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2024年3月21日发(作者：数组链表队列堆栈的区别)

JournalofHazardousMaterials59

Ž

1998

.

211–233

Mathematicalmodellingofaccidentalgasreleases

HelenaMontiel

)

,JuanA.Vılchez,JoaquimCasal,JosepArnaldos

´

Centred’EstudisdelRiscTecnologic

`

(

CERTEC

)

,DepartmentofChemicalEngineering,UniÕersitat

PolitecnicadeCatalunya-Institutd’EstudisCatalansDiagonal647,08028Barcelona,Catalonia,Spain

`

Received16April1997;accepted26October1997

Abstract

Theincreasinguseofnaturalgasentailslargenetworks,locatedmostlyinhighlypopulated

ore,anyaccidentalreleasesofgasthatmightoccurthroughdamagedpipesimplya

cases,thepredictionofreleaseflow-rateandtimeof

r,themathematicalmodelscurrently

availableforperformingthispredictionshowamajorgapintherangeofconditionsoverwhich

rmore,theydonottakeinto

considerationtheunsteadystateexistingwhenasafetydeviceisclosedafteracertaintimeof

paper,anewmodelisdevelopedasacombinationoftheclassical‘hole’and‘pipe’

models,forthecalculationofgasreleasesindistributionsystemsatmediumandlowpressures.

Thismodelcanbeappliedtothesetwocases

Ž

smallholeinatankorapipeandfullboreholes

.

X

Abbreviations:A,ParameterdefinedbyEq.

Ž

47

.

;A

c

,Areaofthecrosssectionofthepipe

Ž

m

2

.

;A

or

,

Holearea

Ž

m

2

.

;B,ParameterdefinedbyEq.

Ž

47

.

;C,Velocityofthesound

Ž

mrs

.

;foridealgases

X

Cs

Ž

kPMr

Ž

RPT

..

1r2

;C,ParameterdefinedbyEq.

Ž

47

.

;CPR,criticalpressureratio

Ž

-

.

;D,Pipediameter

Ž

mormm

.

;d

or

,Holediameter

Ž

mm

.

;F,FunctiondefinedbyEq.

Ž

45

.Ž

-

.

;f,Frictionfactor

Ž

-

.

;G,Massflux

Ž

kgrm

2

s

.

;k,Heatcapacityratio

Ž

-

.

;K

i

,Pressuredropcoefficientforeachfitting

Ž

-

.

;L,Pipelength

Ž

m

.

;L

e

,

Equivalentpipelength

Ž

m

.

;M,Molecularweight

Ž

kgrkmol

.

;m,Massofgascontainedinthepipe

Ž

kg

.

;Ma,

Machnumber,urC

Ž

-

.

;N

i

,numberoffittings

Ž

-

.

;P,Pressure

Ž

Paorbarabs

.

;P

c

,criticalpressure

Ž

Paorbar

abs

.

;Q

m

,Massdischargerate

Ž

kgrsorNm

3

rh

.

;R,Idealgasconstant

Ž

JrkmolK

.

;Re,Reynoldsnumber,

Du

r

r

m

Ž

-

.

;T,Temperature

Ž

K

.

;t,Time

Ž

s

.

;t

c

,Criticaltime

Ž

s

.

;u,Velocityofthegas

Ž

mrs

.

;V

P

,Pipe

volume

Ž

m

3

.

;Y,ParameterdefinedbyEq.

Ž

14

.Ž

-

.

;Greekletters:

a

,ParameterdefinedbyEq.

Ž

36

.

;

b

,

ParameterdefinedbyEq.

Ž

39

.

;

F

,ParameterdefinedbyEq.

Ž

47

.

;

r

,Density

Ž

kgrm

3

.

;

m

,Viscosity

Ž

kgrm

s

.

;Subscripts:0,Steady-state;0

sub

,Steadystateorinitialvaluesinsubsonicflow;1,Atthebeginningofthe

pipe;2,Insidethepipeandonalevelwiththehole;3,Atthehole;a,Inthesurroundings,atatmospheric

pressure;E,Regulatorinletconditions;i,Initialconditions;j,Anypoint

)

Correspondingauthor.

0304-3894r98r$htsreserved.

PIIS0304-3894

Ž

97

.

00149-0

alofHazardousMaterials59

(

1998

)

211–233

andalsototheintermediatesituation,licationtovariousaccident

scenariosisdiscussed.q1998ElsevierScienceB.V.

Keywords:Mathematicalmodelling;Gasreleases;Accidental

uction

Theconsumptionofnaturalgasintheindustrializedcountrieshasincreasedsteadily

an-combustioncharacteristicsanditseaseofdistributionatlow

pressuresjustifyitswideuse

Ž

bothforthegenerationofelectricityandasadomestic

fuel

.

,whichhasdoubledfrom1990to1994,resultinginaworldwideconsumptionof

2170=10

12

m

3

in1994.

Thisusehasmeantinstallingandmaintainingcomplexpipingsystemstotransport

anddistributegas,hese

facts,accidentscausedbythelossofcontainmentofnaturalgascaninvolvesubstantial

economiclossesandevenvictimsamongstthepopulation.

Polyethylenetubinghaslargelyreplacedthesteelorcastirongaspipeswhichwere

hylenepipehasseveraladvantages:itiseasiertoinstall,has

ndsof

kilometersofthispipehavebeeninstalledanditsuseisstillincreasing.

Gaspipes,whicharemostlyinstalledunderground,canbedamagedbyvarious

activities:undergroundwork,bull-dozers,eisapartialorcompletebreaking

ofthepipe,ituationcanbeno

morethananincidentiftheleakissmallorisrapidlydetected,orcanleadtoan

accidentdependingonthecircumstances.

Arecentsurveyof185accidentsinvolvingnaturalgas

w

1

x

showedthat,ofthetotal,

131werecausedduringtransportation,eitherbyroad,railway,

analysisofthesedataclearlyshowstherelativelyhighfrequencyofaccidentsinpipes:

tfrequentcausesoftheaccidentswere

mechanicalfailure,impactfailure,tthe

accidentsarisingfromimpactfailure

Ž

39

.

,themostfrequentspecificcausewas

excavatingmachinery

Ž

21accidents

.

,followedbyvehicles

Ž

5

.

andheavyobjects

Ž

5

.

.

Otherspecificcausesduetoexternaleventsweregroundsubsidence

Ž

4cases

.

and

sabotagervandalism

Ž

4cases

.

.

Intheanalysisofsuchaccidents,orwhenforecastingtheconsequencesofthistype

ofhypotheticalsituation,thefirststageistoestimatetheflow-rateatwhichthegasis

beingreleasedthroughthedamagedpipe

w

2

x

.Thisisacomplexproblem,whichinfact

beginswiththedefinitionofthe‘holediameter’:aparticularopeningsizemustbe

assumed;itcanbeasmallhole,alargeoneoreventhewholecross-sectionofthepipe

,theflow-ratethroughthisholemustbecalculated,both

forthecaseofconstantflow-rateandforthecaseofdecreasingvelocity

Ž

ifan

emergencyvalveisautomaticallyclosed,forexample

.

.Inthispaper,amathematical

modelisdescribedwhichallowsthepredictionoftheflow-rateofgasthrougha

damagedpipe.


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