Abstract

Diesel NOx emissions have been at the forefront of research and regulation scrutiny as a result of failures of late vehicle technologies to deliver on-road emissions reductions. The current study aims at identifying the actual emissions levels of late light duty vehicle technologies, including Euro 5 and Euro 6 ones. Mean NOx emission factor levels used in the most popular EU vehicle emission models (COPERT, HBEFA and VERSIT+) are compared with latest emission information collected in the laboratory over real-world driving cycles and on the road using portable emissions measurement systems (PEMS). The comparison shows that Euro 5 passenger car (PC) emission factors well reflect on road levels and that recently revealed emissions control failures do not call for any significant corrections. However Euro 5 light commercial vehicles (LCVs) and Euro 6 PCs in the 2014–2016 period exhibit on road emission levels twice as high as used in current models. Moreover, measured levels vary a lot for Euro 6 vehicles. Scenarios for future evolution of Euro 6 emission factors, reflecting different degree of effectiveness of emissions control regulations, show that total NOx emissions from diesel Euro 6 PC and LCV may correspond from 49% up to 83% of total road transport emissions in 2050. Unless upcoming and long term regulations make sure that light duty diesel NOx emissions are effectively addressed, this will have significant implications in meeting future air quality and national emissions ceilings targets. © 2016 Elsevier Ltd

Abstract

WOS: 000318575900001 Due to factors affecting flight operation and air traffic management, such as air traffic separation, avoidance of traffic from congested areas, or facilitating separation with crossing traffic, as well as environmental constraints, aircraft cannot always use optimum descent profiles and perform stair step descent or low level flight. This leads to vertical flight inefficiencies and thereby an increase in fuel consumption and NOx emissions. In order to address the negative impact of vertical flight inefficiencies, particularly in the descent phase, descending at constant flight path angles has been identified as an efficient approach procedure by aviation organizations and researchers. This procedure is defined as continuous descent approach. In this study, an evaluation of continuous descent approach and various flight path angles, in relation to conventional approaches, is investigated and the comparative results are given in terms of NOx emissions, fuel consumption, and descent duration. As a result, a strong inverse proportion between flight path angle and fuel consumption is found. As expected, an analogous strong inverse relationship is also found for flight path angle and NOx emissions, not only from reduced fuel usage, but also from the changed exhaust gas temperature due to lower power settings thanks to the continuous descent approach. It can also be seen that the descent duration could be less for steeper flight path angles.