NOx Trap Regeneration with an On-Board Hydrogen Generation Device 2004-01-0582

In order to enable the regeneration of NOx traps at low temperatures and reduce the fuel penalty, an innovative fuel reformer has been developed to create a hydrogen-rich gas from diesel fuel to be used as the NOx reductant. This paper outlines the experimental use of this hydrogen generation device on a dual-leg NO_x trap system with an 8.3L diesel engine. The system was tested at six ESC modes, and gave satisfactory results at those engine conditions where the NOx trap had good adsorption capacity (exhaust temperature < 450 °C). With the NOx conversion efficiency of 80% as the target, the fuel economy penalty was about 3% for most engine conditions. Since this type of diesel engines are widely used for urban transit buses, the system was also tested at six typical road conditions and showed satisfactory results in terms of both NOx conversion efficiency and fuel economy penalty. A comparison with diesel fuel as the NOx reductant was conducted with the same test setup. At the same fuel penalty, the NOx conversion efficiency was much higher with the H₂-rich reformate gas than with diesel fuel. To achieve same NOx conversion efficiency, the fuel penalty with the reformate gas was only half of that required with diesel fuel. Therefore, this hydrogen generation device in combination of NOx traps is a promising technology for the NOx abatement of diesel engines.