Strategies to Meet Worldwide Heavy-Duty Diesel Emission Standards

The most severe exhaust emission standards for heavy-duty diesel engines will be introduced in the United States in 1994 and 1998 and standards of similar severence have been announced in Japan and in Europe. While in the United States emissions have to be measured in a transient cycle, in both of the other two geographical areas, Europe and Japan, special steady state cycles have been adopted for certifying heavy-duty diesel engines. In the first part of the paper the main characteristics of the three test procedures are compared and those load-speed operating areas identified which most significantly contribute to cycle emissions. Of these, NOx and particulates are the most challenging components. Strategies to reduce them are outlined in later parts of the paper. Emphasis is placed primarily on technologies for in-cylinder emissions reduction, but exhaust gas aftertreatment by diesel oxidation catalysts is also addressed. The achievements of these technologies will be demonstrated by test results from heavy-duty diesel engines of the 1 to 2 litre/cylinder categories.