Mechanical refrigerating system can be divided into two classes:the direct one and the indirect one.In the  former,the refrigerant directly takes away the heat from the substance to be cooled.That is to say the heat exchange takes place directly between the surrounding substance and the refrigerant,while in the latter,cooling liquids,such as cold brine and water,are employed as a medium to carry out the transfer of heat between the refrigerant and the surrounding substance to be cooled.

In the refrigerating system,the refrigerant becomes after the heat exchange takes place.

In addition to the main parts,there are a number of systems necessary for the operation of the engine,such a the starting system served by the air compressors and air bottles,the fuel-injection system with its camshaft drive, the cooling system and the lubricating system.Besides,the high pressure turbocharging system is also an important part to heavy engines.

The starting system is usually operated by the_____.

Special care should be taken to stop leaks of all descriptions immediately after they occur.Vital components of the engine should be frequently examined.The crankcase cover should never be allowed to open for investigation when the engine is running.And it should not be opened until at least fifteen minutes after the engine stops.Lights of high voltage or naked lights should never be used for fear of fire or explosion.

"Leaks of all description"in the passage means_____.

Satisfactory and proper operation of the engine depends not only on correct manoeuvring but also on how well it is kept in order.Regular maintenance of the engine helps a lot in preventing early wear of parts and in ensuring a long  service  as  well  as  the  working  efficiency  of  the  engine.With  various  types  of  engines,of  course,the maintenance and overhaul are different.Instruction books are to be referred to whenever necessary.During overhaul the safety rules have to be observed as required in order to prevent the danger of accidents.

What is the possible title of this passage?

The engine is provided with a governor which is designed to regulate the engine's speed by adjusting the quantity of oil injected.When the engine runs at a speed higher or lower than is set,the governor will act automatically and reduce or increase the fuel oil supply so that the engine speed can be adjusted.The flyweight type governor with an adjustable spring is one of those most commonly used for large-sized marine engines.The regulating movements of the flyweights are transmitted to the fuel pump regulating rods by means of a built-in servomotor.The oil pressure necessary for operating this governor is delivered by a gear-type oil pump built into the governor.

What is the function of a governor?

The turbochargers are placed a the level of the top gallery.They rest on the charge-air receiver which runs along the whole length of the engine and is bolted to the cylinder block.The turbocharger comprises a gas turbine,driven by the engine exhaust gases,a blower,which draws ai from the ambient atmosphere and discharges to the air inlet manifold on the engine.The air coolers are built into the charge-air receiver and can be dismantled and lifted out. The outer part of the charge-air receiver is undivided and serves as the scavenge-air duct,while the inner part is divided according to the widths of the cylinders and forms the buffer spaces for scavenging the cylinders.

Where is the turbocharger located?