Various methods of control emissions Main pollutants from diesel engines are, HC, CO, smoke and odour of aldehydes, particulate matters etc.

The method of reducing, HC, and CO, emissions in diesel engines are the same as discussed above for emissions control in S.I. engines. Therefore, only the methods of controls of smoke and odour are discussed below.

Control of Smoke:

Black smoke represents the carbon particles suspended in exhaust and its formation is a process of conversion of hydrocarbon fuel into particles of soot. The poor combustion and incorrect A.F. ration is the main cause of production of smoke in diesel engines. The magnitude of smoke increase with the increase in load on the engine.

Method of control of smoke are:

De-rating and maintenance: There is hardly any method which can successfully control the root except to run the engine at reduced loads (i.e. derating) and maintain the engine at best possible condition in particular its injections system.

Smoke suppressing additives: Some of the compounds like barium compounds when added in d=fuel reduced the temperature of combustion and avoids the soot formation. Even if soot is formed, this compound breaks the soot into fine particles and reduce the smoke formation.

But, the barium compounds have tendency to increase deposit formation on the engine and reduces filters life.

Fumigations: it involves the injection of small amount of fuel into intake manifolds. This enhances the preflame reactions and reduces the chemical delay period. The reduced chemical delay period curds the thermal cracking which is responsible for soot formation.

Catalytic converters: The use of catalytic converters for reduction of smoke in diesel engines have not been found effective so far since these are found to interfere CO, HC, and emissions. However, the research is on for search catalyst to reduce smoke in engines.