What Is Cylinder Liner?
In an engine, a cylinder wall is exposed to high temperature and high pressure, with pistons and pistons sliding rings at high speed. In particular, since long service life is required for engines of trucks and buses, cast-iron cylinders that have excellent wear-resistant properties are used only for cylinder parts. In addition, with the recent trend of lighter engines, materials for engine blocks are shifting from cast iron to aluminum alloys.
However, as sliding surfaces for the inner cylinder, the straight sliding motion of aluminum alloys has the drawbacks of deformation during operation and wear resistance. For this reason, cast iron cylinder liners are used in most cases.
The cylinder liners are sleeves in which the pistons of an engine interact. The life of a cylinder between its re-holes depends on two main factors: Abrasion and Corrosion. The friction depends on the atmospheric conditions and the efficiency of the air filter & oil filter. Dusty atmospherics air is more harmful as it increases friction in the cylinder.
Cylinder corrosion is caused by corrosive products of combustion, which are formed after burning fuel with air. Corrosion intensifies at low cylinder temperatures due to acid-bearing moisture on the cylinder walls. The use of separate barrels or sleeves, known as cylinder liners, gives the cylinder a longer life. These cylinder liners are made of superior materials and fit into the cylinder block.
The liners are removable and can be replaced if worn or worn out. The cylinder liner must have good wear resistance and the ability to retain oil to lubricate the surface between the walls and the piston rings.
Material for Cylinder Liner:
For cylinder liners, nickel-chromium iron has been popularly used. The nickel-chromium iron used includes;
- Carbon 3.5%;
- Manganese 0.6%;
- Phosphorus 1.5%;
- Sulfur 0.05%;
- Silicone 2%;
- Nickel 2%; and
- Chromium 0.7%.
To increase wear resistance, liners are hardened by heating to 855°C-865°C for 30 to 40 minutes and then quenched in oil. This type of heat treatment increases the life of the liner by three times compared to gray iron or cast iron cylinders.
The Function of Cylinder Liner:
Cylinder liners are the central working part of a reciprocal engine or pump, the space in which a piston travels. The problem of cylinder wear is substantial and has been solved by the use of cylinder liners. Cylinder liner is in the form of barrels made of special alloy iron-containing silicon, manganese, nickel, and chromium. They are centrifugal cast. Cylinder liners are now installed on the engines of cars and commercial vehicles. These liners are of oil hardening type and provide a much longer life for the engine.
#1. Formation of Sliding Surface
The cylinder liner, acting as the inner wall of cylinders, forms a sliding surface for the pistons rings while retaining the lubricant within. The most important functions of cylinder liners are the excellent characteristic of the sliding surface and these essential points.
- High Anti-Galling Properties
- Less wear on the cylinder liner itself
- Less wear on the partner piston ring
- Low consumption of lubricants
#2. Heat Transfer
The cylinder liner receives the combustion heat through the piston and piston rings & transmits the heat to the coolant.
#3. Compression Gas Sealing
The cylinder liner prevents compressed gas and combustion gas from escaping. All that is needed is a cylinder liner that is difficult to replace with the high pressure and high temperature in the cylinder. In an engine, a cylinder wall is exposed to high temperature and high pressure, with pistons and pistons sliding rings at high speed.
In particular, since long service life is required for engines of trucks and buses, cast-iron cylinders that have excellent wear-resistant properties are used only for cylinder parts. In addition, with the recent trend of lighter engines, materials for engine blocks are shifting from cast iron to aluminum alloys.
However, as the sliding surfaces for inner cylinders, the straight sliding motion of aluminum alloys has the drawbacks of deformation during operation and wear resistance. For this reason, cast iron cylinder liners are used in most cases.
Types of Cylinder Liner:
#1. Dry Liners
The dry liners are made in the shape of the barrel with a flange on top. The flange holds the liner in position in the cylinder block. The liner fits snugly into the cylinder. Correct contact of the liner with the cylinder block is essential for effective cooling of the liner.
In addition, gas pressure, piston thrust, and impact loading during combustion are opposed by the combined thickness of the liner and cylinder. Therefore, dry liners are thinner, with a wall thickness varying from 1.5 mm to 3 mm, and are mostly used to repair worn-out liners. Dry liners are not in directs contact with cold water.
#2. Wet Liner
Wet liners are so-called because cold water comes into contact with the liner. This liner features a flange at the top, which fits into the groove made in the cylinder block. To prevent leakage of cold water into the crankcase, the lower end of the wet liner is sealed with the help of a sealing ring or packing ring. As the wet liner has to withstand the pressure, thrust, and impact loading of the gas, the wall thickness of the liners is increased and made to be greater than that of the dry liner.
Generally, the wall thickness of wet liner ranges from 3mm to 6mm. The exterior of the liner is coated with aluminum to protect it from corrosion. Wet liners are cooled better than dry liners. When it gets worn or worn out, it can be easily removed.
Comparison of Dry and Wet Liners:
The wet liner can be easily replaced, while the dry liner requires special equipment as it is tight-fitted to the cylinder block. A wet liner is cooled precisely because it comes into direct contact with cold water, whereas a dry liner does not come into direct contact with cold water. Therefore, the working temperature of the dry liner is higher than that of the wet liner.
A wet liner requires leak-proof joints so that cold water does not leak into the crankcase, whereas a dry liner has no such requirement. A wet liner does not require precise finishing on the outside, whereas a dry liner requires precise finishing. Finishing can be accomplished in a wet liner prior to assembly, while dry liners require finishing after assembly.