Advanced heterogeneous diesel combustion with ultra-low engine emissions and low fuel consumption levels

Abstract

Increasingly stringent emissions regulations, limited reserves of fossil fuels and CO2-related climate effects have led to the demand for new and diversified engine and vehicle technologies. Compression ignition combustion processes currently offer the highest thermal efficiencies and therefore low specific fuel consumption. Nevertheless, conventional diesel engines face challenges in decreasing NO x and particulate emissions if they are to meet ever more stringent emission regulations. An overview of advanced Diesel technologies and possible ways to address these challenges will be presented in this paper. A recently developed combustion process will be highlighted in detail to demonstrate the emission reduction potential of heterogeneous diesel combustion while maintaining a high thermal efficiency. This combustion process is based on the spatial separation of the different part injections performed during one cycle and offers major advantages in terms of oxygen use, increased exhaust gas recirculation tolerance and significantly lower levels of pollutant formation. This injection strategy is realized by integrating a second injector into the cylinder head of a single cylinder research engine. This second injector is used for the pilot injection and the centrally placed standard injector is used for the main injection. This configuration allows the pilot and main fuels to be injected into different areas of the cylinder. Additionally, the flexible configuration of the proposed injection system allows easy implementation of alternative combustion processes such as homogeneous or partially premixed combustion.