In the description of many truck drivers, they think that the mixing of coolant with water or a small amount of coolant with water will not affect the use of the engine, even for 2-3 years. Often this kind of chronic corrosion can not attract attention, which will cause a chain reaction in the later stage, and the engine maintenance cost is very high. Cavitation is one of the fatal hazards.
Cavitation occurs around the engine combustion chamber. Although the feedback from the vehicle water temperature gauge is about 90 degrees, the engine combustion work, especially most wet cylinder liners, the local surface temperature exceeds the boiling point of water, which is much higher.
When water is near the boiling point, a large number of bubbles will be generated, which repeatedly impact the cylinder liner surface, and the pressure of the shock wave under the micro level reaches 15-20000 psi. In our daily life, when the teapot is boiling, the bubbles generated at the bottom of the pot are similar.
The coolant used in the engine usually has a boiling point temperature of more than 130 degrees. If the composition ratio of the coolant is destroyed, the ethylene glycol composition will be reduced. The cylinder liner is exposed to a low boiling point and alcohols cannot adhere to the surface. Cavitation cannot be avoided. For example, in the coolant test after mixing water 200 hours later, Cummins Cummins ntc400 engine has produced severe cavitation on the cylinder liner, resulting in more serious cavitation.
The early failure of Jiefang 6dm engine is relatively typical in the cavitation case typical accident case – wet cylinder liner cavitation of 6dl2 engine.
Domestic medium displacement engines have evolved technically from the 1970s, only equivalent to the level of foreign engines in the 1950s, and have not changed in essence. Therefore, at the beginning of the engine design, the requirements for the cooling system are not high, the combustion chamber is not strengthened, and the cavitation phenomenon also exists, but it is not obvious. Compared with the corrosion condition, it is more prominent, such as rotten water blocking.
Nowadays, domestic large displacement truck engines adopt supercharging, high compression ratio, shortened piston stroke and lower speed. Such enhanced design, local temperature of combustion chamber and forced heat dissipation requirements are mostly realized through piston oil nozzle, higher coolant circulation and coolant with higher boiling point temperature. Therefore, a small amount of coolant make-up water can be used for emergency in a short time. The disadvantages of long-term use outweigh the advantages. The service life of an engine with local frequent “boiling” is greatly shortened.
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