Study On The Characteristics Of Smoke Propagation For Highway Tunnel With Central Smoke Extraction Systems

Along with our country’s comprehensive national power being enhanced, the tunnel construction is developing rapidly. Highway tunnel with central smoke extraction systems has gradually become the body of the construction of highway tunnel, compared with the longitudinal ventilation tunnel, the capture velocity of Centralized smoke tunnel is less than the longitudinal ventilation tunnel.So natural sedimentation could be maximum sustain what is benefit for escape of people. Thermal parameters of roof, temperature field, concentration distributions of space have important influence to the design of enclosure structure and escape of people. The temperature and concentration decay in tunnel is worthy to be discussed.In this paper, the model of two-layer zone of reversed flow at centralized exhaust ventilation is build and steady-state differential equations are established and solved according to the law of conservation of principle. Then dimensionless smoke flow differential equation of the upstream region are released, further with centralized smoke tunnel smoke diffusion distance equation obtained.For the fire of heavy truck, the center and near the wall of2different fire source positions are considered to predict thermal parameters near fire hazard tunnel roof by CFD software think over the character of flame and the methane as fuel different combination of different jet fan and exhaust fan. Moreover the thesis gives out dimensionless correlation standard of the value and vocation of the highest temperature and concentration and flame length under the roof as air supply dimensional velocity at upstream and induced velocity at downstream change.Based on the research of diffusion characteristics of fire smoke in central exhaust tunnel temperature and concentration and vertical attenuation at upstream and downstream are analyzed. Horizontal and vertical attenuation amplitude and their relation of temperature and concentration three outlet positions are obtained, with the dimensional equation of corresponding parameter as air supply dimensional velocity at upstream and induced velocity at downstream change.In the finality, the problems requiring further studies are discussed.