3 research outputs found
Time Resolved Measurements of Speciated Tailpipe Emissions from Motor Vehicles: Trends with Emission Control Technology, Cold Start Effects, and Speciation
Experiments
were conducted at the California Air Resources Board
Haagen-Smit Laboratory to understand changes in vehicle emissions
in response to stricter emissions standards over the past 25 years.
Measurements included a wide range of volatile organic compounds (VOCs)
for a wide range of spark ignition gasoline vehicles meeting varying
levels of emissions standards, including all certifications from Tier
0 up to Partial Zero Emission Vehicle. Standard gas chromatography
(GC) and high performance liquid chromatography (HLPC) analyses were
employed for drive-cycle phase emissions. A proton-transfer-reaction
mass spectrometer measured time-resolved emissions for a wide range
of VOCs. Cold-start emissions occur almost entirely in the first 30–60
s for newer vehicles. Cold-start emissions have compositions that
are not significantly different across all vehicles tested and are
markedly different from neat fuel. Hot-stabilized emissions have varying
importance depending on species and may require a driving distance
of 200 miles to equal the emissions from a single cold start. Average
commute distances in the U.S. suggest the majority of in-use vehicles
have emissions dominated by cold starts. The distribution of vehicle
ages in the U.S. suggests that within several years only a few percent
of vehicles will have significant driving emissions compared to cold-start
emissions
Measuring Particulate Emissions of Light Duty Passenger Vehicles Using Integrated Particle Size Distribution (IPSD)
The California Air
Resources Board (ARB) adopted the low emission
vehicle (LEV) III particulate matter (PM) standards in January 2012,
which require, among other limits, vehicles to meet 1 mg/mi over the
federal test procedure (FTP). One possible alternative measurement
approach evaluated to support the implementation of the LEV III standards
is integrated particle size distribution (IPSD), which reports real-time
PM mass using size distribution and effective density. The IPSD method
was evaluated using TSI’s engine exhaust particle sizer (EEPS,
5.6–560 nm) and gravimetric filter data from more than 250
tests and 34 vehicles at ARB’s Haagen-Smit Laboratory (HSL).
IPSD mass was persistently lower than gravimetric mass by 56–75%
over the FTP tests and by 81–84% over the supplemental FTP
(US06) tests. Strong covariance between the methods suggests test-to-test
variability originates from actual vehicle emission differences rather
than measurement accuracy, where IPSD offered no statistical improvement
over gravimetric measurement variability
Emissions During and Real-world Frequency of Heavy-duty Diesel Particulate Filter Regeneration
Recent
tightening of particulate matter (PM) emission standards
for heavy-duty engines has spurred the widespread adoption of diesel
particulate filters (DPFs), which need to be regenerated periodically
to remove trapped PM. The total impact of DPFs therefore depends not
only on their filtering efficiency during normal operation, but also
on the emissions during and the frequency of regeneration events.
We performed active (parked and driving) and passive regenerations
on two heavy-duty diesel vehicles (HDDVs), and report the chemical
composition of emissions during these events, as well as the efficiency
with which trapped PM is converted to gas-phase products. We also
collected activity data from 85 HDDVs to determine how often regeneration
occurs during real-world operation. PM emitted during regeneration
ranged from 0.2 to 16.3 g, and the average time and distance between
real-world active regenerations was 28.0 h and 599 miles. These results
indicate that regeneration of real-world DPFs does not substantially
offset the reduction of PM by DPFs during normal operation. The broad
ranges of regeneration frequency per truck (3–100 h and 23–4078
miles) underscore the challenges in designing engines and associated
aftertreatments that reduce emissions for all real-world duty cycles