DIFFERENT TYPES OF MARINE ENGINE

Date: 2015-10-07; view: 486.

Grammar Pattern to Text А

The larger the propeller (is) the slower it turns.

Чем больше винт, тем медленнее он проворачивается

Прочтите текст А, не пользуясь словарем. Ответьте на следующие вопросы.

1. What kind of diesel engine (slow, medium or high speed) is used (installed) on large merchant vessels in most cases today?

2. What are its advantages?

TEXT A

(1) 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.

(2) The diesel engine is a form of internal combustion engine. Its power is expressed as brake horsepower (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 propeller¹, 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 1o the propeller by gearing. They ace cheaper than slow-speed diesel engines, and their smaller size and weight can result in a smaller cheaper ship.

(3) In steam turbines high pressure steam is directed into a series of blades or vanes attached to a shaft, causing it to rotate². 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. Turbines are often used in container ships.

(4) Gas turbines differ, from steam turbines if that gas rather than steam³ 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. ,

(5) 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.

Notes:

¹although higher power could be produced by... this would reduce the efficiency of the propeller - хотя и можно было бы развивать большую мощность, это бы уменьшило КПД винта.

² causing it to rotate - заставляя его вращаться/вызывая его вращение.

³gas rather than steam - газ, а не пар.