Английский язык: Сборник текстов и упражнений для студентов специальности "Эксплуатация судовых энергетических установок". Писарева Л.П. - 27 стр.

                                         Lesson 9
                                   Turbochanging System

       To increase the available output of a diesel engine of given main dimensions the engine
is connected with one or more exhaust-gas turbine-driven compressors and air coolers: an ar-
rangement which is generally known as turbocharging. The only difference between an engine
equipped in this manner and a normally aspirated engine is that the former operates at an in-
creased pressure level. The exhaust gas drives a turbine which, in turn, drives a centrifugal
compressor which increases the air pressure before the reciprocating scavenging air pumps.
Since the density of scavenging air is increased by the pressure rise in the turbo-compressor
and the subsequent cooling, a larger quantity of air by weight is entrapped in the cylinder
which, in turn, permits the combustion of a larger quantity of fuel and gives a higher available
output. Each turbo-charger consists of a single stage or two-stage centrifugal compressor and
axial turbine which are assembled on the same shaft. Rotation of the rotor depends on the en-
gine load and scavenging resistance, since the unit is connected to the engine without any me-
chanical transmission. The turbo-charged engine is maneuvered in the same manner as a nor-
mally aspirated engine.
       MAK engines use only pulse turbocharging and to meet this requirement cylinder
numbers which permit good grouping of the turbocharger connections are employed. A dis-
tinction is made between three-pulse charging for 6 – 9 and 12 cylinder engines with cams
specially timed for three-pulse mode and four-pulse charging for 8 and 16 cylinder engines
with completely different timings for the four-pulse mode. The disadvantage of pulse charg-
ing for highly-supercharged engines compared with the constant pressure charging is the fact
that during the full load the single-stage exhaust turbine can only utilize the lower part of the
very high exhaust gas pressure wave. But this is the advantage at part load or reduced power.
Pulse charging has a further advantage that the engine can adapt very quickly to sudden
changes in load.
       With exhaust gas turbo-charging it has proved possible to triple the power obtained from
the swept volume of a diesel engine.


                                          Vocabulary

     available                                      имеющийся в наличии
     output                                         выходная мощность
     dimension                                      размер, измерение
     arrangement                                    устройство
     turbocharging                                  турбонаддув
     to equip                                       оборудовать, оснащать
     normally aspirates engine                      двигатель без наддува
     former                                         первый (из ранее упомянутых)
     in turn                                        в свою очередь
     reciprocating pump                             поршневой насос
     density                                        плотность
     stage                                          ступень
     axial turbine                                  аксиальная турбина
     to assemble                                    собирать
     resistance                                     сопротивление
     transmission                                   передача
     to maneuver                                    маневрировать
     pulse                                          пульсирующий
     meet smb’s requirement                         отвечать требованиям

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