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An EGR system for turbocharged (and aftercooled) heavy-duty diesel engines has been demonstrated on a 12 litre 315 kW engine with 4 valves per cylinder head and high pressure injection system. In the EGR system exhaust gas is tapped off before the turbine, run through a cooler and mixed with the intake air after the compressor and aftercooler. This is done with a minimum of disturbance to the pressure balance across the engine by combining a very efficient venturi-mixer unit with a VGT turbocharger. The venturi-mixer is positioned between the aftercooler and the intake manifold and provides a suction power to the EGR gas. Optimization of EGR quantity and injection timing reduced the NOx emission over the European 13-mode test by almost 60% to 2.4 g/kWh. Particulate emissions were 0.107 g/kWh and the BSFC penalty 2.5%. Initial tests demonstrate acceptable transient behaviour when using a dedicated control strategy.

A urea SCR deNOx system for heavy-duty diesel engines was developed comprising a SCR catalytic converter combined with a low sulfate formation oxidation catalyst. Urea is injected upstream the SCR catalyst system by means of an open-loop controlled injection system. Test bed investigations with the urea deNOx system applied to a 315 kW EURO 2 baseline heavy-duty diesel engine demonstrated a NOx emission reduction potential down to a level of less than 3 g/kWh. Heavy-duty diesel engines equipped with such a deNOx converter are able to comply with the expected EURO 4 NOx emission limits, independent from the ultimately effective test cycle. The particulate emission level of the EURO 2 engine was found not to be influenced by the SCR catalyst. The combination of SCR and oxidation catalyst results in a particulate increase of up to 25%, depending on the utilized test cycle.