The Countermeasures for honeycomb pits on the outer wall of diesel engine cylinder liner are as follows:
In the parts of the outer and water contact of the wet cylinder liner, sometimes there will be a number of honeycomb pits of different sizes. In serious cases, even through the leakage of water. This phenomenon is called cavitation.
Taking 6135 diesel engine as an example, it was found in use. The cavitation damage was not paid attention to before. It was mainly because the cylinder liner was worn out before the cylinder liner was worn out. With the progress of science and technology, the abrasion resistance of the inner wall of the cylinder liner was greatly improved. On the other hand, the supercharging and high speed performance of the exhaust gas were greatly improved. As a result, the cavitation damage of cylinder liner has also aroused people's attention. Practice has proved that the cavitation site of cylinder sleeve is mostly produced in the narrow place of the cylinder and cylinder liner on the side of the camshaft, and in the middle and lower parts of the cylinder liner and the upper edge of the waterproof ring, many pits and trench marks of different diameters of 1~4mm are often produced. The cylinder sleeve will perforate the scrap.
One of the important reasons for this failure is the high frequency vibration caused by alternating pressure of cooling water. Specifically, the cavitation area can not be fully cooled so that the local overheating is produced in the narrow area of the water jacket. The gap between the piston and the cylinder sleeve is too large, the flow velocity is too low and the basic large cooling water is used, all of which will accelerate the cavitation erosion. In addition, the strong vibration of the cylinder sleeve is one of the main factors that cause cavitation. When the diesel engine works, the piston moves up and down. When the piston reaches the stop point, the piston moves from one side of the cylinder sleeve to the opposite side because of the direction of the side thrust. The cylinder liner is vibrate at a high speed, so that the cylinder sleeve will be vibrate at high frequency. When the clearance between the piston and the cylinder liner and the lateral thrust are greater, the speed and energy of the piston hitting the cylinder liner are greater, so the vibration of the cylinder liner is greater.
When the cylinder liner vibrates, the air bubbles are produced between the surface of the cylinder liner and its adjacent waters. The bubbles occur frequently and disappear with the high frequency vibration of the cylinder sleeve. At the moment of the collapse of the air bubbles, high temperature and high pressure wave are produced, which repeatedly acts on the outer wall of the cylinder sleeve made of cast iron, thus producing cavitation pit.
In order to reduce the vibration frequency and amplitude of cylinder liner, it is usually appropriate to reduce the gap between the cylinder liner and the upper and lower seat holes, and to minimize the clearance of the piston and cylinder sleeve to achieve its purpose under the condition of normal operation. In addition, the temperature and cleanliness of the cooling water of the diesel engine and the hole of the cylinder liner Corrosion also has a certain effect. The reason is that when the diesel engine is in a long time below 60 C, the diesel engine ignition is lengthened and the pressure increase rate increases, which causes the cylinder liner vibration to intensify. With a large amount of impurities, water is easily separated and is conducive to the formation of bubbles. Thus, the cavitation erosion of cylinder liner will also be accelerated. Practice has proved that the use of good quality long effect antifreeze as coolant can often effectively prevent cavitation.
The other fact is that if the application is unsuitable, the dry cylinder sleeve will also have a cavitation phenomenon. For the Japanese Nissan PD6 diesel engine for engineering machinery, the dry cylinder liner wall thickness is 2.5mm, the cylinder sleeve and the cylinder hole machining precision is high, and the cylinder liner and the cylinder hole are matched with the "O" and "1" two groups of processing dimensions respectively. In order to ensure the suitable interference fit, only the "0" group gas cylinder body and the "0" or "1" cylinder liner, and the "L" group cylinder body and the "1" group cylinder sleeve are matched. In the maintenance, the "1" cylinder body is cooperated with the "O" cylinder sleeve to form a transition and matching (+0.02~0.Olmm), which will lead to strong high-frequency vibration, so that the outer surface of the cylinder sleeve is presented. A dense honeycomb pit.
Therefore, when maintenance is carried out, it is necessary to strengthen the inspection of the site where the cavitation erosion is easy to occur. It is found that the cavitation phenomenon can be used to extend the cylinder sleeve 900 and use it to prolong the service life. In addition, a layer of epoxy phenolic resin is applied to the outer wall of the cylinder sleeve, which also has good effect on preventing cavitation.
