U.S. DEPARTMENT OF COMMERCE
(Utiooai Technical Infomution Service
PB-289 934
Effect of Altitude on Non-Controlled
Evaporative Emissions from
Gasoline-Fueled Vehicles
(U.S.) Environmental Protection Agency, Ann Arbor, Mi
Jan 79
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Technical Report
Effect of Altitude on Kon-Controlled Evaporative Emissions
from Gasoline-Fueled Vehicles
January, 1979
Michael W. Kcifcr-nan
NOTICE
Technical reports do not necessarily represent final EPA decisions or
positions. They arc intended to present technical analynts of issues
using data which arc currently available. The purpose in th<* rclrae? of
such rcportr. is to facilitate the exchange of technical Information and
to inform tlie public of technical developments which nay form the basis
for a final EPA decisions, posJ'ion or regulatory action.
Standards Hcvelopncnt and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air, JCoise and Radiation
U. S. Environmental Protection Apcncy
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TECHNICAL REPORT DATA
ifttdtr rtatiIntcvfnons on thertttrie beforecomptennf).
5. REPORT DATE ., _ _,
January, 1979
Evapora-
chicles
6. PERFORMING ORGANIZATION CODE
7. AUTMORIS)
Michael W. Leiferman
8. PERFORMING ORGANIZATION REPORT
SDSB 79-01
. PERFORMING ORGANIZATION NAME AND ADDRESS
Standards Deve'Iopinpent a-nd Support Branch
Emission Control Technology Division
J.S. Environmental Protection Agency
Vnn ArRor. Michigan '18105
TJ. SPONSO"R"IN
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:Altitude ou Xoit-Coritrollcd Evaporative Emissions
^?rr; '£r<:£5 Gasoline-Fuelcd Vehicles
I. Introduction
0 reiK&;ejd interest in control of evaporative cnissions at
ija«fe,:»,,. ij: ,,.has become necessary to establish the difference in
OTaissions between locations near sea level
and locations in hi^h altitude areas. Determine! ti on of this difference
in cnissions will result iii the identification of control standards for
hip.li altitude which ?iven sinilar percent reductions .is standards in
effect for low altitude areas.
II. Discussion
There is very little published test data which compares evaporative
emissions at different altitudes. However, there has been considerable
testing done for the effect of fuel volatility on evaporative emissions.
There have also been mathematical models developed for th" prediction of
evaporative losses. These models generally have a theoretical basis and
have been shown to agree with experimental data gathered under low
altitude condition;-,. It appears that these models are applicable to
prediction of evaporative losses at different altitudes.
A. Diurnal Loss _ •.' • *"
-For the diurnal test conditions, the following equation derived by
Wade is applicable for prediction of non-controlled fuel tank losses:
454 M
ce R
where:
C ~ Weight of fuel lost, g
Ib
M » Molecular weight of fuel vapor
V ™ Volume of tank vapor space, ft
T « Temperature, °R
P = Atmospheric pressure, psia
a
P » Fuel tank pressure, psia
p = Partial pressure of fuel, psia
P - (P! + p2)/2
-Si-
lo .-nolc
3
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i = Initial state
2 •• Final state
R «= Ideal gas Constant" 10.73
ft3
°R lb-r=o]e
C = Cbaprcssibility factor.
£
The conpressibility factor (C ) value can be obtained frora the
& 2
following two equations contained in an Al'I publicntioa :
Z - (379.5) V C , 14.7 .
_ _£. ( _ )
M P
ar.d also,
Z - 690 -
where Z » Volume of saturated vapor at 60*F and 14.7 psia per
gallon of liquid, ft
U - Weight of 1 gallon of liquid, pounds
P « Fartial pressure of the hydrocarbon in vapor at
saturation, psia.
Coabining the two above expressions for Z gives
C - (690-4M) M
8 14.7 (379.5 W)
Substituting this into Wade's equation gives the following expression
from which diurnal losses can be calculated:
G -
454W
690-4M
» . •*
P
/•" ?.
4
•
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M" 62 lb BOlc
V • 1.60 ft (Fuel tank volume » 20 gallons)
f « 14VZ'.g»£a-..a-.c- soa icvcl.-
a » \i'a-i'at;5200^cei:-:'
P. « 4.6 psia, P, • 7.2 psia
The results arc lifted in Table 1. As shou-a, the calculated loss
at sea level is 20.0 grass and at 5200 feet is 27.0 grams.
Bi Hot-soak Loss
In regard to cavburctor hot-soak losses, Wade has shown that the
fuel boiling proco:;? can be closely approximated by a single plate
equilibrium distillation process, end the aaour.t of fuel loss correlated
veil with this distillation curve at the peak carburetor temperature.
On this basis, an equation has been proposed fcr the prediction of
carburetor hot-soak losses. Hovever, since single-plate distillation
data arc not comrecnly available on gasolines, this equation can not
normally be used.
A more practical solution has been the development of empirical
relationships between non-controlK'd carburetor losses and the ASTM
distillation results; at the peak carburetor bowl temperature. Such
relationships can be used to predict the effect of altitude on car-
buretor hot-soak losses sipcc altitude lias a known effect on the AST!-!
distillation temperatures. The following empirical relationship has
been used to predict ihe effect of altitude on non-controlled carburetor
hot-soak emissions:
where: C - Mass of fuel lost, g
B « Volume of fuel in bowl, cc
- W - Density of fuel, g/cc
V « Volume Z distilled at peak, bowl temperature
• - Constant « 0.801
b - Constant - 4.38.
Assumed values used were:
B - 100 ce
W - 0.74 g/cc
Peak gasoline temperature in carburetor bowl » 165*F
From inspection distillation data on Indolcne fuel,
V - 222 at sea level
C - 25. K at 5200 ft.
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TAB1.E I
Estimated Diffurcncc in Non-Controlled r.vnporntlve
titission Test I'.OMiltt; Kcli.ven Si-a. Level and an
Altitude of 5200 Feet
Sea Level 5200 Keet 2 Increase
Diurnal Loss, &
Hot Soak Loss, g
Diurnal and Hot Soak, &
20.0
9.8
29.8
27.0
11.9
38.9
35
21
31
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The results arc listed In Table 1. As shown the estimated hot-soak
losr.os a»: sen level and 5200 ft. are 9.8 g and 11.9 g, respectively.
C. Sursnary
Table 1 shows the calculated difference in evaporative emission
test levels between ses level and a representative hlrh altitude
location (5200 feet). The sea level and high altitude values (combining
both diurnal and hot-soak losses) are 29.8 g and 35.9 g, respectively,
an increase of 31* when going frora sea Ieve7 to 5200 feet.
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References
3. D. 1. V;idc, "Factors Inflt-encing Vehicle Evaporative Emissions",
SAE Taper 67012G, January, 1967.
2. "Evaporative Losses in the Petroleum Industry", API Bulletin No.
2513, American Petroleum Institute, February, 1959.
3. Billcr, Manof£, Sachdev, Zegel, and V.'ade, "Mathematical Expression:
Relating Evaporative Emissions from Motor Vehicles without
Evaporative LORS Control", SAE paper 720700, 1972.
4. 1974 Annual Book of ASTK standards, Part 23, p 8-19.
5. V7. J. Koehl, Jr., "Mathematical Models for Prediction of Fuel
T-ink and Carburetor Evaporative Losses", SAE paper 690506, Hay,
1969.
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