Smoke Layer Research Articles

Numerical modeling on mechanical smoke extraction efficiency of multiple lateral smoke extraction vents system in an immersed tunnel

In the case of immersed tunnel fires, lateral smoke extraction is a method employed to control the smoke movement with vents set in tunnel sidewalls due to limited space in height. This paper has investigated the smoke extraction efficiency of multiple lateral vents system using large eddy simulations (LES) in a fire dynamics simulator (FDS). The analysis is done on the impact of the lateral vent aspect ratio AR (n), lateral extraction velocity (v), and vent spacing distance (d) at various heat release rates HRRs (Q) on smoke extraction efficiency (E). The results show that the vent spacing distance (d) has a negligible impact on the smoke extraction efficiency. The smoke mass flow rate and smoke layer thickness in the tunnel changed significantly because of lateral extraction vents. The smoke extraction efficiency increases with dimensionless HRR Q* and vent aspect ratio n at constant lateral extraction velocity v, but decreases drastically with increasing dimensionless lateral extraction velocity v* due to an increase in fresh air drawn into the lateral vents. The smoke extraction efficiency reached to 100% at 1 m/s extraction velocity for vents of 3.25 aspect ratio. Finally, a correlation for smoke extraction efficiency in one-dimensional smoke spread stage was established based on dimensional analysis, which can provide a reference guide for designing a ventilation system in tunnels with lateral vents.

Study on the influence of vent area on porosity-controlled wood crib compartment fires prior to flashover

PurposeThis study describes a series of experiments investigating the upper hot layer temperature profile in a confined space under different ventilation conditions for porosity-controlled wood crib fires for pre-flashover conditions.Design/methodology/approachFull-scale compartment (4 m × 4 m × 4 m) experiments were carried out for four-door openings, i.e. 100%, 75%, 50% and 25% of the total vent area (2 m × 1 m) with the wood crib as a fuel load. The temperature of the upper hot smoke layers of the compartment was recorded with the help of four layers of thermocouples for varying vent areas.FindingsThe effect of ventilation on the properties, i.e. mass loss rate, enclosure temperature, heat release rate and carbon monoxide (CO) gas concentration, has been measured and analyzed. The effect of ventilation on heat flux and flame temperature has also been studied. Compartment gas temperature has been examined by five wood crib burning stages: Ignition, growth, steady burning, recess and collapse.Originality/valueFindings demonstrate that the influence of vent openings varies for the burning parameters and upper layer temperature of the compartment. The current results are beneficial in analyzing thermal risks concerning compartment fire and fire safety engineering projects.

Study on the effect of obstacles on smoke diffusion and airflow structure in subway stations

Although obstacles exist in every subway station, the impact of obstacles on smoke diffusion characteristics is always overlooked. This work investigates the effect of rectangular obstacles on the ceiling temperature distribution, vertical temperature distribution, and airflow field structure in a subway station fire scenario. Small-scale experiments and numerical simulations are conducted considering varied fire location, heat release rate, blockage ratio, and obstacle location. A dimensionless temperature rise ratio is proposed to quantify the obstacle influence. The key results include (1) Obstacles would cause a proportional decrease in the ceiling temperature rise behind. And the proportion is positively correlated with the blockage ratio but not related to heat release rate, fire location, and obstacle location. (2) The influence of obstacles on vertical temperature rise presents hierarchical characteristics. The same proportional decrease is observed in the smoke layer at the top. As the height decreases in the mixture layer, the temperature rise ratio would also decrease gradually. The air layer at the bottom is kept at a small temperature rise ratio. (3) The wake area behind the obstacle is composed of a recirculation area and a wake recovery area. There is less smoke and slower airflow velocity in the wake area, which means the acquired temperature rise rule is not applicable in this area. A calculation method of the length of the wake area based on the airflow velocity characteristics is presented. This work aims at arousing attention on the influence of obstacles in the fire smoke studies in subway stations.

Stability of smoke stratification under the impact of water sprays with various droplet size ranges in longitudinally ventilated road tunnels

This paper presents a simplified model of tunnel smoke stratification, which can be used to study the effect of sprinkler water spray on stratified stability. The stratified flow downstream of a tunnel fire is represented by a two-layer thermal flow, with the hot upper layer representing the smoke and the cold lower layer representing the ventilation air. The dragging effects of sprays from sprinkler nozzles with various K-factors were numerically studied using FDS code (version 6.7.3). Experiment data reported in the literature successfully validated the accuracy of the CFD method. Spray-induced smoke movements, including the smoke logging distance and the horizontal movement, were determined by releasing a series of massless tracers from the smoke layer inlet. The findings of the work indicate that the dragging effect of a water spray is droplet-size-dependent. The smaller the droplets, the larger the dragging force for a given volumetric spray rate. By applying dimensional analysis and introducing the volume mean diameter into the governing parameters, some correlation models that account for the droplet size were proposed to predict the spray-induced smoke movements and smoke layer heat loss. The new correlation models help complete previous work by the authors and are of practical use for tunnel fire safety design where water sprays are included alongside a longitudinal ventilation system.

Inverse tracing of fire source in a single room based on CFD simulation and deep learning

Inverse tracing of fire source location is important for investigation after the fire accidents. In this work, the CFD simulations and deep learning were combined to explore a more efficient and intelligent tool for fire investigation. Firstly, a CFD model for single room was built using FDS. Then abundant simulations were performed by varying the initial conditions to collect massive data including temperature distribution and smoke layer heights in the room. The dataset was divided into two parts for the training and validation of BP network, respectively. The inverse model and forward model with the same data set and neural network parameters were established, which saved the time in adjusting models and producing data and improves the efficiency of research. The shared data sets and neural network parameters did not affect the final prediction results. The accuracy of forward and inverse models is still excellent, reaching a high accuracy. In particular, the accuracy of the inverse model had been improved to more than 99% compared with previous studies. The accuracy of the forward model is more than 80%. Besides, the inverse model's robustness was also examined, the model is still valid when some input features are lost.

A multi-scale experiment analysis of air entrainment and heat exhaust coefficient under lateral smoke exhaust in tunnel fires

This study investigated the air entrainment caused by a lateral smoke exhaust system via full-scale and model-scale tests. A particular phenomenon, shear flow, was observed downstream of the exhaust vent. The phenomenon of shear flow was more intense when the exhaust velocity increased, which destroyed the smoke layer stratification and strengthened the air entrainment. Plug-holing and shear flow intensified air entrainment, and the functional relationship between air entrainment, Froude number, and dimensionless exhaust vent size was established. The relationship between the air entrainment and heat exhaust efficiency was studied, and it was found that the heat exhaust coefficient was positively related to the air entrainment. The functional relationship between the heat exhaust coefficient and air entrainment for different lateral exhaust vent sizes was presented. In addition, we observed that lateral smoke exhaust exhibit little effect on the centerline temperature distribution. A model that can be used to describe the centerline temperature distribution with lateral smoke exhaust systems was developed.

A study of the characteristics of smoke stratification in lateral point smoke exhaust tunnel

In order to study flow stratification behavior in lateral smoke exhaust mode, experiments were carried out in reduced-scale model and numerical simulations model. The characteristics of smoke layer interface, smoke layer thickness, vertical temperature and normalized shear velocity in tunnel with different heat release rates were analyzed. The flow pattern was visualized by a semiconductor laser. The stratification pattern was found to fall into three regimes. Buoyancy, inertia force and suction force, as three factors affecting the flow stratification of smoke, are related by a new dimensionless number. At region I (Frs<2.4), the buoyancy stratification was stable, and there is an obvious interface between the upper smoke layer and the lower cold air layer. At region II (2.4<Frs<4.8), the buoyant flow stratification was stable, but the stratification interface between smoke and cold air was unstable. At region III (Frs>4.8), the stratification becomes unstable, the mixing between smoke and cold air was intense, and there is no obvious stratification interface.

Effect of ventilation on carbon monoxide and soot particles emissions in a confined and mechanically-ventilated fire

Fire behavior in a 1 m3 confined and mechanically ventilated compartment is investigated experimentally. The main objective is to study carbon monoxide and soot particle emissions by four different fuels: pure n-heptane, technical-grade dodecane, kerosene Jet A-1, and Mobil DTE oil heavy medium. Air Renewal rates are set at 4.83 ACH, 9.67 ACH, and 17.8 ACH, while the fuel pan diameters are 0.115 m, 0.14 m, and 0.19 m. The results show that decreasing the renewal rate or increasing the pan size decreases the mass loss rate and soot emissions. However, CO emissions increase. Lighter fuels exhibit higher mass loss rates and CO emissions than heavier fuels. The highest smoke temperatures are produced at high renewal rates and large pan diameters. Meanwhile, soot emission levels decrease in the order of kerosene > dodecane > Mobil oil > heptane. High levels of soot but low CO emissions are present in well-ventilated fires. However, high CO but low soot emissions appear in under-ventilated fires. The soot particles collected in the smoke layer show unimodal distribution. The modal diameter of the particles ranges from 220 nm to 300 nm.

Numerical study on thermally driven smoke flow characteristics in long tunnels under natural ventilation

The paper focuses on the flow structures and mass flow rates of thermally driven smoke flows induced by fires in long transportation tunnels under natural ventilation. The important influencing factors including heat release rate (HRR), tunnel width and height, are taken into consideration. The mechanism of the smoke flow movement is explored. The results show that for a fire in a long naturally ventilated transportation tunnel, there exists a critical point which is dependent on HRR and tunnel geometry. This critical point is defined as the location where the smoke layer thickness and the outgoing mass flow rate increase towards it and decrease after it. Further, it is found that the critical point moves farther away from the fire source in a wider or higher tunnel, while it lies closer to the fire source for a higher HRR. A correlation is proposed to estimate the location of the critical point. The outgoing mass flow rates along the tunnel are calculated using the two-layer flow model and well-mixed flow model of thermally driven flows, and the results indicate that these models produce satisfactory predictions of the mass flow rates if the vertical temperature profile is known.

Effects of control zone, exhaust rate and station extent on smoke dispersal during emergency concourse fires in underground stations

Effective mass rapid transit plays an essential role in public transportation for sustainable urban development. This study investigates the temporary spreading behavior of smoke in the concourses of underground stations. The computational approach implements the software package FDS® 6.7.4 along with a post-processing visualization module (Smokeview) to simulate the smoke dispersal processes for determining the unsteady distributions of temperature and visibility during emergency concourse fires. The interfacial temperature between the lower air layer and upper smoke layer is employed to estimate the smoke layer height, as guided by NFPA-92B. The FDS predictions agree reasonably well with the measured fire plume temperatures at the heights of 7.0 m and 13.0 m above the fire source from the available literature in the time duration of 600 s for model verification. FDS calculations are then extended utilizing the validated computational model to explore the effects of the control area, exhaust rate and station size on the smoke spreading progressions. The simulated results reveal the effectiveness of installing static barriers to restrict smoke dispersal within a specific control space; however, the implementation of suitable mechanical exhaust system is required to extract the dense smoke out of the concourse. For the scenario of a high volume MRT underground station, the design adopting the smoke control area of 20 m × 15 m in conjunction with the exhaust rate of 15 m3/s can attain clear visibilities for emergency evacuation. However, the simulations show the inappropriateness of arranging the same design layout of control area and exhaust rate as safety measures of underground fires for a medium volume station.

Multiwavelength fluorescence lidar observations of smoke plumes

Abstract. A five-channel fluorescence lidar was developed for the study of atmospheric aerosol. The fluorescence spectrum induced by 355 nm laser emission is analyzed in five spectral intervals using interference filters. Central wavelengths and the widths of these five interference filters are, respectively, as follows: 438 and 29, 472 and 32, 513 and 29, 560 and 40, and 614 and 54 nm. The relative calibration of these channels has been performed using a tungsten–halogen lamp with a color temperature of 2800 K. This new lidar system was operated during summer–autumn 2022, when strong forest fires occurred in the Moscow region and generated a series of smoke plumes analyzed in this study. Our results demonstrate that, for urban aerosol, the maximal fluorescence backscattering is observed in a 472 nm channel. For the smoke, the maximum is shifted toward longer wavelengths, and the fluorescence backscattering coefficients in 472, 513 and 560 nm channels have comparable values. Thus, from the analysis of the ratios of fluorescence backscattering in available channels, we show that it is possible to identify smoke layers. The particle classification based on single-channel fluorescence capacity (ratio of the fluorescence backscattering to the elastic one) has limitations at high relative humidity (RH). The fluorescence capacity indeed decreases when water uptake of particles enhances the elastic scattering. However, the spectral variation of fluorescence backscattering does not exhibit any dependence on RH and can be therefore applied to aerosol identification.

Experimental study on vertical temperature distribution of the two-layer smoke flow in tunnel during construction

For a tunnel fire during construction, the formation of two-layer smoke flow underneath the ceiling accelerates the smoke descent threatening the personnel evacuation. As an important indicator of smoke diffusion, the gas temperature distribution inside tunnel is worthy of analysis in depth. However, the vertical temperature profiles within this kind of two-layer smoke flow inside tunnel have not been experimentally studied. To fill the gap, this paper conducts a series of fire experiments in a 1/20 reduced-scale tunnel model. Multi-variables including fire heat release rate, fire position, lifting-up height of fire source, inclined shaft slope, are considered. The visible flame shape, O2 volume fraction and gas temperature are recorded and measured. The burning of the propane gas persists steadily for 20 mins without the occurrence of self-extinction. The structural evolutions of the smoke layer are predicted by FDS simulation and traced by the laser sheet. The smoke descent process in the main tunnel is divided into three stages. The effects of fire source position, inclined shaft slope, fire heat release rate and lifting-up height on the gas temperature distributions inside tunnel are analyzed. The measured temperature rise and the perpendicular distance from the ceiling are normalized by ΔTmax and LT, respectively. At various longitudinal positions (1.82 ≤ │X-dm│/Hef ≤ 10.68), the normalized temperature distributions follow the same curve, independent of the values of Qm, dm and hm. The self-similarity of the vertical temperature distribution within the two-layer smoke flow are sufficiently proved. It is found that ΔT/ΔTmax with z/LT shows a two-regional variation. Based on over 1,740 temperature data from 36 experimental cases, an experimental equation is proposed to describe the gas temperature rise in the region between the fire source and the closed end. The proposed model shows good agreement with the measured data, which can help the researchers to better assess the smoke layer height inside tunnel.

Numerical Simulation on Smoke Temperature Distribution in a Large Indoor Pedestrian Street Fire

In order to study the characteristics of fire smoke spread and temperature distribution of a large indoor pedestrian street under different heat release rates and smoke exhaust modes, this paper focuses on the analysis of fire smoke spread, visibility, smoke temperature distribution and variation curves in an atrium. This paper uses a numerical simulation method to conduct research. PyroSim fire simulation software is used to calculate this project, which is based on a full-scale experimental design scheme. The numerical simulation results show that under the conditions of higher heat release rate, the smoke spread rate is greater than that under the conditions of lower heat release rate. Furthermore, the average temperature of smoke in the atrium is also greater, up to about 400 °C. The conditions of a higher heat release rate also show the characteristics of faster generation, faster spread and a larger volume of smoke. When the smoke exhaust system is turned on, the thickness of the smoke layer and the smoke temperature decrease. There then comes a situation where the stabile section of the fire ends in advance. The simulation results of vertical temperature distribution in an atrium can fit the modified McCaffrey plume model in any case. Under all cases, the smoke temperature reaches the maximum directly above the fire source. The horizontal dimensionless smoke temperature rises under the atrium roof, and decreases exponentially with the dimensionless distance from the fire source. The greater the heat release rate of fire source is, the smaller the attenuation coefficient is, with a more than 50% change. When the smoke exhaust system is turned on, the smoke flow accelerates and the smoke is cooled rapidly. Thus, the attenuation coefficient increases. Additionally, the effect of mechanical smoke exhaust is better than natural smoke exhaust, because mechanical smoke exhaust makes air flow and heat exchange more intense. The variation amplitudes of the attenuation coefficient under natural smoke exhaust and mechanical smoke exhaust are 13% and 22%, respectively.

Self-lofting of wildfire smoke in the troposphere and stratosphere: simulations and space lidar observations

Abstract. Wildfire smoke is known as a highly absorptive aerosol type in the shortwave wavelength range. The absorption of sunlight by optically thick smoke layers results in heating of the ambient air. This heating is translated into self-lofting of the smoke up to more than 1 km in altitude per day. This study aims for a detailed analysis of tropospheric and stratospheric smoke lofting rates based on simulations and observations. The main goal is to demonstrate that radiative heating of intense smoke plumes is capable of lofting them from the lower and middle free troposphere (injection heights) up to the tropopause without the need of pyrocumulonimbus (pyroCb) convection. The further subsequent ascent within the lower stratosphere (caused by self-lofting) is already well documented in the literature. Simulations of absorbed solar radiation by smoke particles and resulting heating rates, which are then converted into lofting rates, are conducted by using the ECRAD (European Centre for Medium-Range Weather Forecasts Radiation) scheme. As input parameters thermodynamic profiles from CAMS (Copernicus Atmosphere Monitoring Service) reanalysis data, aerosol profiles from ground-based lidar observations, radiosonde potential temperature profiles, CALIOP (Cloud–Aerosol Lidar with Orthogonal Polarization) aerosol measurements, and MODIS (Moderate Resolution Imaging Spectroradiometer) aerosol optical depth retrievals were used. The sensitivity analysis revealed that the lofting rate strongly depends on aerosol optical thickness (AOT), layer depth, layer height, and black carbon (BC) fraction. We also looked at the influence of different meteorological parameters such as cloudiness, relative humidity, and potential temperature gradient. To demonstrate the applicability of our self-lofting model, we compared our simulations with the lofting processes in the stratosphere observed with CALIOP after major pyroCb events (Canadian fires in 2017, Australian fires in 2019–2020). We analyzed long-term CALIOP observations of smoke layers and plumes evolving in the UTLS (upper troposphere and lower stratosphere) height region over Siberia and the adjacent Arctic Ocean during the summer season of 2019. Our results indicate that self-lofting contributed to the vertical transport of smoke. We hypothesize that the formation of a near-tropopause aerosol layer, observed with CALIOP, was the result of self-lofting processes because this is in line with the simulations. Furthermore, Raman-lidar-based aerosol typing (in Leipzig and the High Arctic) clearly indicated the dominance of smoke in the UTLS aerosol layer since August 2019, most probably also the result of smoke self-lofting.

Smoke Stratification in a Mine Drift with Multiple Objects Downstream

Abstract The smoke behaviour and smoke stratification of a fire in a mine drift will be one of the decisive factors affecting the risk to mining personnel during a fire. This paper studies the smoke stratification in a mine drift with multiple objects downstream of the fire, at varying distances and number of objects. Data for the study was provided from earlier model-scale fire experiments and CFD modelling was performed for in-depth analysis of specific phenomena. It was found that at considerable downstream distances from the fire, the smoke stratification differences were significant, reflecting the high impact of multiple objects. With an increasing distance between the objects downstream, an increased degree of mixing and decreased stratification occurred. With an increasing distance between the burning object and the second object, the smoke layer will descend further before encountering the object and the smoke stratification on the upstream side of the second object will decrease. The increased mixing of the hot gases flowing from the burning object will have a more significant effect on the overall stratification due to the higher temperatures. An increasing number of objects downstream will not by itself lead to increased stratification, with shorter distances between the objects and an increasing number of objects, the smoke stratification may instead be retained for a longer distance. An increasing flow velocity will result in decreasing stratification found foremost downstream of the burning object, as the tilt of the plume will increase and interact increasingly with the second object.

The CALIPSO version 4.5 stratospheric aerosol subtyping algorithm

Abstract. The accurate classification of aerosol types injected into the stratosphere is important to properly characterize their chemical and radiative impacts within the Earth climate system. The updated stratospheric aerosol subtyping algorithm used in the version 4.5 (V4.5) release of the Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) level 2 data products now delivers more comprehensive and accurate classifications than its predecessor. The original algorithm identified four aerosol subtypes for layers detected above the tropopause: volcanic ash, smoke, sulfate/other, and polar stratospheric aerosol (PSA). In the revised algorithm, sulfates are separately identified as a distinct, homogeneous subtype, and the diffuse, weakly scattering layers previously assigned to the sulfate/other class are recategorized as a fifth “unclassified” subtype. By making two structural changes to the algorithm and revising two thresholds, the V4.5 algorithm improves the ability to discriminate between volcanic ash and smoke from pyrocumulonimbus injections, improves the fidelity of the sulfate subtype, and more accurately reflects the uncertainties inherent in the classification process. The 532 nm lidar ratio for volcanic ash was also revised to a value more consistent with the current state of knowledge. This paper briefly reviews the previous version of the algorithm (V4.1 and V4.2) then fully details the rationale and impact of the V4.5 changes on subtype classification frequency for specific events where the dominant aerosol type is known based on the literature. Classification accuracy is best for volcanic ash due to its characteristically high depolarization ratio. Smoke layers in the stratosphere are also classified with reasonable accuracy, though during the daytime a substantial fraction are misclassified as ash. It is also possible for mixtures of ash and sulfate to be misclassified as smoke. The V4.5 sulfate subtype accuracy is less than that for ash or smoke, with sulfates being misclassified as smoke about one-third of the time. However, because exceptionally tenuous layers are now assigned to the unclassified subtype and the revised algorithm levies more stringent criteria for identifying an aerosol as sulfate, it is more likely that layers labeled as this subtype are in fact sulfate compared to those assigned the sulfate/other classification in the previous data release.

Development and Experimental Study of Mobile Fire Smoke Decontamination System

Fire smoke decontamination equipment, such as fire-fighting robots and smoke exhaust robots, is mainly used in long and narrow spaces such as underground garages. In several recent decades, the study of fire smoke spread in narrow spaces and fire smoke decontamination equipment stimulated the interests of many researchers. However, present equipment cannot eliminate insoluble toxic gases such as CO and may decrease the height of the smoke layer, causing great difficulty to rescue. In this study, a novel mobile fire smoke decontamination process and system are proposed. The experimental study and theoretical prediction of the system are conducted. The results show that the developed equipment is able to eliminate fire smoke particles and CO, cool the space, and improve the visibility of the fire site. The developed equipment can reduce the space temperature to below 60 °C, reduce the CO concentration to below 145 ppm, and enhance the visibility to more than 50 m in the rectangular tunnel after operating for 30 min under 4 MW fire condition.

Experimental study on the impact of asymmetric heavy rainfall on the smoke spread and stratification dynamics in tunnel fires

This work examines the impact of heavy rainfall on the smoke spread and stratification dynamics in tunnel fires with a reduced-scale (1:15) experimental platform. Scaled tests vary the rainfall intensity (up to 60 mm/h, equivalent to 232 mm/h in nature), raindrop size (1.0–1.5 mm, equivalent to 4–6 mm in nature), and fire heat release rate (2.1–6.7 kW, equivalent to 2–6 MW in real scale). We found that the asymmetric rainfall on one exit can induce the longitudinal airflow inside the tunnel due to the dissipation of the raindrop momentum and the rain-induced air entrainment. The velocity of such a longitudinal airflow increases with increasing rainfall intensity, and smaller raindrops tend to induce faster longitudinal airflow. The spread and stratification of hot smoke are sensitive to the induced airflow. In the absence of rainfall, there was a symmetrical temperature distribution from the fire source due to the symmetrical air entrainment. Under rainfall, the temperature distribution of tunnel fires gradually becomes less symmetrical, and the smoke stratification interface becomes unclear. With the increase in rainfall intensity, the phenomenon of smoke back-layering appears, and the smoke layer height decreases. Under a small rainfall intensity, raindrop size has a higher impact on the smoke stratification near the fire source. This study aims to attract more attention to tunnel safety under the dual disaster of fire and extreme weather and support the emergency response.

Effects of ambient pressure on characteristics of smoke movement in tunnel fires

This paper systematically studies the effect of ambient pressure on smoke movement in tunnel fires by numerical investigations. Because of the correlation between ambient pressure and air density, the influence of pressure on smoke movement can be considered as the effect of ambient air density in this study. The results of numerical simulation show that under a certain fire HRR, the average smoke layer thickness downstream of fire increases with the increase of both ambient pressure and longitudinal ventilation velocity. Compared with ambient pressure, the ventilation velocity has a greater impact on smoke layer thickness. The concept of turning velocity VT was put forward for the first time when analyzing the effect of ambient pressure on smoke backlayering length. When V<VT, the smoke backlayering length will decrease with the decreasing pressure. When VT<V<VC, the smoke backlaying length will increase with the decreasing pressure. Such results can be attributed to the two-sides effect of ambient pressure on the thermal buoyancy of smoke plume at the smoke backlayering front. Furthermore, the critical velocity has a negative correlation with the ambient pressure. According to the results of dimensional analysis, the prediction models of the smoke backlayering length and critical velocity considering the effect of ambient pressure were established. These findings will provide some basic references for the design of ventilation system in high-altitude tunnel.

Effects of Quantity and Arrangement of a Flame-Retardant Cable on Burning Characteristics in Open and Compartment Environments

The results of cable burning experiments conducted in a well-controlled or open environment may differ from fire phenomena in an actual installation environment of cables where the effects of ventilation conditions and thermal feedback exist. In order to prevent the misunderstanding of fire phenomena due to these differences, the changes in burning characteristics in open and compartment environments were investigated for a flame-retardant (TFR-8) cable and general PVC (VCTF) cable arranged on three-layer trays. As a result, it was confirmed that the fire scale, fire spread area, and cable damage varied greatly depending on the cable arrangement under the same cable quantity condition. Furthermore, the maximum heat release rate (HRR) and fire growth rate of TFR-8 in the compartment environment increased more than 3-times compared to the open environment, and showed a similar level of fire risk to VCTF even though it is a flame-retardant cable. Additional experiments using vertical and horizontal openings of various shapes were conducted to evaluate the individual contributions of thermal feedbacks from the wall and smoke layer to the changes in burning characteristics within the compartment. The results of this study can be used as basic data to reduce fire damage while providing an essential understanding of cable fire phenomena.