Large-scale diesel engine emission control parameters

An extensive worldwide investigation and development effort is ongoing in order to make the performance of advanced reciprocal internal combustion engines meet emissions requirements for years to come. The ability to burn different fuel types (such as light and heavy fuel oil, LFO and HFO, but also others) has become a characteristic but also major design target for large-scale medium speed diesel engines. In this study emission tests have been carried out on a large-scale medium-speed supercharged diesel engine (∼1 MW per cylinder) with control parameters compression ratio, SOI and fuel type (LFO and HFO). Emissions of NOx, CO, hydrocarbons (HC) and smoke (FSN) were measured and presented here, and are discussed in relation to the control parameters. Regarding turbocharger influence on emissions the control parameters by-pass and waste-gate are also briefly addressed. The results show that NOx, CO and FSN decrease while HC emissions increase with later SOI (more retardation, more delay) for all loads (25-100%). The influence of compression ratio (CR) for NOx is the inverse of this, with decreasing CR giving increased NOx. Nozzle design (number of holes, holes diameter, injection angle, etc.) is important for emissions control and it seems that less holes and bigger diameter for a certain injection angle gives the best performance. Fuel type is important as well, and generally it can be said that LFO produces less gaseous or particulate emissions. Diesel engine turbocharger by-pass and wastegate valves do affect large-scale diesel engine emissions.