LPL EGR and D-EGR Engine Concept Comparison Part 2: High Load Operation

摘要

The ongoing pursuit of improved engine efficiency and emissions is driving gasoline low-pressure loop EGR systems into production around the globe. The Dedicated EGR (D-EGR) engine was developed to minimize some of the challenges of cooled EGR while maintaining its advantages. The D-EGR engine is a high efficiency, low emissions internal combustion engine for automotive and off-highway applications. The core of the engine development focused on a unique concept that combines the efficiency improvements associated with recirculated exhaust gas and the efficiency improvements associated with fuel reformation. To outline the differences of the new engine concept with a conventional LPL EGR setup, a turbocharged 2.0 L PFI engine was modified to operate in both modes. The second part of the cooled EGR engine concept comparison investigates efficiency, knock resistance, combustion stability, and maximum load potential at high load conditions. These results document the superior knock tolerance and stability of the D-EGR concept over the LPL EGR embodiment and how to overcome the combustion limitations that have historically limited SI engine efficiency at high EGR dilution levels. This study also demonstrates that the reformate is the source of the improved knock mitigation of a D-EGR concept by comparing the D-EGR results to a LPL EGR engine with and without supplemental H_2 and CO at high loads.