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

精品文档 1欢迎下载 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 ship s 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 精品文档 2欢迎下载 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 精品文档 3欢迎下载 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 1 2 Compression 压缩 2 3 Fuel injection 喷油 3 4 Power 动力 4 5 Exhaust 排气 1 Approx 110 BTDC 上止点前约 110 2 Approx 10 BTDC 上止点前约 100 3 Approx 12 ATDG 上止点后约 120 4 Approx 110 ATDG 上止点后约 110 5 Approx 140 ATDC 上止点后约 140 6 Approx 140 BTDC 止点前约 140 7 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 精品文档 4欢迎下载 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 strokes 4 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 5 精品文档 5欢迎下载 1 The diesel engine is a type of 柴油机是一种 答案 D A 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 B A 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 C A 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 C A 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 A A TDC B DTC C BDC D BCD 精品文档 6欢迎下载 8 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 D A after TDC B before TDC C after BDC D before BDC 9 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 C A 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 A A 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 C A as much as 一样多 B less than少于 C twice两倍 D more than 12 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 B A 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 精品文档 7欢迎下载 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 C A 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 D A 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 offset 1 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 精品文档 8欢迎下载 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 ship s 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 例如 其工作原理如下 Task 3 Translation Exercise 任务 3 翻译练习 A Translate the followin