Combustion and Exhaust Emissions in a Heavy-Duty Diesel Engine with Increased Premixed Combustion Phase by Means of Injection Retarding

An experimental study has been conducted in a HD diesel engine operating at light load with standard injection and combustion systems, retarding the start of injection with the aim of promoting the first phase of combustion in premixed conditions. A detailed study of the combustion characteristics has been carried out by means of a combustion diagnosis model, and the basic phenomena behind the changes in engine performance and pollutant emissions have been studied. Retarded fuel injection has produced very low levels in nitrogen oxides (NOx) and soot emissions, with the inconvenient of higher carbon monoxide (CO) and unburned or partially burned hydrocarbons (HC) emissions and a significant penalty in fuel efficiency. At the light engine load operation point studied here, the combination of retarded fuel injection and the introduction of exhaust gas recirculation (EGR) has proven to be very efficient in achieving soot and NOx levels below the future emission regulations, at the cost of increased fuel consumption and high CO and HC emissions.