汽车发动机如何工作勘测毕业设计外文文献翻译、中英文翻译、外文翻译

1 How Car Engines Work Introduction to How Car Engines Work Have you ever opened the hood of your car and wondered what was going on in there? A car engine can look like a big confusing jumble of metal, tubes and wires to the uninitiated.  You might want to know what's going on simply out of curiosity. Or perhaps you are buying a new car, and you hear things like "3.0 liter V-6" and "dual overhead cams" and "tuned port fuel injection." What does all of that mean?  If you have ever wondered about this kind of stuff, then read on - In this article, we' ll discuss the basic idea behind an engine and then go into detail about how all the pieces fit together, what can go wrong and how to increase performance. The purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is an internal combustion engine - combustion takes place internally.  Two things to note:  There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on HEMI engines, rotary engines and two-stroke engines. Each has its own advantages and disadvantages.  There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines Almost all cars today use a reciprocating internal combustion engine because this engine is:  Relatively efficient (compared to an external combustion engine)  2 Relatively inexpensive (compared to a gas turbine)  Relatively easy to refuel (compared to an electric car)  These advantages beat any other existing technology for moving a car around.  To understand the basic idea behind how a reciprocating internal combustion engine works, it is helpful to have a good mental image of how "internal combustion" works. One good example is an old Revolutionary War cannon. You have probably seen these in movies, where the soldiers load the cannon with gun powder and a cannon ball and light it. That is internal combustion.  Almost all cars currently use what is called a four-stroke combustion cycle  to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated bellow ,they are:    Intake stroke          Compression stroke    Combustion stroke    Exhaust stroke The piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves, it has the effect of "resetting the cannon." Here's what happens as the engine goes through its cycle：  1.The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.  2.Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. 3.When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down.  4.Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tail pipe.  Then the engine gets ready for the next circle . Cylinders, Displacement and Other Engine Parts 3 The core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi -cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures. Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing-cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles.  Displacement The combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume. The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1,000 cubic centimeters equals a liter).  Valves The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.  Piston A piston is a cylindrical piece of metal that moves up and down inside the cylinder.  Piston rings Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:   They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.   They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.  4 Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.  Connecting rod The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.  Crank shaft The crankshaft turns the piston's up and down motion into circular motion.  Sump The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).  Valve Trains and Systems The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down。 Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams."  Ignition and Cooling Systems The ignition system produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires  send the charge to each spark 5 plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness. Cooling System The cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead.Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.  Air-intake and Starting Systems Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor. Starting System The starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:   All of the internal friction caused by the piston rings   The compression pressure of any cylinder(s) that happens to be in the compression stroke   The energy needed to open and close valves with the camshaft   All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.  Because so much energy is needed and because a car uses a 12 -volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the 6 ignition key, it activates the solenoid to power the motor.  Lubrication and Fuel Systems The lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings that allow things like the crankshaft and camshafts to rotate freely. In most cars, oil is sucked out of the oil pan by the oil pump, run through the oil filter to remove any grit, and then squirted under high pressure onto bearings and the cylinder walls. The oil then trickles down into the sump, where it is collected again and the cycle repeats.  Fuel System The fuel system pumps gas from the gas tank and mixes  it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.  In carburetion, a device called a carburetor mixes gas into air as the air flows into the engine. In a fuel-injected engine, the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).  Exhaust, Emission-control and Electrical Systems The exhaust system includes the exhaust pipe and the muffler. Without a muffler, what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens the sound. The exhaust system also includes a catalytic converter.  Emission Control The emission control system in modern cars consists of a catalytic converter, a collection of sensors and actuators, and a computer to monitor and adjust everything.For example,the catalytic converter uses a catalyst and oxygen to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available for the catalyst to work and adjusts things if necessary. Electrical System The electrical system consists of a battery and an alternator. The alternator is connected to the engine by a belt and generates electricity to recharge the battery. The battery makes 12-volt power available to everything in the car needing electricity (the ignition system, radio, headlights, windshield wipers, power windows and seats, computers, etc.) through the vehicle's wiring.  7 8 译文：  汽车发动机如何工作  关于汽车发动机如何工作的简介  你是否曾经打开过汽车的发动机盖？然后急切的想知道里面究竟是什么东西吗？一部汽车发动机看起来就像杂乱无章的金属管子，线团等组合而成的。  或许出于你的好奇 心，你想知道究竟是什么，或许你现在正打算购买一辆新车，当你听到诸如此类的“ 3.0L V6”、“双凸轮轴顶置”等，你想知道这些代表什么吗？  如果您对这些材料感兴趣 , 那么读读这篇文章吧 , 我们将讨论汽车发动机的基本原理，然后将进一步讨论各部件是怎么衔接工作的，什么部件经常出现故障和怎样匹配才能发挥更大功效。  汽车发动机的目的是将汽油转化为动力然后驱动汽车行走。目前使汽油产生动力最容易的方式就是将置入发动机里面燃烧。所以 , 汽车发动机是一部内燃机。请做好两点笔记：  一、生活中有不同种类的内燃机。有柴油几、汽油机 等。同时还有 HEMI发动机、转子发动机和二冲程发电机。每种类型都有它自己的优点和不足。  二、生活中还有一种外燃机。  蒸汽机在古老的火车和蒸汽船中的运用就是外燃机最佳的例子。燃料 (煤炭 , 木头 , 石油 , 无论什么 )在蒸汽机外部燃烧以产生蒸汽 , 然后蒸汽在蒸汽机里变成动力。内部燃烧比外部燃烧的效率要高得多 (每英里用的燃料比较 ) ，而且内燃机要不外燃机的体积要小得多。这就能更好的解释为什么我们从福特和通用公司看不蒸汽机做为汽车的发动机。  今天，几乎所有的汽车都使用热交换机是因为这个发动机：  效率更高  (与外燃机比 较 )      价格较低廉  (与汽轮机比较 )  加油比较方便  (与电车比较 )  这些优点促使其他现有的技术都为汽车服务。   在了解热交换机如何工作的基本大意之后 , 它对你理解 "内部燃烧 "是怎样工作的有一个好的大概印象。一个好的例子就是一门老革命战争大炮。您大概看见了这些在电影 , 战士用枪粉末和大炮球装载大炮，然后点燃它。那就是内部燃烧。  9 目前，几乎所有的汽车都是经过四行程把汽油转换为动力的。四行程以  奥多周期而著称，主要是用来纪念 Nikolaus 奥多 ,这是因为“四冲程”是奥多于 1867 年发明的。四个冲程列 表如下，他们是： 1.进气行程  2.压缩行程  3.做功行程  4.排气行程   活塞由一连杆连接到曲轴，当曲轴转动时 ,它有 "重新设置大炮的作用 " 。这就是当发动机转动时你即将看到的景象：  1.活塞开始在上止点，进气门打开 ,并且活塞运动到下止点时让发动机充分地吸入空气和汽油。这就是进气行程。为了发动机更好的工作 ,这最微小的一滴汽油必须与汽缸中的空气混合良好。  2.然后活塞上移动压缩油气混合物。这样压缩后的气体燃烧后爆炸更加强劲有力。 (压缩行程 ) 3.当活塞到达压缩行程的上止点时 ,火花塞喷射出火花点燃油气混合物。汽油 在汽缸中燃烧爆炸 ,迫使活塞向下止点运动。 (做功行程 ) 4.一旦活塞运动到做功行程的下止点时 ,排气门打开 ,燃烧后的废气通过排气管道排出。  紧接着发动机准备好下个循环。   汽缸、行程和发动机的其他零件  发动机的核心是汽缸 ,活塞在汽缸里面上上下下的运动。发动机被描述为单缸发动机 ,典型的就是割草机的发动机。但是大多数汽车都是超过一个汽缸的(四 , 六和八缸的很普遍 ) 。在一个多缸发动机中 , 汽缸通常被排列为以下三种形式：直列型 , V 型  或水平对置。  发动机汽缸不同的布局方式因制造费用、形状特征等有不同的优点和局限性， 这些优点和不足之处正好适合不同的车型。  行程  燃烧室是压缩和燃烧发生的区域。当活塞上下运动时 ,您可以看到燃烧室的体积大小的改变。它有最大容积并且也有最小容积。最大容积和最小容积之间的距离叫行程 ,它是用公升或毫升来测量 (1,000 毫升等于一公升 )。    火花塞  火花塞提供火花以便使空气混合气点燃。火花必须在正确的时刻产生以确保发动机可靠地工作。  气门  10 进气门和排气门必须在适当的时间打开或关闭以确保空气和燃料里充分燃烧。请注意两组气门在压缩和燃烧期间都是闭合的以便密封燃烧室确保完全燃烧。   活塞  活塞是 可以在汽缸里面上上下下运动圆柱形金属。   活塞环  活塞环在活塞的外边缘和汽缸的内边缘之间起密封作用。活塞环有两点作用：   1.活塞环防止燃油混合气在压缩行程和废气在排气行程中从燃烧室漏入油底壳。 2.活塞环防止从油底壳带入的润滑油进入燃烧区域 ,这样它会被烧和损失。   大多数汽车因发动机老化和活塞环磨损而 "烧机油 " ，所以每 1,000 英哩必须加一定的润滑油。  连杆  连杆连接活塞和曲轴。它在两个末端都可以旋转以便当活塞上下运动和曲轴旋转运动时可以适时的改变角度。   曲轴  曲轴圆周旋转推动活塞上下运动。   油底壳  油底壳中的润滑油浸没一部分曲轴。它包含一定数量的润滑油 , 收集在油底壳底部。  气门机构和系统  气门机构包括气门和负责打开、关闭他们的机构。负责打开和关闭的系统称  凹轮轴。凹轮轴由上下止点来关闭和打开阀门。现代大部分发动机都有凸轮顶置。这意味着 , 凹轮轴位于在气门之上。凸轮直接地或通过非常短的联结来推动气门。老式发动机的凹轮轴位于曲轴附近，油缸之上。这种方法有更多的运动部件和并且导致更多的运动