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On the Characteristics of Fires in Tunnels

Lönnermark, Anders LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

I avhandlingen presenteras viktiga fenomen i samband med bränder i tunnlar. Detta baseras både på experimentellt och teoretiskt arbete. Tyngdpunkten ligger på de brandförsök i fullskala som genomfördes 2003 i Runehamartunneln i Norge. Under dessa försök mättes brandeffektutvecklingen (HRR), temperaturer, gaskoncentrationer (O2, CO2, CO, HCN och H2O), gashastigheter, strålning och rök. Försöksuppställningen simulerade långtradarlaster och fyra försök genomfördes med olika blandningar av cellulosa och plast. Mängden bränsle i respektive försök varierade mellan 2850 kg och 11010 kg, vilket gav maximal effektutveckling mellan 66 MW och 202 MW.



Resultaten från försöken visade att... (More)
Popular Abstract in Swedish

I avhandlingen presenteras viktiga fenomen i samband med bränder i tunnlar. Detta baseras både på experimentellt och teoretiskt arbete. Tyngdpunkten ligger på de brandförsök i fullskala som genomfördes 2003 i Runehamartunneln i Norge. Under dessa försök mättes brandeffektutvecklingen (HRR), temperaturer, gaskoncentrationer (O2, CO2, CO, HCN och H2O), gashastigheter, strålning och rök. Försöksuppställningen simulerade långtradarlaster och fyra försök genomfördes med olika blandningar av cellulosa och plast. Mängden bränsle i respektive försök varierade mellan 2850 kg och 11010 kg, vilket gav maximal effektutveckling mellan 66 MW och 202 MW.



Resultaten från försöken visade att vanligt (ej definierat som farligt) gods kan ge brandeffekter och temperaturer, som hittills ansetts förknippade endast med farligt gods (t.ex. tankbilsbrand). Detta innebär att de högsta brandeffekterna och temperaturerna låg betydligt högre än vad som anges i olika riktlinjer och standarder. Ett nära samband identifierades mellan energiinnehåll och maximal brandeffekt för personbilar och långtradare. Det har också visats i Runehamarförsöken att en långtradarbrand kan sprida sig långa avstånd nedströms i tunnels, i storleksordningen 100 m. Baserat på resultaten från brandförsöken och verkliga bränder måste man understryka betydelsen av insatser under de första fem till tio minuterna av en brand i en tunnel. Åtgärder och handlande hos personer i tunneln under denna tidsperiod kan vara avgörande för utgången av branden.



Under två av brandförsöken i Runehamartunneln observerades stora pulsationer i gasflödet inne i tunneln. Dessa pulsationer registrerades endast när brandeffekten var högre än ungefär 125 - 135 MW. Två olika perioder mättes upp hos pulsationerna, en kortare på 4 s och en längre på 18 s. Pulsationerna presenteras och förklaras med hjälp av två olika angreppssätt: en akustisk analys och en frekvensresponsanalys baserad på impedanser. Dessa analyser visade att systemets resonansfrekvenser låg nära de uppmätta frekvenserna. Flera faktorer som kan påverka pulsationerna har identifierats, men beräkningarna visar att oscillationsperioderna är egenskaper hos systemet.



Andra fenomen som diskuteras är rök som transporteras uppströms (s.k. backlayering), ventilationens effekt på effektutvecklingen, flamlängder och förhållandena i tunneln. Data från litteraturen har, när det ansetts relevant, jämförts med resultaten från Runehamarförsöken. I denna analys har även toxicitet och ventilationens effekt på gassammansättningen inkluderats. Speciell uppmärksamhet gavs åt CO/CO2-kvoten och hur denna beror på ventilationen och förbränningsförhållandena. I detta sammanhang har resultat från en detaljerad studie av emissioner från rumsbränder och dess beroende av ventilationsförhållandena använts och legat till grund för en diskussion om ventilationens inverkan på toxiciteten och förhållandena i tunneln under en brand. (Less)
Abstract
Important phenomena related to tunnel fires are presented including both experimental and theoretical work. The main focus is on the large-scale fire tests performed in 2003, in the Runehamar tunnel in Norway. During these tests heat release rate (HRR), temperatures, gas concentrations (O2, CO2, CO, HCN, and H2O), velocities, radiation, and smoke were measured. Four tests with a set-up simulating HGV cargos were performed with fuel loads constituting of different mixtures of cellulose and plastic. The fuel load ranged from 2850 kg to 11010 kg giving maximum HRRs between 66 MW and 202 MW.



The results showed that ordinary (non-hazardous) cargo can give HRRs and temperatures normally expected to be related only to hazardous... (More)
Important phenomena related to tunnel fires are presented including both experimental and theoretical work. The main focus is on the large-scale fire tests performed in 2003, in the Runehamar tunnel in Norway. During these tests heat release rate (HRR), temperatures, gas concentrations (O2, CO2, CO, HCN, and H2O), velocities, radiation, and smoke were measured. Four tests with a set-up simulating HGV cargos were performed with fuel loads constituting of different mixtures of cellulose and plastic. The fuel load ranged from 2850 kg to 11010 kg giving maximum HRRs between 66 MW and 202 MW.



The results showed that ordinary (non-hazardous) cargo can give HRRs and temperatures normally expected to be related only to hazardous goods (e.g. tanker fires). Thus, the highest HRR and gas temperature were far higher than that suggested by most tunnel design guidelines. A close correlation between the maximum HRR and energy content is presented for passenger cars and HGVs. It has also been shown in the Runehamar tests that the fire in an HGV can spread a long distance downstream in a tunnel, of the order of 100 m. Based on the test results and real incidents one must emphasize the importance of the incident operation during the first five to ten minutes of the fire. The actions of the people inside the tunnel and the rescue personnel during this time period can be crucial to the outcome.



During two of the fire tests, large pulsations of the gas flow inside the tunnel were observed. These pulsations were registered only when the measured heat release rate was higher than 125 MW - 135 MW. Two different periods of pulsations were registered, short periods of approximately 4 s and longer periods of approximately 18 s. The pulsations are presented and explanations are given, using two different approaches: an acoustic approach and a frequency response analysis based on an impedance approach. The intrinsic resonances of the system proved to be close to the periods found in the experiments. Several factors can affect the pulsations, but the calculations show that the oscillation periods are properties of the system.



Other issues discussed include backlayering and the effect of the ventilation on the HRR, flame length, and the conditions in the tunnel. Literature data are, where relevant, compared with the results from the Runehamar tests. In this analysis toxicity and the effect of the ventilation conditions on the gas composition in the tunnel are also included. Special attention was paid to the CO/CO2 ratio and its dependence on the ventilation and combustion conditions. In this context results from a detailed study of the emissions from an enclosure fire under varied ventilation conditions are used as the basis for a discussion of the impact of ventilation on the acute toxicity of the fire gases. (Less)
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author
supervisor
opponent
  • Dr Beard, Alan N, Heriot-Watt University, UK
organization
publishing date
type
Thesis
publication status
published
subject
keywords
experiments, tunnel fire, heat release rate, temperature, fire spread, ventilation, backlayering, pulsations, thermoacoustic instability, equivalence ratio, emissions, gas concentrations, toxicity, Technological sciences, Teknik, Building construction, Byggnadsteknik, Road transport technology, Vägtransportteknik, Railway transport technology, Järnvägstransportteknik
pages
266 pages
publisher
Department of Fire Safety Engineering and Systems Safety, Lund University
defense location
Room V:A, V-building, John Eriksson väg 1, Lund Institute of Technology
defense date
2005-10-21 10:15
external identifiers
  • other:ISRN:LUTVDG/TVBB--1033-SE
ISSN
1402-3504
ISBN
91-628-6637-0
language
English
LU publication?
yes
id
cab7c7b4-8099-432c-90d3-40f64d42bf52 (old id 545453)
date added to LUP
2007-09-10 12:52:06
date last changed
2016-09-19 08:44:54
@phdthesis{cab7c7b4-8099-432c-90d3-40f64d42bf52,
  abstract     = {Important phenomena related to tunnel fires are presented including both experimental and theoretical work. The main focus is on the large-scale fire tests performed in 2003, in the Runehamar tunnel in Norway. During these tests heat release rate (HRR), temperatures, gas concentrations (O2, CO2, CO, HCN, and H2O), velocities, radiation, and smoke were measured. Four tests with a set-up simulating HGV cargos were performed with fuel loads constituting of different mixtures of cellulose and plastic. The fuel load ranged from 2850 kg to 11010 kg giving maximum HRRs between 66 MW and 202 MW.<br/><br>
<br/><br>
The results showed that ordinary (non-hazardous) cargo can give HRRs and temperatures normally expected to be related only to hazardous goods (e.g. tanker fires). Thus, the highest HRR and gas temperature were far higher than that suggested by most tunnel design guidelines. A close correlation between the maximum HRR and energy content is presented for passenger cars and HGVs. It has also been shown in the Runehamar tests that the fire in an HGV can spread a long distance downstream in a tunnel, of the order of 100 m. Based on the test results and real incidents one must emphasize the importance of the incident operation during the first five to ten minutes of the fire. The actions of the people inside the tunnel and the rescue personnel during this time period can be crucial to the outcome.<br/><br>
<br/><br>
During two of the fire tests, large pulsations of the gas flow inside the tunnel were observed. These pulsations were registered only when the measured heat release rate was higher than 125 MW - 135 MW. Two different periods of pulsations were registered, short periods of approximately 4 s and longer periods of approximately 18 s. The pulsations are presented and explanations are given, using two different approaches: an acoustic approach and a frequency response analysis based on an impedance approach. The intrinsic resonances of the system proved to be close to the periods found in the experiments. Several factors can affect the pulsations, but the calculations show that the oscillation periods are properties of the system.<br/><br>
<br/><br>
Other issues discussed include backlayering and the effect of the ventilation on the HRR, flame length, and the conditions in the tunnel. Literature data are, where relevant, compared with the results from the Runehamar tests. In this analysis toxicity and the effect of the ventilation conditions on the gas composition in the tunnel are also included. Special attention was paid to the CO/CO2 ratio and its dependence on the ventilation and combustion conditions. In this context results from a detailed study of the emissions from an enclosure fire under varied ventilation conditions are used as the basis for a discussion of the impact of ventilation on the acute toxicity of the fire gases.},
  author       = {Lönnermark, Anders},
  isbn         = {91-628-6637-0},
  issn         = {1402-3504},
  keyword      = {experiments,tunnel fire,heat release rate,temperature,fire spread,ventilation,backlayering,pulsations,thermoacoustic instability,equivalence ratio,emissions,gas concentrations,toxicity,Technological sciences,Teknik,Building construction,Byggnadsteknik,Road transport technology,Vägtransportteknik,Railway transport technology,Järnvägstransportteknik},
  language     = {eng},
  pages        = {266},
  publisher    = {Department of Fire Safety Engineering and Systems Safety, Lund University},
  school       = {Lund University},
  title        = {On the Characteristics of Fires in Tunnels},
  year         = {2005},
}