Scale Modeling on the Effect of Air Velocity on Heat Release Rate in Tunnel Fire

2008 ◽  
Vol 18 (2) ◽  
pp. 111-124 ◽  
Author(s):  
C. Chen ◽  
L. Qu ◽  
Y. X. Yang ◽  
G. Q. Kang ◽  
W. K. Chow
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Air Velocity ◽  
Tunnel Fire ◽  
Scale Modeling

Numerical Simulation and Analysis of Critical Velocity in Tunnel Fires Based on FDS

2013 ◽  
Vol 831 ◽  
pp. 455-459
Author(s):  
Shu Hui Xu ◽  
Ling Fei Cui ◽  
Lei Ning ◽  
Zi Ye Wang
Keyword(s):  
Heat Release ◽  
Critical Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Small Scale ◽  
Smoke Control ◽  
Tunnel Fires ◽  
Tunnel Fire ◽  
Velocity Prediction ◽  
The One

Critical velocity is a very important parameter in smoke control of tunnel fires and the variation of critical velocity against fire heat release rate is also one of the most important issues in tunnel fire researches. In this paper, a simplified physical model of a tunnel was established and the predictions of critical velocity for fire sizes in the 5-100MW range were carried out by FDS simulations. The FDS-predicted dimensionless critical velocities were compared with the values calculated by Wu and Bakar’s model. The result indicated that when the heat release rate was relatively small, Q≤30MW, the critical velocity increased with the increasing of heat release rate and varied as the one-third power of the heat release rate; when Q≥40MW, the growth rate of critical velocity became very small; after Q reach to 60MW, the critical velocity was almost unchanged with the increasing of heat release rate. In addition, the values of critical velocity calculated by Wu and Bakar’model which was derived from small-scale gas fire tests were underestimated. Therefore, the model suggested by Wu and Bakar is not suitable for critical velocity prediction in tunnel fires.

scholarly journals Numerical Investigation of Critical Velocity in Reduced Scale Tunnel Fire with Constant Heat Release Rate

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Ruben Mouangue ◽  
Philippe M. Onguene ◽  
Justin T. Zaida ◽  
Henri P. F. Ekobena
Keyword(s):  
Heat Release ◽  
Critical Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Combustion Products ◽  
Healthy Environment ◽  
Tunnel Fire ◽  
Air Supply ◽  
Minimum Velocity ◽  
Reduced Scale

When a fire occurs in a tunnel in the absence of sufficient air supply, large quantities of smoke are generated, filling the vehicles and any space available around them. Hot gases and smoke produced by fire form layers flowing towards extremities of the tunnel which may interfere with person’s evacuation and firefighter’s intervention. This paper carries out a numerical simulation of an unexpected fire occurring in a one-way tunnel in order to investigate for the critical velocity of the ventilation airflow; this one is defined as the minimum velocity able to maintain the combustion products in the downstream side of tunnel. The computation is performed successively with two types of fuels representing a large and a small heat release rate, owing to an open source CFD code called ISIS, which is specific to fires in confined and nonconfined environments. It is indicated that, after several computations of full-scale fires of 43.103 and 19.103 kJ/kg as heat release rate, the velocities satisfying the criterion of healthy environment in the upstream side of the tunnel are 1.34 m/s and 1.12 m/s, respectively.

Effects of ambient pressure on the critical velocity and back-layering length in longitudinal ventilated tunnel fire

2019 ◽  
Vol 29 (7) ◽  
pp. 1017-1027
Author(s):  
Guanfeng Yan ◽  
Mingnian Wang ◽  
Li Yu ◽  
Yuan Tian
Keyword(s):  
Heat Release ◽  
High Altitude ◽  
Critical Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Ambient Pressure ◽  
Smoke Movement ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
High Altitude Area

Nowadays, the critical velocity and back-layering length are the key parameters in longitudinal ventilation design. However, most studies research them at standard air pressure but ambient pressure decreases at high-altitude area and the reduced ambient pressure could affect the smoke movement characteristics in a tunnel fire. In order to investigate the effect of ambient pressure on the velocity and back-layering length in longitudinal ventilated tunnel, theoretical analysis was carried out first and a series of numerical simulation were conducted with varying heat release rate and ambient pressure. Results show that Li’s model is also reliable under various ambient pressures. The critical velocity under various ambient pressures would become larger with an increase in the heat release rate and would remain stable after the heat release rate reaches a certain value. At smaller heat release rate, the length of counterflow would be higher under reduced ambient pressure while it remains the same when the HRR is large. This could provide reference for tunnel ventilation design at high-altitude areas.

Numerical investigation on the smoke behaviour and longitudinal temperature decay in tilted tunnel fire with portal sealing

2021 ◽  
pp. 1420326X2110348
Author(s):  
Jiaxin Li ◽  
Yanfeng Li ◽  
Junmei Li ◽  
Quan Yang
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Temperature Rise ◽  
Ventilation System ◽  
Emergency Evacuation ◽  
Maximum Temperature ◽  
Tunnel Fire ◽  
Temperature Decay ◽  
Tunnel Portal

Blocking the tunnel portal is one strategy in railway tunnel firefighting. In order to evaluate the effect of tunnel portal sealing ratio on fire behaviour, Fire Dynamics Simulator (FDS) was used to simulate tilted tunnel fire with different slope angles varying from 0% to 5%, heat release rate varying from 10 to 50 MW and sealing ratios varying from 0% to 75%. Results show that the experimental data of the temperature distribution inside the tilted tunnel were in good agreement with the simulation results. Moreover, the ceiling temperature rise decreases along the tunnel with the increase of the tunnel portal sealing ratio at initial stage and then tends to stabilize because of less oxygen supply when the heat release rate is relatively large. The maximum temperature rise decays exponentially along the tunnel ceiling with distance. The current model for temperature decay beneath the tunnel ceiling was proposed to be modified by taking the tunnel entrance sealing ratio into account. The predictions by the modified model agree well with the experimental measurement. The results could provide practical information and knowledge in ventilation system design and emergency evacuation for inclined railway tunnels.

Study on real-time heat release rate inversion for dynamic reconstruction and visualization of tunnel fire scenarios

2022 ◽  
Vol 122 ◽  
pp. 104333
Author(s):  
Chao Guo ◽  
Qinghua Guo ◽  
Tong Zhang ◽  
Wei Li ◽  
Hehua Zhu ◽  
...  
Keyword(s):  
Heat Release ◽  
Real Time ◽  
Heat Release Rate ◽  
Release Rate ◽  
Dynamic Reconstruction ◽  
Tunnel Fire ◽  
Fire Scenarios

Experimental Studies on Heat Release Rate in Chinese Kitchen Fires

2011 ◽  
Vol 21 (4) ◽  
pp. 313-327 ◽  
Author(s):  
H. H. Wu ◽  
W. K. Chow
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Experimental Studies
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