**Abstract**

This chapter deals with the tribology of marine diesel engines. Several types of diesel engines have been installed and used in the engine room of marine ships. Some of them, used for propulsion, operate at low-speed in a two-stroke combustion process in conjunction with propellers. Four-stroke engines are used for power generation and operates at medium-speed. In general, two or more four-stroke engines, including spares, are installed in the large ships. Tribological problems are important issue in the respect of reliability in the marine diesel engines, and there are many tribological engine components including bearings, pistons, fuel injection pumps and rollers. Moreover, the marine engines have lubricant problems such as lacquering. Improvements to the tribological performance of marine engine components, and lubricants can provide reduced oil and fuel consumption, improved durability, increased engines power outputs and maintenance. Therefore, this chapter shows better designs and methods in order to improve the tribological problem in the marine diesel engines.

**Keywords:** marine diesel engine, medium-speed diesel engine, low-speed diesel engine; fuel injection pump, lacquering; bearing, condition monitoring

### **1. Introduction**

The marine diesel engine was first installed in the Selandia, which is oceangoing vessel, in 1912. According to statics, diesel engines used as a power source more than 95% in the ships of 2,000 tons or more [1]. Various types of engine used in the ship according to fuels such as diesel engine, gas engine and duel fuel engine. Among those marine engines, diesel engines have a large portion in marine engine market from the past to the present. Marine diesel engines burn refines but mostly residual fuels with a legislated maximum sulfur content between 0.0005% and 4.5% w/w sulfur. The intention is to reduce SOx exhaust gas emissions for environmental reasons [2]. There has been a steady decline in NOx emissions at an acceptable level due to the increasing number of rigorous exhaust legislations for marine diesel engines to minimize NOx emissions. Reduced NOx emission can also be achieved by selective catalyst reduction (SCR), which is the most widely used and established technology [3]. Although ship pollution rules of IMO (international maritime organization) strengthened like IMO Tier III, the demand for engine performance improvement is also increasing.

Marine diesel engine types are two-stroke cycle and four-stroke cycle. The two-stroke engines are engine that complete a power cycle with two strokes of the piston during only one crankshaft revolution, and operate with about 100 rpm.

On the other hand, the four-stroke engines are internal combustion engines in which the piston complete four separate strokes during two crankshaft revolutions, and work in the speeds of 250 to 850 rpm. In case of large ships such as container ship, the two-stroke engines commonly installed as propulsion and the four-stroke engines operated as generators. This is because the two-stroke engines have higher torque and superior power-to-weight ratio than the four-stroke engines. However, the four-stroke engines used as propulsion in relatively small ship such as passenger boats and ferries.

Distillate oil and residual oil are the two most common types of marine fuels. "Intermediate oil" is the third type of marine fuel that combines the first two main types. In a refinery, petroleum fractions of crude oil from distillate fuel are separated by a boiling process. Residual fuel, also called 'tar' or 'petroleum pitch', is a fraction of the fuel that does not boil. Unwanted substances, such as chemical waste, are found in this type of fuel. Fuel system components, fuel injection equipment, pistons, piston rings, and cylinder liners can be damaged by these undesirable materials [4].

Various problems arise in the process of increasing the size of an engines or improving its performance. The solution and improvement of tribological problems related to friction wear and lubrication is very important in terms of reliability in marine diesel engines. This chapter present researches on machine components of marine diesel engines, which have tribological problems such as wear, sticking and oil consumption.
