Pressure – charging

Pressure – or super – charging is a process of increasing the power output of an engine. If during the working cycle the amount of air supplied into the cylinder is increased it will enable to burn more fuel and as a result more power is received (achieved, obtained). To supply more air it should be compressed. The air is compressed by a turboblower installed just after the engine. This turboblower consists of a compressor and a turbine which is driven by the exhaust gases leaving the engine.

The exhaust turboblower system increases the total efficiency of the engine, its reliability and reduces the maintenance costs.

There are two types of the turbo-charging system. The main engines can operate on the pulse or impulse system and constant-pressure system (the system producing constant pressure of the exhaust gases). With impulse system the construction is rather complicated. It means that engines with more than three cylinders must be fitted with more than one turboblower or the turboblower must have multi-inlet casings which have separate passages to the turbine nozzles. And the efficiency of the turbine reduces. But this system is highly efficient at partial loads of the engine operation.

For constant pressure operation all cylinders exhaust into a common receiver (manifold) where the constant pressure is maintained (kept). The construction is simplified. It allows greater flexibility in positioning the turboblower. But the system is insensitive to changes in engine operating conditions (The system is less efficient at part-load conditions).

amount	[q'mQunt]	количество
enable	[i'neibl]	смочь, быть способным
burn	[bWn]	сжечь
receive	[ri'sJv]	получать
installed	[in'stLl]	устанавливать
drive	['drQiv]	приводить(в движение)
reliability	[ri"laiq'biliti]	надежность
maintenance	['meintinqns]	эксплуатация
costs	[kOsts]	расходы
constant	['kOnstqn]	постоянный
mean	[mJn]	означает
multi-inlet	[mAlti 'inlet]	с несколькими входами
separate	['seprit]	отдельный
nozzle	[nOzl]	сопло
partial	['pRSql]	частичный
common	['kOmqn]	общий
simplify	['simplifQi]	упрощать
flexibility	["fleksi'biliti]	гибкость
insensitive	[in'sensitiv]	нечувствительный

Fuel Oil System

During normal operation on heavy oil at sea, the oil is taken from the bottom tanks, where it is stored. First it is supplied through a heater and next through the centrifuge for purification. It may then pass through a cooler, before it gets into the steam-heated heavy oil service tanks. There are usually two such tanks: one tank is in use and the other is being filled. (These tanks are heated to a moderate temperature and self-closing drain valves are fitted to remove any water or sludge, which may settle out.) The fuel oil is taken from the service tank in use by pumps and discharged (at low pressure) to the fuel oil heater. These pumps should be in duplicate. A relief valve on the pumps will return excess pressure to the system. A viscosity regulator is fitted at the heater outlet. It automatically controls the temperature of the oil fuel leaving the heater because it is necessary to maintain the correct fuel viscosity. Then the oil is discharged through a fine filter to the (suction side of) the main engine fuel pump. (A pressure control valve is fitted in the system and excess oil is returned either to the heavy oil service tanks or to a bottom tank.)

A diesel fuel tank is included in the system and it is connected to the primary pump suction line through a change-over valve. By operating this valve the engine may be operated on diesel oil.