【安全课件】第7章室内火灾简介.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,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,Flammable(Flame)可燃的,Combustible(combustion)可燃的,Smoulder 阴燃、无焰燃烧,Smouldering fire 无焰燃烧,Flaming fire 有焰燃烧,Ventilate(ventilation)通风,Ventilation Factor 通风因子,Opening Factor 开口因子,Key Words&Phrases,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,(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).,How does a flashover happen?,En France le Backdraft a tu cinq sapeurs pompiers de Paris en septembre 2002 alors quils intervennaient sur un feu de chambre de bonne,Flashover usually leads to tripled(三倍的)death in fire.,The height and width of the opening.,After the hose lines are charged with water and firefighters are in full protective equipment,the door or window is broken.,3)Sequences of flashover;,The building materials of the walls and ceiling.,That means we can change the material of its walls and ceiling.,What are the three firefighting tactics that can reduce destructive effects of a backdraft explosion?,Signal detector,Ventilation-controlled fire,Definition of Flashover,At a Window:,Fully developed stage,Formation of backdraft,(自燃点)for a certain mixture of flammable gases.,WTC 911,The big Garley building fire,1996,Hongkong,Airport terminal fire,1996,Duesseldorf,Germany,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),Bus fires:,Burnt to the top within 10 min,Burnt completely,within 10 min,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.,Outdoors,fire grows steadily.,Indoors,trapped,heat and smoke cause temperature to suddenly go up.,3.Ignition(点燃)of a Compartment Fire,For ignition of a fire to occur,a fuel must be heated above its,auto-ignition temperature,(自燃点),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 auto-ignition temperature.,Smouldering Fires,After ignition two kinds of fires may follow:,A fire in solid fuel which is heat-limited(energy-limited)or ventilation limited will smoulder.,3.Development of a Compartment Fire,3.Ignition(点燃)of a Compartment Fire,Flaming Fires,3.1 Smouldering Fires,A Heat-limited Smouldering Fire,A Ventilation-limited Smouldering Fire,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.,After Ignition Two Kinds of Fires May Follow:,3.2 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.,A Flaming Fire,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.,Temperature,Time,4.Development of a compartment fire,Flashover,轰燃,Growth stage,(pre-flashover),初期增长阶段,Fully developed stage,(post-flashover),充分发展阶段,Decay,衰减阶段,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.,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.,4.2 Fully developed stage(post-flashover),4.3 Decay Stage,Average T 80%T,max,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.,4.4 Flashover,Growth stage,Fully developed stage,Transition,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 combustible surfaces within the room.,Once flashover has occurred in one compartment,its 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 the buiding.,5.The Necessary Condition for Safe Evacuation,Where,t,p,is the time elapsed from ignition to the perception,(感觉),that a fire exists;,t,a,is the time between perception to the start of the escape action;,t,rs,is the time taken to move to a place of relative safety;,t,u,is the time(from ignition)for the fire to produce untenable,(难以忍受的),conditions at the location.,t,p,+,t,a,+,t,rs,t,u,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.,Influences of Ventilation,Ventilation factor AH,1/2,(m,5/2,),Burning rate(kg/min),Ventilation Factor,kg/min,kg/s,or,Here,AH,1/2,is called,ventilation factor,.,Theoretical Deduction of the Ventilation Factor,kg/min,kg/s,or,Ventilation Factor,Control Forms of a Compartment Fire,Fuel-controlled（燃料控制）fire,Ventilation-controlled（通风控制）fire,Fuel,Air(oxygen)Supply,/A,f,Kg/m,2,s,m/A,f,kg/m,2,s,Influence of Ventilation on the Control forms of fire,Fuel-controlled fire,Ventilation-controlled fire,The duration from onset of burning to flashover is directly relevant to life safety within the buiding.,Compartment fires are quite different from those fires burning in the open air because of the walls and ceiling.,Firefighters must be aware that the building could collapse at any point after a compartment reaches flashover.,Los Angeles,做时，你只能或者最好沿着以脚为起点的射线向前。,Fire plume 火羽,2 Great damage caused by flashover,You will probably see one at your next fire.,If these accumulate then the admission of air when an opening is made to the compartment can lead to a sudden deflagration.,Both the width and height of the door can be adjusted.,A second difference is that a backdraft is an explosion;a flashover is not.,22:01:0222:01:0222:0110/25/2022 10:01:02 PM,If these accumulate then the admission of air when an opening is made to the compartment can lead to a sudden deflagration.,Temperature will increase quickly.,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.,Opening Factor,Opening Factor,Fuel-controlled fire,Ventilation-controlled fire,Summary,4.Factors Affecting Fire Growth(ventilation),1.Introduction of compartment fire.,2.Explanation of why compartment fires are more dangerous than outdoor fires.,3.Ignition&development of a compartment fire.,Growth,Fully-developed,Decay,Flashover,Questions,What are the two control forms of the compartment fire?What is the difference between them?,Why indoor fires are more dangerous than outdoor fires?,Calculate the ventilation factor and opening factor of this classroom.,Thanks!,Please feel free to raise any question!,Chapter 7 Compartment Fire,Lesson 2 Flashover,Key Words&Phrases,Flashover 轰燃,Fire plume 火羽,Heat flux 热通量,Pyrolyze(pyrolysis)高温裂解,R,adiation feedback heat 辐射热反馈,Structural failure 结构破坏,Collapse 坍塌、倒塌,Hose-line 消防水带,Temperature,Time,Development of a compartment fire,Flashover,轰燃,Growth period,(pre-flashover),初期增长阶段,Fully developed period,(post-flashover),充分发展阶段,Decay,period,衰减阶段,The term flashover was first introduced by UK scientist P.H.Thomas in the 1960s and was used to describe the theory of a fires growth up to the point where it became fully developed.,1.Definition of Flashover,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.,Most commonly used Definitions of flashover are as follows:,Definition of Flashover,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.,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),Initial development of a Fire Plume,(火羽),in a Compartment.,2.Formation of flashover,A hot layer of smoke forms under the ceiling of the room.And it will produce radiation feedback heat,（辐射热反馈）,.,When all the combustible surfaces reach a certain high T,they will pyrolyze and release flammable gases.,When the temperature reaches a certain value,other combustible objects will pyrolyze,(高温裂解),and release pyrolysis gases.,There is a certain,auto-ignition temperature(AIT),(自燃点),for a certain mixture of flammable gases.,When T reaches the auto-ignition temperature of the flammable gases inside the room,suddenly,all the flammable gases and all the combustible surfaces will be on fire.,The T will suddenly go up and it can exceed 1000.,The flames will fill the whole compartment and get out of the openings.,Flashover Fire Cases,Video 1:Flashover experiment,Fire in Bradford City Soccer Stadium,England,1985.,P1:first visible flames,P2:90 seconds,P3:150 seconds,3.Consequences of Flashover,Great damage,Large number of deaths and injuries,Trapped building occupants,(被困居民),Firefighters,Building structure,Properties,3.1 Death and injury caused by flashover,Flashover happens,very suddenly,.,During flashover,fire grows,so,rapidly,that people do not see the need for evacuation,(疏散),until evacuation is impossible.,Flashover usually leads to tripled,(三倍的),death in fire.,Firefighters,:If wearing full protective clothes,any firefighters caught in a compartment which reaches flashover still have seconds to evacuate.,Most firefighting tragedies happen because most of time firefighters are too focusing on searching and rescuing others without noting that flashover is going to happen.,Year,Place,Death,1981,Dublin,48,1982,Los Angeles,24,1991,Petersburg,8,1996,Dusseldorf,17,1997,UK,3,2002,Paris,5,Death caused by flashover in some fire cases,In the USA,NFPA,(美国消防协会),statistics recorded between 1985 and 1994 demonstrated a total of,47,US firefighters lost their lives to flashover.,Firefighters confronted a flashover.,Firefighter caught inside a,flashover.,Wooden beams,(木梁),will char,(烧焦);,Steel,(钢筋),will be permanently weakened.Then it,will expand and damage surrounding structural components,(构件);,Concrete,(水泥),and masonry,(砖瓦),will,spall,(破碎),and may crack into pieces.,3.2 Great damage caused by flashover,Great damage,Building structure,Properties,Structural Failure,Structural Failure,After those structural failures,the,roof,of a building will generally collapse,(倒塌),first,due to the concentration of high temperature gases and flames at the top of the structure.,The,walls,may follow.,Firefighters must be aware that the building could collapse at any point after a compartment reaches flashover.,Catastrophic Collapse of a Building,Video 2:Non-Flashover experiment,Does flashover occur in all the compartment fires?,The Development of Fire With and Without Flashover,4.Fuel and Ventilation Conditions Necessary for Flashover,Fuel and Ventilation Conditions Necessary for Flashover,1.Mass burning rate:,2.Ventilation factor:,4.Criteria of flashover,(轰燃判据),Based on the observations and measurements of compartment fires,different criteria of flashover were proposed:,Radiation heat flux at floor level,(地面热辐射通量),reaches 20kW/m,2,;,Gas Temperature at ceiling level,(顶棚气体温度),reaches 600;,Influencing Factors of Flashover,The amount of combustible materials.,The building materials of the walls and ceiling.,The height and width of the opening.,The kinds of combustible materials.,6.Three ways to delay flashover:,Venting:,By venting windows of a burning room you release the build up of heat in the room.This slows down flashover in addition to improving visibility in a smoke-filled room.,Not venting:,by not venting and instead closing the door to the burning room,you can also delay flashover.By not venting,you starve the fire of oxygen,which slows down the combustion rate and the build up of heat in the room.,This may be done when there is a delay in stretching a hose-line and all persons are out of the burning room.,Portable extinguisher:,The use of a portable extinguisher can cool the heat down in a burning room temporarily and delay flashover.,The sudden lowering of the existing smoke layer(smoke interface).,Sudden increases of heat forcing you to crouch low;,7.Warning signs of flashover,Flames are running overhead on the ceiling;,Perception of rollover:,Rollover is defined,as,sporadic,(零星的),flashes of flame mixed with smoke at ceiling level.,8.Point of no return,The point of no return is a distance inside a burning room beyond which a searching firefighter will not escape and will not reach the door or window entered.,How far inside a burning room can a firefighter be and still escape back out the door alive and not suffer serious bums after a flashover occurs?How far into the burning room that appears about to flashover should a firefighter go?,Five feet is the point of no return after the room explodes into a flashover.,8.Point of no return,1.Fire temperatures of 280-320 F cause intense pain and damage to exposed skin.(,138-160),2.The average temperature in a room that flashes over is 1000 to 1500 F.(537-816,),3.The average person moves 2.5-feet per second when walking,4.How long can a firefighter take 1000-1500 F on the neck,ears,wrists and any other exposed portion of the body?Just two seconds.,Five feet is the point of no return,9.Defensive Search Procedures:,A firefighter sho