FDS Ver. 6 による小型樹脂部品の延焼シミュレーション

Study on the effect of tunnel dimensions on the smoke layer thickness in naturally ventilated short tunnel fires

The prediction performance of design fire curves is numerically investigated for tunnel fire using the fire dynamics simulator (FDS). A large eddy simulation (LES) was adopted in the simulation of a previous 750 kW tunnel fire experiment. Based on the experimental heat release rate, t2-fire growth, quadratic and exponential design fire curves (DFCs) are mathematically constructed and adopted in the FDS simulation. The predictions of each DFCs are compared against the experimentally measured smoke temperature, smoke travel time, and carbon monoxide (CO) concentration. In addition, the prediction performance of the mixture fraction (MF) and mixing controlled fast chemistry (MCFC) combustion models, is compared. The simulation results of the MF and MCFC models are similar except for the CO concentration features. For the performance of the DFCs, t2-fire growth curve with the MF combustion model is the most effective combination, which demonstrated the most reasonable agreement with the experimental data.

This paper studied the effects of ambient pressure on the plug-holing phenomenon in tunnel fires with a shaft by a Fire Dynamics Simulator. The influence of ambient pressures on the smoke movement, temperature distribution, critical Richard number (Ric) and critical shaft height for plug-holing were analyzed in detail. A new prediction formula of smoke flow velocity considering different pressures was modified. A prediction formula of smoke temperature distribution beneath the ceiling under different pressures was developed. As a result, a prediction model of Richard numbers to determine whether the plug-holing occurs was proposed by combining smoke flow velocity and smoke temperature distribution. The critical Richard numbers (Ric) and critical shaft height (hc) increases as the pressure decreases. Outcomes in this study can provide references for the design of a natural ventilation system in tunnel fires at a higher altitude.

The critical ventilation velocity in tunnel fires—a computer simulation

Passive houses are becoming more and more popular due to energy efficiency requirements. An important aspect is their airtightness, i.e., they have a very low leakage. The present paper describes a preliminary numerical study on fire-induced pressure variations in a structure that resembles a passive house compartment. The configuration without ventilation system is considered in this paper. The fire source used in the experiment consists of wood cribs that have been simulated in the Fire Dynamics Simulator (FDS), version 6.5.2, as a cube with a prescribed heat release rate (HRR) curve (based on experimental measurements). The grid sensitivity study is conducted by using different mesh cell size and comparing the results of pressure variation. A cell size of 0.1 m is considered sufficient in this preliminary study. The maximum over-pressure obtained without ventilation reached up to 870 Pa in the experiment. Such high over-pressure will definitely hinder the escape of occupants. The structural integrity may also be affected by the over-pressure. Using a constant leakage area, which is the default option, the pressure difference without ventilation rises up to 2027 Pa in the simulation. A good agreement with the experimental data can only be achieved if the simulated leakage area is not kept constant when the room pressure rises. Tuning the leakage pressure exponent in FDS significantly reduces the deviation between the simulation and experimental results. The default setting of reference pressure difference in FDS is used to examine the influence of this parameter on the pressure prediction. When applying the default reference pressure difference, a smaller leakage pressure exponent is needed to reproduce experimental results. Therefore, the reference pressure difference has a certain influence on leakage area and should be set according to the pressure used in determining the reference leakage area during experiments. The overall pressure evolutions are qualitatively well captured in the FDS simulations, as these strongly depend on the fire heat release rate evolution, which was prescribed to match the experimental profile. However, in order to improve the current level of accuracy and address the general validity of the observations made in the present study, more experimental and numerical work need to be carried out.

Numerical modeling of flexible polyurethane foam combustion under two ignition modes

Analysis of entrainment phenomenon near mechanical exhaust vent and a prediction model for smoke temperature in tunnel fire

Fire safety is one of the most important parts in the safety management of urban electrical cable tunnels. Therefore, a new approach for quantitative risk assessment of fire in cable tunnels is proposed in this study. The approach integrates both the deterministic and the probabilistic analysis by incorporating a Monte Carlo based fire simulation simulated under the CFD code–fire dynamics simulator (FDS)–into an event tree model, which enables the fire development and the uncertainty existed in the fire progression process to be handled in the assessment. In order to validate the availability of this approach, a case study is also carried out in this paper. Through the analysis of fire risk using this approach, the fire risk can be quantified more accurately, and further analysis of the performance of different fire safety measures is also able to be conducted.

ABSTRACTThe influence of curvature on smoke spreading in a curved tunnel fire was studied using FDS (Fire Dynamics Simulator) software . The aim of the study was to understand the correlation between the influence range and the degree of the tunnel curvature. A dimensionless was defined after the force analysis of smoke, which was the ratio centrifugal force to component of reaction force in the radical direction. The results show that the temperature and velocity outside lateral smoke near fire sources are higher than that inside. The difference decreases with the radius of tunnel curvature. Taking =0.1 as the critical value, and the corresponding radius of curvature is defined as the critical radius . The critical radius depends on the Heat Release Rate (HRR) and the downstream locations. The larger the HRR, the greater the critical radius. The farther the fire source is, the smaller the range of the effect is.

Study on the smoke mass flow in T-shaped tunnel fire

Fires caused by cables occur frequently in mines, which endanger the safety of workers. To explore the characteristics of a multilayer cable fire in a mine tunnel, multilayer cable fire simulations were carried out using the Fire Dynamics Simulator (FDS). The influence of cable tray spacing, ignition position, and tunnel ventilation speed on the characteristics of the fire were studied. The results showed that these factors change the amount of contact between the cable and air, the heat accumulation, and the heat transfer by the flame interaction between the cables. It was also noted that increasing the spacing or wind speed both made the peak of heat release rate (PHRR) initially increase and then decrease. The influence of wind speed on the cable burnout rate in the upstream and downstream sides of the fire source was not consistent, and the wind speed had a sensitive effect on the cable burn out rate in the upstream side of the fire source. The higher the ignition position was, the longer the arrival time of PHRR was and the slower the fire developed. There was a higher burn velocity close to the ceiling. The cable hooks obstructed the cable fire. This study provides a theoretical basis for cable fire prevention and control in mine tunnels.

Accurate prediction of toxic gas concentrations during conveyor-belt fires is essential for ensuring mine safety, yet the nonlinear, time-varying, and turbulent characteristics of underground environments pose significant challenges for real-time forecasting. This study proposes a Physics-Informed Neural Network–Long Short-Term Memory (PINN-LSTM) hybrid model that integrates the one-dimensional convection–diffusion equation as a physical constraint with the sequential learning capability of an LSTM. Full-scale mine tunnel combustion experiments and Fire Dynamics Simulator (FDS) numerical simulations under multiple wind speeds and distances were conducted for model training and validation. The results indicate that the proposed PINN-LSTM achieves the lowest error metrics under all test conditions. The model reduced MSE and RMSE by 70–78% and 65–73%, respectively, compared with traditional LSTM models, and by 8–12% compared with the PINN-TCN variant. The proposed PINN-LSTM achieves the lowest error under all conditions. The PINN-LSTM model has strong prediction accuracy, physical interpretability, and real-time reasoning ability, providing a reliable and physically consistent solution for intelligent gas monitoring and early warning systems in underground fire scenarios.

SummaryExperimental studies are performed under different ventilation conditions to investigate the effect of ventilation on compartment fires. A compartment of size 4 m × 4 m × 4 m having a door of size 2 m × 1 m is used for experiments. The experiments are conducted with full door open and half door open conditions. Diesel, used as a fuel source, is placed in a pan of 40 cm diameter and 15 cm height, which is kept in the center of the compartment. During experiments a constant 12 cm height of the fuel is maintained above the pan bottom. The maximum heat release rate is found to be 100 kW and 115 kW in full door open and half door open experiments respectively. It is observed that the size of door opening affected the heat release rate, burning rate and thermal environment inside the compartment after the growth period of 800 s. The numerical simulation is also performed for full door open experiment using CFD code, Fire Dynamics Simulator (FDS, version 6.0.1) developed by NIST. Simulation is accomplished with the refinement of mesh size near the fire source; results from FDS closely match with the experimental results. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Numerical simulation of pressure changes in closed chamber fires