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SCR technology is becoming more and more important for the segment of diesel-driven passenger cars. Due to space and functional demands the dependency of SCR performance on a uniform supply of ammonia into the catalytic substrates is highly increased. Both an even distribution of the AdBlue® spray and a completed evaporation and decomposition of the droplets are the key to achieve the desired ammonia spread. Evaluation of the influence of spray quality on the AdBlue® decomposition and catalyst performance are leading to a new approach in dosing, using a special nozzle and air-supply strategy. The resulting new technology is evaluated and compared to the state of the art.

The reduction of particulate emissions from diesel engines is one of the most challenging problems associated with exhaust pollution control, second only to the control of NOx from any “lean burn” application. Particulate emissions can be controlled by adjustments to the combustion parameters of a diesel engine but these measures normally result in increased emissions of oxides of nitrogen. Diesel particulate filters (DPFs) hold out the prospect of substantially reducing regulated particulate emissions and the task of actually removing the particles from the exhaust gas has been solved by the development of effective filtration materials. The question of the reliable regeneration of these filters in situ, however, remains a difficult hurdle. Many of the solutions proposed to date suffer from high engineering complexity and/or high energy demand. In addition some have special disadvantages under certain operating conditions.

A modular particulate trap system for buses, trucks and other applications consiting of honeycomb traps and an electrical regeneration system has been designed and tested on a test bench and in a city bus. For regeneration, the soot is ignited at the entrance of the trap channel by electric heaters. After ignition, the soot burns self-supporting without further energy supply. Regeneration is possible over the whole engine map. The electrical energy consumption of the heaters for a city bus is in average below 100 W. The filtration efficiency of the system including regeneration is about 80 % during transient city driving. During regeneration, appr. 98 % of the accumulated hydrocarbons adsobed to the soot in the trap are burned off the initiated combustion front. Additionally, the odor of the diesel engine exhaust gas behind the trap is lowered at low engine load even during regeneration.

Diesel soot collected in a catalytically coated ceramic honeycomb trap, burns self-supporting, if the heat loss is less than the heat release due to soot oxidation. Experimental verification has been accomplished using a 4.66″ × 6″, 100 CPI trap. Ignition time and regeneration time are measured. At low speeds, a minimum ignition time of 15 s would be sufficient for the trap regeneration. An extended channel with an observation window is provided to allow examination of the regeneration. The soot is ignited at the beginning of the channel and the flame propagation is then observed. The soot burns through the channel in a match-like manner. Manganese and iron fuel additives are observed to have an effect on the mechanism of flame propagation.