Abstract
Many pollutants are generated during tunnel fires, such as smoke and toxic gases. How to control the smoke generated by tunnel fires was focused on in this paper. A series of experiments were carried out in a 1:10 model tunnel with dimensions of 6.0 m × 1.0 m × 0.7 m. The purpose was to investigate the smoke layer thickness and the heat exhaust coefficient of the tunnel mechanical smoke exhaust mode under longitudinal wind. Ethanol was employed as fuel, and the heat release rates were set to be 10.6 kW, 18.6 kW, and 31.9 kW. The exhaust velocity was 0.32–3.16 m/s, and the longitudinal velocity was 0–0.47 m/s. The temperature profile in the tunnel was measured, and the buoyant flow stratification regime was visualized by a laser sheet. The results showed that the longitudinal ventilation leads to a secondary stratification of the smoke flow. In the ceiling extract tunnel under longitudinal ventilation, considering the research results of the smoke layer height and the heat exhaust coefficient, a better scheme for fire-producing pollutants was that an exhaust velocity of 1.26–2.21 m/s (corresponding to the actual velocity of 4.0–7.0 m/s) should be used. The longitudinal velocity should be 0.16–0.32 m/s (corresponding to the actual velocity of 0.5–1.0 m/s).
Highlights
The terrain environment in different regions was usually distinct
Smoke Layer Height Changes The finite-current motion in stably stratified fluids and turbulent shear flow in stratified fluids was mThenetfiionnieted-c[u35rr]e, nwtitmhoatmiopnliitnudsteabmlyotsitornatdifeiefidnefdluaidssl:and turbulent shear flow in stratified fluids was mentioned [35], with amplitude motion defined as l: The concept of buoyancy frequency for t∂∂∂∂htt2e222llrm==aglg∂∂s∂∂zztρρralltification, and the buoyancy frequency refers to theTrhaetecofnchepant goef obfubouyoaynacnycyfrienqtuheenvcyertfiocraltdhierremctaiol nstprraotipfiocsaetdio[n3,6a],ntdhethfoermbuolayaisn:cy frequency refers to the rate of change of buoyancy in the vertical direction proposed [36], the formula is: Usually, the fire plume could be always (c(−o−nggsi∂∂∂d∂ρρzezsrs/eρdaρa)as2)t12he ideal gas (ρsTs the ρ ρ Equation (3) becomes: Usually, the fire plume could be always considered as th1e ideal gas ( ∂(1/T(z)) 2
The discharge of pollutants from tunnel fires was investigated by the scale-model
Summary
The terrain environment in different regions was usually distinct. The complex terrain environment leads to inconvenient traffic conditions in the region. In order to investigate the longitudinal ventilation mode, Memorial tunnel studied this mode early, the results showed that the control effect of smoke in the tunnel was not good because there was almost no longitudinal wind in the tunnel This phenomenon was the balance between air supplement and smoke exhaust in the full transverse smoke exhaust system. In order to investigate the ceiling smoke extraction, the Zhejiang Provincial Transportation Planning and Design Research Institute of China and Central South University jointly carried out scientific research to jointly tackle the key technologies of central smoke extraction, structure fire resistance, and the concentrated smoke exhaust schemes in independent smoke exhaust pipes of highway tunnels [9] They used a combined mode of tunnel operation shaft with jet fan, and the concept of central smoke extraction with independent smoke exhaust pipes at the top in tunnel fires [10]. Based on the analysis of the buoyancy plume structure, the smoke layer height, and the exhaust efficiency, the characteristics and ventilation scheme of smoke exhaust were determined
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