Performance of a Urea SCR System Combined with a PM and Fuel Optimized Heavy-Duty Diesel Engine Able to Achieve the Euro V Emission Limits

In order to meet the Euro V heavy-duty diesel emission standard legislation limits, a diesel engine can be optimized by internal means to give low particulate emissions and lower fuel consumption. These modifications of the engine lead inevitably to higher NOx emissions due to the NOx/PM trade off. An efficient Urea SCR after-treatment system is then able to reduce the higher NOx emission to below the Euro V 2.0g/kWh legislation limit. This paper presents tests made on a PM optimized 12 liter heavy-duty diesel engine together with a urea SCR after-treatment system. The optimized engine had engine out particulate emissions of about 0.04 g/kWh and NOx emissions of 9 g/kWh for the ESC and 8,5 g/kWh for the ETC. The fuel consumption of the optimized engine was 194 g/kWh for the ESC and 198 g/kWh for the ETC as compared to state of the art Euro III engines of typically 210 g/kWh for the ESC, giving significant fuel savings of 7.5 %.

Combining the engine with a 20 liter 300-cpsi SCR catalyst, catalyst volume to cylinder ratio of 1.7, the particulate emissions dropped to 0.017 g/kWh for the ESC and 0.020 for the ETC. Particle size measurements also showed a decrease in the number of fine particles. With a urea injection corresponding to about 8-9% of the fuel flow the NOx emissions were reduced to 1.4 g/kWh for the ESC and 1.5g/kWh for the ETC with low ammonia slip. These reductions correspond to a NOx conversion of 84 % and 82% for the ESC and ETC respectively.

Thus the optimized engine combined with the urea SCR after-treatment system was compliant with the Euro V emission limits.