Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusi...Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.展开更多
The objective of this work is to investigate the influence of smoke movement during mine fires on miner evacuation behaviors. A three-dimensional computational fluid dynamics method was conducted to reconstruct the la...The objective of this work is to investigate the influence of smoke movement during mine fires on miner evacuation behaviors. A three-dimensional computational fluid dynamics method was conducted to reconstruct the lane- way conveyor belt fire scenes under two ventilating conditions. The parameters, including temperature-time histories, soot density, carbon monoxide and heat release rate, were simulated to characterize the mine fires at various ventilating speeds. A miner evacuation model affected by fire smoke movement was advanced to describe the miner evacuation behaviors, which can be divided into three stages. Based on the evacuation model coupled with the mine fire smoke movement, the available safety evacuation time for miners involved in coal mine fire located in different sites was estimated. Two evacuation patterns were advanced according to the ventilating speeds combined with the model of miner evacuation behaviors. The results show that the miners located between the inlet-air end and the air door in lane 1 should be evacuated to the inlet-air end and other miners involved in coal mine fire could choose the air door as the escaping destination, when the ventilation speed is greater than 3 m/s. Accordingly, the research can be used as references for the mine safety administration authorities to design the safety evacuation.展开更多
In this study,experimental and numerical simulation methods were combined to simulate the changing course of the temperature and velocity fields in nine different fire scenes. The characteristics of smoke movement in ...In this study,experimental and numerical simulation methods were combined to simulate the changing course of the temperature and velocity fields in nine different fire scenes. The characteristics of smoke movement in shafts with different fire source position factors(h/H) were quantitatively investigated,and the non-dimensional fitting function between the fire source position factors and the maximum temperature was deduced. The results showed that the location of the neutral plane moved upward as the fire source rose,and all the generated smoke spread to the upper areas;however,there was barely any smoke in the lower areas. The maximum temperature was inversely proportional to the fire source position factor;the higher the source position is,i.e. the higher the ratio factor is,the lower the maximum temperature is in the shaft. The experimental verification of the fire dynamics simulator(FDS) showed good results.展开更多
Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal...Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal of the tunnel follows aW-shaped distribution.The congestion situation does not allowfor immediate longitudinal smoke exhaust at the early stage of the fire,and the natural spread of smoke is complicated.An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident,employing the fire dynamics software FDS,considering five slopes and four fire locations.The simulation results reveal that the layer of high-temperature smoke becomes thicker as one gets closer to the fire source.The thermal pressure difference significantly impacts the temperature distribution within the tunnel and the distance of smoke spread.The value of the thermal pressure difference is significantly affected by changes in slope.It reaches a maximum of 157 Pa at a 5%slope,while it is only 41 Pa at a 1%slope when the fire occurs at the V-point.Fire hazards vary across locations within the W-shaped tunnel,necessitating separate consideration of the V-point and inverted V-point fire characteristics.The mass flow rate in small and large slope tunnels shows different decay rates due to variations in the main forces acting on the movement.Hence,two equations have been developed to predict the smoke mass flow rate,indicating a nonlinear relationship with the tunnel slope and the distance fromthe fire source.The tunnel slope inversely affects the smoke mass flowrate at the same location.The results can be utilized as a reference for conducting evacuation operations and aiding rescues during aW-shaped tunnel fire.展开更多
Wave motion in subway or tunnel fire is an intrinsic property of smoke.As the pressure of smoke changes with mass of certain power,a kind of linear wave equation for smoke can be derived from the conservation equation...Wave motion in subway or tunnel fire is an intrinsic property of smoke.As the pressure of smoke changes with mass of certain power,a kind of linear wave equation for smoke can be derived from the conservation equations of its mass and momentum,under nearly homogeneous zone assumption.The smoke movement of 4 subway fires was simulated with Airpak.By fitting the pressure-mass functions to the simulated data,wave equations of the smoke were derived,and wave motions of smoke were thus validated.It can be seen that smoke wave is a kind of mass wave,whose velocity is inversely proportional to smoke mass,and wave of a bigger fire propagates slower.展开更多
Objective Embryonic movements （EM） and angiogenesis pathways are evolutionarily conserved mechanisms which are essential for proper embryonic development. Deviations in these processes by exposure to cigarette smoke...Objective Embryonic movements （EM） and angiogenesis pathways are evolutionarily conserved mechanisms which are essential for proper embryonic development. Deviations in these processes by exposure to cigarette smoke condensate （CSC） may cause vascular and morphogenetic disorders. Methods Using chicken and mouse embryos, we have demonstrated the in vivo effects of CSC on EM, vascular development, and organogenesis. Results Examination of the CSC exposed chicken embryos revealed a significant reduction in EM, stunted growth, deviated pattern of blood vessels, hemorrhages, and localized necrosis. Likewise, mouse embryos that were exposed to CSC at E8.5 and E9.5 died between E11.5 and E12.5, respectively. These mouse embryos showed defects in morphogenesis and remodeling of the embryonic vasculature, while littermate controls showed normal development. Conclusion Cigarette smoking during pregnancy is fatal for growing embryos. CSC may induce the remodeling of embryonic vasculature, leading to various pathologies.展开更多
基金Project(U1134203)supported by the Major Program of the National Natural Science Foundation of ChinaProject(51105384)supported by the National Natural Science Foundation of China
文摘Research on the distribution of smoke in tunnels is significant for the fire emergency rescue after an operating metro train catches fire. A dynamic grid technique was adopted to research the law of smoke flow diffusion inside the tunnel when the bottom of a metro train was on fire and to compare the effect of longitudinal ventilation modes on the smoke motion when the burning train stopped. Research results show that the slipstream curves around the train obtained by numerical simulation are consistent with experimental data. When the train decelerates, the smoke flow first extends to the tail of the train. With the decrease of the train's speed, the smoke flow diffuses to the head of the train. After the train stops, the slipstream around the train formed in the process of train operation plays a leading role in the smoke diffusion in the tunnel. The smoke flow quickly diffuses to the domain in front of the train. After forward mechanical ventilation is provided, the smoke flow inside the tunnel continues to diffuse downstream. When reverse mechanical ventilation operates, the smoke in front of the train flows back rapidly and diffuses to the rear of the train.
基金National Natural Science Foundation of China （51274205）, the Doctoral Program Foundation of Ministry of Education the New Teacher Project （20070290022） and the Open Project of China University of Mining and Technology Resources and Mine Safety State Key Laboratory （S KLCRSM 10KFB 13）.
文摘The objective of this work is to investigate the influence of smoke movement during mine fires on miner evacuation behaviors. A three-dimensional computational fluid dynamics method was conducted to reconstruct the lane- way conveyor belt fire scenes under two ventilating conditions. The parameters, including temperature-time histories, soot density, carbon monoxide and heat release rate, were simulated to characterize the mine fires at various ventilating speeds. A miner evacuation model affected by fire smoke movement was advanced to describe the miner evacuation behaviors, which can be divided into three stages. Based on the evacuation model coupled with the mine fire smoke movement, the available safety evacuation time for miners involved in coal mine fire located in different sites was estimated. Two evacuation patterns were advanced according to the ventilating speeds combined with the model of miner evacuation behaviors. The results show that the miners located between the inlet-air end and the air door in lane 1 should be evacuated to the inlet-air end and other miners involved in coal mine fire could choose the air door as the escaping destination, when the ventilation speed is greater than 3 m/s. Accordingly, the research can be used as references for the mine safety administration authorities to design the safety evacuation.
文摘In this study,experimental and numerical simulation methods were combined to simulate the changing course of the temperature and velocity fields in nine different fire scenes. The characteristics of smoke movement in shafts with different fire source position factors(h/H) were quantitatively investigated,and the non-dimensional fitting function between the fire source position factors and the maximum temperature was deduced. The results showed that the location of the neutral plane moved upward as the fire source rose,and all the generated smoke spread to the upper areas;however,there was barely any smoke in the lower areas. The maximum temperature was inversely proportional to the fire source position factor;the higher the source position is,i.e. the higher the ratio factor is,the lower the maximum temperature is in the shaft. The experimental verification of the fire dynamics simulator(FDS) showed good results.
文摘Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal of the tunnel follows aW-shaped distribution.The congestion situation does not allowfor immediate longitudinal smoke exhaust at the early stage of the fire,and the natural spread of smoke is complicated.An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident,employing the fire dynamics software FDS,considering five slopes and four fire locations.The simulation results reveal that the layer of high-temperature smoke becomes thicker as one gets closer to the fire source.The thermal pressure difference significantly impacts the temperature distribution within the tunnel and the distance of smoke spread.The value of the thermal pressure difference is significantly affected by changes in slope.It reaches a maximum of 157 Pa at a 5%slope,while it is only 41 Pa at a 1%slope when the fire occurs at the V-point.Fire hazards vary across locations within the W-shaped tunnel,necessitating separate consideration of the V-point and inverted V-point fire characteristics.The mass flow rate in small and large slope tunnels shows different decay rates due to variations in the main forces acting on the movement.Hence,two equations have been developed to predict the smoke mass flow rate,indicating a nonlinear relationship with the tunnel slope and the distance fromthe fire source.The tunnel slope inversely affects the smoke mass flowrate at the same location.The results can be utilized as a reference for conducting evacuation operations and aiding rescues during aW-shaped tunnel fire.
文摘Wave motion in subway or tunnel fire is an intrinsic property of smoke.As the pressure of smoke changes with mass of certain power,a kind of linear wave equation for smoke can be derived from the conservation equations of its mass and momentum,under nearly homogeneous zone assumption.The smoke movement of 4 subway fires was simulated with Airpak.By fitting the pressure-mass functions to the simulated data,wave equations of the smoke were derived,and wave motions of smoke were thus validated.It can be seen that smoke wave is a kind of mass wave,whose velocity is inversely proportional to smoke mass,and wave of a bigger fire propagates slower.
基金supported by the grant from Post Doctor Program, Chonbuk National University (2008)
文摘Objective Embryonic movements （EM） and angiogenesis pathways are evolutionarily conserved mechanisms which are essential for proper embryonic development. Deviations in these processes by exposure to cigarette smoke condensate （CSC） may cause vascular and morphogenetic disorders. Methods Using chicken and mouse embryos, we have demonstrated the in vivo effects of CSC on EM, vascular development, and organogenesis. Results Examination of the CSC exposed chicken embryos revealed a significant reduction in EM, stunted growth, deviated pattern of blood vessels, hemorrhages, and localized necrosis. Likewise, mouse embryos that were exposed to CSC at E8.5 and E9.5 died between E11.5 and E12.5, respectively. These mouse embryos showed defects in morphogenesis and remodeling of the embryonic vasculature, while littermate controls showed normal development. Conclusion Cigarette smoking during pregnancy is fatal for growing embryos. CSC may induce the remodeling of embryonic vasculature, leading to various pathologies.
