毕业设计论文 外文文献翻译 中英文对照 发动机基本原理

1、engine fundamentals automobiles have been operated successfully by electric motors ,steam engines ,and internal combustion engines .the internal combustion engine burns fuel within its cylinders and converts the expanding force of the burning fuel ,or combustion, into a rotary force used to propel t

2、he vehicle.there are several types of internal combustion engines: two-and four-cycle reciprocating piston engines ,gas turbine engines .however ,four-cycle reciprocating engines have been refined to such a degree that they have almost complete dominance of the automotive field .engines of other typ

3、es are described in chapter 18 ,diesel and other engines.many things are demanded of an engine used to propel an automobile. some of the requirements are:（1）ease of starting.（2）reliability.（3）power.（4）responsiveness.（5）economy in fuel ,oil ,and ,repairs.（6）ease of handling.（7）quiet operation.some of

4、 these factors conflict .for example ,a great amount of power can be had from an engine of sufficient size, but a super-size engines is not economical to operate .therefore ,all automobile engines are a compromise in order to obtain the desirable combination of performance and economy.engine fuels i

5、nternal combustion engines can be made to operate on almost anything that can be converted into a combustible gas, such as wood ,coal, alcohol, vegetable oils, mineral oils, etc. however, because of convenience, a variety of petroleum products are commonly used as fuel :gasoline, kerosene ,fuel oil

6、,liquefied petroleum gas (lp-gas) ect. what kerosene ,fuel oil ,or lp-gas is used it is necessary to alter the design of the engine to achieve efficient operation.engine deigngasoline engines used in automotive vehicles are of two basic types :four-cycle engines and two-cycle engines .either type ma

7、y be water-cooled ,or air-cooled .four- ,six-, and eight-cylinder engines are common however, three-, five-, ten- ,and twelve-cylinder engine are available.almost all automobile engines have more than one cylinder. these cylinders can be arranged in an inline ,opposed ,or v-type configuration. engin

8、es for other purpose ,such as aviation, are arranged as radial, inverted inline ,inverted v, and x-shaped configurations.reciprocating enginesin the typical automobile engine, a piston reciprocates (moves back and forth) within each cylinder. each piston is connected to the crankshaft by means of a

9、link known as a connecting rod.other types of reciprocating engines substitutes an eccentric, an inclined plate ,or a cam mechanism for the crankshaft .the piston engine has no crankshaft or connecting rods.engine componentsthe typical automotive engine is made up of several essential components. th

10、ese components are designed to provide efficient and reliable engine operation .the basic components in a four-cycle automotive engine include the following:（1）cylinder block.（2）crankshaft.（3）pitons.（4）piston rings.（5）connecting rods.（6）piston pin.（7）cylinder head.（8）valve train(includes valves and

11、valve operating mechanism). engine constructioncylinder block the cylinder block is cast in one piece. usually, this is the largest and the most complicated single piece of metal in the automobile.the cylinder block is a complicated casting made of gray iron (cast iron ) or aluminum. it contains the

12、 cylinders and the water jackets that surround them. to make the cylinder block, a sand form called a mold is made. then molten metal is poured into the mold. when the metal has cooled the sand mold is broken up and removed. this leaves the tough cylinder-block casting. the casting. the casting is t

13、hen cleaned and machined to make the finished block. cylinder blocks for diesel engines are very similar to those for spark-ignition engines. the basic difference is that the diesel-engine cylinder block is heavier and stronger. this is because of the higher pressures developed in the diesel-engine

14、cylinders.several engines have aluminum cylinder blocks. aluminum is relatively light metal, weighing much less than cast iron. also ,aluminum conducts heat more rapidly than cast soft to use as cylinder wall material. it wears too rapidly. therefore, aluminum cylinder blocks must have cast-iron cyl

15、inder liners or be cast from an aluminum alloy that has silicon particles in it. some manufactures make an aluminum cylinder block that does not have cylinder liners, or sleeves. instead ,the aluminum is loaded with silicon particles. silicon is a very hard material. after the cylinder block is cast

16、, the cylinders are honed. then they are treated with a chemical that etches eats away, the surface aluminum. this leaves only the silicon particles exposed. the pist. the cylinder block is cast in one piece. usually, this is the largest and the most complicated single piece of metal in the automobi

17、le.the cylinder block is a complicated casting made of gray iron (cast iron ) or aluminum. it contains the cylinders and the water jackets that surround them. to make the cylinder block, a sand form called a mold is made. then molten metal is poured into the mold. when the metal has cooled the sand

18、mold is broken up and removed. this leaves the tough cylinder-block casting. the casting. the casting is then cleaned and machined to make the finished block. cylinder blocks for diesel engines are very similar to those for spark-ignition engines. the basic difference is that the diesel-engine cylin

19、der block is heavier and stronger. this is because of the higher pressures developed in the diesel-engine cylinders.several engines have aluminum cylinder blocks. aluminum is relatively light metal, weighing much less than cast iron. also ,aluminum conducts heat more rapidly than cast soft to use as

20、 cylinder wall material. it wears too rapidly. therefore, aluminum cylinder blocks must have cast-iron cylinder liners or be cast from an aluminum alloy that has silicon particles in it. some manufactures make an aluminum cylinder block that does not have cylinder liners, or sleeves. instead ,the al

21、uminum is loaded with silicon particles. silicon is a very hard material. after the cylinder block is cast, the cylinders are honed. then they are treated with a chemical that etches eats away, the surface aluminum. this leaves only the silicon particles exposed. the piston and rings slide on the si

22、licon with minimum wear. piston the piston converts the potential energy of the fuel into the kinetic energy that turns the crankshaft. the piston is a cylindrical shaped hollow part that moves up and down inside the engines cylinder. it has grooves around its perimeter near the top where the ring a

23、re placed. the piston fits snugly in the cylinder. it has grooves around its perimeter near the top where the rings are placed. the piston fits snugly in the cylinder. the pistons ate used to ensure a snug “air tight” fit.the piston in your engines cylinder are similar to your legs when you ride a b

24、icycle. think of your legs as pistons; they go up and down on the pedals, providing power. pedals are like the connecting rods; they are “attached” to your legs. the pedals are attached to the bicycle crank which is like the crank shaft, because it turns the wheels. to reverse this, the pistons (leg

25、s) are attached to the connecting rods ( pedals ) which are attached to the crankshaft (the bicycle rank). the power from the combustion in the cylinders powers the from the combustion rods to turn the crankshaft.connecting rod：the connecting rod shown in is made of forged high strength steel. it tr

26、ansmits force and motion from the piston to the crank pin on the crankshaft. a steel piston pin, or “wrist pin”, connects the small end of the connecting rod. some rods have a lock bolt in the small end. as the piston moves up and down in the cylinder, the pin rocks back and forth in the hole, or bo

27、re, in the piston. the big end of the connecting rod is attached to a crank pin by a rod bearing cap.connecting rod and rod-bearing caps are assembled during manufacture. then the hold for the bearing is bored with the cap in place. this is called line-bring. it make each rod and its cap a matched s

28、et. usually, the same number is stamped on the rod and cap. this prevents the caps setting mixed during engine service. if the caps are mixed, the bearing bore will not be round. an engine assembled with the rod bearing caps switched will probably lock the crankshaft. if the crankshaft turns, the be

29、aring will probably have improper clearance and early bearing failure will result.another reason for keeping the cap and rod matched is to prevent engine unbalance and unwanted vibration. all connecting rods in an engine must be as light as possible. but they must all weigh the same. if one rod is h

30、eavier than the other, the engine will vibrate. this could damage the engine.crankshaftthe crankshaft then main rotating member, or shaft , in the engine. it has crank-pins, to which the connecting rod from the pistons are attached . during the power strokes, the connecting rods force the crank-pins

31、 and therefore the crankshaft to rotate. the reciprocating motion of the pistons is changed to rotary motion as the crankshaft spins. this rotary motion is transmitted through the power train to the car wheels.the crankshaft is a strong, one-piece casting, or forging, or heat-treated alloy steel. it

32、 must be strong to take the downward force of power strokes without excessive bending. it must be balanced so the engine will run without excessive vibration. engine operating principlesmost automobile engines are internal combustion, reciprocating 4-stroke gasoline engines, but other types have bee

33、n used, including the diesel the rotary (wankel), the 2-stroke and the stratified charge.reciprocating means “up and down” or “back and forth”. it is the up and down action of a piston in the cylinder that produces power in a reciprocating engine. almost all engines of this type are built upon a cyl

34、inders block, or engine block. the block is an iron or aluminum casting that contains engine cylinders and passages called water jackets for coolant circulation. the top of the block is covered with the cylinder head, which forms the combustion chamber. the bottom of the block is covered with an oil

35、 pan or oil sump.power is produced by the linear motion of a piston in a cylinder. however, this linear motion must be changed into rotary motion to turn the wheels of cars and trucks. the piston is attached to the top of a connecting rod by a pin, called a piston pin or wrist pin. the bottom of the

36、 connecting rod is attached to the crankshaft. the connecting rod transmits the up-and-down motion of the piston to the crankshaft, which changes it into rotary motion. the connecting rod is mounted on the crankshaft with large bearings called rod bearings. similar bearings, called main bearings, ar

37、e used to mount the crankshaft in the block.the diameter of the cylinder is called the engine bore. displacement and compression ratio are two frequently used engine specifications. displacement indicates engine size, and compression ratio compares the total cylinder volume to compression chamber vo

38、lume.the term “stroke” is used to describe the movement of the piston within the cylinder, as well as the distance of piston travel. depending on the type of engine the operating cycle may require either two or four strokes to complete. the 4 stroke engine is also called otto, who first applied the

39、principle in 1876. in the 4 stroke engine, four strokes of the piston in the cylinder are required to complete one full operating cycle. each stroke is named after the action it performs intake, compression, power, and exhaust in that order.（1）intake strokeas the piston moves down, the vaporized mix

40、ture of fuel and air enters the cylinder through the open intake valve. to obtain the maximum filling of the cylinder the intake valve opens about 10before t. d. c., giving 20overlap. the inlet valve remains open until some 50after b. d . c. to take advantage of incoming mixture.（2）compression strok

41、ethe piston turns up, the intake valve closes, the mixture is compressed within the combustion chamber, while the pressure rise to about 1mpa depending on various factors including the compression ratio, throttle opening and engine speed. near the top of the stroke the mixture is ignited by a spark

42、which bridges the gap of the spark plug.（3）power stroke the expanding gases of combustion produces a rise in pressure of the gas to some 3.5 mpa, and the piston is forced down in the cylinder. the exhaust valve opens near the bottom of the stroke.（4）exhaust stroke the piston moves back up with the e

43、xhaust valve open some 50before b. d. c. , allowing the pressure within the cylinder to fall and to reduce back piston during the exhaust stroke, and burned gases are pushed out to prepare for the next intake stroke. the intake valve usually opens just before the exhaust stroke.this 4 stroke cycle i

44、s continuously repeated in every cylinder as long as the engine remains running.a 2 stroke engine also goes through four actions to complete one operating cycle. however, the intake and the compression actions are combined in one stroke, and the power and exhaust actions are combined in the other st

45、roke. the term 2 stroke cycle or 2 stroke is preferred to the term 2 cycle, which is really not accurate.in automobile engines, all pistons are attached to a single crankshaft. the more cylinders an engine has he more power stroke produced for each revolution. this means that an 8-cylinder engine ru

46、ns more smoothly because the power strokes are closer together in time and in degrees of engine rotation.the cylinders of multi cylinder automotive engines are arranged in one of three ways. (1) inline engines use a single block of cylinder. most 4 cylinder and any 6 cylinder engines are of this des

47、ign. the cylinders do not have to be vertical. they can be inclined to either side.(2) v-type engines use two equal banks of cylinders, usually inclined 60 degrees or 90 degrees from the each other. most v-type engines have 6 or 8 cylinders, although v 4 and v 12 engines have been built.(3) horizont

48、ally opposed or pancake engines have two equal banks of cylinders 180degrees apart. these space saving engine designs are often air cooled, and are found in the chevrolet carver, porsches, subaru s, and volkswagens. subarus design is liquid cooled. late-model volkswagen vans use a liquid cooled vers

49、ion of the air cooled vw horizontally opposed engine. 发动机基本原理汽车已经工作的非常成功通过电子马达，蒸汽机，和内燃机，内燃机在气缸里燃烧并且将燃料燃烧发出的膨胀力转换或旋转力用来推动汽车。内燃机有好几种类型：两冲程或四冲程的活塞发动机，涡轮发动机，自由活塞的发动机。然而，四冲程的发动机改进的程度如此之高。已经几乎统治垄断了汽车的领域，其它类型的发动机，如柴油机在以后再叙述。发动机上的许多东西都是有要求，它们常用于推动发动机，许多的要求如下：（1）容易起动性能：(2)可靠性。(3)动力性。(4)灵敏性。(5)燃料，机油，维修的经济性。(6

50、)轻便的操纵性。(7)安全的工作性能。有些性能是互相冲突的，例如，很大的动力需要以尺寸是足够大的发动机上获得，但是这么大的尺寸的发动机工作时经济性不好，因此，所有汽车的发动机都是为获的满意的性能和经济性。发动机的燃料内燃机能被制造或依靠几乎任务东西运行的，只要这些东西能转换或燃料的气体。例如木材，煤矿，酒精，植物油，矿物油等，燃而，因为适合方便，各种各样的石油产品被用来作为燃料，汽油，煤油，液化气等当煤油，燃油或液化气被使用时，必须改变发动机的设计从而获得较高的效率。发动机的设计用于车辆上的汽油发动机有两种基本类型，四冲程发动机任何其中一种类型都应是水冷或风冷，四缸六缸和八缸的发动机都是普通常

51、见的燃而三缸五缸十缸的发动机都是可以利用的几乎所有汽车的发动机的汽缸都不少于一个。这些汽缸都被设计或线性排列对置或v型的结构，其它途径的发动机例如航空应用的都被设计成辐射状的倒置反转的v型的结构。往复式发动机在这种类型汽车的发动机里，活塞在各自的汽缸里往复运动。每个活塞通过连杆被连接在曲轴上。其它类型往复式发动机的的代表是离心的，有斜向的盘子，或在曲轴上有一个凸轮机构。自由活塞的发动机没有曲轴或连杆。发动机的部件典型的汽车的发动机是由许多必须的部件组成的，这些部件被设计成用来提供发动机运行的可靠性和高效率性。四缸汽车发动机的基本部件包括：（1）汽缸体。（2）曲轴。（3）活塞。（4）活塞环。（5

52、）连杆。（6）活塞销。（7）汽缸盖。（8）气阀结构。 发动机结构汽缸体汽缸体是铸造成而成一体的。通常，这是发动机上最大，最复杂的铁制的部件。汽缸体是用灰铸铁或铝铸造成的。它包括汽缸体本身和环绕在周围的水套。要做汽缸体需要一个沙模模型，然后将金属溶液倒入模型中。当金属溶液冷却后，将模型打破拿走，只剩下了一个粗糙的汽缸体。然后将它清洁机加工，最后完成一个汽缸体。柴油机用的发动机与汽油机用的非常相似。最根本的不同是柴油机的比汽油机的更加坚固更沉。这是因为柴油机产生的气缸压力更大。有许多发动机用的是铝制的气缸。铝也是一种金属，重量比铸铁要轻很多，并且铝的导热速度比铸铁的要快。这就是说它发生爆燃的可能性

53、要小。然而，铝作为汽缸体材料来说较软，铝的磨损也非常快。因此，铝制气缸要有气缸衬套，因此在铝中加入硅粒子形成铝合金。一些制造商制造的铝制气缸也没有气缸。他在铝中加入了硅粒子。硅是非常硬的材料。气缸在铸造后，要进行研磨。然后给它们涂上一层化学制剂，把表面上的铝腐蚀掉。这样只剩下硅存在表面。此时，活塞和环磨损最小。活塞活塞将化学能转变为动能传给曲轴。活塞是一个圆柱状放在气缸内的物体。活塞顶部有放置活塞环的活塞环槽。活塞可以更合适的放在气缸中。活塞环用来保持气缸的气密性。活塞在气缸中就像你在骑自行车时的腿。认为你的腿和活塞一样；当上下踏脚踏板时可以产生动力。脚踏板就像连杆；它连着你的腿。踏板连着自行车的轴，这个轴类