Abstract
Regulated emissions and CO2-values, good comfort and drivability, high reliability and affordable costs, this is the main frame for all future powertrain developments. In this frame, the diesel powertrain faces several challenges in order to fulfill the different future emission legislations while keeping the engine efficiency and in consequence the fuel consumption benefit.
One widely discussed approach for fuel consumption improvement within passenger car applications is to incorporate the downsizing effect. Certain publications have already discussed strategies for diesel engines with reduced capacity. The correlating impact on fuel consumption is therefore well-known. To maintain the high full-load performance of a diesel powertrain, an increase of the specific power has to be considered when facing future downsizing concepts. In this context, this publication deals with the further potential of increasing the specific power for HSDI diesel engines while meeting the required engine-out emissions for future legislation.
In order to increase the power density of a self-ignition engine, different approaches are possible. While benefiting from an improved turbo charger design an optimized boost strategy can be developed. Furthermore, the layout of the injection system can be optimized for high full load performance. In detail, this includes investigations of different nozzles specifications with increasing hydrodynamic flow rate for improved full load performance while maintaining acceptable part load emission behavior and fuel economy on superior level.
In addition to that, by means of cycle simulations, a trade-off between full load performance dependent on the specific power output and the part load emission behavior will be analyzed for future emission legislations. The shown results are based on single cylinder measurements and test cycle simulations.
Furthermore, an appropriate design of the boosting system is suggested. In a first assumption a two stage boosting system is required to achieve the boosting level, which is mandatory for higher power output. By means of GT-POWER simulations a tailored layout of the boosting system is found and investigated, which is capable to achieve, in combination with a superior combustion system, a specific power output of approximately 105 kW/L for a 1.6 L Diesel engine.
Keywords: Downsizing, diesel engines, CO2 reduction, power density, emissions