Search Results

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 NOx 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.

This paper describes the development of an exhaust Thermal Enhancer™ using an airless nozzle fuel system. The purpose of the Thermal Enhancer™ is to increase diesel engine exhaust gas temperatures to a level where catalytic heating can be used for Diesel Particulate Filter regeneration. The system can also be used to achieve adequate temperatures for NOx reduction, employing techniques such as Selective Catalytic Reduction. The Thermal Enhancer™ is used to increase exhaust gas temperatures at conditions that would otherwise be too cold for effective catalyst operation. These conditions include idle and low-load operation. The airless-nozzle fuel system is necessary for engines that do not have a compressed-air system. Performance data, including hydrocarbon slip as a function of Thermal Enhancer™ outlet temperature are presented at steady state conditions. Pressure loss as a function of engine speed indicates it is less than 1 kPa at the maximum exhaust flow rate.

This paper describes recent progress in our program to develop an emissions technology allowing diesel engines to meet the upcoming 2007/2010 regulations for NOx. At the heart of this technology is the ArvinMeritor Diesel Fuel Reformer that reforms the fuel, on-demand, on-board a vehicle. The fuel reformer uses plasma to partially oxidize a mixture of diesel fuel and air creating a highly reducing mixture of Hydrogen and Carbon monoxide. In a previous publication, we have demonstrated that using a reformate rich in H2 and CO to regenerate a NOx trap is highly advantageous compared to vaporized diesel fuel used conventionally. In this paper we present results and a strategy for performing desulfation of the traps using the fuel reformer. In contrast to vaporized diesel, which requires very high temperatures that fall outside the normal exhaust operating temperatures for diesel engines, desulfation was achieved at temperatures lower by more than 100 °C using the Plasma Fuel Reformer.

This paper describes recent progress in our program to develop an emissions technology allowing diesel engines to meet the upcoming stringent worldwide regulations for NOx. The Plasma Fuel Reformer (PFR) has the ability to rapidly convert diesel fuel (with air), to a hydrogen rich gas on-board a vehicle, which is then utilized to efficiently regenerate a NOx trap. We have made several advances on the PFR as well as on the NOx reducing system. The Plasma Fuel Reformer operating range has been extended by 120% up to 1.5 g/s fuel flow rate while retaining the high hydrogen and low soot characteristics. The plasma power consumption has been further reduced and the high voltage design has been made more robust. The T90 start-up time during regenerations has been reduced to less than 4 seconds. The NOx reducing system utilizes a novel algorithm for NOx trap regeneration that reduces the fuel penalty by 25% while increasing NOx conversion by 10%.