Technical Paper
NOx Reduction by Injection Control
1990-02-01
900637
The reduction of NOx without the degradation of soot emission and/or fuel economy necessitates the grasp of the in-cylinder temperature behavior, since NOx is mainly generated within localized high-temperature regions in the cylinder of diesel engines. Therefore, the in-cylinder temperature distributions were measured by the two-color method. This temperature distribution measurement enabled the characterization of the NOx reduction mechanisms for two methods by injection control; injection timing retard and pilot injection. Injection timing retard lowers the temperature throughout the combustion chamber, where NOx is reduced by controlling the spatial development of localized high-temperature regions. On the other hand, pilot injection delays the development of high-temperature regions. NOx is reduced by controlling the temporal development of the localized high-temperature regions. Furthermore, a novel method to reduce NOx has been proposed.