scholarly journals Numerical Study on the Effect of Tunnel Aspect Ratio on Evacuation with Unsteady Heat Release Rate Due to Fire in the Case of Two Vehicles

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 133 ◽  
Author(s):  
Younggi Park ◽  
Youngman Lee ◽  
Junyoung Na ◽  
Hong Sun Ryou
Keyword(s):  
Aspect Ratio ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Numerical Study ◽  
Longitudinal Direction ◽  
Release Rates ◽  
Aspect Ratios ◽  
Visibility Distance ◽  
Computational Fluid Dynamics Analysis

In this study, the characteristics of fires in case of two vehicles in a tunnel are analyzed by Computational Fluid Dynamics analysis for varying tunnel aspect ratios. Unsteady heat release rates over time are set as the input conditions of fire sources considering real phenomena. Unsteady heat release rate values are obtained from experiments. As a result, the smoke velocities above the fire source appear faster in the case of tunnels with a large aspect ratio because the higher the height of the tunnel, the faster the smoke velocity caused by buoyancy forces. The smoke velocity in the longitudinal direction increases quickly. However, the temperature distribution in the vicinity of the ceiling is low when the tunnel aspect ratio is large because the height of the tunnel is not directly affected by the flames. Also, the higher the height of the tunnel, the lower the visibility distance due to the heat and smoke coming down along the wall surface. However, in the tunnels represented in this study, it is considered that the visibility of evacuees is sufficiently secured.

scholarly journals Numerical Study of the Effects of the Jet Fan Speed, Heat Release Rate and Aspect Ratio on Smoke Movement in Tunnel Fires

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1206
Author(s):  
Ha Thien Khieu ◽  
Young Man Lee ◽  
Ji Tae Kim ◽  
Hong Sun Ryou
Keyword(s):  
Aspect Ratio ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Numerical Study ◽  
Smoke Movement ◽  
Tunnel Fires ◽  
Jet Fan ◽  
Fan Speed ◽  
Set Up

In this study, the effects of the jet fan speed, heat release rate and aspect ratio on smoke movement in tunnel fires have been investigated. The jet fan speed was changed from 6.25 (25%) to 12.5 m/s (50%), 18.75 m/s (75%), and 25 m/s (100%). The heat release rate was set up from 3.9 to 6 MW and 16 MW, the aspect ratio was changed from 0.6 to 1 and 1.5, respectively. The lower the jet fan speed is, the longer the smoke back-layering length is. With a higher velocity, the smoke tends to move out of the tunnel quickly; however, smoke stratification also occurs, and this reduces visibility. This could make it difficult for people to evacuate. With a higher heat release rate, the smoke tends to move far away from the fires quickly when compared with other cases. Additionally, the higher the heat release is, the longer the smoke back-layering is. Finally, with a higher aspect ratio, the smoke back layering length in the tunnel is also longer. The smoke layer thickness is also larger than in other cases. The correlation of velocity, heat release rate and aspect ratio has been investigated to avoid the smoke back layer length in tunnel fires.

Influence of the Spatial and Temporal Interaction Between Diesel Pilot and Directly Injected Natural Gas Jet on Ignition and Combustion Characteristics

2017 ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Combustion Process ◽  
Gas Jet ◽  
Injection Timing ◽  
Release Rates ◽  
Temporal Interaction ◽  
The Impact

In this paper, pilot-ignited high pressure dual-fuel (HPDF) combustion of a natural gas jet is investigated on a fundamental basis by applying two separate single-hole injectors to a rapid compression expansion machine (RCEM). A Shadowgraphy system is used for optical observations, and the combustion progress is assessed in terms of heat release rates. The experiments focus on the combined influence of injection timing and geometrical jet arrangement on the jet interaction and the impact on the combustion process. In a first step, the operational range for successful pilot self-ignition and transition to natural gas jet combustion is determined, and the restricting phenomena are identified by analyzing the shadowgraph images. Within this range, the combustion process is assessed by evaluation of ignition delays and heat release rates. Strong interaction is found to delay or even prohibit pilot ignition, while it facilitates a fast and stable onset of the gas jet combustion. Furthermore, it is shown that the heat release rate is governed by the time of ignition with respect to the start of natural gas injection — as this parameter defines the level of premixing. Evaluation of the time of gas jet ignition within the operability map can therefore directly link a certain spatial and temporal interaction to the resulting heat release characteristics. It is finally shown that controlling the heat release rate through injection timing variation is limited for a certain angle between the two jets.

scholarly journals Effect of ratio between incoming cool air and outgoing hot gases on behaviour of compartment fire

2019 ◽  
pp. 326-326
Author(s):  
Olivier Zatao-Samedi ◽  
Abbo Oumarou ◽  
Jean M’Boliguipa ◽  
Mvogo Onguene ◽  
Ruben Mouangue
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Room Temperature ◽  
Data Acquisition System ◽  
Main Element ◽  
Compartment Fire ◽  
Release Rates ◽  
The Impact ◽  
Reduced Scale

Many factors have an influence on the development of compartment fire notably on its heat release rate as well as on its capability to propagate and become a flashover situation. The main element which rapidly conveys fire from a compartment to another is hot smoke flowing out through openings of the compartment source of fire. The present work aims to experiment the impact of the variation of heat release rate of the source on the behaviour of fire. So, five fire tests with different heat release rates were thus carried out in a reduced scale room. Temperature of burned gases inside the room, were measured during tests by sensors connected to a data acquisition system. Results revealed that temperature of burned gases as well as its content in carbon monoxide, evolves differently according to two ranges of the incoming air/outgoing gases ratio. The first range of which the ratio is lower than 2, corresponds to the case where both parameters decrease rapidly. The second range of which the ratio is higher than 2, corresponds to the case where both parameters decrease moderately. The transition from the first to the second range, points out the passing from the ventilation-controlled fire to the fuel-controlled fire. A relation expressing the variation of the mass flow rate of outgoing burned gases according to the heat release rate of the fire source has been given.

scholarly journals A Numerical Study on the Effect of Volume Change in a Closed Compartment on Maximum Heat Release Rate

2017 ◽  
Vol 31 (5) ◽  
pp. 19-27
Author(s):  
Hong-Seok Yun ◽  
◽  
Dong-Gun Nam ◽  
Cheol-Hong Hwang ◽  
◽  
...  
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Volume Change ◽  
Release Rate ◽  
Numerical Study ◽  
Maximum Heat ◽  
Maximum Heat Release

scholarly journals Characteristics of fire in high-speed train carriages

2019 ◽  
Vol 38 (1) ◽  
pp. 75-95
Author(s):  
Haiquan Bi ◽  
Yuanlong Zhou ◽  
Honglin Wang ◽  
Qilin Gou ◽  
Xiaoxia Liu
Keyword(s):  
Numerical Simulation ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Ignition Temperature ◽  
High Speed ◽  
Rapid Development ◽  
Longitudinal Direction ◽  
High Speed Train ◽  
Fire Source

With the rapid development of high-speed railways, safety hazards presented by train fires cannot be ignored. An effective design for protection against fire in high-speed trains is essential to ensure passenger safety. In this study, the cone calorimeter and ignition temperature tester were used to carry out combustion experiments on materials constituting the main components of the train. The heat release rate, smoke yield, CO yield, and ignition temperature of combustible materials were tested. Based on the experimental data of material combustion, a numerical model of the high-speed train carriage fire was simulated. The accuracy of the numerical simulation was verified by drawing a comparison with the full-scale train fire experiment in existing literature. The numerical simulation results revealed that when the fire source is present at the corner of the carriage end door, the fire develops to the maximum possible extent in approximately 25 min, with a peak heat release rate of approximately 38.4 MW. Increase in the carriage fire heat release rate and breakage of windows occur almost simultaneously. Improvement of the fireproof performance of windows can inhibit and delay the carriage fire development. For the flashover of carriage fire, the spread speed of the flashover area in the longitudinal direction inside the carriage is approximately 1.9 m/s. The end door area furthest from the fire source in the carriage has strong flashover, while the flashover in other areas is weak.

scholarly journals Use of the cone calorimeter to detect seasonal differences in selected combustion characteristics of ornamental vegetation

2005 ◽  
Vol 14 (3) ◽  
pp. 321 ◽  
Author(s):  
David R. Weise ◽  
Robert H. White ◽  
Frank C. Beall ◽  
Matt Etlinger
Keyword(s):  
Moisture Content ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Cone Calorimeter ◽  
Mass Loss Rate ◽  
Combustion Characteristics ◽  
Release Rates ◽  
Intermediate Scale ◽  
Time To Ignition

The flammability of living vegetation is influenced by a variety of factors, including moisture content, physical structure and chemical composition. The relative flammability of ornamental vegetation is of interest to homeowners seeking to make their homes ‘fire safe’. The relative importance of the factors influencing fire behaviour characteristics, such as flammability, is unknown. In the present study, oxygen consumption calorimetry was used to obtain selected combustion characteristics of ornamental vegetation. Peak heat release rate, mass loss rate, time to ignition and effective heat of combustion of 100 × 100-mm samples of foliage and small branches were measured using a bench-scale cone calorimeter. Green and oven-dry samples of 10 species were collected and tested seasonally for a period of 1 year. Similar measurements were made on whole shrubs in an intermediate-scale calorimeter. The range of cone calorimeter peak heat release rates for green and oven-dry samples was 1–176 and 49–331 kW m−2, respectively. Moisture content significantly reduced heat release rates and increased time to ignition. Peak heat release rates for Olea europea and Adenostoma fasciculatum were consistently highest over the year of testing; Aloe sp. consistently had the lowest heat release rate. The correlation of peak heat release rates measured by the cone calorimeter and an intermediate-scale calorimeter was statistically significant yet low (0.51). The use of the cone calorimeter as a tool to establish the relative flammability rating for landscape vegetation requires additional investigation.

Flame Retardancy of Laponite- and Montmorillonite-Based Nylon 6 Nanocomposites

2003 ◽  
Vol 788 ◽  
Author(s):  
Gunes Inan ◽  
Prabir K. Patra ◽  
Yong K. Kim ◽  
Steven B. Warner
Keyword(s):  
Mass Loss ◽  
Heat Release ◽  
Heating Rate ◽  
Heat Release Rate ◽  
Flame Retardancy ◽  
Release Rate ◽  
Barrier Properties ◽  
Nylon 6 ◽  
Release Rates ◽  
Peak Heat Release Rate

ABSTRACTThe flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.

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