4 Переведите следующие предложения, содержащие глагол-сказуемое в перфектной форме.

1. Farm mechanization programs in the past have been largely devoted to labor saving. 2. Tractor engine speeds have been increased. 3. Mаnу different sizes and types of engines have been used for tractors. 4. The practice of operating cooling systems under pressure has become more frequent because of the reduction in evaporation losses. 5. Many attempts have been made to utilize the waste heat from engines. 6. The most important division of engine types is by the cycles which have been described in the previous chapter.

5. Назовите по-английски основные формы следующих глаголов:

знать, брать, давать, делать, толкать, гореть, приходить, становиться, посылать, использовать.

6. Прочтите и переведите текст а.

The 4 - stroke engine

The four-stroke-cycle engine requires four strokes of each piston, two up and two down (two complete revolutions of the crank-shaft), to complete its cycle. The strokes, in the order in which they occur, are called induction (intake) compression, power, and exhaust.

The Induction stroke. The piston moves down, inlet valve open, exhaust valve closed. This downward movement of the piston creates a partial vacuum inside the cylinder causing fuel/air mixture to rush in through the inlet valve passage. When the piston reaches the bottom of its stroke the inlet valve closes to prevent any escape of the fuel, therefore the fuel is trapped inside the cylinder.

The compression stroke. The piston moves up the inlet valve is closed, the exhaust valve is closed. This upward movement compresses the fuel/air mixture into a small space at the top of the cylinder.

The power stroke. When the piston is at the top of the compression stroke with both valves closed, a spark is arranged to take place across the points of a spark plug. This spark immediately sets fire to the mixture which burns and expands forcing down the piston: this provides the power.

The exhaust stroke. The piston moves up the cylinder again, the inlet valve is closed the exhaust valve is open. This upward movement pushes the burnt gases out through the exhaust valve outlet and to the atmosphere.

7. Найдите в тексте ответы на следующие вопросы:

1. Из каких четырех тактов поршня состоят рабочий цикл четырехтактного двигателя?___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Какое движение поршня создает вакуум в цилиндре?________________________

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3. Какое движение поршня снижает рабочую смесь?__________________________

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4. При каком положении поршня происходит зажигание рабочей смеси?_________

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5. Как происходит выпуск отработанных газов?_______________________________

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