What are the functions of a cylinder liner? What are the two types of cylinder liners?

The function of the cylinder liner

　　1. Together with the cylinder head and piston, it constitutes the working space of the cylinder;

　　2. The cylinder liner of a cylindrical piston diesel engine bears the lateral thrust of the piston and becomes the guide for the reciprocating motion of the piston;

　　3. It transfers the heat from the piston assembly and itself to the cooling water, keeping the working temperature appropriate;

　　4. The cylinder liner of a two-stroke diesel engine has air ports, which are opened and closed by the piston to achieve gas distribution. What materials are cylinder liners made of? Cylinder liners are made of ductile iron and alloy cast iron. The material of the cylinder liner must have sufficient mechanical strength and heat resistance, and must also have good wear resistance, corrosion resistance, oil retention and lubricity.

What are the two types of cylinder liners?

　　Cylinder liners are divided into dry-type cylinder liners and wet-type cylinder liners. The distinction between the two is mainly based on whether they are in contact with the coolant.

　　1. Dry-type cylinder liner The characteristic of a dry-type cylinder liner is that its outer surface is not in contact with the coolant. In order to obtain sufficient actual contact area with the cylinder block to ensure heat dissipation and the positioning of the liner, the outer surface of the dry-type cylinder liner and the inner surface of the cylinder bore that it mates with have high machining accuracy, and generally use interference fit. The dry-type cylinder liner wall is thin, generally only 1~3mm. Dry-type cylinder liners are often used in gasoline engines, and some low-power diesel engines also use dry-type cylinder liners.

　　Advantages: Large body rigidity, small cylinder center distance, small body mass, simple processing technology.

　　Disadvantages: Poor heat dissipation, uneven temperature distribution, inconvenient repair, and easy local deformation.

　　2. Wet-type cylinder liner The characteristic of a wet-type cylinder liner is that its outer surface is directly in contact with the coolant. In addition, it has a thicker wall than a dry-type cylinder liner. The radial positioning of the wet-type cylinder liner generally relies on two protruding rings at the top and bottom, which are clearance-fitted with the cylinder block. The axial positioning is achieved by using the lower plane of the upper flange. The lower part of the cylinder liner is sealed by 1 to 3 heat-resistant and oil-resistant rubber sealing rings. The sealing methods include expansion sealing and pressure sealing.

　　Advantages: There is no sealed water jacket on the body, easy to cast, good heat transfer, relatively uniform temperature distribution, and the wall thickness is generally 5~8mm. Importantly, during repair, the cylinder liner can be replaced without removing the engine from the vehicle, making maintenance convenient. Wet-type cylinder liners are generally used in diesel engines.

　　Disadvantages: Poor body rigidity and easy water leakage.