P. 1


# OAR Box 1830 Prepped by Ollie Stewart



### Document

Number: 

# 200 ) IV-C-16

7 Docket Number: 

# A-87-1 1

Printed 11/13/20087:21:02 AM Sheet 200of 232[.X'itl ~,



## _v*07 I UNITE D S7A7I 3 ENVIRONMENTA L PROTECTIO N AGENC Y Wit I ARBOR
. MICHIGA N 4310 5 P. 2

p ' - : C . (0 7 -

, OFFIC E O F AI R AN C RADIATIO N

Mr . Stuar t Drake . Kirklan d an

d Elli s 6 5 5 15t h St. , N

W Washington , D.C . 2000 5 Dea r Mr . Drake : Jan e Roeme r o f EPA' s Offic e o f Genera l Counse l infor i cr vou r recu s 

### :o r . n e versio n 

### ou

r coraouis r U-.c. o . escribe d b

yDr . Davi d Bartu s a t th e meetin g betwee n E? Aa n

. , 1989 . Enclose d i s a draf t cop yo f Releas e o f the ? T Evaporativ e Emission s Mode l alon g wit h a draf t o f th e update d user s guide . Neithe r th e mode l no r th e u i guid e ha s receive d revie w withi n EP Abeyon d tha t U I . U S G G M 2. 0 cop y o_r s D«
- Bartus . Currently , Dr . Bartus , wh o develope d th e ? T model , o n a thre e mont h leav e o f absence . Durin g hi s absence , ano i enginee r i n m

yprojec c group , Pau l Laing , wil l o e av s provid e informatio n abou t the model . Pleas e contac t 313/563-427 4 i f yo u hav e an yquestion s o r comments . = i 1
Sincerely , 

## /hu;^-? " C Richar d Rykowski , Senio r Projec t Manage r Standard s Developmen t an d Suooor t Branc h cc . Jan e Roemer , EPA/OG C (withou t enclosures ) Docke t A-85-2 I Docke t A-87-1 1 Enclosure s 7 2 6 7 WP. 3



### P T Evaporativ e Emission s Mode l Descriptio n an dUser s Guid e Releas e 2. 0

June , 198 9

Davi d B
. Bartu s Standard s Development

an d Suppor

t Branc h Emissio n Contro l Technolog y Divisio n Office of Mobil e Source s Office of Air an d Radiatio n U.S
. Environmenta

l Protectio n Agenc yP. 4



# BR A 

# F T

I Introductio n 1 I I Mode l Descriptio n 3 A ) Introductio n 3 B ) Inpu tDat a 3 1 ) Scala r Dat a3 a ) Tan k Siz e 3 b ) Canister

Siz e 4 c ) Initia l Caniste r Loa d 4 d ) MaximumPurg e Rate 4 e ) Diurna

l Caniste r Loa d 4 f ) Hotsoa k

Caniste r

Loa d 5 g ) Purg e Dela

y 5 h ) Horsepower

Correlatio n Parameter s 5 i ) Driv e Schedul e DataFil e Nam e 6 j ) Vapo r

Generatio n Dat aFil e Name s 6 k ) Even t Dat aFil e Nam

e 6 1 ) Lo g Output

Fil e Nam e 6 m ) Plo t Output Fil e Nam e 6 n ) Purg e Typ e Flag 6 o ) Caniste r

Purg e Curv e Typ e 6 p ) Canister

Loa d Model Flag 7 q ) Back-purg e Flo w Rat

e 7 2 ) Tabula r Dat a7 a ) Driv e Schedul e Tabl e 7 b ) Canister

Purg e Tabl e 7 c ) Vapo r Generatio n Tabl e 8 3 ) Even t Dat a8 a ) Diurna l Event s 8 b ) Hotsoa

k Event s 9 c ) Driv e Event s 9 C ) Mode l Operatio n an d Structur e 1 2 1 ) Mode l Operatio n 1 2 2 ) Model Structur

e 1 4 3 ) Component

Descriptio n 1 6 a ) Ptdih s 1 6 b ) Ptdriv e 1 6 c ) Getpurg e 1 7 d ) Getspee d1 8 e ) Geth p 1 8 g ) Getvp r

1 9 h ) Dopurg e 1 9 i ) Ptbkp g 2 4 II I User s Guid e 2 5 A ) Overvie w 2 5 B ) Dat a Fil e Preparatio n 2 5 1 ) Inpu t Dat aPreparatio n 2 6P. 5

2 ) Tabula r Dat a Preparatio n 2 7 a ) Driv e Schedul e Tabl e 27 b ) Canister

Purg e Tabl e 27 c ) Vapo r

Generatio n Tabl e 2 8 3 ) Even t DataPreparatio n 3 1 C ) Progra m Us e 3 2 1 ) Runnin g th e Mode l 3 2 2 ) Outpu t Descriptio n 3 4 a ) Termina l Outpu t

3 4 b ) Lo g Fil e Output

3 7 c ) Plo t Fil e Output

3 8 D ) Progra m Generatio n an d Modificatio n 3 8 1 ) Progra mGeneratio n 3 8 2 ) Progra mModificatio n 3 9 I V Reference s 4 1 V Appendice s 4 2 A ) Distributio n Dis k Content s an d Mode l Installatio n 4 2 1 ) Distributio n Dis k

Content s 4 2 2 ) Model Installatio n 4 4 B ) Refueling/Exces s Evaporativ e Emission s Worksho p Dat a 4 6 1 ) Introductio n 4 6 2 ) Inpu t Data4 6 a ) Scala r Dat a4 6 b ) Tabula

r Dat a4 6 c ) Even t Dat a4 7 C ) Sampl e Run s 4 8 1 ) Descriptio n 4 8 3 ) Test 2 Sampl e Ru n Dat a5 5 D ) Vapo r Generatio n an d Temperatur e Profil e Dat a 6 1 1 ) Emission s Modellin g 6 1 2 ) Diurna

l Uncontrolle d Emission s 6 1 3 ) Hotsoa

k Uncontrolle d Emission s 6 1 4 ) Vapor Generatio n 6 3 E ) Summar y o f

Mode l Change s Betwee n Release s 1. 0 an d 2.0....6 4P. 6



### Lis to f Figure s Figure 1 Sampl e Temperatur e Profil e 1 1 Figure 2 PT Model Operationa l Flowchar

t 1 3 Figure 3 P T Model Progra mStructur

e 1 5 Figure 4 Canister Loadin g Efficiency v s Canister Loa d 2 0 Figure 5 Sampl e Canister Purg e Curv e 2 1 Figure 6 Sampl e Analytica l Purg e Curv e Family 2 3 Figure 7 Distributio n Dis k Director y Structur e 3 3P. 7

I Introductio n Th e P T mode l i s ase t

o f compute r

algorithm s an d associate d dat atha t can b e use d t o simulat e th e behavio r

an dperformanc e o f

evaporativ e emission s contro l systems . Th e mode l i s base do n a

n accountin g syste mtha

t include s source s o f

hydrocarbo n vapor s in a vehicle , suc h a s th e fuel tank , vapo r storag e devices , suc h a s th e charcoa l canister , an d finally , vapo r

sinks , suc h a s th e engine/purg e contro l system . Durin g simulatio n o f variou s evaporativ e emission s events , th e behavio r o f thes e vehicl e component s i s predicted , an dacontinuou s histor y i s maintaine d o f

th e carbo n caniste r

storag e device
. A ke y feature o f

th e mode l i s tha

t i t make s us e o f

instantaneou s drivin g schedul e velocitie s an daccelerations , i n contras t t o averag e values , s o tha t interaction s betwee n drivin g patterns , purg e control , fue l tank vapo r generatio n an d charcoa l adsorptio n characteristic s ca n b e realisticall y simulated
. Th e P T mode l i s intende dt o serv e thre e purposes . Th e firs t i s t o estimat e evaporativ e an d runnin g los s emission s fromasingl e vehicl e i n respons e to aspecifie d set o f events , fuel tank an dcaniste r

characteristics , an d purg e contro l strategy . Th e secon d i s t o serv e a s a desig n too l t o evaluat e variou s vehicl e emission s tes t procedure s an d t o determin e caniste r size s an dpurg e rate s neede dt o pas s give n procedures
. Finally , th e mode l i s intende d t o provid e estimate s o f

instantaneou s engin e fue l requirement s an d o f unmetere d fue l provide ddurin g caniste r purge . Thes e values can assis t i n estimatin g th e impac t o f evaporativ e emission s contro l system s o n exhaus t pollutants
. Becaus e th e mode l wa s constructe d primaril y a s atoo l t o evaluat e evaporativ e emission s tes t procedures , severa

l aspect s o f

evaporativ e emission s hav e no t bee n explicitl y modelled
. Th e firs t o f thes e i s th e respons e o f

fue l syste mtemperature s t o ambien t temperatur e an d vehicl e operatin g mode
. Temperature effects , however , ar e implicitl y accounte d fo

r i n thi s mode l throug h appropriat e specificatio n of ho t soa k an d diurna l emissions , a s wel l a s runnin g los s vapo r

generation
. A secon d aspec t o f evaporativ e emission s tha t ha s no t been explicitl y modelle di s fuel syste mpressure . Fue l syste mpressure s ar e assume d t o remai n a t aconstan t

valu e durin g al l phase s of simulatio n an d th e correspondin g vehicl e operatin g events . A s wit

h fue l syste mtemperature , th e influenc e o f pressur e o n evaporativ e emission s ca

n b e implicitl y accounte d fo r throug h appropriate specificatio n of hydrocarbo n vapo r generatio n values
. Numerou s revision s an denhancement s hav e bee n adde d t o th e mode l sinc e it s initia l development
. Several significan t modification s wer e mad e betwee n th e Jun e 30 , 198 8 publi c worksho p [2 ] a

t whic h th e mode l wa s first presente d an d th e tim e tha t versio n 1. 0 o f th e mode l wa s releasedi n September , 1988 , an d anumber o f other change s mad e sinc e th e releas e o f versio n 1.0
. Al l change s t o dat e are incorporate d i n Releas e 2. 0 o f th e P T Evaporativ e Emission s Model , whic h thi s manua l documents
. User s shoul d not e that furthe r modification s ar

e likely t o b e made i

n i n the future
. Enhancement s t o th e P T mode l include d in releas e 2. 0 ca n b e groupe d int o fou

r areas . Th e first tw o o f thes e focu s o n caniste r

loadin g an d purgin g behavior , wit h th e objectiv e o f realisticall y modellin g non-ideal caniste r effects , an d eliminatin g som e o f th e significan t simplifyin g assumption s buil d int o th e origina l versio n o f th e model
. Th e thir d are a focuse s o n a

n additiona l sourc e o f

caniste r purg e no t

include d i n th e origina l model , specifically , purg e flo w tha t occur s durin g period s o f decreasin g fue

l tank temperature . Thi s phenomeno n occur s regularl y in-us e afte r certai n vehicl e operatin g events , an d ma y hav e asmal l bu t

significant

effec t o n evaporativ e emission s contro l syste mperformance
. Th e final are ao f

enhancemen t

focuse s o n additional dat aan d vapo r generatio n table s tha

tP. 8

hav e bee n develope dsinc e th e first mode l release , an d whic h ma y b e usefu l i n modellin g high-temperature scenario s tha t approac h the boilin g point o f gasolin e fuels
. I n bot h mode l releases , emphasi s ha s bee n place d o n functionalit y rathe r tha n appearance . I n th e mode l itself

, for example , basi c erro r

checkin g ha s bee n included , bu t exhaustiv e verificatio n o f

al l inpu t dat aha s no t

Althoug h graphica

l displa y o f certai n mode l output s i s useful , onl y tabula

r outpu t o f thes e dat ai s generate d b

y th e model
. User s ma

y incorporate thes e dat aint o thei r

preferre d graphic s packag e i n orde r t o generat e an y desire d plots
. I n th e report , th e function s an d format s of al l inpu t dat aare described , bu t

specificatio n of method s fo r

generatin g specifi c numerical value s are omitte d i n some instances
. In thes e cases , th e neede ddat ama y b e obtaine d fro msource s rangin g fro mlaboratory dat at o compute r simulations , accordin g to th e resource s availabl e t o th e user . Finally , i n many instances , "in-us e average " value s fo r inpu t variable s ar

e no t provided , sinc e th e mode l wil l ofte n b e use dt o simulate vehicle s and tes t procedure s fo

r whic h such dat aar

e no t available
. Thi s documen t

i s divide dint o tw o majo r sections
. I n Sectio n II , "Mode l Description, " th e dat arequire db y th e mode l i s discussed , alon g wit h structur e an d operatio n o f th e model
. I n Sectio n IH , "User s Guide, " specifi c detail s o f ho w th e mode l ca n b e use dar e provided , includin g preparatio n of dat afiles, runnin g th e mode l itself , erro r determination , andinterpretatio n o f

output .P. 9

I I Mode l Descriptio n Thi s sectio n provide s description s o f th e P T model , inpu t

dat arequire d b y it , an d ho w thes e dat aar e use ddurin g simulations
. Sectio n A , "Introduction, " give s agenera l overvie w o f

th e mode l an dit s operation
. Sectio n B , "Inpu tData, " discusse s in detai l th e variou s dat aitem s an dtable s tha t mus t b e supplie d t o th e model
. Finally , Sectio n C , "Mode l Operatio n an d Structure, " describe s th e detaile d calculatio n step s carrie d ou t b y th e model , an dth e structure and algorithm s use d b y it
. A ) Introductio n I n th e mos t

general sense , th e P T mode l consist s o f aset o f computationa l algorithms , an d anumbe r o f dat aset s upo n whic h thes e algorithm s operate . I n practica l terms , th e computationa l algorithm s ar e embodie d i n acompute r program , an d th e set s o f

dat aar e store da s number s an dtex t in compute r

dat afiles. Th e mode l carrie s ou t simulation s b y firs t readin g dat afile s tha

t describ e th e vehicl e t o b e simulate d an d it s initia l condition , th e behavio r o f vehicl e component s associate d wit h evaporativ e emissions
. Next , th e mode l reads , i n asequential fashion , aserie s o f event s tha

t asimulate d vehicl e i s t o experience
. Durin g simulatio n o f

eac h event , th e mode l calculate s th e quantity o f hydrocarbo n vapor s generated , ho w muc h o f

thes e ar e loade d t o o r

purge d fro mth e charcoa l canister , an dth e quantit y o f vapor s burne db

y th e engine
. A

t th e en d o f

eac h simulate d event , summarie s o f simulatio n result s fro

mth e event

and the current

stat e o f th e simulate d vehicl e ar

e generate d an ddisplayed
. B ) Inpu tDat a Thi s sectio n describe s th e variou s dat aitem s tha t ar e require d b y th e P T model , th e expecte ddat aformat , if

any , an d th e sourc e o f

dat afo r eac h itemo r

table
. Model inpu t

dat a ca n b e divide dint o thre e types : scalar , tabular , an d event . Scala r data , describe d belo w i n sectio n 1 , "Scalar Data, " i s generall y vehicle-specific , whil e tabular data , describe d i n sectio n 2 , "Tabular Data, " i s eithe r mostl y o r

totall y vehicl e independent
. Even t data , describe dbelo w i n sectio n 3 , "Even tData, " i s vehicl e dependent , bu t wil l var y slightl y i n respons e t o fue

l vapo r pressure . 1 ) Scala r Dat a Scala r dat aitem s consis t

o f asingl e valu e o r

asmal l but

fixed number

o f dat aitems
. Thes e dat avalue s generall y describ e vehicl e components , thei r behavior , o r

thei r conditio n a

t th e star t o f asimulation
. Some value s ar e dependent

onl y o n th e vehicl e t o b e simulate d (fue l tan k size , fo r example) , whil e other s depen d o n fuel characteristic s a s wel l (diurna l an d hotsoa k caniste r loads)
. Fuel-dependen t

dat avalue s ca

n b e obtaine d fromexperimenta l data , o r fro mmodellin g results
. Care mus t b e exercised , however , tha t suc h dat ab e obtaine do n aconsisten t

basi s wit h th e vehicl e t o b e simulate d b y th e P T model
. Eac h scala r dat aite mrequire db

y th e PT model i s describe d below
. a ) Tan k Siz e Thi s dat aite mspecifie s th e nomina l usabl e liqui d volume , i

n gallons , o f

th e fue l tan k in th e vehicl e t o b e modelled
. Th e valu e specifie d mus t li e withi n th e rang e o f

0.0<(Tank

Size ) < 100.0
. Neithe r

th e fre e headspac e no r

th e fill leve l i s explicitl y specifie d i n th e model
. Bot h o f thes e value s ar e implicitl y accounte d for in th e value s specifie d for diurna l an dP.1 0



### hotsoa k caniste r loads , bac k purge vapo

r flo w rate , an d fo r value s containedi

n th e vapo r generatio n table
. Furthe

r description s o

f thes e latte r value s ca n be foun dbelow
. b ) Caniste r Siz e Thi s dat aite mspecifie s th

e carbo n caniste r size , i n liter s o f charcoal , o

f th e caniste r i n th e vehicle t o b e modelled
. Th

e valu e mus t alway s be specified , an

dmust li e withi n th e range o f 0.0<(Caniste

r Size)<50.01
. I n addition , thi s ite

mals o specifie s th

e hydrocarbo

n saturation capacit

y o f th e canister , i

n grams pe r liter , whe n non-idea l caniste r loadin g calculation s ar

e specified
. Se

e th e caniste r loadin g model fla

g descriptio n below in Section p , an dSection II-B-3-h , "Dopurge. " Whe n idea l caniste r loadin g i s specifie

d(th e onl y optio n i n Releas e 1.

0 o f th e P T model) , the caniste r saturation capacit

y value ma

y b e omitted
. Acceptable caniste r saturation capacit y value s must

li e withi n th e rang e o f 0.0<(Saturation Cap.)<150. 0 g/1
. Fo r bot h idea l an d non-idea l caniste r loadin g models , th

e type , load/purg e characteristic s an d th e breakthroug

h capacit y o f th e charcoa l i s implicitl

y specifie dthroug h th e caniste r purg e table , described belo

w i n Sectio n 2- b an dSectio n II-B-3-h , "Dopurge. " c ) Initia

l Caniste r Loa

d Thi s dat aite mspecifie s th

e initia l loadin g a t th e star t o f simulation , i

n percen t o f tota l capacity , o f th e caniste r i n th e vehicl e t o be modelled
. Th

e valu e specifie dmust li e withi n th e rang e o f 0.0<(lnitia

l Load)<= 100.0
. A value o f 0. 0 correspond s t

o afull y purged canister , while avalu e o

f 100. 0 correspond s t

o afull y loadedcanister
. Normally , a n initia l caniste r loadin g slightl y les s tha n 100. 0 percen

t (99.0 , fo r example) i s specifie

d t o avoi d anomalou s prediction s o f uncontrolledhydrocarbo

n ventin g during th

e first fe w second s o f adrive tha

t begin s wit h afull y loade dcanister , particularl

y whe n idea l caniste r loadin g i s specified
. d ) Maximu

m Purg e Rat e Thi s dat aite mspecifie s th

e maximu mcaniste r purge rate , i

n standar dcubic fee t pe r minute , characteristi c o

f th e vehicl e t o b e modelled
. Th

e valu e specifie dmus t b e greate r tha n zero . Durin g simulation , th

e actua l caniste r purge rat e wil l b e calculatedas som

e fractio n o f thi s maximu mrat e i n respons e t

o vehicl e speedan

dacceleration
. Furthe

r discussion s o

f caniste r purge rat e calculation s ca

n b e foun di n Sectio n II-C-l-c , "Getpurge. " e ) Diurna

l Caniste r Loa

d Thi s dat aite mspecifie s th

e quantit y o f hydrocarbon s generate

ddurin g adiuma l hea t build , i n grams pe r gallo n o f usable liquidfue

l tan k capacity , t o b e use ddurin g simulation
. Thi s value represent s uncontrolled diurna l vapo r generation i

n th e fue l tank , i n contras t t o th e quantit y o f hydrocarbon s vente

dfro macaniste

r durin g adiuma l emission s test . Th

e value specifie d must be greate r tha n zero . Diuma

l caniste r loa di s specifie

dfo r areference hea

t build , usuall

y th e standar d FT P range o f 60-84 °F , an

dfo r aparticula

r fue l vapo r pressure . Durin g simulation , th

e actua l diurna l caniste r loa di s calculatedb

y adjustin g th e specifie d loa d fo r fue l tan k size an d fo r difference s i

n temperatur

e betwee n th e simulateddiurna

l fro mth e referenc e diurnal
. Adjustment s fo r fue l tan k size ar e mad e b y multiplying th

e specifie d diurna l loa d b y th e specifie dfue l tan k size , whil e th e temperatur

e adjustmen

t i s mad e b y multiplying th

e specifie dloa db y th e diuma l even t multiplie r rea dfro mth e even t file fo r adiurna l event . Furthe

r detail s o f thi s temperatur

e correction an

do f th e diurna lP.1 1



### even t multiplie r ca n be foun di n Section II-B-3-a , "Diurna l Events, " an

di n Section II-C-3-a , "Ptdihs. " Th e diurna l caniste r loa d valu e i s partially vehicle-independent , a s i t i s specified o

n a specifi c rathe r tha n a n absolut e basis , bu t i t i s implicitl

y dependen

t o n th e fre e headspac e volum e o f th e vehicle t o b e modelled
. Whil

e thi s headspac e volume , as apercentag e o f useable liqui d volume , ma

y b e simila r acros s abroa

dspectru mo f th e in-us e vehicle fleet, th e correspondin g volum

e o f aspecific vehicl e ma

y deviat e markedl y fro mth e flee t average . Car

e must be take n whe n specifyin g th e diurna l caniste r loa dfo r suc h vehicle s tha t th e appropriat

e valu e i s used
. f ) Hotsoa

k Caniste r Loa

d Thi s dataite

mspecifie s th

e quantit y o f hydrocarbon s generatedduring ahotsoa k event , i n grams/gallo

n o f usable liquid fue

l tan k capacity , t o be use dduring simulation
. Thi s value represents uncontrolle

d hotsoa k vapo r generatio n i n th e fue l tank, i n contras t t o th e quantit y o f hydrocarbon s vente d fro

macaniste

r durin g ahotsoa

k emission s test . The valu e specifie d must b e greate r tha n zero . Hotsoa

k caniste r loa di s specifiedfo

r a n arbitrar y referenc e end-of-drive temperatur e an daparticula

r fue l vapo r pressure . I

n th e cas e o f a n FT P pre p drive , i n whic h th e initia l fue l tan k temperatur

e migh t b e 72. 0 ° F an

d th e temperatur e rise durin

g th e drive migh

t b e 15. 0 °F , th

e end-of-driv

e woul dbe 97. 0 °F
. I

n th e cas e o f carbureted vehicles , an

dadditiona

l contribution must

b e addedfo

r emission s fro mth e carbureto r bowl
. Durin

g simulation , th

e actua l hotsoa k caniste r loa di s calculated b y adjustin g th e specifie d loa dfo r fue l tan k siz e an dfo r difference s i

n temperatur

e betwee n th e simulate d hotsoa k fro mth e reference hotsoak
. Adjustment s fo r fue l tan k size ar e mad e b y multiplyin g th

e specifiedloa

db y th e simulatedvehicl e fue

l tan k size , whil e the temperatur e adjustmen

t i s mad e b y multiplying th

e specifie dloa dby th e hotsoa

k even t multiplie r rea d fro mth e even t file fo r ahotsoa k even t Furthe r detail s o f thi s temperatur

e correction an

d o f th e hotsoa k even t multiplie r ca n b e foun di n Sectio n II-B-3-b , "Hotsoa

k Events, " an

d i n Section II-C-3-a , "Ptdihs. " Comments mad

e above i n section II-B-l-e , "Diurna l Caniste r Loading, " regardin g fue l tan k vapo r headspac e assumption s als o appl y t o specification o

f hotsoa k caniste r loadin g values
. g ) Purge Dela

y Thi s dat aite mspecifie s th

e dela y betwee n th e beginnin g o f adrive even

t an dth e star t o f caniste r purge , i n th e unit s o f th e driv e schedule table
. (Se

e Section II-B-2-a , "Driv

e Schedule Table." ) Th

e valu e specifie

dmust b e greate r tha n zero . Specifyin

g avalue greate r tha n th e numbe r o f entrie s i n th e drive schedul

e tabl e effectivel y disable s al

l caniste r purge . Thi s i s permitted , bu t awarnin g messag e i s generatedwhe n suc h asituation i s encountere d durin g mode l operation
. h ) Horsepowe r Correlatio n Parameters Thes e dataspecif

y the empirica

l parameter s usedby the Geth p module , describe d i

n Sectio n IF-C-3-e , "Gethp, " t

o determin e th e horsepowe

r requiredt o propel avehicle a

t a give n spee d an d acceleration
. Suggeste

dvalue s fo r th e fou r requiredparameters ar

e give n i n th e descriptio

n o f Gethp
.P.1 2



### i ) Drive Schedul e Dat a Fil e Nam

e Thi s dat aite mspecifie s th

e pat h nam e t o b e use dwhe n openin g th e dat afile containin

g th e driv e schedul e table
. Thi s datatabl e i s describe din Section 2-a , "Driv e Schedul e Table " below , and the forma t o f thi s dataite

mi n Sectio n III-C , "Inpu

tDat a Preparation. " j ) Vapo r Generatio n Dat a Fil e Names Thes e dat aitem s specif

y th e pat h name s t o be use dwhe n openin g th e dat afiles containin

g vapo r generatio n tables
. Thes e dat atable s ar e describe din Sectio n 2-c , "Vapo r Generatio n Table " below , an dth e forma t o f thi s dataite

mi n Section III-C , "Inpu

t Dat a Preparation. " k ) EventDat

a Fil e Nam

e Thi s dataite

mspecifie d th e pat h nam e t o b e usedwhe

n openin g the input file containing even t data
. Thi s inpu

t file i s describedi

n Sectio n 3 , "Even tData " below , etc . 1 ) Lo g Outpu

tFil e Nam

e Thi s dataite

mspecifie s the pat

h nam e to b e usedwhe

n openin g th e output

fil e tha t i s t o contai n adetailed lo g o

f simulatio n results
. Thi s outpu

t file i s describedin Sectio

n III-C-2 , "Outpu tDescription. " Se

e als o th e description o

f the Plotfla

g keywor dcontaine d in Section III-B-1 , "Inpu

tDat a Preparation. " m ) Plo tOutpu

tFil e Nam

e Thi s dataite

mspecifie s th

e pat h nam e t o b e usedwhe

n openin g the outpu

t file tha t i s to contain caniste

r loa d versu s time data
. Thi s outpu t file i s describe di n Section III-C-2 , "Outpu tDescription. " Se

e als o the description o

f the Plotfla

g keywor dcontained in Section III-B-1 , "Inpu

tDat a Preparation. " n ) Purge Typ e Fla g Thi s dataite

mspecifie s the purg e contro l strategy t o b e useddurin g simulations
. A s distributed , th

e P T mode l contain s asingle purg e contro l strateg y model , as described i

n Section II-C-3-c , "Getpurge, " whic h i s selectedb

y specifyin

g avalu e o

f zer o fo r th e purg e typ e fla

g dat aitem
. I f additional , user-suppliedpurg e contro l model s ar e added , a s describe d in Section III-D , "Progra m Generation and Modification, " the y ma y b e selected b y specifyin g value s o f -1 , -2 , etc . fo

r thi s dat aitem
. Furthe

r detail s ca n b e foun d i n Sectio n HI-D . o ) Caniste r Purge Curv e Typ e Thi s dataite

mspecifie s i

f th e caniste r purg e curve i s t

o b e specifiedb

y asingle tabl e o

f purg e curv e values , o r

b y a n analytica

l functio n tha t generate s afamil

y o f loading

dependen t purg e curves . Eac

h o f thes e option s ar

e describedbelow i

n Section II-B-3-h , "Dopurge. " Th e valu e specifie da s the purg e curv e typ e determine s how datai n th e caniste r purg e tabl e i s interpretedan dth e expecteddat

aforma t o f the associateddat

afile. Se e Section II-B-2-b , "Caniste r Purg e Table. "-P.1 3



### p ) Caniste r Load Mode l Fla g Thi s dat aite mspecifie s th

e mode l t o b e use d t o carr y out caniste r loading calculations , an

d mode l parameters , i

f needed
. Option s available includ e treating caniste

r loading behavio

r as eithe r idea l o r non-ideal
. Idea

l caniste r loading calculation s assum e tha t hydrocarbon vapors ar e completel

y capturedu

p t o caniste r breakthrough , an

dtha t n o additiona

l caniste r capacit y exist s beyond th e breakthroug h point
. Non-idea

l caniste r loadin g calculation s charcoa l efficiency , whic

h become s slightl

y les s tha n 100.0 % a s breakthroug

h loadin g i s approached , bu

t remain s non-zer

o a t caniste r load s well beyon

dth e breakthroug

h point
. Eac h o f thes e mode

l option s ar

e describedfurthe

r in Sectio n II-C-3-h , "Dopurge. " q ) Back-purg e Flo w Rat e Thi s dataite

mspecifie s the quantit

y o f vapo r tha t i s draw n throug h th e charcoa

l caniste r an d int o the fue l tan k in respons e t

o fue l tan k temperatur e decreases
. Unit s o

f thi s valu e ar e ft^(gallo n tan

k capacity)/°F
. Physica

l phenomeno

n tha t shoul db e accountedfo

r b y value s specified fo

r thi s dataiteminclude th e reductio n i n vapor volum e andcondensatio n o

f hydrocarbo

n vapors , bot

h a s afunctio

n o f decreasin g temperature . The comment s mad e i n Sectio n e above regarding vehicle dependence o f diuma l caniste r load s als o appl

y t o back

purg e floe rate values
. Back-purg e calculatio n detail s ar e includedi n Section II-C-3-h , "Ptbkpg. " 2 ) Tabular Dat

a Tabula r dat aitem s consis t

o f table s o f dat atha t describ e adriving schedule o r behavio r o f vehicl e components . Th e thre e type s o f table s neededb

y the P T mode l includ e adriv e schedule , acaniste

r purg e curve table , an

don e or mor e vapo r generation tables
. Th

e first tw o o f thes e ar e independen

t o f vehicl e andfue

l characteristics , whil e th e latte r dat afile depends on fue

l characteristic s an

d t o asmal l exten t o n vehicl e characteristics
. Eac

h tabula r dat atable neede

d by the P T mode l i s describe

dbelow
. a ) Driv e Schedul e Tabl e Thi s datatabl e describe s th e velocitie s in MPH , an daccelerations , i n MP

H pe r second , a t eac h unit time interva

l o f the driv e schedul

e to b e simulatedb

y th e PT model
. Th

e tabl e consist s o f thre e columns , one eac

h fo r time , velocity , an

dacceleration
. Thes e datashoul d b e available fo

r the desire d driving schedul

e o n asecond-by-secon

dbasis , wit

h eac h tabl e ro w consistin g o

f asingl e set

o f observations
. Th e numbe

r o f datarow s i n th e table , therefore , shoul

d b e equa l t o th e drivin g schedul e lengt h i n seconds
. b ) Caniste r Purg e Tabl e Thi s datatabl e contain s value s tha t eithe r explicitl y or implicitl y specif y the caniste

r purg e curve , depending o

n whethe r th e caniste r purg e curve typ e flag specifie s us e o f atabula r purg e curve , o r

a n analytica

l purg e curve . Bot

h approache s contai n information tha t describe s purg e behavio

r o f th e carbo n caniste r t o b e simulated , an

dtha t allo w calculation o f th e quantit y o f hydrocarbon s remove

dfro macaniste

r versu s volum

e o f purg e air
. Whe n th e caniste

r purg e curve i s t o b e specifie dexplicitl y i n tabula r form , th e dat

atabl e consist s o f tw o columns , on

e fo r volum e o f purg e air , in standar

dcubi c feet , an

don e fo r th e cumulativ e quantit

y o f hydrocarbon s purged , in grams . I t i s assumedtha

t th e caniste

r purg e tabl e contain s datanormalize dt o describ e a1.01
. canister
. Whe n th e caniste

r purg eP.1 4

curv e i s t o b e specifie danalytically , th e dat atabl e consist s o f aset o f mode l constants , a s describe di n Sectio n III-B-2-b , "Caniste r Purg e Table. " c ) Vapo r Generatio n Tabl e Thi s dat atabl e describe s th e vapo r generatio n characteristic s o f afue l tank durin g vehicl e operation , an dcontain s dat adescribin g th e cumulativ e mas s o f hydrocarbon s generate d durin g adrive , an do n instantaneou s volumetri c flo w rat e at whic h vapor s are generated
. Th e tabl e consist s o f

thre e columns , on e fo

r tim e sinc e th e star

t o f adriv e i n minutes , on e for cumulativ e mas s o f

hydrocarbon s generate d sinc e th e star t o f adrive , i n grams , and on e for vapo r generatio n rate , i n standar d cubi c feet pe r minute
. Dat ai n thi s tabl e mus t b e normalize dt o abasi s o f

a1. 0 gallo n fue

l tan k wit h a n appropriatel y scale d vapo r headspac e volume
. Care mus t

b e take n tha

t th e headspac e volum e a s apercent of liqui d capacit

y i s th e same in vapo r

generatio n table s a s i n th e vehicl e t o b e simulated
. A vapo r generatio n tabl e depend s o n bot h fue l volatilit y an d o n th e time/temperature profil e o f th e driv e t o b e simulated
. Simulatio n o f mos t tes t procedure s require s vapo r generatio n table s for tw o temperatur e range s pe r fue l RVP , an d simulatio n o f in-us e drivin g pattern s ma y requir e thre e suc h tables , th e maximu mnumbe r currentl y provide d for

b y th e P T model
. 3 ) Even tDat a Even t dat ai s use da s asourc e o f inpu t b y th e mode l t o determin e th e sequenc e an d characteristic s o f

events that

asimulate d vehicl e wil l experience
. Event s tha t can b e simulate dinclud e diuma l hea t builds , hotsoaks , drivin g sequences , an d back-purg e cycles
. I n th e event

file, event s ar

e specifie d b

y akeywor

d tha t identifie s th e desire d event , an don e o r mor e optiona l parameter s tha t specif y o r modif y even t characteristics
. Parameter s associate dwit

h diurna l an dhotsoa

k event s adjus t

simulate d emission s t o simulat e an y desire ddiurnal temperature rang e an d hotsoa k temperature . Althoug h onl y asingl e drivin g schedul e i s supported , thi s driv e ma y b e simulate d fo r u p t o thre e ambien t temperature/initia l fue l temperatures , an d parameter s associate d with driv e even t specificatio n allo w an y portio n o f th e driv e schedul e t o b e simulated
. Thi s sectio n describe s ho w eac h of

thes e event s i s describe d i n the event

file. a ) Diurna l Event s Diurna l event s are specifie db y th e "diurnal " keyword
. A singl e optiona l paramete r i s allowe dt o permi t

simulatio n o f

diurna l events a

t temperature s differin g fro mthos e associate dwit

h th e bas e diuma l caniste r load a s describe d in Sectio n II-B-l-e , "Diurna l Caniste r Load. " I

f thi s paramete r

i s omitted , o r

avalu e of

-1. 0 i s specified , th e diuma l caniste r loa duse dt o simulate d th e diurna l i s exactl y a s specifie d by th e bas e diurna l caniste r loa ddat aitem
. I

f apositive , non-zer o paramete r i s given , th e diurnal load use d for simulatio n i s th e bas e diurnal caniste r load multiplie d b y th e valu e o f th e parameter . Not e tha t th e bas e diurnal caniste r

load i s alway s scale d t o th e simulate d vehicl e fue l tank size , a s describe di n Sectio n II-B-l-e , in additio n to an y scalin g specifie d b y adiuma l even t parameter . In equatio n form , thi s ca n b e expresse d as : Actua l Diurnal Caniste r

Load = Bas e Diurnal Caniste r Loa d * Fue l Tan k

Siz e * Diuma l Even t ParameterP.1 5



### Example s o

f diuma l events in a

n even t file ar e show n below
. diuma l - 1 diurna l 2.7 7 b ) Hotsoa

k Events Hotsoa k event s ar e specifiedb

y the "hotsoak " keyword
. A single optiona l paramete r i s allowe d to permit

simulatio n o

f hotsoa k event s a t temperature s differing fro

mthos e associated wit

h the bas e hotsoa

k caniste r loa da s describedi

n Section U-B-l-f

, "Hotsoa k Canister Load. " I

f thi s paramete

r i s omitted , o

r avalu e o f -1. 0 i s specified , the hotsoa k caniste r load used to simulatedth

e hotsoa k i s exactl y a s specifiedb

y th e bas e hotsoa

k caniste r loa d dataitem
. I

f apositive , non-zer

o paramete r i s given , th e hotsoa

k loa d used fo r simulation i s the bas e hotsoa k caniste r loa dmultipliedb

y the valu e o

f the parameter . Not e tha t th e bas e hotsoa

k caniste r loa di s alway s scale

dt o th e simulatedvehicl e fue

l tan k size , a s describe d i

n Section II-B-l-f

, in addition to an

y scaling specifiedby ahotsoa k even t parameter . I

n equatio n form, thi s ca

n b e expresse

das : Actua l Hotsoa k Caniste r Loa d= Bas e Hotsoa

k Caniste r Loa d* Fue l Tan k Size * Hotsoa k Even t Paramete r Example s o

f hotsoa k events in a

n even t file ar e show n below
. hotsoa k - 1 hotsoa k 1.46 c ) Driv e Events Driv e event s ar

e specified b

y on e o f th e keyword s "drivel, " "drive2, " o r "drive3. " A keywor d o f "drive " i s als o accepted , an d i s processeda s a"drivel " event . U p to tw o optiona l parameters ar

e allowe dt o indicat e tha t onl y aportion o

f a n entir e drivin g schedul e i s to b e simulated , or

t o star t asimulate ddrive wit h elevatedfue

l temperature . Eac

h o f th e thre e driv e even

t keyword s appl

y t o th e singl e driv e schedul e specifie db y th e driv e schedule tabl e describe d i

n Section II-B-2-a , "Driv

e Schedule Table. " The ambien t temperature/initia

l fue l temperatur

e a t whic h simulatio n o f thi s drive i s to b e performe

d i s give n b y whic h o f th e three keyword s i s used
. The "drivel " keywor di s usedto simulat

e a driv e whos e fue

l temperatur

e profile , an

dhenc e runnin

g los s vapo

r generation profile , i s describe d by th e vapor

generation tabl e associate dwit h the vaporfile l dataitem
. (Se e Sectio n II-B-2-c , "Vapo

r Generatio n Table, " an d Sectio n III-C , "Dat a Tabl e Preparation." ) Similarly , the "drive2 " keywor di s associatedwit

h th e vaporfile 2 data item , an d the "drive3 " keywor

d i s associate

dwit h th e vaporfile 3 dat

aitem
. U p t o tw o optiona

l parameter s ma

y b e specifie

dt o allow simulation o

f apartia l driv e schedule , or

to simulat e drive s startin

g wit h a n initia l fue l temperatur

e abov e the initia l fue l temperatur e o f th e associate dvapo

r generatio n table
. Th e first o f thes e parameter s indicate s the lengt

h o f the driv e t

o b e simulated , i

n tim e unit s equa

l t o thos e usedin the drive schedul

e table (usuall

y seconds)
. Th

e secon d paramete r indicate s th

e numbe r o f drive tabl e entrie s tha

t woul d hav e t o hav e bee n simulate di n apreviou s drive whil

e followin g the current vapor generatio n tabl e temperatur e profil e t o reac h th e desire dinitial fue l temperature . Th e driv e star t tim e is , therefore , th e point

i n tim e a t whic h th e vapor generation tabl e i s entered a t th e star t o f th e simulateddrive
. Not

e tha t the driv e tabl e i s alway s entere d fro

mit s beginning ; it

i s no t possibl e t o begi n adriv e simulation par

t wa y throug h adrive schedule
.P.1 6

Defaul t value s ma

y b e use dfor

bot h optional parameters . I

f value s for

neithe r paramete r ar e given , th e defaul t

actio n i s t o simulat e a

n entir e driv e usin g atemperatur e profil e correspondin g t o th e start o f th e associate d vapo r

generatio n table
. Paramete r value s o f -1. 0 ma y als o b e use dt o selec t

thes e defaults
. I

f onl y on e paramete r

i s given , th e defaul t actio n i s t o simulate adriv e whos e lengt h i s equa l to th e valu e o f

th e give n parameter , usin g adefaul t temperatur e profil e a s describe d above
. I f tw o parameter s ar e given , bot h th e driv e lengt

h an dth e vapo r

generatio n tabl e entr

y poin t ma y b e modified
. Not e tha t i f a non-defaul t

temperature/vapo r

generatio n profil e i s desired , i t i s necessary t o provid e value s for bot h parameters ; i

f desired , avalu e of

-1. 0 ma y b e give n fo

r th e firs t paramete r a s aplac e holder

tha t select s adefaul t

o f simulatin g afull-lengt

h drive
. Show n belo w are severa l example s tha

t illustrate us e of

parameter s wit

h driv e entrie s i n a

n event file. Exampl e 1 drive 2 Thi s entr y specifie s adriv e tha t follow s th e temperatur e profil e give n b y th e vapo r generatio n tabl e associate dwit h th e "vaporfile2 " dat aitem
. Th e entir e driv e describe d b y th e driv e schedul e tabl e i s simulated
. Exampl e 2 drive 2 50 5 Thi s entry specifie s adriv e tha t follow s th e sam e temperatur e profil e a s describe d i n Exampl e 1 above
. Th e simulate d drive , however , proceed s onl y throug h th e first 50 5 driv e tabl e entries
. If

th e driv e tabl e contain s entrie s a t time interval s o f

seconds , thi s exampl e might

b e use dto simulat

e bag 3 o f a n FT P test . Exampl e 3 drive 2 50 5 153 7 Thi s entry specifie s adriv e tha t follow s th e sam e temperatur e profil e a s i n th e previou s examples , excep t

tha t th e temperatur e profile/vapo r generatio n tabl e i s entere d a t apoin t conespondin g t o th e fuel temperatur e tha t woul d b e observe d afte

r 153 7 second s (more precisely , time unit s o f

driv e schedul e tabl e entries ) hadelapse d i n adriv e wit h initial fuel temperature equa

l t o tha t o f th e firs t vapo r generatio n tabl e entry . Th e lengt h o f th e driv e i s 50 5 seconds
. Th e temperature profile s followe d b y thi s hypothetical driv e an d th e driv e t o b e simulate di n thi s exampl e ar e illustrate d i n th e followin g figure b y th e portio n o f th e curv e extendin g from99. 0 ° F t o 103. 0 °F :



### 1 0P.1 7

Figur e 1 Sampl e Temperatur

e Profil e

80. 0 0. 0 10.0 20. 0 30. 0 Tim e (min. ) 40. 0 50. 0 60. 0
Exampl e 4 drive 2 - 1 153 7 Thi s entr y i s identical to tha

t i n Exampl e 3 above , excep t tha t aful l lengt h driv e i s simulate d instea do f onl y th e first

50 5 second s o f

th e ful l drive
. d ) Back-Purg e Event s Back-purg e event s are specifie d b y th e keyword "backpg. " A singl e require d paramete r specifie s th e decreas e in fue l tan k temperature tha

t i s t o b e modelle d durin g th e even t Th e actua l caniste r

purg e volum e associate d wit h bac k purg e events i s calculate d fro mth e specifie dtemperature change , th e fue l tank size , an d th e back-purg e flo w rat e give n b y th e back-purg e flo w dat e scala r dat aitem , describe d i n Sectio n II-B-2-q , "Back-purg e Flo w Rate , a s follows : Back-purg e vol
. = (Back-purg e Flo w Rate ) * (Tan k Volume ) * (Deltat) wher e Deltat

i s th e desire dtemperature change
. Becaus e th e P T mode l doe s no t explicitl y accoun t for fue l tank temperatures , i t

i s up t o th e user

t o specif y a n appropriat e back-purg e even t paramete r

s o a s t o maintai n temperature continuit y betwee n event s an d ove r multipl e day s tha t ar e simulated
. A

n exampl e of

aback-purg e event

i n a n even t dat afile is : backp g 12. 0 Thi s entry specifie s tha

t a n even t characterize d b y adecreas e i n fuel tan k temperatur e o f 12. 0 ° F i s t o b e simulated
.

1 1P.1 8

C ) Mode l Operatio n an d Structur e Thi s sectio n describe s th e P T mode l frombot h a n operationa l an d astructural viewpoint
. Sectio n 1 , "Mode

l Operation, " discusse s th e calculatio n sequenc e use d b y th e mode l i n genera l an dt o simulat e specifi c evaporativ e emission s event s i n particular
. Sectio n 2 , "Mode l Structure, " present s th e structura l organizatio n of th e P T model , an d ho w it s constituen t

module s relate t o on e another
. Thi s sectio n i s o f mos t interes t t o thos e wishin g t o modif y progra mcode
. Finally , Sectio n 3 , "Componen tDescription, " contain s detaile ddescription s o f

individua l programmodule s an d thei r specifi c functions
. Onl y module s direcd y related t o evaporativ e emission s aspect s o f th e mode l are discussed
. Other modules , relate dt o supervisor y contro l an d dat ainpu t

functions , ar e no t

describe d i n th e interes t o f simplicity , a s knowledg e of thes e component s i s no t

necessar y t o us e o r

modif y th e model
. 1 ) Mode l Operatio n Operatio n o f

th e P T mode l ca

n b e divide d int o thre e key phases
. Th e firs t o f thes e i s one tim e initializatio n an dinpu t of bot h scala r an d tabula

r data , a s describe d i n Section s II-B- 1 an dU-B-2 , respectively
. Th e secon d phas e i s readin g o f individual evaporativ e emission s event s fromth e even t

dat afile, extractin g applicabl e parameters , an d transfer o f simulatio n contro l t o module s responsibl e for modellin g o f

thes e events . Th e final phas e i s even t processin g an ddisplay o f

outpu t fromindividual even t

simulations
. Th e secon d an d thir d o f thes e processin g phase s are repeate d for eac h entr y i n th e even t

dat afile
. Th e flow o f contro l amon g thes e event s i s illustrate d i n Figur e 2
.



### 1 2P.1 9

Figur e 2 Rea d dat a& Perfor m initializatio n 

### P T Mode l

Operationa l Flowchar t

Rea d even t dat a

Proces s back

purge events ^Determines
.

\even t type / Proces s drive

even t 

## I Calculat e tri p lengt h Proces s diurna

l an d hotsoa k events Calculat e back

purge volum

e Calculat

e diurna l o r hotsoa k loa d Perfor mcaniste r purge calculation s Calculat e spee d & acceleratio

n Repea

t fo r all tri p table entrie s Calculat e purg e rat e Ad d calculate d loa dt o caniste r 

### X

Calculat e vapo r generatio n rat e Fin d ne t load/purge & updat e caniste r ca m Calculat e fue l rat e & fue l fro mcaniste r Outpu t even t result s

En d o f simulatio n I n th e dat ainpu t

processin g phase , a n inpu t dat afile i s rea d whic h contain s al l scala r inpu t data , a s describe d i n Sectio n II-B-a , alon g wit h th e name s o f dat afile containin g tabula r an deven t

data
. Next , check s ar e mad e o n scala r dat aitem s t o insur e al l require d value s hav e bee n specifie dan d tha t the y ar e withi n reasonabl e ranges . Interna l storag e i s the n

1 3P.2 0

allocate dfo

r dat atables , an dinternal initializatio n performed
. Finally , informatio n from eac h of th e tabula r dat afile s i s readan d store d internally
. In th e even t

inpu t phase , even t

entrie s ar e read , alon g wit h associate d parameters , a s describe di n Sectio n II-B-3 , "Even tData. " Al l driv e event s are passe d t o th e Ptdriv e modul e fo r processing , whil e diuma l an d hotsoa k event s are passe d t o th e Ptdih s module , an dback-purg e event s ar e passe d t o th e Ptbkp g module
. N o checkin g i s performe d on even t parameter s at

thi s stage . Event s continu e to b e read an d simulate d unti l al l event s in th e specifie deven t

dat afile hav e been processed
. Diuma l an dhotsoa

k event s ar e processe d i n asimila r fashio n b y th e Ptdih s module , wit h th e primar y differenc e betwee n the mbein g th e basi c emissio n rat e use d for each
. Fo r

bot h events , th e appropriate emissio n rat e i s obtained , an d correcte d t o accoun t fo r fue l tan k siz e an dfor th e even t multiplie r

containe d i n th e even t

dat afile. Th e resultin g uncontrolle d hydrocarbo n emissio n valu e i s the n adde d t o th e caniste r throug h us e o f

th e Dopurg e module , thu s updatin g th e caniste r state . Furthe r

detail s are containe d i n Section s II-C-3- a an dH-C-3-h
. Driv e event s are processe db y the Ptdriv e module
. A t the star t o f eac h driv e simulation , th e star t time relative t o th e beginnin g o f th e specifie d driv e schedul e an d th e driv e lengt h ar e determine dfromparameter s associate d wit h th e driv e even t

specification
. Next , eac h entr y i n th e driv e tabl e include di n th e driv e i s processed
. Fo r eac h driv e tabl e entry , vehicl e spee dan dacceleratio n i s calculated , alon g wit h caniste r purg e rate , th e fuel tank

vapo r generatio n rate , an dth e ne t chang e in caniste r

load ove r th e interva l betwee n driv e tabl e entries
. I n addition , value s fo

r th e quantit

y of fue l require d b y th e engin e an d th e percen t of thi s fue l provide db y caniste r purg e vapor s ar e als o calculated
. After al l driv e tabl e entrie s hav e bee n processed , atri p summar y i s displayed
. Furthe r

detail s are containe d i n Sectio n II-C-3-b
. Back-purg e event s ar e processe d b y th e Ptbkp g module
. Thi s even t i s processe d b y calculatin g th e volum e o f

purg e ai r tha t passe s throug h th e caniste r durin g di e event , the n performin g caniste r

purg e calculation s in amanne r identica l t o tha t

use d t o carry out caniste r purg e calculation s durin g driv e events . Furthe r detail s ar e foun d i n Sectio n II-C-3-i
. 2 ) Mode l Structur e Thi s sectio n describe s th e overal l structur e of th e P T model , an d ho w th e component s o f th e mode l relat e t o on e another
. Knowledg e o f thi s structure i s no t

strictl y necessar

y t o us e o r understan dth e model , but i t ma y b e usefu l if th e mode l i s t o b e expande d o r modified
. Figur e 3 belo w illustrate s th e P T mode l structure i n term s o f it s highest-leve l components . Th e algorithm s upo n whic h eac h o f thes e component s are base d ar e describe d belo w in Sectio n 3 , "Componen tDescription. "



### 1 4P.2 1

Figur e 3 

### Caniste r Model Progra m Structur e Purge ! 'es t

GetFil e Gprdke y Ptchec k
Ptini t Ptdsp O Read_dat a Doi t

Rdev t

Display_dat a Ptdi

Pth s Ptbkp g
Ptdriv e DoPurg e

GetSpee d GetH p GetPurg e GetVp r Thi s diagra

mshow s tha

t th e mode l structure consist s o f five levels
. Th e first

of thes e i s th e modul e labele dPurgeTest , whic h supervise s readin g o f al l inpu t dat aan d dat atables , mode l initialization , dat avalidation , an d displa y of inpu t data
. Thi s modul e make s us e o f subordinat e module s i n th e secon d level , suc h a s GetFile , Gprdkey , Ptcheck , Ptinit , PtdspO , an dRead_data
. PurgeTes t i s als o responsibl e for

startin g th e actua l simulatio n calculation s by callin g on Doit , an d fo r displayin g final result s throug h Display_data
. Th e second-leve l modul e Doi t i s responsible fo

r supervisin g the processin g o f eac h event

in th e even t dat afile. Thes e events , an d thei r associate d parameters , are rea d b y th e Rdev t module
. Afte

r eac h even t

i s read an d it s typ e determined , Doi t call s upo n on e o f

th e third

leve l module s Ptdi , Pths , Ptdriv e o r Ptbkpg , a s appropriate , t o carry ou t th e necessary calculations
. Eac h o f

thes e thre e module s mak

e us e of th e fourth-leve l modul e DoPurg e t o carry ou t caniste r loadin g andpurgin g calculations 1

. Ptdriv e als o make s us e o f several fourth-leve l module s t o perfor mcalculation s associate d wit h determinin g vehicl e spee d and acceleration , engin e horsepowe r output , purg e flow rate , an d fue l tank vapo r flow rates . Module s use dfo

r thes e purpose s includ e GetSpeed , GetHp , Ge t Purge , an d Getvpr
. iTh e module(s ) use dto carry ou t diurnal an dhotsoa

k calculation s ar e referre d to a s eithe r Ptdihs , o r

a s Ptd i an dPths
. Th e Ptd i an d Pth s module s ar e actuall y entry point s i n th e Ptdih s module , sinc e man y o f th e calculation s neede db y thes e tw o module s ar e identical
. Fro mafunctiona l viewpoint , Ptd i an d Pth s ca n b e considere dt o b e separat e a s indicate d b y th e diagramabove , eve n thoug h fromaprogra mstructur e viewpoint , the y ar e reall y subordinat e component s of Ptdihs
. 

### 1 5P.2 2



### A numbe r o f othe r module s no

t describedher

e ar e als o use db y th e P T model ; these , however, ar

e associate d wit h low-leve l dat ainpu t or progra mcontrol , an

dar e no t describe d i n mi s document
. 3 ) Componen t

Descriptio n Thi s sectio n describe s eac

h o f th e computationa

l module s presentedabove i n Sectio n 2) , alon g wit h the computationa

l algorithm s upo

n whic h the y ar e based
. Module s tha

t ar e described her

e ar e limited t o thos e directl

y wit h simulation o

f vehicl e components an

d operation
. Othe

r modules , suc

h as thos e associatedwit

h periphera

l functions , suc

h a s supervisor y o r input/outpu

t tasks , ar e no t documented
. a ) Ptdih s Thi s modul e processe s bot h diurna l an dhotsoa k events , includin g calculatio n o f uncontrolled vapo

r generation an

dchange s i

n caniste r loading
. Fo

r diurna l events , th

e basi c quantit

y o f hydrocarbon s generatedduring th e even t i s obtainedfro

mthe Diuma

l scala r inpu t dat aitem , a s describedi

n Sectio n II-B-l-e , "Diurna

l Canister Load. " Fo

r hotsoa k events , th e corresponding value i s obtainedfromth e Hotsoa k dat aitem
. Thes e value s ar e the n adjuste d fo r fue l tan k size , an dth e fue l tan k an dambien t temperature s a

t which the even

t occurs , a s describe di

n Section II-B-3 , "Even

tData. " Next , the corrected hydrocarbo

n generatio

n valu e i s passe dt o th e Dopurge module , whic

h performs th e actua l caniste r loadin g calculations
. Thes e calculation s includ e updating the caniste

r load , an d determining the amount , i f any , o f hydrocarbon s vente ddurin g the event . Finally , asummar

y o f hydrocarbon s generate

ddurin g th e event , th e fina l caniste r state , an d th e hydrocarbon s vente

d i s displayed
. b ) Ptdriv e Thi s module processe s driv e events , includin g interaction s betwee n fue l tan k vapor generation , caniste

r purge , an ddrive characteristics
. Thi s calculation procedur e use d t o carr y ou t drive simulatio

n i s as follows : 1 ) Determin

e th e star t an den dtimes , relative t

o th e star t o f th e driv e define

db y th e drive schedule table , fromeven t file parameters as describedi n Sectio n II-B-3-c , "Driv e Events. " Initializ e th e curren t simulation tim

e t o th e initia l driv e tabl e entr y o f th e drive t o b e simulated
. 2) Determin

e th e curren t vehicl e spee dan dacceleratio

n throug h th e Getspee dmodule
. Spee d i s returned i

n MPH , an dacceleratio

n i n MPH/second
. Calculat

e tota l mile s traveled i n th e drive b y integratin g velocit y usin g Euler' s method
. 3 ) Calculat

e th e horsepowe

r requiredb y th e curren t vehicle spee

dan dacceleration , usin g th e Geth p module
. Als o calculat

e th e rat e o f fue l consumption , i

n pound s pe

r second , require

d b y thi s powe

r level , usin g th e Geth p module
. 4 ) Determin

e th e volumetri

c flo w rate , i n SCF/minute , o

f caniste r purge availabl

e from th e engin e base d o n th e curren t vehicle spee

dan dacceleration , usin

g th e Getpurg e module
. I f th e curren t simulation time i s les s tha n th e specifiedcaniste

r purg e delay , a s describe d i

n Section II-B-l-g , "Purg

e Delay, " se

t thi s purg e rat

e t o zero .
1 6P.2 3

5 ) Determin e th e quantity , in grams , an d flow rate , i n SCF/minute , o f hydrocarbo n vapor s generate di n th e fuel tank ove r th e uni t time interva l startin g a

t th e curren t driv e simulatio n time. Thi s valu e i s obtaine d b y th e Getvp r module , usin g th e vapo r generatio n tabl e correspondin g t o th e curren t driv e type . Se e Sectio n II-B-3-c , "Driv

e Events. " Adjus t

bot h of thes e quantitie s for

th e fue l tank siz e of th e simulate dvehicle
. 6 ) Calculat e th e ne t

purg e flow rate throug h th e caniste r a s th e differenc e betwee n th e availabl e purg e rate found i n 4 ) above , an d th e fue

l tank vapo r flow rat e found in 5 ) above
. Thi s calculatio n assume s tha t th e purg e syste mi s configure d a s show n below : I f th e ne t caniste r purg e i s les s than zero , the n caniste r loadin g wil l occur ; otherwise , hydrocarbon s wil l b e purge d fromth e canister
. Caniste r loadin g i s processe da s follows : First , fue l tank hydrocarbo n vapor s are apportione d betwee n th e engin e an dth e caniste r i n th e sam e ratio a s th e availabl e purg e rat e fromth e engin e t o th e fue l tan k

vapo r generatio n flo w rate . Next , thi s quantit y o f hydrocarbon s ar e loade d t o th e caniste r by th e Dopurg e module
. Finally , th e amoun t o f hydrocarbons , in pounds , availabl e t o th e engin e a s unmetere d fuel from th e fuel tank

i s calculated
. Thi s quantit y i s found fromth e differenc e betwee n fuel tank vapo r generatio n and th e amount of hydrocarbon s loade d t o th e canister
. Fo r caniste r purge , th e followin g calculation s ar e performed
. First , th e tota l purg e volum e i s determine db y multiplyin g th e ne t purg e flo w rate , i n SCF/minute , b y th e interva l width , normall y on e secon d o r 1/6 0 minute
. Then , th e Dopurg e modul e i s use dt o carr

y ou t caniste r purg e calculations
. Finally , th e amoun t o f hydrocarbon s availabl e t o th e engin e a s unmetere d fue l i s calculate d a s the su mo f fue l tan k vapor s an dvapor s purge dfromth e canister
. 7 ) Calculate th e percen t

o f engin e fue

l requirement s provide d b y unmetere d fuel from th e canister

alone , an dfro

mth e canister

an d fue l tan k combined
. 8 ) Writ e entrie s t o bot

h th e plo t file an d t o th e lo g file, if

specifie d b y th e appropriat e Plotflag dat aitem
. 9 ) Continu e wit

h 2 ) abov e unti l al l entrie s i n th e driv e tabl e hav e been processed
. At th e en do f

adriv e simulation , asummar y o f total tri p data , vehicl e performance , an d evaporativ e emission s i s displayed
. c ) Getpurg e Thi s modul e determine s th e availabl e purg e flow rat e t o th e engine
. Purg e rat e can b e calculate dfroma

n interna l algorithm , a s describe d below , o r fro mauser-supplie d algorithm , a s describe di n Appendi x B
. Usin g th e interna l algorithm , purg e rag e i s proportional t o engin e power , a s follows :



### 1 7

### I f speed < 2. 5 mp

h the n purg e = 0. 0 els e i f acceleratio n > 3. 5 mph/s/

s or acceleratio n < 0 the n purg e = 0. 0 els e { h p = horsepowe

r a t curren t velocit y an dacceleratio

n max_h p = horsepowe

r a t 60. 0 mp h cruis e min_h p = idle horsepowe

r k l = max_purge*(hp-min_hp)/(max_hp-min_hp) k 2 = max(1.0-(2./9.)*accel , 0.10 ) purg e = k l * k2 } 

### Whe n th e vehicle i s belo

w aspecifie

dvelocit y (2. 5 mph) , o

r decelerating , n o purg e occurs . Otherwise , purg e i s proportiona l to horsepower , multiplie db y a n empirica

l correctio n factor , k2 , tha

t accounts fo

r th e reducedmanifol

dvacuu mavailable during acceleration
. The notation show

n above fo r th e calculation o

f k 2 indicate s th e followin

g steps : First , calculat e the quantit

y 1.0-(2/9)*accel
. Next , compar e thi s valu e t o 0.10 , an

dselect th e algebraicall y large r value a s the resul

t t o b e take n a s th e value o f k2
. d ) Getspee d Thi s module determine s the vehicl e spee dan dacceleration a

t aspecifiedtim

e during a drivin g cycle
. Thes e dataar e obtaine db

y tabl e looku

p i n th e driv e tabl e describe d in sectio n II-B-2-a , "Driv

e Schedule Table. " Vehicl e speed , in MPH , i s determine d a s th e averag e speed ove

r th e tim e interva l define db y the specifie

dtim e andthe tim

e o f th e nex t sequentia l driv e tabl e entry , i

f any . Acceleration , i

n MPH/second , i s determined by th e change i n velocit y ove r thi s interva

l divide db y th e interva l width
. e ) Geth p Thi s modul

e determine s th

e horsepowe

r require dto mov e avehicle a

t aspecifie dspee d an d acceleration
. The followin

g empirica l correlation i s usedto obtai

n the desire dhorsepowe

r value : horsepowe

r = k 4 + ki*spee d + k2*speed

^ + k3*speed*acceleratio

n Th e fou r constant s i n th e above correlatio n ar e selectedo n the basi s o

f vehicl e weight
. Suggeste d value s ar e show n below : Vehicl e weigh t 2,50 0 lbs
. 4,000 lbs
. k l

0.007 0.01 0 k

2 0.003 8 0.005 5 

## k a

0.33 4 0.48 6 k

4 0.85 0 0.75 0 f ) Getfue

l Thi s module determine s the rat e o f fue l consumption , i

n pound s o

f fue l pe r second , o f a vehicl e a t agive n powe r output , a s providedb

y Gethp
. Thi s calculation , show n below , i s asimple conversion tha

t include s the energ

y conten t o f gasoline (1864 6 BTUAbm) , an d engin e therma l efficienc y (take n as 28. 0 %)
. 1 8P.2 5

Fue l rate = horsepower * 2,544,98 7 BTU / 3,600. 0 sec , /

18,464 , BTU horsepowe r

hr
. hou r

lbm
. g ) Getvp r Thi s modul e determine s th e fue l tan k vapo r generatio n rat e at

th e curren t

time in adrivin g cycle , usin g aspecifie dvapo r generatio n table , describe d i n sectio n II-B-2-c , "Vapo r Generatio n Table. " Th e mas s of hydrocarbo n vapor , i n grams , generate d ove r aon e secon dinterval startin g a

t th e specifie d time i s foun

d fro mth e vapo r

generatio n table , alon g wit h th e volumetri c vapo r

flow rate , i n standar

d cubi c fee

t per minute
. h ) Dopurg e Thi s modul e carrie s ou t

caniste r loadin g an d purgin g calculations , wit h option s availabl e fo r eac h tha t diffe r accordin g t o th e simplifyin g assumption s tha t are incorporate d int o each
. Loadin g mode l selectio n i s mad e throug h th e cantyp e scala r dat aitem , whil e th e purg e mode l i s selecte db y th e pcurvetyp e dat aitem , bot h o f whic h ar e describe d i n Sectio n II-B- 2 an dbelow
. Al l model s ar e base d o n experimenta l dat atake n unde r conditions s typicall y encountere db y evaporativ e emission s contro l systems . Th e P T mode l assume s tha t onl y charcoa l typ e difference s are significant betwee n canisters , an d tha t canister s o f differin g siz e bu t

identica l adsorben t

exhibi t performanc e proportiona l t o size
. Caniste r loadin g an dpurgin g model s are describe d below
. Canister Loadin g Model s Tw o caniste r

loadin g model s are available , selecte d b y th e cantyp e inpu t dat aitem
. Th e forma t an dvalue s expecte dfo

r thi s ite mar

e describe d belo w in n Sectio n III-B-1 , "Inpu t Dat a Preparation. " Th e simples t loadin g mode l i s base d o n a n assumptio n o f

idea l caniste r adsorptio n behavior
. Durin g caniste r loading , th e caniste r

i s assume d t o adsor

b al l vapor s passin g throug h th e adsorben t bed , u p t o th e poin t

o f breakthrough
. After

thi s point , an y additional vapor s fed t o th e caniste r ar e assume d t o b e entirel y vented
. More specifically , th e adsorptio n fron t for th e adsorben t

be di s assume d t o b e perfectl y sharp , wit h n o leadin g o r

trailin g tail
. Calculation s necessary t o simulate caniste r loading , therefore , are simpl y t o ad dan y portio n of

incomin g vapor s t o th e cunen t caniste r loa dup t o th e maximu mcaniste r

capacity , an d t o ven t

an y remainin g inle t

vapor s a s emissions
. Th e maximu mcaniste r

capacity i s determine d b y th e specifi c caniste r capacity obtaine d fromth e purg e curve , alon g wit h th e actual caniste r

volume
. N o parameter s o r dat aothe r than, th e canister

breakthroug h capacit

y ar e neede d t o perfor

mthes e calculations
. A mor e realisti c caniste r loadin g mode l i s als o availabl e whic h assume d that caniste r loadin g i s somewha

t les s efficien

t tha n wit h a n ideal caniste r

up t o th e breakthroug h point , an dtha t som e caniste r

capacit y i s stil l availabl e at caniste r loading s beyon d th e breakthroug h point
. Th e efficienc y o f caniste r loadin g i s determine d fromexperimenta l data , an di s afunctio n o f

caniste r capacit y expresse d a s percen t

of breakthroug h capacity
. Figur e 4 show s th e applicabl e experimental dat aan d th e correlatio n o f thes e dat ause d b y th e non-idea

l efficiency-base dcanister

loadin g model
.



### 1 9P.2 6



### Figure 4 Canister Loadin

g Efficienc y vs . Caniste r Loa d 12 0 

# 1 o 

## s U l 6 0

. 5

. a


### 0 10

0 200 30 0 Caniste r Load , % o f Breakthroug h Capacit y Th e caniste r efficienc y correlatio

n ha s th e followin g form : (e " - e' u 

### ) Efficienc y = k l - k 2 (e u 

### + e"U

) wher e u = k 3 * (Canisterjoa d - k_v ) Caniste r loading mode

l parameters tha

t have bee n determineda s o

f th e dat e o f thi s repor t ar e a s follows : k l

k 2 k 3 k 4 0.7 0

0.3 0 0.0 5 146.00 CAUTION : Althoug

h the for mo f th e caniste r loadin g mode l an dcorrelation appea

r to b e appropriate , ver

y limite d dat

aar e availabl e fro

mwhic h t o determin e th e fou

r model constant s tha

t ar e needed
. A s additiona

l databecom

e availabl e applicabl e t o differen t canister s an

d charcoals , the indicatedvalue s ma y change
. Th e above constant s ma y b e used , but wit h appropriat

e cautio n an dunderstanding
. Tw o calculation option s ar

e available fo

r carrying out

caniste r purg e calculations , bot

h o f whic h accoun t fo r th e non-linea r characteristic s o

f the purg e curve . Th

e first option tha t i s available , an

d the onl y one includedwit

h Releas e 1.

0 o f th e P T model , assume s tha

t al l purg e behavio

r ca n b e describedb

y asingle purg e curve . Fo

r thi s option , the purg e curve i s described b

y atable o f value s tha t relat e th e mas s o f hydrocarbon s purgedto th

e volum e o f purg e air
.

2 0P.2 7

A secon doption s i s als o availabl e whic h eliminate s th e assumptio n tha t asingl e purg e curv e i s sufficient

t o describ e caniste r

purg e behavior
. Experimental dat asho w tha t a t th e star t o f apurg e cycle , th e rat e a

t whic h hydrocarbon s are remove d fromcharcoa l i s quit e rapid , an dno t

astron g functio n o f

th e caniste r

load a t th e star t of purge . In contrast , th e firs t purg e calculatio n option s describe d abov e implicid y assume s that hydrocarbon s are removedmuch more slowly a t th e star t o f purg e when canister s ar

e lighdy loade d compare d t o th e start

o f purg e wit

h aheavil y loade d canister
. T o describ e thi s typ e o f purg e behavior , afamily o f

purg e curve s i s needed
. Eac h member o f thi s curv e famil y i s simila r t o th e singl e purg e curv e describe d above , an d i t relate s hydrocarbon s purge d to purg e volume
. Th e particula

r shap e o f agiven member

o f thi s family i s specifie d by th e caniste r load , a s percen t

o f saturatio n capacity , a

t th e star t o f purge . Fo r

thi s purg e calculatio n option , th e require dfamily o f purg e curve s are obtaine d froma n analytica l functio n rathe r tha n atabl e o f

values
. Althoug h th e tw o purg e calculatio n option s differ i n th e way tha t

apurg e curv e i s described , calculation s ar e similar for agive n purg e curve . Thes e calculation s ar e describe di n th e followin g paragraphs , followe d by adiscussio n o f th e algorith muse d t o implement

th e secon dcalculatio n option s incorporatin g purg e curv e families
. Th e caniste r

purg e calculatio n sequenc e i s bes t illustrate d b y example , wit h th e ai d o f Figur e 5
. Thi s exampl e demonstrate s determinatio n o f th e final caniste r

loadin g startin g fromaknow n initia l caniste r load an d aknow n purg e volume
. Th e value s show n belo w are assume dfor

thi s example
. The y ar e give n o n bot h aspecific , o r

pe r lite r o f caniste r volum e basis , an do n atota l basis
. Ouantit v Specifi c Basi s Canister siz e 1.0 1 Workin g Cap
. 32. 2 g/ 1 Initia l loa d12. 2 g/ 1 Purg e volum e 17. 8 ft3/l

35- 1 3 0 • 

### 25

- H C Purged 2 °

- (gms ) 15 . 

### 10 ' 5 •
n • 

### 0 Figur e 5 Tota l Basi s 2.0 1 64. 4 g/ 1 24. 4 g 35. 6 ft3 Sampl e Canister

Purg e Curv e

5 1 0 1 5 2

Purg e Vol t 0 2 5 3 0 im e (SCF ) 

### 3 5 4 0
Th e followin g step s are carrie d ou t t o determin e th e fina

l canister loading : 

### 2 1P.2 8

1 ) Determin e th e amoun t

of purg e requiredt o reac h th e initia l caniste r loa d from afully loade dcanister
. In thi s example , thi s i s th e purg e volum e require d t o reac h aloadin g o f 12. 2 g/ 1 (24. 4 g total ) fro ma n initia l loadin g o f

32. 2 g/ 1 (64. 4 g total)
. D o thi s b y enterin g th e purg e curv e o n th e y-axi s a

t apoin t correspondin g t o th e valu e (maximu m loadin g - curren t

loading ) an d rea d fromth e purg e curv e th e correspondin g purg e volume
. Th e entr

y valu e i s a

t 32. 2 - 12. 2 = 2 0 g/ 1 (64.4-24.4=40. 0 g total ) a s show n i n Figure 1
. Note that

al l entrie s int o th e purg e curv e are mad e o n aspecifi c o r per-liter basis , s o that

th e purg e curv e i s initiall y entere d a t avalu e o f

20. 0 g/l rathe r that 4 0 g total
. 2 ) Addth e availabl e purg e volume t o the purg e volume obtaine d i n 1 ) above
. Thi s valu e i s 2. 2 + 17. 8 = 2 0 ft3/l (4. 4 + 35. 6 = 40. 0 ft 3 total)
. 3 ) Ente r th e purg e curv e fromth e x-axi s a t th e valu e from2 ) above , an d rea d fromth e purg e curv e th e correspondin g quantit y o f hydrocarbon s purged
. In thi s case , th e valu e i s 30. 3 g/ 1 (60. 6 g total)
. 4 ) Calculat e th e final loadin g b y subtractin g th e valu e obtaine d i n 3 ) abov e fromth e tota l caniste r workin g capacity
. In thi s case , th e valu e i s 32. 2 - 30. 3 = 1. 9 g/ 1 (64. 4 - 60. 6 = 3. 8 g total)
. Thi s exampl e indicate s tha t th e final canister

loadin g i s 1.9 g/ 1 o r

atotal load of

3. 8 g . Th e abov e procedure doe s no t account fo r th e influenc e of

temperature o r

inle t hydrocarbo n vapo r compositio n o n carbo n capacit y o r performance , no r

doe s i t accoun t for non-idea l adsorptio n characteristic s of charcoal
.

22P.2 9

Figur e 6

H C P u r g e d > G r a m s / L 1 t e r 90.0 0 - r
80.0 0 - - 70.0 0 - - 60.0 0 - - 50.0 0 - -
40.0 0 - -
30.0 0 - -
20.0 0
10.0 0
0.0 0 - 0.0 0 20.0 0 40.0 0 60.0 0 80.0 0 100.0 0 120.0 0 140.0 0 160.0 0 180.0 0 200.0 0 Purg e Volume , cu . ft
. Caniste r purg e calculation s ar

e identical to thos e oudine d when analytical purg e curve s ar e use dinstea do f

apurg e curv e table , excep t for th e algorith muse d t o specif y th e initia l caniste r loada t th e star t of apurg e event

an d thu s aparticula

r load-dependen t

purg e curve . Fo r bot h driv e an dback-purg e events , apurg e curv e i s determine d base d o n th e caniste r loa da t th e star t o f th e drive
. Thi s purg e curv e i s use d for th e duratio n o f

agive n driv e event , eve n thoug h caniste r loadin g ma

y occu r durin g th e driv e whe n fue l tan k vapo r generatio n caniste r

purge . CAUTION : Th e algorith mdescribe d abov e base d on afamily o f analytical purg e curve s i s believe dt o b e areasonabl e representatio n o f real-world canister

behavior , an d i t

wil l remain apart o f th e P T model
. Th e implementatio n o f th e algorith mi n Releas e 2. 0 o f th e P T 2 3P.3 0

mode l i s preliminary , however
. At th e presen t

time, insufficient

experimenta l dat aexist s fro mwhic h areliabl e analytica l purg e curv e functio n ca n b e determined
. It i s recommendedtha

t user s of th e P T mode l mak

e us e o f th e analytica

l purg e curv e calculatio n optio n for evaluatio n purpose s onl y unti l suc h time a s additional experimental dat abecome availabl e an dappropriate mode l refinements ar e made
. Dat ao n whic h th e curren t purg e curv e functio n i s based , an d th e for mo f th e functio n selecte dt o generat e purg e curve s withi n th e P T model , ar e likel y t o b e change d i n th e future
. Detail s o f

experimental dat aand th e associate d correlatin g function , therefore , ar e no t include di n th e bod

y o f thi s report . Brief

comment s o n th e source s o f preliminar

y dat a upo n whic h th e curren t

analytical purg e curve s are base d i s include d in Appendi x E , whil e intereste dreader s ca

n examin e th e sourc e cod e of th e Dopurg e modul e for

detail s o f th e analytica l purg e curv e function
. i ) Ptbkp g Thi s modul e processe s back-purg e event s tha t occu r a s fuel tan k

temperature s fal l afte

r diurna l temperatur e rises, o r afte r drives
. Th e purg e volum e fo r thi s even t

i s calculate d fro mauser-specifie d back-purg e rate , in unit s o f ft3/gal/°F, th e user-supplie d tan k capacity , an dth e magnitud e o f th e tan k temperatur e decreas e specifie d a s a n even t parameter . Caniste r

purg e calculation s ar

e then carrie d ou t

usin g th e Dopurg e module , an d asummar y o f th e hydrocarbo n mas s purge d and the resulting caniste r state i s displayed
.

2 4P.3 1

II I User s Guid e Thi s sectio n provide s instruction s fo r preparatio n o f

th e inpu t dat aand table s neede d b y th e P T model , for

runnin g th e model , an d fo r interpretin g outpu t

generate d b y it
. I n addition , guideline s ar e provide dfor makin g certai n programmodification s tha t ma y b e neede d t o more realisticall y mode l performanc e of evaporativ e emission s contro l devices
. Sectio n A give s ageneral descriptio n o f th e step s necessar

y t o perfor masimulation , whil e Section s B an dC ar e concerne dwit h dat asource s an d preparatio n o f tabula r an d scalar

data , respectively
. Sectio n D describe s th e sequenc e o f step s necessar

y t o ru n th e mode l onc e dat afile s hav e been prepared
. Finally , Sectio n E oudine s ho w user-prepare d programcod e ma y b e incorporate dint o th e model
. A ) Overvie w Us e o f th e P T model i s atwo-ste p procedure , with th e first consistin g o f

dat afil e preparation , an dth e second , runnin g o f th e mode l itsel f

an d interpretatio n o f

results
. In almos t al l cases , dat apreparatio n i s th e mos t critical an d time consumin g o f th e tw o steps . Th e dat apreparatio n ste p ca n b e divide d int o thre e parts , correspondin g t o scala r o r inpu t data , tabula

r data , an deven t

data , a s describe d i n Sectio n II-B , "Inpu tData. " Generally , adifferent inpu t dat afile i s neede d fo

r eac h simulatio n run , althoug h files for aserie s o f run s are often simila

r in content . A smaller

number o f even t dat afiles are needed , a s th e same event s ar

e usuall y use dfo

r anumber o f mode l runs . Th e same i s tru e o f tabula r dat a files, especiall y th e caniste r purg e an d drivin g schedul e files. Additional vapo r generatio n file s ma y b e needed , dependin g o n characteristic s o f fuel s t o b e use d for

simulation
. Al l dat afiles consis t

of ordinary tex t

an d numbers , s o that

the y ca n b e prepare d an d modifie dwit

h th e ai do f

atex t edito r o r wor d processor . It

ma y b e convenien t

t o prepar e tabula r dat afiles, suc h a s vapo r

generatio n files, wit

h th e ai d o f

aspreadsheet
. If

aword processo r i s used , a

n appropriat e mod e shoul d b e selecte d t o avoi d includin g an y formattin g o r

othe r specia l character s int o dat afiles
. Generally , inpu t dat afile s ar e frequentl y modified , whil e tabula r an d even t

dat afiles are seldom , if

ever , change d onc e the y hav e been prepared
. Runnin g th e P T model , a s describe d in Sectio n III-D , "Progra m Use, " i s straightforwardonc e al l dat afiles ar e available
. Often , th e mode l i s use d a s adesig n too l t o findth e valu e of

som e inpu t variabl e suc h tha

t simulate d vehicl e performanc e meet s certai n criteria
. Thi s desig n proces s involve s selectin g a n initia l valu e o f

th e inpu t

variable , runnin g th e mode l usin g thi s value , examinatio n of output , followe d b y modificatio n o f th e initia l inpu t

value
. Th e mode l i s the n reru n in a n iterativ e fashio n unti l th e desire d mode l outpu t i s obtained
. A typica l applicatio n o f thi s procedur e i s findin g th e caniste r siz e neede dt o provid e agiven leve l o f emission s contro l under

aspecifie d set

o f conditions
. B ) Dat a Fil e Preparatio n Thi s sectio n outline s th e step s necessar y to prepare dat afile neede d b y th e P T model
. Th e structur e o f

thes e guideline s follow s tha t o f Sectio n II-B , "Inpu

tData. " I n Sectio n 1 below , "Inpu

tDat a Preparation, " eac h o f th e dat aitem s tha

t mus t b e include d i n th e scalar o r inpu t dat afile i s discussed
. Sectio n 2 below , "Tabula r Dat a Preparation, " describe s preparatio n o f th e thre e tabular

dat afile, whil e Sectio n 3 , "Even tDat a Preparation, " cover s preparatio n of even t dat afiles.


### 25P.3 2

1 ) Inpu tDat a Preparatio n Th e scala r o r inpu t dat afile consist s of

anumber o f entrie s correspondin g t o eac h o f th e dat aitem s describe di n Sectio n II-B-1 , "Inpu tData. " Th e prototyp e o f eac h entr y i s a s follows : <keyword > <data_count> <data_list> Th e <keyword > consist s o f th e nam e of a n inpu t dat akeyword t o whic h anumeri c valu e i s t o b e assigned , an d<data_count> i s th e number o f numeri c value s tha

t are to b e specified
. <data_list > i s the n th e set

o f on e o r more actua

l dat avalues
. Th e inpu t

dat akeyword s use d b y th e P T mode l ar

e summarize d i

n the followin g Table
. Keywor d

pcurgetyp e logfla g

drivefil e vaporfile l vaporfile 2 Typ e Coun tDescriptio n titl e tanksiz e maxpurge bprat e diuma l hotsoa k purgedela y cansiz e

canstart para m purgetyp e cantyp e Cha

r Rea l Rea l Rea l Rea l Rea l Intege r Rea l

Rea l Rea l Rea l intege r <8 0

1 1 1 1 1 1 1/2

1 4 1 1/ 5

intege r 1 Logica l 2

Cha r Cha r <8 0 <8 0 A descriptiv e titl e tha twil l b e displaye d a

tth e star to f eac h simulation . Fue l tan k liqui d capacity , gallons . Maximu m caniste r purg

e rate , SCFM . Se e Sectio n H-B-l-d . Back-purge flo w rate . ft3/gal./°F . Se e Sectio n H-B-l-q . Bas e cas e diurna

l caniste r loading . Se e Sectio n II-B-l-e . Bas e cas e hotsoak caniste r loading . Se e Sectio n H-B-l-f . Numbe r o f time step s by whic

h the star to f purg e i s delaye d afte r th e star to f a drive . Se e Sectio n II-B-l-g . Caniste r size , liters . Als o specifie s caniste r breakthroug h i f cantyp e i s se tt o 1 an d pcurvetyp e i s se tt

o 0 (non-ideal caniste r loadin g an d a curve specifie d by a

n experimenta

l purg e curv e table) . Initia l caniste r loadin g a

s percento f

tota l capacity . Horsepowe r correlatio n parameters . Se e Sectio n II-B-l-h . Purg e strateg y model index . Normall y 3 . Se e Sectio n HI-E . Th e firs tdat a item specifie s i f

the idea l caniste r loadin g mode l i s t o b e use d (cantype=0 ) o r i f the non-ideal caniste r efficienc y loadin g mode

l i s t o b e use d (cantype=l) . I f the firstvalu e specifie s ideal caniste r loading , n o additiona l value s mus tb e specified . Fo r non-idea l loading , however , fou

r loadin g model paramete r mus t b e specified . Se e Sectio n II-C-3-h . Specifie s if

th e caniste r purg

e curve i s t

o b e specifie d b y a tabl e o f experimenta

l dat a (pcurvetype=0 ) or b

y a n analytica

l functio n (pcurvetype=l) . Lo g fil e an d plo tfile outpu

tcontrol flags . Th e firstvalu e determines if

a norma l o r condense d lo g outpu

tfile shoul d b e generate d (value s .true , an

d .false. , respectively) . Th e secon d valu e applie s t o th e plo toutpu

tfile. Se e Sectio n HI-D-2 . Pathnam e fo r drive schedul e tabula

r dat a file. Se e Sectio n QT-B-2-a . Pathnam e for vapo r generation tabula r dat a files. A tleas ton e o f thes e keyword s musthav e a pathnam e assigne d t

o it, a s wel l a s 

### 2 6canfil e logfil e plotfil e eventfil e Cha

r Cha r Cha r Cha r <8 0 <8 0 <8 0 <8 0 vaporfile 3 keyword s corresponding t o all drive even tkeyword s occurring i n the even tdat

a file. Se e Sectio n HI-B-2-c . Pathnam e for caniste r load/purge tabula r dat a file. Se e Sectio n DI-B-2-b . Pathnam e fo r lo g outpu

tfile. Se e Sectio n HI-D-2 . Pathnam e for plo toutpu

tfile. Se e Sectio n HI-D-2 . Pathnam e fo r even tdat

a inpu tfile. Se e Sectio n HI-B-3 . In preparin g th e inpu t

dat afile , keyword s mus t

appea r exactl y a s i n th e tabl e above , wit h lowe r cas e letter s use dwhere indicated
. Upper an d lowe r

cas e letter s ar e no t

treate d a s bein g equivalent
. Th e meanin g o f th e forma t type s appearin g i n th e secon d colum n o f th e tabl e ar e a s follows : Rea l value s ar e number s appearin g i n eithe r floatin g poin t

o r exponentia l notation ; Intege r value s are number s that

d o no t contai n adecimal poin t

o r fractional point ; Char(acter ) value s are alphanumeri c text , al l o f whic h mus t

appea r o n a singl e dat afile line
. Characte r string s shoul d b e terminate d b y adoubl e backslas h ("\\") ; Logica l value s ar e eithe r tru e o r false , a s indicate d b y th e tex t ".true. " o r

".false. " respectively
. Fo r

real, integer

and logica

l dat aitems , th e dat acoun t appearin g wit

h th e dat a keywor d indicate s th e number o f individual dat aitem s t o b e specified
. Fo r characte r dat a items , th e dat acoun t

refer s t o th e maximu mnumbe r o f character s that

ma y appea r i n th e followin g tex t

string
. Comment s ma

y b e include d a

t any poin t

i n th e fil e b y placin g a semicolo n (";" ) in th e firs t

colum n of th e lin e to b e mad e acomment . 2 ) Tabula r

Dat aPreparatio n Thi s sectio n describe s source s o f dat afo r eac h of th e thre e tabula

r inpu t dat afile s describe d i n Sectio n II-B-2 , "Tabula r Data, " an d th e forma

t o f eac h dat afile
. Sectio n 1 cover s th e driv e schedul e table , whil e Section s 2 an d 3 discus s th e caniste r purg e tabl e an d th e vapo r generatio n table , respectively
. a ) Driv e Schedul e Tabl e Thi s tabl e consist s o f

vehicl e spee d an d acceleratio n value s at equall y space d intervals , usuall y on e secon di n width , tha t describ e aparticula

r driv e schedule
. I n th e cas e o f light

dut y vehicl e an dlight-duty truc k urba n dynamomete r

(LA-4 ) an d heavy-duty truc k urba n dynamomete r

schedules , th e necessary dat aar e availabl e in 4 0 CFR86 , Appendi x I , section s a) an dd) , respectively
. Th e forma t o f thi s fil e i s a s follows : Lin e 1 : Tide Lin e 2 : Velocit

y (mph ) Acceleratio n (mph/sec. ) Lin e n : Velocit

y (mph) Acceleratio n (mph/sec. ) b ) Caniste r

Purg e Tabl e Thi s tabl e consist s o f

value s describin g caniste r purg e characteristic s an d whic h relat e th e volum e o f

purg e ai r

necessary t o purg e agive n quantity o f hydrocarbon s fro mafully loade dcanister
. Two method s ar e availabl e i n th e P T mode l t o specif y th e caniste r

purg e curve , correspondin g t o whethe r th e caniste r

purg e i s assume d t o b e describe d b y asingl e purg e curv e independentl y o f caniste r load , o r whethe r suc h adescriptio n i s give n b y a 2 7P.3 4

famil y o f purg e curve s parameterize d b y caniste r loa d a t th e star t o f purge . I n th e former case , th e purg e curv e i s specifie d b y atabl e o f

values , whil e i n th e latte r case , th e purg e curv e i s specifie db y aset

o f parameter s tha

t ente r int o a n analytical functio n tha

t describe s th e desire dfamil y o f

purg e curves . Whic h optio n i s use d b y th e P T mode l i s specifie d b y th e pcurvetyp e scala

r inpu t dat aitem , a s describe d in th e keyword tabl e above
. Fo r purg e curve s describe db y atabl e o f purg e curv e data , th e dat aar e normall y obtaine d experimentally , usin g th e followin g procedure : 1 ) Loadcanister

t o breakthrough
. 2 ) Begi n caniste r

purgin g a t apurg e flow rat e consisten t wit h th e expecte d in-us e rate . Simultaneously , record total purg e volume and canister weight
. 3 ) Continu e purg e an ddat arecordin g unti l th e caniste r i s fully purge d an d astabl e weigh t i s observed
. At leas t 4 0 t o 5 0 dat apoint s shoul d b e use d t o giv e agoo d representatio n o f th e entir e purg e curve . Th e forma

t o f thi s dat afile i s a s follows : Lin e 1 : Tide Lin e 2 : Total purg e vol
. (SCF ) Tota l mas s purge d (gms ) Lin e n : Total purg e vol
. (SCF ) Total mas s purge d (gms ) Bo mpurg e volum e an dhydrocarbo n purge d mas s value s shoul d b e i n ascendin g order , an dth e final file lin e shoul dgiv e th e caniste r workin g capacity o n aper-lite r basis , alon g wit h th e tota l purg e volum e requiredt o full y purg e aloade d 1.0 lite r

canister
. Th e tide lin e consist s o f

u p t o 8 0 alphanumeri c character s tha t ma y b e use d t o describ e content s o f th e file. Al l remainin g dat avalue s are al l numeric , format-free , an d shoul d b e separate d b y blank s o r commas . Eac h pai r

o f speed/acceleratio n dat ashoul d occup y asingl e lin e i n th e file. Fo r purg e curve s describe db y a n analytica l function , parameter s o f th e functio n ar e normall y obtaine db y acurv e fit t o analytica l data
. A s o f th e dat e o f

thi s document , insufficien t

experimenta l dat awer e availabl e t o hav e fully refine d th e functio n use d t o generat e purg e curv e families , s o that afull descriptio n o f

th e functio n selecte d an d th e curv e fittin g proces s use dt o generat e th e neede d parameter s i s no t included
. Whe n thi s optio n i s used , th e paramete r dat afile name d fordeq.ca n shoul d b e used , a s describe d i n Appendi x A
. c ) Vapo r Generatio n Tabl e Thi s tabl e consist s o f

values describin g fuel tank vapo r generatio n characteristic s o f a vehicl e durin g operation
. Thes e dat aincorporate the influenc e of several factor s includin g th e fue l tan k temperature profil e durin g vehicl e operation , fue l volatility , fue

l tan k pressure , an dth e rat e a

t whic h tan k vapor s ar e generate d i n respons e to change s in temperature . Dat a item s i n thi s file includ e tim e sinc e th e start o f adrive , tota l hydrocarbo n vapo r mas s generate ddurin g th e drive , and th e instantaneou s vapo r generatio n flow rat e a

t eac h time. Th e file forma

t i s a s follows :



### 2 8P.3 5

Lin e 1 : Tide Lin e 2 : Time(min. ) Total H C Mas s (g ) Vapo r Flo w Rate (SCFM ) Linen : Time(min. ) Tota l H C Mas s (g ) Vapo r

Flo w Rate (SCFM ) Th e title lin e consist s o f

up t o 8 0 alphanumeri c character s tha t ma y b e use d t o describ e content s o f

th e file. Al l remaining dat avalue s ar e al l numeric , format-free , an d shoul d b e separate db y blank s o r

commas . Eac h set

o f time/mass/flow rat e dat ashoul d occup y a singl e lin e in th e file
. Dat apoint s i n thi s fil e nee d no t b e equall y space d i n time
. Th e tota l length o f tim e represente db y th e file shoul db e a t leas t a s lon g a s th e longes t

driv e ma t i s t o b e simulated , takin g int o accoun t

sequential drive s tha

t hav e initia l driv e times startin g othe r tha n a t th e beginnin g o f

avapo r generatio n table
. If available , experimenta l dat ama y b e use d directl y i n vapo r generatio n tables
. I n mos t cases , however , i t

ma y b e necessar

y t o us e simulation s t o obtai n th e neede d data
. A multi

ste p procedur e wa s use ddurin g developmen t o f th e P T mode l t o obtai n vapo r generatio n dat afiles, a s outline dbelow
. 1 ) Generate atabl e that

describe s fuel tan k

vapo r generatio n a s afunctio n o f fue l temperature . Thi s tabl e shoul d hav e entrie s for temperature , mas s o f

hydrocarbo n vapo r generated , an dtank

vapo r flow rate . Th e rang e o f

temperature s shoul d b e representativ e o f

th e rang e expecte d fo r

th e vehicl e t o b e simulated
. Typically , a rang e o f 25-3 0 ° F i s appropriate
. Hydrocarbo n mas s values shoul d b e i n gram s an dindicat e th e cumulativ e vapo r generatio n startin g fro mth e initia l tan k temperature . Vapo r

flow rate s shoul d b e i n SCF/minute , an d indicat e instantaneou s flow rate s a

t eac h temperature . Bot

h hydrocarbo n mas s an d flow rat e value s shoul d b e normalize dt o a1.

0 gallo n tan

k size
. 2 ) Generat e atabl e o r

functio n tha

t relate s tim e an dfuel tan k temperatur e durin g vehicl e operation
. Thi s tabl e wil l mos t likel y b e base d o n experimental data , sinc e a realisti c theoretica l mode l o f fuel tan k temperature s i s difficul t

t o develo p i n th e absenc e o f

experimenta l data
. Dat ause d t o develo p th e P T mode l i s describe di n Appendi x D , "Vapo r Generatio n an d Temperatur e Profil e Data. " 3 ) Combin e table s fromstep s 1 ) an d 2 ) abov e a s follows
. Selec t th e temperature valu e fro ma n entr y i n th e tabl e for

m1) , an d ente r

th e tabl e from2 ) a t

th e sam e temperatur e value
. Obtai n th e time , o r length o f

driv e neede d t o reac h tha t temperature , interpolatin g a s necessary . Generate asingl e entr y i n th e final vapo r generatio n tabl e usin g th e tim e valu e obtaine d fro mth e ste p 2 ) table , an d th e hydrocarbo n mas s an d vapo r flo w rat e value s fromth e step 1 ) table
. 4 ) Repea t step 3 ) fo r al l entrie s i n th e ste

p 1 ) table
. Abbreviate dexample s o f

table s correspondin g t o thos e describe d i n th e step s 1 ) an d 2 ) above , an dth e resulting vapo r generatio n tabl e are show n below
.



### 29Vapo r Generatio n Tabl e (Ste

p 1 ) Temperatur

e H

C Mas s Vapo

r Volum e (g
. Fahrenheit) (grams ) (SCF/g-1 ) 84. 0 0. 0 l-77e- 3 85. 0 0.2 0 2.05e- 3 8 5 5 0.3 0 2.l0e- 3 86. 0 0.4 1 2.15e- 3 8 7 o 0.6 4 2.24e- 3 8 7 5 0.7 6 2.30e- 3 88. 0 0.8 9 2.35e- 3 88. 5 1.0 1 2.40e- 3 89. 0 11 5 2.46e- 3 8 9 5 1.2 9 2.52e- 3 90. 0 1.4 3 2.58e- 3 9 0 5 1.5 8 2.65e- 3 9 1 0 1.7 4 2.72e- 3 9 1 5 1.9 0 2.78e- 3 9 2 0 2.0 7 2.86e- 3 9 2 5 2.2 5 2.93e- 3 9 3 5 2.6 2 3.10e- 3 94. 0 2.8 3 3.20e- 3

3 0P.3 7

Time/Temperatur

e Tabl e (Ste

p 2 ) Temperatur

e (° - Fahrenheit ! 84. 0 84. 5 85. 0 85. 5 86. 0 86. 5 87. 0 87. 5 88. 0 88. 5 89. 0 89. 5 90. 0 90. 5 91. 0 91. 5 92. 0 92. 5 93. 0 93. 5 94. 0 Time (Min. } 0. 0 0.5 4 1.1 9 1.8 5 2.5 2 3.2 0 3.8 8 4.5 7 5.2 7 5.9 8 6.7 0 7.4 2 8.1 5 8.9 0 9.6 5 10.4 1 11.8 4 11.9 7 12.7 6 13.5 7 14.3 9 Vapo r Generatio n Tabl e (Step s 3 an d 4 ) Tim e (Min. ) 0. 0 0.5 4 1.1 9 1.8 5 2.5 2 3.2 0 3.8 8 4.5 7 5.2 7 5.9 8 6.6 9 7.4 2 8.1 5 8.9 0 9.6 5 10.4 1 11.1 8 11.9 7 12.7 6 13.5 7 14.3 9 HCMas s

fgrams/eal. 1 0. 0 0.1 0 0.2 0 0.3 0 0.4 1 0.5 2 0.6 4 0.7 6 0.8 9 1.0 1 1.1 5 1.2 9 1.4 3 1.5 8 1.7 4 1.9 0 2.0 7 2.2 5 2.4 3 2.6 2 2.8 3 Vapor Flo w Rat e (SCFM/eal ) 1.77e- 3 1.91e- 3 2.05e- 3 2.10e- 3 2.15e- 3 2.19e- 3 2.24e- 3 2.30e- 3 2.35e- 3 2.40e- 3 2.46e- 3 2.52e- 3 2.58e- 3 2.65e- 3 2.72e- 3 2.78e- 3 2.86e- 3 2.93e- 3 3.02e- 3 3.10e- 3 3.20e- 3 3 ) Even t

Dat aPreparatio n Th e even t dat afile consist s o f

asequenc e o f

even t entries , on e pe r

file line , eac h o f

whic h consist s o f

akeywor dan don e o r

mor e parameters . Vali d keyword s an d associate d number of parameter s ar

e a s follows : 

### 3 1P.3 8

! .

Kevwor d drive l drive 2 drive 3 diumal hotsoa k backp g Paramete r Count 

### 1- 2 1- 2 1- 2 1 1 1 Lowe r cas e tex t mus t b e use dfor

keywords ; upper

an d lower

cas e letter s are no t

treate d a s bein g equivalent
. Th e definitio n o f even t keywor d parameter s ca n b e foun d i n Sectio n H-B-3 , "Even

tData. " C ) Progra m Us e Thi s sectio n describe s us e o f th e P T mode l t o carr

y ou t simulation s onc e al l dat afiles hav e bee n prepared , a s covere di n Sectio n II- B an d II-C
. Basi c command s an d procedure s fo r runnin g th e mode l o n IBM-P C an d compatibl e machine s are foun d i n sectio n 1 , "Running th e Model, " whil e asummar y o f mode l outpu t

i s foun d i n sectio n 2 below , "Outpu t Description. " 1 ) Runnin g th e Mode l Th e P T model , a s distributed , wil l ru n under MS/PC-DO S Versio n 3. 0 o r late r o n IB M A T computers , o r

o n compatibl e machine s that us e a n 8028 6 processor 1

. Th e minimu m hardwar e require dt o ru n th e mode l include s afloppy dis k drive , adisplay , an d a

t leas t 256 k of memory . Becaus e of

the data-intensiv e nature of th e mode l an d th e amount o f dat a tha t mus t b e rea dfromdis k

files durin g eac h run , i t

i s highl y recommende d tha t th e mode l b e ru n o n amachin e wit

h ahard disk
. Releas e 2. 0 o f th e P T mode l make s us e o f anumeri c coprocesso r

(8087/80287/80387 ) i

f present , but

doe s no t require. Before th e mode l i s run , i t shoul d b e transferre d fromth e distributio n dis k t o aworkin g flopp y disk , o r

installe do n ahard disk , a s describe d in Appendi x A
. Th e example s tha t follo w assum e tha

t th e director

y structure o f

th e distributio n dis k

i s preserved , o r

that th e mode l i s installe do n ahar ddis k i n adirectory calle d PT
. Th e director y setu p shoul d therefore appea

r a s show n belo w in Figure 7
.

lT Jser s wh o requir e mode l version s fo r othe r machin e configuration

s ca n recompil e th e P T mode l usin g th e distribute dsourc e cod e an d thei r ow n FORTRA N compiler
. I f user s canno t compil e th e mode l themselves , th e autho r shoul d b e contacte d t o determin e i f a n appropriat

e mode l versio n ca n b e generate d an d distributed
. Se e Sectio n D) , "Progra

mGeneratio

n an d Modification, " belo

w fo r furthe r details
. 3 2P.3 9



### P T pt.key pLba t rpt.exe runpLda t install.ba t Figur e 7

DAT A SOURC E ptfo r ptdihs.for
VP R EVT CA N 

### IN P 7297.vp r 84109.vp r ftp90.evt

ftplll5.ev t ford.ca n nissan.can sample.da t testl.da t test2.da t 

## w s 7191a.vp r 84104a . vp r 96116a.vp r
OU T DR V test l .ou t test2.out la4.dr

v nyc.dr v hwfe.dr v Dat afiles containe di n th e directorie s VPR , EVT , etc. , ar e liste d i n Appendi x A , "Distributio n Dis k Content s an d Mode l Installation. " Runnin g o f

th e P T mode l i s normall y accomplishe d throug h us e o f m e p t batc h file. Thi s techniqu e simplifie s operatio n of th e mode l b y automaticall y locatin g an d executin g th e mode l itself

, an db y appendin g th e prope r pat h name t o th e scala

r inpu t dat afile, th e nam e o f whic h mus t

b e specifie d when th e mode l i s executed
. Inpu t dat afile name s ar e assume d to hav e th e forma

t <input_data_file_name>.da t where th e brackete dtex t

represent s auser-specifie d name . Eac h o f thes e file i s expecte d to reside in th e director

y ptNdataSinp
. T o run th e model , th e workin g director y shoul d b e set

t o tha t containin g th e pt.ba

t file, in thi s cas e c:\pt , an d th e comman d prototyp e show n belo w used
. pt <input_data_file_name > 

### 3 3P.4 0

Note tha t th e extensio n ".dat " nee d no t appear , althoug h i t

ca n appea r i f desired
. A t thi s point , th e p t

mode l wil l begi n execution , an d th e inpu t dat afil e wil l b e read. A brie f summar y o f ke y inpu t dat aitem s wil l the n b e displayed , and eac h o f th e tabula

r inpu t dat a files wil l b e opened
. Th e name o f eac h file i s displaye d a s i t i s opened
. A s thes e files are the n read, th e number

o f dat aline s i n eac h file i s displayed , alon g wit h th e correspondin g titl e line
. Thi s informatio n i s usefu l to verif y tha t th e desire d dat afiles hav e been correcd y specifie dfor

eac h simulation
. Afte

r thes e tabula

r dat afiles hav e been read , th e first entr y in th e event dat afile i s read , andsimulatio n calculation s begin
. Normally , outpu t

fromth e mode l appear s o n th e display screen . Outpu t ca n b e redirecte d t o afile o r device , if desired , by usin g th e followin g comman d prototyp e t o begi n executio n of th e p t model : p t <input_data_file_name > <output_fd> wher e <output_fd > i s adevic e name (e.g. , lptl:) , o r th e full pat

h nam e o f

th e desire d outpu t file. Th e redirectio n symbo l "> " i s adde d automatically , s o tha t i t shoul d no t

b e include di n th e <output_fd> specification
. 2 ) Outpu tDescriptio n Th e P T mode l generate s thre e type s of simulatio n output , referred t o a s terminal output , lo g file output , an dplo t

file output . Terminal output , whic h normall y appear s o n th e compute r screen , i s th e primary outpu t stream . Thi s streamcontain s summarie s o f bot h inpu t dat a an dsimulatio n results
. Lo g fil e outpu t contain s detaile d second-by-secon d outpu t generate ddurin g driv e events . Becaus e thi s informatio n i s bot h voluminou s an d usuall y o f lesse r interes t tha n tha t displaye d a s part

o f termina l output , i t

doe s no t appear o n th e compute r screen . Plo t

file outpu t

contain s detaile d second-by-secon d value s for caniste r loadin g an dpercen t

o f engin e fue

l provide d by caniste r

purg e durin g driv e events . A s wit h lo g file output , thi s streami s directe d t o adis k file rathe r

tha n displaye d o n th e compute r screen . Th e followin g thre e section s describ e eac h o f thes e outpu t

stream s i n detail , an d provid e th e file forma

t use dfo r recordin g lo g an d plo t

outpu t data
. a ) Termina l Outpu t Termina l outpu t

i s th e primary outpu t

streamfromth e P T model , containin g inpu t dat a summaries , summarie s o f simulatio n results , an d message s describin g an y error s o r warning s that

ar e encountere d durin g mode l operation
. Thi s outpu t streami s normall y displaye do n th e compute r screen , althoug h i t

ma y b e redirecte d t o a

n alternat e file o r device , a s describe di n Sectio n III-C-1 , "Runnin g th e Model. " Fo r eac h even t simulate dby th e P T model , severa l value s ar e displaye d that identif y th e even t

bein g simulated , even t

characteristic s o r

parameters , an d result s fromsimulatio n o f th e event . Thi s sectio n describe s thi s output , and ho w eac h dat aite mi s to b e interpreted
. At th e star t o f calculation s fo

r eac h simulatio n event , th e mode l display s count s o f th e total numbe r o f event s processe dand th e total number o f event s processe d o f

th e same typ e a s th e curren t

event . Thi s informatio n i s usefu l t o determin e ho w fa r simulatio n ha s progresse dthroug h th e sequenc e of event s i n a

n even t dat afile. Followin g this , outpu t specifi c t o eac h even t

i s generated
. Sample s o f eac h ar e show n below , alon g wit h a descriptio n o f

eac h outpu t

item
.

3

4P.4 1

Hotsoa k an d Diurna l Events : Linel : Hotsoa

k event #2 Cumulativ e event

#5 Lin e 2 : Event

type : hotsoa

k Lin e 3 : H C to caniste r

(gms) : 7.4 0 Lin e 4 : H C vente d(gms) : .0 0 Lin e 5 : Fina

l canister load (%) : 45.7 0 Lin e 6 : Fina

l canister ca p (gms) : 20.9 9 Lin e 1 : "Hotsoa

k even t #2 Cumulativ e even t

#5 " Indicate s tha

t th e fifth even t

in th e even t dat afile i s bein g processed , an d tha t i t i s th e secon d hotsoak

even t o f di e simulatio n t o b e processed
. Lin e 2 : "Even

t type : hotsoak " Indicate s th e even t type . Lin e 3 : "H C t o caniste r

(gms)... " Indicate s th e tota l hydrocarbo n vapo r loa d flowin g int o th e canister

durin g thi s even t Lin e 4 : "H C vente d(gms)... " Indicate s th e mas s o f hydrocarbo n vapor s vente d int o th e atmosphere b y th e caniste r du e t o insufficient

capacit y t o adsor b some o r al l o f th e vapo r loadindicate db

y the valu e i n Lin e 4
. Lin e 5 : "Final can . load(%)..." Indicate s th e exten t

of caniste r loadin g at

di e en d o f

th e even t o n apercentag e basis
. A valu e o f 100.0 0 correspond s t o afull y loade d canister
. Lin e 6 : "Final can . cap . (gms)... " Indicate s th e availabl e caniste r capacity at

th e en d o f th e even t o n a n absolute mas s basis
. A valu e o f 0.0 0 correspond s t o afull y loade d canister wit h n o availabl e capacity
. Driv e Events : Linel : Driv e event * 2 Cumulativ e event #4 Lin e 2 : Processin g typ e 2 driv e even t Lin e 3 : Lin e 4 : Lin e 5 : Lin e 6 : Lin e 7 : Lin e 8 : Lin e 9 : Lin e 1 0 Lin e 1 1 Lin e 1 2 Lin e 13 Lin e 14 Star

ttime Driv e lengt h Endin g tim e Tota l fue l use d Obs ) Tota l mile s travele d Overal l miles/gallo n Tota l prg . rat e (ft3 ) Total H C purged (gms ) Total HC vente d (gms ) H C pg' dfro

mca n (g ) Final can . loa

d (% ) Final can . cap . (gms ) = = =

_ _ = = = = = = = = 0 106 1 106 1 1.4 9 5.5 5 23.1 4 19.9 5 42.1 5 0.0 0 25.7 9 26.5 4 28.3 9 Lin e 1 : "Driv e even t

#2 Cumulativ e even t

#4 " Indicate s tha

t th e fourt h even t i n th e even t dat afile i s bein g processed , an d tha t i t i s th e secon d driv e even t o f th e simulatio n to b e processed
. 

### 3 5P.4 2

Lin e 2 : "Processin g typ e 2 driv e event. " Indicate s adriv e event , an d tha t th e vapo r generatio n dat afile specifie d b y th e vaporfile 2 keyword in th e inpu t dat afile wil l b e used
. Lin e 3 : "Star

t time... " Indicate s th e startin g tim e of th e drive , a s specifie d b y th e secon dparameter

o f the drive x keywor

d in the even

t dat afile. Lin e 4 : "Driv e length... " Indicate s th e lengt h o f th e drive , a s specifie d b y th e first parameter o f the drive x keywor

d i n di e event

dat afile. Lin e 5 : "Endin g time..." Indicate s th e th e endin g tim e o f th e drive , a s compute d from th e value s displaye din line s 3 and 4 above
. Lin e 6 : "Amoun t

o f fue l used... " Indicate s th e calculate d quantity o f fue l use d durin g th e specifie ddrive
. Lin e 7 : "Total mile s traveled... " Indicate s th e calculate d distanc e travele d durin g th e specifie ddrive
. Lin e 8 : "Overal l miles/gallon... " Indicate d th e calculate d fue l econom y ove r th e specifie ddrive
. Lin e 9 : "Total prg . rat e (ft3)... " Indicate s th e tota l volum e o f purg e vapo r

enterin g th e engin e ove r

th e specifie d drive
. Thi s quantit y reflects th e volum e o f

vapor s purge d throug h th e caniste r

a s wel l a s fue

l tan k vapor s tha

t are route d direcd y t o th e engine
. Lin e 10 : "Total H C purge d (gms)... " Indicate s th e tota l mas s o f purg e hydrocarbon s enterin g th e engin e ove r

th e specifie d drive
. Thi s quantity reflect s hydrocarbon s purge dfromth e caniste r

a s wel l a s fue

l tank vapor s tha

t ar e route d direcd y t o th e engine
. Lin e 11 : "Total H C vente d (gms)... " Indicate s th e mas s o f hydrocarbo n vapor s vente d int o th e atmosphere b

y th e canister

du e t o insufficien

t capacit y t o adsor b some o r al l o f th e fue l tan k vapor s generate d durin g th e specifie d drive
. Lin e 12 : "H C pg' dfromca n (g)... " Indicate s th e mas s o f hydrocarbon s purge d from th e caniste r

durin g th e specifie d drive
. Lin e 13 : "Final can . loa d(%)... " Indicate s th e exten t o f caniste r loadin g at

th e en d o f th e even t o n apercentag e basis
. A valu e o f 100.0 0 correspond s t o afully loade d canister
. Lin e 14 : "Fina

l can . cap . (gms)... " Indicate s th e availabl e caniste r capacit y a t th e en d o f th e even t o n a n absolute mas s basis
. A valu e o f 0.0 0 conespond s t o afull y loade d canister
.



### 3 6P.4 3

Back-purg e Events : Lin e 1 : Backpurg e event #2 Cumulativ e event

#4 Lin e 2 : Processin g bac k purg e event . Delta

t = 15.0 0 Lin e 3 : Purg e vol
. (ft3 ) = .1 6 Lin e 4 : H C purge d(gms ) = 3.4 3 Lin e 5 : Final can . load (% ) = 76.3 0 Lin e 6 : Final can . cap . (gms ) = 10.7 4 b ) Lo g Fil e Outpu t Lo g file outpu t

contain s second-by-secon d outpu t generate d durin g simulation s o f driv e events . Thes e outpu t

value s provid e mor e detaile d informatio n abou t driv e simulation s than appear s i n termina l output . Thes e dat aare writte n t o a n outpu t file specifie d b y th e logfil e keywor di n th e scala r o r inpu t dat afile describe d in Sectio n II-B-1-1 , "Lo g outpu t fil e name, " an da s modifie d b y th e lo g fil e outpu t fla g describe d i n Sectio n III-B-1 , "Inpu tDat a Preparation. " Sampl e outpu t fromthi s file an d adescriptio n o f eac h outpu t ite mfollows
. Time : 10. 0 Speed : .0 0 Accel : .00 0 Fue l rate : 2.3030E-0 4 E P rate : .00 0 Ca

n prg vol : -1.0197E-0 2 FTHC(g/sec) : .0237 9 FT vp r (SCFM) : 4.923e-0 3 Total f t he (gl) : .2 6 Total f

t vp r (SCF) : 4.512e-0 4 %fue l a s vapor : .000 0 %fue

l fro mcan. : .00 0 Can
. loa d (%) : 99.02 7 Can
. ca p (gms.) : .375 9 Time : Time of

driv e simulation , i

n time unit s use d in th e driv e schedul e table
. Speed : Vehicl e speed , i n mph
. Accel : Vehicl e acceleration , in mph/sec
. Fue l rate : Liqui dfue l rat e int o th e engine , i n lbs/sec
. E P rate : Volumetri c flow rat e o f purg e vapor s int o th e engine , i n SCF/min
. Ca n prg . vol : Volumetri c flow rat e of purg e vapor s out

o f th e canister , in SCF/min
. FT HC : Mas s of

fue l tan k hydrocarbo n vapor s generate d durin g th e curren t driv e schedul e time interva l (grams)
. F T vpr : Volumetri c flow rat e of fue l tan k vapor s (air

+ hydrocarbons ) durin g th e curren t

driv e schedul e time interval (SCFM)
. Tota l f t he : Tota

l mas s o f fue l tan k hydrocarbon s generate d sinc e th e star t o f th e current driv e simulatio n (grams)
. Tota l f t vp n Total volum e of

fue l tan k vapor s (air

+ hydrocarbons ) generate d sinc e th e star t o f th e current

driv e simulatio n (grams)
. %fue l a s vapor : Percent

o f tota l fue l require d b

y th e engin e availabl e fromth e combine dcanister

purg e strea

man d fue l tan k vapo r stream . Thi s valu e ma y b e greater

tha n 100.0%
. %fue l fromcan : Percen

t of tota l fue l require d b

y th e engin e availabl e fromth e combine dcanister

purg e stream . Thi s valu e ma y b e greater

tha n 100.0%
. Can
. load(%) : Current

canister load , a s percent

o f tota l capacity
. Can
. ca p (gms) : Current

availabl e canister

capacity , in grams .

3 7P.4 4

c ) Plo tFil e Outpu t Plo t fil e outpu t

contain s second-by-secon d outpu t generate d durin g simulation s o f driv e events . Thes e outpu t

values provid e detaile d informatio n abou t caniste r loadin g an d percen t o f engin e fuel requirements provide d b y th e caniste r

purg e stream , an d ca

n b e use d t o prepar e plot s o f

thes e quantitie s versu s time. Thes e dat aar e writte n t o a n outpu t file specifie db y th e plotfil e keywor d i n th e scala r o r inpu t dat afil e describe d i n Sectio n II-B-l-m , "Plotoutpu tfile name, " an d a s modifie d b y th e plo t fil e outpu t

flag describe di n Sectio n III-B-1 , "Inpu tData Preparation. " Sampl e outpu t fromthi s file andadescriptio n of

eac h outpu t

ite mfollows
. Colum n 1 Colum

n 2 Colum

n 3 Lin e 1 : Simulatio n time Canister load (% ) %Eng
. fue

l fromcanister Lin e 2 : Lin e 3 : D ) Progra m Generatio n an d Modificatio n Thi s sectio n contain s abrie f guid e t o recompilatio n o f th e P T model , an d t o addin g additional , user-define dpurg e contro l strateg y models
. Althoug h neithe r o f thes e step s ar e necessary for

us e o f th e model , th e necessary instruction s ar e include d her e fo r thos e wishin g t o modif

y th e model
. Instruction s ar e brief , an d knowledg e o f

FORTRA N i s assumed ; person s wit

h question s no t

answere d i n thi s sectio n shoul d contac t di e author
. Th e P T mode l i s writte n i n FORTRAN-77 , an d ha s bee n compile d usin g Microsof t FORTRAN , versio n 4.01
. Any use r modification s t o th e mode l wil l require tha t thi s o r a compatibl e compile r

b e available , alon g wit

h asuitabl e tex t

edito r t o mak e an y neede d sourc e cod e modifications
. 1 ) Progra m Generatio n Compilatio n o f

th e P T mode l i s normall y carrie d ou t throug h us e o f

amake utility , suc h a s that include dwit

h th e Microsof

t Versio n 4.0 1 FORTRAN-7 7 compiler
. Al l sourc e cod e for th e model , alon g wit

h th e dat afiles require d b y make , ar e include d in th e sourc e subdirector y o f

th e mode l distributio n disk
. Tw o dat afiles ar e use d durin g mode l compilatio n an d linking
. Th e first o f thes e i s th e sourc e cod e dependenc y file, calle d pt.mak , whic h i s readb y th e mak e utilit y itself
. Th e secon d dat afile, calle d ptlink , i s rea d b y th e linke r

t o determin e th e name s o f al l objec t cod e files neede d t o buil d th e model
. Sinc e di e make utilit

y automatically determine s which sourc e cod e files mus t b e compile dt o rebuil dth e P T model , asingl e comman d i s use d t o d o s o after an y sourc e cod e modifications
. Thi s comman dis : mak e pt.ma k Us e o f thi s comman dassume s tha t th e curren t

workin g directory i s se t

t o tha t containin g th e mode l sourc e cod e an d th e pt.ma k an d pdin k

dat afiles. I n th e distributio n disk , thi s directory i s calle dsource . Sinc e us e o f aFORTRAN compile r

i s syste mdependent , step s necessar y t o acces s th e compiler

on aparticula

r syste mare no t

covere d here
.
3 8P.4 5

I f th e P T mode l i s t o b e ru n o n acompute r equippe d wit

h a n 8088/808 6 o r

80188/8018 6 processor , the n i t

mus t b e recompiled wit

h th e appropriate compile r switc h an d linked
. T o recompile di e mode l i n thi s instance , th e pt.ma k fil e mus t b e modifie d to includ e th e /G O o r /G l compiler

switc h tha

t select s th e proper

instructio n se t

Eac h comman d lin e in th e mak e file mus t b e changed
. Fo r

example , th e comman d lin e that compile s th e ptfo r

modul e appear s a s follow s i n th e distributio n versio n o f pt.mak : f l /4Yd/c/FPi/G 2 ptfo r Thi s lin e shoul db e change dt o fl /4Yd/c/FPi/G 0 pt.fo r o r f l /4Yd/c/FPi/G l ptfo r t o generat e machin e cod e for 8088/808 6 o r

80188/8018 6 processors , respectively
. A simila r chang e shoul db e mad e to th e remaining comman d lines
. If additiona l sourc e cod e module s are adde d t o th e P T model , bot h th e ptma k

an d pdin k dat afiles mus t

b e modifie dt o reflect

th e addition
. Detail s o f

thi s procedur e ca

n b e foun d i n di e relevan t

section s of

th e compiler

documentation
. 2 ) Progra m Modificatio n Provision s hav e bee n mad e i n th e P T mode l t o accommodate user-supplie d addition s that allo w simulatio n o f

caniste r purg e contro l strategie s othe r than tha t

include d i n th e distributio n versio n o f

th e model
. T o mak e suc h a n addition , th e sourc e cod e fil e containin g th e purg e contro l strateg y mode l mus t b e modified , an d th e mode l recompile d a s describe dabov e i n Sectio n 1
. In addition , achang e t o th e purgetyp e dat aite mi n th e scala r inpu t dat afil e mus t

b e mad e to selec t

us e of th e user-supplie d purg e mode l i n plac e o f di e built-i n model
. Detail s o f

thes e step s ar

e covere d in th e followin g paragraphs
. Th e purg e contro l strateg y modul e Getpurg e i s containe d i n th e file ptgetprg.fo r i n th e sourc e director

y o f th e distributio n disk
. Withi n thi s file , comment s indicat e th e portio n o f th e sourc e cod e reserve dfor user-supplie d additions
. T o add new code , th e tw o executabl e line s mus t b e deleted , a s indicate d i n th e sourc e cod e comments , an d th e appropriat e use r cod e added
. Th e purg e mode l t o b e use d durin g aP T ru n i s specifie d b y th e purgetyp e scala r dat afil e item , describe d i n Sectio n II-B-l-n , "Purg e Typ e Flag. " Durin g executio n o f

Getpurge , th e variabl e ptyp e contain s thi s value
. Value s o f ptyp e les s tha

n zer o shoul db e use dt o selec t user-supplie d models , whil e avalu e of zer o shoul d b e use d to selec t th e distributio n model
. Two parameter s ar e passe dt o th e Getpurg e modul e whic h ma y b e use d t o calculat e purg e flow rates . Thes e are a s follows : Variabl e Typ e Descriptio n spee dreal* 4 Vehicl e velocity , in mph
. acce l real*4 Vehicl e acceleration , i n mph/sec
. Th e variabl e max_purge , o f typ e real*4 , ma

y b e use d i n user-supplie d code
. Thi s variabl e contain s th e valu e specifie dfor th e maxpurg e scalar

dat aitem , describe d i n Sectio n II-B-l-d , "Maximum Purg e Rate. " I n addition , th e modul e Geth p ma y b e calle d b y 

### 3 9P.4 6

use r cod e t o estimat e engin e horsepowe r outpu t a t agive n spee d an d acceleration
. Th e callin g sequenc e fo

r thi s modul e i s a s follows : hp = gethp(speed , accel , rvec(hp_base) ) Here , spee dandacce l ar

e th e vehicl e velocit

y an d acceleratio n a

t whic h horsepower

i s t o b e calculated
. Th e thir dparameter , rvec(hp_base) , mus t appea r exactl y a s shown ; i t

i s use d t o pas s horsepowe r

conelatio n parameter s t o Gethp
. Detail s of ho w thi s thir d paramete r i s obtaine dan duse dare omitte dfor th e sake o f

brevity
. Gethp wil l return th e calculate d horsepowe r

valu e a s afunctio n value , whic h i s o f typ e real*4
. Afte r auser-supplie dpurg e mode l calculate s purg e rat e in SCF/min. , i t shoul d assig n thi s valu e t o th e variabl e purge . Th e valu e o f thi s variabl e wil l b e assigne d t o th e functio n Getpurg e itsel f

upo n retur

n fromth e function
. A possibl e skeleto n for user-supplie d cod e i s a s follow , wit

h existin g cod e show n in bold :

i f (ptyp e .It . 0 ) the n if (ptyp e .eq . -1 ) th e (calculation s fo

r first adde d model ) purg e = purge_value_l els e if (ptyp e .eq . -2 ) then (calculation s fo

r second adde d model ) purg e = purge_value_ 2 endi f els e i f (ptyp e .eq . 0 ) the n

40P.4 7



### I V Reference s 1 ) "Summar

y an d Analysi s o

f Comment s o n th e Recommende

dPractic e fo

r th e Measuremen t

of Refuelin g Emissions." , March , 1987 , U.S
. EPA/OAR/OMS/ECTD/SDSB
. 2) Note s fro

mpubli c worksho

p "Modification s t

o Evaporative an

dRefuelin g Tes t Procedure s fo

r th e Control o

f Exces s Evaporative Emissions, " Jun e 30 , 1988 , U.S
. EPA/OAR/OMS/ECTD/SDSB
. Publi c docke t A-87-11 , documen

t IV-E-58
. 3 ) "Koehl , W.J
. Jr. , "Mathematica l Model s fo

r Predictio n of

Fuel Tan

k an d Carbureto r Evaporatio

n Losses, " SA

E Pape r 690506
. 4 ) Reddy , S.R. , "Evaporative Emission s fromGasoline s an dAlcohol-Containing Gasoline s wit

h Closel y Matche dVolatilities, " SA

E Pape r 861556
. 5 ) AT L Repor t - On-roa dfue l tan k temperatures .

4 1P.4 8

* *

V Ap p endice s

A ) Distributio n Dis k Content s an d Mode l Installatio n Thi s Appendi x contain s adetaile d lis t and descriptio n o f

al l files include d in th e P T mode l distributio n disk , andinstruction s fo r installin g th e mode l fromth e distributio n disk
. Thes e topic s are covere di n Section s 1 an d 2 below , respectively. 1 ) Distributio n Dis k Content s Th e directory structur e o f th e distributio n dis k

i s a s show n i n Sectio n III-C- 1 , "Runnin g th e Model, " Director v roo t (pt)

sourc e o f

th e text . Content s o f

eac h director

y are give n below
. Fil e pt.ba t ptke y rptex e runptda t install , ba t ptfo r ptdihs.fo r ptgetprg.fo r ptcan.fo r ptinit.fo r ptdrive.fo r ptbkpg.fo r lintrp.fo r ptdoitfo r ptcheck.fo r ptdspO.for ptinde x ptgpfi o ptdim.in s gpfio.li b ptma k pdink ptex e Descriptio n

Batc h file use d fo

r runnin g the model
. Dat afile use dinternall y b y th e P T model
. Thi s file mus t b e i n th e current

director y a t th e time th e P T mode l i s run . Driver file use d t o generat

e pathname s neede d t o star t th e P T model
. Se e Sectio n 2 below
. Dat afile rea db y rptexe . Se e Sectio n 2 below
. Batc h file fo

r installin g th e P T model
. Se e Sectio n 2 below
. Main progra

mfo r th e P T model
. Diumal an

d hotsoa k modules
. Purg e contro l module
. Canister module
. Model initializatio n module
. Driv e simulatio n module
. Backl-purg e simulatio n module
. Linea r interpolatio n utility
. Even t handler module
. Inpu t dat acheckin g and verificatio n module
. Dat adispla

y module
. Dat afile require d fo

r compilation
. D o no t

modify
. Dat afile require d fo

r compilation
. D o no t

modify
. Dat afile require d fo

r compilation
. D o no t

modify
. Object cod e librar

y containin g dat ainput

utilities
. Sourc e cod e no t

included
. D o no t

modify
. Dat afile require d by mak

e durin g compilation
. Datarequire d fo

r progra mcompilatio n and linking
. PT model executabl e code
.

4 2P.4 9

dataXvp r 7297g.vp r 84109g.vp r 96116g.vp r 7297f.vp r 84109f.vp r 96116f.vp r 7297a.vp r 84109a
. vp r 96116a
. vp r 7297d.vp r 84109d.vp r 96116d.vp r 7297e.vp r 84109e.vp r 96116e.vp r 7297c.vp r 84109c
. vp r 96116c.vp r dataXvpAws 7191a
. vp r

84104a
. vp r 96116a
. vp r 7191b.vp r 84104b.vp r 96116b
. vp r data\evt nprm.ev t

ftpws.ev t ftpdi.ev t ftphtdi.evt ftpla4.ev t ldir90.ev t ldir l 17.evt ldnir90.ev t ldnir l 17.evt ldftp90.ev t hdir90.ev t hdir l 17.evt hdnir90.ev t hdnirll7.ev t Vapo r

Vapo r Vapor Vapo r Vapo r Vapo r Vapo r Vapo r Vapo r Vapo r Vapo r Vapo r Vapor Vapo r Vapo r Vapo r Vapo r Vapo r generatio n generatio n generatio n generaito n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n generatio n file, current

file, current file, current file, current file, current file, current file, current file, current file, current file , current file, current file, current file , current file, current file, current file, current file, current file, currentdata , 7. 8 #RV P fuel ,

data , 7. 8 #RV P fuel , data , 7. 8 #RV P fuel , data , 8. 0 #RV P fuel , data , 8. 0 #RV P fuel , data , 8. 0 #RV P fuel , data , 9. 0 #RV P fuel , data , 9. 0 #RV P fuel , data , 9. 0 #RV P fuel , data , 9. 5 #RV P fuel , data , 9. 5 #RV P fuel , data , 9. 5 #RV P fuel , data , 10. 5 #RV P fuel , data , 10. 5 #RV P fuel , data , 10. 5 #RV P fuel , data , 11. 5 #RV P fuel , data , 11. 5 #RV P fuel , data , 11. 5 #RV P fuel
. Vapo r generatio n file, worksho p data , 9. 0 #RV P fuel
. Vapo r generatio n file, worksho p data , 9. 0 #RV P fuel
. Vapo r generatio n file , worksho p data , 9. 0 #RV P fuel
. Vapo r generatio n file, worksho p data , 10. 5 #RV P fuel
. Vapo r generatio n file, worksho p data , 10. 5 #RV P fuel
. Vapo r generatio n file, worksho p data , 10. 5 #RV P fuel
. NPR M tes t procedure , worksho p data
. FT P test , worksho p data
. FT P plu s diumal , worksho p data
. FT P plu s high-temp , diumal , worksho p data
. FT P plu s LA- 4 drive , worksho p data
. Reproposa

l T P fo r LD V wit h integrate d on-board refueling systems , 9. 0 #RV P fuel , revise d temperatur e profile
. Reproposa

l T P fo r LD V wit h integrate d on-board refueling systems , 11. 5 #RV P fuel , revise d temperatur e profile
. Reproposa l T P fo r LD V wit h non-integrate d refueling systems , 9. 0 #RV P fuel , revise d temperatur e profile
. Reproposa l T P fo r LD V wit h non-integrate d refueling systems , 11. 5 #RV P fuel , revise d temperatur e profile
. Current FT P T P for

LD V wit h 9. 0 #RV P fuel , revise d temperatur

e profile
. Reproposa

l T P fo r HD V wit h integrate d on-board refueling systems , 9. 0 #RV P fuel , revise d temperatur e profile
. Reproposa

l T P fo r HD V wit h integrate d on-board refueling systems , 11. 5 #RV P fuel , revise d temperatur e profile
. Reproposa

l T P fo r HD V wit h non-integrate d refuelin g systems , 9. 0 #RV P fuel , revise d temperatur e profile
. Reproposa

l T P fo r HD V wit h non-integrate d refuelin g systems , 11. 5 #RV P fuel , revise d temperatur e profile
.

4 3P.5 0

dataXca n
dataXin p fordxa n Canister purg e tabl e fo

r For d (domestic)-typ e charcoal , nissan.can Canister

purg e tabl e fo

r Nissan-typ e charcoal
. sample.da t Scala r input dat afile prototyp e template
. testl.da t Scala

r inpu t dat afile fo

r sampl e tes t

run . Se e Appendi x C
. test2.da t Scala

r inpu t dat afile fo

r sampl e tes t

run . Se e Appendi x C
. dataXdr v

2 ) la4.dr v

hdurb.dr v nyc.drv Mode l Installatio n LA- 4 urba n dynamomete

r driv e schedul e tabl e Heavy-dut y urba n driv e schedul e table
. New Yor k cit y driv e schedul e driv e table
.
T o simplif y installatio n o f

the.P T mode l t o auser' s machine , abatc h file i s include d o n th e distributio n dis k

that wil l automaticall y creat e al l necessar y directories , an d cop y al l files fromth e distributio n dis k

t o th e appropriat e targe t

directory
. Thi s batc h file i s intende d t o instal l di e mode l fromth e distributio n floppy dis k t o auser' s fixeddis k

drive , whic h i s assume dt o b e driv e c: . Modification s tha t mus t b e mad e t o th e installatio n batc h file t o plac e th e mode l o n adriv e othe r tha t driv e c : o r

o n afloppy dis k

are oudine d at

th e en do f thi s section
. Th e followin g installatio n procedure s assum e that th e use r i s familia r wit h PC-DOS/MS-DO S commands , tree-structure d directories , an d th e us e o f floppy an d har d dis k drives
. If

additiona l guidanc e i s neede d i n thes e areas , user s shoul d consul t thei r computer hardware an doperatin g systemmanuals
. Th e followin g step s shoul db e followe d t o perfor mnorma l installatio n fromth e distributio n dis k t o afixed disk : 1 ) Make driv e c : (th e fixed disk ) th e curren t disk , an d chang e th e curren t directory t o tha t under whic h th e P T mode l i s t o b e installed
. Th e instal l batc h file wil l creat e a director y calle dpt , an d instal l th e mode l unde r i t a s show n i n Sectio n III-C-1 , "Runnin g th e Model. " 2 ) Plac e th e distributio n dis k i n driv e a: , an d mak

e driv e a : th e current

disk
. 3 ) Ente r th e comman d instal l t o begi n th e installatio n process . 4 ) Afte r installatio n i s complete , amessag e wil l b e displaye d t o thi s effect
. A t thi s point , th e curren t

dis k ma y b e change d t o driv e c: , an d th e distributio n dis k remove dfromdriv e a: . 5 ) Chec k tha t al l files liste d abov e i n Sectio n 1 hav e been copie d fromth e distributio n disk , an dtha

t the y ar e in thei r proper location
. 6 ) Verif y tha t th e mode l i s operatin g properl y b y runnin g th e tw o sampl e run s include d wit h th e mode l an ddescribe d in Appendi x C , "Sample Runs. "
4 4P.5 1

Installatio n o f

th e mode l t o afixed dis k

othe r tha n driv e c: , o r

t o aflopp y disk , wil l require modificatio n o f

th e installatio n batc h file install.ba t I n bot h cases , al l reference s to c : in th e origina l batc h file mus t

b e change d t o th e desire d drive
. Fo r alternat e fixeddrives , thi s referenc e shoul db e change dto th e appropriate driv e letter , whil e for installin g t o aflopp y disk , driv e b : shoul dnormall y b e specified
. Flopp y disk s mus t b e formatte d before attemptin g to instal l th e model
. I t i s no t recommende d tha

t th e P T mode l b e installe d on 360 K flopp y disks , sinc e littl e spac e wil l b e availabl e fo r outpu t files o r additional inpu t dat afiles. If th e P T mode l i s installe dwit h adirector

y structure differin g fromdia t generate d b y th e instal l batc h file, o r

i f different dis k drive s are to b e use d for

th e mode l an d for

inpu t dat a files, then i t

ma y b e necessar

y to modif y th e runptda t

file tha t i s found in th e roo t

director y o f th e distributio n disk , an d in th e p t directory a s th e mode l i s installe d b y th e normal installatio n process . Dat ai n thi s file ar e use d t o generate pathname s durin g executio n of th e p t model , an dit s forma

t i s a s follows : linel : <Model_code_pathname > line2 : <Input_data_file_pathname > Th e content s o f

th e first lin e contai n the director

y pat h o f th e file containin g th e P T mode l executabl e cod e (ptexe) , whil e th e secon d lin e contain s th e directory pat h t o th e director

y containin g scala

r inpu t dat afiles. Not

e tha t the Model_code_pathname mus t terminate i n a file, wherea s th e Input_data_file_pathname mus t terminate i

n adirectory
. Durin g executio n o f th e P T model , th e inpu t

dat afile t o b e use d i s locate d by appendin g th e user-supplie d dat afile name t o th e Input_data_file_pathname
. A s distributed , runptda t file appear s a s follows : linel : sourceXp

t line2 : dataXin

p If , fo r example , scala

r inpu t dat afiles are t o b e read fromaflopp y dis k i n driv e a : instea d o f fromth e directory ptXdataXin p a s distributed , th e runpt.dat file shoul d b e modifie d t o appea r as : linel : sourceXp

t line2 : a : Note tha t modificatio n o f

th e runpt.dat

file i s no t

neede d if th e distributio n dis k

directory structur e i s maintained
.



### 4 5P.5 2



### B ) Refueling/Exces s Evaporativ e Emission s Worksho p Dat a 1 ) Introductio n Thi s appendi

x contain s description s an

dsummarie s o

f datausedto obtain di e evaporative emission s caniste

r size s an d performance estimate s presenteda t the publi c worksho

p title s "Modification s to Evaporative an dRefuelin g Tes t Procedure s fo

r th e Contro l o

f Exces s Evaporativ e Emissions, " hel don Jun e 30 , 1988
. Thes e dataar

e presente da s astartin g point fro mwhich calculation s upo

n whic h worksho p presentation s wer

e base dca n b e carried ou t an d verified
. Dat aar e presented accordin

g t o the organization o

f Section s I I an

d H I o f thi s report. Tha

t is , source s o

f scala r dataan dthei r source ar e presentedfirst, followe

db y tabula r dataan d even t data
. I n di e cas e o

f scala r data, , dat avalue s an dthei r source s ar e presented , whereas fo r tabula r data , reference i s mad

e t o compute r dat afiles distributedwit

h the model
. 2 ) InputDat

a a ) Scalar Dat

a 

### D A vapor headspac e Fue l tan k size : All tank s ar

e 17. 6 gallon s in size , volum e o f 2. 0 gallon s i s assumed
. 2 ) Caniste r size : Variabl

e 3 ) Initia l Caniste r Load : 99.0 % o

f tota l caniste r capacity , except

fo r som e ver y larg e canisters (greate

r tha n 20.01) , i n whic h cas e avalu e o

f 98.5 % was used
. Thes e value ar

e usedt o simulat e afull y loadedcaniste

r instea d o f 100.0 % t o avoidamode

l quir k tha t allow s asmall amoun

t o f vapo r breakthroug

h fromfue l tan k vapor s during simulation o

f th e first entr y i n di e drive schedul

e table
. 4 ) Maximu

mPurg e Rate : Fo

r purg e rate s o

f 8. 0 l/LA-4 , avalu e o

f 1.7 3 i s used , an d fo r purg e rate s o

f 20. 0 l/LA-4 , avalu e o

f 4.6 5 i s used
. 5 ) Diurna l Caniste r Load : Value s o

f 25. 0 an d 40. 0 g/even

t ar e usedfo r FT P an d in-us e diurnals , respectively. 6 ) Hotsoa k Caniste r Load : Value s o

f 6. 0 an d20. 0 g/even

t ar e usedfo r FT P an d in-us e diurnals , respectively
. 7 ) Purge Delay : A value o

f zer o i s use d fo r all simulations
. 8 ) Horsepowe

r Correlation Parameters : Value s presentedin Section II-B-l- h ar e use d fo r all simulations
. b ) Tabular Dat

a 1 ) Drive Schedul

e Table : Th

e drive schedul

e i n th e file la4.dr

v i s use dfo

r all simulations
. 2 ) Canister

Purg e Table : Dat

ai n th e canister

purg e file s ford.ca

n and nissan.ca n ar e used , a s appropriate
.

4 6P.5 3

3 ) Vapor Generatio n Tables : Th e followin g table s ar e used : Initia l Fuel Temperatur

e Fue

l Volatilit y 71. 0 ° F 84. 0 O F 96. 0 O F 71. 0 ° F 84. 0 O F 96. 0 O F 9. 0 ps i RV P

9. 0 ps i RV P 9. 0 ps i RV P 10. 5 ps i RV P 10. 5 ps i RV P 10. 5 ps i RV P DataFil e

7191a.vp r 84104a
. vp r 96116a
. vp r 7191b.vpr l 84104b.vp r 96116b.vp r c ) Even tDat a

1 ) Th e followin g event

dat afiles ar

e used : Event Descriptio n procedure fo

r load-to-breakthroug h and canister pre conditioning
. 

### FT P FT P followe db y asingl e diurnal FT P followe db y a

n LA- 4 driv e FT P followe db

y ahigh-temperature Event Dat aFil e Augus t 198 7 NPR

M tes t nprm.ev t ftpws.ev t ftpdi.ev t ftpla4.ev t ftphtdi.ev t in-us e diurna

l

4

7P.5 4

C ) Sampl e Run s Thi s Appendi x describe s tw o sampl e run s that ar e distribute d wit

h th e P T mode l t o illustrat e dat aformats , ho w th e mode l ca n b e use d to simulate variou s tes t procedure s an d type s o f vehicl e operation , an d a s areferenc e to verif y prope r operatio n o f

th e model
. Sectio n 1 belo w give s abrie f descriptio n o f

th e tw o tes t

cases , whil e Section s 2 an d 3 contai n inpu t

dat afiles andmode l outpu t 1 ) Descriptio n Inpu t dat aan dmode l outpu t

fromtw o sampl e simulation s are include d o n th e distributio n disk , an dreproduce di n printe d for mat th e en d o f

thi s section
. Thes e example s may b e use dt o verif

y tha t th e mode l ha s been installe d an d i s operatin g correcdy , a s example s o f typica l inpu t

dat afile formats , an d t o illustrat e technique s availabl e t o simulat e effect s o f fue l tan k temperature s on evaporativ e emissions
. Sampl e dat afile s ar e a s follows : Input dat afile: Description : test l .da t Simulatio n o f th e FTP+LA- 4 tes t

procedure , a s presente d durin g th e Jun e 30,198 8 workshop
. Fue l temperature s durin g al l drive s ar

e assume d t o b e identical
. Diumal an d hot-soa k loading s are take n t o b e 25. 0 an d 6. 0 grams , respectively
. test2.dat Simulatio n of th e FTP+LA- 4 tes t

procedure
. Fue l temperature s ar

e continuou s fro

mon e tes t procedure even t

t o another
. Diumal and hot-soa k loading s reflec t

update d vapo r generatio n modelling , and hotsoa k loading s reflect end-of-driv e fue

l tan k temperatures . Bot h inpu t dat afiles are locate d in th e dataXin p directory , an d outpu t

fromthes e tw o example s ca

n b e foundi n dataXoutXtestl.ou t and idataXoutXtesti.out

, respectively
. Assumin g tha t th e mode l ha s bee n installe d a s describe d in Appendi x A , that th e curren t

driv e i s tha

t ont o whic h th e mode l ha s bee n installed , an d that th e curren t

directory correspond s t o th e roo t director y o f th e distributio n disk , th e followin g comman d ma y b e use d t o ru n di e firs t o f th e tw o sampl e runs : p t test l Thi s comman dwil l caus e simulatio n outpu t t o appea r on th e displa

y screen . T o verif

y tha t th e mode l i s operatin g correctly , result s ca n b e compare d t o th e content s o f th e file dataXoutXtestl.out
. I

f desired , th e comman d p t test l lptl : can b e use dt o obtai n aprinte d cop y of th e sampl e ru n output . Fo r further details , se e Sectio n III-C-1 , "Runnin g th e Model. " Th e secon d sampl e ru n can b e execute d b y substitutin g "test2 " fo

r "testl " in either

of th e tw o prototype s above
. Th e TANKSIZ E keywor d specifie s th e nomina l liqui d capacit yo f th e fue l tank , i n gallons .


### 4 8P.5 5

tanksiz e 1 17. 6 Th e MAXPURG E keywor d specifie s th e maximu minstantaneou s purg e rat e i n cfm/min . maxpurg e 1 4.3 0 Th e DIURNA L keywor d specifie s th e defaul t diurna l h e generation , i n grams . diurna l 1 1.42 0 Th e HOTSOA K keywor d specifie s th e defaul t hotsoa k h e generation , i n grams . hotsoa k 1 0.34 1 Th e DELA

Y keywor d specifie s a dela yi n th e star t o f caniste r purg e afte r th e star t o f simulation . purgedela y1 0 Th e CANSIZ E keywor d specifie s th e siz e o f al l canisters , i n liters . cansiz e 1 4. 1 Th e CANSTAR T keywor d specifie s th e initia l loading , i n percent , o f eac h o f eac h canister . canstar t 1 99. 0 Th e PARAM keywor d specifie s th e horsepowe r correlatio n parameters . para m4 .00 7 .003 8 .33 4 0.8 5 Th e PURGETYP E keywor d specifie s th e purg e strateg yindex . purgetyp e 1 0 Th e LOGFLA G keywor d specifie s i f th e entir e lo g an d plo t file s shoul d b e written . Th e firs t entr ycontrol s lo g files , whil e th e secon d entr ycontrol s plo t files . logfla g 2 .false , .false , drivefil e 2 5 data\drv\la4.drv\ \ vaporfile l 3 5 data\vpr\ws\7191a.vpr\ \ 

### 4 9P.5 6

vaporfile 2 3 5 data\vpr\ws\84104a.vpr\ \ vaporfile 3 3 5 data\vpr\ws\96116a.vpr\ \ canfil e 2 5 data\can\ford.can\ \ logfil e 2 5 data\out\pttestl . log W plotfil e 2 5 data\out\pttestl.plt\ \ eventfil e 2 5 data\evt\ftpla4.evt\ \



### 5 0P.5 7

Even t Dat a Fil e fo r sampl e ru n test l (ftpla4.evt ) drive 2 - 1 hotsoa k - 1 diurna l - 1 drive 2 - 1 hotsoa k 0. 5 drive 2 50 5 hotsoa k - 1 drive 2 - 1 hotsoa k - 1



### 5 1P.5 8

Outpu t fromsampl e run test l (testl.out ) 1? T tes t file , integr . system , ftp+la 4 drive , w s temps. , 9. 0 # fue l Calculation s begin : 10/11/198 8 14:40:1 5 Fue l tan k siz e (gal. ) = 17.6 0 Maximu mpurg e rat e (CFM ) = 4.3 0 Fo r caniste r 1 siz e (1 ) = 4.1 0 Purg e mode l inde x = 0 Driv e schedul e file : Purg e curv e table : Vapo r gen . fil e # 1 Vapo r gen . fil e # 2 Vapo r gen . fil e # 3 Lo g outpu t file : Plo t outpu t file : Even t file : data\drv\la4.dr v data\can\ford.ca n data\vpr\ws\7191a.vp r data\vpr\w3\84104a.vp r data\vpr\ws\96116a.vp r data\out\pttestl.lo g data\out\pttestl.pi t data\evt\ftpla4.ev t 137 0 entrie s rea d fo r driv e table . Titl e is : D * Th e LA 4 dat a cam e fro mMT S fil e 1402D-S0100 T (las t mo d 11-04-87 ) 12 9 entrie s rea d fo r purg e curv e table . Tim e For d Titl e is :
4 1 entrie s rea d fo r vapo r generatio n tabl e 1 . Titl e is : 71-91 F Runnin g los s vapo r gen . - 9. 0 RV P fuel , AT L on-roa d temp , profil e 4 1 entrie s rea d fo r vapo r generatio n tabl e 2 . Titl e is : 84-104 F Runnin g los s vapo r gen . - 9. 0 RV P fuel , AT L on-roa d temp , profil e 4 1 entrie s rea d fo r vapo r generatio n tabl e 3 . Titl e is : 96-116 F Runnin g los s vapo r gen . - 9. 0 RV P fuel , AT L on-roa d temp , profil e

Driv e even t # 1 Cumulativ e < Processin g typ e 2 driv e Star t tim e = 0 Driv e lengt h = 137 0 Endin g tim e = 137 0
Tota l fue l use d (lbs ) Tota l mile s travelle d Overal l miles/gallo n Tota l prg . rat e (ft3 ) Tota l H C purge d (gms ) Tota l H C vente d (gms ) H C pg' d fro mca n (g ) Fina l can . loa d (% ) Fina l can . cap . (gms ) _ = = = = = = = = even t

1 7 2 4 2 0 10 3 8 4 3 4 8 6 sv e

8 9 4 5 4 5 0 3 2 7 0 0 9 3 6 7 2 5
Hotsoa k even t # 1 Cumulativ e even t # 2 

### 5 2P.5 9

Even t type : hotsoa k H C t o caniste r (gms) : 6.0 0 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 39. 2 Fina l caniste r ca p (gms) : 80.2 5 Diurna l even t # 1 Cumulativ e even t # 3 Even t type : diurna l H C t o caniste r (gms) : 24.9 9 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 58. 1 Fina l caniste r ca p (gms) : 55.2 6 Driv e even t # 2 Cumulativ e even t # 4 Processin g typ e 2 driv e event . Star t tim e = 0 Driv e lengt h = 137 0 Endin g tim e = 137 0
Tota l fue l use d (lbs ) = 1.8 9 Tota l mile s travelle d = 7.4 5 Overal l miles/gallo n = 24.4 5 Tota l prg . rat e (ft3 ) = 20.0 3 Tota l H C purge d (gms ) = 53.2 3 Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 34.9 0 Fina l can . loa d (% ) = 31.7 1 Fina l can . cap . (gms ) = 90.1 6
Hotsoa k even t # 2 Cumulativ e even t # 5 Even t type : hotsoa k H C t o caniste r (gms) : 3.0 0 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 34. 0 Fina l caniste r ca p (gms) : 87.1 6 Driv e even t # 3 Cumulativ e even t # Processin g typ e 2 driv e event . Star t tim e = 0 Driv e lengt h = 50 5 Endin g tim e = 50 5
Tota l fue l use d (lbs ) = .9 5 Tota l mile s travelle d = 3.5 9 Overal l miles/gallo n = 23.4 4 Tota l prg . rat e (ft3 ) = 10.3 4 Tota l H C purge d (gms ) = 13.7 3 

### 5 3P.6 0

Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 7.6 4 Fina l can . loa d (% ) = 28.2 0 Fina l can . cap . (gms ) = 94.7 9
Hotsoa k even t # 3 Cumulativ e even t # 7 Even t type : hotsoa k H C t o caniste r (gms) : 6.0 0 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 32. 7 Fina l caniste r ca p (gms) : 88.7 9 Driv e even t # 4 Cumulativ e even t # 8 Processin g typ e 2 driv e event . Star t tim e = 0 Driv e lengt h = 137 0 Endin g tim e = 137 0
Tota l fue l use d (lbs ) = 1.8 9 Tota l mile s travelle d = 7.4 5 Overal l miles/gallo n = 24.4 5 Tota l prg . rat e (ft3 ) = 20.0 3 Tota l H C purge d (gms ) = 26.2 7 Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 7.9 3 Fina l can . loa d (% ) = 26.7 4 Fina l can . cap . (gms ) = 96.7 2
Hotsoa k even t # 4 Cumulativ e even t # 9 Even t type : hotsoa k H C t o caniste r (gms) : 6.0 0 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 31. 3 Fina l caniste r ca p (gms) : 90.7 2 En d o f even t fil e found . 9 event s processed . Tota l h e vente d (gms ) = .0 0 Calculation s terminate d at : 10/11/198 8 14:41:0 5 Norma l termination.. .



### 5 4P.6 1



### 3 ) Test 2 Sampl e Ru n Dat a Inpu t dat afile (test2.dat

) titl e 7 5 P T tes t file , integr . system , ftp+la 4 drive , cont . temps. , 9. 0 # fuel\ \ Th e TANKSIZ E keywor d specifie s th e nomina l liqui d capacit yo f th e fue l tank , i n gallons . tanksiz e 1 17. 6 Th e MAXPURG E keywor d specifie s th e maximu minstantaneou s purg e rat e i n cfm/min . maxpurg e 1 4. 3 Th e DIURNA L keywor d specifie s th e defaul t diurna l h e generation , i n grams . diurna l 1 1.28 2 Th e HOTSOA K keywor d specifie s th e defaul t hotsoa k h e generation , i n grams . hotsoa k 1 0.16 3 Th e DELA Y keywor d specifie s a dela yi n th e star t o f caniste r purg e afte r th e star t o f simulation . purgedela y1 0 Th e CANSIZ E keywor d specifie s th e siz e o f al l canisters , i n liters . cansiz e 1 4. 7 Th e CANSTAR T keywor d specifie s th e initia l loading , i n percent , o f eac h o f eac h canister . canstar t 1 99. 0 Th e PARAM keywor d specifie s th e horsepowe r correlatio n parameters . p a ra m4 .00 7 .003 8 .33 4 0.8 5 Th e PURGETYP E keywor d specifie s th e purg e strateg yindex . purgetyp e 1 0


### 5 5P.6 2

Th e LOGFLA G keywor d specifie s i f th e entir e lo g an d plo t file s shoul d b e written . Th e firs t entr ycontrol s lo g files , whil e th e secon d entr ycontrol s plo t files . logfla g 2 .false , .false , drivefil e 2 5 data\drv\la4.drv\ \ vaporfile l 2 5 data\vpr\7297a.vpr\ \ vaporfile 2 2 5 data\vpr\84109a.vpr\ \ vaporfile 3 2 5 data\vpr\96116a.vpr\ \ canfil e 2 5 data\can\ford.can\ \ logfil e 2 5 data\out\pttest2 . log W plotfil e 2 5 data\out\pttest2.plt\ \ eventfil e 2 5 data\evt\ldir90.evt\ \



### 5 6P.6 3

Event dat afile fo

r sampl e ru n test 2 (ldir90.evt) drive l - 1 hotsoa k - 1 diurna l - 1 drive 2 - 1 hotsoa k 1.14 0 drive 2 50 5 137 0 hotsoa k 3.0 2 drive 2 - 1 153 1



### 5 7Outpu t from sampl e ru n test l (testl.out ) P T tes t file , integr . system , ftp+la 4 drive , cont . temps. , 9. 0 # fue l Calculation s begin : 10/11/198 8 14:41:2 1 Fue l tan k siz e (gal. ) = 17.6 0 Maximu mpurg e rat e (CFM ) = 4.3 0 Fo r caniste r 1 siz e (1 ) = 4.7 0 Purg e mode l inde x = 0 Driv e schedul e file : Purg e curv e table : Vapo r gen . fil e # 1 Vapo r gen . fil e # 2 Vapo r gen . fil e # 3 Lo g outpu t file : Plo t outpu t file : Even t file : data\drv\la4.dr v data\can\ford.ca n data ^ -3r\7297a.vp r data\.pr\84109a.vp r data\vpr\96116a.vp r data\out\pttest2.lo g data\out\pttest2.pi t data\evt\ldir90.ev t 137 0 entrie s rea d fo r driv e table . Titl e is : D * Th e LA 4 dat a cam e fro mMT S fil e 1402D-S0100 T (las t mo d 11-04-87 ) 12 9 entrie s rea d fo r purg e curv e table . Titl e is : Tim e For d 5 1 entrie s rea d fo r vapo r generatio n tabl e 1 . Titl e is : 9.0 # fuel , AT L temps , 72-97F , 1. 0 gal . tan k 5 1 entrie s rea d fo r vapo r generatio n tabl e 2 . Titl e is : 9.0 # fuel , AT L temps , 84-109F , 1. 0 gal . tan k 4 1 entrie s rea d fo r vapo r generatio n tabl e 3 . Titl e is : 9.0 # fuel , AT L temps , 96-116F , 1. 0 gal . tan k

Driv e even t # 1 Cumulativ e even t # 1 Processin g typ e Star t tim e = Driv e lengt h = Endin g tim e = 1 driv e event . 0 137 0 137 0
Tota l fue l use d (lbs ) = 1.8 9 Tota l mile s travelle d = 7.4 5 Overal l miles/gallo n = 24.4 5 Tota l prg . rat e (ft3 ) = 20.0 3 Tota l H C purge d (gms ) = 111.7 4 Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 101.4 4 Fina l can . loa d (% ) = 31.9 7 Fina l can . cap . (gms ) = 102.9 6
Hotsoa k even t # 1 Cumulativ e even t # 2 

### 5 8P.6 5

Even t type : hotsoa k H C t o caniste r (gms) : 2.8 7 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 33. 9 Fina l caniste r ca p (gms) : 100.0 9 Diurna l even t # 1 Cumulativ e even t # 3 Even t type : diurna l H C t o caniste r (gms) : 22.5 6 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 48. 8 Fina l caniste r ca p (gms) : 77.5 2 Driv e even t # 2 Cumulativ e even t # 4 Processin g typ e 2 driv e event . Star t tim e = 0 Driv e lengt h = 137 0 Endin g tim e = 137 0
Tota l fue l use d (lbs ) = 1.8 9 Tota l mile s travelle d = 7.4 5 Overal l miles/gallo n = 24.4 5 Tota l prg . rat e (ft3 ) = 20.0 3 Tota l H C purge d (gms ) = 44.0 5 Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 25.6 4 Fina l can . loa d (% ) = 31.8 3 Fina l can . cap . (gms ) = 103.1 7
Hotsoa k even t # 2 Cumulativ e even t # 5 Even t type : hotsoa k H C t o caniste r (gms) : 3.2 7 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 34. 0 Fina l caniste r ca p (gms) : 99.9 0 Driv e even t # 3 Cumulativ e even t # 6 Processin g typ e 2 driv e event . Star t tim e = 137 0 Driv e lengt h = 50 5 Endin g tim e = 187 5
Tota l fue l use d (lbs ) = .9 5 Tota l mile s travelle d = 3.5 9 Overal l miles/gallo n = 23.4 4 Tota l prg . rat e (ft3 ) = 10.3 4 Tota l H C purge d (gms ) = 16.4 0 

### 5 9P.6 6

Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 8.2 5 Fina l can . loa d (% ) = 28.5 4 Fina l can . cap . (gms ) = 108.1 4
Hotsoa k even t # 3 Cumulativ e even t # 7 Even t type : hotsoa k H C t o caniste r (gms) : 8.6 6 H C vente d (gms) : .0 0 Fina l caniste r loa d (%) : 34. 3 Fina l caniste r ca p (gms) : 99.4 8 Driv e even t # 4 Cumulativ e even t # 8 Processin g typ e 2 driv e event . Star t tim e = 153 1 Driv e lengt h = 137 0 Endin g tim e = 290 1
Tota l fue l use d (lbs ) = 1.8 9 Tota l mile s travelle d = 7.4 5 Overal l miles/gallo n = 24.4 5 Tota l prg . rat e (ft3 ) = 20.0 3 Tota l H C purge d (gms ) = 28.8 2 Tota l H C vente d (gms ) = .0 0 H C pg' d fro mca n (g ) = 8.0 9 Fina l can . loa d (% ) = 28.9 2 Fina l can . cap . (gms ) = 107.5 7 En d o f even t fil e found . 8 event s processed . Tota l h e vente d (gms ) .0 0 Calculation s terminate d at : 10/11/198 8 14:42:1 2 Norma l termination.. .



### 6 0P.6 7



### D ) Vapor Generation an d Temperatur

e Profile Dat

a Thi s section describe s method s an ddat asource s use

dt o generat e diurna l an dhotsoa k canister loadings , a s well a s vapo r generatio n tables
. I

n addition , asummar

y o f uncontrolle d diurnal an

d hotsoa k emissions , generate dafte r th e Jun e 30 , 198 8 workshop(2) , i s included
. 1 ) Emission s Modellin g Value s fo r uncontrolle

d emission s fromdiurna

l an dhotsoa k events use di n connectio

n wit h th e Jun e 30 , 198 8 evaporativ e emission s worksho p an dpresente di

n Appendix B , "Refueling/Exces s Evaporativ e Emission s Worksho p Data, " wer e selecte d as approximat e bu t realisti c estimate s o

f thes e quantities
. Modification s t o an d refinement

s o f the P T mode l sinc e th e worksho p hav e includedadditiona

l modelling o

f diurna l an d hotsoa k emissions , a

s wel l a s fue l tan k vapo r generatio n rates . Modellin

g o f dies e event s has bee n carried ou

t wit h apackage , know

n as th e E E model , currend

y unde r developmen

t a t EPA
. Th e E E mode l i s base do n individua

l hydrocarbo

n specie s description s o

f fuels , an d i t ca n predict evaporative hydrocarbo

n vapo r generatio n an demission s i

n respons e t

o change s i n temperatur

e andpressur

e throug h th e us e o f rigorous thermodynamic and vapor-liqui d equilibriu

mprinciples
. Becaus e th

e E E mode l i s stil l unde

r development , documentatio

n o f i t i s no t available
. Element

s o f di e mode l applicabl e t o generatio n o f dat a neede d b y the P T model , however, ar

e base do n calculation technique s presentedi n th e literatur e b y Koehl(3 ) an

d Reddy(4)
. 2 ) Diurna

l Uncontrolle d Emission s Simulatio n o f th e mas s o f hydrocarbo

n vapors generatedduring diurna l event s has bee

n carried ou t fo r tw o diuma l temperatur

e range an dfo r thre e fue l volatilities
. Result

s o f thes e calculation s ar

e presente d below , an

dar e all basedo

n a40 % ful

l tan k an davapo r headspac e volum

e equa l t o 15.0 % o f th e liquidcapacit

y o f th e tank
. Al l value s ar e o n a basi s o f grams/(gallo

n tota l liqui dcapacity)/tes

L Diuma l Temperatur

e Rang e Fue l Volatilit y 60-8 4 ° F 72-9 6 ° F 7. 8 #RV P 0.89 5 g/gal
. 1.48 8 g/gal
. 8. 0 #RV P 0.95 0 g/gal
. 1.59 1 g/gal
. 9. 0 #RV P 1.28

0 g/gal
. 2.23 3 g/gal
. 9. 5 #RV P 1.52

4 g/gal
. 2.75 0 g/gal
. 10. 5 #RV P 1.96

0 g/gal
. 3.760 g/gal
. 11. 5 #RV P 2.60 1 g/gal
. 5.509 g/gal
. 11. 7 #RV P 2.74

7 g/gal
. 5.96

4 g/gal
. 3 ) Hotsoak

Uncontrolle dEmission s Uncontrolle

d hotsoa k emission s hav

e bee n estimatedfo

r th e three fue l volatilitie s use

d fo r simulatio n o f diuma l emissions , an

dfo r anumbe r o f fue l tan k temperature s correspondin

g to end-of-driv e temperature s encountere ddurin g driv e simulations
. Unlik e diurna l emissions , EP

A doe s no t hav e arigorous, mechanistic mode l o f hotsoa k emission , s o dia

t asemi-empirica

l approac h was take n t o obtai n th e neede destimates
. I

n thi s approach , it was assumed tha

t hot-soa k emission s originat

e primaril y fromth e fue l tan k a s i n fue l 6 1P.6 8



### injecte d vehicles , an

d tha t atemperatur

e increas e o

f 0. 6 ° F i s experiencedb

y th e content s o f fue l tank s durin g hotsoaks
. Using th e sam e fue l tan k fill level an

d vapo r spac e assumption s as wer

e applied t o diuma l emission s estimates , th

e quantit y o f hydrocarbo

n vapors emitte

d fro mafue l tan k durin g ahotsoa k wa s calculate dusin g th e E E model
. Next, amultiplicative facto

r wa s applie dt o thes e value s suc

h tha t th e quantit y o f emission s from hotsoaks afte

r adrive wit

h afina l fue l tan k temperatur

e o f 99. 0 ° F (typica

l afte r a n LA-4 drivin g cycle performe

d o n adynamometer

) an d9. 0 #RV P fue l was 6. 0 g/test
. A value o

f 3.09 was foun

d fo r thi s multiplicativ e factor , an d i t was appliedt

o hotsoa k emission s estimate s fo

r al l thre e fue l volatilities
. Th

e valu e o f 6. 0 g/tes t was selectedt

o maintai n consistenc y wit h earlie r EP A evaporativ

e emission s modelUng
. A summar y o f results fro m hotsoa k emission s modellin

g i s show n below , alon

g wit h th e rati o o f emission s a

t eac h indicate d temperatur

e t o bas e emission s a

t 80. 0 °F
. Thes e rati o value s ca n be use d as hotsoa k even t parameter s whe

n preparing even

t files, a s describe din Section ni-B-3 , "Even tDat a Preparation. " Unit s fo r othe r value s ar e grams/(gallo n tota

l liqui d capacit y )/tes t Fue l RV P End-of-Driv e Temperatur

e 84. 0 ° F 96. 0 ° F 99. 0 ° F 103. 0 ° F 108. 0 ° F 111. 0 ° F 7. 8 #RV P Basi c Em
. Adj
. Em
. Rati o 8. 0 #RV P Basi c Em
. Adj
. Em
. Rati o 9. 0 #RV P Basi c Em
. Adj
. Em
. Rati o 9. 5 #RV P Basi c Em
. Adj
. Em
. Rati o 10. 5 #RV P Basi c Em
. Adj
. Em
. Rati o 11. 5 #RV P Basi c Em
. Adj
. Em
. Rati o 11. 7 #RV P Basi c Em
. Adj
. Em
. Rati o 0.035 6

0.110 6 1.000 0.038 0 0.118 0 1.000 0.052 6 0.163 5 1.000 0.064 0 0.198 1 1.00 0 0.085 6 0.265 9 1.000 0.119 8 0.372 3 1.000 0.128 1 .398 0 1.000 0.061 8

0.192 2 1.73 7 0.066 7 0.207 2 1.75 6 0.098 8 0.306 9 1.87 7 0.126 9 0.392 6 1.98 2 0.188 5 0.585 8 2.20 3 0.319 1 0.991 6 2.66 4 0.359 0 1.115 0 2.80 2 0.072 0

0.223 6 2.02 2 0.077 9 0.242 1 2.05 2 0.118 5 0.368 1 2.25 1 0.155 9 0.482 2 2.43 4 0.243 0 0.757 0 2.84 7 0.463 0 1.43 9 3.86 4 0.540 9 1.681 0 4.22 3 0.089 2

0.277 2 2.50 6 0.097 2 0.302 0 2.55 9 0.154 8 0.480 9 2.94 2 0.212 8 0.612 8 3.09 3 0.370 4 1.151 0 4.32 8 0.976 7 3.03 5 8.15 1 1.32 3 4.11 9 10.33 0 0.119 8

0.372 1 3.36 4 0.132 0 0.410 2 3.47 7 0.229 7 0.713 7 4.36 5 0.347 1 1.073 6 5.419 5 0.822 1 2.55 4 9.60 7 3.285 3 10.20 8 27.42 0 4.67 2 14.52 0 36.48 0 0.145 7

0.452 7 4.093 5 0.162 2 0.504 0 4.27 1 0.306 6 0.952 6 5.82 6 0.515 0 1.593 0 8.04 1 2.164 0 6.725 0 25.29 1

_

-

-

.

-

- 

### 6 2P.6 9

•**
.

4 ) Vapo r Generatio n Vapo r generatio n table s fo

r th e PT mode l wer

e constructe d a s oudine d i

n Sectio n UI-B-2-c , "Vapo r Generatio n Table. " Th e vapo r generatio n tabl e require d by Step 1 o f thi s procedur e wa s obtaine dusin g th e E E mode l describe d above , whil e th e time/temperature tabl e require dby Step 2 wa s obtaine d fromexperimentally-obtaine d fue l tank temperature data
. Thi s sectio n give s abrie f overvie w o f

ho w eac h of

thes e dat asource s wer e use d t o obtai n th e neede dinformation
. Th e EE mode l wa s use dto predic t vapo r generatio n durin g vehicl e operatio n b y assumin g tha t fue l tan k vapor s ar e produce d in respons e t o increase s i n th e temperatur e o f tank contents . Therefore , atemperature/vapo r generatio n tabl e wa s obtaine d b y simulatin g a fue l tan k temperatur e ris e coverin g th e rang e expecte d durin g driv e events , with intermediat e outpu t

obtaine da

t temperature interval s o f

0. 5 °F
. Al l suc h simulation s wer e carrie dou t

assumin g 40 % full fue

l tanks , aheadspac e volum e o f 15 % o f tota l liqui d capacity , an dpressure equal t o ambient atmospheri c pressure . Fue l tan k time/temperature dat awa s obtaine d fro mexperimenta

l on-roa d studie s carrie d ou t i n connectio n wit

h EP A vehicl e testing(5)
. Thes e dat agiv e averag e fue l tank temperature s a t severa l point s durin g extended , continuou s drive s fro maflee t o f 1 6 vehicles
. Eac h driv e consiste do f

repeatedexecution s o f

on e o r mor e drivin g cycles , suc h a s LA- 4 o r HFE T cycles
. Dat ause dfor

developmen t

o f th e P T mode l were fro mdrive s consistin g o f thre e LA- 4 drivin g cycle s performe d back-to-back , wit h ashor t paus e betwee n eac h cycl e t o recorddata
. Fro mthes e individua l time/temperature dat apoints , asecond-orde r regressio n polynomia l wa s calculate ds o tha t th e time neede d t o reach agive n fuel temperatur e coul d b e obtained
. Dat agiven b y th e TimeATemperatur

e Tabl e exampl e i n Sectio n HI-B-2- c wer e generate dfromthi s polynomial
.



### 6 3E ) Summar y o f Mode l Change s Betwee n Release s 1. 0 an d 2. 0 Thi s Appendi x outline s al l major change s mad e t o di e P T mode l betwee n Releas e 1. 0 an d Releas e 2.0 , alon g wit

h references t o section s documentin g eac h chang e an d th e dat afile modifications , if

any , necessar

y to accommodat e th e change
. Not e that becaus e several new scala r inpu t dat aitem s hav e bee

n adde d t o Releas e 2.0 , existin g Releas e 1. 0 scala r dat a files mus t b e modifie dbefor

e us e widi Releas e 2.0
. 1 ) Canister

Loadin g Mode l Changes
. a) A ne w scala

r inpu t dat aitem , cantype , i s no w require d i n al l inpu t dat afiles. Se e Section s II-l-B- p an d IJI-B-l
. b ) Th e cansiz e scala

r inpu t dat aite mno w require s tha t th e caniste r

breakthroug h capacity b e specifie d when th e non-ideal caniste r loadin g mode l i s selecte d ( a valu e o f 1 i s specifie d fo

r th e first valu e o f th e cantyp e scala

r dat aitem)
. Se e Section s U-l-B- b an d III-B- 1 2 ) Canister

Purg e Mode l Changes
. a ) A ne w scala

r inpu t dat aitem , pcurvetype , i s no w require d in al l inpu t dat afiles. Se e Section s II- 1 -B- o and JJI-B-1
. b ) Whe n avalu e o f

1 i s specifie d for

th e pcurvetyp e scalar

inpu t dat aitem , indicatin g tha

t analytical purg e curve s are to b e use d instea d o f apurg e curv e table , th e caniste r

dat afil e fordeq.can mus t b e use d instea d o f

ford.can o r nissan.can
. Note : N o erro r checkin g i s performe d b y th e P T model t o determin e if

th e caniste r

dat afile forma

t matche s th e forma

t associate d wit

h di e specifie dfor

th e pcurvetyp e scalar

dat aitem
. User s ar e responsibl e fo r consistenc y betwee n th e expecte d an d actua l dat afile formats
. Se e Sectio n III-B-2-b , "Caniste r Purg e Table. " 3 ) Back-purg e Event

Typ e Addition
. a) A new even t

typ e ha s been adde d t

o simulat e canister back-purg e durin g period s o f decreasin g fue l tan k

temperature s that

ma y occu r afte r diuma l o r

driv e events . An even t

typ e o f backp g ma

y b e specifie d even t

dat afiles t o simulat e back-purg e events . Se e Section s II-B-3- d and HI-B-3
. b ) A ne w scala

r inpu t dat aitem , bprate , i s no w require d i n al l inpu t dat afiles. Se e Section s II-l-B- q an d III-B-1
. 4 ) Vapo r

Generatio n Dat aFil e Updates
. a ) Change s hav e bee n mad e t o th e followin g vapo r generatio n table s t o reflec t results fro mupdate d modellin g of

fue l tan k vapo r generatio n a

t and nea r th e fue l boilin g point
. Thes e dat afile s shoul d b e use d i n plac e o f th e ol d vapo r generatio n dat afiles in simulation s where fue l boilin g ma

y influenc e P T mode l results
.



### 64