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Chapter 7 Compartment Fire

Chapter 7 Compartment Fire. Lesson 1 Development of Compartment Fire. Key Words & Phrases. Compartment fire 室内火灾 Flashover 轰燃 Pre-flashover 轰燃前 post-flashover 轰燃后

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Chapter 7 Compartment Fire

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  1. Chapter 7 Compartment Fire Lesson 1 Development of Compartment Fire

  2. Key Words & Phrases Compartment fire 室内火灾 Flashover 轰燃 Pre-flashover 轰燃前 post-flashover 轰燃后 Flammable (Flame) 可燃的 Combustible (combustion) 可燃的 Smoulder 阴燃、无焰燃烧 Smouldering fire 阴燃 Glowing fire 无焰燃烧 Flaming fire 有焰燃烧

  3. Key Words & Phrases Ventilate (ventilation) 通风 Ventilation Factor 通风因子 Opening Factor 开口因子

  4. 1.Definition of compartment fire Fires happen in a room, a bus, a car, a ship or train compartment, etc. are all compartment fires. A compartment fire is a fire that takes place in a compartment, such as a room, a bus or a train compartement. A compartment fire (室内火灾) means a fire that takes place in a compartment. A compartment is an enclosure with walls, roof and openings (such as windows and doors).

  5. WTC 911

  6. The big Garley building fire ,1996, Hongkong Airport terminal fire, 1996, Duesseldorf, Germany

  7. MTR train compartment arson fire（纵火）, January 2004 (up) Ship fire: The fire broke out an hour after the ship left the port of Miami(Right)

  8. Bus fires: Burnt to the top within 10 min Burnt completely within 10 min

  9. 2. Why compartment fires present added danger? Compartment fires are quite different from those fires burning in the open air because of the walls and ceiling. When a fire occurs in free space, heat and smoke generated would be lost to the ambient (环境) rapidly. But for a compartment fire, most of the heat and smoke generated would be confined in the upper part of the compartment.

  10. Outdoors, fire grows steadily. Indoors, trapped heat and smoke cause temperature to suddenly go up.

  11. 3. Ignition (点燃) of a Compartment Fire For ignition of a fire to occur, a fuel must be heated above its ignition temperature (燃点) in the presence of sufficient oxidizer（氧化剂）for a fire to occur. An ignition source is anything which can heat even a small portion of a fuel to its ignition temperature.

  12. 3. Ignition (点燃) of a Compartment Fire 3. Development of a Compartment Fire After ignition three kinds of fires may follow: Smouldering Fires Glowing Fires Flaming Fires 3.1 Smouldering Fires A fire in solid fuel which is heat-limited (energy-limited) or ventilation limited will smoulder.

  13. A Heat-limited Smouldering Fire

  14. A Ventilation-limited Smouldering Fire

  15. Fate of a Smouldering Fire • The smouldering fire may eventually gain enough heat (through reflected radiation or enhanced ventilation) to burst into flames; • Alternatively, the fire may self-extinguish due to radiant heat loss or lack of fuel or oxygen.

  16. After Ignition Three Kinds of Fires May Follow: 3.2 Glowing Fires Glowing combustion is associated with the surface oxidation of carbonaceous (碳的、含碳的) materials or char. Glowing combustion differs from smouldering only in that thermal degradation of the parent fuel does not occur.

  17. A Glowing Fire

  18. Fate of a Glowing Fire: Glowing fire is normally of short duration and is apt to self-extinguish.

  19. After Ignition Three Kinds of Fires May Follow: 3.3 Flaming Fires A flaming fire may develop immediately after ignition, particularly in cases of arson (纵火), or may develop from a smouldering fire after a delay which may be hours.

  20. A Flaming Fire

  21. Fate of a Flaming Fire: • The fire burn itself out without involving other items of combustible material; • If there is enough fuel but inadequate ventilation, the fire may self-extinguish or continue to burn at a very slow rate dictated by the availability of oxygen; • If there is sufficient fuel and ventilation, the fire may progress to full room involvement in which all exposed combustible surfaces are burning.

  22. Temperature Time 4. Development of a compartment fire Flashover轰燃 Decay 衰减阶段 Fully developed stage (post-flashover) 充分发展阶段 Growth stage (pre-flashover)初期增长阶段

  23. 4.1 Growth stage (Pre-flashover) • (1) Average temperature is low. • (2) Fire localization is small. In the growth or pre-flashover stage, the average compartment temperature is relatively low and the fire is localized in the vicinity of its origin.

  24. 4.2 Fully developed stage (post-flashover) • (1) Average temperature is high. • (2) The whole compartment is in fire. In the fully developed or post-flashover fire, all combustible items are on fire. Flames appear to fill the whole compartment and emerge from the windows and other ventilation (通风) openings. This may continue until the available fuel is consumed.

  25. 4.2 Fully developed stage (post-flashover)

  26. 4.3 Decay Stage • Average T ≤ 80%Tmax The decay period is often identified as the stage of fire after the average temperature has fallen to 80% of its peak value. At this stage, fire becomes smaller and temperature drops lower due to the consumption of fuel.

  27. 4.4 Flashover Transition Growth stage Fully developed stage Flashover The transition(转变) is very short. So flashover is considered as an event not a stage. Temperature will increase quickly. Temperature can reach as high as 1000℃. During flashover, flames will spread rapidly from the area of localized burning to all the combustible surfaces within the room.

  28. Once flashover has occurred in one compartment, it’s hardly for the occupants of the rest of the building to evacuate (疏散). • The duration from onset of burning to flashover is directly relevant to life safety within a buiding.

  29. 5. The Necessary Condition for Safe Evacuation tp + ta+ trs≤ tu Where tp is the time elapsed from ignition to the perception (感觉) that a fire exists; ta is the time between perception to the start of the escape action; trs is the time taken to move to a place of relative safety; tu is the time (from ignition) for the fire to produce untenable (难以忍受的) conditions at the location.

  30. 6. Factors Affecting Fire Growth • The nature, amount and distribution of the combustible contents; • The size and shape the compartment; • The width and height of the ventilation openings.

  31. Burning rate (kg/min) Ventilation factor AH1/2(m5/2) Influences of Ventilation

  32. kg/min or kg/s Ventilation Factor Here AH1/2is calledventilation factor.

  33. Theoretical Deduction of the Ventilation Factor

  34. kg/min or kg/s Ventilation Factor

  35. Fuel Control Forms of a Compartment Fire Fuel-controlled （燃料控制） fire Ventilation-controlled （通风控制） fire Air (oxygen) Supply

  36. m/Af kg/m2s /AfKg/m2s

  37. Influence of Ventilation on the Control forms of fire Ventilation-controlled fire Fuel-controlled fire

  38. Opening Factor

  39. Opening Factor Opening factor: a measure of the rate of temperature rise of a fire, defined as the ratio of the ventilation factor and the total bounding area of an enclosure. Fuel-controlled fire Ventilation-controlled fire

  40. Fully-developed Decay Summary 1. Introduction of compartment fire. • 4. Factors Affecting Fire Growth (ventilation) 2. Explanation of why compartment fires are more dangerous than outdoor fires. 3. Ignition & development of a compartment fire. Flashover Growth

  41. Questions • Definition: Compartment fire; ventilation factor • Why indoor fires are more dangerous than outdoor fires? • How many stages are there in the development of a compartment fire? What are they and what are the characteristics of each stage? • What are the two control forms of the compartment fire? What is the difference between them?

  42. Chapter 8 Compartment Fire Lesson 2 Flashover

  43. Key Words & Phrases Flashover 轰燃 Fire plume 火羽 Heat flux 热通量 Pyrolyze (pyrolysis) 高温裂解 Radiation feedback heat辐射热反馈 Structural failure 结构破坏 Collapse 坍塌、倒塌 Hose-line 消防水带

  44. Temperature Time Development of a compartment fire Flashover轰燃 Decay period衰减阶段 Fully developed period (post-flashover) 充分发展阶段 Growth period (pre-flashover)初期增长阶段

  45. 1. Definition of Flashover • The term 'flashover' was first introduced by UK scientist P.H. Thomas in the 1960s and was used to describe the theory of a fire's growth up to the point where it became fully developed.

  46. Most commonly used Definitions of flashover are as follows: • The transition from a localized fire to the general conflagration (大火灾) within the compartment when all fuel surfaces are burning; • The transition from a fuel (燃料) controlled fire to a ventilation (通风) controlled fire; • The sudden propagation (传播) of flame through unburnt gases and vapors collected under the ceiling.

  47. Definition of Flashover Other Popular Definitions • The definition of flashover is given in a British Standard as a: "Sudden transition to a state of total surface involvement in a fire of combustible materials within a compartment".   (BS 4422, 1987) • The International Standards Organisation (ISO) use a similar wording: "The rapid transition to a state of total surface involvement in a fire of combustible materials within an enclosure".

  48. 2. Formation of flashover Initial development of a Fire Plume (火羽) in a Compartment.

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