On-road and laboratory emissions of NO, NO_2, NH_3, N_2O and CH_4 from late-model EU light utility vehicles: Comparison of diesel and CNG

摘要

AbstractExhaust 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, NO2and 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 NOX, CO and CO2during dynamometer tests. On diesel engines, mean NOXemissions 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 NOXand 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 NOXemissions 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 NOX(12–186mg/km) and NH3(10–24mg/km), while mean emissions of methane were 18–45mg/km, under 1g/km CO2equivalent, 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.Graphical abstractDisplay OmittedHighlights•On-board FTIR used to measure real-world emissions from diesel and CNG Euro 6 vans•Diesel vans produced hundreds of mg/km NOx, little NH3, tens of mg/km N2O.•CNG vans produced tens of mg/km NOxand NH3, little N2O, methane, aldehydes.•FTIR useful for assessment of classic and unregulated gases incl. NO2, NH3, N2O, CH4•NOx, NO2, NH3, greenhouse gas emissions assessment needed also for small vans, trucks