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In order to further reduce NOx emissions in increasing HP EGR cooler performance, several OEMs have decided to use a secondary cooling loop dedicated to bring cold water (around 35°C) to the HP EGR heat exchanger. Nevertheless, strongly cooled EGR gases can condensate in the cooler-producing acidic liquids which can corrode some parts in the loop. It is therefore necessary to define EGR components compatible with such kind of environment and constraints. Testing was performed on a 2.0-liter EU4 diesel engine, using a large panel of current fuels including neat biodiesels from soybean, rapeseed or palm, as well as low and high sulfur petroleum-based diesels. In order to cover all existing cycle conditions, the HP EGR is cooled from 20°C to 90°C independently from the engine coolant circuit.

Testing was performed on a 2.0 liter diesel engine with high pressure (HP) and low pressure (LP) EGR, using standard European low sulfur diesel as well as fatty acid methyl ester (FAME) biodiesel fuels produced from soy, rapeseed and palm feedstock, both neat and blended with 50% standard diesel. In the HP EGR configuration, fuel injection, air flow and EGR rate were adapted to achieve the same engine load and NOx emissions for all fuels at the selected test points. Higher brake specific fuel consumption and lower smoke emissions were observed for the biodiesels compared to the standard diesel. In the LP EGR configuration, large reductions in NOx and smoke were observed for all fuels compared to HP EGR. In addition, water condensed in the charge air cooler at coolant temperatures below 30°C. This condensate was collected and analyzed, finding similar volumes and acidity for condensates from all the diesel and biodiesel fuels.