Ultra-High Fuel Injection Pressure with Massive EGR to Enable Simultaneous Reduction of Soot and NOx Emissions

In this study both double and triple injection strategies were used with fuel pressures up to 300 and 250 MPa, respectively. Tests were conducted at medium load conditions with cooled, high-pressure EGR at a ratio of 40% and higher. A four-cylinder production engine, featuring double turbochargers with one variable geometry turbocharger, was tested. The double injection strategy consisted of a 20% close-coupled pilot injection while the triple injection strategy introduced a post injection consisting of 10% the total cycle fuel. Results of this study do not indicate an advantage to extreme fuel pressure. The increased air entrainment reduces soot while increasing the premixed burn heat release, mean cylinder temperature, and NOx. Compared to the double injection scheme, triple injections achieved much lower soot for the same EGR rate with only a small NOx penalty. Under the conditions tested, triple injections could be used with high EGR as a mixing strategy, allowing for the use of fuel pressures below 200 MPa to achieve a low FSN that can be effectively cleaned by the DPF.