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Ingason, H. & Li, Y. Z. (2019). Large scale tunnel fire tests with different types of large droplet fixed fire fighting systems. Fire safety journal, 107, 29-43
Open this publication in new window or tab >>Large scale tunnel fire tests with different types of large droplet fixed fire fighting systems
2019 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 107, p. 29-43Article in journal (Refereed) Published
Abstract [en]

The paper presented the main results of large-scale fire tests with different types of fixed firefighting systems (FFFS) conducted in the Runehamar tunnel in June 2016. The background to the tests, the performance of the different systems, and conclusions regarding the efficiency of the systems were presented. The fire load consisted of 420 standardised wooden pallets and a target of 21 wooden pallets. Five of the tests were carried out with a 30 m long deluge zone delivering varying water densities using three different types of side-wall nozzles with an interval distance of 5 m. One test with 93 °C glass-bulb automatic sprinklers in the same zone was also conducted. In the five deluge tests, the detection system was simulated using thermocouples in the tunnel ceiling. The alarm was registered when the ceiling gas temperature reached 141 °C, and the system was activated manually after a delay of 4 min. The protection goal of the system was to prevent fire spread to a target positioned 5 m from the rear of the main fuel area, and to ensure that the fire did not exceed 30 MW in size. The system setups tested were found to meet these goals.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Automatic sprinkler, Deluge, Fixed firefighting system (FFFS), Heat release rate, Water density, Wood pallets, Fire extinguishers, Fire protection, Hose, Pallets, Thermocouples, Heat Release Rate (HRR), Fires
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-39267 (URN)10.1016/j.firesaf.2019.04.007 (DOI)2-s2.0-85067036002 (Scopus ID)
Note

 Funding details: Trafikverket; Funding text 1: The project was financially supported by the Swedish Transport Administration (STA) which is gratefully acknowledged. We would like to thank tunnel safety officer Ulf Lundström of the STA, and Conny Becker of Brandskyddslaget AB. We would also like to thank all of the technicians at RISE Fire Research in Borås and RISE Fire Research A/S in Trondheim for their great work. Thanks also to Per Fiva of the Norwegian Public Road Administration in Åndalsnes for the technical support during the tests. The nozzles tested were provided by TYCO Fire Protection Products, who is gratefully acknowledged.

Available from: 2019-07-03 Created: 2019-07-03 Last updated: 2019-07-03Bibliographically approved
Yao, Y., Li, Y. Z., Ingason, H. & Cheng, X. (2019). Numerical study on overall smoke control using naturally ventilated shafts during fires in a road tunnel. International journal of thermal sciences, 140, 491-504
Open this publication in new window or tab >>Numerical study on overall smoke control using naturally ventilated shafts during fires in a road tunnel
2019 (English)In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 140, p. 491-504Article in journal (Refereed) Published
Abstract [en]

This paper studies the overall smoke control of natural ventilation systems with vertical shafts during fires in a common road tunnel by numerical modelling. The variables studied include the heat release rate, longitudinal fire location along the tunnel, length of shafts and the interval between two shafts. Simulation results indicate that the total smoke spread length on both sides of fire source is closely independent of the heat release rate and longitudinal fire locations. For a given dimensionless shaft interval (the ratio of the shaft interval to shaft length), with the increase of shaft length, the smoke spread length firstly increases, reaching a maximum at 12 m, and then decreases significantly until 18 m. For a fire less than 30 MW, the first shaft pair on both sides of fire source prevents the critical-temperature smoke (270 °C) from spreading beyond this shaft. For a 100 MW fire, in the cases with shorter shaft lengths (L shaft ≤9 m), the critical-temperature smoke can't be controlled between the first shaft pair. The gas temperature at human height (1.8 m) is less than 60 °C in all cases with shafts. Downdraught occurs when the smoke front stabilizes at the bottom of a shaft and the buoyancy force could be too low to overcome the kinetic pressure of the air flow flowing into this shaft, consequently destroying the structure of smoke layer. In most scenarios, the total exhaust area of shafts that is required to exhaust all the smoke is about 100 m 2 . The first shaft pair plays a critical role to exhaust the smoke, and its exhaust efficiency is also affected significantly by the shaft length. This study investigates how to control the smoke by using vertical shafts in a road tunnel fire and the conclusions are useful to tunnel fire protection engineering.

Keywords
CFD simulation, Natural ventilation, Smoke control, Tunnel fire, Vertical shaft, Computational fluid dynamics, Fire protection, Fires, Roads and streets, Smoke abatement, Temperature, Ventilation, CFD simulations, Tunnel fires, Smoke
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38255 (URN)10.1016/j.ijthermalsci.2019.03.016 (DOI)2-s2.0-85063353163 (Scopus ID)
Note

 Funding details: China Scholarship Council; Funding text 1: This project was financially supported by the Tunnel and Underground Safety Center (TUSC) . Besides, the authors would also like to acknowledge China Scholarship Council for providing Yongzheng Yao with the opportunity to study at RISE Research Institutes of Sweden.

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02Bibliographically approved
Zhao, S., Li, Y. Z., Kumm, M., Ingason, H. & Liu, F. (2019). Re-direction of smoke flow in inclined tunnel fires. Tunnelling and Underground Space Technology, 86, 113-127
Open this publication in new window or tab >>Re-direction of smoke flow in inclined tunnel fires
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2019 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 86, p. 113-127Article in journal (Refereed) Published
Abstract [en]

The re-direction of smoke flow in inclined tunnel fires refers to the phenomenon that the smoke flow direction suddenly changes due to the changes of thermal buoyancy or outside pressure or the activation of fans. This poses special risk for fire rescue services fighting fires in tunnels. Both small-scale tunnel fire tests (28 scenarios) and numerical simulations of full-scale tunnel fires (31 scenarios) were conducted to study this special phenomenon. A one-dimensional model was used to predict the flow velocity in the inclined tunnels, based on two different methods for calculating the mean smoke temperature (Method I and Method II, respectively). Results show that the smoke flow direction could be well predicted by the model with Method II. When the ventilation velocity is relatively large and the flow tends to be one dimensional, both methods produce similar results. Further, the influences of important factors on the re-direction of smoke flows were systematically analyzed. These factors include heat release rate, tunnel slope, tunnel length, friction factor, tunnel cross sectional area and fire source location.

Keywords
Re-direction, Slope, Smoke movement, Tunnel fires
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37695 (URN)10.1016/j.tust.2019.01.006 (DOI)2-s2.0-85060335729 (Scopus ID)
Note

 Funding details: China Scholarship Council, CSC; Funding text 1: The authors would like to acknowledge Tunnel and Underground Safety Center (TUSC) for the financial support to the study. Shengzhong Zhao was also financially supported by China Scholarship Council under Program for Ph.D Student Overseas Study Scholarship 2017. The authors would also like to acknowledge Eva-Sara Carlson and Anna Gidlöv for the help during the model scale tests.

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-02-01Bibliographically approved
Yao, Y., Li, Y. Z., Ingason, H. & Cheng, X. (2019). Scale effect of mass loss rates for pool fires in an open environment and in tunnels with wind. Fire safety journal, 105, 41-50
Open this publication in new window or tab >>Scale effect of mass loss rates for pool fires in an open environment and in tunnels with wind
2019 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 105, p. 41-50Article in journal (Refereed) Published
Abstract [en]

This paper investigates the influence of wind on mass loss rate per unit area (MLRPUA) of fuel-controlled pool fires both in an open environment and inside tunnels and the scale effect of pool fires is also investigated. Large pool fires with a diameter D greater than 1 m (D > 1 m) are of key concern but small pool fires (D < 1 m) are also considered for comparison. This is done by analyzing large amounts of experimental data from the literature. Results show that for small pool fires (D < 1 m) in an open environment, increasing wind speed tends to increase the MLRPUA, especially for pools with D < 0.2 m, where the MLRPUA could increase significantly with the increase of wind speed. But when small pool fires occur in tunnels, the results are more complex. When the ratio of effective tunnel height to pool diameter is less than 3, increasing wind speed tends to decrease the MLRPUA. When this ratio is greater than 3, the influence of wind on MLRPUA of pool fires in tunnels is similar to that in an open environment. The influence of wind on the MLRPUA decreases for larger pool diameters, no matter whether the pool fire occurs in an open environment or in a tunnel. For large pools with D > 1 m, the MLRPUA is not affected significantly by increasing wind speed and most likely varies within 30% for a wide range of wind speeds based on the test data collected. This influence is far less than the values concluded by previous studies based on small pool fire experiments. The outcome of this study contributes to improving the understanding of burning characteristics of pool fires under windy conditions, especially large pool fires, which are much more meaningful than small pool fires from the perspectives of fire protection engineering and fire hazard assessment.

Keywords
Heat feedback mechanism, Mass loss rate, Pool fire, Scale effect, Tunnel fire, Wind, Fire resistance, Fires, Lakes, Speed, Heat feedback, Pool fires, Scale effects, Tunnel fires, Fire protection
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38216 (URN)10.1016/j.firesaf.2019.02.004 (DOI)2-s2.0-85062285313 (Scopus ID)
Note

Funding details: China Scholarship Council; Funding text 1: This project was financially supported by the Tunnel and Underground Safety Center (TUSC) . The authors would also like to acknowledge the China Scholarship Council for providing Yongzheng Yao with the opportunity to study at RISE Research Institutes of Sweden. Thanks also to our colleague Dr Francine Amon at RISE for her valuable comments.

Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-04-02Bibliographically approved
Yao, Y., Li, Y. Z., Lönnermark, A., Ingason, H. & Cheng, X. (2019). Study of tunnel fires during construction using a model scale tunnel. Tunnelling and Underground Space Technology, 89, 50-67
Open this publication in new window or tab >>Study of tunnel fires during construction using a model scale tunnel
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2019 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 89, p. 50-67Article in journal (Refereed) Published
Abstract [en]

The paper presents a study on the characteristics of tunnel fires during construction. A model-scale tunnel was built and fire tests were conducted. The tunnel consists of an inclined access tunnel and a horizontal main tunnel. The main tunnel has two dead ends (excavation faces) and the only opening is from one side of the access tunnel. Propane gas burner and the fibre board soaked with the heptane were used as fuels. The flame characteristics, O 2 and CO volume fraction and gas temperature were measured and recorded. Two typical characteristics of self-extinguishment and smoke spread were found in the tunnel fires during construction. Results indicate that when a fire occurs in the horizontal main tunnel, the critical equivalence ratio for the occurrence of self-extinguishment is within 0.28–1.38 for the propane gas burner and 1.11–3.6 for the fibre board soaked with heptane. The difference is related to the burning behavior of the different fuels used. The fire location in the horizontal tunnel also has a significant influence on the fire development. A well-ventilated fire at the center of the horizontal tunnel becomes under-ventilated due to vitiation when it is located at the closed end of the horizontal tunnel. Besides, when a fire occurs at the closed end of the horizontal main tunnel, the stratification of smoke is destroyed after hitting the closed end, and then the smoke seems to spread over the entire cross section of the tunnel. The smoke spread velocity is found to be proportional to the ventilation rate. However, when a fire occurs at the closed end of the inclined access tunnel (lower end), the fire does not self-extinguish, even when the ventilation rate is 0 m 3 /s. The corresponding smoke spread velocity is higher than that in the horizontal main tunnel. The outcomes of this study provide new experimental information that contributes to improve the understanding of characteristics of tunnel fires during construction and can help firefighters to make better decisions during the rescue processes.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Equivalence ratio, Self-extinguishment, Smoke spread, Tunnel during construction, Tunnel fire, Under-ventilated, Fires, Gas burners, Heptane, Open access, Propane, Smoke, Ventilation, Equivalence ratios, Smoke spreads, Tunnel fires, Tunnels
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-38351 (URN)10.1016/j.tust.2019.03.017 (DOI)2-s2.0-85063487886 (Scopus ID)
Note

Funding details: China Scholarship Council; Funding details: Myndigheten för Samhällsskydd och Beredskap; Funding details: RISE; Funding text 1: This work was financially supported by the Swedish Civil Contingencies Agency (MSB) and the Tunnel and Underground Safety Center (TUSC) which are gratefully acknowledged. Thanks to the advisory group consisting of numerous representatives from industry and authorities for valuable comments and support. Thanks also to Jonatan Gehandler for the support and our technicians for technical assistance in carrying out the tests. Besides, the authors would also like to acknowledge China Scholarship Council for providing Yongzheng Yao with the opportunity to study at Research Institutes of Sweden (RISE).

Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-05-07Bibliographically approved
Yao, Y., Li, Y. Z., Ingason, H. & Cheng, X. (2019). The characteristics of under-ventilated pool fires in both model and medium-scale tunnels. Tunnelling and Underground Space Technology, 87, 27-40
Open this publication in new window or tab >>The characteristics of under-ventilated pool fires in both model and medium-scale tunnels
2019 (English)In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 87, p. 27-40Article in journal (Refereed) Published
Abstract [en]

This paper investigates the characteristics of under-ventilated fires in tunnels. This was done by using both model and medium-scale tunnels. The fuels used were heptane and xylene. The mass loss rates per unit area, ventilation rates from tunnel inlet, flame characteristics, O 2 , CO and CO 2 concentrations, optical densities and heat release rates were measured and recorded. Results show that the fire behaviors in under-ventilated tunnel fires are different from that in well-ventilated fires. In under-ventilated fires, the mass loss rate per unit area is found to decrease during identical periods due to the low oxygen concentration resulting from the low ventilation rate and vitiation, meanwhile the flame size dramatically reduces with a lifted and fluttering flame. This was clearly observed in model-scale tests, but due to limited optical view there was no possibility to observe this in the medium-scale tests. As a result, the ventilation rate approaches the amount required for complete combustion of vaporized fuel. This indicates that the combustion has converted from ventilation-controlled to fuel-controlled. No significant increase in CO production is observed in under-ventilated fires. Besides, the equivalence ratio and combustion efficiency were analyzed in order to judge whether the combustion is fuel-controlled or ventilation-controlled. This study provides new experimental information that contributes to improving the understanding of characteristics of under-ventilated fires in tunnel and can help firefighters to make right judgements and take related protective measures during the rescue processes.

Keywords
Equivalence ratio, Flame characteristics, Mass loss rate, Tunnel fire, Under-ventilated, Vitiation, Combustion, Fire resistance, Fires, Fuels, Equivalence ratios, Tunnel fires, Ventilation
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37864 (URN)10.1016/j.tust.2019.02.004 (DOI)2-s2.0-85061253858 (Scopus ID)
Note

 Funding details: China Scholarship Council, CSC; Funding text 1: This project was sponsored by the Swedish Fire Research Board (Brandforsk), the Swedish National Fire and Rescue Board (Räddningsverket) and the National Road Administration (Vägverket)

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-03-05Bibliographically approved
Li, Y. Z. & Ingason, H. (2018). Discussions on critical velocity and critical Froude number for smoke control in tunnels with longitudinal ventilation. Fire safety journal, 99, 22-26
Open this publication in new window or tab >>Discussions on critical velocity and critical Froude number for smoke control in tunnels with longitudinal ventilation
2018 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 99, p. 22-26Article in journal (Refereed) Published
Abstract [en]

Determination of critical velocity is a key issue for smoke control in any tunnel with longitudinal ventilation. The critical Froude model using single Froude number of 4.5 has for decades been widely used in engineering applications. This value was originally used by Danziger and Kennedy and they argued that the critical Froude number obtained by Lee et al. was in a range of 4.5 and 6.7 and therefore a conservative value of 4.5 was obtained. This paper explores the validity of using single critical Froude number of 4.5 by investigating the original sources and comparing it to recent research results. It was found that the value of 4.5 obtained in the original source corresponds to a large tunnel fire and it correlates well with data from other literature within a narrow range of large fire sizes. Using this value produces a significantly lower critical velocity for a wide range of fire sizes and therefore it is not conservative. The Froude number of 6.7 obtained by Lee et al. corresponds to another Froude number with a different definition and it is therefore not comparable with the value of 4.5. It is found that the use of a single value of 4.5 for the critical Froude number is not reasonable in calculation of the critical velocity for smoke control in tunnels with longitudinal ventilation.

Keywords
Critical Froude number, Critical velocity, Longitudinal ventilation, Tunnel fire, Fires, Froude number, Longitudinal control, Smoke, Smoke abatement, Velocity, Conservative value, Critical velocities, Engineering applications, Froude modeling, Lower critical, Recent researches, Tunnel fires, Ventilation
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-34305 (URN)10.1016/j.firesaf.2018.06.002 (DOI)2-s2.0-85049337369 (Scopus ID)
Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-08-24Bibliographically approved
Li, Y. Z. & Ingason, H. (2018). Influence of fire suppression on combustion products in tunnel fires. Fire safety journal, 97, 96-110
Open this publication in new window or tab >>Influence of fire suppression on combustion products in tunnel fires
2018 (English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 97, p. 96-110Article in journal (Refereed) Published
Abstract [en]

A series of model scale tunnel fire tests was carried out to investigate effects of the fire suppression system on production of key combustion products including CO and soot. The key parameters accounted for in the tests include fuel type, ventilation velocity and activation time. The results show that fire suppression indeed has influence on production of combustion products especially for cellulose fuels. In case that the fire is not effectively suppressed, e.g. when the water density is too low or activation is too late, the CO concentration and visibility could be worse than in the free-burn test. From the point of view of production of combustion products, only fire suppression systems with sufficient capability and early activation are recommended to be used in tunnels.

Keywords
Activation, CO yield, FED, Fire suppression, Soot yield, Tunnel fire, Ventilation, Visibility, Chemical activation, Combustion, Fire extinguishers, Flammability testing, Soot, CO concentrations, Combustion products, Fire suppression systems, Investigate effects, Model scale tunnels, Tunnel fires, Ventilation velocity, Fires
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-31173 (URN)10.1016/j.firesaf.2017.06.011 (DOI)2-s2.0-85024494074 (Scopus ID)
Available from: 2017-08-23 Created: 2017-08-23 Last updated: 2018-08-24Bibliographically approved
Li, Y. Z., Ingason, H. & Jiang, L. (2018). Influence of tunnel slope on smoke control.
Open this publication in new window or tab >>Influence of tunnel slope on smoke control
2018 (English)Report (Other academic)
Abstract [en]

The critical velocity and backlayering length in sloped tunnels are investigated by numerical simulations using FDS. Simulation in two full-scale tunnels, with negative slopes ranging up to -18 % and heat release rates from 5 to 100 MW were carried out.

The results show that NFPA 502 equation significantly overestimates the effect of negative slopes.

The equation proposed by Atkinson and Wu is found to be in closer agreement with the results. A simplified correlation, i.e. Eq. (12), is proposed and recommended for practical use.

The previous correlation for dimensionless backlayering length, Eq. (3), is valid for tunnels of various slopes and aspect ratios, and can be used for prediction of backlayering length.

Publisher
p. 22
Series
RISE Rapport ; 2018:50
Keywords
critical velocity, tunnels, sloped tunnel, FDS
National Category
Mechanical Engineering Fluid Mechanics and Acoustics Applied Mechanics
Identifiers
urn:nbn:se:ri:diva-36626 (URN)978-91-88695-92-5 (ISBN)
Note

In the previous version there were misprints that have been corrected in the present version. The report/full text has been updated 2019-04-23 according to following corrections:

Equation (8) was given for two equations. The equation number sequence after Equation (8) has been corrected as well as references in text and graphs (2,4 and 6) to the corresponding equations.

In the previous version, Equations (8) on page 9, Equation (9) on page 11, Equation (10) on page 12 and Equation (13) on page 15 there was a misprint in the exponents for the boundaries given; a negative sign has been changed to positive sign in these equations.

Available from: 2018-12-14 Created: 2018-12-14 Last updated: 2019-04-23Bibliographically approved
Li, Y. Z. & Ingason, H. (2018). Model scale tunnel fire tests on maximum ceiling gas temperature for structural protection.
Open this publication in new window or tab >>Model scale tunnel fire tests on maximum ceiling gas temperature for structural protection
2018 (English)Report (Other academic)
Abstract [en]

Model scale tests with varying materials as tunnel structure were carried out to further study the theoretical model of maximum gas temperature for structural protection. New correlation for calculation of air mass flow rate is introduced. Test results showed that the maximum ceiling gas temperatures increases with the increasing heat release rate and decreases with the increasing tunnel width and thermal inertia of the tunnel linings. Higher ventilation velocity may also result in slightly higher temperatures for large fires.

Comparisons of model scale tests and theoretical models showed that the theoretical models predict the maximum ceiling gas temperature very well. A fire with a fixed heat release rate or a time-varying heat release rate, the effects of tunnel structure, tunnel ventilation, tunnel width and fire size have been well considered by the model. Comparisons of other model and full scale tests with theoretical models further verified this.

Publisher
p. 36
Series
RISE Rapport ; 2018:58
Keywords
tunnel, fire, temperature, scale model, linings, ventilation
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36643 (URN)978-91-88907-02-8 (ISBN)
Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2018-12-19Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7744-2390

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