EGR System Integration on a Pump Line-Nozzle Engine

The minimum oxides of nitrogen (NO_x) emissions over the U.S. Federal Test Procedure (FTP) using exhaust gas recirculation (EGR) were investigated on a heavy-duty diesel engine featuring a pump-line-nozzle fuel injection system. Due to the technical merits of electronic fuel injection systems, most accounts of EGR system development for heavy-duty diesel engines have focused on these types of engines and not engines with mechanical fuel systems. This work details use of a high-pressure-loop EGR configuration and a novel, computer-controlled, EGR valve that allowed for optimizing the EGR rate as a function of speed and load on a 6L, turbo-charged/intercooled engine. Cycle NO_x levels were reduced nearly 50 percent to 2.3 g/hp-hr using conventional diesel fuel and application of only EGR, but particulates increased nearly three-fold even with the standard oxidation catalyst employed. Particulate analysis revealed that the insoluble contribution to the particulate increased with EGR amount thereby decreasing the effectiveness of the oxidation catalyst as a particulate countermeasure. Tests with an added 1.82-percent oxygenate in the fuel resulted in a 10-percent reduction in particulates. The EGR strategy selected for the best NO_x particulate tradeoff over the European and Japanese test cycles resulted in a 13-percent reduction in NO_x .