Modern Euro 6d diesel engines with the corresponding exhaust aftertreatment technology have long been capable of significantly undercutting the existing emissions thresholds. So, air quality targets are met, even in inner-city traffic. However, the public image of the diesel engine is a tarnished one – the threat of driving bans for older vehicles and an often highly emotional debate continue to harm the perception of this highly efficient drive type. A recent study by FEV Europe GmbH in Aachen once again proves that this is unjustified. The company develops innovative drive concepts for the global automotive and engine industry. Within the scope of its “White Eco Diesel” project, the engineers in Aachen improved the arrangement and configuration of existing components, resulting in reduced nitrogen oxide emissions under urban driving conditions in particular, as well as lowering fuel consumption – with no negative impact on driving performance and characteristics. Numerous renowned suppliers took part in the study as partners. BASF provided state-of-the-art catalyst technology for the test system.
FEV had already presented initial promising results at the International Vienna Motor Symposium in May 2019. Further detailed results were then revealed at the most recent Aachen Colloquium Automobile and Engine Technology, which was held from October 7-9, 2019, and where the visitors from the trade could also experience the performance of the drive concept for themselves with the new concept vehicle. The basic idea behind it is simple. The exhaust aftertreatment system is positioned upstream of the turbocharger, not downstream. The diesel oxidation catalyst (DOC), a SCR and SCRoF (selective catalytic reduction on filter) for reducing cold start emissions, a large underfloor SCR and the ammonia oxidation catalyst (AMOX) from BASF Catalysts were used. The catalysts upstream of the turbocharger benefit from the increased proximity to the engine, as the exhaust gases fed into the turbocharger are much hotter there. Accordingly, the faster the higher exhaust gas temperature is reached, the sooner the catalytic reactions that comprehensively eliminate harmful substances can begin. The outcome was clear: both nitrogen oxide (NOx) and hydrocarbon emissions are reduced considerably. Furthermore, because the exhaust gases do not have to be heated as much due to the positioning of the catalysts, the energy consumption also falls. As a result, there is significant potential to save fuel and reduce CO2 compared to the conventional catalyst arrangement.
This technological approach is not fundamentally new. In the past this arrangement was not pursued further because it also poses a special challenge. If the exhaust aftertreatment system is upstream of the turbocharger, the turbocharger’s performance and dynamics decline. If the hotter exhaust gas reaches the catalysts first, it therefore arrives at the turbo both cooler and later with a noticeable impact on driving dynamics. FEV’s solution was to use an electrical 48 V turbocharger that is activated when the thermal energy of the engine exhaust gas is not sufficient. As a result, the driving behavior no longer differs from that of other vehicles that comply with Euro 6d, while the emission values of vehicles using the White Eco Diesel technology fall even further below the respective limits.
“Since the advent of Euro 6d and the corresponding emission measurements taken in real traffic conditions required for certification, diesel vehicles are cleaner than ever. The results of the FEV study underline this once again and clearly demonstrate that the diesel engine still has great potential, also through the intelligent combination of existing components and the use of hybrid technology,” commented Dr. Uwe Zink, Technical Manager Regulatory Affairs at BASF Catalysts Germany in Hanover. “It is possible to have clean diesel vehicles without impacting the air quality in towns and cities. This is also an important signal, as diesel engines are up to 30 percent more economical than their gasoline counterparts. The latest diesel vehicles can therefore play an important part in achieving the climate and air quality goals. So, diesel vehicles and clean air are not mutually exclusive – on the contrary.”
In addition, Zink praised the FEV study as an excellent example of how industry partners can cooperate successfully and realize such a project. Under the project leadership of FEV, further renowned industry partners contributed their components and expertise alongside BASF. “We think it’s great when important players succeed in working together as partners in order to turn individual innovations into an excellent collaborative achievement.”