Section d engine-cooling system
When automobiles work a considerable amount of heat produced by internal combustion engines is transferred to cylinder walls and combustion chamber walls.
The maximum temperature of the cylinder walls is determined by. lubricating conditions. After a certain temperature ranging from 160°C to 200°G has been reached lubricating conditions begin to deteriorate rapidly. It is necessary that the excess heat should be removed from reciprocating parts, cylinders and other parts which are sub ected to the gasoline combustion flames. Otherwise, the increased wear of pistons and other parts is likely to occur.
Two kinds of cooling systems are in use for automobile engines, one using air exclusively and the other using air and liquid.
Let us look at the diagram and consider the operation principle of the liquid cooling system. The piston is at the bottom of the cylinder. On each side of the piston there is the cylinder wall, and beyond the cylinder wall a certain area which .is filled with water, and beyond this area there is the water jacket wall of the cylinder. Circulation of the water through the water jacket is secured by means of the water pump of the automobile which draws the water from the radiator, forces it through the water jackets of the cylinders and returns it into the radiator.
The forward movement of the car forces air into the .radiator and the water is coded. To remove heat from the radiator at low speeds a fan is provided. The fan draws the air through the radiator core.
Many factors should be taken into consideration in designing the cooling system of the engine. First of all, it is necessary to design the water jackets in the proper manner so that ample circulation of water should be secured. Secondly, it is very important to design properly the area surrounding the valve ports so as to secure ample cooling. Otherwise, cylinder warping, valve burning and other troubles will develop. And finally, great attention should be paid to the spark, plug. It is important that the spark plug should stand considerable heat variation and be properly cooled.
Thus, the problem of designing the cooling system is not a simple .thing at all. The importance of the cooling system is obvious. No automobile could operate without the system protecting the engine from overheating.
Exercise 10 Are these statements true or false? If they are false change the statement into the negative form.
When water flows around the engine the engine is cooled and the water is heated.
The hot water enters the radiator through the top and the bottom hoses. 3. The water flows down through the radiator and is cooled by air. 4.The cool water leaves the radiator through the top and the bottom hoses. 5. The water passes through the water pump and goes around the engine. 6.Air is pulled through the radiator by a fan. 7. The fan is turned by a belt 8.The belt is driven by the car driver.
Exercise 11 Complete the paragraph from the wordlist: Air, amount, below, boil, causes, checking, cooled, flows, leak, needs, out of, radiator, reduces, stroke, unless, will.
The friction inside an engine ... heat. Too much heat ... damage the engine and so it ... cooling. Generally, engines are ... by water but some engines are ...-cooled. The water ... around the inside of the engine and reduces the temperature. The water then flows to the ... and is cooled by the air flow. Then it comes ... the radiator and runs through the engine again. Some of the water will ... out of the engine when it is used. The heat of the engine will sometimes cause the water to ... and evaporate into steam. Therefore, the ... of water in the radiator will need ... regularly. In cold conditions (,..0°C ), the water in the radiator will freeze,… anti-freeze, is added to it.
UNIT THREE
MOTOR VEHICLES MAINTANANCE
FACTS ABOUT MATTER
Section A
ENGINES AND FUELS
There are three basic types of fuel for motor vehicles. There is diesel fuel, there is petrol and there is two-stroke mixture.
Most motorcycles have two-stroke petrol engines. There are a few motorcycles with four-stroke petrol engines. There are no motorcycles with diesel engines.
A few cars have diesel engines. There are also a few cars with two-stroke engines but most cars have four-stroke petrol engines. Most lorries have diesel engines. There are a few lorries with four-stroke petrol engines but there are no lorries with two-stroke petrol engines.
There is a lot of carbon (about 85%) in diesel fuel. There is also a lot of carbon in petrol. There is a little hydrogen in both these fuels. There is also a little sulphur (about 1%) in diesel fuel but there is no sulphur in petrol.
Two-stroke mixture is about 95% petrol and 5% oil. There is no oil in the fuel for four-stroke engines.
Exercise 1 Answer these questions. Use the following words: most, a few, none, a little, a lot.
Look at the example.
_ How many motorcycles have diesel engines?
Short answer: None.
Complete answer: No motorcycles have diesel engines.
1. How many motorcycles have four-stroke petrol engines?
2. How many motorcycles have two-stroke engines?
3. How many cars have diesel engines?
4. How many cars have two-stroke engines?
5. How many lorries have diesel engines?
6. How much carbon is there in diesel fuel?
7. How much hydrogen is there in petrol?
8. How much sulphur is there in diesel fuel?
9. How much oil is there in two-stroke mixture?
10. How much oil is there in petrol?
Exercise 2 Read, translate and retell the text to your neighbor.
Not long ago I bought a 2-stroke petrol engine for my motorcycle. The engine fins are made of aluminum alloy. Aluminum alloy is made of two metals. There is aluminum (about 95%) and a little copper in most aluminum alloys. There is no oil sump in this engine. There is about 95 per cent petrol and five per cent oil in the petrol. There is 10 per cent fuel and ninety per cent air in the mixture.
Exercise 3 Amounts are often expressed as percentages or fractions.
Complete this table. Some of them have been done for you.
|
percentages |
|
|
fractions |
|
50% |
(fifty per cent) |
|
|
(a half) |
|
25% |
(twenty five per cent) |
|
|
(a quarter) |
|
75% |
( ) |
|
|
(three quarters) |
|
|
(thirty three and |
a third per cent) |
|
( |
) |
|
(twenty per cent) |
|
|
(a fifth) |
|
|
(forty per cent) |
|
|
( |
) |
|
(seventeen per cent) |
|
|
( |
) |
10% |
( |
) |
|
( |
) |
|
(sixteen and two thirds per cent) |
|
( |
) |
|
|
(two per cent) |
|
|
(a fiftieth) |
|
1% |
( |
) |
|
( |
) |
Exercise 4 Read and translate the words to be remembered.
Percentage, copper, per cent (%), a fraction, rubber, air, with, a half, the fourth, a quarter, five-fifth-fifteen-fifty, lorry-lorries, fifty-fiftieth, how much…?