Effect of EGR on Autoignition, Combustion, Regulated Emissions and Aldehydes in DI Diesel Engines

In view of the new regulations for diesel engine emissions, EGR is used to reduce the NOx emissions. Diluting the charge with EGR affects the autoignition, combustion as well as the regulated and unregulated emissions of diesel engines, under different operating conditions. This paper presents the results of an investigation on the effect of EGR on the global activation energy and order of the autoignition reactions, premixed and mixing-controlled combustion fractions, the regulated (unburned hydrocarbons, NOx, CO and particulates), aldehydes, CO₂ and HC speciation. The experiments were conducted on two different direct injection, four-stroke-cycle, single-cylinder diesel engines over a wide range of operating conditions and EGR ratios.