Diesel smoke: Smoke is defined as visible products of combustion, is due to poor combustion. It originates early in the combustion. Rich fuel-air mixture & at pressures developed in diesel engines- produces soot. If soot is not burnt in combustion cycle it will pass in exhaust, & if in sufficient quantity, will become visible- as smoke.
Methods:
1. De-rating:- At lower loads, the air: fuel ratio obtained will be leaner & hence the smoke developed will be less. However this means a loss of output.
2. Maintenance: - Maintaining the injection system of engine properly results in a significantly reduced smoke, best engine performance, and clean exhaust system. Other methods are changes in Combustion chamber geometry.
3. Smoke suppressant additives:- Some barium compound, if used in fuel, reduce the temp of combustion, thus avoiding the soot formation, & if formed- they break it into the fine particles, thus appreciably reducing smoke.
4. Fumigation: - Fumigation consists of introducing a small amount of fuel into the intake manifold. This shortens the delay period- curbs thermal cracking which is responsible for soot format