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1、 UNIT 5DIESEL FUEL INJECTIONTEXT AOverview of Conventional Diesel Fuel Injectionand Common Rail Injection Systems PROFESSIONAL ENGLISHConventional Diesel Fuel Injection System components Common Rail Injection Systems System components Injector operation 本次课学习内容本次课学习目标l掌握柴油机喷油系统的组成l掌握主要部件的型式及原理l掌握有关的
2、专业名词与术语l了解翻译技巧省略NEW WORDSparticlep:tikln.微粒，颗粒微粒，颗粒clogklgv.&n.阻塞，堵塞阻塞，堵塞nozzlenzln.喷嘴喷嘴traptrpn.圈套，陷阱，捕集器圈套，陷阱，捕集器plungerplnn.柱塞，活塞柱塞，活塞variationverieinn.变化，变更，变种，变调变化，变更，变种，变调protrudeprtru:dv.突出，伸入突出，伸入solenoidsulinidn.螺螺线线管管，电电磁磁线线圈圈铁铁，阀阀，开开关关energizeendaizv.供给供给能量，通电，励磁能量，通电，励磁depressiondiprenn.
3、消消沉沉，萧萧条条；低低气气压压，凹凹陷陷，凹坑凹坑stackstkn.堆堆,一堆；一堆；v.堆叠堆叠piezoelectricpaii:zuilektrik a.压电的压电的PHRASES AND EXPRESSIONSfuel pump燃油泵燃油泵fuel filter燃油滤清器燃油滤清器injection pump喷油泵喷油泵fuel line燃油管燃油管light truck轻型货车轻型货车inline injection pump直列式喷油泵直列式喷油泵distributor injection pump分配式喷油泵分配式喷油泵delivery valve出油阀出油阀spray pa
4、ttern喷注形状喷注形状glow plug预热塞预热塞intake air heater进气加热器进气加热器precombustion chamber预燃室预燃室fuel rail油轨油轨pressure shoulder承压锥面承压锥面solenoid-type injector电磁式喷油器电磁式喷油器piezoelectric injector压电式喷油器压电式喷油器Typical diesel fuel injection system components include the fuel tank,fuel pump,fuel filter,injection pump,injec
5、tors,and the necessary fuel lines(Fig.5-1).Fig5-1 A conventional diesel fuel injection systemConventional Fuel Injection System Fuel Filter.Diesel fuel must be kept clean to avoid injector system trouble.Very small particles are enough to clog injector nozzles.Diesel fuel systems typically use one o
6、r more filters to trap dirt and other deposits.Injection Pump.Due to the high compression(around 22:1)used in diesel engines,the diesel injection pump must be capable of producing high pressures.There are a number of injection pump designs.The most commonly used automobile and light truck diesel inj
7、ection pumps are classified as inline or distributor.Conventional Fuel Injection SystemConventional Fuel Injection SystemThe inline injection pump uses a separate cylinder-plunger-cam unit for each cylinder.These units are contained in a straight row in a common housing.In the distributor injection
8、pump,a single double-plunger type pump serves all injector outlets.A single delivery valve is located in the rotor.Conventional Fuel Injection System Injector.There are many different injector designs,but all are a variation of two basic types-inward opening and outward opening.Diesel spray patterns
9、 will vary depending upon engine design.Glow Plug and Intake Air Heaters.To aid in igniting the compressed air-fuel mixture during cold starting,diesel engines use glow plugs and intake air heaters.The glow plug is an electrically operated device that protrudes into the precombustion chamber.On late
10、r engines,the glow plugs are turned on and off automatically.Intake air heaters warm the air as it passes through on its way to the intake manifold.The heater element is a wire mesh that is electrically heated.The computer energizes the heater element before cranking.Conventional Fuel Injection Syst
11、emCommon Rail Injection System Newer diesel engines are equipped with common rail injection systems(Fig.5-2 and Fig.5-3).Common rail systems are direct injection(DI)systems.The injectors nozzles are placed inside the combustion chamber.The piston top has a depression where initial combustion takes p
12、lace.The injector must be able to withstand the temperature and pressure inside the cylinder and must be able to deliver a fine spray of fuel into those conditions.These systems have a high pressure fuel rail connected to individual injectors.The injectors are controlled by a computer that attempts
13、to match injector operation to the operating conditions of the engine.Fig.5-2 Common rail(CR)systemConventional Fuel Injection SystemConventional Fuel Injection SystemFig.5-3 Bosch third-generation common rail system with piezoelectric injectors The injector facilitates precise control of the start
14、of injection and injected fuel quantity as well as pre-and post-injection.Injector closed(rest state).The fuel flows through the fuel-inlet passage into the valve control chamber and to the injection-nozzle pressure shoulder.The discharge throttle is closed by the valve ball.The pressure above the v
15、alve control plunger in the valve control chamber generates a force which is greater than the opposing force which acts on the nozzle-needle pressure shoulder1.The nozzle needle thus remains closed,regardless of the rail pressure applied at the injector(see Fig.5-4).Conventional Fuel Injection Syste
16、mConventional Fuel Injection Systemon its pressure shoulder.The nozzle needle opens and fuel is injected,see Fig.5-4.Injector closes(end of injection).When the solenoid valve is no longer supplied with power by the FCU,the valve spring forces the valve ball onto its seat.As a result,the discharge throttle is closed and the fuel pressure builds up again abruptly in the valve control chamber.The force acting on the valve control plunger and the force of the nozzle spring acting from above exceed t
