Directly actuated piezo injector for advanced injection strategies towards cleaner diesel engines

Low fuel consumption is one of the greatest merits of the Diesel engine, emission of nitrous oxides, NOx, and particulate matter, PM, are its most prominent disadvantages. For modern passenger car diesel engines, to achieve low fuel consumption targets, i.e. CO2 emissions, and to simultaneously fulfil the ambitious EU6 emissions legislation, a combination of intelligent injection strategies and high EGR rates with appropriate boost pressures is required. Generally, NOx emissions can efficiently be decreased via exhaust gas recirculation, EGR. An unwanted consequence of this is an increase in smoke, HC and CO emissions. This can be alleviated by a suitable application of injection strategies. Injections strategies are also employed to curb excessive emissions of unburnt hydro-carbons, HC, and carbon monoxide, CO, particularly in conditions of cold start. These strategies may also be used to facilitate fast light-off of the oxidation catalyst. In the current work the novel directly actuated piezo injector of Continental Automotive GmbH was used to evaluate the emissions potential not only of multiple injection patterns, but also of advanced rate shaping strategies. The application of this wealth of technology puts further cost onto the already expensive Diesel engine. Nevertheless, there is a need to explore the benefits and the limits of such technology, since the fuel consumption and CO2 emission target of 120g/km across the European passenger car fleet can only be achieved with a sufficiently high share of Diesel vehicles, also in the most dominant market segment of small and medium sized cars. Cost in this respect needs to be considered from an overall engine system point of view. Higher cost for measures to reduce engine out emissions may be well invested if exhaust gas aftertreatment can be avoided or at least be minimised.