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  • 1.
    He, Kun
    et al.
    University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Shi, Long
    University of Science and Technology of China, China.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Experimental study on the maximum ceiling gas temperature driven by double fires in a tunnel with natural ventilation2024In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 144, article id 105550Article in journal (Refereed)
    Abstract [en]

    The maximum gas temperature below the ceiling is an important parameter for tunnel safety. The present study analyzed the characteristics of the maximum excess ceiling gas temperature driven by double fire sources in a naturally ventilated tunnel. A series of small-scale tunnel fire experiments were carried out with different fire separation distances and heat release rates. Theoretical analysis based on the equivalent virtual origin was also performed. The results showed that there exists only one peak gas temperature when the two fire plumes are merged before reaching the ceiling, while two peak gas temperatures can be observed when the two fire plumes are completely separated. The maximum excess gas temperature below the tunnel ceiling gradually decreases with an increasing fire separation distance in the plume merging region (S < Scp). When the fire separation distance increases further (S > Scp), the effect of the fire separation distance on the maximum gas temperature below the ceiling is very limited. Furthermore, a model using an equivalent fire source was proposed to predict the maximum excess gas temperature below the ceiling, considering different plume merging states. The present study contributes to the understanding of the maximum excess gas temperature characteristics of the smoke flow driven by double fires with an equal heat release rate in naturally ventilated tunnels. 

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  • 2.
    Li, Ying Zhen
    et al.
    Safety and Transport - Fire and Safety, RISE Research Institutes of Sweden, Borås, Sweden.
    Ingason, Haukur
    Safety and Transport - Fire and Safety, RISE Research Institutes of Sweden, Borås, Sweden.
    Arvidson, Magnus
    Safety and Transport - Fire and Safety, RISE Research Institutes of Sweden, Borås, Sweden.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Safety and Transport - Fire and Safety, RISE Research Institutes of Sweden, Borås, Sweden.
    Performance of various water-based fire suppression systems in tunnels with longitudinal ventilation2024In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, article id 104141Article in journal (Refereed)
    Abstract [en]

    Low pressure, medium pressure and high pressure water-based fire suppression systems were tested in a medium scale tunnel (scale 1:3). The primary objective was to investigate which of these systems are most effective in the suppression or control of different types of tunnel fires. The default low, medium and high pressure systems refer to full scale water flow rates of 10 mm/min, 6.8 mm/min and 3.7 mm/min, respectively. Some other water densities were also tested to investigate the effects, as well as different ventilation velocities and activation criteria. Several series of fire tests were conducted for different fire scenarios. The fire scenarios considered included idle wood pallet fires, loosely packed wood crib fires, loosely packed wood and plastic crib fires, and pool fires, with or without a top cover on the fuel load. Comparisons of the three default systems based on the three parameters: heat release rate, energy released and possibility of fire spread, show that the performance of the default low pressure system is usually the most effective based on the parameters studied. The default high pressure system usually yields results less effective in comparison to the default low pressure system. The performance of the default medium pressure system usually lies in between them. The high pressure system behaves very differently in comparison to the others, in terms of tunnel ventilation velocity, water density, operating pressure, and the presence of the top cover.

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  • 3.
    Li, Ying Zhen
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Blom, Joel
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Arvidson, Magnus
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Försth, Michael
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Mechanisms and performance of different fixed fire fighting systems in tunnels – summary of laboratory and tunnel fire tests2024Report (Other academic)
    Abstract [en]

    This report presents both small scale laboratory tests and tunnel fire tests carried out in a FORMAS project. Four series of small scale laboratory tests were conducted to obtain the material properties, burning properties, water spray distributions, and spray droplet size distributions. The main efforts were, by adopting the Froude scaling, seven series of tests conducted in a about 50 m long container tunnel with a scale of 1 to 3. This report presents results on the influence of low pressure, medium pressure and high pressure water-based fixed fire fighting systems (FFFSs) on fire development, fire spread to adjacent vehicles, structural protection, tenability, smoke control, spray deflection and spray resistances. The focus is to compare the performance of three default FFFSs and to evaluate the efficiency of each of the FFFS. The results show that the default low pressure FFFS performs well in term of suppressing the fire development, preventing the fire spread to nearby vehicles, providing tenable conditions for evacuation and rescue service, protecting tunnel structure and easing the problem with spray deflection due to tunnel ventilation. The default high pressure FFFS is usually on the opposite side while the default medium pressure FFFS usually lie in between.

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  • 4.
    Li, Ying Zhen
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Svensson, Robert
    Wahlqvist, Jonathan
    Van Hees, Patrick
    Lund University, Sweden.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Numerical modelling of water sprays and fire suppression in tunnels2024Report (Other academic)
    Abstract [en]

    This work aims to validate numerical modelling of water sprays against experiments carried out in this project. The focus has been on the influence of ventilation on water distributions on the tunnel floor, the influence of water sprays on control of smoke flow, and the modelling of pool fires and crib fires. Besides, full scale tunnel fires with FFFS in tunnels using longitudinal ventilation and point extraction ventilation systems are simulated and compared, as well recommendations for numerical modelling of such scenarios.

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  • 5.
    Sjöström, Johan
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Sokoti, Hasan
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Brandon, Daniel
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Pyrolysis and thermal properties of wood and high-density polyethylene2024Report (Other academic)
    Abstract [en]

    Sample tests were conducted to obtain thermal and kinematic parameters for wood and high-density polyethylene (HDPE) that were used in a series of intermediate scale tunnel fire tests with and without water-based fire suppressions systems. The thermal properties were measured using Transient Plane Source (TPS) and Transient Line Source (TLS). The pyrolysis kinetics parameters were tested based on Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Different methods were used to obtain pyrolysis kinetics parameters. Different oxygen concentrations exposed to samples were tested and the results showed its significant influence in the charring process.

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  • 6.
    Guo, Qinghua
    et al.
    Taiyuan University of Science and Technology China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Yan, Zhiguo
    Tongji University, Cina.
    Zhu, Hehua
    Tongji University, China.
    Numerical study on thermally driven smoke flow characteristics in long tunnels under natural ventilation2023In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 192, article id 108379Article in journal (Refereed)
    Abstract [en]

    The paper focuses on the flow structures and mass flow rates of thermally driven smoke flows induced by fires in long transportation tunnels under natural ventilation. The important influencing factors including heat release rate (HRR), tunnel width and height, are taken into consideration. The mechanism of the smoke flow movement is explored. The results show that for a fire in a long naturally ventilated transportation tunnel, there exists a critical point which is dependent on HRR and tunnel geometry. This critical point is defined as the location where the smoke layer thickness and the outgoing mass flow rate increase towards it and decrease after it. Further, it is found that the critical point moves farther away from the fire source in a wider or higher tunnel, while it lies closer to the fire source for a higher HRR. A correlation is proposed to estimate the location of the critical point. The outgoing mass flow rates along the tunnel are calculated using the two-layer flow model and well-mixed flow model of thermally driven flows, and the results indicate that these models produce satisfactory predictions of the mass flow rates if the vertical temperature profile is known. © 2023 The Authors

  • 7.
    He, Kun
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety. University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Fire spread among multiple vehicles in tunnels using longitudinal ventilation2023In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 133, article id 104967Article in journal (Refereed)
    Abstract [en]

    The characteristics of fire spread among multiple vehicles in tunnels using longitudinal ventilation were investigated by analyzing the experimental data from a series of fire tests in a 1:15 scale tunnel. Further, a simple theoretical model for gas temperature in a tunnel with multiple fire sources was proposed and used in analysis of the experimental data. The results showed that, for objects (wood piles) placed at a same separating distance downstream of the fire, the fire spread occurred faster and faster along the tunnel. Validation of the simplified temperature model for multiple fire sources was made against both model and full-scale tunnel fire tests. The model was further used to predict the critical conditions for fire spread to the second and third objects. Comparisons with the test data showed that average excess temperature of 465 K (or an equivalent incident heat flux of 18.7 kW/m2) could be used as the criterion for fire spread, and this was verified further by other model-scale tests and full-scale tests. The results showed that the critical fire spread distance monotonously increases with the heat release rate, and decreases with the tunnel perimeter. For multiple fire sources with equivalent heat release rates, as the separation distance between the first two fire sources increases, the critical fire spread distance from the second fire source to the third fire source decreases, but the total fire spread distance from the first fire source to the third one increases. If the total heat release rate at the site of a downstream fire source is greater than that at the former fire source, the critical fire spread distance becomes longer.

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  • 8.
    Zhao, Shengzhong
    et al.
    Shandong Jianzhu University, China.
    Yang, Haoran
    Shandong Jianzhu University, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Liu, Fang
    Chongqing University, China.
    Theoretical and numerical study on smoke descent during tunnel fires under natural ventilation condition2023In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 142, article id 105414Article in journal (Refereed)
    Abstract [en]

    The smoke stratification and the smoke descent along a tunnel are of the utmost importance for personnel evacuation. The paper investigates the smoke descent along a tunnel during a naturally ventilated tunnel fire. A theoretical model is developed to predict the smoke depth below the ceiling along the tunnel. A series of numerical simulations of full-scale tunnel fires are conducted to compare with the developed model, and some coefficients such as the entrainment coefficient are determined from the simulation results. The concepts of critical moment and critical distance are proposed to characterize the smoke descent along the tunnel. The results show that as the smoke spreads longitudinally, the smoke depth below the tunnel ceiling continuously increases. The temperature decay along the tunnel due to heat losses and air entrainment at the smoke layer interface is considered as the main parameter for the smoke descent. After the vitiated air returns back to the fire source, the smoke stratification in the entire tunnel will be significantly reduced. The smoke layer depth along the tunnel based on the temperature distribution is relatively stable in the process of smoke development, which is not sensitive to the HRR, but influenced by the tunnel width, and this method could only be used before the critical moment. The outcomes of this study could provide references for a better understanding of smoke movement in naturally ventilated tunnels and provide technical guidelines for fire safety designers.

  • 9.
    Hynynen, Jonna
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Quant, Maria
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Pramanik, Roshni
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Olofsson, Anna
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Arvidson, Magnus
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Andersson, Petra
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Electric Vehicle Fire Safety in Enclosed Spaces2023Report (Other academic)
    Abstract [en]

    Lately, concerns regarding fires in electric vehicles in enclosed spaces such as in road tunnels and parking garages have been raised and there are indications that parking of electric vehicles may be prohibited in some spaces. For the success of electromobility and the transition from fossil to renewable fuels, it is important to understand the risks and consequences of fires in electric vehicles and to provide technical solutions if necessary, so as not to hinder the widespread adoption of electric vehicles.

    In this work, a literature review on fires in vehicles has been conducted. The focus was on fires in enclosed spaces involving electric vehicles. A comprehensive risk assessment of electric vehicle fires was performed using systematic hazard identification. In addition, a workshop with representatives from three Swedish fire and rescue services was carried out to evaluate the emergency rescue sheets/response guides.

    The main conclusions are; That statistics regarding vehicle fires need to be improved, as of today the root causes of fires are missing in the data, which could potentially result in non-fact based regulations; The data studied in this work does not imply that fires in electric vehicles are more common than fires in internal combustion engine vehicles; Fires in electric vehicles and internal combustion engine vehicles are similar in regards to the fire intensity and peak heat release rates. 

    The most effective risk reductions measures on vehicle level, to decrease the number of fires in EVs, could not be defined based on that relevant data on the root causes of fires in EVs are currently not publicly accessible. The most effective risk reduction measures, to limit fire spread, on infrastructure level were the use of fire sprinkler systems, fire detection systems (early detection) and increased distance between parked vehicles.

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    Electric Vehicle Fire Safety in Enclosed Spaces
  • 10.
    Li, Ying Zhen
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Lönnermark, AndersRISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.Gehandler, JonatanRISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.Ingason, HaukurRISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Proceedings from the Tenth International Symposium on Tunnel Safety and Security2023Conference proceedings (editor) (Refereed)
    Abstract [en]

    This publication includes the Proceedings of the 10th International Symposium on Tunnel Safety and Security (ISTSS) held in Stavanger, Norway, April 26-28, 2023. The Proceedings include 45 papers and 16 posters. The papers were presented in 16 different sessions, i.e., Keynote sessions, Alternative Fuel Vehicle Safety, Risk Management & Explosion, Digitization, Explosion, Poster Corner, Ventilation 1&2, Fixed Fire Fighting Systems, Tenability and Evacuation, Emergency Management, Evacuation, Safety Management, Fire Dynamics and Resistance. Each day was opened by invited Keynote Speakers (in total five) addressing broad topics of pressing interest. The Keynote Speakers, selected as leaders in their field, consisted of Ove Njå (University of Stavanger, Norway), Vladimir Molkov (Ulster University, UK), Ulf Lundström (Swedish Transport Administration, Sweden), Mirjam Nelisse (TNO, The Netherlands), and Gunnar Jenssen (SINTEF, Norway). We are grateful that the keynote speakers were able to share their knowledge and expertise with the participants of the symposium.

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  • 11.
    Guo, Qinghua
    et al.
    RISE Research Institutes of Sweden. Tianjin Fire Research Institute of MEM, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Yan, Zhigou
    Tongji University, China.
    Zhu, Hehua
    Tongji University, China.
    Study on spilled liquid from a continuous leakage in sloped tunnels2022In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 120, article id 104290Article in journal (Refereed)
    Abstract [en]

    The study focuses on the behaviors of spilled liquid from a continuously leaked tank in sloped tunnels. Spillage width and area, which impact the potential heat release rates in case of fire, are investigated under different tunnel slopes and leakage flow rates by numerical simulations using interFoam based on the VOF method in the OpenFOAM toolbox following the validation. The simulation results show that the spillage width initially decreases rapidly and then slowly as the tunnel slope increases. Other parameters, including road surface roughness, physical properties of liquid and leakage source height, are also considered. Empirical models for predicting the spillage width and area are established considering both tunnel slope and leakage flow rate. The results may provide guidance for tunnel safety design and drainage system design affiliated with a tank leakage inside a tunnel. © 2021 The Author(s)

  • 12.
    Ingason, Haukur
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Arvidson, Magnus
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Jiang, Lei
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Fire tests with automatic sprinklers in an intermediate scale tunnel2022In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 129, article id 103567Article in journal (Refereed)
    Abstract [en]

    A series of 1:3 intermediate scale tunnel fire tests was performed to investigate the performance of a fully automatic sprinkler system in a road tunnel. The experiments were carried in a container tunnel with scaled geometry, using wood pallets as the fire source to simulate HGV fires. The activation of the sprinklers was simulated by using thermocouples that corresponded to a given Thermal Response Index (RTI) of a sprinkler bulb or a link. A total of 12 tests were carried out with varying longitudinal velocities (0.8–1.7 m/s), sprinkler activation temperatures (68–141 °C), water densities (2.9–8.7 mm/min) and types of arrangement of the fuel. The activation times, number of activated sprinklers, maximum heat release rates and other key parameters are presented and analyzed. The results show that the water density plays a key role in the performance of the automatic sprinkler systems tested. A high tunnel ventilation velocity, low water density and low sprinkler activation temperature are not recommended. © 2022 The Authors

  • 13.
    He, Kun
    et al.
    RISE Research Institutes of Sweden. University of Science and Technology of China, China.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety.
    Shi, Zhicheng
    University of Science and Technology of China, China.
    Yang, Hui
    University of Science and Technology of China, China.
    Zhang, Heping
    University of Science and Technology of China, China.
    Experimental study on flame characteristics of double fires in a naturally ventilated tunnel: Flame merging, flame tilt angle and flame height2021In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 114, article id 103912Article in journal (Refereed)
    Abstract [en]

    A series of fire tests was carried out to investigate the diffusion flame characteristics of double fires generated from separated burners in a naturally ventilated tunnel, considering different heat release rates and fire separation distances. The results show that the flame tilt angle, as well as the horizontal projected flame length, first increases with fire separation distance and then remains constant, but the vertical flame length first decreases and then remains constant, which is different from two fires in free spaces where flames do not tilt when the separation distance is relatively long. This difference is caused by the non-dimensional fire induced air flow velocity in the tunnel, which is mainly related to the tunnel cross-section dimensions and burner radius. Three regions can be identified, i.e. flame vertical merging, plume vertical merging and non-merging with flame tilted. The critical flame merging separation distance, estimated by the flame merging probability, is greater than that of two fires in an open environment due to the fire-induced air flows. The merging flame height is lower than that of a single fire with a same heat release rate. A correlation was proposed to estimate flame height of two fires in a tunnel by the modified non-dimensional heat release rate using an air entrainment perimeter as the characteristic length. This work enhances the understanding of diffusion flame behaviors of double fires in naturally ventilated tunnels.

  • 14.
    Guo, Qinghua
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Chemistry, Biomaterials and Textiles. Tongji University, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Yan, Zhiguo
    Tongji University, China.
    Zhu, Hehua
    Tongji University, China.
    Theoretical and numerical study on mass flow rates of smoke exhausted from short vertical shafts in naturally ventilated urban road tunnel fires2021In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, article id 103782Article in journal (Refereed)
    Abstract [en]

    The study focuses on the mass flow rate of the buoyancy-driven gases exhausted from the shaft in naturally ventilated urban road tunnel fires. Theoretical analyses and numerical simulations are performed. The model to predict the mass flow rate of the incoming smoke exhausted by the nearest shaft is developed by considering that the smoke is exhausted along the four sides of the shaft separately. Based on the heat balance between the incoming smoke exhausted and the total gas flow exhausted, the model to estimate the total mass flow rate exhausted from the shaft (both smoke and entrained air) is also established. Meanwhile, a series of numerical simulation in a naturally ventilated tunnel considering the heat release rate (HRR), the shaft height, shaft length and width, shaft location was carried out. The simulation results show that the shaft height has a limited contribution to the mass flow rate of the incoming smoke exhausted while a larger shaft cross-sectional area shows a favorable performance in exhausting the smoke. Further, the air entrainment into the shaft increases with both the shaft height and shaft cross-sectional area. Comparisons of the mass flow rates of the incoming smoke and the total mass flow rates exhausted between simple calculations and simulations are made, showing that the simple models perform well. Further, it is found that there exist two regimes for the total mass flow rate corresponding to different smoke modes in the shaft (complete plug-holing, plug-holing and without plug-holing), which is caused by the different driven forces in the shaft. The outcomes of this work could provide some guidance for the design of vertical shaft and smoke control in naturally ventilated tunnel in urban area.

  • 15.
    Liu, Yongqiang
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research. Chongqing University, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Liu, Fang
    Chongqing University, China.
    Control of thermal-driven smoke flow at stairways in a subway platform fire2021In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 165, article id 106937Article in journal (Refereed)
    Abstract [en]

    To manage thermal-driven smoke from fires in a subway station, a mechanical ventilation system is usually installed. Such a system normally consists of an air supply system and a smoke exhaust system. In case of a platform fire, the ventilation systems will be activated to control the smoke and to provide better environmental conditions for personnel evacuation. This paper conducted a theoretical analysis and a series of CFD simulations to study the critical velocity (minimum air velocity) at the stairways for preventing smoke propagating from the platform to the upper floor through the stairways in case of a platform fire. Correlations for critical velocities are established for two typical types of stairways (i.e., with and without side slabs). It is found that the critical velocity is well correlated with the heat release rate by a 1/3 power law function for both types of stairways, but it varies with the height of the smoke curtain at the stairway by a 1.375 and a 2.55 power law function for stairways with and without side slabs, respectively. The results may serve as a useful reference for smoke control in subway platform fires.

  • 16.
    Yao, Yongzheng
    et al.
    RISE Research Institutes of Sweden. China University of Mining and Technology, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Zhang, Heping
    University of Science and Technology of China, China.
    Theoretical and numerical study on influence of wind on mass loss rates of heptane pool fires at different scales2021In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 120, article id 103048Article in journal (Refereed)
    Abstract [en]

    The paper presents an investigation of the influence of wind on the mass loss rate per unit area (MLRPUA) of heptane pool fires at different scales. This work was done by a theoretical analysis and numerical simulations. Correlations are developed to show how results from a small-scale pool fire might be used to estimate MLRPUA for a large-scale pool fire. The calculated results demonstrate that in the presence of wind, the MLRPUA in large-scale pool fires (side length>1 m) does not increase several times as the small-scale tests have revealed, and the 1.5 m heptane square pool fire only varies within a range of −20% and 30% of that in the free burn. Numerous heptane pool fires with different pool scales and wind speeds were simulated using FDS (Fire Dynamics Simulator). Results indicate that within a certain range of Froude number (0–2.5), the overall variation trend of MLRPUA with wind speed varies from increasing significantly to decreasing as the pool scale increases gradually (0.15 m–6 m). For large-scale heptane pool fires, the MLRPUA most likely fluctuates within ±40% for a wide range of Froude number. The outcomes of this study could contribute to improving the understanding of burning characteristics of different scales of pool fires under windy conditions in an open environment. 

  • 17.
    Li, Ying Zhen
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Parametric study of design fires for tunnels with water-based fire suppression systems2021In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 120, article id 103107Article in journal (Refereed)
    Abstract [en]

    A series of tests was carried out to investigate the influence of different parameters on design fires for tunnels with water-based fire suppression systems in a 1:4 scale tunnel. The key parameters tested included fuel load covers, activation time, water density, nozzle type, ventilation velocity, sprinkler section length and tunnel width. Analyses of test data are presented with a focus on the influence of these parameters on the design fire. The main findings are that the fuel load covers, activation time and ventilation velocity all play significant roles in the fire development. Further, suggestions on design fires for tunnels with water-based fire suppression systems are proposed. © 2020 The Authors

  • 18.
    Guo, Qinghua
    et al.
    RISE Research Institutes of Sweden. Tongji University, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Yan, Zhiguo
    Tongji University, China.
    Zhu, Hehua
    Tongji University, China.
    Theoretical studies on buoyancy-driven ceiling jets of tunnel fires with natural ventilation2020In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 119, article id 103228Article in journal (Refereed)
    Abstract [en]

    The paper presents a theoretical study on the ceiling jets induced by small fires in tunnels. The ceiling jet thickness, temperature rise and velocity are analyzed theoretically with Non-Boussinesq approximation. The study focuses on the radial and one-dimensional ceiling jets. Numerical solutions in the radial region and one-dimensional shooting region are obtained and new analytical solutions in the critical flow region are achieved. Analytical solutions indicate that the ceiling jet thickness increases with distance away from the fire source, which largely differs from the existing models implying that the ceiling jet thickness in the one-dimensional critical flow remains constant. Additionally, impacts of the air entrainment, friction and heat transfer on the ceiling jet are analyzed. It is found that in the radial and one-dimensional shooting flow regions, the air entrainment has a much more significant effect than the friction and heat transfer. However, in the one-dimensional critical flow region, the impact of air entrainment seems to be negligible and the flow is dominated by the friction and heat transfer. Further, validation of the present theory is made by comparing with previous theories, semi-empirical models, and experiments. The results show that the present theory provides a good prediction of the ceiling jet properties with natural ventilation for a small fire. © 2020 The Authors

  • 19.
    Yao, Yongzheng
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety. University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Scale effect of mass loss rates for pool fires in an open environment and in tunnels with wind2019In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 105, p. 41-50Article in journal (Refereed)
    Abstract [en]

    This paper investigates the influence of wind on mass loss rate per unit area (MLRPUA) of fuel-controlled pool fires both in an open environment and inside tunnels and the scale effect of pool fires is also investigated. Large pool fires with a diameter D greater than 1 m (D > 1 m) are of key concern but small pool fires (D < 1 m) are also considered for comparison. This is done by analyzing large amounts of experimental data from the literature. Results show that for small pool fires (D < 1 m) in an open environment, increasing wind speed tends to increase the MLRPUA, especially for pools with D < 0.2 m, where the MLRPUA could increase significantly with the increase of wind speed. But when small pool fires occur in tunnels, the results are more complex. When the ratio of effective tunnel height to pool diameter is less than 3, increasing wind speed tends to decrease the MLRPUA. When this ratio is greater than 3, the influence of wind on MLRPUA of pool fires in tunnels is similar to that in an open environment. The influence of wind on the MLRPUA decreases for larger pool diameters, no matter whether the pool fire occurs in an open environment or in a tunnel. For large pools with D > 1 m, the MLRPUA is not affected significantly by increasing wind speed and most likely varies within 30% for a wide range of wind speeds based on the test data collected. This influence is far less than the values concluded by previous studies based on small pool fire experiments. The outcome of this study contributes to improving the understanding of burning characteristics of pool fires under windy conditions, especially large pool fires, which are much more meaningful than small pool fires from the perspectives of fire protection engineering and fire hazard assessment.

  • 20.
    Yao, Yongzhenh
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety. University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Cheng, X.
    University of Science and Technology of China, China.
    Numerical study on overall smoke control using naturally ventilated shafts during fires in a road tunnel2019In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 140, p. 491-504Article in journal (Refereed)
    Abstract [en]

    This paper studies the overall smoke control of natural ventilation systems with vertical shafts during fires in a common road tunnel by numerical modelling. The variables studied include the heat release rate, longitudinal fire location along the tunnel, length of shafts and the interval between two shafts. Simulation results indicate that the total smoke spread length on both sides of fire source is closely independent of the heat release rate and longitudinal fire locations. For a given dimensionless shaft interval (the ratio of the shaft interval to shaft length), with the increase of shaft length, the smoke spread length firstly increases, reaching a maximum at 12 m, and then decreases significantly until 18 m. For a fire less than 30 MW, the first shaft pair on both sides of fire source prevents the critical-temperature smoke (270 °C) from spreading beyond this shaft. For a 100 MW fire, in the cases with shorter shaft lengths (L shaft ≤9 m), the critical-temperature smoke can't be controlled between the first shaft pair. The gas temperature at human height (1.8 m) is less than 60 °C in all cases with shafts. Downdraught occurs when the smoke front stabilizes at the bottom of a shaft and the buoyancy force could be too low to overcome the kinetic pressure of the air flow flowing into this shaft, consequently destroying the structure of smoke layer. In most scenarios, the total exhaust area of shafts that is required to exhaust all the smoke is about 100 m 2 . The first shaft pair plays a critical role to exhaust the smoke, and its exhaust efficiency is also affected significantly by the shaft length. This study investigates how to control the smoke by using vertical shafts in a road tunnel fire and the conclusions are useful to tunnel fire protection engineering.

  • 21.
    Ingason, Haukur
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Large scale tunnel fire tests with different types of large droplet fixed fire fighting systems2019In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 107, p. 29-43Article in journal (Refereed)
    Abstract [en]

    The paper presented the main results of large-scale fire tests with different types of fixed firefighting systems (FFFS) conducted in the Runehamar tunnel in June 2016. The background to the tests, the performance of the different systems, and conclusions regarding the efficiency of the systems were presented. The fire load consisted of 420 standardised wooden pallets and a target of 21 wooden pallets. Five of the tests were carried out with a 30 m long deluge zone delivering varying water densities using three different types of side-wall nozzles with an interval distance of 5 m. One test with 93 °C glass-bulb automatic sprinklers in the same zone was also conducted. In the five deluge tests, the detection system was simulated using thermocouples in the tunnel ceiling. The alarm was registered when the ceiling gas temperature reached 141 °C, and the system was activated manually after a delay of 4 min. The protection goal of the system was to prevent fire spread to a target positioned 5 m from the rear of the main fuel area, and to ensure that the fire did not exceed 30 MW in size. The system setups tested were found to meet these goals.

  • 22.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Study of fire and explosion hazards of alternative fuel vehicles in tunnels2019In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 110, article id 102871Article in journal (Refereed)
    Abstract [en]

    This paper presents results concerning fire and explosion hazards of various alternative fuel vehicles in tunnels. The alternative fuels are divided into four types: liquid fuels, liquefied fuels, compressed gases, and electricity, and detailed parameters are obtained. Three important types of fire hazards: pool fires, jet fires and fireballs are identified and investigated. From the perspective of pool fire size, the liquid fuels pose equivalent or even lower fire hazards compared to traditionally used fuels, but the hazards of liquefied fuels may be higher. For pressurized tanks, fires are generally much larger in size but shorter in duration. The gas releases from pressure relief devices and the resulting jet flames are highly transient. For hydrogen vehicles, the fire sizes are significantly higher compared to CNG tanks, while flame lengths are only slighter longer. Analysis of the peak overpressure in case of an explosion in a tunnel shows that the consequences of tank rupture and BLEVE are relatively tolerable for a position further than 100 m away, but the situations in case of a cloud explosion are highly severe and intolerable for tunnel users in most cases. These hazards need to be carefully considered in both vehicle safety design and tunnel fire safety design. 

  • 23.
    Yao, Yongzheng
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety. University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Cheng, Xudong
    University of Science and Technology of China, China.
    The characteristics of under-ventilated pool fires in both model and medium-scale tunnels2019In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 87, p. 27-40Article in journal (Refereed)
    Abstract [en]

    This paper investigates the characteristics of under-ventilated fires in tunnels. This was done by using both model and medium-scale tunnels. The fuels used were heptane and xylene. The mass loss rates per unit area, ventilation rates from tunnel inlet, flame characteristics, O 2 , CO and CO 2 concentrations, optical densities and heat release rates were measured and recorded. Results show that the fire behaviors in under-ventilated tunnel fires are different from that in well-ventilated fires. In under-ventilated fires, the mass loss rate per unit area is found to decrease during identical periods due to the low oxygen concentration resulting from the low ventilation rate and vitiation, meanwhile the flame size dramatically reduces with a lifted and fluttering flame. This was clearly observed in model-scale tests, but due to limited optical view there was no possibility to observe this in the medium-scale tests. As a result, the ventilation rate approaches the amount required for complete combustion of vaporized fuel. This indicates that the combustion has converted from ventilation-controlled to fuel-controlled. No significant increase in CO production is observed in under-ventilated fires. Besides, the equivalence ratio and combustion efficiency were analyzed in order to judge whether the combustion is fuel-controlled or ventilation-controlled. This study provides new experimental information that contributes to improving the understanding of characteristics of under-ventilated fires in tunnel and can help firefighters to make right judgements and take related protective measures during the rescue processes.

  • 24.
    Yao, Yongzheng
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety. University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Lönnermark, Anders
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Cheng, Xudong
    University of Science and Technology of China, China.
    Study of tunnel fires during construction using a model scale tunnel2019In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 89, p. 50-67Article in journal (Refereed)
    Abstract [en]

    The paper presents a study on the characteristics of tunnel fires during construction. A model-scale tunnel was built and fire tests were conducted. The tunnel consists of an inclined access tunnel and a horizontal main tunnel. The main tunnel has two dead ends (excavation faces) and the only opening is from one side of the access tunnel. Propane gas burner and the fibre board soaked with the heptane were used as fuels. The flame characteristics, O 2 and CO volume fraction and gas temperature were measured and recorded. Two typical characteristics of self-extinguishment and smoke spread were found in the tunnel fires during construction. Results indicate that when a fire occurs in the horizontal main tunnel, the critical equivalence ratio for the occurrence of self-extinguishment is within 0.28–1.38 for the propane gas burner and 1.11–3.6 for the fibre board soaked with heptane. The difference is related to the burning behavior of the different fuels used. The fire location in the horizontal tunnel also has a significant influence on the fire development. A well-ventilated fire at the center of the horizontal tunnel becomes under-ventilated due to vitiation when it is located at the closed end of the horizontal tunnel. Besides, when a fire occurs at the closed end of the horizontal main tunnel, the stratification of smoke is destroyed after hitting the closed end, and then the smoke seems to spread over the entire cross section of the tunnel. The smoke spread velocity is found to be proportional to the ventilation rate. However, when a fire occurs at the closed end of the inclined access tunnel (lower end), the fire does not self-extinguish, even when the ventilation rate is 0 m 3 /s. The corresponding smoke spread velocity is higher than that in the horizontal main tunnel. The outcomes of this study provide new experimental information that contributes to improve the understanding of characteristics of tunnel fires during construction and can help firefighters to make better decisions during the rescue processes.

  • 25.
    Zhao, Shengzhong
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety. Chongqing University, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Kumm, Mia
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Liu, Fang
    Chongqing University, China.
    Re-direction of smoke flow in inclined tunnel fires2019In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 86, p. 113-127Article in journal (Refereed)
    Abstract [en]

    The re-direction of smoke flow in inclined tunnel fires refers to the phenomenon that the smoke flow direction suddenly changes due to the changes of thermal buoyancy or outside pressure or the activation of fans. This poses special risk for fire rescue services fighting fires in tunnels. Both small-scale tunnel fire tests (28 scenarios) and numerical simulations of full-scale tunnel fires (31 scenarios) were conducted to study this special phenomenon. A one-dimensional model was used to predict the flow velocity in the inclined tunnels, based on two different methods for calculating the mean smoke temperature (Method I and Method II, respectively). Results show that the smoke flow direction could be well predicted by the model with Method II. When the ventilation velocity is relatively large and the flow tends to be one dimensional, both methods produce similar results. Further, the influences of important factors on the re-direction of smoke flows were systematically analyzed. These factors include heat release rate, tunnel slope, tunnel length, friction factor, tunnel cross sectional area and fire source location.

  • 26.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Discussions on critical velocity and critical Froude number for smoke control in tunnels with longitudinal ventilation2018In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 99, p. 22-26Article in journal (Refereed)
    Abstract [en]

    Determination of critical velocity is a key issue for smoke control in any tunnel with longitudinal ventilation. The critical Froude model using single Froude number of 4.5 has for decades been widely used in engineering applications. This value was originally used by Danziger and Kennedy and they argued that the critical Froude number obtained by Lee et al. was in a range of 4.5 and 6.7 and therefore a conservative value of 4.5 was obtained. This paper explores the validity of using single critical Froude number of 4.5 by investigating the original sources and comparing it to recent research results. It was found that the value of 4.5 obtained in the original source corresponds to a large tunnel fire and it correlates well with data from other literature within a narrow range of large fire sizes. Using this value produces a significantly lower critical velocity for a wide range of fire sizes and therefore it is not conservative. The Froude number of 6.7 obtained by Lee et al. corresponds to another Froude number with a different definition and it is therefore not comparable with the value of 4.5. It is found that the use of a single value of 4.5 for the critical Froude number is not reasonable in calculation of the critical velocity for smoke control in tunnels with longitudinal ventilation.

  • 27.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Influence of fire suppression on combustion products in tunnel fires2018In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 97, p. 96-110Article in journal (Refereed)
    Abstract [en]

    A series of model scale tunnel fire tests was carried out to investigate effects of the fire suppression system on production of key combustion products including CO and soot. The key parameters accounted for in the tests include fuel type, ventilation velocity and activation time. The results show that fire suppression indeed has influence on production of combustion products especially for cellulose fuels. In case that the fire is not effectively suppressed, e.g. when the water density is too low or activation is too late, the CO concentration and visibility could be worse than in the free-burn test. From the point of view of production of combustion products, only fire suppression systems with sufficient capability and early activation are recommended to be used in tunnels.

  • 28. Li, Ying Zhen
    Study of fire and explosion hazards of alternative fuel vehicles in tunnels2018Report (Other academic)
    Abstract [en]

    An investigation of fire and explosion hazards of different types of alternativefuel vehicles in tunnels is presented. The different fuels are divided into four types:liquid fuels, liquefied fuels, compressed gases, and electricity, and detailed parameters are obtained. Three types offire hazards for the alternativefuel vehicles: pool fires, jet fires and fireballs are identified andinvestigated in detail. Fromthe perspective of pool fire size, the liquid fuels pose equivalent or evenmuch lower fire hazards compared to the traditionally used fuels, but theliquefied fuels may pose higher hazards. For pressurized tanks, the fires are generally much larger in size butshorter in duration. The gas releases from pressure relief devices and the resulting jet firesare highly transient. Forhydrogen vehicles, the fire sizes are significantly higher compared to CNGtanks, while flame lengths only slighter longer. Investigation of the peakoverpressure in case of an explosion in a tunnel was also carried out. Theresults showed that, for the vehicles investigated, the peak overpressure of tankrupture and BLEVE are mostly in a range of 0.1 to 0.36 bar at 50 m away. Thesituations in case of cloud explosion are mostly much more severe andintolerable. These hazards need to be carefully considered in both vehiclesafety design and tunnel fire safety design. Further researches on thesehazards are in urgent need.

    Download full text (pdf)
    RISE Rapport 2018:20
  • 29.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Model scale tunnel fire tests on maximum ceiling gas temperature for structural protection2018Report (Other academic)
    Abstract [en]

    Model scale tests with varying materials as tunnel structure were carried out to further study the theoretical model of maximum gas temperature for structural protection. New correlation for calculation of air mass flow rate is introduced. Test results showed that the maximum ceiling gas temperatures increases with the increasing heat release rate and decreases with the increasing tunnel width and thermal inertia of the tunnel linings. Higher ventilation velocity may also result in slightly higher temperatures for large fires.

    Comparisons of model scale tests and theoretical models showed that the theoretical models predict the maximum ceiling gas temperature very well. A fire with a fixed heat release rate or a time-varying heat release rate, the effects of tunnel structure, tunnel ventilation, tunnel width and fire size have been well considered by the model. Comparisons of other model and full scale tests with theoretical models further verified this.

    Download full text (pdf)
    fulltext
  • 30.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Tunnel fire safety: editorial2018In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 97, p. 85-86Article in journal (Other academic)
  • 31.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Overview of research on fire safety in underground road and railway tunnels2018In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 81, p. 568-589Article in journal (Refereed)
    Abstract [en]

    In the past two decades, the interest in fire safety science of tunnels has significantly increased, mainly due to the rapidly increasing number of tunnels built and the catastrophic tunnel fire incidents occurred. This paper presents an overview of research on fire safety in underground road and railway tunnels from the perspectives of fire safety design. The main focuses are on design fires, structural protection, smoke control and use of water-based fire suppression systems. Besides, some key fire characteristics, including flame length, fire spread, heat flux and smoke stratification, are discussed.

  • 32.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Jiang, Lei
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Influence of tunnel slope on smoke control2018Report (Other academic)
    Abstract [en]

    The critical velocity and backlayering length in sloped tunnels are investigated by numerical simulations using FDS. Simulation in two full-scale tunnels, with negative slopes ranging up to -18 % and heat release rates from 5 to 100 MW were carried out.

    The results show that NFPA 502 equation significantly overestimates the effect of negative slopes.

    The equation proposed by Atkinson and Wu is found to be in closer agreement with the results. A simplified correlation, i.e. Eq. (12), is proposed and recommended for practical use.

    The previous correlation for dimensionless backlayering length, Eq. (3), is valid for tunnels of various slopes and aspect ratios, and can be used for prediction of backlayering length.

    Download full text (pdf)
    fulltext
  • 33.
    Ingason, Haukur
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Spilled liquid fires in tunnels2017In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 91, p. 399-406Article in journal (Refereed)
    Abstract [en]

    The study focuses on release of liquids inside tunnels from tankers containing dangerous good. Experiments and analysis from large scale tests are presented. The tests include different leakage rates, leakage type, liquids, spillage sizes on sloping surfaces and heat release rates. Models for estimation of leakage rates, spillage sizes and heat release rates for different scenarios are presented. The results are important to use in the design of active fire protections systems in tunnels including ventilation, fixed fire-fighting and drainage systems.

  • 34.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Effect of cross section on critical velocity in longitudinally ventilated tunnel fires2017In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, p. 303-311Article in journal (Refereed)
    Abstract [en]

    Numerical and theoretical work was conducted to investigate the effect of tunnel cross section on critical velocityfor smoke control in longitudinally ventilated tunnel fires. The results show that for small fires, the criticalvelocity decreases with both the increasing tunnel height and tunnel width. For large fires, the critical velocitysignificantly increases with the increasing tunnel height but is independent of tunnel width. Differentcalculation models are compared with a focus on effect of tunnel cross section. A new correlation is proposedto account for the effect of tunnel width based on the previous model.

  • 35.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Scaling of wood pallet fires2017In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 88, p. 96-103Article in journal (Refereed)
    Abstract [en]

    §method for scaling time-resolved burning behaviors of wood pallet fires has been developed. A series of validation tests was carried out in two different scales and the time-resolved heat release rates were obtained and compared. The results show that the scaling method proposed works very well. The scaling method proposed could be applied to general wood pallets.

  • 36.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Analysis of Muskö tunnel fire flows with automatic sprinkler activation2017Report (Other academic)
    Abstract [en]

    The focus of the present study is analyzing the best position of a sprinkler nozzle in a tunnel cross-section in the Muskö tunnel, south of Stockholm, Sweden. Activation of the sprinklers installed along the centerline and along the sidewall is investigated through analysis of full scale experiments and by three dimensional numerical modelling. Then the tunnel velocity is analyzed by one dimensional numerical modelling for various fire locations in the Muskö tunnel. For both activating the automatic sprinklers nearby the fire and avoiding activation of the sprinklers further downstream, the automatic sprinklers are recommended to be installed along the centerline of the tunnel. It has also been found that the tunnel velocity varies significantly with the fire location. When the fire is on the left side of the tunnel, the flow velocity mostly remains in a range of 1 m/s (positive or negative) within the first 10 minutes, which helps early activation of the automatic sprinklers. When the fire is on the right side of the tunnel, the flow velocity mostly remains within a range of -1 m/s and 1 m/s within the first 5 minutes, and the velocity mostly increases to 2 m/s at around 10 min. Therefore, the scenario for fire located on the left side is better than that for fire on the right side, especially when it is located between the middle of the right section and the right portal. As one typical case with fire on the right side, the tunnel velocity maintains at 1 m/s for the first 5 min and gradually increases to 2 m/s at 10 min. Under such conditions, the automatic sprinkler system is expected to perform well. 

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    RISE Rapport 2017:51
  • 37.
    Fan, Chuan Gang
    et al.
    University of Science and Technology of China, China; Hefei University of Technology, China.
    Ji, Jie
    University of Science and Technology of China, China.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Sun, Jin Hua
    University of Science and Technology of China, China.
    Experimental study of sidewall effect on flame characteristics of heptane pool fires with different aspect ratios and orientations in a channel2017In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 36, no 2, p. 3121-3129Article in journal (Refereed)
    Abstract [en]

    A series of small scale tests was conducted to investigate the influence of sidewall on flame characteristics of heptane pool fires in a channel, considering pool shape (aspect ratio: 1, 2, 4 and 8) and pool orientation relative to sidewall. Distance between fire and sidewall was changed systematically. Both transverse flame development (along the direction of channel width) and longitudinal flame development (along the direction of channel length) were recorded by digital video. Results show that for a fixed fire location, the heat release rate increases with the increasing pool aspect ratio (namely a larger pool perimeter), which indicates more air entrainment and more intense combustion. In wall fire cases, when the long pool rim is perpendicular with channel sidewall, the flame can obtain more air entrainment with a weaker boundary restriction from the sidewall, compared to the case with the long pool rim being parallel with sidewall. Comparison of some previously established correlations based on various experimental conditions with our test results is made. Due to the fact without considering sidewall effect and fuel shape on the air entrainment of fire plume, the classic correlations need to be further improved. Therefore, an integral flame length model considering both sidewall effect and fuel shape is developed, which correlates well with all the data from cases with various pool positions, orientations and aspect ratios. © 2016 The Combustion Institute. Published by Elsevier Inc.

  • 38.
    Lönnermark, Anders
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Li, Ying Zhen
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Kumm, Mia
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Fire development in a 1/3 train carriage mock-up2017In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 91, p. 432-440Article in journal (Refereed)
    Abstract [en]

    To study what parameters that control the initial fire spread and the development to local flashover in a metro carriage, a total of six fire tests were conducted in a mock-up of a metro carriage that is about 1/3 of a full wagon length. They were carried out under a large scale calorimeter in a laboratory environment. The focus was on the initial fire development in a corner scenario using different types of ignition source that may lead to a fully developed fire. The ignition sources used were either a wood crib placed on a corner seat or one litre of petrol poured on the corner seat and the neighbouring floor together with a backpack. The amount of luggage and wood cribs in the neighbourhood of the ignition source was continuously increased in order to identify the limits for flashover in the test-setup. The tests showed that the combustible boards on parts of the walls had a significant effect on the fire spread. In the cases where the initial fire did not exceed a range of 400–600 kW no flashover was observed. If the initial fire grew up to 700–900 kW a flashover was observed. The maximum heat release rate during a short flashover period for this test set-up was about 3.5 MW. The time to reach flashover was highly dependent on the ignition type: wood cribs or backpack and petrol. A full developed carriage fire was achieved as a result of intense radiation from the flames and ceiling smoke layer. This was mostly dependent on the amount of fire load nearby the ignition source and how strong the vertical flame spread on the high pressure laminate boards mounted to walls and ceiling above the ignition source was, leading to a ceiling flame. In such cases, the seats alone did not contain sufficient fuel for the fire to spread within the train, and additional fuel (luggage) is required near the seats. For fully developed carriage fires, the fire starting on the seat in the corner spread to the opposite seat on the same side of the aisle, then horizontally spread to seats on the other side of the aisle, and finally a longitudinal flame spread along the carriage was observed. When and where the fire stopped or whether it reached a fully developed stage was mostly dependent on the amount of fire load nearby the ignition source and how strong the vertical flame spread on the high pressure laminate boards mounted to walls and ceiling above the ignition source was.

  • 39.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Huang, Chen
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Anderson, Johan
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Svensson, Robert
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden (2017-2019), Safety and Transport, Safety.
    Husted, Bjarne
    Lund University, Sweden.
    Runefors, Marcus
    Lund University, Sweden.
    Wahlqvist, Jonatan
    Lund University, Sweden.
    Verification, validation and evaluation of FireFOAM as a tool for performance design2017Report (Other academic)
    Abstract [en]

    The open source CFD code FireFOAM has been verified and validated against analytical solution and real fire tests. The verification showed that FireFOAM solves the three modes of heat transfer appropriately. The validation against real fire tests yielded reasonable results. FireFOAM has not been validated for a large set of real fires, which is the case for FDS. Therefore, it is the responsibility of the user to perform the validation, before using the code. One of the advantages of FireFOAM compared to the Fire Dynamic Simulator is that FireFOAM can use unstructured grid. FireFOAM is parallelised and scales reasonable well, but is in general considerably slower in computation speed than the Fire Dynamic Simulator. Further, the software is poorly documented and has a steep learning curve. At present it is more a tool for researchers than for fire consultants.

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  • 40.
    Li, Ying Zhen
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    Ingason, Haukur
    RISE - Research Institutes of Sweden, Safety and Transport, Safety.
    New models for calculating maximum gas temperatures in large tunnel fires2016Report (Other academic)
    Abstract [en]

    The work presented in this report focuses on estimating maximum gas temperatures at ceiling level during large tunnel fires. Gas temperature is an important parameter to consider when designing the fire resistance of a tunnel structure. Earlier work by the authors has established correlations between excess ceiling gas temperature and effective tunnel height, ventilation rate, and heat release rate. The maximum possible excess gas temperature was set as 1350°C, independent of the tunnel structure and local combustion conditions. As a result of this research, two models have been developed to better estimate possible excess maximum gas temperatures for large tunnel fires in tunnels with differing lining materials and structure types (e.g. rock, concrete). These have been validated using both model- and full-scale tests. Comparisons of predicted and measured temperatures show that both models correlate well with the test data. However, Model I is better and more optimal, due to the fact that it is more conservative and easier to use. The fire duration and flame volume are found to be related to gas temperature development. In reality, the models could also be used to estimate temperatures in a fully developed compartment fire.

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  • 41.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    CFD modellering av brandförlopp i tunnelbanevagnar under olika ventilationsförhållanden2016In: Brandposten, no 54, p. 20-21Article in journal (Other academic)
  • 42.
    Li, Ying Zhen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Ingason, Haukur
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Design Fires for Tunnels with Water-Based Fire Suppression Systems2016In: Proceedings from the 7th International Symposium on Tunnel Safety and Security, 2016, p. 305-316Conference paper (Other academic)
    Abstract [en]

    A series of tests were carried out to investigate design fires for tunnels with water-based fire suppression systems under different conditions in a 1:4 model scale tunnel. The key parameters including fuel load covers, activation time, water flow rate, nozzle type, ventilation velocity, sprinkler section length and tunnel width were tested. Technical information and analyses of test data are presented with a focus on the influence of these different parameters on the design fire in a tunnel with a water-based fire suppression system. Further, guidance for the design fires in tunnels with water-based fire suppression systems is proposed.

  • 43.
    Ingason, Haukur
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Appel, Glenn
    Swedish Transport Administration, Sweden.
    Lundström, Ulf
    Swedish Transport Administration, Sweden.
    Becker, Conny
    Brandskyddslaget AB, Sweden.
    Large Scale Tunnel Fire Tests with Large Droplet Water-Based Fixed Fire Fighting System2016In: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099, Vol. 52, no 5, p. 1539-1558Article in journal (Refereed)
    Abstract [en]

    This paper presents the main results of six large scale fixed fire fighting system tests that were carried out in the Runehamar tunnel in September 2013. It describes the background and the performance of the system. The main fire load consisted of 420 standardized wood pallets and a target consisting of a pile of 21 wood pallets placed 5 m from the rear end of the main fire load. The purpose was to investigate possible fire spread. The water spray system is a deluge zone system delivering 10 mm/min in the activated zone. The detection system was simulated with use of thermocouple in the tunnel ceiling. The alarm was registered when the ceiling gas temperature was 141°C. After alarm was obtained the system was activated manually after a given delay time that was varied in the tests. The heat release rates in tests with fire suppression were reduced to 20–45 MW compared to 100 MW estimated for a free-burn test or 75 MW in test 6 with a failure of activation. Fire spread to the target was prevented after fire suppression. 

  • 44.
    Ingason, Haukur
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Bobert, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Fullskaliga försök med brandbekämpningssystem i tunnlar2016In: Brandposten, no 55, p. 4-6Article in journal (Other academic)
  • 45.
    Li, Ying Zhen
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Ingason, Haukur
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Influence of ventilation on tunnel fires with and without water-based suppression systems2016Report (Refereed)
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  • 46.
    Ingason, Haukur
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Bobert, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Large scale fire tests with different types of fixed fire fighting systems in Runehamar tunnel2016Report (Refereed)
    Abstract [en]

    The report presents the main results of the six large-scale tests with different types of fixed firefighting system (FFFS) that were carried out in the Runehamar tunnel in June 2016. It describes the background to the tests and the performance of the different systems, and draws conclusions regarding the efficiency of the systems. The fire load consisted of 420 standardised wooden pallets and a target of 21 wooden pallets. Five of the tests were carried out with a 30 mlong deluge zone delivering varying water densities using three different types of side-wall nozzle and an interval distance of 5 m. One test with 93°C glass-bulb nozzles (sprinkler head) in the same zone was also conducted. In the five deluge tests, the detection system was simulated using thermocouples in the tunnel ceiling. The alarm was registered when the ceiling gas temperature reached 141°C, and the system was activated manually after a delay of 4 minutes. The protection goal of the system was to prevent fire spread to a target positioned 5 m from the rear of the main fuel area, and to ensure that the fire did not exceed 30 MW in size. The system setups tested were found to meet these goals.

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  • 47.
    Ingason, Haukur
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Brandteknik, skydd (BRs ).
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    A New Methodology of Design Fires for Train Carriages Based on Exponential Curve Method2016In: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099, Vol. 52, no 5, p. 1449-1464Article in journal (Refereed)
    Abstract [en]

    Design fires have great influences on the fire safety concepts and safety measures, and are the basis for any assessment and calculation in tunnel fire safety design. A new methodology of design fires for individual train carriages is proposed based on the exponential design fire curve method and state-of-the-art fire research. The three key parameters required for construction of a design fire are the maximum heat release rate, time to maximum heat release rate, and energy content. An overview of the full scale train carriage fire tests is given and the results show that the maximum heat release rate is in a range of 7 MW to 77 MW and the time to reach the maximum heat release rate varies from 7 min to 118 min. The method could be employed to one single train carriage or several carriages, and alternatively one carriage could be divided into several individual sections. To illustrate the use of the methodology, several engineering applications are presented, including design fires for a metro train carriage with a maximum heat release rate of 77 MW, a double-deck railway train carriage with a maximum heat release rate of 60 MW and a tram carriage with a maximum heat release rate of 28 MW. The main objective is to provide practicing engineers with a flexible and reliable methodology to make design fires for individual train carriages in performance-based tunnel fire safety design.

  • 48.
    Fan, Chuan Gang
    et al.
    Hefei University of Technology, China.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Ingason, Haukur
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Lönnermark, Anders
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Fire Research.
    Effect of tunnel cross section on gas temperatures and heat fluxes in case of large heat release rate2016In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 93, p. 405-415Article in journal (Refereed)
    Abstract [en]

    Tests with liquid and solid fuels in model tunnels (1:20) were performed and analysed in order to study the effect of tunnel cross section (width and height) together with ventilation velocity on ceiling gas temperatures and heat fluxes. The model tunnel was 10m long with varying width (0.3m, 0.45m and 0.6m) and height (0.25m and 0.4m). Test results show that the maximum temperature under the ceiling is a weak function of heat release rate (HRR) and ventilation velocity for cases with HRR more than 100MW at full scale. It clearly varies with the tunnel height and is a weak function of the tunnel width. With a lower tunnel height, the ceiling is closer to the base of continuous flame zone and the temperatures become higher. Overall, the gas temperature beneath the ceiling decreases with the increasing tunnel dimensions, and increases with the increasing longitudinal ventilation velocity. The HRR is also an important factor that influences the decay rate of excess gas temperature, and a dimensionless HRR integrating HRR and other two key parameters, tunnel cross-sectional area and distance between fuel centre and tunnel ceiling, was introduced to account for the effect. An equation for the decay rate of excess gas temperature, considering both the tunnel dimensions and HRR, was developed. Moreover, a larger tunnel cross-sectional area will lead to a smaller heat flux.

  • 49.
    Ingason, Haukur
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Appel, Glenn
    Swedish Transport Administration, Sweden.
    Gehandler, Jonatan
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Li, Ying Zhen
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Nyman, Hans
    Brandskyddslaget AB, Sweden.
    Karlsson, Peter
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Arvidson, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Lundström, Ulf
    Swedish Transport Administration, Sweden.
    Modig, Henric
    Swedish Transport Administration, Sweden.
    Test Method and Performance of Fire Detection Systems in Tunnels2016In: Proceedings from the 7th International Symposium on Tunnel Safety and Security, 2016, p. 485-496Conference paper (Other academic)
    Abstract [en]

    The results of a study carried out for the Swedish Transport Administration on fire detection in road tunnels is presented. Laboratory tests and numerous large-scale tests were carried out in order to verify a proposal for a test method for fire detection systems. The main aim was to investigate possible fire detector systems and to see if they could fulfil the requirement given by the Swedish Transport Administration to detect the fire within 90 seconds. The tests are presented as well as a recommendation for testing detection systems in Swedish road tunnels. In order to perform the fire test, pans of different sizes were tested in order to obtain a reasonable fire size. The method proposed requires the use of three 0.6 m diameter standard pans, each containing eight litres of 95 octane gasoline, and air flow velocities of 2 m/s and 6 m/s. It was found out that using only one 0.6 m pan is sufficient if early warning is required without identifying the position for the fire-fighting system.

  • 50. Li, Ying Zhen
    et al.
    Fan, Chuan Gang
    Hefei University of Technology, China.
    Ingason, Haukur
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Brandteknik, skydd (BRs ).
    Lönnermark, Anders
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Brandteknik, skydd (BRs ).
    Ji, Jie
    University of Science and Technology of China, China.
    Effect of cross section and ventilation on heat release rates in tunnel fires2016In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 51, p. 414-423Article in journal (Refereed)
    Abstract [en]

    Model scale fire tests were performed in tunnels with varying tunnel widths and heights in order to study the effect of tunnel cross-section and ventilation velocity on the heat release rate (HRR) for both liquid pool fires and solid fuel fires. The results showed that for well ventilated heptane pool fires, the tunnel width nearly has no influence on the HRR whilst a lower tunnel height clearly increases the HRR. For well ventilated solid fuel fires, the HRR increases by approximately 25% relative to a free burn test but the HRR is not sensitive to either tunnel width, tunnel height or ventilation velocity. For solid fuel fires that were not well ventilated, the HRRs could be less than those in free burn laboratory tests. In the case of ventilation controlled fires the HRRs approximately lie at the same level as for cases with natural ventilation.

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