Effects of EGR, Swirl, and Cylinder Deactivation on Exhaust Temperatures of a Throttled Light-Duty Diesel Engine under Idle Conditions 2019-01-0544

This study extends a previous study on the effects of intake throttling and post-injection on light-duty Diesel engine exhaust temperatures and emissions, and includes the effects of EGR, in-cylinder swirl air motion, and cylinder deactivation. The baseline injection strategy was adapted from a 2014 Chevrolet Cruze having an engine similar to the light-duty GM engine used for this study. While the engine was fixed to a motoring engine dynamometer, the dynamometer was not active for the study, as the engine was operated under idle conditions. The desired idle speed was controlled using a feedback loop in the control algorithm to vary the duration of the main injection event.

Three methods were investigated. In the first method, the engine was operated fully warmed up, firing all four cylinders. Two rail pressures of 400 and 550 bar were studied, with the injection strategy and throttle position defining the baseline operating conditions, around which the effects of EGR and swirl were studied. The degree of throttling possible was determined by the ability of the engine to maintain a stable idle at 850 rpm. The parameters measured included MAP, exhaust temperature, exhaust concentrations of NOx, HC, and CO₂, as well as, IMEP and COV of IMEP. For the baseline idle conditions without intake throttling, the exhaust port temperature was approximately 80-90^oC. It was found that under unthrottled idle conditions, EGR had little effect on emissions, but NOx was slightly reduced by the increasing EGR rate as throttling was increased, for which temperatures were elevated by as much as 80^oC. Swirl had a negligible effect on HC emissions.

Methods 2 and 3 involved deactivation of fueling to two cylinders with and without valve deactivation (Methods 2 and 3, respectively). This was found to allow for greater amounts of post-injection fueling relative to operation on all four cylinders, and could results in increases in idle exhaust port temperatures of as much as 200^oC versus that for unthrottled operation with all cylinders firing.