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Supply the proper preposition
1. Exhaust gas heat exchanger is mounted … the main engine uptake.
2. The exhaust gases are sent to the funnel … lower temperatures.
3. The exhaust gas boiler is equipped … an economizer and a superheater.
4. Thermal energy contained in the exhaust gases of diesel engines is superior … 30% of the total heating value … the fuel.
5. The temperatures of the exhaust gases vary … 270°C … 320°C for slow two- stroke engines.
6. This residual energy is recovered … using exhaust gas boilers.
UNIT 3
TEXT A
WATER-TUBE BOILER DESIGN
One of the most commonly used types of marine boilers is a water-tube boiler. In the water-tube boiler the gases pass around a number of small diameter tubes through which steam-water mixture circulates.
In a modern water-tube boiler burners are located in front of the furnace.
The furnace is the place where air and fuel are mixed for the combustion that heats the water in the drums, tubes and headers. It is lined on the floor and walls with refractory material which prevents the heat loss due to radiation.
The furnace is surrounded on all sides by tubes. These tubes are connected either to upper and lower headers or a lower header and the steam drum.
Between the steam drum and the smaller water drum below, large numbers of smaller-diameter generating tubes are fitted. They provide the main heat transfer surfaces for steam generation. Large-bore pipes or downcomers are fitted between the steam and water drum to ensure good natural circulation of the water.
Superheaters are essentially a bank of tubes used to heat the steam above the saturation temperature. Superheater tubing is used to further cool the gases; as gases are cooled, the steam is superheated.
Economizers are heat exchangers which are fitted in a boiler to increase the efficiency of the boiler. This is done by extracting the heat from the gases and using it to heat the feed water entering the boiler.
Air heaters are used to heat combustion air and to recover more of the heat energy from the exhaust gases before they are sent to the stack.
There are two types of water-tube boilers - main boilers and auxiliary boilers.
The circulation in water-tube boilers is either natural or forced.
According to the pressure they are classed as low, intermediate and high pressure boilers. The boilers generating steam under the pressure up to 15 atm. are called low pressure boilers, up to 28 atm. intermediate pressure boilers, and those generating steam under the pressure higher than 28 atm. may be called high pressure marine water-tube boilers.
As to more detailed classification of water-tube boilers they may be classed:
а) according to the number of drums as single-drum, two-drum and three-drum boilers;
b) according to the tube inclination as horizontal – those having tube inclination up to 30°, and vertical – with tube inclination of 45-90°;
c) according to the superheater location as horizontal and vertical;
d) according to the arrangement of gas flow as single-flow and double flow.
Vocabulary
mixture, n смесь
front of the boiler фронт (передняя часть) котла
header, n коллектор
line (with), v облицовывать; футеровать; выкладывать
floor, n под (топки)
refractory, adj огнеупорный; жаростойкий
due to radiation из-за излучения
generating tubes водогрейные (испарительные) трубы котла
provide, v обеспечивать
heat transfer surface теплопередающая поверхность
steam generation парообразование
large-bore pipes трубы с большим (внутренним) диаметром
superheater, n пароперегреватель
bank of tubes пучок труб
saturation temperature температура насыщения
economizer, n экономайзер
heat exchanger теплообменник
efficiency, n производительность; КПД
extract, v извлекать
recover, v утилизировать
stack, n дымовая труба
intermediate pressure среднее (промежуточное) давление
single-drum однобарабанный
inclination, n наклон
arrangement of gas flow способ течения газа
single-flow однопроточный (одноходовой)
E X E R C I S E S
1. Give English equivalents:
Наиболее распространенный тип; пароводяная смесь; трубы маленького диаметра; циркулировать по трубам; смешивать; предотвращать; потеря тепла; окружать; соединять; естественная циркуляция; воздухоподогреватель, выхлопные газы, котел низкого давления, котел высокого давления, до 15 атмосфер, свыше 28 атмосфер, двухпроточный.
2. Answer the questions according to the models:
| Model A. Does the boiling occur in the economizer? No, it doesn’t. Do the gases pass from the furnace to the stack? Yes, they do. |
1. Do the gases pass through a number of tubes in the water-tube boiler?
2. Does steam-water mixture circulate through tubes in the water-tube boiler?
3. Does the combustion heat the water only in the drums?
4. Do downcomers provide good natural circulation of the water?
5. Do superheaters heat the steam below the saturation temperature?
6. Does a horizontal water-tube boiler have an inclination more than 45º?
| Model B. Is superheater tubing used to heat the gases? No, it isn’t. Are burners located in front of the furnace? Yes, they are. |
1. Is the furnace surrounded on all sides by the tubes?
2. Is superheater tubing used to heat the gases?
3. Are the gases cooled in the economizer?
4. Is the circulation in the water-tube boiler only natural?
5. Are air heaters provided to heat combustion air?
6. Are the exhaust gases sent to the stack?
Ask for details:
| Model C. Burners are located in the boiler front. Where are the burners located? |
1. Heat energy is contained in the steam.
2. The heated water is fed to the boiler.
3. Air and fuel are mixed in the furnace.
4. Downcomers are located between the steam and water drums.
5. The furnace is lined with refractory material on the floor and walls.
6. Generating tubes are fitted between the steam and water drums.
3. Match the type of the boiler with its principle of classification:
Boilers may be classified into:
single-drum, two-drum and three-drum boilers by the pressure
main and auxiliary boilers by the number of drums
vertical and horizontal boilers by the tube inclination
single-flow and double flow boilers by their purpose
natural and forces circulation boilers by the superheater location
vertical and horizontal boilers by the arrangement of gas flow
low, intermediate and high pressure boilers by the principle of water and
steam mixture motion.
4. Self-assessment questions:
1. Which is one of the most widely used types of marine boilers?
2. Where do the gases pass in the water-tube boiler?
3. What does the steam-water mixture circulate through?
4. Where are burners installed in a modern water-tube boiler?
5. What kind of a place is the furnace?
6. What is the furnace lined with?
7. What is the function of superheater tubing?
8. What are air heaters used for?
9. What is the boiler classification according to the pressure?
10. How are water-tube boilers classed according to the number of drums?
11. What do we call boilers with tube inclination of 45-90°?
12. How can the superheater be located in the boiler?
13. How are water-tube boilers classed according to the gas flow arrangement?
5.Translate into English:
1. В водотрубном котле вода циркулирует в трубках.
2. Форсунки расположены на фронте котла.
3. Пароперегреватель подогревает пар, а экономайзер – питательную воду.
4. Циркуляция в котле может быть естественной и принудительной.
5. Котлы подразделяются на котлы низкого, среднего и высокого давления.
6. Котлы могут быть одно-, двух- и трехбарабанные.
7. Наклон котельных трубок может быть от 30° до 90°.
8. Пароперегреватель располагается вертикально или горизонтально.
9. Водотрубные котлы бывают однопроточными и двухпроточными.
TEXT B
WATER-TUBE BOILERS
The water-tube boiler is used to generate steam having high pressure and temperature. It is a type of the boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes.
The heated water then rises into the steam drum. Here, saturated steam is drawn off the top of the drum. The steam enters the furnace through a superheater to become superheated. Superheated steam is defined as steam that is heated above the boiling point at a given pressure. Superheated steam is a dry gas and therefore used to drive turbines, since water droplets can severely damage turbine blades.
Cool water at the bottom of the steam drum returns to the water drum through large-bore downcomer tubes.
Water-tube boilers are the most widely used boilers. They have replaced many boilers, including the fire-tube type, mainly because of the following reasons:
· The weight of the water-tube boiler is much less than any type of boiler of equivalent size.
· Steam raising and steam generation process is much faster.
· The design can include any kind of modifications.
· It has very high efficiency than the rest of the boilers.
· The design facilitates good natural circulation of the feed water.
E X E R C I S E S
1. Find the corresponding translation and memorize.
2. Answer the questions.
TEXT C
PARTS OF WATER-TUBE BOILERS
All water-tube boilers have the following essential parts:
1. The steam drum, which provides a reservoir for the water, its distribution to the tubes, a place for separation of steam and water and collection of the steam for delivery.
2. The water drum, which provides the distribution of water, entering it from the downcomers, to the screen and generating tubes.
3. Headers, which perform a similar duty to that of the drums. In general, the drums are large enough to be entered through manholes, and access to the interior of the headers is provided by hands.
4. Generating tubes, which consist of numerous small diameter tubes around which the hot gases circulate and in which the water receives heat to become steam.
5. The furnace, which is used for combustion of fuel and generating hot gases.
6. The superheater, which superheats the steam.
7. The air heater, which is used to heat the air.
8. The economizer, which heats the feed water before the drum.
9. Various appliances to control the operation and to safeguard the boiler and personnel from possible damage. These include safety valves, gauge glasses, blowdown valve, feed water stop and check valves, steam stop valves, salinometer cock, pressure gauges and soot blowers.
Vocabulary
essential, adj основной
distribution, n распределение
delivery, n снабжение; доставка
generating tubes водогрейные (испарительные) трубки котла
similar, adj подобный; сходный
distinction, n различие
manhole, n лаз; горловина; отверстие для доступа
access, n доступ; вход
interior, n внутренняя часть
appliance, n устройствo
safeguard, v предохранять
damage, n повреждение
gauge glass водомерное (водоуказательное) стекло
blowdown valve клапан продувки котла
stop valve стопорный (запорный) кран
check valve обратный (невозвратный) клапан
steam stop valve паровой стопорный (запорный) клапан
salinometer cock солемерный кран
pressure gauge манометр; датчик давления
soot blower сажеобдуватель
E X E R C I S E S
1. Give answers to the questions:
1. Enumerate the parts of a water-tube boiler.
2. What function do the steam and water drums perform?
3. What is the difference between the drums and the headers?
4. Where are generating tubes placed?
5. Speak about the functions of the furnace, the superheater, the air heater and the economizer.
6. Why are various appliances installed in the boiler?
7. What devices are fitted to control the boiler operation?
2. Translate into English:
1. Часть установки, где сгорает топливо, называется топкой.
2. Перегрев пара осуществляется в особых устройствах, называемых пароперегревателями.
3. Воздухоподогреватель служит для подогрева воздуха перед подачей в топку.
4. Экономайзер – это подогреватель питательной воды.
5. Для обеспечения безопасной работы котлов на них оборудуется ряд устройств.
6. К ним относятся предохранительные клапаны, клапан продувки котла, стопорный и обратный клапаны питательной воды, паровые стопорные клапаны, солемерный кран, водомерные стекла, манометры и сажеобдуватели.
UNIT 4
TEXT A
FUEL OIL
The quality of fuel is determined by its elementary composition, calorific (heat) value, viscosity, specific gravity, flash point, ignition temperature, pour point and some other characteristics.
Fuel oil is composed of carbon, hydrogen, oxygen, sulphur and nitrogen, the amount of each depending on the grade of oil. The chief constituents are carbon and hydrogen.
The calorific value of fuel oil fuel is the heat available from that fuel when it is completely burned. There are two values:
• Higher Calorific Value - the water of combustion is entirely condensed and the heat contained in the water vapor is recovered;
• Lower Calorific Value - the products of combustion contains the water vapour and the heat in the water vapour is not recovered.
The practical method of determining the B.t.u. equivalent of oil fuel is by means of a calorimeter. The B.t.u. equivalent varies from 17,000 to 20,000 per lb. of oil.
Viscosity is the resistance of oil to flow. As temperature affects the flow, the viscosity is usually determined at 50-75-80°C. depending on fuel. Heavy oils usually have high viscosity and light oils low viscosity at 50°C. Viscosity is obtained by means of a viscosity meter. In Europe to measure viscosity they use either Redwood or Saybolt seconds.
Specific gravity is a relation between the weights of a definite volume of oil and water, both liquids being at the same temperature. The specific gravity is obtained by means of a hydrometer.
Flash point is the temperature at which the fuel is ignited with a small open flame. This flame disappears immediately after ignition.
Ignition temperature is the minimum temperature required to ignite fuel oil vapour in air without a flame being present.
Pour point is the lowest temperature at which the fuel can be easily handled.
Such fuel characteristics as carbon content, ash content, sulphur content, water content, mechanical impurities, total acidity, alkali content, content of vanadium and sodium are also very important.
Vocabulary
quality, n качество
determine, v определять
elementary composition элементарный состав
calorific (heat) value теплотворная способность; теплотворность;
теплота сгорания
available, adj зд. полезный
viscosity, n вязкость
specific gravity удельный вес
flash point температура вспышки
ignition temperature температура воспламенения
pour point температура застывания
carbon, n углерод
hydrogen, n водород
oxygen, n кислород
sulphur, n сера
nitrogen, n азот
constituent, n составная часть
release, n освобождать; выделять
resistance, n сопротивление
flow, n течение; текучесть
viscosity meter вискозиметр
relation, n отношение
weight, n вес
volume, n объем
ignite, v зажигать; воспламенять
disappear, v исчезать
handle, v зд. перекачивать
carbon content содержание углерода
ash content зольность
mechanical impurities механические примеси
total acidity общая кислотность
alkali щелочь
E X E R C I S E S
1.Give English equivalents:
Состоять из; топливо; основные составляющие; величина; высшая теплота сгорания (теплотворность); низшая теплота сгорания (теплотворность); с помощью калориметра; меняться, варьироваться; так как; в зависимости от; вискозиметр; измерять; секунды Редвуда или Сейболта; на 40° выше; самая низкая температура; содержание влаги; ванадий; натрий.
2. Ask questions according to the model:
| Model. The physical characteristics of this oil should be determined at once. What should be determined at once? |
1. The specific gravity should be obtained by means of a hydrometer.
2. The viscosity of oil should be determined at 50°-80°C.
3. The constituents of oil should be burnt in suspension.
4. The fuel oil and the air should be preheated for complete combustion.
3. Complete the sentences:
1. We determine the quality of fuel by such characteristics as ….
2. Fuel oil is composed of ….
3. The Higher Calorific Value is ….
4. The Lower Calorific Value is ….
5. We determine the B.t.u. equivalent of oil fuel by ….
6. Viscosity is ….
7. A viscosity meter is a device ….
8. Specific gravity is a relation ….
9. The flash point is the temperature ….
10. Pour point is the temperature ….
4. Answer the questions:
1. What characteristics should be known to determine the quality of fuel?
2. What is oil composed of?
4. What does the grade of oil depend on?
5. What is the calorific value?
6. How do we measure the heat value of fuel oil?
7. Is viscosity essential for fuel practicability?
8. Does the temperature affect the flow?
9. What is the specific gravity?
10. What is the difference between the flash point and the ignition temperature?
11. Why is it necessary to know the pour point?
12. What other characteristics should we know?
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