Effective Usage of LNT in High Boosted and High EGR Rate of Heavy Duty Diesel Engine

Lean NOx trap (LNT) and Urea-SCR system are effective aftertreatment systems as NOx reduction device in diesel engines. On the other hand, DPF has already been developed as PM reduction device and it has been used in various vehicles. LNT can absorb and reduce NOx emission in wide range exhaust temperatures, from 150°C to 400°C, and the size of LNT component can be compact in comparison with Urea-SCR system because LNT uses the diesel fuel as a reducing agent and it is needless to install the reducing agent tank in the vehicle. In this study, authors have shown that the NOx conversion rate of LNT is high in the case of extremely low NOx concentration from the engine. Also, the effects of LNT and DPF were examined using the Super Clean Diesel (SCD) Engine, which has low NOx level before aftertreatment and has been finished as Japanese national project. The specifications of SCD Engine are a turbo-intercooled and in-line six-cylinder diesel used high-boost and high EGR rate system and it has thoroughly reduced NOx and PM before aftertreatment. The fuel dosing system was installed in the exhaust pipe before LNT in order to make rich spikes. The control logic of the effective fuel dosing was designed and the effects of LNT and DPF were examined in transient JE05 test mode of Japan. As a result, LNT is effective under the low NOx and low PM concentrations before aftertreatment such as SCD Engine. The reduction rate was 80% by LNT with 2.4% of fuel penalty as reducing agent in Japanese JE05 test mode by controlling rich spikes at the fuel dosing system. And also, 90% of PM of engine-out was removed by DPF.