|Cut-away illustration of the Delphi Diesel Fuel Reformer shows the reforming catalyst. Click to enlarge.|
At the recent Engine Expo in Stuttgart, Germany, Delphi provided an update and some test data on its development of an on-board diesel fuel reformer for emissions control. (Earlier post.)
The on-board reformer will allow a Lean NOx Trap (LNT) to meet more stringent current and future emission regulations such as Euro 6 and EPA Tier 2 Bin 5 without major engine modifications or additional fluids, and at a lower cost than urea SCR.
Unlike catalysts, which continuously convert NOx to N2, LNTs (or NOx adsorbers) are materials which store NOx under lean conditions and release and catalytically reduce the stored NOx under rich conditions.
This process can perform well at high exhaust temperatures, but historically has demonstrated poor performance at lower exhaust temperatures. Low exhaust temperatures represent a large portion of vehicle operating time, particularly for medium- and light-duty diesel vehicles (including cars and SUVs) used in cities.
|On-board reformer design|
Through a catalytic partial oxidation process, the Delphi Diesel Fuel Reformer System converts diesel fuel into a hydrogen-rich stream of gas (reformate). The reformate is injected directly into the vehicle’s exhaust system to achieve optimal regeneration and desulfation of a Lean NOx Trap aftertreatment system and improve its emission reduction performance. The reformate is also used for diesel particulate filter regeneration.
Diesel Fuel + Air → Reformate CH2 + 0.5 (O2 + 3.8 N2) → H2 + CO + 1.9 N2 + Heat
The hydrogen generated on-board can also be used to serve other purposes, such as ammonia generation. This could eliminate the need for an external reductant such as urea when using a Selective Catalytic Reduction (SCR) System.
Applied in a Silverado full-size pickup truck, the reformer device helped reduce NOx emissions to 0.023 g/mi—well below the Tier 2 Bin 5 target of 0.05 g/mi.
|2004 Silverado LD FTP Emissions|
|Fuel Reformer System Average||0.3035||0.161||1.786||0.023||16.3|
|Tier 2 Bin 5 Standard||n/a||.075 – .09||3.4 – 4.2||.05 – .07|
Delphi is currently targeting production for the device in 2010.