| 1. |
- Tuovinen, Heimo
(författare)
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Simulation of Combustion and Fire-Induced Flows in Enclosures
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Numerical modeling of combustion in flames and gas flows and gas flows generated by fires in compartments has been carried out. The laminar flamelet model has been used to model combustion in different degrees of vitiation in order to model fire gas recirculation which occurs in compartment fires. CFD modeling (computational fluid dynamics) has been used in the calculation of the flow field. The flamelet calculations were carried out using a modified version of the Cranfield SNECKS code and CFD calculations using the Fire Research Station’s JASMINE code. The results from both flamelet and CFD calculations agree reasonably with experimental results. Generally, the deviations from laboratory measurements are less than 30%, which is not greater than the errors expected in the measurements.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Plos, Mario, 1963, et al.
(författare)
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Nonlinear FE Analyses of RC Bridge Frame Corners, Based on Fracture Mechanics
- 1998
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Ingår i: Journal of Bridge Engineering. - 1084-0702. ; 3:4, s. 204-209
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Tidskriftsartikel (refereegranskat)abstract
- Reinforced concrete frame corners were analyzed using the nonlinear finite-element method and fracture mechanics. The objective of the study was to determine whether the reinforcement detailing in frame bridges could be simplified, with preserved structural safety, by splicing the reinforcement within the frame corner. A constitutive model for concrete, based on nonlinear fracture mechanics and plasticity, was used. An interface model was used to account for slip between the reinforcement and surrounding concrete. Analysis of previously tested frame specimens, with both spliced and unspliced corner reinforcement, was used to study the overall behavior of the frames; more detailed analysis of only the frame corner regions was used to study the influence of the reinforcement splices. The analyses were found to reflect the mechanical behavior of the specimens, and are in good agreement with the test results. The analysis results support, together with the test results, the idea that it would be feasible to splice all reinforcement in a portal frame bridge within the corner regions.
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| 7. |
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| 8. |
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| 9. |
- Andersson, Berit, et al.
(författare)
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Combustion of Chemical Substances and the Impact on the Environment of the Fire Products: 1/3 Scale Room Furnace Experiments
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes the results obtained from fire tests in a 1/3-scale room. The aim of the study was to investigate how changes in external radiation and oxygen supply affect the production of smoke and toxic gases. The ventilation was varied to simulate under- and well-ventilated fires. The thermal exposure to the materials was varied to simulate fires of different sizes. Fifty-nine tests were performed, with polystyrene, FR polystyrene, polypropylene, nylon and PVC. Measurements were made of the contents of O2, CO2, CO, NOx, and HC in the exhaust gases. The impact of external radiation was mainly to increase the pyrolysis rate, and thus the rate of heat release, and to drive the fire into under-ventilation. The degree of ventilation proved to have the greatest impact on the combustion efficiency. The smoke production was almost constant for polypropylene and nylon. The CO production appeared to be the most complex of the parameters to describe, and the expected increase in CO yield at low yields of CO2 could not be seen. The generation of NOx was low for the two substances without chemically bound nitrogen, but for nylon, the generation was significant. The production of low molecular weight HC was essentially constant for all three materials. Almost all the carbon was recovered in wellventilated fires, but at under-ventilated conditions, only 30% of the carbon from the he1 was detected. The toxic potency of the exhaust gases was estimated using the N-gas model, and proved to be relatively low. Lack of oxygen and the production of carbon oxide had the greatest impact on the toxicity for polystyrene and polypropylene, while NO, represented the main part for nylon. The survival fraction and the decomposition products from the original materials are not considered in the model. It can therefore not be assumed that the model reflects all aspects of the toxicity problem.
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| 10. |
- Andersson, Berit
(författare)
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Introduktion till konsekvensberäkningar. Några förenklade typfall
- 1992
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I dagens samhälle krävs i många fall genomförande av risk- och/eller konsekvensanalyser. Krav ställs dels från myndigheter och dels inom enskilda företag och organisationer. Här kommer endast konsekvensanalyser att behandlas. Anledningen till att genomföra en konsekvensanalys kan skifta. Som nämnts kan krav på en konsekvensalanys komma utifrån från myndigheter och dels kan en analys utföras för att ge ett företag underlag för åtgärdsplanering. Att göra en inventering av vilka risker som finns inom företaget och vilka konsekvenser dessa kan ge upphov till är ofta mycket lärorikt. Syftet med här nedan redovisat arbete är att på svenska ge en sammanställning över beräkningsmetoder som kan användas vid en konsekvensanalys för att göra uppskattningar med hjälp av handräkningsmetoder. I många fall är det tillräckligt att göra denna typ av beräkningar för att gå en uppfattning om storleken på konsekvenserna av ett oplanerat utsläpp. Vid omfattande analyser är det till stor hjälp att ha tillgång till något av de datorprogram för konsekvensberäkningar som finns på marknaden. Handräkningsmetoderna kan då utnyttjas som enkla kontrollinstrument av att man gett rätt indata till de beräkningsmodeller som finns i datorprogrammet. Exakt överensstämmelse får man naturligtvis inte mellan resultaten men en storleksjämförelse är ändå viktig. Sammanställningen innehåller material från ett antal, inom området, välkända referenser. Uppläggningen har gjorts så att i de fall materialet hämtats från orginalreferensen så anges denna i annat fall hänvisas till de generella referenser som finns angivna i referenslistan. Härledningar har genomgående utelämnats och för studier av dessa hänvisas till de generella referenserna. Det redovisade arbetet initierades av Länsstyrelsen i Malmöhus län av det under 1989 pågående RAM-projektet (Risk-Analys-Malmöhus-län). Delvis har arbetet utförst inom detta projekt och även till en del finansierats av RAM-projektet.
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| 11. |
- Andersson, Berit, et al.
(författare)
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Manual till datorprogrammet GASOL
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Gasol är ett användarvänligt PC-baserat datorprogram i Windowsmiljö. Programmet är specifikt utformat för simuleringar av utsläpp av gasol. Gasol är utvecklat på Brandteknik vid Lunds Universitet på uppdrag av Statens Räddningsverk. Gasol är ett vanligt bränsle i Sverige och användningen ökar. Både större och mindre olyckor har inträffat efter vådautsläpp av gasol. För att göra erforderliga riskanalyser av gasol-anläggningar är det nödvändigt att kunna göra konsekvensbedömningar för olika typer av oplanerade gasolutsläpp. Syftet med Gasol är att tillhandahålla ett såväl kraftfullt som användarvänligt datorprogram för konsekvensberäkningar. Programmet skall kunna beskriva spridningsbild och koncentrationer i luften vid utsläpp från tankar och rör av varierande utformning, ange värmestrålning på olika avstånd från ett antänt utsläpp samt avgiven strålning och alstrat tryck vid explosion i ett gasmoln eller vid ett tankhaveri. I indata ska hänsyn kunna tas till rådande väder- och vindförhållanden, topografi, bebyggelse och växtlighet samt till parametrar som är förknippade med utsläppskällan. Utdata skall presenteras i grafisk och tabellform. Gasol skall kunna användas av dem som arbetar med att ta fram konsekvensbedömningar för anläggningar och installationer där gasol utnyttjas som energikälla eller installationer för lagring av gasol. Programmet är främst avsett att utnyttjas inom räddningskårerna i Sverige och därför finns program och manual endast på svenska.
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| 12. |
- Andersson, Berit, et al.
(författare)
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Naturgas Säkerhetsnivå Riskanalys
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport har tillkommit på uppdrag av NUTEK och avser att belysa riskerna med distribution och industriell användning av naturgas. Tidigare har en rapport avseende naturgasinstallationer i hemmen utgetts [1,2]. Rapporten inleds med en allmän diskussion om risker. Vidare tas frågan om lagstiftning, tillsyn, kontroll och utbildning för naturgasanvändning i olika lander upp. Dessutom har en retrospektiv sökning efter statistik om naturgasolyckor samt incidenter gjorts. En kort genomgång av hur man beräknar konsekvenser av naturgasutsläpp görs också.
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| 13. |
- Andersson, Berit, et al.
(författare)
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Simulated Fires in Substances of Pesticide Type
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In order to characterise fires in chemical warehouses, 38 medium scale experiments have been conducted. The experiments were performed in a 0.66m3 combustion chamber. On-line measurements were made of combustion gases (CO2, CO, HC and NOx), mass loss, smoke, temperatures, external radiation and phi-values. Intermittently gas and soot samples were collected and analysed for content of organic compounds and amount of soot produced. Main variables during the experiments were external radiation, fire diameter, opening configuration and ventilation condition. The medium scale was chosen in order to give a test method which is more convenient to work with, less expensive than full-scale experiments and still rather well simulates the conditions in a real fire.
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| 14. |
- Andersson, Petra, et al.
(författare)
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An instrument for determining the total water content in air when extinguishing fires
- 1999
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Ingår i: Fire and Materials. - 1099-1018. ; 23:4, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- n instrument suitable for measuring the total water content both as small liquid droplets and as vapour in the air, in water mist total flooding extinguishing tests, is presented. The instrument consists of a heater and a Vaisala humidity meter. The Vaisala humidity meter is capable of measuring relative humidity at temperatures up to 180°C. The instrument has a measuring range of 0-600g/m3, a sample rate of 1 L/min, a time constant of 5-10 s and an accuracy of ±40 g/m3. Accurate results are obtained when used outside the direct spray from a nozzle. If the instrument is placed in the spray the total water content can be either over- or underdetermined, depending on which part of the instrument faces the spray.
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| 15. |
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| 16. |
- Andersson, Petra
(författare)
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Evaluation and Mitigation of Industrial Fire Hazards
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A tool suitable for conducting industrial fire and explosion hazard analysis is presented, together with an identification of weak links in the hazard evaluation chain. For some of the weak links additional research has been carried out. The tool, "FREIA", evaluates the consequences for humans and components due to fires and accidental releases indoors and outdoors using established engineering methods. Investigations have been carried out to find possible methods to simulate detector activation. The temperature, velocity, soot, CO2, CO and oxygen concentration were determined in the plume above a fire. Close agreement was found between the different compound fields. A CFD simulation of the same plume closely matched the experiments. However, there are large uncertainties involved when transforming light attenuation measurements into soot volume fraction. Simulations of tests according to the EN54 detector standard were also carried out. The agreement differed for different fuels. In addition, there is a problem with comparing light attenuation measurement performed at different wavelengths. All the results obtained indicate that it is possible to model smoke detector activation by treating the soot as an inert gas, or by assuming the soot concentration closely corresponds to one of the other compound fields. Heat detector activation is not as complicated to simulate. The phasing out of halons often demands new solutions in order to maintain the given protection level. More recently water mist has been mentioned as a possible replacement for halons. Experiments together with theoretical considerations have shown that no presently available water mist system fulfils the requirements of a total flooding system. A narrow window exists, however, in which a water mist can function as a total flooding system. Several halon-like agents have been developed. These, however, produce more thermal decomposition products than halons, the amount produced was found to be proportional to the amount of fuel burnt in the presence of the agent. In addition, experiments have shown that they can actually increase the fire instead of extinguishing it, if not properly designed. Estimating human burns is difficult; a test dummy for such measurements is presented.
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| 17. |
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| 18. |
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| 19. |
- Andersson, Petra, et al.
(författare)
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Limitations of Water Mist as a Total Flooding Agent
- 1998
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Ingår i: Journal of Fire Protection Engineering. - : SAGE Publications. - 1042-3915. ; 9:4, s. 31-50
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Tidskriftsartikel (refereegranskat)abstract
- The limitations of water mist in acting as a total flooding agent are discussed in this paper. The paper focuses on water mist consisting of droplets 1-100 µm in diameter. Water mists are very efficient as an extinguishing media if they are present in the flame. There are, however, several problems associated with introducing the water mist into the flame: the spray reaches only a short distance; small water droplets have a very short lifetime; droplets coagulate into larger droplets; large droplets hit obstacles such as walls and therefore have difficulties in being dispersed throughout the protected volume.
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| 20. |
- Andersson, Petra, et al.
(författare)
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Small scale experiments and theoretical aspects of flame extinguishment with water mist
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The present study focuses on extinction of flames with water mist where surface cooling effects are neglected i.e. water mist as a total flooding system where the direct spray cannot reach and cool all burning items in the protected volume. The study includes a survey of the production and properties of water mist such as different types of nozzles and means to describe droplet size distribution. Properties of jets and sprays are discussed as well as water droplet movement, fall and evaporation. Three different series of experiments were conducted with different hydraulic atomising nozzles. In the first series, droplet size distribution and water spray distribution measurements for the nozzles were conducted. The measurements showed that the droplet size distribution ranged from a Sauter Mean Diameter of approximately 35 - 85 µm, all dependent on the water pressure and the configuration of nozzles. The measurements show that considerably larger droplets are formed when individual nozzles are placed together. This can be explained by a coalescence effect when droplets from the sprays of the nozzles collide. The second series of experiments were done using a tubular propane gas bumer where water and propane were mixed prior to reaching the burner outlet. Based on the tests, the specific amount of extinguishing medium required (Required Extinguishing Medium Portion, REMP = m, / m, i.e. the ratio of the agent quantity to fuel quantity consumed) is given as a quantitative measure of the efficiency of the agent. The lower the REMP value, the more efficient the agent. The water pressure ranged between 40 and 80 bar which provided for droplet sizes with a Sauter Mean Diameter in the order of 35 pm. The results show that the amount of water needed for extinguishment by weight is between 1.2 - 2,2 times the amount of propane gas. The decrease in droplet sizes decreased the amount of water needed. Another observation was that the heat release rate of the fire is not affected until extinction occurs. A REMP-value of 1,2 - 2,2 corresponds to a water content of 100 – 200 g/m3 protected volume which is in agreement with theoretical values. Finally, a series of tests were conducted in a 113 scale room using a propane gas fire. Parameters such as location of the fire, the location of the nozzle, water flow rate and the size of the room opening were varied. In these tests the water content needed was in close agreement with the values obtained from the REh4P experiments and the theoretical values. These tests also highlighted the problem of delivering the droplets to the fire. To achieve "total flooding" in an actual situation, nozzles covering the complete protected compartment, with additional nozzles under obstructions would be needed. To make droplets follow the air flows inside a room and behave more like a gaseous total flooding agent, requires droplets of a size in the order of 1 - 20 µm.
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| 21. |
- Bengtsson, Lars-Göran
(författare)
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Övertändning, backdraft och brandgasexplosion sett ur räddningstjänstens perspektiv
- 1999
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This report presents a detailed description of the phenomena flashover, backdraft and smoke gas explosion. The physical and chemical processes which are involved in these phenomena are thoroughly discussed. The report also describes a number of compartment fire scenarios which are believed to be the most common scenarios occurring in Sweden. The description is based on a number of full- scale experiments which were carried out within the project. At the end of the report, possible warning signs of a potential flashover and backdraft are discussed. In the appendices, a number of models used to predict flashover are evaluated, using data from small scale experiments carried out within the project.
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| 22. |
- Benthorn, Lars, et al.
(författare)
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Fire alarm in a public building : how do people evaluate information and choose evacuation exit?
- 1999
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Ingår i: Fire and Materials. - 1099-1018. ; 23:6, s. 311-315
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Tidskriftsartikel (refereegranskat)abstract
- How people react to a fire alarm has been studied in retrospect as well as in experiments. In the present study, the choice of exit was examined with respect to the distance to exits and open or closed emergency exit. The second part deals with some communication aspects regarding identification of signs. It is shown that the subjects prefer a familiar ordinary cash exit even if the distance to that exit is longer than to the nearest emergency exit. However, if the emergency exit is open and the subjects can see the outside, an emergency exit becomes more attractive and most of the subjects choose the emergency exit. The understanding of signs important in a fire evacuation situation is very good. Copyright © 1999 John Wiley & Sons, Ltd.
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| 23. |
- Benthorn, Lars, et al.
(författare)
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Fire alarm in a public building: How do people evaluate information and choose evacuation exit?
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- How people react on fire alarm have been studied in retrospect as well as in experiments. In the present study, the choice of exit was examined with respect to the distance to exits and open or closed emergency exit. The second part covers the question on how the subjects think and react in a situation having a small fire in the escape route. The third part deals with some communication aspects regarding identification of signs. It is shown that the subjects prefer a familiar ordinary cash exit even if the distance is longer to that exit than to the nearest emergency exit. However, if the emergency exit is open and the subjects can see the outside, the attractiveness becomes much higher for the emergency exit and most of the subjects choose the emergency exit. The identification of alarm using a ring signal perceives often as a general warning or some kind of a conventional ring-signal such as telephone or school ring signal, and it is more seldom perceived as an evacuation signal. A spoken message, on the other hand, has a great impact on understanding what to do and gives a better and more appropriate behaviour for the evacuation of the building. The understanding of signs, important in a fire evacuation situation, is very good for signs such as emergency exit but rather low for signs not so frequently used, such as a sign for radioactive material.
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| 24. |
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| 25. |
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