Search Results

Tests are carried out to assess the potential of using SCR DeNOx catalysis, for achieving ultra-low NOx emission levels with heavy-duty diesel engines. A prototype DeNOx catalyst system has been developed which consists of a moderately sized SCR catalyst, upstream of which urea is injected through a heat-shielded nozzle. Downstream of the SCR catalyst a low sulphate oxidation catalyst is used to ensure any ammonia slippage from the SCR stage is oxidized. The system was tested on a standard 2-valve EURO 2 engine over several steady-state and transient test cycles currently under discussion for European use. Over these test cycles NOx emission values of about 2 to 2.5 g/kWh are accomplished, which are sufficient to fulfill future European heavy-duty NOx emissions legislation to be expected around the year 2005.

In a vehicle demonstration programme the high compression lean burn technology showed good potential for further improving emissions and energy effiency of the average European car. At the US ‘83 emission control level a 10 per cent improvement in fuel consumption over the equivalent presentday vehicle was found under European city and highway driving conditions. An oxidation catalyst was found an essential and effective element of the set-up. Special attention should be paid to the representation of actual driving patterns in Europe in relation to the type approval test procedures. Especially for control of NOx emissions the situation is very unsatisfactory. Suggestions for improvement are made.