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For meeting 21st-century exhaust emission standards for HD diesel engines, new methods are necessary for reducing NOx and PM emissions without increasing fuel consumption. The stratified diesel fuel-water-diesel fuel (DWD) injection in combination with exhaust gas recirculation (EGR) is as a means for NOx and PM reduction without any negative effect on fuel economy. The investigation was performed on a charged HD single-cylinder direct-injection diesel engine with a modern low-swirl combustion system, 4-valve technology and high pressure injection. The application of DWD injection combined with EGR resulted in a 60 percent lower NOx emission at full load and a 75 percent reduced NOx emission at part load when compared with present day (EURO II) technology. This was achieved without any fuel economy penalty, but with an additional PM emission reduction.

The high efficiency of the diesel engine has made it the primary propulsion source for truck applications worldwide. In Europe, the penetration of diesel engines in passenger cars is growing rapidly in an effort to meet the stringent CO2 future emission targets. However, future regulations call for increasingly lower NOx emission levels. Extremely low engine out NOx emission levels, if at all possible, have significant negative effects on fuel economy and engine life-cycle cost. As such, a viable strategy is to tune the engine for optimum fuel consumption, while relying on an exhaust aftertreatment system to reduce NOx emissions. The Selective Catalytic NOx Reduction (SCR) enables the engine to run in the overall speed/load range at best fuel economy, while the exhaust aftertreatment system reduces the NOx emissions significantly. The NOx reduction efficiency of an “engine map controlled”, open-loop SCR system is about 65 percent.