Gas temperatures in heavy goods vehicle fires in tunnels

Large-scale fire tests were carried out with heavy goods vehicle (HGV) cargos in the Runehamar tunnel in Norway. The tunnel is a decommissioned, two-way-asphalted road tunnel that is 1600 m long, 6 m high and 9 m wide, with a slope varying between 0.5% uphill and 1% downhill. In total four tests were performed with fire in an HGV set-up and a longitudinal ventilation flow of approximately 3 m/s. In three tests, mixtures of different cellulose and plastic materials were used; in the fourth test a commodity consisting of furniture and fixtures was used. In all tests the mass ratio was approximately 82% cellulose and 18% plastic. A polyester tarpaulin covered the cargo.One purpose of the large-scale tests was to obtain new relevant gas temperature-time data from large-scale HGV fires in tunnels. There is presently a lack of such information for road tunnels. The maximum heat release rates produced by the four different fire loads varied between 66 and 202 MW resulting in maximum gas temperatures at the ceiling ranging between 1281 and 1365 °C. A comparison with literature values shows that the gas temperatures obtained here are uniformly higher than those obtained in other similar large-scale test series conducted using solid materials. A mathematical correlation of a temperature–time curve is given and this is the best representation of the measured temperature and a combination of frequently used temperature curves for tunnels (the HC curve and the RWS curve).     

Variation of heat release rate with forced longitudinal ventilation for vehicle fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study using a Bayesian methodology to estimate the effect of forced longitudinal ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of car and heavy goods vehicle (HGV) fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that forced ventilation has a great enhancing effect on the HRR of HGV fires, but has little effect on the HRR of car fires.     

Spilled liquid fires in tunnels

The study focuses on release of liquids inside tunnels from tankers containing dangerous good. Experiments and analysis from large scale tests are presented. The tests include different leakage rates, leakage type, liquids, spillage sizes on sloping surfaces and heat release rates. Models for estimation of leakage rates, spillage sizes and heat release rates for different scenarios are presented. The results are important to use in the design of active fire protections systems in tunnels including ventilation, fixed fire-fighting and drainage systems.     

Heat radiation from fires of aviation fuels

As a practical matter, the horizontal radiation profile of a free-burning fire may be more significant than the vertical profile from a fire-fighting point of view. Note: Presented at the 1972 Fall Meeting, Eastern States Section, The Combustion Institute, December 7–8, 1972, Princeton University, Princeton, NJ.     

Effect of cross section and ventilation on heat release rates in tunnel fires

Model scale fire tests were performed in tunnels with varying tunnel widths and heights in order to study the effect of tunnel cross-section and ventilation velocity on the heat release rate (HRR) for both liquid pool fires and solid fuel fires. The results showed that for well ventilated heptane pool fires, the tunnel width nearly has no influence on the HRR whilst a lower tunnel height clearly increases the HRR. For well ventilated solid fuel fires, the HRR increases by approximately 25% relative to a free burn test but the HRR is not sensitive to either tunnel width, tunnel height or ventilation velocity. For solid fuel fires that were not well ventilated, the HRRs could be less than those in free burn laboratory tests. In the case of ventilation controlled fires the HRRs approximately lie at the same level as for cases with natural ventilation.     

Predicting the heat release rates of liquid pool fires in mechanically ventilated compartments

In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver.     

Smoke release from wall linings in full-scale compartment fires

Smoke densities and rates of smoke production have been measured when different wall lining materials (chipboard, fibre insulating board, hardboard, polystyrene, plasterboard, and glass reinforced polyester) were exposed to fire in a full-scale compartment.A wooden crib was used as the main fire load, of a size equivalent to burning the contents of a lightly furnished room, which produced a level of radiation intensity on the walls similar to that used with the National Bureau of Standards test.Implications of the smoke released by the different linings are discussed, with some reservations because only a single test was carried out with each wall lining, and because in tests of this kind fire development and smoke production relate to environmental conditions and to the exact nature of the material examined.     

The influence of longitudinal ventilation systems on fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study investigating the influence of forced longitudinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, made by a panel of experts, with data from experimental fire tests in tunnels. Results are presented and the implications are discussed. The influence of longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts’ estimates, causing a fire to grow ten times larger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rate of small pool fires may be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected to be greatly affected by forced ventilation at low ventilation velocities.     

Heat transfer mechanisms in liquid pool fires

The heat transfer mechanisms in liquid pool fires were studied. The heat balance in the combustion system which includes both the liquid fuel and the burner vessel was discussed. The convective heat from the vessel wall to the fuel is dominant in small scale pool fires, and was calculated using the finite difference program. The heat flux between the wall and the fuel during flame spreading over the fuel below its flash point in the vessel of small width was calculated. From the results, it was found that the poorer the thermal conductivity of the vessel the larger the heat flux from the wall to the fuel immediately below the fuel surface. The liquid level at which a flame self-quenches was measured for various materials and wall thicknesses of the vessel. The concentration gradient of fuel at the self-quenching liquid level was found to be nearly constant for a given fuel.     

Measuring mass loss rates in free burning fires

Accurate data on mass loss rates of fuels in large, free-burning fires are scant. However, the authors report a method of making such measurements, which, when tested, provided reliable data. Note: Mr. Murray is now in the Forestry and Timber Bureau, Canberra, Australia; Mr. Northcutt is now in the Division of Forest Fire and Atmosphere Research, Forest Service, USDA, Washington, D. C.; and Mr. Countryman is stationed at Riverside, California.     

Full-scale experiment research and theoretical study for fires in tunnels with roof openings

In order to assess the possibility of exhausting smoke through passive roof openings and the influence of smoke on personnel in the tunnels, full-scale fire experiments in tunnels with roof openings are carried out, which were rarely reported in the previous references. The data of smoke propagation, smoke sedimentation, velocity field and temperature field are measured. On the basis of the smoke longitudinal propagation laws, the prediction model of calculating backlayering distance is built. The Kurioka model and the built mathematical models are validated by those experiments. All the experimental data presented in this paper can be further applied for verification of numerical models, and bench-scale experimental results. Those full-scale experimental results and theoretical analysis can also be used for directing tunnel fire research, which afforded scientific gist for fire protection and construction of road tunnel with roof openings.     

倾斜隧道内可燃液体连续泄漏漫流特征及其潜在火灾热释放速率试验研究

摘 要：为研究倾斜隧道内可燃液体泄漏漫流引发的潜在火灾危险性,建立了双向坡度可调试验平台,对连续泄漏漫流形态、宽度、面积等特征随隧道坡度的变化规律进行了试验研究;同时开展火灾试验,研究燃料厚度对热释放速率的影响。结果表明：当隧道仅存在纵坡时,随着坡度的增加,液体漫流宽度及面积缩小;当同时存在横坡和纵坡时,液体流向隧道侧墙,漫流长度及面积缩小。液体漫流平均厚度为2 mm,该厚度下可燃液体热释放速率为经典模型计算值的30%~50%。结合上述试验研究,可对隧道内可燃液体连续泄漏漫流潜在火灾热释放速率进行估算。研究结果表明：隧道横坡由1%增加至2%,液体漫流面积可减少约50%,大幅降低潜在的热释放速率。     

A simplified model of fires in road tunnels. Comparison with three-dimensional models and full-scale measurements

A new simplified model (UPMTUNNEL) for the simulation of accidental fires in road tunnels with longitudinal ventilation is presented. The model follows a mixed approach, and has characteristics typical of both field and zone models. Like field models, the proposed model calculates the main properties at every point in the whole domain. The tunnel is divided in two zones: the plume, located upstream from the point at which the smoke hits the ceiling, and a diffusion zone extending downstream. Each of these two regions is analyzed assuming steady-state conditions. The plume is described by one-dimensional conservation equations for turbulent flows. To deduce the 1D equations, the 3D problem is considered to be parabolic along the center-line of the flame, and self-similar profiles in planes normal to this line are assumed. The diffusion region is studied as an incompressible unidirectional problem, described by the energy conservation equation. 3D models and full-scale experiments have been used in order to validate the results of the UPMTUNNEL model. Two different general-purpose codes are employed: FLUENT and PHOENICS, in which the eddy break-up and k–ε–g turbulent combustion models have been, respectively, implemented.     

建筑火灾过程中烟气与热排放作用分析

分析了建筑火灾过程中烟气与热排放的目的，我国相关技术规范与欧共体及德国标准相比的不足之处，在此基础上系统地介绍了烟气与热排放的工程方法及烟气与热排放的计算方法，并通过工程实例分析了烟气与热排放的作用效果。     

水喷雾系统抑制电动汽车火灾有效性实验研究

为解决现有消防手段难以有效扑灭电动汽车火灾的问题,设计了水喷雾隔热阻火系统和拖车式车载水喷雾灭火降温系统.对模拟电动汽车火灾进行灭火有效性全尺度实验.结果表明,在现有工况条件下,水喷雾隔热阻火系统能有效抑制车辆底盘的射流火焰,可防止火灾向相邻车辆蔓延,但受安装位置限制,该系统对驾驶舱内部火焰的抑制和降温效果较差,灭火后...     

Energy release rates in fire retardant evaluation

Rate of spread and other indirect measurements of fire intensity are often used as measures of flammability when fire-retardant chemicals are evaluated under laboratory conditions. The authors describe a system for obtaining the energy release rate directly and show its importance and relation to retardant effectiveness. Note: The authors are Research Foresters stationed at the Northern Forest Fire Laboratory, Missoula, Montana.     

Heat of combustion in spreading wood crib fires with application to ceiling jets

Responding to a challenge raised with respect to a 1989 revision of a 1979 paper on the ceiling jet of t-squared fires, we have measured the heat of combustion in the growth phase of wood cribs made of sugar pine, the test fuel in the original work, needed to generalize the ceiling jet measurements to any combustible. The present determination of the chemical heat of combustion in the growth phase, 14.1 kJ/g, is a little higher than adopted in 1989 (12.5 kJ/g, from wood sample burning with diffusion flame) but still considerably lower than employed in 1979 (20.9 kJ/g, from oxygen bomb calorimetry). More importantly, the convective heat of combustion was measured as 11.5 kJ/g, which has been employed to update the ceiling jet equations for temperature and velocity in t-squared fires. An explanation is offered for the varying, and often higher than expected ceiling-level temperatures measured with thermocouples directly over the fire in the original experiments, suggesting that both plume lean and thermocouple insertion depth may have affected the indicated temperature.     

Effects of a transverse external wind on natural ventilation during fires in shallow urban road tunnels with roof openings

Fire experiments using a 1:12 scale model tunnel were conducted to evaluate effects of a transverse external wind on the performance of roof openings in a shallow urban road tunnel under fire conditions. A particular focus was placed on clarifying the characteristics of the spread of smoke in the tunnel under the condition of a transverse external wind blowing above the roof openings. Two types of median barriers, pillars and walls, were examined as dividing structures in the model tunnel, and the heat release rate was selected as the experimental parameter. The following conclusions were obtained. Compared to conditions with no external transverse wind, in the model tunnel with the pillar median structure, the smoke spreading distance was shortened when the transverse external wind was in the positive direction, and the distance remained the same when the wind was in the negative direction; in the model tunnel with the wall median structure, the smoke spreading distance was shortened when the wind was in the positive direction. Furthermore, the smoke spreading distance in each case was constant and independent of the heat release rate of the fire under the scope of the experimental conditions used in this study.     

重质油罐火灾热波传播及影响因素研究

重质油罐燃烧易发生油品的沸溢喷溅灾难性现象。热层及其热波的传播是沸溢喷溅最重要的条件之一。对原油和重质馏分油的热波特性进行了实验研究，建立了热波传播数学模型并讨论了各个因素的影响。