Diesel and CNG Heavy-duty Transit Bus Emissions over Multiple Driving Schedules: Regulated Pollutants and Project Overview

Ayala, Alberto; Kado, Norman Y.; Okamoto, Robert A.; Holmén, Britt A.; Kuzmicky, Paul A.; Kobayashi, Reiko; Stiglitz, Keith E.

doi:10.4271/2002-01-1722

Cited by 71 publications

(70 citation statements)

References 5 publications

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“…7), which is in accordance with Ekström et al (2005). Possible reasons for this variability may be vehicle maintenance and variations in the CNG composition (Shorter et al, 2005;Ayala et al, 2002). The EF for NO x ranged from 4 to 21 g km −1 depending on Euro class, which is in good agreement with reported values for HDVs and buses in the literature (Table 5).…”

Section: Comparison Of Ef Part and Ef Gas (No X Hc And Co)supporting

confidence: 83%

“…The average EF CO for the diesel buses with DPF tested in this study, when assigning values below 6 (1 times the std of the noise) to 6 g (kg fuel) −1 , were 11 g (kg fuel) −1 (10 buses in total). For the buses without DPF the average EF CO was 14 g (kg fuel) −1 (18 buses in total); hence DPF is not only reducing particles but CO as well, as reported in Ayala et al (2002) and Lanni et al (2001). For the tested buses, DPF had no statistical significant effect on the amount of NO x emitted, which also is in agreement with results reported by Ayala et al (2002).…”

Section: Comparison Of Ef Part and Ef Gas (No X Hc And Co)supporting

confidence: 65%

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Particle and gaseous emissions from individual diesel and CNG buses

et al. 2013

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In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO₂ as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO₂ with a non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NO_x, were estimated from NO by using default NO₂/NO_x ratios from the road vehicle emission model HBEFA3.1. The buses studied were diesel-fuelled Euro III–V and CNG-fuelled Enhanced Environmentally Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average a higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EF_PN) were EF_{PN, DPF} = 4.4 ± 3.5 × 10¹⁴, EF_{PN, no DPF} = 2.1 ± 1.0 × 10¹⁵ and EF_{PN, CNG} = 7.8 ± 5.7 ×10¹⁵ kg fuel⁻¹. In the accelerating mode, size-resolved emission factors (EFs) showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode, bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NO_x expressed as NO₂ equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)⁻¹ and for the CNG buses 41 ± 26 g (kg fuel)⁻¹. An anti-relationship between EF_{NO_x} and EF_PM was observed especially for buses with no DPF, and there was a positive relationship between EF_PM and EF_CO

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Section: Comparison Of Ef Part and Ef Gas (No X Hc And Co)supporting

confidence: 83%

Section: Comparison Of Ef Part and Ef Gas (No X Hc And Co)supporting

confidence: 65%

Particle and gaseous emissions from individual diesel and CNG buses

et al. 2013

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“…Vehicle emission testing took place at the CARB Heavy-Duty Emissions Testing Laboratory (HDETL) in Los Angeles, CA (Ayala et al, 2002;Herner et al, 2009). The laboratory was equipped with a heavy-duty chassis dynamometer (SchenckPegasus) driven by a direct-current 675-hp motor that can absorb up to 660 hp.…”

Section: Vehicles Information and Sampling Methodsmentioning

confidence: 99%

Emissions of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs from heavy-duty diesel vehicles with DPF and SCR

Herner

Robertson

et al. 2013

Journal of the Air & Waste Management Association

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In total, 24 polycyclic aromatic hydrocarbons (PAHs) in both gas and particle phases and 35 nitro-PAHs in particle phase were analyzed in the exhaust from heavy-duty diesel vehicles equipped with after-treatment for particulate matter (PM) and NO X control. The test vehicles were carried out using a chassis dynamometer under highway cruise, transient Urban Dynamometer Driving Schedule (UDDS), and idle operation. The after-treatment efficiently abated more than 90% of the total PAHs. Indeed, the particlebound PAHs were reduced by >99%, and the gaseous PAHs were removed at various extents depending on the type of after-treatment and the test cycles. The PAHs in gas phase dominated the total PAH (gas þ particle phases) emissions for all the test vehicles and for all cycles; that is, 99% of the two-ring and 98% of the three-ring and 97% of the four-ring and 95% of the carcinogenic PAHs were in the gas-phase after a diesel particle filter (DPF) and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must include this volatile fraction and cannot be based on the particle fraction only. The selective catalytic reduction (SCR) did not appear to promote nitration of the PAHs in general, although there might be some selective nitration of phenanthrene. Importantly the after-treatmtent reduced the equivalent B[a]P (B[a]Peq) emissions by >95%, suggesting a substantial health benefit.Implications: This study demonstrated that after-treatments, including diesel particulate filters (DPF), diesel oxidation catalysts (DOC), and selective catalytic reduction (SCR), significantly reduce the emissions of PAHs from heavy-duty diesel engines. The gasphase PAHs dominate the total PAH (gas þ particle phases) emissions from heavy-duty diesel vehicles retrofitted with various DPFs and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must also include this volatile fraction and cannot be based on the particle fraction only.

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“…The sampling train included heavy-duty dynamometer chassis, constant volume sampling (CVS) dilution tunnel, and aerosol samplers. Details about this facility and its operation are described elsewhere (Ayala et al, 2002). With the exception of the "baseline" vehicle (not equipped with any catalytic converter) the other 2 tested heavy duty diesel trucks, a Vanadium-based SCRT vehicle and a Zeolitebased SCRT truck, were equipped with advanced emission SCRT is an integrated system of selective catalytic reduction (SCR) and continuously regenerating trap (CRT) designed to reduce both PM and NOx emissions.…”

Section: Motor-vehicle Emissions Sampling -The Carb Dynamometer Facilitymentioning

confidence: 99%

Real-time characterization of particle-bound polycyclic aromatic hydrocarbons in ambient aerosols and from motor-vehicle exhaust

Polidori

Biswas

et al. 2008

Atmos. Chem. Phys.

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Abstract.A photo-electric aerosol sensor, a diffusion charger, an Aethalometer, and a continuous particle counter were used along with other real-time instruments to characterize the particle-bound polycyclic aromatic hydrocarbon (p-PAH) content, and the physical/chemical characteristics of aerosols collected a) in Wilmington (CA) near the Los Angeles port and close to 2 major freeways, and b) at a dynamometer testing facility in downtown Los Angeles (CA), where 3 diesel trucks were tested. In Wilmington, the p-PAH, surface area, particle number, and "black" carbon concentrations were 4-8 times higher at 09:00-11:00 a.m. than between 17:00 and 18:00 p.m., suggesting that during rush hour traffic people living in that area are exposed to a higher number of diesel combustion particles enriched in p-PAH coatings. Dynamometer tests revealed that the p-PAH emissions from the "baseline" truck (no catalytic converter) were up to 200 times higher than those from the 2 vehicles equipped with advanced emission control technologies, and increased when the truck was accelerating. In Wilmington, integrated filter samples were collected and analyzed to determine the concentrations of the most abundant p-PAHs. A correlation between the total p-PAH concentration (µg/m 3 ) and the measured photo-electric aerosol sensor signal (fA) was also established. Estimated ambient p-PAH concentrations (Average=0.64 ng/m 3 ; Standard deviation=0.46 ng/m 3 ) were in good agreement with those reported in previous studies conducted in Los Angeles during a similar time period. Finally, we calculated the approximate theoretical lifetime (70 years per 24-h/day) lung-cancer risk in the Wilmington area due to inhalation of multi-component p-PAHs and "black" carbon. Our results indicate that the lung-cancer risk is highest during rush hour traffic and lowest in the afternoon, and that the Correspondence to: C. Sioutas (sioutas@usc.edu) genotoxic risk of the considered p-PAHs does not seem to contribute to a significant part of the total lung-cancer risk attributable to "black" carbon.

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Diesel and CNG Heavy-duty Transit Bus Emissions over Multiple Driving Schedules: Regulated Pollutants and Project Overview

Cited by 71 publications

References 5 publications

Particle and gaseous emissions from individual diesel and CNG buses

Particle and gaseous emissions from individual diesel and CNG buses

Emissions of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs from heavy-duty diesel vehicles with DPF and SCR

Real-time characterization of particle-bound polycyclic aromatic hydrocarbons in ambient aerosols and from motor-vehicle exhaust

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