This phenomenon is called "cavitation" of the cylinder liner, that is, "cavity corrosion." As diesel engines develop in the direction of adjustment and strengthening, cavitation has become increasingly serious.

The characteristics of crust erosion are in the form of locally concentrated deep holes. In most cases, the damaged surface is clean, free of deposits of corrosive products, and appears on one side of the bearing surface of the cylinder liner.

 

The cavitation damage of the cylinder block and the cylinder liner causes cracks and even through holes, which causes the cooling water to enter the cylinder and the oil, which significantly reduces the life and reliability of the diesel engine.

 

The main source of cavitation is the vibration of the cylinder liner. When the piston reaches the top dead center, the direction of action of the side pressure changes, and the piston yaws from the side of the cylinder liner to the opposite side, and the phenomenon of the piston pendulum appears. Since the thermal gap is left between the piston and the cylinder liner, the oscillation of the piston is impactful. This impact causes strong vibration of the cylinder liner. When the cylinder wall vibrates, alternating stretching and compression occurs in the water chamber, causing localized high pressure and vacuum bubbles in the water near the outer wall. Under the action of high vacuum, the cooling water evaporates into bubbles, and some vacuum bubbles and bubbles occur in the tiny pinholes on the outer wall of the cylinder liner or are squeezed into the pinholes under the action of vibration. When the vacuum bubble or the bubble is broken by the high pressure impact, a pressure shock wave is generated in the vicinity of the rupture zone, and the pressure can reach several tens of atmospheric pressure and impact the outer wall of the cylinder, so that the repeated repeated impact causes the cylinder liner surface to be sharply damaged.

 

In order to prevent cavitation, the current common method is to reduce the gap between the cylinder and the piston, thereby reducing the vibration of the cylinder liner; using a long piston skirt; increasing the cooling water flow rate, improving the water flow direction and the structure of the cooling system Increase the support stiffness of the cylinder liner; improve the material and process of the cylinder liner to improve its resistance to cavitation and so on.