Search Results (16)

Accurate fire source location in an aircraft cargo compartment cannot be determined by common design practices. This study proposes an advanced fire location inversion framework based on a Convolutional Long-Short-Term Memory (ConvLSTM) network. A self-designed interpolation preprocessing module is introduced to realize the integration of spatial and temporal sensor data. The model was trained and validated using a comprehensive database generated from large-scale fire dynamics simulations. Hyperparameter optimization, including a learning rate of 0.001 and a 5 × 5 convolution kernel size, can effectively avoid the systematic errors introduced by interpolation preprocessing, further enhancing model robustness. Validation in simplified scenarios demonstrated a mean squared error of 0.0042 m and a mean positional deviation of 0.095 m for the fire source location. Moreover, the present study assessed the model’s timeliness and reliability in full-scale cabin complex scenarios. The model maintained high performance across varying heights within cargo compartments, achieving a correlation coefficient of 0.99 and a mean absolute relative error of 1.9%. Noteworthily, reasonable location accuracy can be achieved with a minimum of three detectors, even in obstructed environments. These findings offer a robust tool for enhancing fire safety systems in aviation and other similar complex scenarios. Full article

Assessments of subway train fires were conducted based on full-scale experiments and numerical simulations. The experimental platform and simulation model were established according to a real subway train in China. The results show that there was no obvious flame spread, and all the electrical circuitry maintained its integrity during a standard luggage fire. The maximum HRR (heat release rate) of the luggage fire obtained through the full-scale experiment was 155.5 kW, which was almost the same as the standard HRR curve provided in EN 45545-1. However, the fire only lasted approximately 180 s, which was much shorter than a standard fire (600 s). Through numerical simulations of an entire subway train, the side wall and roof ignited quickly, and the fire continually spread to the adjacent compartment under the extreme scenario with a gasoline pool fire and exposed winterproof material. The maximum HRRs of the luggage and gasoline pool fires were 179.7 and 17,800.0 kW, respectively. According to the experimental and simulation results, the Duggan method, which assumes that all combustibles inside a train compartment burn at the same time, was not appropriate for assessing the fires in the subway train, and a simple revised frame was proposed instead. Full article

In the maritime industry, hydrogen fuel cell ships demonstrate significant potential for development due to their environmental friendliness and high efficiency. However, the risks of fire and explosion caused by hydrogen leakage pose severe challenges to their safety. To enhance the safety of hydrogen fuel cell ships and mitigate the explosion hazards caused by leakage, this study employs the XiFoam solver in the OpenFOAM v9 to establish an explosion model for a full-scale hydrogen fuel cell compartment within a hydrogen fuel cell ship. The model simulates the transient explosion process following high-pressure hydrogen leakage under varying initial hydrogen concentrations and premixed fuel conditions. By analyzing the temporary evolution of temperature distribution, flame front propagation, and explosion pressure, the study provides a comprehensive understanding of the safety implications of hydrogen leakage at different locations within the fuel cell. Specifically, increasing the hydrogen concentration from ΦH₂ = 0.10 to ΦH₂ = 0.18 and ΦH₂ = 0.20 significantly elevates the overpressure peak and accelerates the flame speed from 250 m/s to 370 m/s, with local pressure gradients approaching the deflagration to detonation transition threshold. The simulation results contribute valuable insights into optimizing hydrogen fuel cell design, formulating effective fire safety strategies, and improving overall ship safety. Full article

Controlling the simulated smoke flow field is important in the airworthiness verification experiment for the smoke detection system in aircraft cargo compartments to accurately replicate actual fire smoke. In existing studies, the unsteady adjustment performance of the actuator to the simulated smoke flow field has not been comprehensively evaluated, and the model-based closed-loop flow control method encounters the unmodeled dynamics of the complex turbulent flow field. To solve the aforementioned problems, this study first uses the system identification method to obtain transfer function models for different actuation modes. Moreover, the transient adjustment capabilities of different actuation modes for the simulated smoke flow field are thoroughly evaluated. Then, an adaptive flow control law based on a radial basis function neural network is designed based on the selected actuating mode. Furthermore, closed-loop control experiments based on the adaptive control law are performed. The root locus of the transfer functions for two different actuation modes are compared, which reveals that adjusting the flow rate of simulated smoke exhibits a better stability margin than the actuation mode that regulates the upward momentum of simulated smoke. The experimental results in a full-scale mock-up of an aircraft cargo compartment demonstrate that the designed control law realizes dynamic tracking control with the unsteady concentration of actual fire smoke as the control target. Compared with that of PID control, the root mean square error of the control system is reduced by more than 40%. The simulated smoke under the closed-loop control obtains a light-transmission response equivalent to that of the actual fire smoke within a 5% error margin. The proposed closed-loop adaptive flow control method for simulated smoke approximates the unsteady process of actual fire smoke. It provides technical support for the replacement of actual fire smoke in the airworthiness verification experiment of smoke detection in aircraft cargo compartments. Full article

Aircraft cargo compartment fires are one of the main threats to the safety of civil aircraft. In this study, a series of numerical simulations on the fire suppression performance of water mist in cargo compartments was carried out to examine the effects of the spray pattern, droplet size, and nozzle layout. The fire dynamics simulator (FDS) code was used to construct a fire suppression scenario in a full-scale aircraft cargo compartment. The results show that the extinguishment time of a corner fire was longer compared with center and sidewall fires due to the relatively larger distance from the nozzle and, therefore, a lower effective number of droplets reaching the flame area. Solid and hollow spray patterns showed significant differences in the spray coverage area. For a fixed flow rate, the hollow spray showed better fire suppression performance than solid spray. When the droplet size varied from 50 to 400 µm, the fire extinguishment time first increased and then decreased, corresponding to the dominant mechanism of the smothering effect of small droplets and the cooling effect of large droplets. In addition, the nozzle layout affected the water coverage on the ground of the cargo compartment. With an increase in nozzle number, the water mist flux was more evenly distributed and the fire extinguishment effect also increased. Full article

A fire in the cargo compartment has a major impact on civil aviation flight safety, and according to the airworthiness clause of the CCAR-25, the detector must sound an alarm within 1 min of a fire in the cargo compartment. As for the cargo compartment of large transport aircrafts, the internal space is high and open, and the smoke movement speed becomes slower with significant cooling in the process of diffusion. Hysteresis can occur in smoke detectors because of their internal labyrinth structure, which causes the detector’s internal and external response signals to be out of sync. This research employs a numerical simulation to examine the detector response parameters under an ambient wind speed of 0.1–0.2 m/s and fits a Cleary two-stage hysteresis model, where τ₁= 0.09u^−1.43 and τ₂= 0.67u^−1.59. Finally, multiple full-scale cargo cabin experiments were conducted to validate the prediction model. The results show that the model’s predicted alarm range is 43.1 s to 49.0 s, and the actual alarm time obtained by the experiment falls within this interval, confirming the model’s accuracy and providing theoretical support for the structural design and layout of the aircraft cargo cabin smoke detector. Full article

Time to flashover is an important fire safety parameter. The present study investigated the effects of fuel moisture content on the time to flashover, crucial in fire safety analysis. Experiments and simulations of an ISO 9750-1 room model at 1/8 scale were performed by varying the wooden compartment boundaries’ moisture content between 5% and 16%. The results showed a linear increase in time to flashover with fuel moisture content. An empirical model to predict the time to flashover according to the moisture content was developed. The experiments showed that increasing the moisture from 6.5% to 14.4% prolonged the flashover time from $4.6 \min$ to $8.75 \min$. These experimental results are consistent with computational fluid dynamics (CFD) modeling using Fire Dynamics Simulator (FDS), which also depicts a corresponding increase in the time to flashover. These findings demonstrate the critical role of fuel moisture content in fire safety analysis. The results suggest that a 1/8-scale model can be utilized for cost-effective and easily manageable education and demonstration purposes. This includes helping fire brigades and fire academy students comprehend the significance of fuel moisture content in compartment fire development. Since the FDS modeling is not restricted to a 1/8 scale, the presented results are promising regarding CFD modeling of time to flashover in full-scale compartments. Full article

An assessment of the performance of FireFOAM in simulating a large-scale compartment fire scenario is presented in this study, using the Edinburgh Tall Building Fire Test I (2017) as the basis for evaluation. Different mesh geometries and sizes are tested, and both theory-based and experiment-based validation approaches are employed. The theory-based validation revealed that the implemented finite volumes method is generally conservative, but unaccounted deviations of up to 20% for the heat release rate were observed due to errors in numerically modelling subgrid phenomena, particularly with tetrahedral meshes. In the experiment-based validation, the simulated data showed good agreement with experimental measurements for flow patterns inside the compartment, neutral plane height, and temperatures outside the ceiling jet. However, there were relatively large errors in incident radiation in the hot gas zone, thermal boundary layer transient temperatures, and compartment inflow/outflow velocities. Systematic errors were attributed to deficient heat transfer boundary conditions and under-estimated air entrainment. The study also identified ways to improve run-time efficiency by implementing parallel processing or reducing solid angles in FVDOM, although using large meshes (30 cm and 40 cm cell size) resulted in faster run-times at the cost of accuracy. Full article

The modelling of fire behaviour in a compartment is the subject of this work. A small-scale experimental study was carried out in a compartment sized 0.5 m × 0.5 m × 0.5 m with a single door with a width of 0.2 m and a height of 0.4 m. The collected results were converted to full-scale results using Froude modelling. The objective of this study was to see how ventilation affects fuel decomposition rate, gas flow rate at the opening and the power generated inside the compartment. This small-scale experimental study allowed us to determine four values of the fuel’s (diesel) mass loss rate, which correspond to four values of the ventilation factor. Numerical simulation using Fire Dynamics Simulator (FDS) software was used to show the gas’ behaviour at the opening and the variation of the power generated inside the compartment. The vertical profiles of the experimental and numerical temperatures were compared. It was found that the dimensions of the opening have a significant influence on the power generated inside the compartment. Full article

Window sprinklers are commonly used to protect glass, but there is a lack of research on the effect of fire scale on protection. In this study, full-scale experiments on sprinkler-protected glass in building fires were carried out. The experimental process was simulated using CFD numerical simulation software (FDS), and the effect of the heat release rate on the protection effect was revealed based on the glass surface temperature and heat insulation efficiency. It was found that in a full-size compartment fire, the window sprinkler was able to protect the glass from being damaged by high-temperature smoke. The numerical simulation could effectively simulate the spray distribution pattern of a window sprinkler as well as the gas temperature evolution, and the simulation results matched well with the full-size experiments. The window surface temperatures all decreased rapidly and increased linearly with the HRR after the window sprinkler was activated. The steady-state window center temperatures were 40 °C, 60 °C and 76 °C when the HRR was 2 MW, 4 MW and 6 MW, respectively. The window center temperature was less than the critical temperature of glass breakage, indicating that the window sprinkler could protect the glass from fire damage well, within the fire scale of 6 MW. The thermal insulation efficiency in the edge region was slightly lower than that in the center of the window. In the range of 2 to 6 MW, there was no significant correlation between the thermal insulation efficiency and the HRR, and the thermal insulation efficiency was in the range of 54% to 59%. Full article

This paper proposes a hybrid multiscale approach to evaluate the fire performance of large multicompartment structures. A probabilistic network model is at the core of the proposed approach, whose inputs, namely the mean durations of the fire phases and fire transmission through the barriers between compartments (e.g., walls or ventilation ducts), are determined beforehand by a zone model, which is detailed in a companion paper and a one-dimensional computational fluid dynamics code. Next, a proof of concept is developed by applying the hybrid approach to different fire scenarios in a full-scale generic military corvette and a four-story office building. The simulation results highlight the strengths and limitations of the proposed approach. Regarding the latter, a field model is used to evaluate how the hybrid approach performs depending on the interaction between the entire building system and its ventilation and the fire. Finally, a statistical study is carried out to produce fire vulnerability and risk maps, ranking the fire compartments according to their vulnerability or propensity to generate serious fires. Full article

This paper presents the development and validation of a two-zone model to predict fire development in a compartment. The model includes the effects of the ceiling jet on the convective heat transfer to enclosure walls and, unlike existing models, a new concept of surrogate fuel molecule (SFM) to model multi-fuel combustion, and a momentum equation to accurately track the displacement of the smoke layer interface over time. The paper presents a series of full-scale fire experiments conducted in the IUSTI fire laboratory, involving different combinations of solid and liquid fuels, and varying the compartment confinement level. The model results are compared to the experimental data. It was found that for all fire scenarios, the experimental trends are well reproduced by the model. The SFM concept predicts oxygen and carbon dioxide concentrations in the extracted smoke to within a few percent of the measurements, which is a good agreement considering the sensitivity of the model to chemical formulas and combustion properties of fuels. Comparison with other measurements, namely average gas and wall temperatures, is also good. For the large fires reported in this study, the impact of the ceiling jet leads to a slight underestimation of wall temperatures, while the model gives conservative estimates for small fires. Full article

Along with simulated firefighting training, the development of virtual training systems and associated content has recently drawn attention as an alternative method for advanced firefighting training. In particular, to develop virtual training content, it is important to understand the combustion characteristics of indoor combustible materials and appropriately simulate their behavior. In this study, seven types of building fires were selected. From these types, indoor combustible materials of residential buildings were analyzed, and combustion tests were performed for each of three types of combustible materials. Furthermore, three types of indoor spaces, determined according to the combination of indoor combustible materials they contained, were divided into full-scale compartments, and a full-scale fire test was performed using this setup. Finally, the heat release rate and smoke production release of individual combustible materials and the room test were measured over time, and a fire dynamics simulation (FDS) was performed. As a result, it was confirmed that an effective evaluation of the occurrence and spread of fire indoors in buildings is possible through full-scale fire tests and FDS simulations. It is expected that simulation can be used as firefighting training content in the future by applying indoor combustible data and implementing complex and various fire development conditions. Full article

This paper examines the strength of wood adhesive bonds at high temperatures. The goal of this research is to better understand the conditions of heat delamination in cross laminated timber (CLT) that is exposed to fire. Heat delamination in CLT occurs when one lamination detaches from the composite panel before the char front reaches the bondline. Timber that falls from the panel, as a result of delamination, contributes additional fuel to the fire, which can cause fire regrowth, while the loss of a lamination causes a sudden loss in strength. Currently, to demonstrate that an adhesive does not delaminate, it must pass a full scale (6 m by 3 m) compartment fire test as prescribed in the PRG-320 product standard. In this work, we scaled down the mechanical loads and temperatures to 300 mm lap shear specimens. Seven different adhesives were tested and compared against solid wood controls with the same geometry as the lap shear specimens. Quasi-static tests were run where the specimens were loaded to failure at 25 °C and 260 °C, when the samples were at thermal equilibrium. Additionally, creep tests were performed where the load and temperature ramp was matched to the adhesive bondline temperatures measured in the large scale PRG-320 tests. With the exception of some of the polyurethane formulations, all adhesives passed the scaled-down creep test that resembles the PRG-320 standard. Of the polyurethane adhesives tested, only one formulation remained intact for the duration of the test. These results can be used to help better predict which adhesives may pass the PRG-320 test prior to full scale testing. Full article

The order/disorder characteristics of a compartment fire are researched based on experimental data. From our analysis performed by new, pioneering methods, we claim that the parametric Jensen-Shannon complexity can be successfully used to detect unusual data, and that one can use it also as a means to perform relevant analysis of fire experiments. Thoroughly comparing the performance of different algorithms (known as permutation entropy and two-length permutation entropy) to extract the probability distribution is an essential step. We discuss some of the theoretical assumptions behind each step and stress that the role of the parameter is to fine-tune the results of the Jensen-Shannon statistical complexity. Note that the Jensen-Shannon statistical complexity is symmetric, while its parametric version displays a symmetric duality due to the a priori probabilities used. Full article