火灾动力学FD06a-挥发与闪点

希腊火希腊火(flamethrower)+与石棉Asbestos3猛火油柜(flamethrower)

(c.a.1045AD)改变历史的照片与改变历史的发明HoytC.HottelPhanThịKimPhúc潘金福改变历史的橙剂（孟山都Mosanto）液体安全之提纲挥发(liquidfuelsafety)泄漏动力学(forensicscience)点火与蔓延(hazardcontrol)扬沸现象(boilover)液滴动力学（dropletdynamics）水灭火动力学(firepointtheory)7闪点什么是最低环境温度，可以提供刚刚足够的能量，让液体表面的燃料浓度刚好可以达到支持闪燃的程度？由于液体表面的燃料浓度刚刚达到可燃限，所以点火过程会很快消耗那些位于可燃限附近的蒸汽，然后被高浓度的燃气熄灭，这一短时间的一闪即灭的点燃过程，被称作闪燃（flashfire）刚刚让液体表面支持闪燃的环境温度，称作闪点（flashpoint）闪点是液体表面存在燃爆风险的起点，因此对于液体燃料的存储和运输过程的风险控制至关重要闪点必须用实验方法来测定液体燃料的危险性随温度变化2025/6/269闪点的测量开杯与闭杯测量结果美国NFPA30液体安全性的分类FlammableIA–Flashpoint<73°F,boilingpoint<100°FFlammableIB–Flashpoint<73°F,boilingpoint>100°FFlammableIC–73°F<Flashpoint<100°FCombustibleII–100°F<Flashpoint<140°FCombustibleIIIA–140°F<Flashpoint<200°FCombustibleIIIB–Flashpoint>200°F在液体储藏仓库中的应用燃料分类的地理要素由于地理位置的差异，英国采取不同的油品安全分类系统.挥发公式的来源RudolphClausius德国物理学家和数学家热力学科学最重要的贡献者之一第一次引入了熵的概念显着影响了气体和电力动力学理论领域BenoitPaulÉmileClapeyron法国物理学家和工程师被认为是热力学的创始人有助于研究完美的气体和均质固体的平衡Clausius-Clapeyron方程的多种形式Clausius-Clapeyron方程的微分形式Clausius-Clapeyron方程的积分形式Clausius-Clapeyron方程Additional/

complementaryequationsTrouton’sruleDalton’slawRaoult’slaw

HeatofvaporizationattemperatureTMolecularweightBoilingpoint液面上的蒸汽分布红外相机注视下的挥发过程常规灾害计算程序1.计算表面浓度2.用Trouton’srule计算挥发的焓值3.用Raoult’slawandDalton’slaw计算蒸汽分压力4.找到点火的环境温度or蒸发率估算Quintiere,Fundamentalsoffirephenomena,Wiley&sons,2006,pp.148

20例题1:基于低燃限的

最小点火环境温度（闪点）估算甲醇在标况（25Cand1atm）下的空气中的最小点火温度（闪点）:例题2：燃料的表面分布

学期结束，学生们希望喝点烈酒庆祝一下（ahottoddy）。他们有2inch高的烈酒杯，一半装满乙醇，放在微波炉内。液体被加热到50℃。假设蒸汽浓度在液体表面上方线性变化，乙醇的高低可燃限分别是3.3和19.0%（体积浓度）。计算酒杯中可以被点燃的区域。必要的数据，乙醇的汽化潜热是840J/g，沸点是78C。hLhu例题03:从蒸气压到表面温度SubstanceFormulaMWDhfkJmol-1

Dhc(lower)kJmol-1Dhc(lower)MJkg-1Cst(vol%)LFL(vol%)UFL(vol%)AIT(ºC)inairFlashpoint(ºC)Boilingpoint(ºC)PvapatFP(atm)acetoneC3H6O58.08-249.41656.628.524.982.612.8465-18560.03622计算丙酮（acetone）的蒸气压达到0.036atm的环境温度;;例题04:从表面浓度到表面温度=>=>混合物的闪点液体燃料已知的一定是质量浓度，首先需要转换成摩尔浓度或体积浓度，这需要分子量和密度信息；在临界温度下，计算其饱和蒸气压；根据饱和蒸气压与摩尔浓度之乘积，就是蒸汽的分压力；蒸汽分压与环境压力之比，就是蒸汽体积浓度；针对多种燃料，运用勒夏特列定理，可以得到表面浓度是否达到低燃限的结果。如果表面浓度可燃，说明液体闪点低于环境温度，燃料属于高风险的易燃燃料，需要特殊的安全处理措施。混合物的安全性估算（1/2）混合物的安全性估算（2/2）燃料表面的蒸汽浓度（实验结果）27总结闪点是定义液体燃料点火潜力的单一重要的参数。闪点对应于液体表面浓度达到LFL的环境温度。闪点依赖于挥发过程，后者是克劳修斯-克拉佩龙方程决定的结果。28美国航空燃料简史莱特兄弟的发明为什么会成功？为什么他们的飞机会上天？通过活动环节的天才组合增加了飞机的可控性（他们是自行车生产商）新发明的内燃机具有紧凑高效的特征。利用了下列成果EtinenneLenoir,1860年发明第一款内燃机N.A.Otto,KarlBenz,1876年发明四冲程内燃机SamuelLangley,1896年发明蒸汽机马达CharlesManley,1901年发明内燃机马达TWA800爆炸事件让美国重新回顾燃料的安全性汽油的妙用DistilledproductfromtheprocessofmakingKeroseneforillumination.(economyandavailability)Distillant(gasoline)isusedtobedampedintoseaforsafetyreasons.Duringthefirstworldwar,theengineknock(Pinking)becameaproblemToavoidthisproblem,engineersusefuelsoflightspecificgravity.(Evaporability)燃料研究ChemicalcompositionsoffuelshadaprofoundeffectuponengineperformanceAtasinglecompressionratio,differencesinpowerdevelopmentwereminorThemoredetonationresistantthefuel,thehigherthecompressionratiothatcouldbeused,andtherefore,themoreefficientandpowerfultheenginecouldbe.32裂化问题In1792,crackingwasusedinUKformakingilluminatinggas.1912,Burtonprocesscanmake35%gasolineoutofcrudeoil.Thecrackedfuelsgenerateresinousandgummymaterialinpipelines,causingcorrosionproblem.Theanti-knockpropertiesofcrackedfuelisnotappreciatedinthebeginning.Tetraethylleadisfoundtobegoodatresistingdetonationandoverheatingproblems.NavyintroducedTELin1926.1935,100octaneaviationgasolineintroducedinKleinpaper.33喷气燃料MostofjetenginesdevelopedbeforetheendofworldwarIIutilizedordinarykeroseneasafuel.(Duetoavailability.Gasolineismilitarygoodsundercontrol.)Whittlehadconsidereddieselfuel,butkerosenewaschosenforflighttestingbecauseitslowfreezepoint.JP-1,aconventionallampburningkerosenewith-40Ffreezepoint.(1944)(Blowoutandreignitiondifficulties)JP-2,awide-cutfueltoexpandsupplies.(itsviscosityisunstable,riskofflammabilitybetween20and80Fatsealevel).JP-3andJP-41946,NACAevaluateFuelAandFuel-BFuelAislabeledasJP-3,withavailabilityof48%.FuelBisa100FflashpointkerosenesimilartoJP-1.Highvolatilityisabigproblemforenginesrunningat30,000feethigh.Finally,itisdecidedtolowerthevaporpressurefrom7psiato3psia,reducingevaporationlossesathighaltitudetoaverylowlevel.Thiswide-cutfuelisJP-4.35JP-4andJP-5JP-4istypicallycontains50to60%gasoline,andtheremainderiskerosene.Theprimaryadvantageofthewidecutisthegreatlyincreasedavailabilityoftheresultingfuel.USnavyuseaviationgasoline(JP-4)forturbojetaircraft.Soon,itlearnedthattheleadinthefuelwasattackingtheenginehotsectioncomponents.1952,“jetmix”,JP-5isdesignedwithahighflashpointkerosene.JP-5hasaminimumflashpointof140F,forship-boardsafetyreasons.Tomaximizeavailabilityofthisfuel,theNavyselectedamaximumfreezepointof-50F.Becausemissionisshort,whiletheseahasalargethermalmass(reservoir).JP-6Forsupersonicflight,JP-6wasdevelopedin1956.ItisakerosenebasedfuelsimilartoJP-5,butwithalowerfreezepointandimprovedthermalstability.JP-6’svaporpressureof0.5psiat100Fwasconsiderablylowerthanthe3psiofJP-4.JP-6’savailabilityis30%ofJP-4.U2JPTS(Thermallystablejetfuel)1956,withJFA-5(jetfueladditive5)37JP-7andJP-8SR-71,Mach-3speed,highheatofcombustion,paraffinsandcycloparaffins,JP-7,high-freezepoint(-46F)becauseofaerodynamicheating.CombatexperienceobservedduringtheVietnamwar,revealedthattheUSAFaircraft,usehighlightvolatileJP4hashighercombatlossesthanUSNaircraft,uselowervolatilityJP5.CrashdataindicatedthattheprobabilityofapostcrashfireforJP4isnearly100%,muchhigherthanwithakerosenefuelsuchasJP5orcommercialJetA.Ground-handlingdevice.JP-8wasdevelopedtoprovideasafer,kerosenebasedjetfuel(similartocommercialjetA-1)forAirForce.Itwasdevelopedtohaveadequateavailabilityandanacceptablefreezepoint(-47C).USAFuseJP-8forbattlefielduse.USNretainsJP-5astheshipboardfuelofchoice.JP-8+100Athightemperaturesthefueltendstobecomeunstableandprecipitatescarbonaceousmaterials.Oxygendissolvedinthefuelreactswithotherfuelcomponentstoformadditionalcarbonadoesmaterial.Fuelsystemandenginedesignersgenerallytrytorestrictthetemperatureoft