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A technical approach to reduce NOx and to minimize the fuel consumption caused by the DeNOx aftertreatment system was introduced. The NEDC mode test of the HMC (Hyundai Motor Company) DeNOx system was done with a Euro 5 vehicle (ETW (Equivalent Test Weight) = 1,810 kg, 143 kW, 430 N⋅m), which resulted in that the Euro 6 legislation standards were met. The NOx and HC emissions were, respectively, measured to be 0.059 g/km and 0.087 g/km with the hydrothermal-aged catalysts, and CO₂ was increased by ≺ 4%.

A NOx absorber and a fuel cracking catalyst were combined to investigate whether this could increase the low temperature activity of a NOx absorber system. Before engine exhausted gas tests, the activity and properties of the NOx absorbing catalyst were examined by simulated gas and temperature programmed desorption. Diesel fuel cracking catalysts were designed to maximize the hydrogen productivity. From the hexadecane reaction experiments for these catalysts, it was found that the hydrogen generation amount was significant even at 200°C. Engine bench test results with the diesel fuel cracking catalysts confirmed the improvement of NOx removal efficiency. In case of high NOx capacity with prolonged regeneration interval condition showed the best results. It reflects the importance of optimization of the NOx absorber and the pre-oxidation catalyst, the regeneration strategy.

In diesel engine development, the new technology is coming out to meet the stringent exhaust emission regulation. The regulation demands more eco-friendly vehicles. Euro6c demands to meet not only WLTP mode, but also RDE(Real Driving Emission). In order to satisfy RDE mode, the new technology to reduce emissions should cover all operating areas including High Load & High Speed. It is a big challenge to reduce NOx on the RDE mode and a lot of DeNOx technologies are being developed. So the new DeNOx technology is needed to cover widened operating area and strict acceleration / deacceleration. The existing LNT(Lean NOx Trap) and Urea SCR(Selective Catalytic Reduction) is necessary to meet the typical NEDC or WLTP, but the RDE mode demands the powerful DeNOx technology. Therefore, the LNT & Urea SCR on DPF was developed through this study.