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1、,Lesson one How does a Marine Diesel engine Work?,Prof. Song Zhou,2007-11-1,New Words and Expressions in Text,marine 海运的，船用的 diesel 柴油，柴油机 internal 内部的 combustion 燃烧 ignite 点燃 inject 喷射 chamber 腔，室 principle 原理，原则 operation 工作，操作，运转，进程 charge 装，充；充填物 fresh 新鲜的，淡(水)的 draw 抽吸 cylinder 气缸 compression 压
2、缩 piston 活塞 fine 细小的，好的 spray 喷雾，(水，油)雾 burn 燃烧,2007-11-1,rotate 旋转，回转 medium 中间的，介质 alternator 交流发电机 in turn 依次，轮流变成 turn into 变成 event 事件，过程 stroke 冲程，行程 separate (from) 分离，分开 exhaust 排出，耗尽；排气 combine (with) 结合，联合 inlet 进口，入口 scavenge 扫除；吹除 blow 吹，鼓风 residual 剩余的，残留的 value 价值，数值 injector 喷射器，喷油器 c
3、ontinue 继续(进行) revolution 转 theoretically 理论上地 inefficient 效率低的，无效的,2007-11-1,advantage 优势，优点，长处 application 应用 propulsion 推进(装置) cause 引起；原因 force 迫使 crankshaft 曲铀 propeller 螺旋桨，推进器 cycle 循环 consist (of) 由组成 fix 固定 sequence 顺序，系列 bottom dead centre (BDC) 下止点 top dead centre (TDC) 上止点 on board ship
4、在船上 r/min 转分 reduction gear box 减速齿轮箱,2007-11-1,*The diesel engine is a type of internal combustion engine which ignites(点燃) the fuel by injecting(喷射) it into hot, high pressure air in a combustion chamber(燃烧室).,2007-11-1,The marine diesel engine is a type of diesel engine used on ships. The princip
5、le of its operation is as follows:,2007-11-1,A charge of fresh air is drawn or pumped into the engine cylinder(气缸) and then compressed by the moving piston(活塞) to very high pressure.,2007-11-1,When the air is compressed, its temperature rises so that it ignites the fine spray(喷雾、油雾) of fuel injected
6、 into the cylinder.,2007-11-1,The burning of the fuel adds more heat to the air charge, causing it to expand and force the engine piston to do work on the crankshaft which in turn drives the ships propeller(螺旋桨).,2007-11-1,Exhaust valve,Inlet valve,Fuel injector,Cylinder,Piston,Piston ring,Connectin
7、g rod,Four-stroke diesel engine,Combustion chamber,Piston pin,crankshaft,Crank web,2007-11-1,Fuel injector,Fuel injector,Exhaust valve,扫气口 Scavenge port,Exhaust port,Two-stroke Engine,Cross scavenge system,Uniflow scavenge system,Piston rod,Connecting rod,Piston pin,Crosshead,2007-11-1,The operation
8、 between two fuel injections is called a working cycle, which consists of a fixed sequence of events.,2007-11-1,This cycle may be achieved either in four strokes(冲程、行程) or two.,2007-11-1,In a four-stroke diesel engine, the cycle requires four separate strokes of the piston, i.e. suction(吸气), compres
9、sion(压缩), expansion(膨胀) and exhaust(排气). * Note: i.e. (拉=id est)即；就是,2007-11-1,If we combine the suction and exhaust operations with the compression and expansion strokes, the four-stroke engine will be turned into a two-stroke one, as is shown in Figures 1-a)d).,2007-11-1,Scavenge (a),Compression (
10、b),Injection (c),Exhaust (d),Scavenge port,Exhaust port,Fuel injector,Cylinder,Piston,Connecting rod,Crank,2007-11-1,The two-stroke cycle begins with the piston coming up from the bottom of its stroke, i.e. bottom dead center (BDC), with the air inlet ports or scavenge ports(扫气口) in the sides of the
11、 cylinder being opened (Fig. 1-a).,2007-11-1,The exhaust ports are uncovered also. Pressurized fresh air charges into the cylinder, blowing out any residual exhaust gases from the last stroke through the exhaust ports.,2007-11-1,As the piston moves about one fifth of the way up, it closes the inlet
12、ports and the exhaust ports. The air is then compressed as the piston moves up. (Fig. 1-b).,2007-11-1,When the piston reaches the top of its stroke, i.e. the top dead center (TDC), both the pressure and the temperature of the air rise to very high values.,2007-11-1,The fuel injector injects a fine s
13、pray of fuel into the hot air and combustion take place, producing much higher pressure in the gases.,2007-11-1,The piston is forced(迫使) downward as the high pressure gases expand until it uncovers the exhaust ports.,2007-11-1,The burning gases begin to exhaust (Fig. 1-d) and the piston continues do
14、wn until it opens the inlet ports. Then another cycle begins.,2007-11-1,In the two-stroke engine, each revolution of the crankshaft (曲轴) makes one power or working stroke, while in the four-stroke engine, it takes two revolutions to make one power stroke.,2007-11-1,That is why a two-stroke cycle engine will theoretically develop twice (two times) the power of a four-stroke engine of the same size.,2007-11-1,Inefficient scavenging and other losses, however, reduce the power advantage to about 1.8.,2007-11-1,Each type of engine has its applica
