Exhaust Emissions from In-Use Heavy Duty Vehicles Tested on a Transportable Transient Chassis Dynamometer

142

Total and speciated particulate matter (PM2.5 and PM10) emission factors from in-use vehicles were measured for a mixed light- (97.4% LD) and heavy-duty fleet (2.6% HD) in the Sepulveda Tunnel, Los Angeles, CA. Seventeen 1-h test runs were performed between July 23, 1996, and July 27, 1996. Emission factors were calculated from mass concentration measurements taken at the tunnel entrance and exit, the volume of airflow through the tunnel, and the number of vehicles passing through the 582 m long tunnel. For the mixed LD and HD fleet, PM2.5 emission factors in the Sepulveda Tunnel ranged from 0.016 (+/-0.007) to 0.115 (+/-0.019) g/vehicle-km traveled with an average of 0.052 (+/-0.027) g/vehicle.km. PM10 emission factors ranged from 0.030 (+/-0.009) to 0.131 (+/-0.024) g/vehicle. km with an average of 0.069 (+/-0.030) g/vehicle.km. The PM2.5 emission factor was approximately 74% of the PM10 factor. Speciated emission rates and chemical profiles for use in receptor modeling were also developed. PM2.5 was dominated by organic carbon (OC) (31.0 +/- 19.5%) and elemental carbon (EC) (48.5 +/- 20.5%) that together account for 79% (+/-24%) of the total emissions. Crustal elements (Fe, Mg, Al, Si, Ca, and Mn) contribute approximately 7.8%, and the ions Cl-, NO3-, NH3+, SO4(2-), and K+ together constitute another 9.8%. In the PM10 size fraction the particulate emissions were also dominated by OC (31 +/- 12%) and EC (35 +/- 13%). The third most prominent species was Fe (18.5 +/- 9.0%), which is greater than would be expected from purely geological sources. Other geological components (Mg, Al, Si, K, Ca, and Mn) accounted for an additional 12.6%. PM10 emission factors showed some dependence on vehicle speed, whereas PM2.5 did not. For test runs in which the average vehicle speed was 42.6 km/h a 1.7 times increase in PM10 emission factor was observed compared to those runs with an average vehicle speed of 72.6 km/h. Speciated emissions were similar. However, there is significantly greater mass attributable to geological material in the PM10, indicative of an increased contribution from resuspended road dust. The PM2.5 shows relatively good correlation with NOx emissions, which indicates that even at the low percent of HD vehicles, which emit significantly more NOx than LD vehicles, they may also have a significant impact on the PM2.5 levels.

“…VOL. 35 2. Emission factors for runs 2 and 6 were invalid due to a sampler malfunction for run 2 and a higher inlet than outlet concentration for run 6.…”

Section: Resultsmentioning

confidence: 99%

On-Road Particulate Matter (PM_2.5 and PM₁₀) Emissions in the Sepulveda Tunnel, Los Angeles, California

Gillies

Gertler

Sagebiel

et al. 2001

142

“…Emissions studies of the in-use fleet have been conducted in a limited manner, primarily due to the expense and difficulty of recruiting and testing large numbers of heavyduty diesel vehicles. Previous studies found that in-use emissions from diesel vehicles, particularly CO and PM, were widely variable for different vehicles under identical test cycles (2,(4)(5)(6)(7)(8). Choice of test cycle can result in CO and particulate emissions changes of from 50 to more than 100% and lesser percentage changes in other pollutants (6,7).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, there is wide variability in the in-use fleet as 291 different heavy-duty diesel engines were certified for on-road use by the EPA in 1996 alone (9). Published studies (2)(3)(4)(5)(6)(7)(8)(10)(11)(12)(13) do not adequately reflect this variability nor do they include late model engines and vehicles. The large change in emissions regulations since 1985 (1) and normal turnover of the fleet make studies of newer vehicles important for evaluating the impact of regulations and for air quality planning purposes.…”

Section: Introductionmentioning

confidence: 99%

Chassis Dynamometer Study of Emissions from 21 In-Use Heavy-Duty Diesel Vehicles

Yanowitz

Graboski

Ryan

et al. 1998

Regulated emissions from 21 in-use heavy-duty diesel vehicles were measured on a heavy-duty chassis dynamometer via three driving cycles using a low-sulfur diesel fuel. Emissions of particulate matter (PM), nitrogen oxides (NO x ), carbon monoxide (CO), total hydrocarbon (THC), and PM sulfate fraction were measured. For hot start tests, emissions ranged from 0.30 to 7.43 g/mi (mean 1.96) for PM; 4.15−54.0 g/mi (mean 23.3) for NO x ; 2.09−86.2 g/mi (mean 19.5) for CO; and 0.25−8.25 g/mi (mean 1.70) for THC. When emissions are converted to a g/gal basis, the effect of driving cycle is eliminated for NO x and largely eliminated for PM. Sulfate comprised less than 1% of the emitted PM for all vehicles and test cycles. A strong correlation is observed between emissions of CO and PM. Cold starting at 77 °F produced an 11% increase in PM emissions. Multivariate regression analyses indicate that in-use PM emissions have decreased at a slower rate than anticipated based on the stricter engine certification test standards put into effect since 1985. NO x emissions do not decrease with model year for the vehicles tested here. Smoke opacity measurements are not well correlated with mass emissions of regulated pollutants.

“…Additionally, there is wide variability in the inuse fleet as 291 different heavy-duty diesel engines were certified for on-road use by the EPA in 1996 alone (16). Published studies (11)(12)(13)(14)(15)(17)(18)(19)(20)(21) do not adequately reflect this variability nor do they include late model engines and vehicles. The large change in emissions regulations since 1985 (1) and normal turnover of the fleet make studies of newer vehicles important for evaluating the impact of regulations and for air quality planning purposes.…”

mentioning

confidence: 99%

In-Use Emissions from Heavy-Duty Diesel Vehicles

Yanowitz

McCormick

Graboski

2000

209

197

This is a three part thesis regarding the regulated emissions from in-use heavy duty diesel vehicles. The first part of the thesis involves the collection and analysis of emissions from 21 vehicles. Emissions of particulate matter (PM), nitrogen oxides (NO x ), carbon monoxide (CO), total hydrocarbon (THC) and PM sulfate fraction were measured as well as smoke opacity. The vehicles were tested on three different driving cycles. This study found that when emissions were converted to a g/gallon basis, the effect of driving cycle was eliminated for NO x and reduced for PM. Sulfate comprised less than 1% of the emitted PM. Smoke opacity was not well correlated with mass emissions of any of the regulated pollutants. Multivariate regression analysis indicated that in-use NO x emissions did not decrease for this fleet during the years 1986 to 1995 while engine certification standards dropped sharply during that time. A review of all inuse emissions data in the scientific literature supported this result. The review also showed that PM emissions were widely variable among vehicles certified under identical standards. The variability was attributed to environmental factors, inertial weight, test cycle, driver variability and vehicle condition, but the relative importance of these factors could not be determined based on previously collected data. The wide variability in PM emissions within model years and the uniformity of NOx results despite the change in engine standards showed that engine certification was not an accurate tool to predict and iv control emissions from vehicles. To better understand the relationship between engine and chassis test results, a computer model was developed that estimates engine speed and load from vehicle speed. Using this model it was possible to detect the use of electronic controls which operate the engine in a different mode during engine testing and other more typical types of operation. The model also showed that the engine certification test generated consistently less PM than the vehicle tests when the model was used to put the engine and chassis emissions on a consistent basis. A good correlation was found between rate of HP increase integrated over the test cycle and PM emissions for both the chassis and engine tests. The engine test procedure includes engine behaviors that cannot be duplicated in in-use operation, and appears to favor lower rates of acceleration than typical chassis operation. The model also showed how small changes in vehicle speeds (+/-2 mph) due to driver variability can lead to a doubling of load on the engine.v