Growing road traffic in Europe results in detrimental effects on the environment and public health. In particular, carbon dioxide (CO2) and noxious emissions may not be sufficiently reduced in real driving, whilst some technologies may have led to increases in the emissions of nanoparticles that are undetected currently. The challenge was to develop a new generation of engine technologies that is significantly more fuel efficient than the best 2015 equivalent, in order to help mitigate the climate change effects of road transport, and to demonstrate pollutant emissions levels compliant with the Euro 6 real driving emissions (RDE) limits plus particle number emissions measured down to 10nm size.
Globally, the gasoline engine will remain the dominant passenger car prime mover this decade. These vehicles show about 10% higher CO2 emissions for those with gasoline engines compared to diesel. Given this basis and projections that gasoline engines (including those in hybrid powertrains) remain dominant in light duty vehicles throughout this decade, then improvements in gasoline engines have a greater potential to lower the passenger car vehicle parc CO2 emissions than improvements in diesel engines. Further, in Europe those passenger car vehicles with the higher annual mileages are often those with higher CO2 emissions. The challenge for the industry is, therefore, to develop highly efficient engines and to improve exhaust gas aftertreatment systems, in order to meet EU legislation in real driving conditions. Simultaneously, the European automotive industry has to improve competitiveness in order to maintain substantial market volumes of high-quality cars.
In PaREGEn, further development of gasoline engines used in mid to premium sized passenger cars has been made. With the electrification of powertrains in smaller vehicles, suitable for zero emissions in urban environments, addressing mid to premium sized cars has been especially important: the requirement for ultra-low emission, efficient and economic engines (whether hybridised or not) for cars regularly used for inter-urban and regional transport becomes more urgent, especially in light of the recent falling market share of diesel engine vehicles, as well as more effective to address the societal challenges of air quality, energy efficiency (decarbonization) and cost-effective mobility. Furthermore, it should be remembered that, should drop-in low carbon or net-zero carbon fuels become available in the coming decade, then it is the type of passenger car vehicles being developed in PaREGEn, that could contribute most to the additional defossilisation realisable.
Through the use of state of the art development techniques, such as optical single cylinder engines, a range of modelling and simulation tools from 0D to 3D (for understanding of in-cylinder particle formation process) and the application of novel engine componentry (next generation fuel or water injection and ignition equipment, boosting systems and exhaust gas aftertreatment technology), the optimal trade-offs between ultra-low emissions and efficiency have being identified. Of special attention throughout this process was the contribution of such technologies to the reduction and control of particle numbers, including those particles between 10 and 23 nm in size. One of the most valuable contributions from this project has been that the new modelling and simulation tools benefit engine design, development and control in general, long after the project is completed.
This learning has been used for the generation of two demonstration vehicles. The approaches to achieving the efficiency targets are different in each, using different combustion system, injection (fuel and water), ignition and dilutent technologies, different engine air handling systems and different aftertreatment packages. As such, the progress within the project has given insight into the best way forward to meet the requirements for these gasoline engines in all vehicle classes during this new decade.
