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As a result of WNTE regulations and the introduction of close-coupled aftertreatment systems, exhaust purification at high temperatures in commercial vehicles has become increasingly important in recent years. In this report, we improve the prediction accuracy for NOx conversion at high temperatures in the kinetic model of conventional Cu-selective catalytic reduction (Cu-SCR). Reaction rate analysis indicated that the rate of NH3 oxidation was extremely low compared to the rate of standard SCR. We found that NOx concentration-dependent NH3 oxidations (termed NOx-assisted NH3 oxidations) were key to the rate of NH3 oxidation. The output of the improved Cu-SCR kinetic model was in agreed with experimental results obtained from the synthetic gas bench and engine dynamometer bench. We analyzed the contribution of each reaction to NH3 consumption during Cu-SCR. Under NH3 + NO + O2, standard SCR was dominant at low temperature.

Application of pre-mixed compression ignition (PCI) combustion for multi cylinder DI diesel engine has been reported in a previous paper [1]. On the FTP75 vehicle test cycle, application of the PCI combustion demonstrated a 50% decrease in the NOx level without any deterioration in fuel economy. In this study, PCI combustion properties were investigated under the condition of enhanced heat exchange capability of EGR cooler on multi cylinder DI diesel engine. Test results showed that the exhaust emissions and performance of PCI combustion were improved by increasing heat exchange on EGR cooler and PCI combustion region was expanded to higher load. However, few issues were encountered using higher heat exchange EGR cooler.

Tier 2 Emission standards enacted by the U.S. Environmental Protection Agency (EPA) require substantial emission reductions for new vehicles, including those with diesel engines. The standards are fuel neutral, and all light duty vehicles must eventually meet a fleet averaged emission level of Bin 5. To improve the emission capability for diesel engines, several advanced technologies have been investigated. These technologies include: common rail FIE with multi-injection capability, enhanced cooled EGR system with increased flow capability, variable geometry turbo charger, and a lower compression ratio piston. A new combustion approach using premixed diesel combustion was applied in the low load area for improving NOx and soot emissions significantly in the FTP-75 test cycle. Applying these technologies, engine out NOx was substantially reduced while maintaining similar soot levels.

Control of NOx and PM from diesel engines is a key for enlarging its application in transportation field. To achieve this, many improvements have been done, for instance, the introduction of highly flexible common-rail injection system and cooled EGR system with advanced control strategy. In order to meet more stringent emission regulations in near future, research and development activities have been carried out energetically in the world. In this paper, a low emission combustion strategy is realized by combination of common-rail and cooled EGR. First of all, low soot combustion is approached by optimizing pilot and main injection, in which pilot is controlled to eliminate hot flame. Then, once low soot combustion achieved, higher EGR can be used to reduce NOx.

The behavior of air-entrainment in a Diesel fuel spray was studied by analyzing the air movement around a free non-evaporated Diesel fuel spray in a pressurized vessel. To measure the air movement around the spray. The density difference in the air near the surface of spray was measured as a tracer of the moving air. This was accomplished heating a stainless steel (SUS) wire with large current. The movement of air caused by the air-entrainment into the spray was recorded by a high speed camera system. By analyzing the recorded air movement, the air-entrainment was obtained. The effects of nozzle hole diameter, injection velocity and ambient gas density on the air-entrainment behavior were investigated. Some discussions were added to help considering the complex phenomena of air-entrainment into a Diesel spray, based on comparing the averaged air/fuel ratio inside the spray with both values of measurement and predicted by momentum theory.