Английский язык: Сборник текстов и упражнений для студентов специальности "Эксплуатация судовых энергетических установок". Писарева Л.П. - 24 стр.

       All engine lubricating systems provide for oil storage. The reservoir to which the oil
drains from the bearings and cylinders is called a “sump”. Many engines have a wet sump that
is the oil stored in the crankcase itself or in the sump which is part of the crankcase. The vigor-
ous motion of the crankshaft and connecting rod creates air currents which agitate the oil sur-
face and produce crankcase “fog”. To avoid excessive lubrication of the cylinder walls caused
by this fog some engines use a dry sump. In this case a storage tank outside the engine is used.
       The complete pressure lubrication system includes an auxiliary pump driven by electric
motor, an oil strainer or filter to prevent dirt from passing into the engine, an oil cooler, to hold
temperature within the desired limit.

      VI. Describe the lubrication system.




                                           Lesson 8
                                     Engine Cooling System

      When fuel burns in the cylinders of a diesel engine only about one-third of the fuel’s heat
energy changes into mechanical energy and then leaves the engine in the form of brake horse-
power. The rest of the heat shows up in hot exhaust gases, frictional heat of the rubbing surfac-
es and heating of the metal walls which form the combustion chamber, namely, the cylinder
head and piston.
      The cooling system job is to remove the unwanted heat from these pasts so as to prevent:
      1. Overheating and resulting breakdown of the lubricating oil film which separates the
engine rubbing surfaces.
      2. Overheating and resulting loss of strength of the metal itself.
      3. Excessive stresses in or between the engine parts due to unequal temperature.
      Cylinder heads and cylinders are generally provided with jackets through which cooling
water is circulated. Pistons transfer their heat to the cylinder walls and to the lubricating oil.
Many engines use oil coolers to remove the heat in the lubricating oil.
      The heat balance of an engine and the amount of heat absorbed by the cooling water
vary with the type of engine and the design of cylinders, exhaust manifold, pistons lubricat-
ing oil system and any other equipment which may be cooled directly or indirectly by the
circulating water.

                                     Closed Cooling System

      In closed cooling systems the jacket water is recirculated through closed heat exchangers.
A heat exchanger is a device that transfers heat from one fluid to another. Thus, in closes sys-
tems, the same water remains in the system indefinitely and is recooled without exposure to air.
The heat exchanger may be water-to-water (shell-and-tube type) or water-to-air (radiators and
evaporative coolers). With water-to-water heat exchanger the secondary water may pass
through only once if the supply is ample and there is no need to conserve it. Scale deposits are
not as serious in heat exchangers can be easily cleaned.
      In the radiator type of a closed system air blown by a fan cools water within the tubes of
the radiator. The water is not exposed to the air and there is no evaporation.
      Both salt and fresh water are used for cooling system. When a separate fresh-water sys-
tem is employed, an extra fresh-water cooler and pump for circulating sea water through this
cooler must be available. The advantages of the separate fresh-water system are that higher
temperatures of the cooling water can be used; salt-water fittings are not necessary beyond the
fresh-water cooler, muddy (dirt) and other objectionable over-board water cannot get into the
engine jackets, main circulating-water piping and circulating-water pumps.
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