1. Crosshead Engine: In crosshead engines, which are typically larger marine diesel engines, the piston and the crankshaft are connected by a crosshead. The crosshead is located outside of the cylinder, allowing for easy access to the cylinder liner. Lubrication is provided by a forced-feed system that delivers oil directly to the piston pin and the crosshead bearing. The oil then flows down the cylinder liner, lubricating the piston rings and the cylinder wall.
2. Crankcase Scavenging: In trunk-piston marine diesel engines, which are smaller engines commonly used in smaller boats, crankcase scavenging is used for cylinder lubrication. In this method, the crankcase is sealed and used to create a vacuum that draws in air and oil mist. This mixture then travels through ports in the cylinder walls, lubricating the piston rings and cylinder liner as the piston moves up and down.
3. Direct Injection: Direct injection engines have fuel injectors that spray fuel directly into the cylinder. In these engines, a lubricating oil is blended with the fuel. This oil-in-fuel lubrication provides a layer of protection between the piston rings and the cylinder liner.
4. Oil Injection: Some two-stroke marine diesel engines use an oil injection system specifically for cylinder lubrication. In this method, a separate pump or injector is used to inject a metered amount of lubricating oil directly into the cylinder at a predetermined point in the engine cycle, ensuring the oil reaches the critical areas that require lubrication.
It's important to follow the manufacturer's recommendations and specifications for the type and frequency of lubrication required for the specific engine model and operating conditions. Proper lubrication is essential for the longevity and reliability of the two-stroke marine diesel engine.
