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Recent studies prove that the main cause of death during urban fires is poisoning by smoke
... However, these reported works only considered a very weak natural buoyancy condition induced by solar heating. More recently, a more catastrophic scenario (Besserre, Delort 1997; Alarie 2002 ) has been investigated under which the hazardous pollutant is produced by a catastrophic fire at the base of a street canyon (Hu et al. 2009) or in an adjacent building (Hu et al. Downloaded by [2010) along a street canyon. ...
... These will pose serious harm to human health. Recent studies (Besserre, Delort 1997) have proved that the main cause of death during urban fires is poisoning by smoke. Complex interaction of the external wind flow with fire-induced buoyant flow should be accounted for, which is much more complex than that produced naturally by solar effect, in characterizing the dispersion of fire smoke in urban atmosphere. ...
... Turbulence methods used in CFD generally include Reynolds Averaging Navier-Stokes equation (RANS) method, Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) (Besserre, Delort 1997; Alarie 2002; Hu et al. 2009). Large Eddy Simulation (LES) is able to predict the unsteadiness and intermittency which is the most important feature of a strong turbulent buoyancydriven flow. ...
Street canyon, formed by buildings along two sides of a road, is an important and ubiquitous architectural element in the metropolises. When a fire occurs in an urban street canyon, a critical serious phenomenon is found to happen where the uprising fire smoke is re-circulated back into the base of the street canyon by the wind flow beyond a critical velocity. Theoretical analysis is derived based on Froude number (Fr), by balancing the inertial force of the wind flow to the buoyancy strength of the fire smoke. It is found that the critical re-circulation wind velocity is proportional to an integrated global parameter . Large Eddy Simulations (LES) are carried out by Fire Dynamics Simulator (FDS). The critical Froude number (Fr) is found to be about 0.7∼0.8. The simulation results are well collapsed by the generalized theoretical relation. It is further revealed that the non-dimensional critical re-circulation wind velocity against aspect ratio of street canyons in the skimming flow pattern (W/H < 1.43) falls into two behavioural regimes, where it firstly increases then remains constant with the increase in street canyon aspect ratio (W/H) with a turning point at W/H = 1. A global non-dimensional relation is finally achieved for the critical re-circulation wind velocity (u), fire heat release rate and its height (H) to the top of the street canyon as well as the street canyon aspect ratio (W/H).
... As a potential annihilator it never steps back to prove itself as a powerful destroyer of everything whatever it faces. Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires[1,2]. During a fire accident, most of the people are found to be victimized not due to fire burning rather due to the toxic potency of emerging CO and CO2 gases. ...
... As a potential annihilator it never steps back to prove itself as a powerful destroyer of everything whatever it faces. Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires [1,2]. During a fire accident, most of the people are found to be victimized not due to fire burning rather due to the toxic potency of emerging CO and CO2 gases. ...
Casualty of garment factory workers from factory fire in Bangladesh is a recurring tragedy. Smoke, which is more fatal than fire itself, often propagates through different pathways from lower to upper floors during building fire. Among the toxic gases produced from a building fire, carbon monoxide (CO) can be deadly, even in small amounts. This paper models the propagation and transportation of fire induced smoke (CO) that resulted from the burning of synthetic polyester fibers using two open source platforms, CONTAM and Fire Dynamics Simulator (FDS). Smoke migration in a generic multistoried garment factory building in Bangladesh is modeled using CONTAM where each floor is compartmentalized by different zones. The elevator and stairway shafts are modeled by phantom zones to simulate contaminant (CO) transport from one floor to upper floors. FDS analysis involves burning of two different stacks of polyester jacket of six feet height and with a maximum heat release rate per unit area of 1500kw/m² over a storage area 50m² and 150m², respectively. The resulting CO generation and removal rates from FDS are used in CONTAM to predict fire-borne CO propagation in different zones of the garment building. Findings of the study exhibit that the contaminant flow rate is a strong function of the position of building geometry, location of initiation of fire, amount of burnt material, presence of AHU and contaminantgeneration and removal rate of CO from the source location etc. The transport of fire-smoke in the building Hallways, stairways and lifts are also investigated in detail to examine the safe egress of the occupants in case of fire.
... [8][9][10] Previous studies have shown that toxic and harmful smoke from combustion poses a major threat to trapped and rescue workers. [11][12][13][14][15] Therefore, the characteristics of smoke spread during tunnel fires would be an important topic to research. 16 A detailed understanding of the smoke layer profile would be beneficial to the design of the smoke exhaust system and the evacuation and firefighting rescue in tunnel fire. ...
With the massive construction of road shield tunnels, vertical evacuation using slides is increasingly used, for it can save construction cost, improve evacuation efficiency and enhance space utilization. An evacuation experiment in an underwater shield tunnel with 101 participants has been carried out in order to obtain the alighting time of bus passengers, the movement speed, the opening time of the slide cover plate, the evacuation capacity of the slide, the total evacuation time and the behavior characteristics of the participants in the whole evacuation process by using fixed cameras, DSLR cameras and drones. The experiment results showed that the average alighting time for a 46-seat bus full of passengers was 62.3 ± 5.1 s (standard deviation), ranging from 55 s to 72 s. The average evacuation capacity of the evacuation slide was 27 person/min, and the evacuation capacity for males was slightly better than females. The opening time of slide cover plate was greatly affected by slide type and participants. The average movement speed of participants exceeded 4.0 m/s on the driveway with the good lighting conditions, smooth ground and clear evacuation instructions. And the movement speed declined in secure channel. This paper also describes the bottleneck phenomenon in the whole process of evacuation.
... Smoke is generated from the smoldering fire and depending on the burning rate of the fuel, smoke generation increases. Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires [1,2]. During a fire accident, most of the people are found to be victimized not due to fire burning rather due to the toxic potency of emerging CO and CO2 gases. ...
Casualty of garment factory workers from factory fire in Bangladesh is a recurring tragedy. Smoke, which is more fatal than fire itself, often propagates through different pathways from lower to upper floors during building fire. Among the toxic gases produced from a building fire, carbon monoxide (CO) can be deadly, even in small amounts. This paper models the propagation and transportation of fire induced smoke (CO) that resulted from the burning of synthetic polyester fibers using two open source platforms, CONTAM and Fire Dynamics Simulator (FDS). Smoke migration in a generic multistoried garment factory building in Bangladeshis has been modeled using CONTAM where each floor is compartmentalized by different zones. The elevator and stairway shafts are modeled by phantom zones to simulate contaminant (CO) transport from one floor to upper floors. In this study, constant coefficient model of source and sink is used to find the extreme condition of fire and smoke propagation. It is kind of impossible to check the simulation project practically as it would involve testing full-scale fire in a garment facility. For this reason, two generic building structure resulting outputs are considered and comparative analysis and study is performed. Simulation method is operated based on “transient” contaminant flow, air flow. Transient integration method is performed based on Implicit Euler. FDS analysis involves burning of two different stacks of polyester jacket of six feet height and with a maximum heat release rate per unit area of 1500kw/m2 over a storage area 50m2and 150m2, respectively. The resulting CO generation and removal rates from FDS are used in CONTAM to predict fire-borne CO propagation in different zones of the garment building. “SFPE Handbook” is used as reference for the input values of fuel. Smokeview (SMV) is a support program used with Fire Dynamics Simulator to visually illustrate the code written in FDS. Real-time smoke propagation with time and space is displayed using SMV. In our study, two different types of fuel is used – Polyester and Cotton. For these fuels peak heat removal rate per unit area (HRRPUA), time of peak, smoke generation and removal rate are studied over a defined time period. For measuring smoke generation and removal rate, temperature of the room two separate devices is set within the smoke pathway. Findings of the study exhibit that the contaminant flow rate is a strong function of the position of building geometry, location of initiation of fire, amount of burnt material, presence of AHU and contaminant generation and removal rate of CO from the source location etc. In this study, source’s generation rate, removal rate, storage area of cloths, AHU supply and return rate, floor position are taken as variables. Varying these parameters smoke propagation in a multistory building is analyzed. The transport of fire-smoke in the building Hallways, stairways and lifts are also investigated in detail to examine the safe operation of the occupants in case of fire. Because using hallways smoke propagates from source room to other rooms of the floor and using phantom zone (stairways, lifts) smoke propagates to other floor of the building. That is why analysis of smoke propagation in hallways and phantom zone is given utmost importance in this study.
... Confining fire generated smoke and toxic gases at the source of fire can play a lifesaving role on the evacuees. Primary cause of death in building fires is inhalation of toxic smoke and subsequent asphyxiation [1,2]. Fire resistant doors, fire resistant walls and smoke control systems are traditionally used to confine the heat and smoke propagation in case of a fire incident. ...
This study aims to investigate air curtains as an effective thermal and aerosol barrier against high gradient of flow parameters generated by a typical fire incident. The numerical investigations are conducted by solving Navier-Stokes equations in Fire Dynamics Simulator (FDS). A clothing store of 12 m2 floor area with a fire of 1528 kW/m2 heat release rate per unit area (HRRPUA), at the furthest corner from the door, is considered as the source of high thermal and pressure gradients inside the store. The only means of ventilation for the current study, is an air curtain of 0.91 m length placed at the door at 2.13 m height from the floor. The air curtain’s injection velocity, injection angle, flow rate and cross-sectional area of the flow channel are systematically varied for optimum sealing performance. The change in temperature profile and aerosol particle concentration with and without air curtain, and air curtain effectiveness E, are measured. Result suggests, the injection velocity and injection angle are the key parameters in preventing the heat and mass transfer across air curtains. The twin jet design, a commercially available feature for air curtains, is found to be less effective up to pitch ratio of 4 compared to that of a single jet design for restraining heat and mass transfer.
... [8][9][10] Previous studies have shown that toxic and harmful smoke from combustion poses a major threat to trapped and rescue workers. [11][12][13][14][15] Therefore, the characteristics of smoke spread during tunnel fires would be an important topic to research. 16 A detailed understanding of the smoke layer profile would be beneficial to the design of the smoke exhaust system and the evacuation and firefighting rescue in tunnel fire. ...
A series of experiments were carried out in a model‐scale tunnel with dimension of 6.0 m × 1.0 m × 0.7 m to investigate the smoke spread behaviors and the typical smoke layer height. Alcohol was employed as fuel, and the heat release rate was set to be 9.5, 18.4, 30.1, and 63.5 kW, respectively. The temperature profile in the tunnel was measured, and the buoyant flow stratification conditions were visualized by a laser sheet. The experiment results show that the N percentage rule would greatly influence by subjective factors. As the N (10, 20, 30) value increases, the smoke layer height also increases. The results calculated by the buoyancy frequency method were more accurate. Fan's prediction method (Fan WC, Wang QG, Jiang FH. Concise Guide of Fire Science. He Fei: University of Science and Technology of China Press; 1995.161 p.) does not accurately evaluate the smoke layer thickness in tunnel fire. An enhanced empirical formula for predicting the smoke layer thickness in the one‐dimensional horizontal spread stage was proposed. It is shown that the empirical formula could well predict the smoke layer thickness by comparing with the experimental data of previous studies.
... The development of efficient smoke exhaust methods has received much attention in tunnel fire research because smoke is the most deadly factor in the event of a fire (Besserre and Delort, 1997). Natural ventilation using vertical shafts or roof openings has been studied extensively by researchers over the years (Vauquelin and Megret, 2002;Wang et al., 2009;Ji et al., 2012bJi et al., , 2014Kashef et al., 2013;Ura et al., 2014) in order to effectively suppress the descent of smoke layer, which will facilitate safe evacuation of occupants. ...
... Smoke and other poisonous and harmful gases generated by fires accumulate easily inside tunnels owing to the enclosed structure, which can pose a great threat to the safety of trapped staff and firefighters (Alarie, 2002;Babrauskas et al., 1998;Besserre and Delort, 1997;Hietaniemi et al., 1999). Therefore, the design of ventilation and smoke extraction systems is an important part of tunnel fire protection (Du et al., 2015;Liang et al., 2017). ...
To investigate the entrainment phenomenon near a mechanical exhaust vent in the tunnel fire, the computational fluid dynamics method employing the software Fire Dynamics Simulator (FDS) is utilized to analyse the effects of heat release rate (HRR) and exhaust velocity on the entrainment near the vent. The simulation results indicate that the total amount of fresh air entrained in the tunnel increases continuously with increasing HRR and exhaust velocity. However, when the smoke temperature is low, the mass flow rate of fresh air exhausted through the shaft is insensitive to the HRR, while is affected more by the exhaust rate. In addition, a simplified prediction model for downstream smoke temperature is developed to account for the entrainment effect on smoke temperature variation. The predicted values accord well with the simulated ones. Results in this work can provide a reference to the optimization design and management of smoke control system in tunnels.
... Toxic gas from fire smoke, known as carbon monoxide (CO), is the most fatal factor in fire safety [1,2]. Although lower visibility due to smoke particles makes it more difficult for people to find a way out, toxic gases may directly harm or kill the evacuee [3]. ...
The hazards of the spread of fire smoke in a channel have been recognized. This paper relates to the potential use of a water mist curtain (WMC) for preventing the spread of fire smoke, focusing particularly on smoke control at the early stage of a fire, with the aim of reducing the harm of fire smoke and allowing time for people to escape. Fatal factors for occupant evacuation in a fire, such as carbon monoxide concentration, smoke temperature, and visibility, were measured in the section controlled by the WMC. The results indicate that the WMC can be effective in preventing fire smoke from spreading at the early stage, and may provide a useful reference for developing a novel method of smoke control. Furthermore, the effects of nozzles with different spray characteristics were investigated and an optimal working pressure was suggested. In addition, a mathematical model was simplified and used to analyze the interaction between the fire-induced smoke layer and WMC spray.
... The magnitude of tunnel fires has been highlighted by major accidents, including the Tauern Tunnel of Austria (Carvel et al., 2001), the Mont Blanc tunnel joining France to Italy (39 victims) (Barbato et al., 2014), and a subway tunnel in Daegu,Korea (198 victims) (Hu et al., 2007). Smoke is the most deadly factor during fires (Besserre and Delort, 1997). Thus, the development of an effective smoke exhaust method has receive a large amount of attention because it is one of the most important protection measures for personnel safety during evacuation in tunnel fires. ...
... In the integrative building, the pedestrian is normally crowed and fire-induced smoke will cause huge casualties and property loss once fire happens. In the fire, studies proved that smoke is the main cause of death [1]. In the past two decades, many researchers used the Computational Fluid Dynamics (CFD) technology to investigate the smoke control strategies during the atrium fire. ...
... 主要是由火灾产生的烟气造成的 [1][2] ，故研究长通 道内机械排烟效果具有重要意义。 根据卷吸机理不同，可将长通道型结构内的火 灾烟气运动过程分为 4 个阶段 [3][4][5] [6] ；胡隆华等对地下走廊补气口位置对 排烟效果的影响进行了研究， 提出了定性的原则 [7] ； Rie Dong-Ho [8] ，Yuan Feng-Dong [9] 等利用数值模拟 方法对不同通风模式下地铁站的机械排烟效果进 行了分析和优化，但这些研究均未结合排烟口处于 不同阶段进行量化分析。本文采用小尺寸长通道模 拟实验，对两种开敞条件下，排烟口位置处于烟气 水平蔓延不同阶段时对排烟效果的影响进行了细 致定量研究。 1 长通道内烟气和空气流动状况 ...
A series of mechanical smoke exhaust experiments were conducted in a bench-scale long channel. Two opening conditions were simulated, two ends being opened and a single end being opened respectively. The influence of the turbulent entrainment intensity at the smoke layer interface, due to different relative locations of exhaust openings to fire source, on the mechanical smoke exhaust efficiency is studied. The results show that when the exhaust openings are operated in the stage of one-dimensional horizontal spread, the turbulent entrainment effect at the smoke layer interface would be evidently intensive, leading to a poor smoke control effect. It is recommended to operate the exhaust openings in the range of the longitudinal distance to fire source less than 1.33 times of the channel width. And for the channel with one end closed, additionally exhaust openings should be opened near the closed end.
... Toxic gas from fire smoke, known as carbon monoxide (CO), is the most fatal factor in fire safety [1,2]. Although lower visibility due to smoke particles makes it more difficult for people to find a way out, toxic gases may directly harm or kill the evacuee [3]. ...
Aiming at fire smoke control and fire compartmentation inside complex buildings, such as the evacuation passageway, fire smoke controlled by water mist was studied through setting up an experimental platform containing the water mist curtain system. The results indicate that under the effect of 2.0 MPa, water mist curtain can bring about 80% reduction of smoke density optical and 62% reduction of smoke temperature. It can promote visibility of the protected area from 1.8 m to 9.5 m. Smoke passing through the curtain experimences a 40 s delay. The water mist curtain proves to effectively control fire smoke and leave enough time for evacuation.
... For example, tunnel fires in Baku in October 1995 killing 289 people and the Alpine train fire in Kaprun Austria in November 2001, killing 155 people [1], the arson fire in a long tunnel in Daegu Korea in February, 2003, killing 198 people [2]. Statistics showed that smoke was the most fatal factor in fires, most victims were killed by the smoke and toxic gases, such as carbon monoxide [3][4][5]. Therefore, smoke control is very important for saving lives in case of tunnel fires. ...
When a fire occurs in a tunnel, smoke control is very important for people's safety. Extraction systems were designed in order to extract smoke in tunnel. In this study, Fire Dynamics Simulator (FDS) was used to research the plug-holing on tunnel fire for it will significantly reduce the efficiency when it occurs. A series of mechanical exhaust velocity with different heat release rate were simulated, the plug- holing issue on a heat release rate was determined by N-percentage rule. N = 20 in our study is based on previous studies and our experimental research. We analysis the critical exhaust rate determined by N-percentage rule on different heat release rate, and find that the critical Froude number 1.5 used to determine the onset of plug-holing in enclosed buildings can’t be used in tunnel fire. However, a critical Froude number 2.1 could be used in determining the onset of plug-holing in tunnel fire.
... The current research of such buoyancy effect on the transportation of these hazardous combustion products in urban elements is still very few. Since the main cause of the death during urban fires is the toxicity and asphyxiating action of the harmful smoke [15,16], the street canyon's smoke dispersion characteristic with such strong buoyancy effect should be given considerable attention. ...
Critical re-circulation phenomenon happens when a fire occurs in an urban street canyon, in which the uprising smoke plume is re- circulated back into the base of the street canyon by the wind-induced flow. This happens when the inertia of the wind flow with a certain so-called critical re-circulation velocity balances the buoyancy force of the fire smoke. The fire smoke dispersion and critical re- circulation wind velocity have been revealed in previous works for urban street canyons with aspect ratio (W/H) of unity. This paper presents an investigation of the effect of street canyon aspect ratio on the above behaviour. Large Eddy Simulation (LES) was performed by Fire Dynamics Simulation (FDS) for a 5 MW fire corresponding to the Heat Release Rate of a burning car. The simulated street canyon has height of 18 m and different width of 9 m, 12 m, 15 m, 18 m, 21 m, 24 m, 27 m, 30 m and 36 m respectively, with aspect ratios varied from 0.5 to 2.0. The smoke soot and CO concentration distribution were presented for different street canyon aspect ratios. It was found that the variation of critical re-circulation wind velocity with street canyon aspect ratio can be divided into three zones. The critical re-circulation wind velocity firstly increases at the first zone, then remains constant at the second zone, and finally increases again at the third zone with the increasing of the street canyon aspect ratio. This special behaviour was explained based on the flow characteristics in the street canyon.
... With the increasing of high-rise buildings, the number of high-rise building fires increased and caused many disasters, such as the fire in a residential building on Jiaozhou road in Shanghai in 2010, killing 58 people [1]. Statistics showed that more than 80 percent deaths in fire were caused by toxic gases, such as carbon monoxide [2][3][4][5]. Therefore, in case of fire, it is very important to control the spreading of smoke. ...
... More and more attention is being paid to the fire protection of long underground tunnels. Investigations showed that smoke was the major fatal factor in such fires, especially in tunnel fires where much toxic gases were released due to incomplete combustion [3,4]. So, smoke control is very important for saving lives in case of underground tunnel fires [5]. ...
Three full scale tests were conducted in a road tunnel to study the smoke spread with different fire sizes and wind speed conditions. The smoke temperature under the ceiling, the smoke layer height distribution and the travel of the smoke front in a 1000 m long domain along the road tunnel were measured. Results showed that wind speed had much influence on the spread of smoke in the tunnel. When wind speed was such low as less than 1 m/s, a smoke layer could form and stabilize all along the tunnel. But when the wind speed was such high as more than 2 m/s, smoke layer could only be maintained in a distance of about 400 m in the downstream. The slowdown of the traveling of the smoke front in the downstream along the tunnel was more obvious when the wind speed was smaller. All these full scale data presented here can be used for further study on the verification or improvement of existing fire models for enhancing their applicability to such long tunnels.
... Consequent to the arson fire in a long tunnel in Daegu Korea on February 18, 2003, killing 198 people, and two more arson fires in Hong Kong and Russia, there are concerns on tunnel or long corridor fires. Statistics have shown that smoke was the most fatal factor in fires (Babrauskas et al., 1998;Besserre and Delort, 1997), especially in tunnel fires where large amount of toxic gases were released due to incomplete combustion. In order to provide appropriate fire safety, the physics of smoke spreading should be well understood first (Buchanan, 1994(Buchanan, , 1999. ...
Full-scale burning tests were conducted in a long corridor to study the variations in smoke temperature and velocity. The results were compared with the expressions proposed in the literature. It appeared that the reduction in temperature down the corridor can be fitted by an exponential function on the distance. The power law equation by Bailey et al. [Bailey, J.L., Forney, G.P., Tatem, P.A., Jones, W.W., 2002. Development and validation of corridor flow submodel for CFAST. J. Fire Prot. Engg. 22, 139–161] also agreed fairly well with the measured data for dimensionless distance away from the fire source less than 0.4 or when the distance from the fire source is less than 35 m. The distribution of velocity along the corridor can also be fairly well fitted by exponential equations.
... The latest large tunnel fire, which occurred in Daegu Korea on February 18, 2003, even caused 198 deaths [1]. Statistics showed that smoke was the most deadly factor in fires [2,3], especially in a tunnel fire where incomplete combustion released much toxic gases. In order to give fire safety design to prevent fire disasters, the physics of smoke spread should first be quantitatively understood and thus predicted [4,5]. ...
A simple model was reported to predict the longitudinal distribution of temperature rise for the smoke layer along a tunnel. The longitudinal decay of excess smoke layer temperature in dimensionless form was studied by including convective and radiative heat transfer to the boundary. An expression was derived to relate to the dimensions of the cross-section of the tunnel, the depth and the velocity of the smoke layer to the temperature. A series of full-scale tests was conducted in three vehicular tunnels to verify the model. There, temperature field and smoke layer traveling velocity were measured downstream the fire source. The decay factors for longitudinal smoke layer excess temperature distributions were predicted from the model based on the smoke layer velocities and the dimensions of the vehicular tunnel. Results are then compared with those deduced directly from the measured temperature data. Good agreement was achieved.
... Statistical results show that smoke is the most deadly factor in building fires [3,4]. So assessing the characteristics of the smoke filling process in a building is an important work for designing a fire protection system in the performance-based fire protection method, especially in a big and complex construction, where the smoke development shows more unforeseeable quality. ...
A multicell concept, which first divides the total space into subspaces and then uses the traditional two-layer zone model in each subspace, is performed in this paper to simulate the smoke filling process in a domestic boarding–arrival passage, with an aspect ratio of about 52.3, of an international airport terminal by using CFAST version 4.0.2. Results show that the impingement of ceiling jet upon the passage ends is a critical time for the evacuation of people near these ends. Some comparisons are also presented to show that more reasonable results about the smoke temperature field and the smoke layer interface height are achieved using this method than using the traditional two-layer zone model. Further, results through different subspace dividing technology and using FDS version 3.0, a CFD model, are also achieved and compared on simulating the smoke filling process in a simplified passage, for the purpose of studying the prediction of impingement time, the smoke temperature distribution, and the smoke layer interface height development pattern before and after the impingement. The limitations of this modeling technology and future research topics are also discussed.
... In the case of the flame not impinging on the tunnel ceiling, the formula for flame inclination can be obtained by modifying the equations in unconfined spaces. However, H. Kurioka attempts to develop an alternative model based on the following assumptions [8][9][10][11][12]. ffiffiffiffiffi A f p , for that carried by the inclined fire plume are, respectively, adopted as a reference length. ...
In order to assess the possibility of exhausting smoke through passive roof openings and the influence of smoke on personnel in the tunnels, full-scale fire experiments in tunnels with roof openings are carried out, which were rarely reported in the previous references. The data of smoke propagation, smoke sedimentation, velocity field and temperature field are measured. On the basis of the smoke longitudinal propagation laws, the prediction model of calculating backlayering distance is built. The Kurioka model and the built mathematical models are validated by those experiments. All the experimental data presented in this paper can be further applied for verification of numerical models, and bench-scale experimental results. Those full-scale experimental results and theoretical analysis can also be used for directing tunnel fire research, which afforded scientific gist for fire protection and construction of road tunnel with roof openings.
... Statistics showed that smoke and toxic gases, such as carbon monoxide, are the most fatal hazard to the people in fires [1][2][3]. Therefore, when a fire occurs, it is very important to stop the smoke and toxic gases from spreading by natural or mechanical exhaust systems. As a result, the current building codes in China as well as lots of former studies on smoke management have mainly focused on the smoke exhausting rate and the proportion of fresh air within the smoke exhaust rate. ...
A set of burning experiments were conducted to investigate the influence of smoke vent height and exhausting velocity on mechanical smoke exhausting efficiency. Results have shown that the smoke exhausting process becomes more efficient due to the increased smoke vent height and the decreased exhausting velocity, which eliminate the plug-holing issue with fewer disturbances on the smoke layer interface. For each certain exhausting velocity, there is a critical value of distance between the vent and the bottom of the smoke layer. When the distance is less than the critical value, the smoke exhausting is inefficient, and the efficiency decreases sharply as the distance decreases. Contrarily, when the distance is greater than the critical value, a good efficiency can be acquired and the exhausted smoke increased relatively slowly as the distance increases. A critical Froude number, proposed by Hinkley to predict the onset of plug-holing effect in gravity venting systems, was validated in the experiments. However, the experimental results indicate that in the tests without the plug-holing, the fresh air entrained due to smoke exhausting is up to 48% of the mechanical exhausting rate.
... Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires [1,2]. The smoke particles decrease the visibility range in the space resulting in that the people cannot find the way out. ...
Smoke and toxic gases, such as carbon monoxide, are the most fatal factors in fires. This paper models fire-induced smoke spread and carbon monoxide transportation in an 88m long channel by Fire Dynamics Simulator (FDS) with large eddy simulation (LES). FDS is now a well-founded fire dynamics computational fluid dynamic (CFD) program, which was developed by National Institute of Standards and Technology (NIST). Two full scale experiments with fire sizes of 0.75 and 1.6MW were conducted in this channel to validate the program. The spread of the fire-induced smoke flow together with the smoke temperature distribution along the channel, and the carbon monoxide concentration at an assigned position were measured. The FDS simulation results were compared with experimental data with fairly good agreement demonstrated. The validation work is then extended to numerically study the carbon monoxide concentration distribution, both vertically and longitudinally, in this long channel. Results showed that carbon monoxide concentration increase linearly with the height above the floor and decreases exponentially with the distance away from the fire source.
Fire scenario of street canyon, in which buildings had different heights, was investigated by Large Eddy Simulation (LES). To figure out the impact of street canyon layout on the smoke transportation behavior, side buildings in street canyon with different heights were built in this study. Simulation results showed that two regimes existed in the flow pattern of buoyancy plume. The critical re-entrainment phenomenon was defined as a critical criterion between the regimes. When the horizontal wind velocity exceeded the critical value, fire smoke would re-flow into the street canyon. An improved Froude number (Fr) considering the height difference of street canyon side buildings was proposed to quantify the dispersion pattern of fire smoke plume in street canyon. The investigation showed that the Froude number was consistent when the critical re-entrainment wind velocities reached in different street canyons.
The topic of tunnel fire attracted considerable attention in past two decades. The popularity of this topic is mainly attributed to the widespread construction of long-span tunnels and their incident fire safety issues, as well as the frequent occurrence of catastrophic tunnel fires. To date, a number of research papers have been published focusing on specific aspects of tunnel fires such as fire dynamics, smoke extraction, fire suppression system, personnel evacuation, fire risk evaluation, and some others with broader areas of focus. In this work, a thorough bibliometric and network analysis is conducted on the basis of peer-reviewed publications on tunnel fires, seeking to provide insights in this topic. A total of 519 research articles are obtained from the Web of Science Core Collection database. It is identified that the most prolific journal is Tunnelling and Underground Space Technology, with 121 papers, accounting for 23.3% of the total. England is the most influential region with the highest citations per document, while China is the most prolific country with nearly a half of the total, where the University of Science and Technology of China is the primary contributor. The visualization and cluster analysis of research topics indicate that the currently bursting topics mainly concentrate on the smoke thermodynamics and smoke extraction based on model-scale tests. The reference analysis and co-citation network also confirm the findings.
Fires in high-rise buildings often result in tremendous property losses and heavy casualties. Smoke has been reported to be the main cause of these casualties. A modified Opposite Double-jet Air Curtain (ODAC) is introduced in order to confine smoke movement and to exhaust smoke during a high-rise building fire. Here, a study including an experiment and a numerical simulation, was performed to determine the efficacy of a modified ODAC. The experiment was conducted on a 1:12 scale model of a high-rise building. A complementary Fire Dynamics Simulator (FDS) simulation was conducted on a full scale building. The influences of the air curtain discharge velocity and heat release rates (HRRs) were examined. The results of this study show that given the same supply air volume and HRR, the carbon monoxide (CO) concentration with the ODAC is clearly lower than the levels found with a traditional air curtain in a high rise building fire. The gas temperatures in the hallway increased significantly with the increase of HRR, and when the HRR reached 1.5 MW or more, a significant increase in the temperature of the smoke in the stairwell entrance was observed. When HRR reaches 2 MW, and the velocity has increased to 9 m/s, the CO concentration in the entrance of stairwell just meets the minimum Safety and Health standards.
To understand the characteristics of smoke spreading of fires in a flat underground, experimental and numerical researches were conducted. By comparing the results of the experiment and simulations, the conclusions were drawn that when the maximum heat release rate (HRR) is higher than 480 kW in the flat-space building, it only took 10 s to reach a distance 15 m from the fire source, and 100 s to fill up the 964 m3 volume of the upper part above 2.0 m height of the flat space, which was mainly due to the heat release rate (HRR). However, the HRR did not have obvious effect on the speed of the smoke propagation along the ceiling. Moreover, the temperature stratified vertically in the distance far from the fire source.
Three full-scale burning tests were conducted in a natural ventilation city road tunnel with shafts. Fire sources were placed to be at different locations but its peak release heats were all around 5MW. Results showed that large amounts of smoke and heat were released through shafts. The maximum smoke temperatures under the ceiling were below than 100°C, and being lower than 110°C at the safe height farther 3m away from fires. The maximum smoke spreading horizontal lengths were less than 240m both in the upwind and downwind. During the late stages, many smoke particles descended from the ceiling and downdraught occurred at shafts due to low smoke temperatures, but the visibility was not very bad and people needn’t evacuate. All These results are valuable for fire protection and construction of natural ventilation road tunnel with shafts.
Full-scale burning tests were conducted in a full-scale underground long corridor with beamed ceiling and smooth ceiling. The influence of air-supply opening position on the smoke exhaust efficiency was studied. The operation time of the smoke exhaust fan was also discussed to obtain a better smoke exhaust. Results showed that the smoke exhaust would be more efficient when air-supply openings were some distance away from the smoke exhaust openings. When the air-supply opening was near the smoke exhaust opening, even with larger smoke exhaust rate, it still gave poor smoke control results. Two comparing tests on the effects of operation time indicated that it would give poor smoke control ability when the smoke exhaust system operated too early. Finally, some future research topics were also discussed in this paper.
The quantitative risk assessment (QRA) is one of the explicit requirements under the European Union (EU) Directive (2004/54/EC). As part of this, it is essential to be able to estimate the number of fatalities in different accident scenarios. In this paper, a tangible methodology is developed to estimate the number of fatalities caused by toxic gases due to fire in road tunnels by incorporating traffic flow and the spread of fire in tunnels. First, a deterministic queuing model is proposed to calculate the number of people at risk, by taking into account tunnel geometry, traffic flow patterns, and incident response plans for road tunnels. Second, the Fire Dynamics Simulator (FDS) is used to obtain the temperature and concentrations of CO, CO(2), and O(2). By taking advantage of the additivity of the fractional effective dose (FED) method, fatality rates for different locations in given time periods can be estimated. An illustrative case study is carried out to demonstrate the applicability of the proposed methodology.
The dispersion of buoyancy driven smoke soot and carbon monoxide (CO) gas, which was ejected out from side building into an urban street canyon with aspect ratio of 1 was investigated by large eddy simulation (LES) under a perpendicular wind flow. Strong buoyancy effect, which has not been revealed before, on such pollution dispersion in the street canyon was studied. The buoyancy release rate was 5 MW. The wind speed concerned ranged from 1 to 7.5m/s. The characteristics of flow pattern, distribution of smoke soot and temperature, CO concentration were revealed by the LES simulation. Dimensionless Froude number (Fr) was firstly introduced here to characterize the pollutant dispersion with buoyancy effect counteracting the wind. It was found that the flow pattern can be well categorized into three regimes. A regular characteristic large vortex was shown for the CO concentration contour when the wind velocity was higher than the critical re-entrainment value. A new formula was theoretically developed to show quantitatively that the critical re-entrainment wind velocities, u(c), for buoyancy source at different floors, were proportional to -1/3 power of the characteristic height. LES simulation results agreed well with theoretical analysis. The critical Froude number was found to be constant of 0.7.
The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.
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