temperature distribution and smoke flow features of different fire powers, firelocations, opening smoke vent numbers, smoke exhaust volume fluxes and longitudinalair supply velocities in subway tunnel with the semi-transverse smoke exhaust.Contemporary Fire Dynamics Simulation software FDS has been employed to set upprimary size Subway Interval Tunnel model and make analog computation of the smokespread of different fire powers, smoke exhaust volume fluxes and smoke vent distances.The main work and results of research were shown as follows:①The shrunken size subway Tunnel model with the ratio of1:10consisting ofinterval tunnel and exhaust duct was installed according to Froude-number Model(semi-transverse smoke exhaust); and the test systems of temperature and velocity andfans of supply and return air were debugged.②The research results of the model test and numerical simulation indicated that:1) The best smoke exhaust speed of the semi-transverse smoke exhaust was linearly related to the cubic root of fire power.2) Under static condition, opening smoke ventscheme had little impact on tunnel ceiling temperature. When fire was located under asmoke vent, the smoke exhaust effect would be better with smoke vents above the fireopen and the best smoke exhaust speed of the fire power, while longitudinal air supplyvelocity was0. When fire was located between two smoke vents, the smoke exhausteffect would be better with smoke vents near downstream of the fire open and the bestsmoke exhaust speed of the fire power, while longitudinal air supply velocity waslongitudinal critical wind speed of the fire power.