DIESEL PASSENGER CAR WITH ULTRA-LOW NOX EMISSIONS IN REAL DRIVING CONDITIONS

In future, a further reduction of the nitrogen oxide emissions for passenger cars with diesel engines is to be expected. As part of a joint project, IAV and the Association for Emissions Control by Catalyst (AECC) have investigated the extent to which emissions from diesel vehicles can be further reduced in real driving operation through mild hybridisation and optimised exhaust after-treatment.

MOTIVATION

The European Union legislation on light-duty vehicle emissions has undergone major changes in the last years. The Worldwide harmonised Light-duty vehicles Test Procedure (WLTP) was developed and implemented to determine fuel consumption and CO2 emissions that are more representative of normal vehicle use. In parallel, real driving emissions (RDE) regulation has entered into force that regulates nitrogen oxides (NOx) and particle number (PN) emissions on the road.

The gap between diesel vehicle emissions in laboratory tests compared to those in use has been addressed and modern diesel technology demonstrates low emissions, while driving on the road [1-3]. 1 visualises the significant reduction in NOx emissions from pre-RDE (grey area) to RDE-compliant (blue dots) diesel vehicles, by plotting Portable Emissions Measurement System (PEMS) data from the RDE tests conducted at type approval [4, 5].

Each data point in â‘ represents a vehicle’s NOx emission over an RDE-compliant route comprising urban, rural and motorway driving conditions. 2 visualises how the NOx tailpipe emission level varies according to average vehicle speed/ loads. For pre-RDE vehicles, type approval was limited to the New European Driving Cycle (NEDC), a laboratory test characterised by a single average speed/load value, giving the NOx emission value in the middle of the graph in â‘¡. The robustness of tailpipe NOx emission control across this wider range of driving conditions encountered on public roads has been improved significantly over recent years through powertrains and emission control systems optimisation to meet RDE requirements, â‘¡ (blue arrows).