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Файл:Technical English for Electrical Engineers. Учебное пособие
.pdf
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To compose
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10
To take
To provide
III
1. Read the text paying attention to the terms in bold.
A. C. ELECTRIC MOTORS
Motors for alternating-current circuits may be either single-phase or
polyphase (two- or three-phase). They may again be divided into two
kinds, named respectively:
I. Synchronous; II. Non- or asynchronous, ordinarily called Induction
motors.
Fig. 2. Cutaway Section of an Induction Motor
1. stator winding; 2. winding in rotor slot; 3. rotor winding;
4. governor weights; 5. bearing; 6. shaft; 7. wool yarn; 8. oil well; 9. oil
cup; 10. governor rods; 11. bearing bracket; 12. slot in stator; 13. stator
core; 14. insulation; 15. stator winding; 16. mica commutator ring:
17. face of commutator; 18. brush holder springs; 19. brush lifting
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device: 20. brush holder; 21. carbon brush; 22. spring barrel; 23. short
circuiting segments; 24. leads from rotor coils to commutator bars;
25. stator windings; 26. frame; 27. base
The most widely used a. c. motor is the induction motor shown in
Fig. 1. It has two main parts: a) the stationary winding or stator, which
sets up a rotating magnetic field, and b) the rotating part of the motor,
i. e. the rotor. The rotor of a commercial a. c. motor consists of an iron
core with large copper bars placed in slots around the circumference
and connected at both ends to copper rings. This is called a squirrel-
cage rotor. When a rotor is placed in a rotating magnetic field, a large
current is induced in it.
A. c. motors are exactly similar in construction to а. с generators and
may be called inverted alternators, since the same machine may be used
as either a generator or a motor. Synchronous motors are very suitable for
large powers, where the machine can be started up without load, and once
started run for long periods.
For supplying direct-current power networks, the supply comes first
from an alternating-current source and is converted to direct current by
synchronous converters or motor-generator sets.
2. Answer the questions:
1. What is called a squirrel cage rotor?
2. What are a.c. motors similar to in construction?
3. What are a.c. motors used for?
4. What is the principle of a.c. motors work?
3. Speak on:
Construction of a.c. motor.
4. Name the main parts of a.c. motor.
5. Describe Figure 2.
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ENGINES
I
1. Read the text.
THE ORIGINE OF ENGINES
Do you know what the first engine was like? It was called the
"water wheel". This was an ordinary wheel with blades fixed to it, and
the current of a river turned it. These first engines were used for
irrigating fields.
Then a wind-powered engine was invented. This was a wheel, but a
very small one. Long wide wooden blades were attached to it. The new
engine was driven by the wind. Some of these ones can still be seen in
the country.
Both of these, the water- and wind-operated engines are very
economical. They do not need fuel in order to function. But they are
dependent on the weather.
Many years passed and people invented a new engine, the one
operated by steam. In a steam engine, there is a furnace and a boiler.
The furnace is filled with wood or coal and then lit. The fire heats the
water in the boiler and when it boils, it turns into steam, which does
some useful work.
The more coal is put in the furnace, the stronger the fire is
burning. The more steam the faster a train or a boat is moving.
The steam engine drove all sorts of machines, for example, steam
ships and steam locomotives. Indeed, the very first airplane built by
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A.F. Mozhaisky also had a steam engine. However, the steam engine
had its disadvantages. It was too large and heavy, and needed too
much fuel.
The imperfections of the steam engine led to the design of a new
type. It was called the internal combustion engine, because its fuel ignites
and burns inside the engine itself and not in a furnace. It is smaller and
lighter than a steam engine because it does not have a boiler. It is also
more powerful, as it uses better-quality fuel: petrol or kerosene.
The internal combustion engine is now used in cars, diesel
locomotives and motor ships. But to enable airplanes to fly faster than the
speed of sound another, more powerful engine was needed. Eventually, one
was invented and it was given the name "jet engine". The gases in it reach
the temperature of over a thousand degrees. It is made of a very
resistant metal so that it will not melt.
2. Answer the questions:
1. How many types of engines were there in the history of their
development? Speak on their construction and principle of work.
2. What types of modern engines do you know? Where are they
used?
3. Are old types of engines still used now?
II
1. Read the text.
ENGINE TYPES
In 1903, the first aero plane flew. It was powered by a petrol engine.
This kind of engine is still used in some aircraft. However, most aero planes
of today have jet engines. How do these two types of engine differ?
The Petrol Engine
The fuel and air mixture enters the cylinder. The piston rises and it
compresses the mixture. The compressed mixture is ignited by the spark. As
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the combustion gases expand, they push the piston down, and the crankshaft
turns. On an aircraft the crankshaft is connected to the propeller. In a car it
transmits power to the wheels.
The Jet Engine
The compressor sucks air into the engine, and compresses it. Then the
compressed air mixes with the fuel and this mixture is burnt in the
combustion chamber. The combustion gases drive the turbine. This drives
the compressor. The exhaust gases escape from the engine through the
nozzle. This pushes the aircraft forwards.
2. Copy the drawings of the petrol and jet engines, and label them
with the following words;
fuel and air mixture; cylinder; piston; spark; combustion gases;
crankshaft; propeller; compressor; combustion chamber; turbine; nozzle;
exhaust gases.
3. Use arrows to show the movement of air and gases through the
jet engine, and to show how the parts move the petrol engine.
4. Speak on the principle of work of petrol and jet engines using the
following verbs (fly, enter, ignite, rise, transmit, push down/ forward, suck,
turn, burn, drive, escape) and nouns (fuel, piston, mixture, crankshaft,
compressor, engine, combustion chamber, nozzle).
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5. Put the following stages in the correct order:
power is produced the mixture is burned
fuel and air mixture enters the combustion chamber
6. Look at the description of the petrol engine and find the three
stages.
7. Do the same for the description of the jet engine. Could the order
of the stages be changed?
III
1. Read the text paying attention to the terms in bold.
DIESEL ENGINES
The oil engine (diesel engine) is also a form of internal combustion
engine. It has the usual arrangement of cylinder, piston, connecting rod,
crank, inlet and exhaust valves as we find in petrol engine. In place of
carburetor and sparking plug it has an injection pump and a fuel
injection valve (injector). Unlike spark-ignition engines it uses the heat
of compression to fire the fuel and is, therefore, called compression-
ignition engine.
It utilizes a fuel known as diesel oil, which is forced in the form of
a fine spray through a suitable nozzle directly into the combustion
space. No mixture of fuel and air is introduced into the cylinder, the
compression-ignition (CI) engine draws in pure air only. This air is then
compressed by the ascending piston to a high pressure. As a result of it the
temperature of the air is raised considerably so that the fuel oil injected
into the cylinder ignites rapidly. Thereafter the gaseous products expand
providing the energy for the power stroke.
The high-output oil engines are nearly all of two-stroke type. The
charge is filled into the cylinder by means of a blower which assists
both the intake and exhaust processes. One cycle is completed within
one revolution, i.e. in two strokes – compression and expansion.
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2. Match the columns:
1) to assist
a) to blow in
2) to fire
b) to use
3) to utilize
c) to finish
4) to have
d) to ignite
5) to complete
e) to grow up
6) to raise
f) to help
7) to inject
g) to possess
3. Name the main parts of a diesel engine.
4. Speak on the work of a diesel engine.
IV
1. Read the text.
AIR-COOLED ENGINES
All vehicle engines are air-cooled to some degree. Even in water-cooled
engines heat is transmitted first from cylinder to water and afterwards, in
the radiator, from water to air. This method of cooling is not difficult to
accomplish, because the heat taken off the hot cylinder walls by water can
be distributed without difficulty upon the large cooling surface of the
radiator, and so easy transmission of heat to air is made possible.
Reciprocating engines used in aircraft are almost entirely air-cooled.
Aircraft engines cooled by air are manufactured today in sizes ranging
from 50 to 3500 hp and they have superseded water-cooled engines. The
principal advantages of air-cooled aircraft engines are low weight, and
greater reliability in operation. Modern motor-cycles are also designed
almost exclusively with air-cooled engines.
New designs of air-cooled vehicle engines are notable for their easy
maintenance, reliability and economical operation.
2. Speak on: (1) water – cooled engine, its construction,
3. Translate the text in written form. Mind the terms.
disadvantages, use.
(2) air – cooled engine, its advantages and use.
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V
1. Read the text.
HEAT ENGINES
The heat engine is a machine that converts heat energy to
mechanical energy. The engines of motor-cars, motorcycles, farm
tractors, motor boats, etc., are heat engines, which belong to the subgroup
of internal combustion engines. Combustion engines may be divided into
several types according to the number of piston strokes. Most of modern
automotive engines operate on four-stroke cycle. Cross section of a fourstroke SI engine is shown in Fig. 3. There are also engines which operate
on two-stroke and six-stroke cycles.
A diesel engine is a machine which produces power by burning oil in
a body of air which has been squeezed to a high pressure by a moving
piston. Diesel engines are especially suitable where an independent
source of power is required, as in ships, locomotives, mobile equipment
of all sorts and isolated power plants.
Fig. 3. Cross Section of a Four-Stroke SI (spark-ignition) Engine
1. sir cleaner; 2. carburetor; 3. intake manifold; 4. exhaust manifold;
5. piston; 6. piston pin; 7. cylinder block; 8. connecting rod; 9. crank-case;
10. crankshaft; 11. valve; 12. spark plug; 13. combustion chamber;
14. cam-shaft; 15. water jacket; 16. main bearing; 17. oil pan
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Steam, gas and oil engines were known and used prior to the
1) Reciprocating engine
a) a heat engine where an internal
working fluid is heated by
combustion of an external
source, through the engine wall
or a heat exchanger
2) Steam engine
b) a combustion engine that uses
the oxygen in atmospheric air to
oxidize ('burn') the fuel carried,
rather than carrying an oxidiser,
as in a rocket
invention of the diesel engine. The steam engine converts the heat energy
of steam to mechanical energy. A typical steam reciprocation engine
consists of a cylinder fitted with a piston. A connecting rod and
crankshaft change the piston to-and-fro motion into rotary motion. The
steam pressure on the piston varies during the stroke, and it is a flywheel
which maintains a constant output velocity.
2. Translate the following terms: heat engine, sir cleaner, carburetor,
intake manifold, exhaust manifold, piston, steam, gas and oil engines,
steam reciprocation engine, piston pin, cylinder block, connecting rod,
crank-case, crankshaft, valve, spark plug, combustion chamber,
camshaft, water jacket, main bearing, oil pan.
3. Answer the questions:
1. What is heat engine?
2. What subgroup do combustion engines belong to?
3. What parts may combustion engines be divided into?
4. How does a diesel engine produce power?
5. What does a moving piston squeeze?
6. Where are diesel engines used?
4. Match the columns:
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3) Air-breathing combustion
engine
c) a heat engine that performs
mechanical work using steam as
its working fluid
4) External combustion engine
(EC engine)
d) an engine in which the
combustion of a fuel occurs
with an oxidizer in a
combustion chamber
5) Internal combustion engine
e) a heat engine that uses one or
more reciprocating pistons to
convert pressure into a rotating
motion
5. Speak on: (1) four stroke cycle engine, using Fig. 3.
(2) steam reciprocation engine (its construction and
work)
6. What engines are mentioned in the text?
VI
1. Read the text and discuss the following: in what way
electricity and magnetism are closely linked?
OERSTED’S EXPERIMENT
In the winter of 1819–20 Christian Oersted was doing experiments to
find links between electricity, magnetism, light and heat. One of these
experiments was very important, as it was the first step towards the
invention of the generator or dynamo.
Oersted's apparatus was very simple. He took a piece of wire and bent it
to make a kind of bridge. The ends of the wire could be connected by leads to
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