Text 2. Different types of marine engine

There are four main types of marine engine: the diesel engine, the steam turbine, the gas turbine, and the marine nuclear plant. Each type of engine has its

own particular application.

The diesel engine is a form of internal combustion engine. Its power is expressed as break horse power (bhp). This is the power put out by the engine. Effective horsepower is the power developed by the piston in the cylinder, but some of this is lost by friction within the engine. The power is now expressed in kilowatts. Large diesel engines, which have cylinder nearly 900 mm in diameter, turn at the relatively slow speed of about 145 rpm and less. They are known as slow-speed diesel engines. They can be connected directly to the propeller without gearing. Although higher power could be produced by higher revolutions, this would reduce the efficiency of the propeller, because the propeller is more efficient the larger it is and the slower it turns. More and more of the larger merchant vessels are being powered by medium-speed diesel engines. These operate between 150 and 450 rpm, therefore they are connected to the propeller by gearing. They are cheaper than slow-speed diesel engines, and their smaller size and weight can

result in a smaller cheaper ship.

In steam turbines high pressure steam is directed into a series of blades or vanes attached to a shaft, causing its to rotate. This rotary motion is transferred to the propeller shaft by gears. Steam is produced by boiling water in a boiler, which is fired by oil. Recent developments in steam turbines which have reduced fuel

consumption and raised power output have made them more attractive as an

alternative to diesel power in ships.

Gas turbines differ from steam turbines if that gas rather than steam is used

to turn a shaft. These have also become more suitable for use in ships. A gas

turbine engine is very light and easily removed for maintenance. It is also suitable

for complete automation.

Nuclear power in ship has mainly been confined to icebreakers. A nuclear-powered ship differs from a conventional turbine ship in that it uses the energy released by the decay ( распад) of radioactive fuel to generate steam. The steam is used to turn a shaft via a turbine in the conventional way.

Text 3. From the Steam Engine to the Diesel

Development of the internal combustion engine of which the Diesel constitutes a particular type began in the second half of the 19th century.

The first Diesel engine was built in Germany in 1897 under the direction of Rodolphe Diesel himself. But it was only after the First World war that this engine truly left the experimental.stage thanks to the availability of a mechanical fuel injection system.

The first Diesel locomotive appeared in the USA in 1925. Then beginning in the 1930, railcars engines were put into service in Europe. In the USA Diesels began to be put into general use in the form of medium- power locomotives in 1942 during the Second World War. Their use expanded rapidly in the following years.

From 1950, introduction of powerful Diesel engines made it possible for Diesel locomotives to equal the performance of the electrically powered engines. First the French Railways were equipped with a high number of Diesel engines, but then the density of the rail network and of rail traffic made electrification the preferable choice and it was only for marine industrial and trucking application that Diesels enjoyed extensive development.

Text 4. The Transformation of Potential Energy into Mechanical Energy

The principle of all engines consists in transforming the potential energy of a fuel into mechanical energy, first it is necessary to produce heat, which is then transformed into work.

In almost all current applications, the production of heat is obtained by means of the chemical reaction of oxidation occurring between a hydrocarbon (or other fuel) and an oxidizer which supplies oxygen. The oxidizer is most often air which contains one-fifth oxygen by volume. The products of combustion are: Carbon dioxide

Water, if the fuel burnt contains hydrogen A great deal of heat, which raises the temperature of the gases produced, causing them to expand. The reaction always occurs between gases. If the fuel is not in gaseous form, it is necessary to make it gaseous. If after combustion of all the fuel there is oxygen left over, there is, as one says, an excess of air, meaning the fuel was poor in fuel. If on the other hand, there is unburnt fuel remaining and no oxygen, the mixture is said to be too rich.

The expansion of the gases heated by combustion produces "work" or mechanical energy.