Abstract
Southwest Research Institute has demonstrated the ability of high levels of cooled EGR to significantly improve the fuel consumption of a positive ignition engine by reducing thermal losses, suppressing end gas knock and decreasing pumping losses. High levels of EGR dilution also simultaneously reduce the emissions of NOx, CO, and particle emissions across the full operating range of the engine. However, the use of cooled EGR has several challenges, including a reduction in combustion rates, decreased stability, lower combustion efficiency, and increased demands on the air handling system. A new concept for configuring engine hardware, called Dedicated EGR (D-EGR), was proposed in a previous publication to reduce many of these deficiencies and increase the fuel consumption benefit from cooled EGR. However, in the 4-cylinder application discussed in the previous work, the engine suffered from imbalances due to the pulsing nature of the Dedicated EGR loop. In this work, the D-EGR concept was pushed to the extreme. A V6 engine was configured to run with 50% EGR by using 3 of the 6 cylinders in D-EGR mode. A series of 1-D simulations was undertaken to investigate the potential to achieve the desired torque curve in D-EGR mode, examining single-stage and two-stage boosting with combinations of superchargers and turbochargers. An investigation of the dilution tolerance of various high energy ignition systems was performed to meet the aggressive 50% D-EGR target. Then engine was then demonstrated to operate with 50% D-EGR and the improvement in fuel consumption was documented at a series of part load conditions. The results show that this technology has considerable potential for high efficiency applications.
