Lesson-2-How-Does-a-Marine-Diesel-Engine-Work.doc

Lesson 2 How Does a Marine Diesel Engine Work第2 课 船用柴油机是如何工作的1. The diesel engine is a type of internal combustion engine which ignites the fuel by injecting it into hot, high pressure air in a combustion chamber. The marine diesel engine is a type of diesel engine used on ships. The principle of its operation is as follows:1. 柴油机是一种内燃机, 通过把燃油喷入高温高压的燃烧室而发火。船用柴油机是一种在船上使用的柴油机。其工作原理如下：2. A charge of fresh air is drawn or pumped into the engine cylinder and then compressed by the moving piston to very high pressure.一定量的新鲜空气被吸入或泵入气缸并被运动的活塞压缩至很高的压力。3. When the air is compressed, its temperature rises so that it ignites the fine spray of fuel injected into the cylinder. The burning of the fuel adds more heat to the air charge, causing it to expend and force the engine piston to do work on the crankshaft which in turn drives the ships propeller.空气被压缩时, 温度升高, 便点燃喷入气缸的油雾。燃油的燃烧对缸内空气的加热, 使空气膨胀并迫使发动机活塞对曲轴做功, 随之驱动螺旋桨。4. The operation between two injections is called a cycle, which consists of a fixed sequence of events. This cycle may be achieved either in four strokes or two. In a four-stroke diesel engine, the cycle requires four separate strokes of the piston, i.e. suction, compression, expansion and exhaust. As its name implies a two-stroke cycle takes place in two consecutive strokes of the engine piston, or one revolution of the crankshaft. Thus each operation in the cycle is repeated during every revolution of the engine. The two strokes of the cycle may be termed: Compression stroke and power or expansion stroke.4. 两次喷油期间的运转过程叫一个工作循环。它由一些程序固定的过程组成。这个循环可在二行程或四行程内完成。四冲程柴油机的工作循环需要四个独立的活塞行程, 即吸气、压缩、膨胀和排气。正如其名称所指，二冲程工作循环内发动机活塞完成两个连续冲程，或曲轴转一周。因此，每个循环的运行随着发动机每转一周而重复。这种循环的两个冲程可称为压缩冲程和动力或膨胀冲程。5. Its operation is as follows (see Fig. 2-1):5. 其工作原理如下(见图2-1):1) The crankshaft is revolving clockwise and the piston is moving up the cylinder, compressing the charge of air. Because energy is being transferred into the air, its pressure and temperature increase. By the time the piston is approaching the top of the cylinder (known as top dead center or TDC) the pressure is over 100 bar and the temperature over 500.1) 曲轴顺时针旋转，活塞沿气缸向上运动，压缩充入的空气。由于能量被转移到空气中，其压力和温度都增高。当活塞接近气缸顶部(称为上止点或TDG)时，压力达到100 bar以上，温度超过500。2) Just before TDC fuel is injected into the cylinder by the fuel injector. The fuel is “atomized” into tiny droplets. Because they are very small these droplets heat up very quickly and start to burn as the piston passes over TDC. The expanding gas from the fuel burning in the oxygen forces the piston down the cylinder, turning the crankshaft. It is during this stroke that work energy is being put into the engine.2) 在活塞就要到达上止点之前，喷油器把燃油喷入气缸。燃油被“雾化”成细小的液滴。这些液滴非常小，因而升温很快，在活塞经过上止点时开始燃烧。燃油在氧气中的燃烧使气体不断膨胀，迫使活塞沿气缸向下运动，转动曲轴。正是在这一冲程期间发动机获得工作能量。3) As the piston moves down the cylinder, the useful energy from the burning fuel is expended. At about 110o after TDC the exhaust valve opens and the hot exhaust gas (consisting mostly of nitrogen, carbon dioxide, water vapour and unused oxygen) begins to leave the cylinder.3) 随着活塞沿气缸向下运动，燃油燃烧产生的有用能量被消耗掉。上止点后约110，排气阀打开，高温废气(主要包括氮气、二氧化碳、水蒸气和未使用的氧气)开始离开气缸。4) At about 1400after TDC the piston uncovers a set of ports known as scavenge ports. Pressurized air enters the cylinder via these ports and pushes the remaining exhaust gas from the cylinder in a process known as “scavenging”. The piston now goes past bottom dead center and starts moving up the cylinder, closing off the scavenge ports. The exhaust valve then closes and compression begins.4) 上止点后约140，活塞打开被称为扫气口的一组气孔。增压空气通过这些气孔进入气缸，推动剩余的废气排出气缸，这一过程被称为“扫气”。活塞现在经过了下止点并开始沿气缸向上运动，关闭了扫气口。随后，排气阀关闭，压缩开始。6. The two-stroke cycle can also be illustrated on a timing diagram (see Fig. 2-2).二冲程循环也可以图解为一个正时图(见图2-2 ) Fig.2-2 two-stroke cycle and timing diagrams图2-2 二冲程循环正时图12 Compression压缩23 Fuel injection喷油34 Power动力45 Exhaust排气1. Approx 110 BTDC上止点前约110 2. Approx 10BTDC上止点前约1003. Approx 12 ATDG上止点后约120 4. Approx 110 ATDG上止点后约1105. Approx 140 ATDC上止点后约140 6. Approx 140 BTDC止点前约1407. The main difference between the two-stroke and the four-stroke cycles is the power developed. The two-stroke cycle engine, with one working or power stroke every revolution will, theoretically, develop twice the power of a four-stroke engine of the same swept volume. Inefficient scavenging however and other losses, reduce the power advantage to about 1.8. For a particular engine power the two-stroke engine will be considerably lighter-an important consideration for ships. Nor does the two-stroke engine require the complicated valve operating mechanism of the four-stroke. The four-stroke engine however can operate efficiently at high speeds, which offsets its power disadvantage; it also consumes less lubricating oil.7. 二冲程和四冲程循环的主要区别是产生的功率不同。每转有一个工作或做功冲程的二冲程发动机理论上产生的功率是同样容积排量的四冲程发动机的两倍。然而，扫气不充分和其他损失使这一优势降到大约1.8倍。对于特定的发动机功率，二冲程发动机的重量轻得多，这是船舶一个重要的考虑因素。二冲程发动机也不需要四冲程发动机那样复杂的气阀操纵机构。然而，四冲程发动机能够在高速下高效运转，抵消了其功率的不足;而且其润滑油的消耗量较少。8. Each type of engine has its applications, which on board ships have resulted in the slow speed (i. e. 80-100 r/min) main propulsion diesel operating on the two-stroke cycle. At this low speed the engine requires no reduction gearbox between it and the propeller. The four-stroke engine (usually rotating at medium speed, between 250 and 750 r/min) is used for auxiliaries such as alternators and sometimes for main propulsion with a gearbox to provide a propeller speed of between 80 and 100 r/min.每种柴油机都有其应用。在船上，低速(即80-100 r/min)主推进柴油机以二冲程工作。在此低速下，机桨间不需减速箱。四冲程柴油机(通常以中速运转，转速为250-750 r/min)用于辅助机械，如交流发电机，有时作主推进装置，用减速箱提供80-100 r/min的螺旋桨速度。Task 1 Reading Comprehension任务1阅读理解A. Topics for Discussion A.讨论话题1. What does the term “cycle” mean?1.“循环”这一术语是什么意思?The operation between two injections is called a cycle.2. Please name the four strokes of a four-stroke diesel engine according to their sequence.2.请按顺序说出四冲程柴油机的四个冲程。The four strokes are: suction, compression, expansion and exhaust.3. How many revolutions of the crankshaft does it take for a two-stroke engine to complete one power stroke? What about a four-stroke one?3.二冲程柴油机完成一个动力冲程曲轴需转几转?四冲程柴油机呢?For a two-stroke engine, it takes one revolution of the crankshaft to complete one power stroke.For a four-stroke engine, it takes two revolutions of the crankshaft to complete one power stroke.4. Among the four strokes of a four-stroke diesel engine, which strokes are the downward strokes and which strokes are the upward strokes4. 四冲程柴油机四个冲程中，哪些冲程是下行冲程，哪些是上行冲程?Among the four strokes of a four-stroke diesel engine, suction and expansion strokes are the downward strokes and compression and exhaust strokes are the upward strokes?5. Say something about the comparison of two-stroke and four-stroke cycles.5.说说二冲程与四冲程循环的对比。The main difference between the two-stroke and the four-stroke cycles is the power developed. develop twice the two-stroke cycle engine, with one working or power stroke every revolution will, theoretical of a four-stroke engine of the same swept volume.B. Multiple Choice B.选择题Questions 1-5 are based on paragraphs 1-4. 根据课文第1-4段回答问题1-51. The diesel engine is a type of . 柴油机是一种。答案:DA. turbine engine涡轮机B. gas turbine.燃气轮机C. steam engine.蒸汽机D. internal combustion engine内燃机2. The operation between two fuel injections is called . 两次喷油之间的操作叫_。答案:BA. a power stroke一个做功冲程B. a working cycle一个工作循环C. circulation 循环D. a sequence一个顺序3. In a four-stroke engine, the cycle of events is completed in four strokes of 四冲程柴油机中，循环是在_的四个冲程内完成的。答案:CA. the cylinder气缸B. the crankshaft曲轴C. the piston活塞 D. the crosshead十字头4. In the four-stroke engine, it takes to make one power stroke四冲程柴油机曲轴转_做一个做功冲程。答案.CA. one propulsion一次推进 B. two propulsions.两次推进C. two revolutions 两转D. one revolution一转5. A charge of fresh air is drawn or pumped into the engine cylinder and then by the moving piston to very high pressure. 一定量的新鲜空气被吸入或泵入柴油机气缸，并被运动的活塞至很高的压力。A. suctioned 吸入 B. compressed压缩C. exhausted 排出 D. expanded.膨胀6. Compression takes place in the cylinder through the motion of the piston压缩冲程通过活塞沿气缸的_运动来进行。答案.B.A. downward下行B. upward上行C. inward向里D. outward向外7. During working, when the piston is near the , the air ignites the fine spray of fuel工作时，当活塞靠近时，气缸内的空气点燃细雾状的燃油。答案.AA. TDCB. DTCC. BDCD. BCD8. For an ordinary four-stroke engine the exhaust valves open .对于一般的四冲程柴油机，排气阀在_打开。答案:DA. after TDCB. before TDCC. after BDCD. before BDC9. In which stroke is the working energy being put into the engine? 柴油机从哪一冲程中得到工作能量?答案:CA. Suction. 吸气B. Compression压缩。C. Expansion.膨胀D. Exhaust. 排气10 When the piston of an engine is at the lowest point of its stroke, the engine is said to be on . 当活塞在冲程的最低点时，就说成是柴油机处于_。答案:AA. bottom dead center下止点B. inner dead center总固容量C. outer dead center 外止点D. TDC上止点Questions 11-14 are based on paragraphs 6-8.11. The two-stroke cycle engine, with one working or power stroke every revolution will, theoretically, develop the power of a four-stroke engine of the same swept volume. 每转有一个工作或做功冲程的二冲程发动机理论上产生的功率是同样容积排量的四冲程发动机的。答案-CA. as much as 一样多B. less than少于C. twice两倍D. more than12. For a particular engine power the two-stroke engine will be considerably lighter. the complicated valve operating mechanism of the four-stroke. 对于特定的发动机功率，二冲程发动机的重量轻得多，_四冲程发动机那样复杂的气阀操纵机构。答案.BA. Nor the two-stroke engine requires二冲程发动机也不需要(语法错误)B. Nor does the two- stroke engine require二冲程发动机也不需要(本题因否定词nor放在句首，应采用倒装句式)C. Nor the two- stroke engine require二冲程发动机也不需要(语法错误)D. Nor do the two-s stroke engine require二冲程发动机也不需要(语法错误)13. Each type of engine has its applications, which on board ships have resulted in the slow speed main propulsion diesel operating cycle. .每种柴油机都有其应用。在船上，低速主推进柴油机_工作。答案:CA. on the four-stroke以四冲程B. in the two-stroke以二冲程（介词应用on)C. on the two-stroke以二冲程D. either on the two-stroke or on the four-stroke以二冲程或四冲程14. The four-stroke engine is used for auxiliaries such as alternators and sometimes for main propulsion with to provide a propeller speed of between 80 and 100r/min. 四冲程柴油机用于辅助机械，如交流发电机，有时作主推进装置，用提供80 - 100 r/min的螺旋桨速度。答案:DA. a control box控制箱B. a governor调速器C. a monitor 监控器D. a gearbox减速箱Task 2 Vocabulary and Structure任务2词汇与结构A. Technical Terms A.专业术语Translate the following into Chinese. 将下列词组译成汉语。1. valve operating mechanism 阀操纵机构2. internal combustion engine内燃机3. combustion chamber燃烧室4. top dead center上止点5. fuel injector喷油器6. exhaust valve排气阀7. working or power stroke工作或做功冲程8. swept volume容积排量B. Active Words B.常用词Complete the following sentences by filling in the blanks with the words in the table. Change the form of the words if necessary. 从框中选词完成句子，如有必要改变词的形式。Ignite compress inject atomize offset1. The diesel engine is a type of internal combustion engine which it into hot, high pressure air in a combustion chamber.1. ignites, injecting柴油机是一种内燃机，通过把燃油喷入高温高压的燃烧室而将其点燃。2. The four-stroke however can operate efficiently at high speed, which its power disadvantage. 2. offsets然而，四冲程发动机能够在高速下高效运转，抵消了其功率的不足。3. Just before TDC fuel is injected into the cylinder by the fuel injector. The fuel is into tiny droplets.3. atomized 在活塞就要到达上止点之前，喷油器把燃油喷入气缸。燃油被雾化成细小的液滴。4. When the air is its temperature rises so that it ignites the fine spray of fuel injected in to the cylinder.4. compressed空气被压缩时，温度升高，便点燃喷入气缸的细雾状的燃油。Understand the phrases by studying the sentences below and translate the phrases into Chinese. 通过学习下面的句子理解短语，并将短语译成汉语。1. by the time: 1.到时候为止，等到e. g. By the time the piston is approaching the top of the cylinder, the pressure is over 100 bar and the temperature over 500.例如:到活塞接近气缸顶部时为止，压力超过100 bar,温度超过500。2. in turn: 依次，轮流e. g. 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.例如:燃油的燃烧给缸内空气加入了更多的热量，使空气膨胀并迫使发动机活塞对曲轴做功，随之驱动螺旋桨。3. as follows: 列举如下e. g. The principle of its operation is as follows.例