This study presents a coupled model incorporating a thermal propagation model and a fire model to investigate the fire safety of a large lithium-ion battery (Li-ion) module. The thermal propagation model employs a three-dimensional (3D) finite element method (FEM), while the fire model utilizes computational fluid dynamics (CFD). Literature data on material properties and thermal runaway characteristics of 18650 cells with Nickel-Manganese-Cobalt (NMC) chemistry, including the onset temperature of rapid thermal runaway (TR), maximum cell temperature, vent gas composition, and volume, are used as input data. Simulation results highlight that thermal convection serves as the dominant heat transfer mechanism, contributing over 50 % of the total heat flux driving TR propagation. TR propagation initiates gradually but accelerates rapidly in a string-wise pattern. The gas temperature inside the module significantly influences TR process through convective heat transfer. The computed heat release exhibits linear correlation with experimental values, but underpredicts total heat release by approximately a factor of three. This discrepancy is likely due to the omission of combustion of solid particles as well as heat release from ancillary components (e.g., cables, insulation in the module). The calculated total heat release correlates linearly with the cumulative number of cells entering TR, confirming that accurate TR propagation modelling is critical for reliable prediction of overall energy release

Combustible dust hazards remain a persistent threat across various industries, as dust is an inevitable byproduct of many processes. Managing combustible dust hazards at the battery recycling plants is one of the key factors to minimize the incidents and down time and, therefore, to improve the work environment, and to increase the profitability of the business. The present work aims at exploring the dust explosion risks of black mass in battery recycling. Four black mass samples are investigated. Microscope images, particle size distribution, water content and organic carbonates are analyzed. Dust explosion experiments are performed in a 20-L vessel. Results show that a 10 kJ ignition energy cannot generate high explosion overpressure, whereas an ignition energy of 20 kJ yields an explosion overpressure above 6 bar. The experimental results are compared with published data on various explosion-related characteristics of other dusts in battery recycling, in particular, aluminum and graphite dusts.

A multi-physics thermal propagation model of a battery module, consisting of 507 cylindrical 18650 cells, was built using a commercial software. The model incorporated an empirical method for self-heating in battery cells, a 3-Dimentional (3-D) Finite Element method (FEM) for simulating thermal propagation in solid materials, and sub-models for thermal convection and radiation. Simulations reveal the significance of thermal convection in thermal propagation. The model agreed well with the experimental data until around half of the cells entered thermal runaway (around 22 minutes), with an observed overprediction of heat release afterward. This overprediction might be attributed to inaccuracies in thermal convection and the omission of burning vented gases and solid particles.

The number of batteries in various applications at end-of-life and production waste from battery gigafactories increase significantly. At the same time, new EU regulations are introduced to promote battery recycling, which is a new and rapidly growing business. Large amounts of combustible dust are generated in battery recycling. Managing combustible dust hazards at the battery recycling plants is one of the key factors to minimize the incidents and down time and, therefore, to improve the work environment, and to increase the profitability of the business. Accordingly, the present work aims at exploring the risk of explosion of black mass dusts associated with battery recycling. Specifically, four black mass samples from different battery recycling plants are experimentally investigated. Microscope images, particle size distribution, water content and organic carbonates are analyzed. Dust explosion experiments are performed in a 20-L vessel. Parameters including dust concentration, ignition energy, ignition delay, dust injection pressure are varied. Results show that a 10 kJ ignition energy cannot generate high explosion overpressure, whereas an ignition energy of 20 kJ yields an explosion overpressure above 6 bar for black mass sample C at a concentration of 300 g/m3. The obtained experimental results are compared with published data on various explosion-related characteristics of other dusts relevant to battery recycling, in particular, aluminum and graphite dusts.

Thermal runaway is a major concern for lithium-ion batteries in electric vehicles. A manufacturing fault or unusual operating conditions may lead to this event. Starting from a single battery cell, more cells may be triggered into thermal runaway, and the battery pack may be destroyed. To prevent this from happening, safety solutions need to be evaluated. Physical testing is an effective, yet costly, method to assessing battery safety performance. As such, the potential of a numerical tool, which can cut costs and reduce product development times, is investigated in terms of capturing a battery module’s tolerance to a single cell failure. A 3D-FE model of a battery module was built, using a commercial software, to study thermal runaway propagation. The model assumes that when the cell jelly roll reaches a critical value, thermal runaway occurs. This approach was considered to study the module’s tolerance to a single cell failure, which was in reasonable agreement with what had been observed in full-scale experiments. In addition, quantitative sensitivity study on the i) model input parameters, ii) model space, and iii) time resolutions on the computed start time instant and time duration of thermal runaway were performed. The critical temperature was found to have the greatest influence on thermal runaway propagation. The specific heat capacity of jelly roll was found to significantly impact the thermal runaway time duration. The multi-physics model for battery thermal propagation is promising and worth to be applied with care for designing safer batteries in combination with physical testing.

A vented corn starch dust explosion in an 11.5 m3 vessel is studied using both experimental and numerical methods. The reduced explosion overpressure in the vessel is recorded using two pressure sensors mounted on the wall inside of the vessel. Unsteady three-dimensional Reynolds-Averaged Navier-Stokes simulations of the experiment are performed using the Flame Speed Closure (FSC) model of the influence of turbulence on premixed combustion. The model was thoroughly validated in previous studies and was earlier implemented into OpenFOAM CFD software. The self-acceleration of a large-scale flame kernel is associated with the influence of combustion-induced pressure perturbations on the flow of unburned reactants ahead of the kernel. Accordingly, the FSC model is extended by adapting the well-known experimental observations of the self-similarity of the kernel acceleration. Influence of different turbulence models on the simulated results is also explored. Thanks to the extension of the FSC model, the measured time-dependence of the pressure is well predicted when the k-omega-SST turbulence model is used. © 2021 The Authors

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.

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.

Thermal propagation is one of the major challenges when batteries will be used in dwellings in large scale. It means the exothermic reactions in the cell are out of control and can lead to a fast release of flammable and toxic gases. In a system involving a large number of cells, thermal runaway can rapidly propagate from one battery cell to the whole system, which means substantial fire and explosion risks, an event that is important to mitigate and prevent. Multi-physics simulations together with full-scale testing is a cost-effective method for designing safer batteries. This project aims at simulating thermal runaway initiation and propagation using a multi-physics commercial software GT-Suite. 

A battery thermal runaway model containing 12 prismatic cells based on 3-D Finite Element approach was built using GT-Suite. The computed thermal runaway time instants versus thermal runaway cell number were compared with full-scale experimental data with reasonable agreement. Quantitative sensitivity study on the model input parameters and model space and time resolutions on the computed start time instant and time duration of thermal runaway were performed. The thermal runaway model was then extended with an electric equivalent sub-model to simulate the short circuit. With the electrical model acting as the input to the thermal model, the most interesting output of the simulation is the change in temperature of the cells, dependent on the current in the cells, with respect to time. The current is determined by the value of the external resistance through which the short takes place and the voltage level of the battery pack. The obtained results from the above short circuit simulations can only be used as a starting point and not as absolute values for neither triggering the thermal model nor for accurately simulating a battery under an electrical load. Furthermore, GT-Suite was applied to simulate the gas dispersion inside a room. A comparative study of the dispersion of toxic gases during thermal runaway, utilising an arbitrary release of HCN to represent the battery gases, in a small compartment with natural ventilation was investigated and the results compared the same situation simulated in FDS. The pipe based modelling supported by GT-Suite has limited applicability and overestimated the concentrations close to the ceiling whereas the lateral concentrations where underestimated. 

The multi-physics model for battery thermal runaway process is promising and worth to be applied with care for designing safer batteries in combination with full-scale testing.