Views: 50 Author: Site Editor Publish Time: 2021-06-29 Origin: Site
Some diesel engines, such as the 441KW 6 cylinder water cooled diesel engine and the 12 cylinder 4 stroke new diesel engine, have been used for a long period of time, and malfunctions such as increased oil and diesel smell in the oil will occur. In this case, it is generally caused by diesel oil entering the engine oil. So how does diesel enter the engine and mix with engine oil? Generally speaking, there are two channels for diesel oil to enter the engine oil: first, from the combustion chamber through the gap between the piston and the cylinder wall; second, from the high-pressure pump.
First, let's analyze the first channel. During normal operation, the high speed 4 stroke diesel engine injects diesel fuel into the combustion chamber regularly, quantitatively and at constant pressure through the fuel injector installed on the cylinder head, and then ignites and burns, generating high-temperature and high-pressure gas to push the piston down. It can also be said that the diesel fuel injected into the combustion chamber is completely burned into exhaust gas. But if for some reason, the injector is injected with excessive diesel, or the injected diesel does not burn, the excess diesel will enter the oil pan from the gap between the piston and the cylinder wall and mix with the engine oil. As a result, the viscosity of the engine oil decreases and the lubricating performance decreases, thereby aggravating the wear of the engine. Therefore, the entry of diesel into the engine oil is a serious mechanical failure.
The main reason is that the needle valve of the injector is stuck, causing the diesel to flow directly into the combustion chamber. In this case, diesel does not start fuel injection at the end of the compression stroke, but always supplies fuel to the combustion chamber, so that a large amount of diesel cannot be burned, and then flows into the oil pan. Also, the diesel fuel injected into the combustion chamber does not burn, and condenses in the combustion chamber and flows into the oil pan. This situation is mainly due to the clogging of the injection hole of the fuel injector, and the injected diesel is not sufficiently atomized and cannot be burned. In short, it is all the trouble caused by the injector, just remove the injector and recalibrate it.
Another way is for diesel to flow into the oil pan from the high-pressure pump and mix with the engine oil. Since the high-pressure pump needs oil lubrication during operation, a special oil passage leads to the lower part of the high-pressure pump, and above it is the oil supply plunger of the high-pressure pump. If the plunger ruptures, seizes, or is damaged, diesel will flow out of the gap between the plunger and the plunger body, mix with the engine oil below, and then flow back into the oil pan.
Of these two channels, the first is the most common. Injector needle valve is a kind of extremely precise mating couple. It is repaired in pairs during processing. The mating gap is only 0.003~0.005mm. Not to mention diesel, it is difficult for air to pass through this gap. However, its cleanliness requirements for diesel are extremely high. If there are some impurities in diesel, it will be stuck.
Therefore, the diesel filter of the powerful 12 cylinder diesel engine is a very important component, and it must be replaced and maintained in time. In addition, the 6 cylinder water cooled diesel engine should also pay attention not to use too low-grade diesel oil. If it is cold“hanging wax”, these paraffin wax crystals are extremely harmful to the injector needle valve.