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Diesel Engine An Analysis Of The Causes Of Smoke

Diesel engine at normal operating temperature, the exhaust smoke color should be colorless or light gray, the so-called colorless is not completely colorless, not as petrol as colorless, but in colorless with a touch of gray, which is Normal exhaust smoke color. Diesel engine in the idle air smoke may be heavier in the high-speed, high load may also be heavier, we should pay attention to observe the normal exhaust smoke, in order to judge and analyze the abnormal exhaust smoke. Diesel engine fuel completely burned, the normal color is generally light gray, the load is dark gray when working. Diesel engine in the work, there will often smoke phenomenon, diesel engine smoke smoke, blue smoke, white smoke and gray four, they are one of the conditions to determine the diesel engine failure, the specific analysis is as follows:

Black smoke, also known as soot, diesel engine exhaust black smoke is mainly fuel mixture is too thick, the formation of combustible mixture or combustion is not perfect and other reasons. Diesel engine in the high temperature, high pressure combustion conditions, local hypoxia, pyrolysis and dehydrogenation to the formation of carbon as the main component of solid particles, is the combustion chamber fuel combustion is not complete performance. Because the diesel engine is heterogeneous combustion, the chemical reaction conditions in the various areas of the combustion chamber are inconsistent and change over time, so the smoke is likely to be generated by many different ways. Diesel is a complex hydrocarbon, injected into the combustion chamber of unburned diesel oil by high temperature decomposition, the formation of carbon black, exhaust with the exhaust together with the formation of black smoke. Black smoke is not completely burning products, hydrocarbon combustion in the case of high temperature and hypoxia release and polymerization process. In some cases the fuel is injected on the wall of the combustion chamber to form a liquid oil film, which is part of the final evaporation. Its combustion depends on its evaporation rate and the rate of fuel vapor mixing with oxygen. If the concentration of oxygen in the surrounding gas is too low or the speed of mixing is not sufficient, the fuel gas evaporated from the oil film will be decomposed and produce unburned hydrocarbons, incomplete oxidation products and black smoke.

According to the qualitative description, the generation of black smoke in the combustion process of diesel engine can be summarized as three stages - nucleation stage, single grain stage, single grain burning disappears or agglomerates into larger flocs. The main reason for its production is:

1. Piston ring, cylinder liner and other wear Diesel engine

Valve, piston ring, cylinder liner wear, resulting in insufficient compression pressure and oil up and down the combustion chamber, the cylinder at the end of the compression stroke, the normal mixture of mixed gas changes, so that fuel combustion in anaerobic conditions, the combustion process is easy to produce Coke, the exhaust emissions to form a large number of black smoke.

2. The shape of the combustion chamber changes Diesel engine

The shape of the combustion chamber due to manufacturing quality and long-term use led to the decline in technical conditions, so that the compression is too large, too small and the wrong position of the piston will make the combustion chamber shape and volume changes, thus affecting the fuel and air mixing quality, fuel combustion conditions Bad.

3. The injector is working poorly Diesel engine

Diesel engine exhaust smoke and fuel atomization quality are closely related to the diesel engine fuel injection process, each time the end of the injection, the injection pressure drop, poor atomization quality, so that the droplet diameter than the main jet phase Oil droplets 4 to 5 times larger (about 100 times the volume), these oil droplets evaporate and burn the time is short, the concentration of oxygen around the low, prone to smoke. The injector is not atomized, atomized or driped so that the fuel can not be adequately mixed with the air in the cylinder and can not be completely combusted. The phenomenon of black smoke caused by the poor operation of the injector is more pronounced at low speed operation of the diesel engine because the intake vortex in the cylinder at low speed is weak and the possibility that the oil droplets or oil beams are scattered by the airflow is reduced and the time Longer, easier to form carbon black discharge.