Investigation of the nitrogen oxide reduction characteristics and in-cylinder controls of the regeneration mode of a lean nitrogen oxide trap catalyst in a light-duty diesel engine

Abstract

This investigation focused on an in-cylinder control method to create a rich atmosphere inside a lean nitrogen oxide trap catalyst. The experimental procedures can be summarized as follows. To adjust to the excess air ratio values of 0.92 and 0.96, the air mass was fixed using a limited post-injection quantity from an engine management system, the main injection timing was slightly adjusted to create a rich atmosphere inside a lean nitrogen oxide trap catalyst in advance and the precise values were adjusted by regulating the post-injection timing together with the post-injection quantity calculated using the logic of the engine control unit. The results were as follows. First, the main-injection quantity was greatly reduced when a post-injection quantity was supplied. Second, it was verified that the post-injection quantity participated in generating the torque. Third, the overall efficiency was 26-63% and included a storage efficiency of 11-51%, a reduction efficiency of 56-89% and a conversion efficiency of 11-50%. Fourth, to control the lean nitrogen oxide trap catalyst temperature and its performance precisely using a small value, which was caused by the post-injection quantity, as the speed (r/min) increased, the air mass supply must be increased more during the rich mode than during the lean mode.