9. Special processes for reducing pollutant emissions

As the most conventional diesel engine designs and operating modes have already been described above, we will now take a general look at the problems of reducing pollutant emissions and the specific processes that can be implemented, bearing in mind that they are generally adaptable to the various types of engine.

Three objectives appear to be priorities for short- and medium-term development:

• the need to reduce the production of nitrogen oxides in the combustion chamber, since in practice it is very difficult to eliminate them a posteriori in the exhaust gases;

• obligation to reduce consumption due to the greenhouse effect caused by carbon dioxide emissions;

• lower unburnt emissions.