Effect of High Levels of Boost and Recirculated Exhaust Gas on Diesel Combustion Characteristics at Part Load 2014-01-1245

Future diesel combustion systems may operate with significantly higher levels of boost and EGR than used with present systems. The potential benefits of higher boost and EGR were studied experimentally in a single-cylinder diesel engine with capability to adjust these parameters independently. The objective was to study the intake and exhaust conditions with a more optimum combustion phasing to minimize fuel consumption while maintaining proper constraints on emissions and combustion noise. The engine was tested at four part-load operating points using a Design of Experiments (DOE) approach. Two of the operating points correspond to low-speed and low-load conditions relevant for the New European Driving Cycle (NEDC). The other two points focus on medium load conditions representative of the World-wide harmonized Light-duty Test Procedures (WLTP). For the NEDC relevant conditions, improved fuel consumption was not achievable due to combustion noise constraints and the requirement for a very high turbocharger efficiency improvement of more than 20%. For the WLTP points, the Net Specific Fuel Consumption (NSFC) was improved by 11-12% with higher boost and EGR and improved combustion phasing while meeting Eu6 emission and noise constraints. The air flow and pressures for the WLTP points may be possible with next generation boosting systems.