Combustion Features and Emissions of a DI-Diesel Engine with Air Path Optimization and Common Rail Fuel Injection

Emission and performance parameters of a medium size, and medium speed D.I. diesel engine equipped with a Miller System, a new developed High Pressure Exhaust Gas Recirculation System (HPEGR), a Common Rail (CR) system and a Turbocharger with Variable Turbine Geometry (VTG) have been measured and compared to the standard engine. While power output, fuel consumption, soot and other emissions are kept constant, nitric oxide emissions could be reduced by 30 to 50% depending on load and for the optimal combination of methods.

Heat release rate analysis provides the reasons for the optimised engine behaviour in terms of soot and NO_x emissions: The variable Nozzle Turbocharger helps deliver more oxygen to the combustion process (less soot) and lower the peak gas temperature (less NO_x). The flexible common rail system delivers higher injection pressures and thus more intense fuel-air mixing (less soot), while allowing later combustion phasing for the same bsfc and thus lower peak temperatures (less NO_x).

Therefore the combination of flexible air and fuel paths yields a synergistic optimisation of engine operation in global terms.