Experimental Investigation of Combined LNT + SCR Diesel Exhaust Aftertreatment

In the present work, an exhaust aftertreatment system combining lean NO X trap (LNT) plus exhaust bypass, passive selective catalytic reduction catalyst (SCR) and engine-independent LNT reductant supply by onboard exhaust fuel reforming was developed. Further, it was experimentally investigated in steady-state operation on an engine test bench and on road in a demonstrator vehicle. The intrinsic NH 3 formation during the LNT regeneration was intensively studied as one key function for passive SCR without active urea dosing. LNT regeneration duration and temperature are the most significant parameters for NH 3 emission. In steady-state operation, the passive SCR could be forced to a contribution to the total NO X conversion of up to 35 %. At 170 °C, 50 % steady-state total NO X conversion was achieved, and at 250 °C and a fuel consumption penalty of