EGR technology for lowest emissions

An EGR system for turbocharged and aftercooled HD diesel engines has been demonstrated on a 12 litre 315 kW engine with 4 valves per cylinder and a high pressure injection system. In this system exhaust gas is tapped off before the turbine, run through a cooler and mixed with the intake air after the compressor and aftercooler. The EGR system combines a novel, very efficient venturi-mixer unit with a VGT turbocharger. The venturi-mixer is positioned between the aftercooler and the intake manifold and provide such a suction power to the EGR gas. A first report showed that optimization of EGR quantity and injection timing enabled emission levels in the ECE R49 test below 3 g/kW h for NOx and around 0.10 g/kWh for particulates without a substantial increase in fuel consumption. Since then tests have continued with different fuels and with different EGR hardware. This paper gives further and more detailed information on the venturi-mixer characteristics and on how its interaction with the turbocharger influences engine operation and EGR potential. It is also shown that especially with some oxygenated fuels increase of particulate emissions with EGR could be minimal