Chinese Professional Generator Set Manufacturers
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2025
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Why do diesel engines emit black smoke?
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Diesel engines easily emit black smoke from the exhaust at high loads.
Diesel engines easily emit black smoke from the exhaust at high loads. It is generally believed that when the load of the diesel engine is high, the amount of fuel injected into the combustion chamber increases, and the temperature in the combustion chamber is also high. In addition, the uneven formation of the diesel engine mixture will cause the combustion fuel with insufficient air in the local area of the combustion chamber to decompose and polymerize into soot (carbon black) under high temperature and oxygen deficiency conditions Charcoal smoke is not pure carbon, but a polymer mainly composed of carbon (over 85%) but also contains small amounts of oxygen, hydrogen, and ash, and its composition varies with the load of the diesel engine Collecting the black smoke through a filter and observing it under an electron microscope, it can be seen that the diameter of the large carbon smoke particles is around 0.05 μ m The high-temperature cracking reaction during combustion in diesel engines is inevitable, especially in space mixed combustion diesel engines where the high-temperature gas surrounds the liquid oil droplets, creating the most favorable conditions for cracking reaction. High speed photography of the combustion process proves that a large amount of black smoke will appear around the top dead center, but in general, the soot can find air in the subsequent combustion and burn completely, leaving no black smoke in the exhaust But if the air in the cylinder is insufficient and the mixing process is slow, the cylinder temperature will decrease due to expansion, and the carbon cannot burn and will aggregate into soot The formation of charcoal smoke reduces the fuel efficiency of incomplete combustion diesel engines, increases exhaust temperature, and emits black smoke from the exhaust. The surface area of the combustion chamber is covered with charcoal and the load cannot be further increased Carbon buildup can also cause faults such as piston rings or pistons getting stuck, and valves biting Therefore, diesel engines are not allowed to operate under long-term overload conditions
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