UNIT 5 DIESEL FUEL INJECTION TEXT A Overview of Diesel Fuel Injection,PROFESSIONAL ENGLISH,UNIT 5 DIESEL FUEL INJECTION TEXT A Overview of Diesel Fuel Injection Overall Diesel Fuel System Injector Pump Types Diesel Injector Types Glow Plug and Intake Air Heaters,本次课学习内容,本次课学习目标,掌握柴油机喷油系统的组成 掌握主要部件的型式及原理 掌握有关的专业名词与术语 了解翻译技巧省略,NEW WORDS,schematic skimtik a.示意性的 alert l:t v.向发出警报； clog klg v.&n.阻塞，堵塞 nozzle nz()l n.喷嘴 jam m v.&n.堵塞，拥挤 trap trp n.圈套，陷阱，捕集器 plunger pln n.柱塞，活塞 rack rk n.齿条 barrelbr()l n.桶；v.装入桶内 helix hi:liks n.螺旋，螺旋状物,cutaway ktwei a.切去一部分的，剖面的 instantly instntli ad.立即地，即刻地 variation verieinn.变化，变更，变种，变调 protrude prtru:d v.突出，伸出 dull dl v.变迟钝；a.迟钝的，不鲜明的，无光泽的 readily redili ad.容易，欣然，乐意地,water separator （油）水分离器 inline injector pump 直列式喷油泵 delivery valve 出油阀 segment gear 扇形齿轮 transfer pump 输送泵，输油泵 inline fuel pump 管路串接式燃油泵 inward opening injector 孔式喷油器 outward opening injector 轴针式喷油器 glow plug 预热塞 pumping chamber 预压缩室（腔） wire mesh （金属、钢、塑料）丝网，线网,PHRASES AND EXPRESSIONS,Overview of Diesel Fuel Injection Diesel engines are used on some cars and light trucks. The diesel engine uses the heat of compression, instead of a spark plug, to ignite the fuel. Diesel fuel injection is similar to gasoline injection, but requires higher injection pressures. Air is drawn into the cylinder and highly compressed. The compression is so high that the compressed air will reach temperatures of 1000(538.2). At the precise time the piston has completed the compression stroke, diesel fuel is sprayed into the combustion chamber, or an offset prechamber. The intense heat of the compressed air ignites the fuel, and the power stroke follows. Overall Diesel Fuel System A schematic of a diesel fuel system layout is shown in Fig.5-1. Typical diesel system components include the tank, fuel pump, filter, injection pump, injectors, and the necessary fuel lines. The system in Fig.5-1 is typical of newer systems that utilize a computer-controlled electronic fuel injection pump.,Fig.5-1. An overall view of one particular diesel fuel injection system as used with a V-8 engine.,Water In Fuel Sensor Some vehicles are equipped with a water in fuel sensor that will alert the driver to the fact that water is present in the fuel 1. The water may then be drawn off through a valve in the bottom of a water separator. Water is extremely damaging to the injection system. Fuel Filter Diesel fuel must be kept clean to avoid injector system trouble. Very small particles are enough to clog injector nozzles or jam the injector. Diesel fuel systems typically use one or more filters to trap dirt and other deposits. Diesel Injection Pump Diesel fuel is injected directly into the cylinder at the top of the compression stroke. Due to the high compression (around 22:1) used in diesel engines, the diesel injection pump must be capable of producing high pressures. Injector pump pressures vary greatly depending on the pump and engine. Pressures can range from 3000-15,000 psi (20 685-103 425 kPa).,How the Injector Pump Produces Pressure By using a plunger operating in a cylinder, the pump traps fuel ahead of the plunger. When the plunger is forced up, it builds pressure on the fuel. Pressure will be increased to the point at which the injector will open and spray fuel into the engine. Pumps can use a single plunger for each injector or a single pump (often consisting of two or more opposing plungers) to serve all injectors2. Injector Pump Types There are a number of injector pump designs. The most commonly used automobile and light truck diesel injector pumps are classified as inline or distributor. Both are mechanical pumps that pressurize the fuel and deliver it to the cylinders at the proper time for each. Inline Injector Pump,Inline Injector Pump The inline injector pump uses a separate cylinder plunger-cam for each cylinder. They are contained in a straight row in a common housing. The cams are part of a common camshaft driven by the engine at one-half engine speed. Drive may be by chain, belt, or gear. Fuel from the fuel pump is fed to all of the plunger assemblies. As the camshaft rotates, each of the plungers is moved up and down in their cylinders. A single control rack or rail with gear teeth along one side is meshed with each plunger assembly. By moving the control rack, the effective pump action (amount of fuel pumped) of all plungers can be adjusted. Inline Injector Pump Metering Control Each plunger operates in a separate cylinder or barrel. The top section of the plunger has a wide band or groove cut away. One edge of the cut forms a helix (spiral shape). The plunger also has a vertical slot reaching from the top of the plunger down into the cutaway area.,The bottom of the plunger is connected, by means of a flange, to the toothed control sleeve that meshes with the control rack teeth. When the control rack is moved back and forth, the plunger