Английский язык: Сборник текстов и упражнений для студентов специальности "Эксплуатация судовых энергетических установок". Писарева Л.П. - 18 стр.

taken by the piston and results in a side pressure against the wall of the cylinder. To provide
adequate bearing so that this side pressure will have a low unit value, the piston is provided
with an extended skirt, or trunk, from which this method of construction gets its name. This
construction has the advantages that it reduces engine height and is cheaper than crosshead
construction. It is universally used for small engines and in some cases for engines of quite
large power.
      The crosshead type is usually confined to large engines. The piston is connected to the
crosshead by a piston rod and the crosshead is in turn connected to the crankpin by a connect-
ing rod. This construction has the advantage of relieving the piston and cylinder wall of side
thrust and in the four-cycle engine permits to use a short piston. In the case of a two-cycle en-
gine the extended piston skirt is still required in order to keep the exhaust and scavenging ports
closed during the upstroke of the piston. This construction is penalized by the extra height re-
quired to make room for the crosshead and piston rod.

      1. How is the piston attached to the upper and lower ends of the connecting rod in the
trunk-piston engine?
      2. What advantages does this engine have?
      3. What advantage does the crosshead type engine have?




                                           Lesson 6
                                     Fuel Injection System

       In an internal combustion engine the combustion process is rather complicated. All such
engines operate with intermittent combustion. A charge of fuel is mixed with the air and ig-
nited in the engine cylinder. For introducing the fuel charge into the cylinder if a Diesel engine
fuel injection system is in general use.
       Each cylinder has its own fuel injection pump connected directly through piping to the
spray nozzle of the individual engine cylinder. In this system oil is drawn into the individual
pump through the suction valve. When the nose of the fuel cam strikes the lower end of the
pump plunger, the oil in the pump barrel is forced out through the discharge valve. The pipe-
line is kept filled with oil, so when a new charge if oil enters the piping from the fuel pump, an
equal amount is pushed out of the pipe into the spray valve mounted in the cylinder head. This
oil acts upon the surface created by the design of the spray valve needle. The oil then issues
through openings into the engine cylinder.
       The amount of oil the pump delivers to the engine is controlled by the governor – the
particular type of control depends upon the pump design. On some, the pump stroke is varied
to control the oil charge, on others a bypass valve allows part of the oil to flow back into the
pump suction line.
       The spray valve may have a spring – loaded differential needle which is lifted by the
oil pressure as soon as the pump starts its delivery stroke. The fuel valve may also contain
only a light check valve to prevent the cylinder gases passing through the valve, this is
called an open nozzle.


                                          Vocabulary

      to operate=to run                             работать
      intermittent                                  пульсирующий
      to be in general use                          обычно использовать
      fuel injection pump                           THBD
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