United States
Environmental Protection
Agency
Research and Development
Atmospheric Sciences Research
Laboratory
Research Triangle Park NC 27711
~EPA/600/S3-85/032 June 1985
ii'
&EPA Project Summary
Outdoor Smog Chamber
Experiments Using Automobile
Exhaust
H. E. Jeffries, K. G. Sexton, T. P. Morris, M. Jackson, R. G. Goodman, R. M.
Kamens, and M. S. Holleman
The smog chamber facility of the Uni-
versity of North Carolina at Chapel Hill
(UNC) was used in a study to provide
further experimental data for develop-
ing and testing kinetic mechanisms of
photochemical smog formation. The
smog chamber, located outdoors in
rural North Carolina, is an A-frame
structure supporting Teflon film. Be-
cause the chamber is partitioned into
two sections, each with a volume of
156 m3, two experiments can be con-
ducted simultaneously. The dual cham-
ber is operated under natural conditions
of solar radiation, temperature, and rel-
ative humidity.
In this study, 33 all-day dual experi-
ments were conducted using exhaust
from two automobiles. The purpose of
this study was to supplement the exist-
ing UNC smog chamber database with
experiments that involved the complex-
ity of real automobile exhaust. These
data, with other experiments, could be
used to test and improve mechanisms
for use in the Empirical Kinetics Model-
ing Approach (EKMA) technique for
calculating control requirements need-
ed to achieve the ozone standard.
This report describes the experimen-
tal methods and procedures used, the
automobiles tested, and the results of
the 33 dual smog chamber experiments
conducted in the two years of this pro-
ject. Two automobiles were used: an
uncontrolled 1972 Dodge Charger and
a catalyst-equipped 1979 Plymouth
Volare. All experiments were side-by-
side dual experiments. Types of exper-
iments conducted were matched initial
conditions of exhaust from each vehi-
cle, matched initial conditions of ex-
haust from both vehicles using the same
gasoline, matched initial conditions
comparing cryocondenser collected ex-
haust with directly injected exhaust,
matched initial conditions experiments
comparing synthetic auto exhaust with
directly injected exhaust, differential
exhaust injections with matched nitro-
gen oxides for testing an EKMA control
strategy reduction, and matched initial
conditions comparing exhaust from
premium and regular gasoline for the
same car. In addition to the chamber
tests, the cars were tested each year on
dynamometers at the EPA Mobile Sourc-
es Emissions Research Branch
(MSERB), and detailed HC composition
of the exhaust was determined both by
MSERB analysis and by analysis at U N C
using a capillary column gas chromato-
graph and a high resolution double foc-
using mass spectrometer.
General findings and observations
were direct injection of auto exhaust
from one vehicle operated at high idle
gave identical reactivity in the two
chamber halves, direct injection of
exhaust in one chamber side and cryo-
genically trapping exhaust with subse-
quent evaporation into the other cham-
ber side gave the same results when
reactant masses were the same, direct
injection from both vehicles into separ-
ate chambers with equal HC and NO,
concentrations resulted in slightly more
reactivity from the controlled vehicle,
direct injection of exhaust from the
same car using premium gasoline and
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regular gasoline in separate chambers
resulted in the same reactivity, and
exhaust injection using regular gasoline
with a reduction of hydrocarbon of 60%
between the two chamber sides (at the
same initial NO, and at a HC-to-NO*
ratio of 10 on the high HC side) resulted
in a 30-35% reduction in peak ozone.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
The Bureau of Mines (BOM) auto
exhaust database has been used for more
than 12 years to validate model predic-
tions for Os as a function of oxides of
nitrogen (NO,) and hydrocarbons (HC).
Although it has been used, through
OZIPP/EKMA, in the standard setting
process, the BOM data present signifi-
cant problems for use in today's photo-
chemical mechanism validation.
The purpose of this project was to sup-
plement an existing smog chamber data-
base with experiments using automobile
exhaust so that modelers can test and
develop improved photochemical reaction
mechanisms for use in EKMA to calculate
control requirements for meeting the
ambient ozone standard. In this project,
the dual outdoor smog chamber facility at
the University of North Carolina at Chapel
Hill, which is operated using ambient
sunlight, near-ambient temperatures,
and realistic water vapor conditions, was
used to provide a close approximation of
actual atmospheric conditions. In addi-
tion, at the start of this project, a large set
of experimental tests were already avail-
able from the UNC chamber that ad-
dressed many model development and
testing issues. This project extended the
existing test set to include experiments
emphasizing the unique aspects of auto-
mobile emissions, such as the effect of
gasoline composition on reactivity and
whether the models can correctly predict
such effects.This study was performed by
UNC under Cooperative Agreement No.
809391.
Background discussion in the report
describes the complexity of automobile
exhaust and the problems this complexity
creates for sampling whole automobile
exhaust, analyzing the reacting species,
and modeling the results of chamber
experiments.
Approach
The controlled vehicle used in the study
was a 1979 Plymouth Volare, and the
less-controlled vehicle was a 1972 Dodge
Charger. The UNC facility and the analyti-
cal system used in this study are des-
cribed in detail in report appendices.
The automobiles were tested several
times throughout the study on dynamo-
meters at the Mobile Source Emissions
Research Branch at the EPA laboratories
in Research Triangle Park, NC. Dynam-
ometer tests performed were the stand-
ard Federal Test Procedure, the New York
City Cycle, the Cruise and Urban Extended
Cycle, and high idle for emissions rate per
mile and for emissions detail hydrocarbon
composition and class analysis. EPA/
MSERB data from testing of a fleet of in-
use vehicles at the same time as several
of the dynamometer tests on UNC vehi-
cles provided comparison for the UNC test
vehicles. In the chamber tests, exhaust
hydrocarbon speciation, total NMHC,
detailed aldehyde and oxygenates, CO,
PAN, organic nitrates, NO,, and 03 data
were obtained.
To transport samples between the UNC
facility and MSERB, a cryocondenser
method was developed. Experiments
were performed to test the cryocondenser
in which samples were taken directly
from the vehicle exhaust pipe and then
injected from the cryocondenser into one
chamber. Exhaust from the same vehicle
was injected at the same time into the
other chamber, and results were com-
pared. The cryocondenser injection meth-
od is described in detail in the report. The
other injection methods used were direct
exhaust injection from one car into both
chambers, direct exhaust injection from
one car using premium gas into one
chamber and the same car using regular
gas into the other, direct injection from
two cars (one into each chamber) and
direct exhaust injection in one chamber
with synthetic mixture injected into the
other.
Results
Supporting data from the dynamometer
tests are explained in a series of tables
showing the emissions recorded by test,
car, and year. A table of the HC species as
identified by MSERB is also included. In
analyzing the data, UNC performed a
species identification by sampling at
MSERB with the cryocondenser. A mass
spectrometer and four gas chromato-
graphs were used to analyze the samples.
The differences between the exhaust
composition based on UNC data and
MSERB data are discussed and shown in
several graphs.
Data from the cryocondenser exper-
iments showed that the sampling method
performed well, without a detectable
effect upon the hydrocarbon composition.
Analyses of the gasolines were also
performed, and these comparisons are
presented. Selected HC composition data
tables and the techniques for the calibra-
tion of NMHC instruments are described
in appendices.
The report presents a summary table of
the initial conditions of each of the 33
experiments performed. Following this
table is the general documentation for
each experiment, which describes the
purpose, initial conditions, special con-
cerns, and results and plots for N0,/03,
temperature and dew point for each
experiment. For the most complete exper-
iments, a detailed listing of the initial
concentrations of the measured HC spec-
ies are given. These speciated HCs ac-
count for 70-90% of the measured NMHC.
By using average carbon numbers in each
HC class computed from the detailed GC
and GCMS analysis of tail pipe exhaust,
the unspeciated HC in the smog chamber
experiments was divided into HC classes
with an assigned carbon number. This
allows modelers to include the unspec-
iated HC in the most appropriate manner.
General findings and observations
were:
• direct injection of automobile exhaust
from a vehicle operated at high idle,
when split between the two chambers
every one second, gave identical re-
activity in the two chambers;
• direct injection of automobile exhaust
in one chamber and cryogenically
trapping the whole exhaust volume at
the same time with subsequent evap-
oration of the trapped exhaust into the
other chamber gave essentially ident-
ical results when the initial reactant
masses were the same; several exper-
iments were necessary before the
exact same mass could be collected in
the cryocondenser as was injected
into the chamber;
• direct injection of exhaust from one
vehicle into one chamber and direct
injection of exhaust from the other
vehicle into the other chamber at the
same HC and NO, concentrations
showed that the exhaust from the
controlled vehicle was slightly more
reactive;
• when the same vehicle was used to
directly inject exhaust from premium
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gasoline into one chamber and ex-
haust from regular gasoline into the
other chamber, the reactivities of the
two sides were essentially the same,
even though the exhaust compositions
were different;
• in two experiments with regular gaso-
line and differential injection of ex-
haust so that one side had only 60% of
the HC of the other side and with direct
injection of NO, to balance the initial
NOx in the two sides, the peak 03 on
the low HC side was 30-35% of that on
the full exhaust side; the HC-to-NO*
ratio on the high HC side was =10.
Obtaining Data
This data set has been supplied to
modelersfor analysis under EPA Contract
Nos. 68-02-3738 and 68-02-4104. This
report describes the data so others in the
scientific community may use it. Fully
processed runs are available on an ANSI
formatted magnetic tape. Copies of the
tape and other supporting information
are available through the authors.
H. E. Jeffries, K. G. Sexton, T. P. Morris, M. Jackson, R. G. Goodman, R. M.
Kamens, andM. S. Holleman are with the University of North Carolina, Chapel
Hill, NC 27514.
Mar da C. Dodge is the EPA Project Officer (see below).
The complete report, entitled "Outdoor Smog Chamber Experiments Using
Automobile Exhaust," (Order No. PB85-191 708/AS; Cost: $25.00, subjectto
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U.S. GOVERNMENT PRINTING OFFICE: 1985-55&O16/27078
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