Real-world gaseous and particulate emissions from Euro IV to VI medium duty diesel trucks.

This study offers emission factors for earlier and late technology medium duty diesel particulate filter (DPF) -equipped trucks, operating on real-world conditions. The analysis includes levels of nitrous oxide (N2O) emissions as well as the impacts of DPF regenerations on emission levels. The real-driving gaseous and particulate emissions, as well as fuel consumption of 14 Euro IV, Euro V, and Euro VI medium duty diesel trucks were analysed and the efficiency of different emission control technologies were assessed. Measurements were conducted using portable emission measurement systems (PEMS) over a wide range of driving and operating conditions. Distance-based integration of emission rates over 500 m sections was considered for statistical analysis, providing a large dataset of emission factors to be used for network link-based traffic and emissions modelling. In terms of emissions performance, nitrogen oxides (NOx) levels were in general above the corresponding Euro standard limits, while carbon monoxide (CO), total hydrocarbons (THC) and particulate matter (PM) levels were within limits. Selective catalytic reduction (SCR) -equipped Euro V vehicles were seen to emit more than their non-SCR-equipped counterparts. NOx and fuel consumption were positively correlated with road gradient over the -6% to 6% gradient range. The emission levels of ammonia (NH3) were measured significantly lower than the respective Euro VI provisions for heavy duty engines, while the N2O levels were found to contribute approximately 1% to the respective total greenhouse gases levels. DPF regeneration events in real world seem to have a measurable impact mostly on THC and PM emissions, increasing baseline levels by 8.1% and 29%, respectively, for Euro VI vehicles.

Evaluation of Real-World Gaseous Emissions Performance of Selective Catalytic Reduction and Diesel Particulate Filter Bus Retrofits.

This study reports on the results of gaseous pollutants emission measurements of double-decker buses in an urban road network, using portable emission measurement systems (PEMS). Measured vehicles were tested by following in-service buses on regular routes. Six Euro II and Euro III buses were retrofitted with diesel particulate filters (DPF) and selective catalytic reduction (SCR) or a combined SCR+DPF (SCRT) device. Substantial and statistically significant technology impacts were observed for several pollutants. Optimized SCR and SCRT retrofit technology reduced real-world NO x emissions by approximately 70%, on average. Retrofit DPF slightly reduced NO x emissions but increased direct NO2 emissions by more than a factor of 8, on average. SCRT led to about 70% lower NO2 levels than DPF alone, but for some vehicles higher NO2 levels were observed as compared with the "no retrofit" situation, warranting further investigation. None of the SCR systems were found to lead to a substantial increase in NH3 emissions after operation optimization. High NH3 and N2O emissions were occasionally observed while experience with the system calibration was being accumulated. Observed average N2O emission levels for "DPF+SCR" technology were relatively high at 182 mg/kg fuel, corresponding to 1.5% of total greenhouse gas emissions. The study shows that SCR retrofit programs can be effective for NO x reduction of transit buses but that proper calibration and regular emission monitoring are required.