Дизельные двигатели. Эксплуатация и обслуживание = Diesel engines. Operation and maintenance. Практикум

3. Translate from Russian into English:

1.Наддув или зарядка цилиндров под давлением увеличивает выходную мощность двигателя.

2.Соотношение топливо-воздух всегда постоянно.

3.При наддуве цилиндр наполняется воздухом, давление которого на несколько фунтов выше атмосферного.

4.Скорость турбонагнетателей изменяется в зависимости от нагрузки на двигатель.

5.При наличии большего веса воздуха в цилиндре можно сжечь больше топлива.

6.Перед наддувом цилиндры двигателя должны быть очищены, продуты.

7.Чистое увеличение мощности двигателя при наддуве может доходить до 50 %.

8.В настоящее время широко используется газотурбонаддув.

4. Ask your talk partner and let him give answers:

•about supercharging;

•if supercharging increases the power output;

•about the relation between the volume and pressure during supercharging;

•about the relation between weight of air in the cylinder and fuel;

•about the way of arranging the valve timing;

•about type of supercharging which is widely used in modern ships;

•about principles on which the turbochargers operate;

•about the way of compressed air to the under piston space;

•if the pumping action of the under piston space provides 2nd stage of compression.

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5. Translate the following sentences using the vocabulary from the exercises:

1.Следует перебрать и проверить под давлением пусковые клапаны всех цилиндров ГД.

2.Следует заменить бронзовые втулки и пальцы коромысел.

3.Следует отрегулировать головные подшипники ГД на новые ремонтные размеры поршневых колец.

4.Все цилиндровые втулки ГД проверили на эллипсоидный

износ.

5.Необходимо вскрыть редуктор, произвести необходимый осмотр и дефектовку.

6.Прошлифовать шейки распредвала ГД до новых ремонтных размеров.

7.Следует установить крышки цилиндров на место, гайки шпилек затянуть по инструкции.

8.Снять и отправить на завод 2 комплекта крейцкопфных узлов для шлифовки пальцев.

9.Следует очистить и промыть детали. Трубки пресной воды снять с крышек цилиндра. Коромысла клапанов снять с цилиндровых крышек.

10.Следует снять крышки смотровых окон картера, слить смазочное масло.

11.Отсоединить генератор от коленвала двигателя, ослабить затяжные болты. Промыть зеркало цилиндров. Промыть и очистить зарубашечное пространство охлаждения. Втулки обмерить и предъявить Регистру.

12.Корпус турбонагнетателя снять, очистить, промыть и подщелочить. Все детали следует перебрать, очистить, промыть и обмерить. Ротор нужно отбалансировать, подшипники заменить, все детали предъявить Регистру.

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13.Необходимо снять рамовые подшипники, шейки коленвала прошлифовать на станке и предъявить Регистру. Старые (существующие) шатуны заменить новыми с гидравлической затяжкой болтов. Снять воздухоохладитель, воздушные и водяные полости очистить химическими средствами и промыть.

14.Следует собрать дизельный двигатель, дизель испытать в работе по утвержденной Регистром технологии (схеме).

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10.STARTING AIR SYSTEM

1.Read and translate the text. Pay attention to new phrases.

Starting Air System

Diesel engines are started by supplying compressed air into the cylinders in the appropriate sequence for the required direction. A supply of compressed air is stored in air reservoirs or “bottles” ready for immediate use. Up to 12 starts are possible with the stored quantity of compressed air. The starting air system usually has interlocks to prevent starting if everything is not in order.

Compressed air is supplied by air compressors to the air receivers. The compressed air is then supplied by a large bore pipe to a remote operating non-return or automatic valve and then to the cylinder air start valve. Opening of the cylinder air start valve will admit compressed air into the cylinder. The opening of the cylinder valve and the remote operating valve is controlled by a pilot air system. The pilot air is drawn from the large pipe and passes to a pilot air control valve which is operated by the engine air start lever.

When the air start level is operated, a supply of pilot air enables the remote valve to open. Pilot air for the appropriate direction of operation is also supplied to an air distributor. This device is usually driven by the engine camshaft and supplies pilot air to the control cylinders of the cylinder air start valves. The pilot air is then supplied in the appropriate sequence for the direction of operation required. The cylinder air start valves are held closed by springs when not in use and opened by the pilot air enabling the compressed air direct from the receivers to enter the engine cylinder. An interlock is shown in the remote operating valve line which stops the valve opening when the engine turning gear is

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engaged. The remote operating valve prevents the return of air which has been further compressed by the engine into the system.

Lubricating oil from the compressor under normal operation passes along the airlines and deposits on them. In the event of a cylinder air starting valve leaking, hot gases would pass into the air pipes and ignite the lubricating oil. If starting air is supplied to the engine, this would further feed the fire and could lead to an explosion in the pipelines. In order to prevent such an occurrence, cylinder starting valves should be properly maintained and the pipelines regularly drained. Also, oil discharged from compressors should be kept to a minimum, by careful maintenance.

In an attempt to reduce the effects of an explosion, flame traps, relief valves and bursting caps or discs are fitted to the pipelines. In addition, an isolating non-return valve (the automatic valve) is fitted to the system. The loss of cooling water from an air compressor could lead to an overheated air discharge and possibly an explosion in the pipelines, leading to the air reservoir. A high-temperature alarm or a fusible plug which will melt is used to guard against this possibility.

supply compressed air

store in air reservoirs

interlock

admit compressed air into the cylinder

spring

flame traps

fusible plug

in an attempt to reduce the effects

be controlled by a pilot air system

deposit

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careful maintenance

bursting caps

overheated air

melt

be fitted to the system

2. Replace the gaps by the words in the list.

Deposit; is supplied; An interlock; cylinder air start valve; maintenance.

1.Lubricating oil from the compressor under normal operation passes along the air lines and … on them.

2.Opening of the … will admit compressed air into the cylinder.

3.Compressed air …; by air compressors to the air receivers.

4.… is shown in the remote operating valve line which stops the valve opening when the engine turning gear is engaged.

5.Also, oil discharged from compressors should be kept to a minimum, by careful … .

3. Answer the questions.

1.How are diesel engines started?

2.Where is the supply of compressed air stored?

3.What fittings can be in the pipeline to reduce explosions?

4.Give synonyms to the following words.

•essential;

•to transfer;

•to rotate;

•to assist;

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•to supply;

•aim;

•amount;

•velocity;

•separate;

•quantity;

•to employ;

•to be located;

•failure;

•inspection;

•detect;

•to apply;

•to lubricate.

5. Read the verbs and think of nouns which can be matched with these verbs.

•to increase;

•to start;

•to compress;

•to obtain;

•to scavenge;

•to fill;

•to cool;

•to develop;

•to operate;

•to require;

•occur; to fill;

•to enlarge;

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•to arrange;

•remain;

•to change;

•to run;

•to blow;

•to burn;

•to charge.

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11.CONTROL AND SAFETY DEVICES

1.Read the translate the text. Pay attention to new phrases.

Control and Safety Devices

Governors. The principle control device on any engine is the governor. It governs or controls the engine speed at some fixed value while power output changes to meet demand. This is achieved by the governor automatically adjusting the engine fuel pump settings to meet the desired load at the set speed. Governors for diesel engines are usually made up of two systems: a speed sensing arrangement and a hydraulic unit which operates on the fuel pumps to change the engine power output.

Mechanical Governor. A flyweight assembly is used to detect engine speed. Two flyweights are fitted to a plate or bullhead which rotates about a vertical axis driven by a gear wheel. The action of centrifugal force throws the weights outwards; this lifts the vertical spindle and compresses the spring until an equilibrium situation is reached. The equilibrium position or set speed may be changed by the speed selector which alters the spring compression. As the engine speed increases, the weights move outwards and raise the spindle; a speed decrease will lower the spindle. The hydraulic unit is connected to this vertical spindle and acts as a power source to move the engine fuel controls. A piston valve connected to the vertical spindle supplies or drains oil from the power piston which moves the fuel controls depending upon the flyweight movement. If the engine speed increases, the vertical spindle rises, the piston valve rises and oil is drained from the power piston which results in a fuel control movement. This reduces

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fuel supply to the engine and slows it down. It is, in effect, a proportional controller.

Electric Governor. The electric governor uses a combination of electrical and mechanical components in its operation. The speed sensing device is a small magnetic pick-up coil. The rectified voltage signal is used in conjunction with a desired or set speed signal to operate a hydraulic unit. This unit will then move the fuel controls in the appropriate direction to control the engine speed.

Cylinder Relief Valve. The cylinder relief valve is designed to relieve pressures in excess of 10 % to 20 % above normal. A spring holds the valve closed and its lifting pressure is set by an appropriate thickness of packing piece. Only a small amount of lift is permitted and the escaping gases are directed to a safe outlet. The valve and spindle are separate to enable the valve to correctly seat itself after opening.

The operation of this device indicates a fault in the engine which should be discovered and corrected. The valve itself should then be examined at the earliest opportunity.

Crankcase oil mist detector. The presence of an oil mist in the crankcase is the result of oil vaporization caused by a hot spot. Explosive conditions can result if a build-up of oil mist is allowed. The oil mist detector uses photoelectric cells to measure small increases in oil mist density. A motor-driven fan continuously draws samples of crankcase oil mist through a measuring tube. An increased metre reading and alarm will result if any crankcase sample contains excessive mist when compared to either clean air or the other crankcase compartments. The rotary valve which draws the sample then stops to indicate the suspect crankcase. The comparator model tests one crankcase mist sample against all the others and once a cycle against clean air. The level model tests each crankcase in turn against

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