High Performance Cooling and EGR Systems as a Contribution to Meeting Future Emission Standards

In relation to further tightening of the emissions legislation for on-road heavy duty Diesel engines, the future potential of cooled exhaust gas recirculation (EGR) as a result of developments in the cooling systems of such engines has been evaluated. Four basic engine concepts were investigated: an engine with SCR exhaust gas aftertreatment for control of the nitrogen oxides (NO_x), an engine with cooled EGR and particulate (PM) filtration, an engine with low pressure EGR and PM filtration and an engine with two stage low temperature cooled EGR also with a particulate filter. A 10.5 litre engine was calibrated and tested under conditions representative for each concept, such that 1.7 g/kWh (1.3 g/bhp-hr) NO_x could be achieved over the ESC and ETC. This corresponds to emissions 15% below the Euro 5 legislation level. It was found, as a consequence of the two stage low temperature EGR cooling, that not only could the fuel economy of the engine be improved compared to that with conventional EGR cooling but that this economy was similar to that of the SCR engine concept (when the urea solution consumption was taken into account). The required cooling performance was achieved via optimisation of the cooling system without an increase in the fan power requirement. It was also found that the engine with two stage low temperature cooled EGR could achieve NO_x emissions significantly less than 1 g/kWh (0.7 g/bhp-hr) over the legislated test cycles with consistent fuel economy.