Characteristics of Ultra-High EGR and Low Oxygen Diesel Combustion and its Dependence on Injected Fuel Quantities 18ICES/064
Authors
Hideyuki Ogawa - Hokkaido University
Hajime Shimizu - Toyota Motor
Shingo Kido - Kanto Auto Works
Noboru Miyamoto - Hokkaido University
Abstract
Ultra-low NOx and smokeless operation at higher loads up to half of the rated torque is attempted with large ratios of cold EGR. The NOx almost completely disappears and soot significantly increases when first decreasing the oxygen concentration to 16% with cold EGR, but after peaking at 14% oxygen, soot then deceases sharply to essentially zero at 10% oxygen while maintaining ultra low NOx and regardless of fuel injection quantity. However, at higher loads, with the oxygen concentration below 10%, the air/fuel ratio has to be over-rich to exceed half of rated torque, and thermal efficiency, CO, and THC deteriorate significantly. As EGR rate increases, exhaust gas emissions and thermal efficiency vary with the intake oxygen content rather than with the excess air ratio.