In the near future, exhaust emissions legislation will become much stricter while at the same time traffic-related CO2 emissions have to be reduced. This requires significantly different development methodologies. The main reasons are mandatory expansions of the technology solutions, considerably different boundary conditions and stricter certification procedures, with the key element of ensuring compliance with emissions limits even outside standardized testing cycles. In addition the pressure on cost is constantly increasing. The FEV Group developed solutions for the two main concerns of this issue: Identification of target oriented emission reduction concepts including the entire vehicle, as well as establishing highly efficient development methods. In representation of a wide range of applications two vehicles were included. A B-segment vehicle with a 1.5-liter diesel engine, which typically faces extreme constrains on cost and packaging space to integrate complex emission control systems and an ambitious SUV application with a 2.0-liter bi-turbo engine which is also exposed to significant full-load operation in regards to the RDE list of requirements.
>> DIESEL ENGINES WILL CONTINUE TO BE A KEY COMPONENT IN INTEGRATED CO2 REDUCTION STRATEGIES
The homologation process will transition from the traditional NEDC test cycle into the new WLTP cycle. RDE regulations will be implemented, as an additional element for evaluating emissions behavior in real-world driving conditions. New procedures and approaches to accurately represent the extensive requirements are needed. Challenging circumstance is the deliberately exclusion of standardized RDE testing conditions by the authorities. A result is partially unknown, stochastic operating conditions that make a robust and adaptable system approach mandatory to comply with the future emissions standards. Not only capable, generously sized and optimized sub-systems as part of a holistic emission concept are required, but also adjustable, highly effective systems for all potential operating conditions in real-world driving situations. The engine control system must include adaptive and intelligent function algorithms.
Combining Global Expertise
The implementation of a comprehensive testing catalog with FEV’s standardized procedures is based on extensive data collection and data evaluation. FEV compiled all RDE results and driving cycles available throughout the group, analyzed data and created a modular, multi-tiered approach.
SUVs are gaining in popularity, as demonstrated by recent market forecasts as issued by the Institute for Advanced Studies (IHS). Diesel engines take a considerable market share in this segment. Hence, FEV experts decided to apply the new development method to this segment.
Very favorable engine-out emissions across the entire spectrum of RDE cycles can be achieved using consistently optimized combustion systems with a high EGR acceptance across the entire engine map. This is possible by the application of a capable sized EGR system. In addition, an effective DeNOx aftertreatment system consisting of a lean NOx trap (LNT) installed close to the engine and a supplemental underfloor SCR unit enables lowest possible NOx emissions. In more than 91% of all cycles during the test case, the results were far below the conformity factor (CF) of 1.5, while all evaluated RDE cycles concluded with CF of 2.1 (valid until 2020). To achieve 100% coverage of the CF of 1.5, further optimization steps are need to optimize this challenging application [~1.4 tons/liter or 16.4 kg/kW].
This very positive emissions behavior was achieved in a relatively short development time. Consequent integration of continuous evolving simulation results into the standardized, DoE-baes calibration process was crucial for the application work as well as the involvement of virtual development methods. In summary, advanced passenger car diesel engines are capable of reliably complying with the strictest emissions standards expected in the future, including during real-world operation. Therefore, they will be an important part in a holistic CO2 reduction strategy.