In-cylinder production of hydrogen during net-lean diesel operation

Hydrogen (H₂) is an excellent reductant, and has been shown to be highly effective when introduced into a variety of catalysts such as three-way catalysts, lean NOx traps (LNTs), and hydrocarbon lean NOx catalysts (also termed hydrocarbon selective catalytic reduction (SCR) catalysts). Furthermore, since lean-burn engines offer improved fuel efficiency yet difficult NOx emission control, H₂ production during lean operation for the purpose of NOx reduction could be beneficial. On-board generation of hydrogen is being explored via catalytic or plasma-based reformers. A possible alternative to these add-on systems is generation of the H₂ in-cylinder with standard fuel injection hardware. This paper details experiments relating to the production and measurement of H₂ under net-lean operation in a common-rail diesel engine. In-cylinder fuel control is used to tailor the combustion process such that H₂ is generated while maintaining a lean Air:Fuel ratio in the bulk exhaust gas.