TASK 6. Give annotation of the text.

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TASK 7. Give a short summary of the text.

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TEXT 9

THERMAL ELECTRICAL PLANTS

Hydroelectric stations deliver power from great rivers, but still about 80 per cent of the required electric power is produced in thermal electrical plants. These plants burn coal, gas, peat or shale to make steam. 

To understand how the energy of fuel is converted into; electrical energy let us discuss the heat process and begin with the fuel.

Gas is delivered through gas pipelines. The coal (peat, shale) arrives in trains, and conveyors or cranes unload it for storage and bring it to the furnace. It is more effective to burn coal in the form of powder, therefore it is first crushed, pulverized and blown into furnaces. To attain complete combustion of the powder a large volume of air is needed, delivered by forced air fans, exhauster fans and smoke stacks. The steam boilers or steam generators supply the huge amount of high-pressure, high-temperature steam required to drive the high-power turbine-generators.

Air is compressed in an axialflow compressor from atmos-pheric pressure to a pressure which is usually between the limits of 75 and 120 ps The compressed air may then flow through a regenerator or heat exchanger in which the hot ex-haust gas from the turbine is utilized to increase the tempera-ture of the air, thereby recovering energy that would other-wise be lost to the atmosphere. Fuel is sprayed into the com-bustor in which it combines chemically with the oxygen in the air to produce a hot gas leaving the combustor at some temperature between 1200° and 1700° F. The pressure of the air decreases slightly between the compressor discharge and turbine inlet because of friction, but the increase in tem-perature in the regenerator and combustor results in more than doubling the volume. The hot gas then expands in the turbine in which it does enough work to drive the compres-sor as well as an electric generator or some other suitable machine. The exhaust gases leaving" the turbine are cooled in the regenerator before being discharged to the atmosphere.

Where space and weight limitations are critical or fuel is cheap, the regenerator may be omitted with a substantial decrease in efficiency. The turboprop engine' as applied to the airplane operates without a regenerator and with a geared propeller as the load. In the turbojet engine as applied to the airplane, the turbine develops only enough to drive the compressor and exhausts into a nozzle at a back pressure considerably in excess of atmospheric pressure. The rearward expansion of the exhaust gases from the nozzle at high velocity creates the thrust which propels the airplane.

The kinetic energy of its steam acts against the blades of the turbine and rotates its shaft joined to the generator shaft.

A centralized control desk with panels and many instruments and automatic control devices supervises and monitors the plant, with only a few operators.

PHRASES & WORD COMBINATIONS TO THE TEXT

1. to deliver - доставить, вручить

2. to require - требовать

3. peat - торф

4. shale - глинистый сланец

5. to convert - превращать, конвертировать

6. fuel -топливо, горючее

7. pipeline - трубопровод, нефтепровод

8. conveyor - конвейер

9. to unload - разгружать, выгружать; разряжать (оружие)

10. storage - хранение, склад, хранилище

11. furnace - печка, очаг, горн, тонко

12. powder - порошок, пудра, порох

13. to crush - давить, мять, уничтожать, толочь

14. to pulverize - растирать в порошок, распылять

15. to blow, blew, blown - дуть

16. to attain - достигать

17. complete - полный, законченный, совершенный

18. combustion - сгорание

19. fan - вентилятор, веер

20. exhauster - вытяжной вентилятор, эксгаузер, пылесос

21. smoke stacks - дымовые трубы, выхлопные трубы

22. to drive, drove, driven - управлять, править

23. to join - соединять(-ся), присоединять(-ся), вступать

24. to supervise - смотреть, наблюдать

25. to monitor - контролировать, управлять

26. forced - принудительный

27. forced air fans - принудительная воздушная вентиляция

EXERCISES

TASK 1. Answer the questions:

1.Where are hydroelectric stations located? _______________________________

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2.What stations produce about 80 per cent of the required electric power? _______

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3. What fuel do they work on? _________________________________________

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4. What kinds of fuel do you know? _____________________________________

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5. How is gas delivered? ______________________________________________

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6. How are solid fuels delivered? _______________________________________

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7. In what form is the solid fuel burnt? ___________________________________

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8. Why is a large volume of air needed for burning solid fuels? ________________

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9. What is used for this purpose? ________________________________________

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10. What are generators fed by? ________________________________________

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11. What does the kinetic energy of the steam do with the blades of the turbine?

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12.What does a centralized control desk do? ______________________________

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13.Why are there only a few operators at such electrical, plants? _______________

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TASK 2. Give Russian equivalents:

to deliver

to require

to convert

to load

to inload

to crush

to pulverize

to attain

to drive

to join

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to supervise

to monitor

to force

peat

shale

pipeline

storage

furnace

powder

combustion

fan

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______________________________________________________________ _______________________________

TASK 3. Translate into Russian:

optimum process

correct choice

interior part

wide application

power input

continuous operation

voltage transformer

initial conditions

moderate temperature

blast furnace

raw materials

heat treatment

current of air

high-power turbine-generator

high-pressure

waste pipes

limited energy

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______________________________

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mass production

forced air fans

exhauster fans

smoke stacks

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TASK 4. Fill the gaps: "to convert", "to crush", "to pulverize", "to burn", "to blow", "to unload", "to feed", "to supervise", "to bring", "to monitor".

1.Thermal electrical plants _______________solid fuels and gas.

2.The energy of solid fuels and gas is __________________ to electrical energy.

3.Solid fuels are ________________ by conveyors and cranes.

4.Solid fuels are ____________, ____________, and __________ to the furnace.

5.Generators are ___________ by the huge amount of high pressure, high temperature steam.

6.A centralized control desk _________________and ______________ the plant.

7.Electrical energy is __________________ to various parts of the nearest region.

TASK 5. Choose the correct variants:

1.Thermal electrical plants produce _____________________________________

a)a limited volume of electrical energy;

b)a large volume of electical energy.

2.Thermal electrical plants are _________________________________________

a)the main producer of electrical energy;

b)not the main producer of electrical energy.

3.Solid fuels are more effective in ______________________________________

a)the form of powder;

b)not in the form of powder.

4. Generators are fed by ______________________________________________

a) gas;

b) high temperature steam.

5. The blades of the turbine rotate ______________________________________

a)the generator shaft;

b)its shaft.

TASK 6. Give Russian explanations to the next terms:

wattmeter -

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galvanometer -

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Ohmmeter –

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1.An instrument for measuring the strength of electric current.

2.An instrument connected to an electric circuit and measuring the power delivered to the circuit in watts.

3.An instrument for measuring resistance in ohms.

 

electric current –

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direct current -

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alternating current –

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continuous current –

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1.A current which always flows in one and the same direction.

2.A current which periodically alternates or reverses in direction.

3.A flow of passage of elictricity along an electric circuit, usually measured in amperes.

 

circuit breaker-

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controller –

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control power switch -

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line switch –

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1.A device for opening or closing a circuit, either by hand or automatically, in the case of an overload.

2.A device for controlling an electric machine or a circuit (a controller device).

 

voltage balance relay –

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emergency direct current relay –

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current balance relay –

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impedance relay –

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1.A device used to interrupt a direct-current power circuit under emergency conditions.

2.A relay which operates on a difference of voltage between two circuits.