On-road and laboratory emissions of NO, NO2, NH3, N2O and CH4 from late-model EU light utility vehicles: Comparison of diesel and CNG

Michal Vojtíšek-Lom; Vít Beránek; Vojtěch Klír; Petr Jindra; Martin Pechout; Tomáš Voříšek

doi:10.1016/j.scitotenv.2017.10.248

On-road and laboratory emissions of NO, NO₂, NH₃, N₂O and CH₄ from late-model EU light utility vehicles: Comparison of diesel and CNG

Sci Total Environ. 2018 Mar:616-617:774-784. doi: 10.1016/j.scitotenv.2017.10.248. Epub 2017 Nov 7.

Authors

Michal Vojtíšek-Lom¹, Vít Beránek², Vojtěch Klír², Petr Jindra³, Martin Pechout³, Tomáš Voříšek⁴

Affiliations

¹ Center for Sustainable Mobility, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 160 00 Praha 6, Czech Republic. Electronic address: michal.vojtisek@fs.cvut.cz.
² Center for Sustainable Mobility, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 160 00 Praha 6, Czech Republic.
³ Department of Vehicles and Ground Transport, Czech University of Life Sciences in Prague, Kamýcká 129, 165 21 Praha 6, Czech Republic.
⁴ SEVEn Energy Ltd., Americká 17, 120 00 Praha 2, Czech Republic.

PMID: 29126635
DOI: 10.1016/j.scitotenv.2017.10.248

Abstract

Exhaust emissions of eight Euro 6 light duty vehicles - two station wagons and six vans - half powered by diesel fuel and half by compressed natural gas (CNG) were examined using both chassis dynamometer and on-road testing. A portable on-board FTIR analyzer was used to measure concentrations of reactive nitrogen compounds - NO, NO₂ and ammonia, of CO, formaldehyde, acetaldehyde and greenhouse gases CO₂, methane and N₂O. Exhaust flow was inferred from engine control unit data. Total emissions per cycle were compared and found to be in good agreement with laboratory measurements of NO_X, CO and CO₂ during dynamometer tests. On diesel engines, mean NO_X emissions were 136-1070mg/km in the laboratory and 537-615mg/km on the road, in many cases nearly an order of magnitude higher compared to the numerical value of the Euro 6 limit. Mean N₂O emissions were 3-19mg/km and were equivalent to several g/km CO₂. The measurements suggest that NO_X and N₂O emissions from late-model European light utility vehicles with diesel engines are non-negligible and should be continuously assessed and scrutinized. High variances in NO_X emissions among the tested diesel vehicles suggest that large number of vehicles should be tested to offer at least some insights about distribution of fleet emissions among vehicles. CNG engines exhibited relatively low emissions of NO_X (12-186mg/km) and NH₃ (10-24mg/km), while mean emissions of methane were 18-45mg/km, under 1g/km CO₂ equivalent, and N₂O, CO, formaldehyde and acetaldehyde were negligible. The combination of a relatively clean-burning fuel, modern engine technology and a three-way catalyst has resulted in relatively low emissions under the wide variety of operating conditions encountered during the tests. The on-board FTIR has proven to be a useful instrument capable of covering, with the exception of total hydrocarbons, essentially all gaseous pollutants of interest.

Keywords: CNG; Euro 6; FTIR; Nitrous oxide; On-road emissions; Reactive nitrogen.