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Boilers can be found on every type of a ship. A boiler is used to produce steam feed water. The main parts of a boiler are: a furnace where fuel is burnt to release its energy; a drum where steam and water can separate; downcomer tubes which join the steam and water drums and are used to circulate feed water between them; an economizer which is used to heat the feed water and an air heater which warms the combustion air before it enters the furnace.

TEXT B

MARINE BOILERS – A GENERAL OVERVIEW

Boilers are one of the most important items of equipment aboard ships. They are used for numerous purposes. Whether it is steam powered or has a diesel engine as the main form of propulsion, a ship without a boiler is really difficult to imagine.

A boiler is a machine with the simplest arrangement of the internal parts. The main job of a boiler is to make high pressure steam. The feed water supplied to the boiler drum utilizes the heat of the energy released by burning the fuel. This energy of burning fuel is stored in the form of the steam with high temperature and pressure. The fuel is burnt in a combustion chamber inside the boiler. To attain high efficiency and complete combustion, air is supplied to this combustion chamber through a separate arrangement. The heat generated in this combustion chamber is transferred to the water from the boiler drum through a large area, which enables the highest rate of energy transfer.

The process of steam generation starts when the feed water enters the steam drum through both internal tubes and the tubes that surround the furnace. The system of tubes that surrounds the furnace is known as water-wall or floor tubes. The feed water gets heated when passed through these tubes. In addition to this, there are large-bore downcomer tubes that pass outside of the furnace and are used to circulate water between the drums, to which the tubes are attached from outside of the furnace.

The steam produced in the steam drum is known as wet or saturated steam. This steam cannot be used directly as it contains moisture. To make this steam usable, it is first dried and heated with the help of a superheater located within the boiler. When all moister is removed, the superheated steam can be supplied to other systems.

To increase the efficiency of the boiler, the feed water that enters the boiler is pre-heated with the help of an economizer through which the feed water passes before entering the boiler. The exhaust gases of the boiler pass over an air heater, which heats up the combustion air entering the furnace. Thus, the energy of the exhaust gases does not go waste.

EXERCISES

1. Learn the following word combinations and their translation. Make up your own sentences with them.

1. to make high pressure steam	производить пар высокого давления
2. to utilize the heat of the energy	использовать тепло энергии
3. to attain high efficiency	достигать высокой производительности
4. to surround the furnace	окружать топку
5. to contain moisture	содержать влагу
6. to increase the efficiency of the boiler	увеличить КПД котла
7. to go waste	выходить впустую

2. Complete the sentences.

1.The main job of a boiler is ….

2. The feed water utilizes ….

3. The fuel is burnt in ….

4. The heat produced in the furnace is ….

5. Water-wall or floor tubes are the system of ….

6. Large-bore downcomer tubes are used to ….

7. A superheater is located ….

8. Before entering the boiler the feed water passes through …

9. An air heater heats up ….

TEXT C

A STEAM POWER PLANT

A steam power plant is used to propel a ship. It consists of a steam producing plant and a steam consuming unit. The steam power plant operates as follows: oil fuel is injected into the boiler furnace through burners which may vary in number in different types of boilers. The combustion of fuel generates heat radiated to the boiler tubes. This heat is absorbed by water and thus steam is formed. After that the heat is transmitted to the additional heating surfaces of the boiler.

To convert the heat energy of the steam into useful work steam is admitted to the turbine. The steam enters nozzles where the energy of steam is converted into the kinetic energy. The steam expands and when it leaves the nozzles the kinetic energy is converted into mechanical energy at the turbine moving blades.

In passing through the turbine the steam is reduced in temperature and pressure. The steam from the turbine passes to the condenser where it is changed into water.

The water is pumped into the steam-water drum and the cycle is repeated. The whole arrangement which includes a water-tube boiler and a steam turbine is known as a steam power plant and is installed in turbo-driven ships.

Vocabulary

use, v использовать

propel, v приводить в движение

steam producing plant паропроизводящая установка

steam consuming plant паропотребляющая установка

burner, n форсунка

vary, v изменяться

surface, n поверхность

moving blades движущиеся рабочие лопатки

turbo-driven ship турбоход

e x e r c I s e s

Дата добавления: 2015-03-29