Effects of EGR, Swirl, and Cylinder Deactivation on Exhaust Temperatures of a Throttled Light-Duty Diesel Engine under Idle Conditions. 2019-01-0544
Modern Diesel exhaust emissions control devices rely on catalysts for effective treatment. These catalysts must be maintained above a certain temperature, usually > ~200oC, to remain effective. Under low-load and idle conditions, the engine exhaust temperature of the engine may be significantly lower than the catalyst activation temperature. Particularly in congested urban settings, it can be common for light-duty vehicles to operate under idle and very low-load for considerable periods. This can lead to tailpipe emissions if the catalysts are not fully active.
This study extends a previous study on the effects of 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.
The engine operating parameters considered included two idle speeds of 800 and 1100 rpm, with the engine fully warmed up. Two rail pressures of 500 and 800 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. The parameters measured included exhaust temperature, exhaust concentrations of NOx, HC, CO, and CO2, as well as, IMEP and COV of IMEP.
For the baseline idle conditions, manifold-out exhaust temperature was approximately 80-100oC. It was found that under unthrottled idle conditions, EGR had little effect on emissions, but NOx was slightly reduced by increasing EGR rate as throttling was increased, for which temperatures were elevated by as much as 100oC. Swirl had a small effect on HC emissions.
Yousif Alsulaiman, Meng Lyu, Tayyar Ozel, Matthew J. Hall, Ronald Matthews
University of Texas at Austin, Univ. of Texas-Austin, Univ of Texas-Austin