1998-10-19

Selective Non-Catalytic NOx-Reduction in Diesel Engines Using Aqueous Urea 982651

High over-all efficiency, good performance together with low impact on environment and low lifecycle-costs are the major demands of truck engine customers. To fulfill these high demands, the potential of an SNCR (selective non catalytic reduction) process for NOx reduction as an alternative to catalytic exhaust treatment systems has been examined in this investigation [1]. Aqueous urea was used as the reducing species. The experimental tests were carried out on a heavy duty single cylinder research engine. The tests confirmed the applicability of a homogeneous non-catalytic selective reduction process.
By injecting aqueous urea directly into the combustion chamber a maximum NOx reduction of 65% could be achieved at full load and increased exhaust gas temperature.
Numerical analysis of the evaporation and mixing processes with the help of the simulation tool Kiva 3 imaged the mixing pattern of the reducing species and the burnt gases inside of the combustion chamber and brought about the direction of further improvement of the process.
The investigated SNCR process also led to the formation of unwanted reaction by-products. Therefore, extended investigation into the reaction mechanism for the formation of by-products, e. q. N2O, and the avoidance of their formation is needed before application of the SNCR process for the reduction of nitric oxides in the exhaust of C.I. engines.

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