Numerical Evaluation of Direct Injection of Urea as NOx Reduction Method for Heavy Duty Diesel Engines 2007-01-0909

The effect of ammoniac deoxidizing agent (Urea) on the reduction of NO_x produced in the Diesel engine was investigated numerically. Urea desolved in water was directly injected into the engine cylinder during the expansion stroke. The NO_x deoxidizing process was described using a simplified chemical kinetic model coupled with the comprehensive kinetics of Diesel oil surrogate combustion. If the technology of DWI (Direct Water Injection) with the later injection timing is supposed to be used, the deoxidizing reactants could be delivered in a controlled amount directly into the flame plume zones, where NO_x are forming. Numerical simulations for the Isotta Fraschini DI Diesel engine are carried out using the KIVA-3V code, modified to account for the “co-fuel” injection and reaction with combustion products. The results showed that the amount of NO_x could be substantially reduced up to 80% with the injection timing and the fraction of Urea in the solution optimized.