of for
D. Harris and Foy G. King
U. S, Environmental Agency
Laboratory
Park, NC
INTRODUCTION
Ambient air have not
to control in the U,S,
as the pollutants, {1,2} Sulfur
oxides monoxide markedly
reduced by strict emission for mobile
and The formation of ambient
ozone is in the urban atmosphere with
either volatile organic chemicals fVQCsJ or
nitrogen (NOx) the rate controlling
depending upon the relative ratio
present. Much of the ozone reduction effort has
been focused on VOCs through hydrocarbon
emission limits from the same sourc.es, NOx
control centered on spark ignition
vehicles using engine modifications and catalytic
tailpipe treatment. Modifications to compression
ignition engines have to reduce these
emissions, but work is ongoing to make similar
emissions reductions from compression ignition
engines,
Current models rely upon emission
inventories for to estimate effects
that control strategies could have on future
pollutant reduction scenarios. Most of the
inventory data are from samples taken from the
sources during normal operations. Mobile
inventory have relied upon laboratory
dynamometer data using a variety of
fundamentally and experimentally derived
conversion factors to estimate in-use emissions.
Thts link has not beer, extensively confirmed due
to problems emissions from m-use cars
trucks. This study endeavors to confirm or
modify those conversion factors by building a
facility which will allow sampling from heavy-
duty diesel vehicles (HDOVs! and the
development of appropriate models for
operations related emission factors.
The objectives of this project are to: 1}
define on-road emissions from HDOVs; 21
agreement among engine and chassis
Acurex Environmental Corp,
P.O. Box
Triangle Park, NC
dynamometers and on-road emission factors; 3)
evaluate current conversion factors for
dynamometer develop appropriate ones
if needed; 4} a modal emissions
model. The on-road component an
instrumented 45-foot* cargo van traiier to
various tractors during on-road operation
according to a modal matrix, These results are
to those obtained during actual runs
over routes. A separate road version of
a certification cycle is to provide a link
to the dynamometer The tractors will be
tested using a chassis dynamometer to check
with that testing method using urban
driving cycles, modal cycles, and an
of the certification cycle. The engine from the
and dynamometer truck will
be to EPA's Office of Mobile Sources for
testing on their engine dynamometer to directly
compare with the on-road *or the
certification cycie and to check against the
original Test Procedure {FTP} certification
data.
Our experimental approach involves on-
road testing according to the test matrix shown
in table 1. This test sequence develops the
modal necessary to model the emissions as
a function of speed, load, grade, and
acceleration. These are fitted to each of
three routes representing; 11 trans-urban
interstate travel, 21 terminal entry'exit, and 3^
urban delivery. The actua! routes are run, and the
emission factors generated are compared to the
model results, A final test sequence
utilizes a certification cycie that has been
to suit actual truck operational capability
to develop data for direct comparison with the
dynamometer
The modal experimental design utilizes
four-lane iimited access highways with Song and
relatively straight sections at three grades. These
* Metric equivalents appear s>. the «nci of this paper
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Table 1: General Test Matrix {Each Tractor)
Slow 15 MPH {constant speed)
Speed Medium 35 MPH (constant speed)
Fast 55 MPH (constant speed)
Accleration Normal Shift gears as governed
0 to 55 MPH Short Shift Shift @ 80-90% governed engine speed
Level 0% U.S. 70 near New Bern, NC
Grade Moderate 2-3% 1-26 near Hendersonvitie
Steep 5-7% 1-26 near Hendersonviile
Downhill Steep 5-7% Load variation only
Light Empty Trailer (25000 - 30000 Ib GCW)
(GCW) Medium % Max Cargo Load (up to 55000 ib GCW)
Heavy Max Cargo Load (up to 80000 Ib GCW}
{3 Speeds + 2 Accelerations)*(3 Grades » 3 Loads) -f Downhill = 46 Triplicate Tests Maximum
highways provide a safe operating area for
sometimes very slow moving vehicles when
testing is confined to low traffic load times. The
extent to which the matrix is completed depends
upon the vehicle power available to pull some
loads up grades as steep as 7%. A coast-down
test per White and Korst {3} is run for each
vehicle to develop the power requirements for
each configuration.
Two preliminary test sequences were
conducted to develop familiarity with diesel
engine testing and specific test procedures, A
diesel powered generator set was tested to
familiarize personnel with the effects of load on
monitored parameters and establish the ranges of
these parameters, A bank of resistive loads could
be switched to simulate the ioad-basad test
procedure, A more complete development phase
was conducted using a diesel powered pickup
truck and a horse trailer to simulate the HDDV
tractor-trailer.
The first step was to Identify the
appropriate road sections to conduct the test
matrix. The North Carolina Department of
Transportation fNCDOT) provided detailed site
plans of sections which met our grade and
distance requirements as weil as practical
recommendations to guide our selection, Leve!
grades were easy to find near the Atlantic coast
of North Carolina, and a 0.0%, 20-mile long
section of U.S. 70 near New Bern was selected.
This has the added advantage of including a large
rest area which we could use for short term
staging. The 3 and 7% grades are numerous but
usually too short to meet our requirement for at
least 60 seconds of continuous data acquisition.
The NCDOT located a stretch of Interstate 26
south of Hendersonviile which includes both
slopes. It too has a rest area nearby for staging.
The development of the sampling and
analysis system was based upon designs by
the authors during stationary source monitoring
projects. A continuous emission monitoring
(CEM) bench was assembled from backup units
available from ongoing laboratory projects. This
short rack-mounted unit was set into the horse
trailer on instrument shock mounts. A computer-
based data acquisition system operating labtech
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Notebook software was mounted on the
instrument rack with shock padding. The
pickup was wired with sensors, and a heated
sampling line connected the tailpipe to the
sample conditioning system in the trailer storage
bay. Since these instruments operate on 110 volt
AC, a gasoline-powered generator was mounted
in the pickup bed. The monitored parameters,
Table 2: Monitored Parameters
Emissions Msamireaeats Operational
o, (*>
CO, !t>
CO (ppm)
HO, fppm)
WC fppai
Exhaust Flow {scfffl)
Vehtcte Speed inpht
togiae $p«d Irp
Bat: G- Force —-iiL
•
X JL
, TWO i |0»
!
KOia
LI
Computerized
Daft; Acq
System
T I
Figure 1: Pickup Test Facility Schematic
(smoke meter) at the end. A sheath air system
was added to the smoke rneter to limit
contamination on the lenses. The sample port is
closely coupled to an electrically controlled ball
valve which allows either exhaust or calibration
gas to flow through the entire sampling system.
This provides total system quality assurance
Stack Measurements
Hi
Engine Measurements ,«•«« -^i"S?
4*ara-:- £^BXiM-.?
O h=- S^
Operational yeasurements
i Ata»et*n,t.
Computerized
Data Acquisition
System
Exhaust Sample Measurements
— Mnc OO* by NOR, fpn
- NOs bf OwAimhssoinM, ppm
Figure 2: HDDV Facility Schematic
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3: HDDV Sampling Trailer Layout
(QA) checks in addition to the individual CEM
calibration and QA tests. A heated Tefion-iined
sampling line connects the sample port to a
heated filter and pump mounted on the front of
the trailer. A short, tine connects to the
instrument rack, and the sample remains heated
to the total hydrocarbon and chemiluminescent
NOx analyzers, while a parallel sample is cooled
and dried using a PerrnaPure dryer for the non-
dispersive infrared (NDIR) analyzers.
The rack-mounted industrial computer
data acquisition system uses Labtech Notebook
and Lotus 1-2-3 to record calibration and
measurement data. Some time alignment of the
from the individual analyzers is done
manually due to differing response times of the
instruments. The computer was recently
upgraded to a Pentium chip to handle the large
quantities of data generated by the test facility.
A second trailer is used as a support
facility. It contains a smaii office/laboratory area
and an for storing the weights not being
used in the test facility. The two trailers are
parked back to back In the staging area, and an
electric pallet jack is used to move the weights
between the two trailers. Permanent staging
have been set up near the remote test sites
with electric power to operate the facilities.
The first tractor being tested is a 1989
Ford L9000 Cab-over with a 315 HP Cummins
NTC engine. Modal testing has been completed.
The results for the NOx emissions for each
constant speed, load, and grade condition are
presented in figure 4. Little effect is noticed
except for the low speed runs where significantly
elevated levels are found. The grams/brake
horsepower-hour {g/BHP-hr) data are plotted in
figure 5 as a function of the estimated engine
m, Hwwswwi m, i^wns 3® 1$, **w*s s«, {^WM
SS^H^KP** «,Lo-W%* M «,*«»^ IS.isM^W
M tft, HM%Hi* 1ft .js-^I^M
C«i®»M Sp«»d C««*m®«*, mph C«anM»iS Sp®®d Coml»m* mph
Figure 4; Average Nitrogen Oxides Emissions by Operating Mode
4
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— » — *
•M «V» — —-—•""
1WS 120G 1*W
Figure 5; Nitrogen Oxides Emissions Versus Engine Torque
torque required by the truck. The
certification level of 7.88 g/BHP-hr for this
engine is indicated on this figure with most of
the data below that level except for the low
torque operating conditions. Analysis of these
is continuing will be reported in a later
paper.
As part of a cooperative agreement with
the North Carolina Truck Driver Training Program
at Johnston Community College (JCC), we have
conducted acceleration studies to determine the
effect, if any, progressive shifting has on vehicle
emissions. Progressive shifting limits the
maximum engine speed (in revolutions per
minute, rpm) reached in each gear constant
before shifting to the next successive gear. The
normal procedure, acceleration to maximum
governed rpm in each gear, is compared to the
progressive method in figure 6, No definite trend
can be identified in this initial test sequence. The
small circle plotted on this graph represents the
total emissions from that vehicle at a constant
55 mph for the distance it took to accelerate it
to 55 mph. This suggests that limited access
bypasses reduce emissions when compared to a
bypass with stoplight traffic controls.
figures 7 and 8 present examples of the
data traces from actual runs. The acceleration
run in figure 7 shows that the CEIVls and engine
sensors readily follow the changes in engine
operating conditions as the vehicle goes through
the gears. A section of urban delivery route is
shown in figure 8. The bottom line displays the
total g-load which is the sum of the forward
acceleration vectors due to gravity and velocity
change. This line shows the spikes as the vehicle
accelerates in each gear, and the corresponding
Zero to 55 MPH Acceleration Emissions
Sm»t» E
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Figure ?: Fully Loaded Truck Acceleration
60
SB
id
!-• ..!/•
Pollution, National Academy Press,
Washington, DC, 1991.
2, Southern Oxidants Study 1995. The
State of The Southern Oxidants Study:
Policy-Relevant Findings in Ozone
Pollution Research, 1988-1994. Prepared
by the Southern Oxidants Study, North
Caroiina State University, Raleigh, NC.
April 1995,
3. White, R, A., Korst, H, H., "The
Determination of Vehicle Drag
Contributions from Coast-Down Tests/*
SAE 720099, Society of Automotive
Engineers, Warrendaie, PA, 1992.
Readers more familiar with the metric
system may use the following equivalents to
convert to those units:
5/9(°F-32} = 1°C
0.305 ft = 1 m
0,0283 ft3 = 1 m3
746 hp = 1 W
0,454 tb = 1 kg
1.609 mi = 1 km
F:gur* 8: Test Data from S«ction of Urban Delivery Routs
this program. The results presented are specific
to the engine/tractor combination that was
tested, and may not be typical of the fleet as a
whole. Nonetheless, the remaining units will
cover all major engine manufacturers as well as
represent the range of emission standards the
engines were designed to meet through the 1994
standard. This project is expected to continue for
2 more years.
REFERENCES
1. National Research Council, Rethinking the
Ozone Problem In Urban and Regional Air
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OF THE
LaJolla, California
July 24-27, 1995
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