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Marine Engineering

The shipping industry has become an essential part of the world economy, with out it many people living in isolation would not be able to receive essential products. At the hart of the marine industry is marine engineering, this covers everything from the way the ship is designed to the various systems and equipment that allow the ship to operate.

Diesel Engines
On a ship the main engine is the beating hart of the ship and often times the largest piece of equipment in the engine room. The main job of the engine is to provide power to the propeller which intern gives the ship propulsion. In other words, the ship would not be able to maneuver without the main engine. Although many different kinds of engines have been developed over the years the most common today would have to be the diesel engine.

Although there are many types of diesel engines all operate on the same principals. Fuel is injected into a cylinder which uses high pressure in order to ignite the fuel. This type of ignition system is called an internal combustion engine. The energy that is created by igniting the pressurized fuel air mixtures is exerted on the piston head forcing it down, this motion is transmitted from a reciprocating motion into a rotational motion by the crankshaft. There are three different classifications of a diesel engine: slow, medium, and high speed. This refers to the revolutions per minute (rpm) that the engine is able to put out. Slow speed engines range from 0-300 rpm, medium speed 300-800 rpm, and high-speed engines are 800 rpm and above.

In the maritime industry there are two distinct types of engines, the two stroke and the four strokes. On a ship both require the same five supporting systems in order to operate efficiently; lubrication, cooling, exhaust, fuel injection, and air intake The largest difference between the tow engines would have to be the cycles of each engine. While the four stroke takes two revolutions in order to complete one cycle the two strokes only takes one stroke. Another key difference between the two would be that a two stoke engine does not use an intake valve, instead it has a scavenging port. The more common one of the two would have to be a four-stroke engine due to its better fuel efficiency across a wider range of rpm. One advantage of a two stoke engine is that it is considered simpler due to the fact that it has fewer moving parts, this also allows the two-stroke engine to be smaller and more compact.

prevention
Cavitation occurs when a change in pressure is found in a liquid which will cause the liquid to turn into a vapor. This can be found on propellers and pumps that are pumping liquids. Cavitation will lead to premature erosion of the propeller and on the impeller of a centrifugal pump. One of the reasons that cavitation is so dangerous is that if this occurs in a fuel line there is a good chance that it could explode. One way to prevent this in a fuel system is to use positive displacement pumps instead of centrifugal pumps. When it comes to preventing cavitation on a propeller you can do two things, slow down the speed of the propeller or increase the number of props.