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  • 201.
    Vermina Lundström, Frida
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Sjöström, Johan
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Granström, Anders
    SLU Swedish University of Agricultural Sciences, Sweden.
    Garden structure is critical for building survival in northern forest fires – An analysis using large Swedish wildfires2023Ingår i: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 157, artikel-id 105928Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Despite increasing concern over wildfires in Fennoscandia, there are essentially no studies on the survivability of buildings within the wildland-urban interface of this region. We make use of four recent large-scale fires in Sweden to elucidate which factors are important for survival, using multiple logistic regression analysis of data collected at the sites. We obtained data on 187 buildings within the fire perimeters, nearly all with wood paneling and tile- or sheet metal roofing. 35 % of the buildings were lost or badly damaged. Results indicate that most buildings were approached by relatively low-intensity fire and that ignition primarily occurred through direct flame contact. The most important factor for survivability was the presence of a maintained lawn. The second most important was that no flammable material was present close to the building façade. Further, fire intensity often decreased close to buildings due to a larger portion of deciduous trees around gardens than in the surrounding forest. These factors were more important than specific features of the building itself, reflecting that the majority of buildings have combustible wooden façades. Our results suggest that the greatest potential for increasing building safety in the Swedish WUI is to keep the area immediately surrounding the building (∼5 m) free from tree litter and other flammable material. Also, since fire intensities are generally low, buildings can in most cases be defended with simple tools without compromising personal safety.

  • 202.
    Vylund, Lotta
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. Greater Gothenburg Fire and Rescue Service, Sweden.
    Frykmer, Tove
    Lund University, Sweden.
    McNamee, Margaret
    Lund University, Sweden.
    Eriksson, Kerstin
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Understanding Fire and Rescue Service Practices Through Problems and Problem-Solving Networks: An Analysis of a Critical Incident2024Ingår i: Fire technology, ISSN 0015-2684, E-ISSN 1572-8099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study explores how the Fire and Rescue Service can better prepare for solving complex problems in emergencies by using the concept of problems and problem-solving networks. Primary and secondary data from an extensive fire incident were analysed, including semi-structured interviews and incident assessment reports. Complex problems that arise during emergencies can be challenging to define, and solutions can be difficult to identify. However, this study demonstrates that breaking down complex problems into sub-problems can facilitate the identification of what kind of problem-solving network is needed to be able to solve problems in emergencies. Overall, this study contributes to a deeper understanding of the rationale behind problem-solving network in emergency situations and highlights the importance of relationships in problem-solving network to address complex problems during emergencies. 

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  • 203.
    White, Rolf Martin
    et al.
    Trøndelag brann- og redningstjeneste, Norway.
    Aamodt, Edvard
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    FRIC webinar: Falske alarmer, Er dagens situasjon akseptabel?2024Övrigt (Övrigt vetenskapligt)
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  • 204.
    Williams Portal, Natalie
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Flansbjer, Mathias
    RISE Research Institutes of Sweden, Material och produktion, Kemi och Tillämpad mekanik.
    Bäckstrand, Albin
    RISE Research Institutes of Sweden, Material och produktion, Kemi och Tillämpad mekanik.
    HCT-City - Bromätning i Varberg2023Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Projektet HCT City studerar hur HCT-konceptet (High Capacity Transport) kan appliceras i städer, genom piloter i Varberg och Stockholm samt analyser i Sundbyberg och Uppsala. I projektet testas hypotesen att HCT-konceptet kan förbättra både produktiviteten och transporteffektiviteten avsevärt och därmed minska utsläppen av CO2 och hälsovådliga emissioner, samtidigt som effekter avseende vägslitage och trafiksäkerhet minskas eller förblir oförändrade. Inom ramen för projektet har effekter adresserats vid utbyte av konventionella tunga fordon och kontroll mot HCT-fordon beträffande: trafiksäkerhet och påverkan/nedbrytning av gator, broar och vägar i tätorten. Denna rapport omfattar en fallstudie där kontrollerad fältmätning genomfördes på en utvald bro belägen på Österleden i Varberg. Mer specifikt utfördes deformationsmätning för att förstå konstruktionen verkningssätt beroende på bland annat fordonsvikt- och hastighet. De utförda mätningarna visar att brofarbanans nedböjning är generellt relativt liten och påkänningarna följaktligen är små vid passage av referensfordon och andra fordon under den aktuella mätperioden. Referensfordonets hastighet avspeglar sig i varaktigheten för brofarbanans nedböjning. Hastighet vid bropassagen verkar dock inte ha någon större inverkan på brofarbanans respons, vilket tyder på att den dynamiska effekten är liten för den aktuella bron.

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  • 205.
    Willstrand, Ola
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Gehandler, JonatanRISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.Andersson, PetraRISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Proceedings from the Seventh International Conference on Fires in Vehicles: STAVANGER, NORWAY, APRIL 24-25, 20232023Proceedings (redaktörskap) (Refereegranskat)
    Abstract [en]

    These proceedings include papers and extended abstracts from the 7th International Conference on Fires in Vehicles – FIVE 2023, held in Stavanger, Norway, April 24-25, 2023. The proceedings include an overview of research and regulatory actions coupled to state-of-the-art knowledge on fire related issues in vehicles, such as passenger cars, buses, trucks and trains, or related infrastructure, such as car parks or vehicle transport at sea. Fires in transport systems are a challenge for fire experts. New fuels that are efficient and environmentally friendly are rapidly being introduced, with emphasis on high energy density batteries. This rapid development, however, introduces new fire risks not considered previously and we risk getting a situation where we do not have enough knowledge to tackle them. In this context FIVE represents an important forum for discussion of the fire problem and for exchange of ideas. Fire protection in road, rail, air, and sea transport is based on international regulations since vehicles cross borders and the safety requirements must be the same between countries. Therefore, understanding of safety and regulations must be developed internationally and the FIVE-conference has a significant role to play as a place to exchange knowledge. FIVE attracts researchers, operators, manufacturers, regulators, rescue services and other key stakeholders. Of particular value is the mix of expertise and the international participation in the conference. The conference is unique as it includes fires in different types of vehicles. In recognition of the fact that many of the fire problems faced by these vehicles are the same, the solutions to them can also be similar. In the proceedings you will find papers on vehicle fire development, bus fires, alternative fuel and electric vehicles, and car park fires. We are grateful to the renowned researchers and engineers presenting their work and to the keynote speakers setting the scene. We sincerely thank the scientific committee for their expert work in selecting papers for the conference.

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  • 206.
    Willstrand, Ola
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. Uppsala University, Sweden.
    Pushp, Mohit
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Andersson, Petra
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Brandell, Daniel
    Uppsala University, Sweden.
    Impact of different Li-ion cell test conditions on thermal runaway characteristics and gas release measurements2023Ingår i: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 68, artikel-id 107785Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing use of lithium-ion batteries requires further efforts in safety testing and evaluation. It is of utmost importance that the effects of different test conditions are understood, particularly for validation of computer models. While plenty of data from thermal runaway tests are available in literature, few are from large test series. The missing systematic approach to evaluate the impact of different test conditions implies uncertainty when comparing test results. In addition, the fast pace in cell development, including an increasing utilization of larger cells, necessitate the validation of previously published results. This work presents thermal runaway data from 37 tests on one type of large format prismatic lithium-ion cell (157 Ah). The tests are conducted in a closed pressure vessel with inert atmosphere as well as in an open setup below an exhaust collector hood. Further, six different thermal runaway trigger methods are employed as well as four different states of charge. Emphasis is put on the gases produced, a key aspect for safety evaluation. The results are compared with literature data and a new modified method is proposed for calculating the characteristic venting rate in a closed pressure vessel. It is concluded that the trigger method affects the gas production rate, mass loss, and maximum temperature of the cell as much as its state of charge. The large cell format potentially impacts the specific total gas production and enhances the effects of different trigger methods, but has a small impact on other evaluation parameters. No significant differences were observed in the test results due to the different test setups, apart from differences due to potential combustion of the released gases in ambient atmosphere. 

  • 207.
    Willstrand, Ola
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. Uppsala University, Sweden.
    Pushp, Mohit
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Brandell, Daniel
    Uppsala University, Sweden.
    Uncertainties in the use of oxygen consumption calorimetry for heat release measurements in lithium-ion battery fires2024Ingår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 143, artikel-id 104078Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accurate measurement of the heat release from a battery fire is vital for risk management, product development and construction of accurate models. Oxygen consumption calorimetry is the most common method for heat release measurements in experimental fire tests. The strength of the method is that it can be applied to unknown compositions of fuel with sufficient accuracy. Despite that this method is used to estimate heat release from battery fires, the method is subject to discussion. In this work, the method is studied in-depth, and potential errors are structured and quantified. Uncertainties associated with self-generated oxygen and internal heat generation, total gas release from the battery and impact on the heat release calculations, as well as the assumed E-factor (i.e., heat release per unit mass of oxygen consumed), are thoroughly discussed. For a Li-ion battery fire, it is concluded that oxygen consumption calorimetry will exclude internal heat generation and underestimate the total heat released from the external flaming fire by up to 10 %. In addition, high rate of combustion reactions can result in that the measured peak heat release rate is underestimated much more, up to 100 %. 

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  • 208.
    Willstrand, Ola
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Ramachandra, Vasudev
    RISE Research Institutes of Sweden, Säkerhet och transport, Maritima avdelningen.
    Evegren, Franz
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Hägg, Mikael
    RISE Research Institutes of Sweden, Säkerhet och transport, Maritima avdelningen.
    Ramne, Bengt
    Chalmers University of Technology, Sweden.
    Li, Z
    Chalmers University of Technology, Sweden.
    Thies, Fabian
    Chalmers University of Technology, Sweden.
    Ringsberg, Jonas
    Chalmers University of Technology, Sweden.
    Lluis, Enric Julià
    Chalmers University of Technology, Sweden.
    Lätta elfartyg – Electric Light: Lightweight and electrically propelled Ro-Pax ships2022Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Syftet med detta projekt var att skapa ett innovativt fartygskoncept för ett helelektriskt Ro- Pax-fartyg, som använder sig av ny teknik, särskilt inom området elektrisk framdrivning och energilagring. Projektet inkluderade också en riskbedömning av konceptet och identifiering av möjliga uppföljningsstudier av kritiska designdelar. Kravet ökar på alla typer av sjöfart att minska utsläppen av växthusgaser och partiklar, samt även NOx och SOx. Att uppfylla IMO: s utsläppsmål 2050 kommer att kräva stora insatser avseende såväl energieffektivitetsåtgärder på befintliga fartyg som nya koncept för fossilfria fartyg. Elektrisk framdrivning för små fartyg har diskuterats länge och många installationer är idag i drift. Detta projekt är ett innovationsprojekt, med brett industriellt deltagande, som bidrar till det övergripande målet för hållbar sjöfart genom att föreslå ett fartygskoncept för ett eldrivet stort Ro-Pax-fartyg för kortare internationell resa. Mängden elektrisk energi som beräknas lagras i batterier ombord är cirka 60 MWh. Detta är tio gånger mer än den nuvarande största installationen av marina batterier. När det gäller brandsäkerhet är det mycket viktigt med ett holistiskt tillvägagångssätt, inklusive integritet, ventilation, feldetektering och brandbekämpningsmetoder etc. baserat på riskidentifiering. Konceptet med brandsäkerhet för batterier som utvecklats i detta projekt utgör riktlinjer för säkerhetskrav för stora fartygsbatteriinstallationer och är ett av huvudresultaten från det genomförda riskanalysarbetet. Tanken med det presenterade konceptet är att det ska vara tillämpligt för alla eldrivna fartyg och att det ska kunna användas som utgångspunkt för diskussioner om IMO-harmoniserade regler för batterilagringssystem ombord på fartyg. En viktig slutsats från projektet är att ett helelektriskt Ro-Pax-fartyg, som går på rutten Göteborg till Frederikshavn, är ett tekniskt och kommersiellt realistiskt alternativ.

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  • 209.
    Xie, L.
    et al.
    Norwegian University of Science and Technology, Norway.
    Ustolin, F.
    Norwegian University of Science and Technology, Norway.
    Lundteigen, M. A.
    Norwegian University of Science and Technology, Norway.
    Li, Tian
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Liu, Y.
    Norwegian University of Science and Technology, Norway.
    Performance analysis of safety barriers against cascading failures in a battery pack2022Ingår i: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 228, artikel-id 108804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lithium-ion batteries have been widely employed as the principal power source in electric vehicles and other storage systems. However, some critical issues in a battery pack still exist, such as thermal failures on initial cells that impact the temperatures of the surrounding cells. Such cascading failures may significantly affect battery performance and safety. Thermal barriers, as one kind of safety barrier, are therefore installed to prevent failure propagations. This paper focuses on the situation when the temperature of battery cell increases, but the battery pack still can be used in a degradation mode since the barriers are against cascading failures. An approach is proposed to analyze how the deployment and performance of thermal barriers in a battery pack determine their capabilities against cascading failures. The approach includes thermal propagation models associated with the simulations, degradation models, reliability analysis, and barrier analysis. Its application is illustrated with a practical case study. The battery reliabilities are sensitive to many factors of the barriers, such as temperature differences, failed cells, and performance coefficient. The barriers between parallel cells are found to be more effective in mitigating failure propagation. Such findings can be beneficial for barrier optimization and reliability improvement of battery packs. © 2022 The Authors

  • 210.
    Yang, A.
    et al.
    SINTEF, Norway.
    Aamodt, A.
    SINTEF, Norway.
    Samuelsen, P. H.
    Oslobygg KF, Norway.
    Olsø, B. G.
    SINTEF, Norway.
    Haukø, A. -M
    SINTEF, Norway.
    Meraner, Christoph
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Fire safety of ventilation systems and fire incidence reports in Norwegian schools2022Ingår i: ROOMVENT 2022, EDP Sciences , 2022Konferensbidrag (Refereegranskat)
    Abstract [en]

    School fires are causes of concern in many countries. Although most of these fires are minor in terms of heat release rate, the amount of smoke produced can be substantial and cause significant damage beyond the room of origin. Currently, Norwegian schools have a wide spread of different ventilation strategies and systems, and building owners struggle with how to test, maintain and keep them fire safe. A systematic survey of fire incidences and ventilation strategies in schools for three municipalities in Norway was done to gain better insights into fire safety in schools. The results indicated that the place of origin is often in locker rooms/toilets, kitchen, or outdoors, and the fires were usually deliberately set. For non-arson fires, electrical failure was the most common cause. The majority of the fire incidences were small but would often result in smoke damage and spread of soot in the building, leading to high restoration costs for the local municipality. A lack of documentation of the fire safety and the function of the ventilation system was also identified, indicating a need for improved routines and systems for registering fire incidences and documentation of the technical systems. © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/)

  • 211.
    Yang, Miao
    et al.
    Lund University, Sweden.
    Zhang, Jingyuan
    NTNU Norwegian University of Science and Technology, Sweden.
    Zhong, Shenghui
    Lund University, Sweden; Tianjin University, China.
    Li, Tian
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. NTNU Norwegian University of Science and Technology, Sweden.
    Løvås, Terese
    RISE Research Institutes of Sweden.
    Fatehi, Hesammedin
    Lund University, Sweden.
    Bai, Xue-Song
    Lund University, Sweden.
    CFD modeling of biomass combustion and gasification in fluidized bed reactors using a distribution kernel method2022Ingår i: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 236, artikel-id 111744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-dimensional reactive multi-phase particle-in-cell (MP-PIC) model is employed to investigate biomass combustion and gasification in fluidized bed furnaces. The MP-PIC model considered here is based on a coarse grain method (CGM) which clusters fuel and sand particles into parcels. CGM is computationally efficient, however, it can cause numerical instability if the clustered parcels are passing through small computational cells, resulting in over-loading of solid particles in the cells. To overcome this problem, in this study, a distribution kernel method (DKM) is proposed and implemented in an open-source CFD code, OpenFOAM. In DKM, a redistribution procedure is employed to spread the solid volume and source terms of the particles in the parcel to the domain in which the particles are clustered. The numerical stiffness problem caused by the CGM clustering can be remedied by this method. Validation of the model was performed using data from different lab-scale reactors. The model was shown to be able to capture the transient heat transfer process in a lab-scale bubbling fluidized bed reactor under varying fluidization velocities and loads of sand. Then, the model was used to study the combustion/gasification process in a bubbling fluidized bed reactor under varying ambient temperatures, equivalent air ratios, and steam-to-biomass ratios. The performance of DKM was shown to improve the accuracy and the robustness of the model. © 2021 The Author(s)

  • 212.
    Yao, Y.
    et al.
    China University of Mining and Technology, China.
    Wang, J.
    China University of Mining and Technology, China.
    Jiang, Lei
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Wu, B.
    China University of Mining and Technology, China.
    Qu, B.
    China University of Mining and Technology, China.
    Numerical study on fire behavior and temperature distribution in a blind roadway with different sealing situations2023Ingår i: Environmental Science and Pollution Research, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 30, s. 36967-36978Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blind roadways have only one portal which connects with other types of mine roadways. Sealing the fire area in a blind roadway is an effective method of disaster relief in a mine. To understand the effect of sealing ratio and sealing distance on fire behavior, Fire Dynamics Simulator (FDS 6.6) was used to study blind roadway fires with different fire scenarios. Results indicate that the smoke flow velocity increases significantly with the increase of sealing distance. The fire in the blind roadway is ventilation-controlled. When the sealing ratio reaches 80%, the fire self-extinguishes completely. Otherwise, the fire experiences an extinguishing-reburning cycle periodically. Besides, an empirical model is proposed to predict the downstream temperature distribution beneath the ceiling in the region from fire source to sealing position. The predictions by the proposed model comply well with the simulation and experimental results from our and others’ studies. This study provides new insights into the sealing strategies in blind roadway fires, and the outcomes of the current study are of guiding significance for the fire rescue in the blind roadways or similar structures. © 2022, The Author(s)

  • 213.
    Zeinali, Davood
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Sarp Arsava, Kemal
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Sanfeliu Meliá, Cristina
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Recent developments in vehicle-to-grid (V2G) and smart ventilation technologies2022Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The present document is the result of a study led by the Fire Research and Innovation Centre (FRIC), aiming to help enhance the fire safety of new technologies in buildings. Accordingly, the study firstly evaluates the technology of Vehicle-to-Grid (V2G) to identify its related fire risks for buildings and to propose fire safety measures that allow mitigating the identified risks. V2G is an alternative technology for enhanced energy storage and the use of renewable energy in buildings. This technology uses the batteries of Electric Vehicles (EVs) to store energy and then returns an optimal amount of the stored energy to the power grid when needed. The present document evaluates the fire hazards of EV batteries integrated with V2G technology and provides an overview of the existing regulations as well as developing standards in this area. Secondly, the study evaluates the technology of smart ventilation systems, i.e., systems that employ sensors to improve indoor ventilation quality and its efficiency in terms of energy consumption. The present document evaluates the influence of such systems on fire safety in buildings, especially from the perspective of their interaction with fire suppression systems.

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  • 214.
    Zhang, Jingyuan
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Li, Tian
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. NTNU Norwegian University of Science and Technology, Norway.
    Ström, Henrik
    Chalmers University of Technology, Sweden.
    Wang, Boyao
    NTNU Norwegian University of Science and Technology, Norway.
    Løvås, Terese
    NTNU Norwegian University of Science and Technology, Norway.
    A novel coupling method for unresolved CFD-DEM modeling2023Ingår i: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 203, artikel-id 123817Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In CFD-DEM (computational fluid dynamics-discrete element method) simulations particles are considered Lagrangian point particles. The details of the flow near the particle surface are therefore not fully resolved. When the particle scale is larger than the resolved flow scale, the coupling between the CFD model and the DEM model is critical. An effective coupling scheme should minimize the risk of artificial influences on the results from choices of numerical parameters in implementations and consider efficiency and robustness. In this work, a novel coupling method is developed. The method includes both the smoothing of the particle data and the sampling of the gas phase quantities. The smoothing employs the diffusion-based method. The gas sampling method can reconstruct the filtered fluid quantities at the particle center. The sampling method is developed based on the diffusion-based method with higher efficiency. The new method avoids mesh searching and it can be easily implemented in parallel computing. The developed method is validated by the simulation of a forced convection experiment for a fixed bed with steel spheres. With the well-posed grid-independent coupling scheme, the simulation results are in good agreement with the experimental measurements. The coupling effects and the computational cost are discussed in detail. 

  • 215.
    Zhang, Yue
    et al.
    China University of Mining and Technology, China.
    Yao, Yongzheng
    China University of Mining and Technology, China.
    Ren, Fei
    China Academy of Safety Science and Technology, China.
    Zhu, Hongqing
    China University of Mining and Technology, China.
    Zhang, Shaogang
    Shanghai Maritime University, China.
    Jiang, Lei
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Effects of ambient pressure on smoke propagation in inclined tunnel fires under natural ventilation2023Ingår i: Environmental Science and Pollution Research, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 30, s. 65074-65085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper systematically studied the coupling effect of ambient pressure and tunnel slope on temperature distribution and smoke propagation in full-scale tunnel fires under natural ventilation by FDS. The downstream length (longitudinal length from fire source center to tunnel downstream exit) was also considered. The concept of “height difference of stack effect” was put forward when analyzing the mutual effect of tunnel slope and downstream length on smoke movement. The results show that the maximum smoke temperature beneath the ceiling decreases with the increasing ambient pressure or tunnel slope. The longitudinal smoke temperature decays faster with the decreasing ambient pressure or slope in inclined tunnel. The induced inlet airflow velocity increases with the increasing height difference of stack effect, while decreases with the increasing ambient pressure. And the smoke backlayering length decreases with the increasing height difference of stack effect. Taking heat release rate (HRR), ambient pressure, tunnel slope and downstream length into account, the prediction models of dimensionless induced inlet airflow velocity and smoke backlayering length in inclined tunnel fires at high altitude were developed, which agree well with our and others’ results. The outcomes of current study are great meaningful to fire detection and smoke control in inclined tunnel fires at high altitude. © 2023, The Author(s)

  • 216.
    Zhao, Shengzhong
    et al.
    Shandong Jianzhu University, China.
    Yang, Haoran
    Shandong Jianzhu University, China.
    Li, Ying Zhen
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Ingason, Haukur
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Liu, Fang
    Chongqing University, China.
    Theoretical and numerical study on smoke descent during tunnel fires under natural ventilation condition2023Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 142, artikel-id 105414Artikel i tidskrift (Refereegranskat)
    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.

  • 217.
    Zhao, Z.
    et al.
    Wuhan University, China.
    Qin, H.
    Hubei University of Economics, China.
    Li, Tian
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. NTNU, Norway.
    Hua, B.
    Wuhan University, China.
    Hou, Y.
    Wuhan University, China.
    Chen, T.
    Wuhan University, China.
    Ström, H.
    NTNU, Norway; Chalmers University of Technology, Sweden.
    CFD simulation of soot generation during biomass gasification in a cyclone gasifier2024Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 364, artikel-id 131103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soot generation is a challenging issue in high-temperature biomass gasification, which reduces the biomass conversion rate and leads to contamination of the reactor. To provide new means and insights to optimize gasification processes, the soot generation during biomass gasification in a cyclone reactor is studied here by establishing a novel biomass gasification and soot formation model to improve the accuracy attainable in numerical predictions of spatio-temporal soot evolution. The new method is validated by comparing it with gasification experiments in two reactor configurations. A good performance in capturing the overall soot generation and light gas yield of the current model is obtained in the simulations of an entrained flow reactor compared with experimental data. Besides, the biomass gasification behavior in this entrained flow reactor is systematically studied by reviewing the tar, precursor, and soot mass fraction evolution in the reactor under different steam/carbon ratios, gasification temperatures, and air excess ratios with the new model. Furthermore, the influence of varying air equivalence ratios, the operation temperature and the fuel moisture on the soot generation in a cyclone gasifier, as well as the ability of the proposed model to reflect such influences, are also discussed. Numerical simulations demonstrate the existence of an optimal operation condition for the cyclone gasifier in terms of the soot generation. The current work thus provides a useful tool for analyzing the mechanism of soot formation at the reactor scale. 

  • 218.
    Zhu, G.
    et al.
    Xi’an Jiaotong University, China.
    Xu, L.
    Xi’an Jiaotong University, China.
    Wang, S.
    Xi’an Boiler & Environmental Protection Engineering Co Ltd, China; Xi’an Jiaotong University, China.
    Niu, F.
    China Coal Research Institute Company of Energy Conservation, China.
    Li, Tian
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet. NTNU, Norway.
    Hui, S.
    Xi’an Jiaotong University, China.
    Niu, Y.
    Xi’an Jiaotong University, China.
    Synergistic reduction on PM and NO source emissions during preheating-combustion of pulverized coal2024Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 361, artikel-id 130699Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present research focuses on the synergistic source control of particulate matter (PM) and NOx formation from pulverized coal combustion. Comparative experiments of preheating-combustion and conventional combustion were conducted in a lab-scale high-temperature preheating-combustion furnace, and PM10 and NO were measured by an electrical low pressure impactor and a flue gas analyzer, respectively. The results of the experiment indicate that preheating-combustion has a significant reduction in PM10 (especially PM0.3 up to 37.51 %) and NO, which can achieve the synergistic control of PM10 and NO source emissions during the combustion process. The fragmentation in preheating-combustion was weaker compared to the conventional combustion. Meanwhile, the relatively weak preheating-combustion coal char oxidation reaction leads to a decrease in ultrafine mode PM yielded due to the inhibition on vaporization of mineral inclusions. The PM0.3/PM1 mass ratio of the preheating-combustion has a decreasing trend, implying an elevated yield of PM0.3-1 and a shift of the average PM1 particle size toward a larger particle size. Higher preheating temperature (Tp) presented the potential to further reduce NO formation, and the NO reduction efficiency increased from 46.59 % to 56.60 % when the Tp was increased from 1200 K to 1600 K. All our preliminary results throw light on the nature of synergistic source control of preheating-combustion PM and NO formation. 

  • 219.
    McNamee, Robert (Redaktör)
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Anderson, Johan (Redaktör)
    RISE Research Institutes of Sweden, Säkerhet och transport, Brand och Säkerhet.
    Proceedings of FSF 2024. The 4th International Symposium on Fire Safety of Facades 2024: 10-12 June 2024. Lund, Sweden2024Rapport (Refereegranskat)
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