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A brief study has been undertaken with exhaust gas recirculation (EGR) applied to a prototype low emission, heavy duty, direct injection (DI) diesel engine aimed at evaluating the potential for low nitrogen oxide (NOx) emissions. By virtue of the very low smoke levels achieved with the prototype engine, EGR can be applied at full load for substantial reductions in NOx down to c. 2.5 g/kWh (1.9 g/hph) over the European R-49 13-Mode test. These results were achieved with competitive particulates and fuel consumption and without recourse to engine de-rating. Compliance with the NOx emissions proposed for the year 2000 Japanese market was also demonstrated. These results are summarised in this paper and justify the need for a major research programme aimed at demonstrating the full potential of using EGR to develop a fuel efficient, low emission truck engine concept for the 1990's and beyond.

It is expected that heavy duty engine legislation in Europe will continue to drive down test cycle BSNox emissions to levels of between 2.5 and 3.5 g/kWh by 2005, with a reduction in particulate emissions to between 0.02 and 0.08 g/kWh. It is unlikely that re-optimisation of existing engine combustion systems alone, such as further retardation of the fuel injection timing, will be sufficient to meet the legislated BSNox targets. Other measures, such as cooled EGR or new aftertreatment systems must therefore be considered. Such emissions control strategies may conflict with other market requirements for improved fuel consumption and increased power density. In this paper, research at Ricardo into the configuration of a premium heavy duty truck engine for the European market for model year 2005 and beyond, is described. A review of the market requirements, projected to 2005 was undertaken in order to define the specification of the concept engine.