A power installation is a complex consisting of an engine and its servicing systems which converts some kind of energy into mechanical work. Engines are machines to change heat into motion. Depending on
the type of engine, power installation employed in present- day construction machinery, in tractors and trucks, can be subdivided into the following groups: steam, internal combustion, electric, pneumatic and hydraulic ones.
Steam engines and internal combustion engines are prime movers since they transform energy taken from fuel into mechanical work. Electric, pneumatic and hydraulic engines are known as secondary movers since they convert into mechanical work the energy produced by generators.
The main components of a steam power installation are a boiler and a steam engine. The boiler produces steam with required pressure. The steam engine transforms the energy of the expanding steam into mechanical work. This engine operates of simple expansion of steam. When used these engines are economical in work, have simple reversing, smooth starting and long life. But their large size and weight, high consumption of soft water and a very low efficiency restrict the application of steam engines in road building and transporting mechanisms.
Internal combustion engines are the principal power installations employed in mobile and self-propelled construction machinery as well as in trucks and tractors. They are very efficient under all working conditions and do not depend on the external sources of energy.
Most of these engines operate on four stroke cycle which is completed in time of two revolutions of the crankshaft. The four stroke cycle comprises the following operations:
1 – intake stroke; 2 – compression stroke; 3 – power stroke; 4 – exhaust stroke.
Internal combustion engines have the following advantages: small specific weight, quick start, high efficiency, etc. On the other hand, the internal combustion engines cannot carry high overloads, they cannot be started under load, which requires the use of clutches. Internal combustion engines have a shorter life compared with other engines. But they are a predominant type of power installations employed in construction machinery.
Electric power installations incorporate generators transforming mechanical energy into electrical one. The latter is then used to drive electric motors.
The widespread use of electric drives in road making and construction machines is due to their considerable economical and operational advantages as compared to other types of drives. They are always ready for service, easy to start, control and reverse, simple in design, small and light. Their efficiency can reach 0. 98 and they also allow a considerable saving in electric power.
Pneumatic and hydraulic power installations are employed for machine control systems, auxiliary devices and mechanical tools.
Exercise 3. Answer the following questions:
1. What are machines driven by?
2. What types of engines do you know?
3. What engines do we call prime movers?
4. What engines are known as secondary movers?
5. What advantages do steam engines have?
6. What are their disadvantages?
7. What advantages does the internal-combustion engine have?
8. What are the disadvantages of this type of engine?
9. What do electric power installations incorporate?
10. Why are electric drives widely used in construction machines?
11. What are the advantages of electric drives?
12. Where are pneumatic and hydraulic installations used?
Exercise 4. Translate the following words into Russian:
Power installation, service (n., v.), convert, heat, employ, steam engine, internal-combustion engine, transform, fuel, boiler, pressure, truck, expand, reverse, consumption, self-propelled, condition, complete (v., adj.), crankshaft, comprise, stroke, intake stroke, compression stroke, power stroke, exhaust stroke, specific weight, carry, clutch, reach.
Exercise 5. Translate from Russian into English:
Достигать, самоходный, сцепление, грузовик, потребление, силовая установка, задний или обратный ход, обслуживать, нести, условие, удельный вес, завершать, расширять(ся), превращать, давление, теплота, ход выпуска, коленчатый вал, котел, применять, рабочий ход, содержать, топливо, паровой двигатель, ход сжатия, преобразовывать, ход впуска, двигатель внутреннего сгорания, ход поршня.
Exercise 6. Match the following words (A) with their definitions (B):
«A»
1. employ
2. convert
3. boiler
4. steam
5. engine
6. reverse
7. clutch
8. truck
9. fuel
10. hydraulic
«B»
1. moved by the pressure of water or other liquids
2. opposite to forward direction
3. a large motor vehicle to carry heavy goods and material in large quantities
4. a container producing steam
5. a mechanism which allows working parts of machinery to be connected or disconnected smoothly
6. material that is used for producing power by burning
7. water in the state of a gas produced by boiling
8. to use
9. to change from one state, use or purpose into another
10. a piece of machinery which changes power from steam or fuel oil into motion
Exercise 7. Define the type of the subordinate clauses (subject, object, predicative, attributive, adverbial) and translate the sentences:
1. A machine is a device that performs some work.
2. Fuel vapour and air are mixed before they get into the cylinder.
3. We know that some useful energy is always lost when machines are used.
4. Machines are used because they develop greater forces than a man does.
5. Who designed the first lifting appliance is not known.
6. The problem is how the power can be increased.
7. We can increase productivity if we use a more efficient equipment.
8. One must be very careful there where the construction machines work.
9. We decided to install this engine in order that the capacity of the pump may be increased.
10. They couldn’t finish their work in time though they worked very hard.
Exercise 8. Translate the sentences; mind the sequence of tenses:
1. They reported that everything was ready to begin testing the device.
2. Designers believed that the giant crane would be suitable for various construction projects.
3. He said he had studied construction machinery at the university.
4. It was important to see if the metal would withstand high stress in work.
5. We wanted to know where that truck had been produced.
6. We were informed that the plan was being carried out successfully.
Exercise 9. Translate the following complex sentences, mind attributive clauses:
1. The equipment we work with is very economic and convenient.
2. The loads the giant cranes can lift are very large.
3. The main parts the tower crane consists of are the base, the tower, the jib and the rope with a hook.
4. Two main types of elevators our plant produces are those with deep buckets and with shallow ones.
5. The conveyor the builders worked with was the most modern one.
6. The laboratories our scientists work in are well equipped with modern devices and instruments.
Exercise 10. Translate the following complex sentences, mind the conditional clauses:
1. We should use some mechanisms or machines if we want to decrease the amount of force required to do some work.
2. If we had had a crane, we could have performed this work more quickly.
3. The mechanical efficiency of a machine would be higher if some force weren’t required to overcome friction.
4. The force required to do some amount of work can be reduced provided lesser force is applied over a longer distance.
5. The small gear is required to run a longer distance and in the process is able to exert a larger twisting force or torque, than would been the case if the gears were the same size.
6. The builders wouldn’t have improved the working process unless they had applied mechanical handling in some operations.
7. The crane can be installed at the building site provided the ground is specially strengthened.
8. The engine will be damaged unless the operator follows the instructions.
9. If the material had been more durable, this machine would have been more reliable.
10. If the engine were more powerful, the excavator would be able to work more efficiently.
