galyatova_v_n_lelet_i_a_angliyskiy_yazyk

4.Втулки должны проверяться на износ.

5.Их можно заменить, если необходимо.

6.Зазоры должны регулироваться.

7.Центровка коленвала должна корректироваться, если не­ обходимо.

Unit II.

Structural Parts of a Diesel Engine

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Text A.

Structural Parts of a Diesel Engine

The principal components of an internal combustion engine may be divided into two principal groups - parts and systems. The main parts of an internal combustion engine may be further divided into structural parts and moving parts.

The frame of the modem diesel may include such parts as the cylinder block, crankcase, bedplate or base, sump or oil pan, and end plates.

The engine frame part which supports the engine's cylinder liners and cylinder heads is called the cylinder block.

The engine frame part, which serves as a housing for the crank­ shaft, is called the crankcase.

In large engines of early design, the support for the main bearings was provided by a bedplate. In some large engines of more modem de­ sign the support for main bearings is provided by a part called the base.

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Since lubrication is essential for proper engine operation, a reser­ voir for collecting and holding the engine's lubricating oil is a necessary part of the engine structure. The reservoir may be called a sump or an oil pan, depending upon its design, and is usually attached directly to the engine. However, in some engines, the oil reservoir may be located at some point relatively remote from the engine; such engines may be called dry sump engines.

Some engines have flat steel plates attached to each end of the cy­ linder block. End plates add rigidity to the block and provide a surface to which may be bolted housings for such parts as gears, blowers, pumps and generators.

Many engines, especially the larger ones, have access openings in some parts of the engine frame. These openings permit access to the cy­ linder liners, main and connecting rod bearings, injector control shafts, and various other internal engine parts. Access doors (sometimes called covers or plates) for the openings are usually secured with hand wheel or nut-operated clamps and are fitted with gaskets to keep dirt and foreign material out of the engine's interior.

The cylinder assembly consists of the head, the liner, the studs and the gasket; it provides a gas and liquid-tight space. Practically all diesel engines are constructed with replaceable cylinder liners. The liners or bores must be sealed tightly to form the combustion chambers. The space at the c9mbustion end of a cylinder is formed and sealed by a cy­ linder head, which is a separate unit from the block.

A number of engine parts, which are essential to engine operation, may be found in or attached to the cylinder head. The cylinder head may house intake and exhaust valves, valve guides and valve seats. Rocker arm assemblies are frequently attached to the cylinder head.

The fuel injection valve is almost always in the cylinder head. Cy­ linder heads of a diesel engine may also be fitted with air starting valves, indicator and blow down valves, and safety valves. Large diesel engines generally have one cylinder head for each cylinder.

In most cases, the seal between the cylinder head and the block de­ pends principally upon the studs and gaskets. The studs, or stud bolts, secure the cylinder head to the cylinder "block. A gasket between the head and the block is compressed to form a seal when the head is pro­ perly tightened down.

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Exercise I.

Answer the questions

1.What structural parts does the engine frame include?

2.What portion of the frame is called the crankcase?

3.What parts may provide the support for the main bearings?

4.What do we call the reservoir that holds the lube oil collected in the lower part of some engines?

5.Can you explain the term "dry sump engine"?

6.What is the double function of the end plates?

7.What arrangements make the examination of the bearings and other internal parts of a diesel engine possible?

8.What is a gasket?

9.What are the parts of the cylinder assembly? Are all of them replaceable?

10.What valves may be fitted in the cylinder head?

11.Are rocker arm assemblies attached to the cylinder heads of all types of diesel engine?

Exercise II.

Speak of the structural parts of a diesel engine.

Exercise III.

Read and translate text В in written form.

Text B.

Cylinder Block

Cylinder block is a box-shaped iron casting divided by cross parti­ tions into six sections accommodating the cylinder liners. The latter have shoulders for resting on the upper plate of the cylinder block and are centered by girths.

Rubber rings in lower girth ensure an air-tight joint between the receiver and the crankcase.

The upper part of the cylinder block forms a trough with the bea­ rings for the camshaft. The space under the trough is used as an addi­ tional volume for the scavenging air of the air receiver. The side and end walls of the cylinder block are provided with machined surfaces for mounting the engine accessories.

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The wall of the cylinder block receiver at the camshaft side has ports used for inspecting the cylinder liners and installing the liner wa­ ter-cooling pipes. The receiver wall at the exhaust side has ports through which the scavenging air is forced in by the air blowers.

The cylinder block is secured to the bed frame by means of the cy­ linder block lugs, which have holes for the fitted bolts and holes for ordinary bolts.

The tie rods, holding together the cylinder block and the bed frame extend through holes.

Each cylinder head is fastened by means of the tie rods inserted into eight holes located in the cylinder block upper plate.

To prevent undue rise of gas pressure in the receiver, the hatch lids are provided with built-in the relief valves, which are identical in design with the safety valves in the lids of the bed frame hatches.

The valve, consist of a body, a disc, a bolt, a spring and a sealing ring. The spring tension is adjusted for a pressure of 1,7 kg/cm2 in the receiver.

The gases escaping through the valve are directed down by the shield. The opening for escaping gases in the cover is dosed with a safety screen.

Exercise IV.

Put 10 questions to the text (5 types).

Exercise V.

Translate into Russian paying attention to Participle II as an At­ tribute.

1.There is an exhaust pipe connected” to the cylinder.

2.The liner has a flanged upper end and a thickened lower end.

3.The foundation is a strong framework designed to tie together the light component elements of the engine.

4.The A-frame consists of a pair of cast iron columns usually of box section, joined to form roughly the shape of the letter A.

5.The shells of the main bearings are of cast iron (or cast steel) with rubbing surfaces lined with high grade babbit metal.

6.The elongated ends of these tie rods are used for attaching a special device intended for lifting the assembled engine.

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7.The cylinder head and bed frame tie rods as well as their nuts are the most stressed parts of the engine.

8.The eighth bearing is mounted on bracket bolted to the face end of the cylinder block.

9.Inspection and cleaning of the cylinder head water jacket may be performed through holes located on the side surface and dosed with covers installed on rubber gaskets.

10.Cylinder block is a box-shaped iron casting divided by cross partitions into six sections accommodating the cylinder liners.

Exercise VI.

Translate into English.

1.Продувочный воздух подается через окна на стенке ресиве­ ра с помощью воздуходувок.

2.Блок цилиндров и фундаментная рама стягиваются анкер­ ными связями.

3.Стравливающие клапаны вмонтированы в крышки люков.

4.Выходящие из клапана газы направляются вниз щитком.

5.Окно для выхода газов в крышке закрыто предохра­ нительной сеткой.

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Text A.

Engine Air Systems

Parts and accessories, which supply the cylinders of an engine with air for combustion, and remove the waste gases after combustion, are called intake and exhaust systems.

In the intake systems of all modern 2-stroke cycle engines and some 4-stroke cycle engines, a device, usually a blower is installed to increase the flow of air into the cylinders. This is accomplished by the blower compressing the air and forcing it into an air box or manifold (reservoir) which surrounds or is attached to the cylinders of an engine. Clearing the cylinder of the gases of combustion is called scavenging.

An increase in air flow into the cylinders of an engine can be used to increase power output, in addition to being used for scavenging. Since the power of an engine is developed by the burning of fuel, an increase of power requires more fuel; the increased fuel, in turn, requires more air, since each pound of fuel requires a certain amount of air for combus­ tion. Supplying more air to the combustion spaces is called superchar­ ging. In some 2-stroke cycle diesel engines, the cylinders are super­ charged during the air intake simply by increasing the amount and pres­ sure of scavenge air. The same blower is used for supercharging and scavenging. Supercharging a 4-stroke cycle diesel engine requires the addition of a blower to the intake system.

The system, which functions to convey gases away from the cylin­ ders of an engine, is called the exhaust system. In addition to this princi­ pal function, an exhaust system may be designed to perform one or more

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of the following functions: muffle exhaust noise, quench sparks, remove solid material from exhaust gases, and furnish energy to a turbine-driven supercharger.

Exercise I.

Answer the questions

1.What systems are spoken about in the text?

2.What is scavenging?

3.What is supercharging and how is it provided?

4.How is the supercharger driven?

5.What are the functions of the exhaust system?

Exercise II.

Speak of the Engine Air Systems.

Exercise III.

Read and translate text В in written form.

Text B.

Pressure-Charging

In an engine which draws its combustion air directly from the at­ mosphere the density of the sucked air charge is approximately the same as the ambient air density. As this air density determines the maximum weight of fuel that can effectively be burned per working stroke in the cylinder, it also determines the maximum power that can be developed by the engine. If, therefore, the charge-air density is increased by instal­ lation of a - compressor between the ambient air and the cylinder, then the weight of air per working stroke is increased and thereby the greater weight of fuel can be burned in the same cylinder, with proportionate in­ crease of power.

It is essential that each cylinder must be scavenged before a fresh charge of air is compressed otherwise this fresh air charge is contami­ nated by residual exhaust gases from the previous cycle. Further, the cy­ cle temperature is unnecessarily high if the air-charge is heated by mi­ xing with residual gases and by contact with hot cylinders and pistons.

The power for driving the compressor has an important influence on the operating efficiency of the engine. For example, it is uneeono-

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mical to drive the compressor directly from the engine by chain gear or other mechanism because some of the power is absorbed. But if the compressor is driven by the heat energy in the engine exhaust gases - about 35 per cent of the total heat energy in the fuel is discharged to the exhaust gases - then an increase of power can be obtained which is pro­ portional to the increase in the charge air density. This is the basic prin­ ciple of exhaust turbo-charging.

Exercise IV.

Put 10 questions to the text (5 types).

Exercise V.

Change Passive into Active.

1. Fuel must be divided into a fine spray when it enters the cylin­

der.

2.Diesels are to be supplied with cooling systems to make their operation reliable.

3.Ports of a two-stroke engine must be covered and uncovered by

the piston at certain positions.

4.Air can be delivered by a turbo-charger at a pressure higher than the atmospheric pressure.

5.All bearings must be supplied with lubricating oil.

6.The power of an engine may be increased by supercharging

from 20 to 300 per cent.

7.The power of an engine can be determined by the density of the sucked air charge.

8.The turbo-charger must be installed between the ambient air and

the cylinder.

9. The weight of fuel that can be burnt in the cylinder is deter­ mined by air charge density.

10. A compressor must be used to compress the air charge.

Exercise VI.

Translate into English.

1.Плотность воздушного заряда увеличивается при установ­ ке компрессора.

2.Цилиндры необходимо продувать до подачи свежего заря­

да воздуха.

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