Дизельные двигатели. Эксплуатация и обслуживание = Diesel engines. Operation and maintenance. Практикум
.pdf4.There is no … of vapor on the suction side of the fuel pump. a) formation
b) formed c) forming
5.Fuel … into combustion chamber through a number of nozzle orifices.
a) is spraying b) sprays
c) is sprayed
4. Make up sentences using their parts (use verbs in the correct Tense and Voice):
1)system / steam / to employ / preheating / up / 7 kg / sq.cm. / to;
2)lines / drain / leakage / for / fuel / to heat / partially;
3)transfer / fuel / pump / to drive / by / electric / an / motor / separately;
4)to be / there / formation / no / vapor / of / suction / on / side / of / pump / the;
5)valve / non-return / to situate / fuel / between / pump / overflow / and / line.
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6.COOLING SYSTEM OF A DIESEL ENGINE
1.Read and translate the text. Pay attention to new phrases.
Cooling System of a Diesel Engine
The principle function of the cooling system is to dispose of the heat transferred from the burning fuel to the metal adjacent to the combustion chamber, but for convenience it is usually extended and put to uses, such as cooling the scavenging air, lubricating oil, exhaust manifold, crosshead guides, etc. All of these points of application may be included in a single system and sea water and fresh water used as the cooling medium or several independent circuits may be used. The most often used cooling system is an enclosed fresh water system. In this case sea water is used for cooling fresh water, oil and scavenging air.
The water that enters the bottom of each cylinder jacket flows upward, passes into the cylinder head, then through the exhaust valve cage and into a pipe leading to the exhaust manifold jacket, whence it is led to the thermostat. The latter delivers part of the water to the cooler and the rest of it to the circulating pump to be recirculated. If there is a temperature rise of cooling water, the thermostat directs greater part of the water to the cooler and lesser part is to be recirculated.
In numerous cases the pistons are cooled with fresh water or oil, in which case the piston system is, of course, separate from the jacket system. A separate circulating pump is used and the oil or fresh water leaving the pistons passes through coolers and into a large tank, to be recirculated. In some of the Burmeister & Wain installations cooling of the piston is done with oil and that of the rest of the engine with fresh
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water, sea water being used only in the coolers, through which the fresh water and oil are passed after leaving the engine.
It will be readily seen that the salt-water method is the simplest arrangement because of the necessity for fewer pumps and the elimination of water coolers and storage tanks, but the use of fresh water tends to reduce the trouble due to scale, sediment and corrosion. Cooling the pistons with oil eliminates troubles due to leakage of water into the lubricating oil.
dispose of the heat transferred from the burning fuel to the metal
adjacent to the combustion chamber
scavenging air
exhaust manifold
crosshead guides
independent circuit
enclosed fresh water system
enter the bottom of each cylinder jacket
flow upward
pass into the cylinder head
exhaust valve cage
exhaust manifold jacket
circulating pump
temperature rise of cooling water
separate from the jacket system
the simplest arrangement
necessity for fewer pumps
reduce the trouble due to scale, sediment and corrosion
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eliminate troubles
leakage of water into the lubricating oil
2.Fill in the gaps in the sentences with words or word combinations from the word box: scavenging air; an enclosed fresh water system; burning fuel; the jacket system; circulating pump; scale, sediment and corrosion:
1.The principle function of the cooling system is to dispose of heat transferred from … to metal adjacent to combustion chamber.
2.The most often used cooling system is … .
3.Sea water is used for cooling fresh water, oil and … .
4.Thermostat delivers part of the water to the cooler and the rest of it
to … .
5.Pistons are usually cooled with oil and the piston system is separate from … .
6.The use of fresh water cooling reduces the trouble due to … .
3. Choose the correct word:
1.The water … the bottom of the cylinder jacket and flows upward. a) enters
b) is entered c) entering
2.The water passes through the exhaust valve cage into a pipe … to the exhaust manifold jacket.
a) led b) leads
c) leading
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3.If there is a temperature rise of cooling water, thermostat delivers the greater part of it to the cooler and the lesser part is to be … .
a) recirculation b) recirculating c) recirculated
4.Sea water is only … for cooling fresh water and oil.
a)using
b)used
c)uses
5. The all salt-water method is the simplest … because of fewer number of pumps and elimination of water coolers and storage tanks.
a)arrangement
b)arranged
c)arranging
4. Make up sentences using their parts (use verbs in the correct Tense and Voice):
1)function / system / principle / cooling / of / to dispose of heat /
to be;
2)points / all / application / of / to include / in / a single cooling
system;
3)to use / independent / circuits / cooling / several;
4)through / water / coolers / to pass / fresh / into / recirculation / for / a large tank.
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COOLING
1. Read and translate the text. Pay attention to new phrases.
Cooling
Cooling of engines is achieved by circulating a cooling liquid around internal passages within the engine. The cooling is thus heated up and is in turn cooled by sea water circulated cooler. Without adequate cooling, certain parts of the engine which are exposed to the very high temperatures, as a result of burning fuel, would soon fail. Cooling enables the engine metals to retain their mechanical properties. The usual coolant used is fresh water: sea water is not used directly as a coolant because of its corrosive action. Lubricating oil is sometime used for piston cooling since leaks into the crankcase would not cause problems. As a result of its lower specific heat however about twice the quantity of oil compared to water would be required.
Fresh Water Cooling System
A fresh water cooling system is divided into two separate systems: one for cooling the cylinder jackets, cylinder heads and turboblowers; the other for piston cooling. The cylinder jacket cooling water after leaving the engine pauses to a sea-water circulated cooler and then into the jacket-water circulating pumps. It is then pumped around the cylinder jackets, cylinder heads and turbo-blowers. A header tank allows for expansion and water make-up system. Vents are led from the engine to the header tank for the release of air from the cooling water. A heater in the circuit facilitates warming of the engine prior to starting by circulating hot water. The piston cooling system employs similar
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components, except that a drain tank is used instead of a header tank and the vents are then led to high points in the machinery space. A separate piston cooling system is used to limit any contamination from piston cooling glands to the piston cooling system only.
Sea Water Cooling System
The various cooling liquids which circulate the engine are themselves cooled by sea water. The usual arrangement uses individual coolers for lubricating oil, jacket water, and the piston cooling system, each cooler being circulated by sea water. Some modern ships use what is known as a “central cooling system” with only one large sea-water- circulated cooler. This cools a supply of fresh water, which then circulates to the other individual coolers. With less equipment in contact with sea water, the corrosion problems are much reduced in this system.
From the sea suction one of a pair of sea-water circulating pumps provides sea water which circulates the lubricating oil cooler, the jacket water cooler and the piston water cooler before discharging overboard. Another branch of the sea water main provides sea water to directly cool the charge air (for a direct-drive two-stroke diesel).
The sea water circuit is made up of high and low suctions, usually on either side of the machinery space, suction strainers and several sea water pumps. The sea water is circulated through the central coolers and then discharged overboard. A low temperature and high temperature circuit exist in the fresh water system. The fresh water in the high-temperature circuit circulates the main engine and may, if required, be used as a heating medium for an evaporator. The low temperature circuit circulates the main engine coolers, the lubricating
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oil coolers and all other heat exchangers. A regulating valve controls the mixing of water between the high temperature and low temperature circuits. A temperature sensor provides a signal to the control unit which operates the regulating valve to maintain the desired temperature setting. A temperature sensor is also used in a similar control circuit to operate the regulating valve which controls the bypassing of the central coolers.
It is also possible, with appropriate control equipment, to vary the quantity of sea water circulated by the pumps to almost precisely meet the cooler requirements.
cooling of engines is achieved by circulating a cooling liquid
exposed to the very high temperatures
retain mechanical properties
cause problems
header tank
release of air
contamination from piston
sea suction
heat exchanger
temperature sensor
appropriate control equipment
precisely meet the cooler requirements
high-temperature circuit
discharge overboard
vary the quantity of sea water
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AFTER-READING TASKS
1. Replace the gaps by a word from the list.
Troubles, necessary, function, uses, medium, application, combustion chamber, coolers, fresh.
1.The principles … of the cooling system is to dispose of heat.
2.The cooling system is to put to many … .
3.All these points of … may be included in a single system … .
4.Sea water and fresh water are used as the cooling … .
5.The metal adjusted to the … … is greatly heated.
6.Separated branches lead to the oil … and shaft bearings.
7.The oil or … water leaving the piston passes through coolers into a large tank, to be recirculated.
8.When sea water cooling is used, there is the … of fewer pumps.
9.Fresh water tends to reduce the … due to scale, sediment and corrosion.
2. Answer the questions.
1.What’s the cooling system’s job?
2.What are cylinder heads and cylinders provided with?
3.Where do pistons transfer their heat?
4.What is the heat exchanger?
5.What types of heat exchangers do you know?
6.What should you know about the temperature of cooling water?
7.What can a large amount of cold water supplied into a hot engine
cause?
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3.Think and answer. Give extended answers.
1.Why is it necessary to cool the engine?
2.What cooling medium can be used?
3.Why is it preferable to cool the piston with oil?
4.Why is sea water used generally in coolers?
4.Read and translate the following word combinations.
• cooling system;
• principle function;
• to dispose heat;
• combustion chamber;
• scavenging air;
• elimination of water coolers;
• to reduce the troubles;
• simplest arrangement;
• storage tank;
• exhaust manifold;
• cylinder jacket;
• sea water method.
5.Tell about the cooling system.
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