angls

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"Stroke" refers to the piston movement. The upper limit of piston movement is called top dead center, or TDC. The lower limit of piston movement is called bottom dead center, or BDS.

A stroke constitutes piston movement from TDC to BDC, or BDC to TDC. In other words, the piston completes a stroke each time when it changes direction of motion. Where the entire cycle of events in the cylinder requires four strokes (two crankshaft revolutions ), the engine is called a four-stroke-cycle engine or a four-cycle-engine. The four strokes

Working process of four stroke cycle.

are intake, compression, power and exhaust. a )Intake

On the intake stroke the intake valve has opened. The piston is moving down, and a mixture of air and vaporized gasoline1 is being drawn into the cylinder through the valve opening. The mixture of gasoline and air

is delivered to the cylinder by the fuel system, which will be considered on a later page.

b) Compression

After the piston reaches BDC or the lower limit of its travel, it begins to move upward, and at this instant the intake valve closes. The other valve is also closed so that the cylinder is sealed. The piston moves upward, compressing the mixture to one-sixth of its original volume or less. This creates a high pressure within the cylinder.

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c) Power

As the piston reaches TDC or the upper limit of its travel, an electric spark is generated at the cylinder spark plug. The spark plug consists of two wire electrodes, which are electrically insulated from each other. At the proper instant the ignition system delivers a high-voltage surge2 of electricity to the spark plug. The electric spark jumps3 across the gap between the spark plug electrodes. The spark ignites the highly explosive mixture of gasoline vapor and air. Rapid combustion takes place, and the high pressure within the cylinder increases to as much as 400 pounds5 per square inch. At this instant a piston (3 inches6 in diameter) would have a pressure of nearly 1 ½ tons pushing against it. This terrific pressure against the top of the piston forces it downward, and a power impulse is transmitted to the engine crankshaft through the connecting rod and crank. As the piston moves down on the power stroke, it continues to transmit turning effort to the shaft.

d) Exhaust

As the piston reaches the lower limit of its travel again the exhaust valve opens. The piston moves upward on the exhaust stroke, forcing the gases out of the cylinder through the exhaust valve opening. At the instant that the piston once more reaches top dead center, the exhaust valve closes and the intake valve opens so that, when the piston begins to move downward on the intake stroke, refresh charge of gasoline vapor and air can be drawn into the cylinder. These four strokes are continually repeated during the operation of the engine.

		ПРИМІТКИ
1.	vaporized gasoline –	запалювальна суміш
2.	high-voltage surge –	імпульс високої напруги
3.	spark jumps –	іскра проскакує
4.	explosive mixture –	вибухова суміш
5.	as much as 400 pounds – не меньше 400 футів
6.	3 inches –	3 дюйми

ЗАВДАННЯ 1

Дайте відповіді на запитання:

1.How many strokes take place in the engine cylinder?

2.When does the piston complete the stroke?

3.What is a four-cycle engine?

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4.What strokes take place in the engine cylinder?

5.What action takes place in the cylinder during the intake stroke?

6.What action takes place on the compression?

7.What action takes place during the power stroke?

8.What does the spark plug consist of?

9.What action takes place during the exhaust?

ЗАВДАННЯ 2

Складіть речення із словосполучень:

Stroke, to complete, to change, direction, to require, intake, compression, power, exhaust, to mix, to deliver, to reach, to create, spark plug, ignition system, vapor, air, to increase, to decrease, to force, to transmit, to repeat.

ЗАВДАННЯ 3

Зробіть лексико-граматичний аналіз речень:

1.The piston is moving down, and a mixture of air and vaporized gasoline is being drawn into the cylinder through the valve opening.

2.The piston moves upward on the exhaust stroke, forcing the burned gases out of the cylinder through the exhaust valve opening.

ЗАВДАННЯ 4

Перекладіть на англійську мову:

1.Після того, як поршень досягне нижньої мертвої точки, він починае рухатись вгору і у цей момент впускний клапан закриваеться.

2.Ці чотири такти безперервно повторюються під час роботи двигуна.

TEXT B

MULTIPLE-CYLINDER ENGINE

A single cylinder provides only one power impulse every two crankshaft revolutions and is delivering power only one-fourth of the time. To provide a more continuous flow of power, modern engines use four, six, eight, or more cylinders. In a six-cylinder engine, for example, the cranks on the crankshaft are set 120 degrees apart, the cranks for cylinders 1 and 6, 2 and 5, and 3 and 4 being in line with each other1. The cylinders fire or deliver the power strokes in the following order:1-5-3-6-2-4.

Thus the power strokes follow each other so closely that there is a continuous and even delivery of power to the crankshaft. Even though the

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power impulses in a multi-cylinder engine follow each other so closely that a fairly even flow of power is obtained, additional leveling off the power impulses2 is desirable so that the engine will run more smoothly. A flywheel is used to achieve this result. To understand how a flywheel functions, let us consider a single-cylinder engine. It is delivering power only one fourth of the time during the power stroke. During the other three strokes it is absorbing powerto push out the exhaust gas, to pull in a fresh charge, to compress the charge. The flywheel makes the engine run without varying too much in speed. It is a heavy steel wheel, attached to the end of the crankshaft. When it is rotating, considerable effort is required to slow it down or stop it. Thus, although the wheel slows down somewhat as it delivers power to the engine during the exhaust, intake, and compression strokes, the wheel speed increases during the engine power strokes. In effect, the flywheel absorbs some of the engine power during the power stroke and then gives it back to the engine during the other three engine strokes.

In the multi-cylinder engine the flywheel functions in a similar manner, absorbing power when the engine tends to speed up during the power strokes and giving up power to the engine when the engine tends to slow down during intervals when little power is being delivered by the engine.

ПРИМІТКИ

1.In a six-cylinder engine, for example, the cranks on the crankshaft are set

120degrees apart, the cranks for cylinder 1 and 6, 2 and 5, and 3 and 4 being in line with each other. - У шестициліндровому двигуні кривошипи коленвалу розташовані під кутом 120 градусів, причому кривошипи циліндрів 1 і 6, 2 і 5, 3 і 4, розташовані на одній лінії.

2.…additional leveling off the power impulses… - додаткове вирівнювання силових імпульсів.

ЗАВДАННЯ 1

Дайте відповіді на запитання:

1.For what purpose do we use four, eight and more cylinders in modern engines?

2.What firing order takes place in a six-cylinder engine?

3.What purpose is a flywheel used for?

4.In what way does the flywheel function?

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ЗАВДАННЯ 2

Використайте словосполучення у своїх реченнях:

to use , to follow, wheel, flywheel, to achieve, to absorb, to compress, to attach, to slow, speed, to give back, to tend, to fire, to revolve, to add, to produce, to rotate.

ЗАВДАННЯ 3

Зробіть лексико-граматичний аналіз речень:

1.Even though the power impulses in a multi-cylinder engine follow each other so closely that a fairly even flow of power is obtained, additional leveling off the power impulses is desirable so that the engine will run more smoothly.

2.Thus, although the wheel slows down somewhat as it delivers power to the engine during the exhaust, intake and compression strokes, the wheel speed increases during the engine power stroke.

ЗАВДАННЯ 4

Перекладіть на англійську мову:

1.Маховик представляе собою стальне колесо, прікріплене до кінця коленчастого валу.

2.Маховик поглинае деяку частину енергії двигуна під час робочього ходу, а потім віддае її двигуну під час трьох інших тактів двигуна.

ЗАВДАННЯ 5

Виберіть правильний варіант:

1.There (were, will be, have been) several bad accidents at this corner recently.

2.There (will be, were, are) lights in the middle of the crossing.

3.They (test, will test, tested) the new engine last month.

4.He (cuts, will cut, cut) himself while be (was repairing, repair, was repaired) his car.

5.The light (changed, has changed, changes) just from green to red.

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TEXT C

TWO-STROKE CYCLE

Two-stroke cycle engines differ in that they have no air inlet valves and every downward stroke of the piston is a power stroke, in other words there is a power stroke for every revolution of the crankshaft.

THE CHARGING AND COMPRESSION STROKE

The piston nears the bottom-dead center, the intake air is entering the cylinder through the inlet port and the exhaust gas is still escaping through the exhaust ports. Part of the intake air, known as the scavenging air, mixes with the exhaust gas and flows out as well.

As the piston rises it closes the intake port, the rest of the stroke being a compression stroke. The piston compresses the air until it almost reaches the top dead point when the atomized fuel is injected.

THE WORKING AND EXHAUST STROKE.

As the piston descends it uncovers the exhaust port, the rest of the stroke being an exhaust stroke.

ЗАВДАННЯ 1

З`ясуйте у чому різниця між дво- і чотирьох тактними циклами

ЗАВДАННЯ 2

Складіть 5 запитань до тексту С.

	UNIT 4
fuel line –	трубопровід подачі палива
warm up –	прогрівання, нагрівання

over-the-road operation – експлуатація на дорогах з твердим покриттям rocker arm – клапанне коромисло

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ENGINE SYSTEMS

TEXT A

In addition to1 the engine itself, which is the power producer, there must be four systems to feed the engine.

These systems are:

1.The fuel system

2.The lubrication or oiling system

3.The ignition system

4.The cooling system.

FUEL SYSTEM

The fuel system consists of a tank in which the liquid gasoline is stored, a fuel line, or tube, through which the gasoline can be brought from the tank to the engine, a pump, which pulls the gasoline through the fuel line, and a carburetor, which mixes the gasoline with air.

Main parts of the carburetor engine fuel system.

The carburetor is designed to mix each pound of gasoline with 9 to 15 pounds of air under various operation conditions.

The richer mixtures of about 9 pounds of air per pound2 of gasoline are for starting, initial warm-up, and acceleration, while the leaner mixtures of about 15 pounds of air per pound of gasoline are for normal over-the-road operation.

FUEL PUMP

The fuel pump consists of a rocker arm, a flexible diaphragm, and two valves. The rocker arm rests against a cam on the camshaft so that rotation

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of the shaft makes the arm rock3. This rocking motion causes the diaphragm to fluctuate up and down, alternately creating pressure and vacuum in the pump chamber. When vacuum is created, the inlet valve is lifted off its seat4, allowing gasoline to be drawn from the fuel tank, through the fuel line, and into the pump chamber.

On the return stroke the diaphragm creates pressure in the pump chamber. This causes the inlet valve to close and the outlet valve to open, forcing gasoline from the pump chamber through a fuel line to the carburetor.

ПРИМІТКИ

1. in addition to -	крім
2. per pound –	на один фунт

3.… rotation of the shaft makes the arm rock …

… кручіння вала змушує коромисло гойдатися …

4. seat –

гніздо клапана

ЗАВДАННЯ 1

Дайте відповіді на запитання:

1.What does the fuel system consist of?

2.What is the purpose of the carburetor?

3.What is a rich mixture?

4.What is a lean mixture?

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6.What is the purpose of the fuel system?

7.What does the fuel pump consist of?

ЗАВДАННЯ 2

Складіть речення із словосполучень:

to feed, lubrication system, liquid, fuel line, pump , to pull, to design, condition, rich, to start, lean, rocker arm, to create, to allow, to draw.

ЗАВДАННЯ 3

Дайте синоніми до слідуючих слів:

to design, various, to start, the inlet valve, to return, to close, initial, oiling system.

ЗАВДАННЯ 4

Зробіть лексико-граматичний аналіз слідуючих речень:

1.When vacuum is created, the inlet valve is lifted off its seat, allowing gasoline to be drawn from the fuel tank , through the fuel line, and into the pump chamber.

2.In addition to the engine itself, which is the power producer, there must be four separate systems to feed the engine.

ЗАВДАННЯ 5

Перекладіть на англійську мову:

1.Система живлення складається з ємності паливопроводу або трубки, насоса та карбюратора.

2.Паливний насос складається з гойдаючогося важеля, гнучкої діафрагми та двух клапанів.

TEXT B

CARBURETOR

The gasoline is delivered to a bowl on the side of the carburetor. The bowl contains a float that actuates a needle valve. When the proper level of gasoline in the bowl is reached, the needle valve closes and prevents further1 delivery of gasoline. When the gasoline level falls in the bowl the needle valve opens and additional gasoline is delivered. The proper level of gasoline in the bowl is thus constantly maintained. A small opening (the

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metering-rod jet2) near the bottom of the bowl permits gasoline to flow up through the main gasoline passage. A metering rod3 partly blocks this opening so that an excessive amount of gasoline will not flow.

Air is drawn down through the carburetor venturi by the engine piston as it moves downward on the intake stroke. During this time, the pressure in the cylinder is lower than atmospheric pressure, and this causes air to flow through the carburetor venturi toward the cylinder. The venturi is merely a restriction or narrowing of the main air passage through the carburetor air horn. At any particular speed, only a certain amount of air can pass through the smallest part of the restriction, but below this point additional air can pass since the passage is larger. This means4 that a partial vacuum is created below the smallest part of the venturi. This partial vacuum tends to draw gasoline from the end of the main gasoline passage. The amount of gasoline drawn out is controlled by the speed of the air rushing through the air horn. Carburetors have idling and accelerator circuits that come into operation when the engine is idling or being accelerated.

After the burned gases are expelled from the cylinders they pass through the exhaust manifold into the muffler. The muffler permits the exhaust gases to escape without excessive noise into the atmosphere through the tail pipe.

	ПРИМІТКИ
1. further –	далі, подальше, наприклад: " … and prevents further

delivery of gasoline …” - "… і припиняє подальшу подачу бензину …”

2.metering-rod jet – калібруючий жиклер

3.metering rod – дозуючий пристрій

4. to mean –		значити, означати
5.	means –	засіб
6.	by means of -	за допомогою

ЗАВДАННЯ 1

Дайте відповіді на запитання:

1.What is the purpose of the carburetor?

2.What is the purpose of the float?

3.What action takes place when the needle valve closes?

4.What action takes place when the needle valve opens?

5.What is the function of the metering rod?

6.What is the venturi?

7.What is the purpose of the muffler?