In this paper a coarse graining process is used to subsequently model large wildland fires, starting from a model of a single tree. The models are created using Wildland Urban Interface Fire dynamics Simulator (WFDS), and it is here found that reasonable fire spread in small forests can be obtained although the results are quite dependent on grid resolution as well as moisture content. In most realistic scenarios the computational volume is rather large yielding massive amounts of data. In using WFDS a rather small grid size is needed to appropriately model the fire spread this will be a severely limiting factor in creating large models.

The self-heating process in a laboratory scale experiment has been modelled using the Comsol Multiphysics software. In the simulations the gas flow and air movement in the volume and heat diffusion in the bulk were taken into account however only one reaction in the pellets bulk is considered. The input data is found from measurements of the reaction chemistry and the heat transfer properties. It is found that all relevant physics is needed in order to obtain reasonable predictions in particular the heat transfer between the bulk and the gas is important but also condensation and evaporation of moisture.   

Self-heating during storage of biomass in piles causes material losses, leads to emissions to air, and poses a risk of fire. There are different techniques to assess a biomass material's propensity for self-heating, some of these are briefly reviewed. One of these techniques is isothermal calorimetry, which measures thermal power from materials and produces time-resolved curves. A recently developed and published test standard, ISO 20049-1:2020, describes how the self-heating of pelletized biofuels can be determined by means of isothermal calorimetry and how thermal power and the total heat produced during the test should be measured by isothermal calorimetry. This paper supports interpretation of the result obtained by isothermal calorimetry; the mentioned standard provides examples of peak thermal power and total heat but does not provide any assistance on how the result from isothermal measurements should be interpreted or how the result from measurements on different samples could be compared. This paper addresses the impact of different types of reactions, peak thermal power, total heat released (heat of reaction), activation energy, heat conductivity, and pile size on the temperature development in a generic pile of biomass. This paper addresses important parameters when the result from isothermal calorimetry is evaluated. The most important parameter, with respect to temperature development in large piles, was found to be the total heat released. It was also proposed that safe storage times, that is, the time until a run-away of the temperature in the pile, could be ranked based on the time to the peak thermal power.

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.

Fires in waste facilities represent significant potential social, economic and environmental challenges. Although the awareness of fires in waste facilities and their consequences has increased in recent years, significant fire safety challenges remain. Fires in waste facilities in Norway and Sweden have been studied to make an overall fire safety assessment and propose measures for increased fire safety. Common ignition causes include self-heating, thermal runaway in batteries, friction, human activity, technical or electrical error and unfavourable combined storage. High-risk wastes include general, residual waste, batteries, electrical and electronics waste, and paper and cardboard. Frequent fires in outdoor storage, increasing indoor storage and new types of waste appear to result in an increased reluctance by insurance companies to work with waste facilities. Measures are suggested for fire safe facility design, operations, waste handling and storage, as well as actions to limit the consequences for the environment and the facility during and after a fire. These actions may prevent fires and minimise the impact of fires that do occur. Increased fire safety at waste facilities may foster a better dialogue between the industry and insurance providers by reducing the potential economic impacts, and limit potential social costs and environmental impacts. © 2020 The Authors

This paper contains a proposal of new Swedish framework for performance-based design of road tunnel fire safety derived from Swedish and European regulation. The overall purpose of the guideline is to protect life, health, property, environment, and key societal functions from fire. The guideline is structured into five key groups of requirements: #1 Proper management and organisation, #2 to limit the generation and spread of fire and smoke, #3 to provide means for safe self-evacuation, #4 to provide means and safety for the rescue service, and #5 to ensure load-bearing capacity of the construction. Each group contains a hybrid of prescriptive requirements, performance-based requirements, and acceptable solutions. Prescriptive requirements must be fulfilled, however, it is the choice of the design team to either adopt the proposed acceptable solutions, or to design alternative solutions by verifying that performance-based requirements are satisfied. For verification of performance-based requirements through risk analysis the operational, epistemic, and aleatory uncertainties are considerable. Therefore, a scenario-based risk analysis with several specified input variables and methods is recommended for verification of #3 and #5. Indispensable complements are scenario exercises, emergency exercises and similar methods that validate the design and highlight organisational aspects. The proposed design guide has been developed by the authors together with the advisory group established for the work.

Fuels with a high energy density have contributed to the development of modern communities. On the other hand, fuels contain energy that, during some conditions, can result in incidents, not least within transportation. CNG vehicles are designed according to safety standards of UNECE, including events such as fire. In case of a fire a thermally activated Pressure Relief Device (TPRD) should empty the container before a pressure vessel explosion potentially can occur. CNG tanks are according to UNECE regulation 110 tested against a 1.65 m long pan fire. However, local fires are not included in these tests. This report presents fire tests of CNG containers performed both with a UNECE compatible fire source and with a local fire source. Any pressure vessel explosion and jet flames were characterized for two different types of CNG containers, namely steel and composite. In five out of six tests the safety of the CNG containers prevailed also in the event of a local (0.24 m by 0.24 m) pan fire, meaning that no pressure vessel explosion occurred. In real vehicle fires, where the fire extends from its local characteristics to a more developed fire that expose the CNG containers to a larger extent, these tests support that TPRDs most likely will activate. The experience from running these test series call for that the fire source should be more accurately defined with regards to fuel and dimensions and a local fire should be included in the UNECE Regulation 110.

Vehicles that are powered by gaseous fuel, e.g., compressed natural gas (CNG) or hydrogen (H2), may, in the event of fire, result in a jet flame from a thermally activated pressure relief device (TPRD), or a pressure vessel explosion. There have been a few incidents for CNG vehicles where the TPRD was unsuccessful to prevent a pressure vessel explosion in the event of fire, both nationally in Sweden and internationally. If the pressure vessel explosion would occur inside an enclosure such as a road tunnel, the resulting consequences are even more problematic. In 2019 the authors investigated the fire safety of CNG cylinders exposed to localized fires. One purpose of the tests conducted in 2021 reported in this paper is to investigate whether extinguishment with water, e.g., from a tunnel deluge system, may compromise the safety of vehicle gas cylinders in the event of fire. Steel cylinders handles the situation with localizde fire and/or cooling with water well. Composite tanks can rupture if the fire exposure degrades the composite material strength, and the TPRD is not sufficiently heated to activate, e.g., if the fire is localized or if the TPRD is being cooled by water, which prevents its activation.

There can be situations, for example if gas containers have been damaged in a vehicle crash, when the fire and rescue service would like to depressurize the gas containers through shooting with a civilian rifle. Modern high-pressure hydrogen containers are designed for a working pressure of 700 bars. This means that they have a very thick and strong shell made of composite material. At the same time the fire and rescue service only have access to civilian rifles and ammunition that can be bought for hunting purposes. Thus, tactical and safe depressurization of hydrogen containers is a big challenge. RISE have, together with the Södra Älvsborgs Fire and Rescue Services (SÄRF), Swedish Civil Contingency Agency, and Lund University conducted shooting tests of gas tanks mounted on a hydrogen gas vehicle and three stand-alone hydrogen gas tanks. The shooting tests were conducted at Remmene shooting field in Sweden. Thirteen shooting tests with hydrogen tanks placed in favouarable positions were performed. Out of these, only four tests were succesful in puncturing the individual gas tank in a single shot. Furthermore, two unwanted events occurred; one rupture (after 7 shots) and two powerful jets (after 20 and one shot respectively). This shows that further development and research is required in order to develop a method to safely depressurize high pressure hydrogen tanks.

The project BREND investigated risk with alternative fuel vehicles inside ro-ro spaces. BREND 2.0 is a continuation and has in particular investigated two of the major risks identified in BREND, namely the risk of toxic gases from electric vehicle fires and the risk of a pressure vessel explosion for fire exposed biogas or hydrogen vehicle tanks. Simulations of electric vehicle fires inside a ro-ro space based on real input fire data has been performed. Field experiments that investigate the conditions that can lead to pressure vessel explosion were made with fire exposed biogas and hydrogen tanks. Recommendations are given about how ro-ro space fires in alternative fuel vehicles, or indeed any vehicle fire, can be managed.

This qualitative risk analysis of dangerous goods transports with alternative propellants was ordered by the Swedish Civil Contingencies Agency (MSB). Scenario combinations consisted of five alternative fuels, six accident scenarios and five types of dangerous goods cargo. The alternative fuels were: methane, hydrogen, ethanol, methanol and dimethyl ether. The accident scenarios consisted of refuelling, fire in tire or engine, tunnel accident, road collision and sabotage of fuel tank. The dangerous goods were limited to: ammonium nitrate, petrol/diesel, methane, ethyl chloride, and EX/II cargo as defined in the ADR regulation. The main identified risks are due to the risk of pressure vessel explosion of gaseous fuels as it: 1) Threatens to detonate explosive load or ammonium nitrate. 2) Cause rescue service to take a defensive approach which will lead to larger consequences. Since there are sustainable liquid fuel alternatives such as bio diesel, this may be a better choice for dangerous goods transportation.

Use of CFD (computional fluid dynamics) software packages within fire performance based engineering and risk assessment is increasing substantially. An important part in the process is the quality assurance. For this reason the Swedish Rescue Services Agency (SRV) sponsored a unique research project. Within the project different codes for smoke spread and evacuation have been evaluated. This poster will focus on the evaluation of four CFD software codes.

Dust explosion has been a constant threat to the physical working environment of the Swedish process industries which deal with combustible powders. Examples of such industries are pellets, paper, metal processing, food and feed, pharmaceuticals, and additive industries. This project aims at (i) development of physics-based and well-validated models which address the important combustion phenomena in dust explosions, (ii) development of a well-verified and an efficient numerical tool based on an open-source toolbox OpenFOAM for predicting consequences of dust explosions and (iii) simulation of large-scale dust explosions in the process industries. The project result improves the understanding of dust explosions, and it provides the process industries with a numerical tool for designing safer process plant regarding dust explosions.The model and code development were carried out in a step-by-step fashion. First, the so-called Flame Speed Closure (FSC) model for premixed turbulent combustion, was implemented into OpenFOAM. The implementation was verified against analytical solutions for 1-dimensional planar and 3-dimensional spherical turbulent flames. Second, the developed code including the model, i.e., FSCDustFoam, was validated against experimental data on corn starch dust explosion in a fan-stirred explosion vessel under well-controlled laboratory conditions. Third, the FSC model was extended by adapting the well-known experimental observations of the self-similarity of the flame acceleration to address large-scale industrial dust explosions. An excellent agreement between measurements of vented corn starch dust explosions in an 11.5 m3 vessel and the simulations using the extended the FSC model was obtained.In spite of the successful development of FSCDustFoam, challenges remain. Specifically, the current version of FSCDustFoam cannot address the effect of different shapes of vent openings on dust explosions. Nevertheless, FSCDustFoam is a promising tool to be applied and further developed to resolve the challenging reality regarding dust explosions in the Swedish process industries.

The design of explosion mitigation strategies e.g. vent design is mainly based on dust explosioncharacteristics such as the maximum explosion pressure XÇïÓ and the deflagration index n! of dustcloud, which are defined in various standards.The wood dust explosion characteristics can be directly obtained by performing standard tests, and testresults are also available in the literature. However, the parameters for one type of dust may varysubstantially in the literature. For example, the n! value for one wood dust is 11.4 times higher thananother wood dust in Gestis-Dust-Ex database. The reason for such large variation in explosionparameters is due to factors such as material properties, particle size distribution, particle shape, moisturecontent, turbulence level during tests and so on.The objectives of this paper are (i) to carry out dust explosion tests for XÇïÓ and n! for two wood dustswith well-described material parameters such as particle size distribution and moisture content accordingto European standards, (ii) to perform statistical analysis of wood dust explosion characteristics includingXÇïÓ and n! in the literature, (iii) to identify the effects of dust material parameters such as particle sizeand moisture contents on XÇïÓ and n! and (iv) to highlight the variation in XÇïÓ and n! and theimportance of obtaining knowledge about these properties of an individual dust, e.g. via dust explosiontests.

Dust explosion is a constant threat to the Swedish industries which deal with combustible powders such as pellets producers, food industry, metal industry and so on. This project aims at (i) development of high-fidelity and well-validated models which address important combustion phenomena during a dust explosion, (ii) development of an efficient numerical tool based on an open source toolbox for predicting consequences of dust explosions and (iii) simulation of dust explosions in scenarios of process industries in cooperation with the reference group members of this project. The project result will improve the understanding of complicated combustion phenomena associated with dust explosions, and it will help the process industries in designing better vent system in case of dust explosion. During the first year, the Flame Speed Closure (FSC) model for premixed turbulent combustion, has been implemented in the open source platform OpenFOAM, which was installed at RISE in the beginning of the project. The implementation of FSC model has been verified against analytical solutions for 1-D planar and 3-D spherical turbulent flames. Verification shows correct implementation of model in the OpenFOAM platform. Currently, the developed code is being validated against small-scale dust-explosion experiments performed using the well-known Leeds combustion vessel. The first test of the code show that the trend, i.e. an increase in turbulent velocity fluctuation, an increase in flame speed, is predicted by the code. A further test shows that the code and model can predict the flame speed quantitatively using proper model parameters. In the next step, the model and code will be developed for considering the heat losses and radiation. Later the developed numerical platform will be applied to unsteady 3-D RANS simulations of large-scale experiments performed at REMBE® Research and Technology Center for vent relieving with different vent geometry.

Dust explosion is a constant threat to the Swedish industries which deal with combustible powders such as pellets producers, food industry, metal industry and so on. This project aims at (i) development of high-fidelity and well-validated models which address important combustion phenomena during a dust explosion, (ii) development of an efficient numerical tool based on an open source toolbox for predicting consequences of dust explosions and (iii) simulation of dust explosions in scenarios of process industries in cooperation with the reference group members of this project. The project result will improve the understanding of dust explosions, help the process industries in designing better vent system in case of dust explosion, and create a safer working environment. During the end of the first and the beginning of the second year, the developed numerical platform including the dust explosion model was validated against experimental data on corn starch dust explosion in a fan-stirred explosion vessel, obtained by Bradley et al. (1989), under well-controlled laboratory conditions. After that, a collaboration was established between the project members and Rembe Research and Technology Center in order to apply the developed numerical platform for simulating large-scale industrial vented dust explosions. In parallel with the collaboration with Rembe, a collaboration with Gexcon was established in order to perform a joint study of dust explosion modelling using the developed numerical platform and the commercial code FLACS-DustEx.

Combustion behaviour of municipal solid waste bales is a rarely studied topic hitherto. However, there is dire need to devote research on the topic because baling as a storage methodology is getting popular among waste management companies and fire episodes in such storage sites can have devastating economic, environmental and social implications. In this study, thickness of low density polyethylene (LDPE) plastic sheets (12 layers, 6 layers and no layer) and type of ignition source (pilot ignition, thermal radiation) were investigated to see their effect on combustion behaviour of bales. In total eleven tests with a single bale in each test were performed. It has been found that the bales not wrapped with LDPE plastic sheets may pose higher hazards for adjacently stored material to catch fire as the value of maximum heat release rate observed for them was higher than those wrapped with LDPE plastic sheets. Furthermore, it has been found that LDPE plastic wrapping do not contribute significantly to the combustion of bales when exposed only to thermal radiation from an adjacent fire. However, it plays a significant role in ignition of bales in case exposed to a pilot flame ignition source. Molten LDPE plastic trapped between the adjacently stored bales was found to be another important factor influencing the combustion of bales.

In this study, NASA’s VIIRS (Visible Infrared Imaging Radiometer Suite) fire hotspots and data of the Swedish Civil Contingencies Agency (MSB), collected between 2012 and 2018, was integrated to characterize waste fire incidents that were detected by VIIRS and reported to MSB (DaR), detected by VIIRS but not reported to MSB (DbNR) and that are reported to MSB but not detected by VIIRS (RbND). Results show that the average number of open waste fire incidents per million capita per year (AFIPMC) in Sweden, for the period 2012–2018, ranges from 2.4 to 4.7. Although a weak correlation exists (r = 0.44, P = 0.1563, one tailed) between years and number of fire incidents (MSB + VIIRS fires), a continuous increase in number of fire incidents was recorded between 2014 and 2018. It is concluded that the use of satellite data of fire anomalies, in-combination with the use of incident reports, will help in formalizing more reliable and comprehensive waste fire statistics. Another focus area of the article is to consolidate the recommendations and routines for safe storage of waste and biofuels and to present the lessons that can be learnt from past fire incidents. The article also discusses the technical, political, economic, social, and practical aspects of waste fires and provide a baseline for future research and experimentation.

Computational fluid dynamics (CFD) modelling has been widely used for performance-based tunnel fire safety design in engineering applications. A CFD tool divides a computation domain into a large number of small cells and solves a set of differential equations with sub-models using different solution algorithms. The CFD users need to not only efficiently use CFD tools but also understand the embedded mechanisms. The basics of CFD modelling are introduced including controlling equations, different turbulence models and numerical methods. Sub-models important for tunnel fires are then described, i.e. gas phase combustion models, condensed phase pyrolysis models, fire suppression models, wall functions and heat transfer models. Despite the rapid development and completeness of these models related to fire phenomena, many limitations exist which should be always kept in mind by the users. Recommendations for CFD modelling of tunnel fires are presented.

Five large-scale fire tests, including one pool fire test and four HGV mock-up fire tests, were carried out in the Runehamar tunnel in Norway in year 2003. New data and new analyzes are presented in this paper, together with a short summary of previous work on these tests. Heat release rate (HRR), radiation, fire spread, gas production, backside wall temperature, visibility, backlayering, fire growth rate, gas temperature, flame length, ventilation and pulsation are investigated. Simple theoretical models are developed to estimate and predict these parameters. The correlations developed can be used by engineers working on fire safety in tunnels.