The internal combustion engine, a marvel of modern engineering, relies on a synchronized work of numerous parts. At the center of this action lies the cylinder block and its companion, the cylinder liner.
These components play a critical role in converting fuel and air into the power that drives our vehicles and countless machines. This article explains the details of cylinder blocks and liners, exploring their functions, the reasons behind their design choices, and the different types of liners employed in various engines.
By understanding these key elements, we gain a deeper understanding of the workings of the internal combustion engine.
What is a Cylinder Block?
The primary engine parts are fit inside a block-like structure known as a cylinder block. To maintain efficiency these parts are manufactured with extreme precision, even the cylinder bores. To hold the released pressure by burning fuels these blocks are very thick.
To seal the flammable gas from escaping the cylinder base and rings are fit tightly to prevent any accident. The cylinder is required to maintain its shape by any chance the shape changes to oval it will not be efficient to seal the gases and they will start leaking.
If the gas leaks through the cylinder such condition is known as blow-by. This reduces the engine’s working efficiency.
The wall’s finish of the cylinder has an impact on the ring seal. The cylinder walls have been machined to an extremely smooth surface. Small grooves created by special grinding stones in the cylinder walls catch oil.
The piston rings and piston skirts are kept lubricated by these grooves. Because cast iron and grey iron were simple to manufacture, they were used to make the majority of cylinder blocks in the past.
When compared to cast iron cylinder walls, aluminium pistons wear extremely well. Engine blocks are now produced from lightweight aluminum due to iron’s primary drawback of weight.
The aluminum block has less weight compared to cast iron. Wear on an aluminum piston skin that comes into contact with an aluminum cylinder wall happens fast. Most aluminum cylinder blocks use steel or ductile iron cylinder bore liners.
What is a cylinder liner?
A hollow cylindrical structure fitted within the engine block’s cylinder bore is called a cylinder liner, also known as a cylinder sleeve. Due to their ability to prevent direct contact between the engine block and piston, these thin metallic structures are essential to internal combustion engines.
Two primary criteria determine how long a cylinder lasts between re-bores:
(i) Wear and tear, and
(ii) The corrosion.
The efficacy of the air and oil filters as well as the state of the atmosphere affect abrasion. Dusty ambient air is more damaging because it causes greater abrasion in the cylinder.
Fuel and air combine to generate corrosive combustion products, which are what cause the cylinder to corrode.
Because the cylinder walls are covered in moisture that contains acid, corrosion is exacerbated at low cylinder temperatures. The cylinder has a lengthy lifespan when separate barrels or sleeves—also referred to as cylinder liners—are used.
These cylinder liners are installed in the cylinder block and are composed of high-quality material. These are replaceable and in the case of any worn out or damaged these can be easily changed.
If the cylinder can withstand the abrasion well, it will lubricate the area between the walls and the piston rings in a much better way
Types of Liners
There are three types of cylinder liners available in the market. These are categorized based on the cooling method used to cool them.
The most typical kind of cylinder liner is the dry kind. Because it operates at high temperatures and pressures, high-grade materials like cast iron and ceramic-nickel plating are required.
Cast iron and ceramic-nickel compounds make up the majority of the material composition of dry liners, giving them certain properties that wet liners cannot match.
Compared to a cylinder block with wet liner liners, one with dry liners is more durable. In comparison to wet liners, dry liners are often thinner.
Dry liners work to shield the piston from abrasion and contaminants, there is no direct contact between the dry linder and coolents. The dry liner in the cylinder block fits exactly up against the cooling jacket wall.
Advantages of Using Dry Cylinder Liner
One benefit of using a dry cylinder liner is that it is simple to change and does not require special attention from a water jacket. Nearly every type of engine may use dry liners.
The disadvantage of Using Dry Cylinder Liner
The drawback of dry cylinder liners is the inefficiency of heat dissipation and the difficulty of manufacturing the cylinder block in which it is installed.
Wet Type Cylinder Liner
The same material is used to make dry-type cylinder liners and wet-type cylinder liners. To preserve the piston, there is direct contact between the wet cylinder liner and the coolant.
Wet liners perform better than dry liners in terms of cooling and heat dissipation. Wet Liners may have built-in cooling channels or a cooling water gap between the engine block and liner.
In the wet liners where the cooling passageway is absent, it forms a two-jacket system one jacket is formed by the liner and another by the block. To prevent coolant from leaking into the combustion area, or oil pan sump, a static seal has to be installed at the crankshaft and combustion ends of the cylinders.
Advantages of Wet Type Cylinder Liner
Wet-type liners have the advantages of being very simple to build, more effective cooling, and less longitudinal stress as a result of the liner’s thermal expansion.
Disadvantages of Wet Type Cylinder Liner
Wet-type liners have the drawbacks of being difficult to change and perhaps having issues with leaks.
Air Cooled or Finned Cylinder Liner
In order to provide long life and effective cooling, Air Cooled Cylinder Liners are created using a unique “Shell Moulding Process” that features wear-resisting, close-grained iron casting.
Air Cooled Liners are made especially for engines that use air cooling, as the name implies. Cars are the most typical use for air-cooled liners. It functions similarly to a dry cylinder liner, however in this case, air serves as the cooling medium.
With the aid of its fins, which are placed on its surface, the Air Cooled Liner dissipates heat by forced convection. The Fin’s material often has a high heat conductivity.
Advantages of an Air Cooled/Finned type Cylinder Liner
The benefits include excellent heat dissipation and corrosion resistance.
Advantages of an Air Cooled/Finned type Cylinder Liner
The fact that an air-cooled cylinder liner is made to support an air-cooled engine and cannot be put in a mechanism that uses coolant is a drawback of this type of liner.
Conclusion
The cylinder block and cylinder liner form a vital partnership within the engine, ensuring smooth operation, efficient power generation, and extended engine life.
The cylinder block provides the foundation, while the liner offers a wear-resistant surface and facilitates precise tolerances.
The various liner types cater to specific engine requirements, optimizing performance and durability. Understanding this dynamic duo sheds light on the workings of the internal combustion engine, a human-generated wonder for the world.