Abstract
Keywords - Piezo-injector, injection rate, CFD, KIVA-3V, emission modeling
Abstract - In direct injection diesel engines the fuel atomisation process strongly affects combustion and exhaust emissions. The demands on modern injection systems concerning a minimisation of emissions and fuel consumption are significant driving forces for the optimisation of the fuel injection process and the mixture formation in the cylinder. Besides experimental parametric studies CFD-Simulations are an excellent tool to understand physical processes more thoroughly. In addition to a further increase of the maximum injection pressure future injection systems will have to offer a high flexibility of rate shaping as well as high re-producibility.
The Institute of Technical Combustion (ITV) at the University of Hannover has developed a new piezoelectrically controlled common rail injection system for research purposes. Its fun-damental difference to conventional common rail injectors is that the piezo-element is directly connected with the needle enabling a highly dynamic and extremely accurate movement and positioning of the needle during the injection. The system is used to investigate the requirements and the potential of different injection rates and their influence on the fuel atomisation process. Therefore optical investigations were accomplished on a rapid compression machine to get precise information about the spray. These investigations were followed by experimental examinations on a single cylinder research engine, which allows a verification by an emis-sion and cylinder pressure analysis. In order to support the experiments simulations with the
3D-CFD-Code KIVA-3V were used to estimate the influences of different injection nozzles and strategies on soot and nitrogen oxide emissions.
The objective of this paper is to give fundamental methods to minimize toxic exhaust components like nitrogen oxides and soot. Thus the influence of different injection nozzles and injection rates on the emissions were investigated with a piezoelectrically controlled research injector. Additionally the CFD-Simulation could emphasize the experimental results and give detailed information about the physical sub-processes. It is shown that there are very reasonable agreements between the 3D-Simulation and the experimental examinations.