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Gao Z.H.,Hefei University of Technology | Ji J.,Hefei University of Technology | Ji J.,Key Laboratory of Building Fire Protection Engineering and Technology of MPS | Fan C.G.,Hefei University of Technology | And 2 more authors.
Tunnelling and Underground Space Technology | Year: 2016

Smoke layer interface height is an important parameter in fire safety science. In this paper, a series of experiments were conducted in a 1/6th scale model tunnel for determining the smoke layer interface height in medium scale tunnel fire scenarios. The commonly used approaches, including visual observation, N-percentage rule and integral method are reviewed firstly. Then, considering the subjectivity and empiricism of previous approaches, a buoyancy frequency method is put forward based on the vertical temperature distribution in tunnel, which has definite physical meaning and eliminates the subjectivity of previous methods. The smoke layer thicknesses determined by buoyancy frequency method are compared with the results of visual observation, N-percentage rule (N = 10, 20, 30) and integral ratio method, respectively. The comparison results reveal that the smoke layer thicknesses determined by buoyancy frequency method fit best with the visual values for all the experimental conditions. While the calculated values by integral ratio method are lower than the visual values. In addition, the selection of optimum N values for the N-percentage rule in different cases is also discussed. © 2016 Elsevier Ltd. Source

Ji J.,Anhui University of Science and Technology | Wan H.,Anhui University of Science and Technology | Li K.,Anhui University of Science and Technology | Li K.,Wuhan University of Science and Technology | And 3 more authors.
International Journal of Heat and Mass Transfer | Year: 2015

Numerical simulations were carried out to study the smoke behaviors induced by fires in inclined tunnels with different slopes and the upstream maximum temperatures along the tunnel centerline were specifically focused. The simulation results show that the longitudinal centerline peak temperature occurs at the downstream region of fire source rather than right above the fire source. Two typical behaviors were found during the quasi-steady state: the upstream smoke layer interface is almost parallel to horizontal level while the downstream smoke layer interface is parallel to the inclined tunnel ceiling. The upstream maximum temperature under the ceiling remain approximately constant near the fire sources and then drop progressively with increasing distance to fire source due to the existence of vortexes, which is fairly different from the downstream maximum temperature distribution. Hence, an empirical correlation is developed by taking into account the tunnel slope, heat release rate and the upstream maximum temperature and using dimensional analysis. The correlation indicates that the dimensionless upstream maximum temperature decreases as the distance from fire source increases and it is proportional to 0.56 power of the dimensionless heat release rate and its relationship with tunnel slope is nonlinear and non-monotonous. © 2015 Elsevier Ltd. All rights reserved. Source

Chen C.-K.,University of South China | Chen C.-K.,Key Laboratory of Building Fire Protection Engineering and Technology of MPS | Zeng J.-W.,University of South China | Shen B.-Y.,University of South China
Journal of Central South University | Year: 2015

Twenty tests were conducted to investigate the efficiency of the intumescent coating designed to protect steel plate at the elevated temperature, by means of electrical furnace. And the factors of the initial thickness of coating and temperature of electrical furnace were considered. The high temperature response behavior of the intumescent coating was observed. And the expansion form of ultrathin intumescent coating and the temperature of the steel plate (TS) were obtained. Besides, the heat flux from expansion layer to steel plate versus time was analyzed in order to evaluate the heat transfer effect of intumescent coating on steel plate. The experimental results show that the response behaviors of the coating subjected to fire could be divided into four phases: stabilization phase, foaming expansion phase, carbonization-consumption phase and inorganic layer phase. And the net heat flux to the steel plate decreased observably in the foaming expansion phase, while the surplus white inorganic substance, which is the residue of the intumesced char layer in the inorganic layer phase under the condition of the temperature of the electrical furnace (TEF) beyond 700 °C over 1 h, has little effect on fire protection for the steel plate. © 2015, Central South University Press and Springer-Verlag Berlin Heidelberg. Source

Zhang G.,China University of Mining and Technology | Zhang G.,Key Laboratory of Building Fire Protection Engineering and Technology of MPS | Zhang G.,China Mobile | Zhu G.,China University of Mining and Technology | And 3 more authors.
Safety Science | Year: 2016

A risk assessment method was proposed to evaluate the evacuation safety in the collapse of a large steel-structured gymnasium caused by localized fire. The criterion for safety evacuation was that the available evacuation time was greater than the required evacuation time, which could be determined by a proposed steel-temperature rise model and a proposed evacuation model, respectively. In the proposed steel-temperature rise model, not only the effects of smoke thermal radiation and convection, but also the effects of flame thermal radiation on steel components were considered. In the evacuation model, the required evacuation time was determined mainly by the following factors: distance from the farthest point to the safety exit, personnel evacuation speed, width of evacuation exit, and density of personnel. All these results and experimental data obtained in this study provide valuable references to fire simulation, hazard assessment, and fire protection design. © 2016 Elsevier Ltd. Source

Chen C.-K.,Hunan Institute of Technology | Zhu C.-X.,Hunan Institute of Technology | Liu X.-Y.,Key Laboratory of Building Fire Protection Engineering and Technology of MPS | Yu N.-H.,Key Laboratory of Building Fire Protection Engineering and Technology of MPS
International Journal of Heat and Mass Transfer | Year: 2016

Sealing the tunnel entrance is a common tactic for tunnel fire fighting, while it is not easy to seal the two entrances synchronously in actual tunnel fire-fighting process. A set of reduced experiments were then conducted to investigate the effect of asymmetrical sealing of tunnel entrances on tunnel fire behavior and temperature distribution. The data of temperature, radiative heat flux and mass loss rate, etc. were acquired. The results demonstrate that hot smoke region shifts to the side not completely sealed, and burning at the side with less sealing ratio is more violent with higher smoke temperature and longer hot smoke plume. Plume temperature at the tunnel entrance could reach to 300°C as measured in the experiments and jet flame was observed at the end not completely sealed. These would lead to great danger to fire fighters in actual tunnel fire fighting. © 2015 Elsevier Ltd. All rights reserved. Source

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