Marine diesel engine parts Diesel engines used on ships. It works as follows:

A stream of fresh air is drawn into or pumped into the engine cylinders and then compressed to a very high pressure by a moving piston. When the air is compressed, its temperature rises so that it can ignite the fine mist of fuel injected into the cylinder. The combustion of fuel adds more heat to the charged air, causing expansion and forcing the generator piston to do work on the crankshaft, which in turn drives the propeller of the ship through the other shafts.

The operation between two fuel injections is called a working cycle. In a four-stroke diesel engine, this cycle needs to be completed by four different strokes of the piston, namely intake, compression, expansion and exhaust. If we combine intake and exhaust with compression and expansion, a four-stroke engine becomes a two-stroke generator.

The two-stroke cycle begins when the piston rises from the bottom of its stroke (both bottom dead center), at which time the air intake on the side of the cylinder is open. At this time, the exhaust valve is also opened, fresh air is filled into the cylinder, and the residual exhaust gas from the previous stroke is blown out through the opened exhaust valve. The valve blows out.

When the piston runs up to about one fifth of its stroke in the morning, it closes the air inlet and the exhaust valve closes, so the temperature and pressure rise to very high values.

When the piston reaches the top of its stroke (that is, top dead center), the fuel valve injects a fine mist of fuel into the high-temperature air in the cylinder. The fuel immediately burns, and the heat causes the pressure to rise quickly. In this way, the expanding gas forces the piston to move downward during the power stroke.

When the piston moves down a little over half of the stroke, the exhaust valve opens, and high-temperature gas starts to flow out through the exhaust valve due to its own pressure, which is assisted by the fresh air entering through the air inlet. The air intake opens as the piston descends further. Then another cycle began.

In a two-stroke engine, the crankshaft makes one power stroke for one revolution, while a four-stroke engine requires two crankshaft revolutions to make one power stroke. This is why two-stroke engines can do about twice as many strokes as the same size The reason for the work done by the engine. In current actual use, with the same cylinder bore and the same speed, the power output of the two-stroke engine is about 80% higher than that of the four-stroke engine. This increase in engine power has made two-stroke generators widely used as main engines of large ships.