发动机专业英语翻译

发动机专业英语翻译 Petrol and Diesel Engines 汽油发动机机和柴油发动机 The explosive mixture of the petrol engine is provided by a carburettor, but in the case of the diesel engine the supply is effected by an injection or jerk pump which forces a shot of fuel into each cylinder in turn according to the correct firing sequence. 翻译:汽油发动机由一个化油器输送可燃混合气体，而柴油发动机，由一个喷射泵或柱塞式 燃油泵实现燃油供应，此泵根据正确的点火顺序把少量燃油依次压入每个汽缸。 The pump is actuated from a camshaft and the amount injected for each power stroke is extremely small at maximum output, indeed it may be less than 0.1 cm2 , Moreover, this charge must be metered with great and constant accuracy even while it is being variably controlled to regulate power from idling to maximum.It will be realised that efficient and economical running is largely dependent upon the fuel pump. 翻译:通过凸轮轴驱动油泵。每个功率冲程的燃油喷射量在最大输出功率时是非常微小的， 实际上，可能小于0.1 cm2。而且，此燃油量虽然从怠速到最大速度要进行不同的控制调节， 但此燃油量必须非常精确和稳定地进行测量。人们认识到有效和经济的运行主要依靠燃油泵 Multi-cylinder engines are normally equipped with pumps in unit monobloc form incorporating a corresponding number of elements，having a common camshaft and control means but provided with individual adjustments for regulating their output and setting their timing .An equal quantity of fuel must be delivered by each element, which is calibrated separately to a predetermined rate of delivery.Timing of the start of injection in relation to engine crankshaft position must also be constant and equal on each element, the setting process is called phasing. Calibration and phasing are precision operations to be carried out only by skilled service mechanics who have the necessary specialised equipment. 翻译:多汽缸发动机一般情况下装配整体式油泵，把相关的喷射单元组合成一体，共用凸轮 轴和控制方式，但可单独调整以调节各自功率输出和设定各自的正时。每个喷射单元必须输 送等量燃油,按照预定的输送比率分别校准。与发动机曲轴位置度相关的喷射开始时间在每 个喷射单元也必须是恒定相等的。设定的过程被称为调整相位。校准和调整相位是精确的操 作，只有熟练的服务机械师用必要的专用工具才能进行。 A very important detail is that injection must cease cleanly and abruptly at the end of the delivery period without any trace of after-dribble from the injector; otherwise carbon deposits quickly form on the nozzle tip and excessive smoke will appear in the exhaust.The required condition is ensured by the special design of the pump delivery valves which provide for a very rapid collapse of pressure in the injector fuel pipes at the end of injection 翻译:一个非常重要的细节是燃油喷射必须在燃油输送结束时干净且突然地停止，从喷射泵 上不留下任何后渗漏的痕迹。否则，在喷嘴尖上很快形成积碳，排气管将冒浓烟。这种要求 由专用(专门的)输油泵输送气阀来保证，此气阀可以在喷射结束时快速终止喷射泵燃 油管的压力。 At an early stage in the evolution of the high-speed diesel a variable timing device was introduced in the pump drive coupling, taking the form of a helically splined coupling by means of which the angular relation between driving and driven shafts could be varied by manual or automatic control.This device has always been a feature of Gardner engines where it is coupled to the accelerator control.In some makes of engine the helically splined coupling is not used and the angular displacement of the shafts is effected by centrifugally actuated devices of the swinging link or inclined plane type.The fitting of variable timing devices has been discarded by some manufacturers in favour of fixed timing, but in recent years the extensive adoption of the distributor type of fuel pump, which incorporates a simple variable timing device, has now brought this refinement into much more general use. 翻译:在高速柴油机发展的早期，可变的正时装置被引用到油泵驱动联轴节上，采用螺 旋式花键套管的形状，驱动轴和从动轴之间的相对角度可以通过手动或自动控制进行改变。 此装置是加德纳发动机的一个特征，总是和加速器控制连接在一起。在一些发动机的制造中， 并不使用螺旋式花键套管，通过摇杆或斜面型的偏心操纵装置，曲轴相位角起到同样作用。 一些制造商放弃装配可变正时装置，而采用固定正时。但是，最近，装配一个简单可变正时 器的分配器型的燃油泵广泛采用，使这精致的附件获得更普遍的使用。 From the above it will be realised that fundamental difference between petrol and diesel engines is that in the petrol engine the source of heat for igniting the charge, namely an electric spark, is generated outside the engine, and is taken, as it were, into the waiting charge at the required instant.In the diesel engine the source of heat for igniting the charge is created within the engine by compressing pure air to a degree that will initiate combustion and then injecting the fuel at the right time in relation to the movement of the crankshaft.It will have been gathered that apart from their auxiliary features, both classes of engine are of very similar construction.But as the diesel is called upon to withstand very much greater stresses due to higher pressures in the cylinders, it has to be of more substantial construction and is thus heavier. 翻译:通过以上描述，人们认识到汽油机和柴油机之间的基本差别是汽油机里，点燃混合气 体的(也就是一个电火花塞)热源产生于发动机外面，在要求的瞬间，热源被吸进等待的混 合气体里。在柴油机里，点燃燃料热源产生于发动机内部，把纯净的空气压缩到开始燃烧的 程度，然后，在曲轴运动相连的准确时刻喷射燃油。从收集的资料看，除了辅助的特点外， 两种的发动机结构非常相似。但是。由于压力更高，柴油机的汽缸里要求经受大得多的应力， 所以，柴油机必须(拥有)更坚固的结构，因而，会增加起其重量。(其重量更重) By careful design and by taking full advantage of the most advanced metallurgical technique the power/weight ratio of the automotive diesel was substantially improved within the course of a very few years so that the weights of present-day engines do not appear to be capable of much further reduction 翻译:通过认真设计和完全利用最先进的冶金技术的优点，汽车柴油机的功率/重量比在最 近几年里有本质的改进，以致，现在发动机的重量似乎已经降到最低程度(似乎不能再减少)。 The Four-stroke Cycle 四冲程循环 Anyone familiar with the working of the ordinary petrol engine is aware that the motive power is produced by igniting above the piston in each cylinder a mixture of petrol vapour and air, the resultant combustion of which causes an expansion of gases exerting pressure on the top of the piston.By this means the heat released by the fuel is transformed into work, the reciprocating movement of the pistons being converted into rotary movement of a crankshaft by means of the connecting rods. 翻译:熟悉普通汽油发动机原理的人知道，通过点燃每个汽缸里活塞上面汽油蒸气和空气混 合气体，混合气体燃烧的结果使气体膨胀，给活塞顶部施加压力而产生动力。通过这种方式， 燃料释放的热量被转换成功。活塞的往复运动通过连杆被转换成曲轴的旋转运动。 The four-stroke cycle is the operating sequence more commonly employed.It requires that each cylinder be provided with an inlet valve to admit a combustible mixture of petrol and air drawn by the suction of the engine from a mixing device known as the carburettor into the space above the piston, while there must also be an exhaust valve to control the outlet through which the residual products of combustion are ejected after they have done their work. 翻译:四冲程循环是被普遍采用的工作顺序。四冲程循环要求装配一个进气阀，允许把发动 机从混合装置也就是化油器上吸入的可燃的汽油和空气混合气体进入活塞上面的空间，同 时，也必须有一个排气阀，控制排出气体，把燃烧的残余物质在做完功后喷射出去。 To describe the complete cycle as it occurs in any one cylinder it may be assumed that the piston is at the top of the stroke and that both the inlet and the exhaust valves are closed.As the piston descends the inlet opens so that charge of mixture can flow into the cylinder. This is called the suction(or induction)stroke, the charge flowing under the influence of external atmospheric pressure.Immediately after the piston has reached its lowest position and begins to rise again the inlet valve is closed so that the mixture can be compressed by the rising of the piston on the compression stroke As the piston once again approaches its topmost position an electric spark is caused to pass between the points of a sparking plug located in the top of the cylinder in a zone called the combustion chamber.The spark ignites the mixture and as both valves are closed during its combustion, there is a considerable pressure rise.As a result, the piston is forced back again down the cylinder, this movement being termed the expansion or power stroke 翻译:为了描述在任何一个汽缸里发生的完整的工作循环，可以假设活塞处于冲程的顶部， 进气阀和排气阀关闭。随着活塞下降，进气阀打开，以便混合气体燃料能流进汽缸。这过程 被称为进气冲程(或感应冲程)，燃料受外部大气压力的影响流动。在活塞已经到达最地位 置后，活塞立即再次上升，进气阀关闭，以便混合气体被上升的活塞压缩，称为压缩冲程。 随着活塞上升到接近最高位置，一个电火花被打着，从火花塞的顶尖穿过，火花塞位于被称 为燃烧室的区域的汽缸的顶部。火花点燃混合气体，随着两个气阀在燃烧时关闭，有巨大的 压力上升。结果，活塞再次被压回汽缸，此运动被称为膨胀冲程或动力冲程。 Before the piston reaches its lowest point, the exhaust valve is opened, pressure is released, and as the piston again rises it sweeps the residual gas through the exhaust outlet, whence it is led through a silencer to the atmosphere; this is the exhaust stroke which completes the continuously repeated cycle.Thus it will be seen that there is one power stroke for every four strokes of the piston or two revolutions of the crankshaft. 翻译:在活塞达到最低点时，排气阀打开，压力释放，随着活塞再次上升，活塞把残余气体 压向排气出口，这里，排出气体经过一个消声器被导进大气;这是排气冲程，完成不断连续 重复的循环。因而，可以看出活塞的每4个冲程或曲轴的两转有一个动力冲程。 It should be noted that the size of the combustion chamber above the piston (known as the clearance space )is considerably smaller than that part of the cylinder in which the piston travels. Thus at the end of the compression stroke the explosive mixture is compressed to a pressure varying from about 5. 5 to 7kg/cm2(80 to 100 lbf/in2).By such compression the mixture is heated to some extent, resulting in better vaporisation of the fuel, and more intimate mixing of the vapor and air; it also enables the engine to work with higher thermal efficiency, to which further reference is made later. 翻译:应该注意活塞上面燃烧室的大小(被人称为间隙空间)比汽缸里活塞行程的那部分相 对要小一些。因而，在压缩冲程结束时，混合可燃气体被压缩到大约5.5--7 kg/cm2 (80 - 100 lbf/in2)的压力。通过这种压缩，混合气体被加热到一定程度，使燃料汽化更好，并使空气和 燃料汽的混合更精细，这也使发动机以更高的热效率做功，后面文章会对热效率作进一步的 解释。 Incidentally, the ratio of the total volume of the cylinder above the piston when it is in its lowest position to that of the combustion or clearance space when it is at its highest position is known as the compression ratio and in modern commercial vehicle petrol engines varies from about 6:1 to 8:1. 翻译:顺便提一下，活塞最低位置时汽缸的总容量和活塞最高位置汽缸燃烧时的容量或间隙 空间的比率被称为压缩比。现代商用车的汽油发动机的压缩比范围从大约6:1到8:1。 The operating cycle of the four-stroke diesel is identical in so far as the sequence of strokes is concerned but there is a major difference in principle.On the induction stroke only pure air is drawn into the cylinder through the inlet valve port.Then, because the clearance space is so much smaller than that in a corresponding petrol engine, the compression ratio is considerably higher, being not less than 12:1 and even in some engines as high as 21:1.The final pressure of the air charge at the end of the compression stroke may be 35kgf/cm2(500 1bf/in2)or more, with a corresponding temperature rise to not less than 1000?F(538?), which is sufficient to ignite finely atomized but non-volatile fuel oil without the assistance of an electric spark. 翻译:4冲程柴油机的工作循环就冲程顺序而言是相同的。但是原理上有一个重要的差别。 在感应冲程，只有纯净的空气通过进气阀口吸进汽缸。那么，因为间隙空间比相应的汽油发 动机的要小的多，其压缩比相当高，不低于12:1，甚至有些发动机达到21:1。压缩冲程结 束时冲气的最终压力可能为35kgf/cm2(500 1bf/in2)或更高，随着相应的温度上升到至少 1000?F(538?)，足以点燃精细雾化的但尚未挥发的燃油，无须电子火花塞的辅助。 Just before the piston reaches the end of the compression stroke the fuel oil is injected into the combustion chamber through an injection nozzle, or sprayer, mounted on the cylinder head in much the same position as the sparking plug in a petrol engine.The pressure at which the fuel is injected must necessarily, of course, be higher than the combustion pressure , usually not less than 140 kgf/cm2(2000 1bf/in2).During injection the fuel is split up into finely divided particles, and the mixture of these with the air forms an explosive charge that is ignited by the heat of compression. 翻译:在活塞到达压缩冲程结束前，燃油通过一个喷射喷嘴或喷雾器被喷射入燃烧室，喷嘴 或喷雾器安装在缸盖上，和汽油发动机上火花塞的位置完全相同。燃油喷射的压力当然且必 须比燃烧压力高，通常至少达到140 公斤力/平方厘米kgf/cm2 (2000 磅力/平方英寸 1bf/in2) 喷射时，燃油被碎成微小颗粒，这些颗粒和空气的混合体形成爆炸(可燃)气体，被压缩的 热量点燃。 Injection is continued for a short period, during which the piston passes its highest position and begins to descend on the power stroke.The expansion of combustion products only begins to have effect when the piston has passed the top of its stroke, and during the injection period the burning fuel maintains a more or less constant pressure somewhat above that of compression; When the fuel is cut off expansion of the gases continues, the pressure is falling as the piston descends.The overall effect on the piston is a more sustained pressure than that associated with the combustion process in a petrol engine.The effective part of the power stroke is concluded before the piston descends to its lowest point, and the cycle is completed when the exhausted gases are expelled by the rising piston. 翻译:喷射持续很短的时间，此时活塞经过最高位置，开始下降到动力冲程。当活塞已经通 过压缩冲程的顶部时，燃烧物的膨胀才开始起作用，喷射期间，燃烧的燃油保持较稳定的压 力，稍微高于压缩压力;当燃油被切断，气体继续膨胀，压力随活塞的下降而下降。对活塞 的总的作用是与汽油发动机里和燃烧过程相关的压力相比具有一个更稳定的压力。动力冲程 的有效部分在活塞下降到最低点前结束，当废气被上升的活塞排出时，循环完成。 To inject the fuel a special type of pump driven by the engine is employed, and this is a distinguishing feature of the diesel engine, just as the carburettor and the magneto or coil and distributor ignition apparatus distinguish the normal petrol engine. 翻译:燃油的喷射靠使用一个由发动机带动的专用型式的泵来实现的。这是柴油发动机一个 明显的特征。而化油器、磁发电机或线圈和分配器点燃装置显示出正常的汽油发动机的特点。 Horsepower 马力 An engine produces power only when a load is applied.When the engine first starts, the load applied is in the form of its own friction and compression.The resistance offered by various accessories also affects this initial load .an engine must drive a fan, generator, injection pump, water pump, perhaps a compressor too.All of these add to the load on an engine before you apply that toad at the output shaft.We’ve said that an engine produces power when a load is applied.What, exactly, is power? Power is the capacity of an engine to do work.WOEK is defined as moving an applied force through distance.Power is work with the element of time added or how long it took to do the work.Horsepower is the measure of power.One horsepower is a measurement of the force required to lift 33, 000 lbs a distance of one foot in one minute. 只有给发动机增加负载时，发动机才发出功率。发动机第一次启动时，增加的负载是自我摩 擦和压缩。各种附件施加的阻力也影响这初始的负载。发动机必须带动风扇，发电机，喷射 泵，水泵，或许也带动一台压缩机。在你把负载加到输出轴上之前，所有这些阻力都加在发 动机的负载上。我们曾说只有给发动机增加负载时，发动机才发出功率。准确的说，什么是 功率,功率是一台发动机做功的能力。做功被定义为把一个作用力移动一定的距离。功率是 单位时间内所做的功或花多长时间的做功。马力是功率的单位。一马力等于在一分钟时间内 提起33, 000磅的重量通过一英尺的距离所要求的力的大小。提起33, 000磅的重量在一分钟 时间内通过一英尺的距离时功率的计量单位。 Horsepower shows up in engine rating specs under several names .It may be listed on these specs as maximum, intermittent, continuous or gross horsepower.How do these terms differ. 马力在发动机标定值规格中有不同的名称。在标定值规格表中可能列为最大马力，间隙马 力，连续马力或总马力，这些术语有什么不同呢, Gross horsepower is a measure of the power units , produced by a bare engine, with no power drain caused by accessories.Manufacturers often use this measure to establish a base line when setting up engine ratings because this method eliminates the variables imposed by different accessories, which may or may not be used on that particular engine in actual service. 总马力是一台没有附件功率消耗的裸机的功率单位，制造商在设定发动机额定功率时经常使 用此单位确定基准线。本方法可以消除不同附件产生的影响，在某一特定发动机的实际运用 中，这些附件可能使用，可能不使用。 Net or flywheel horsepower represents the power units produced by a fully-equipped engine at the output shaft or flywheel. 净功率或飞轮马力是功率单位，表示一台完全装配的发动机在输出轴或飞轮轴上输出的功率 Brake horsepower is another term you may come across while puzzling over an engine rating chart.This simply means the power, available at the output shaft for doing work and is the same as net horsepower .The term is a hold-over from the days when the brake horsepower was actually measured on a form of a brake device called a Prony brake.Today a dynamometer is the instrument most often used and now you know why some people still can a dynamometer a brake. Performance curves can be confusing.Knowing what each curve represents can do much to eliminate this confusion. Maximum brake horsepower curve is the curve showing the highest horsepower that an engine will develop at any rpm within its range. Normally this curve is used for engines which must produce peak power for short periods of time or for special applications. 制动马力是你在研究发动机额定功率值图表时会碰到的另一个专业术语。简单的说，它就是 做功时输出轴能提供的功率，而且等同于净功率。此术语是从过去沿用下来的，当时制动马 力在实际运用中用一个被称作普龙尼制动闸的制动装置进行测量。今天，测功机是最常用的 设备，现在你知道为什么一些人仍然把测功机称为制动闸(刹车)。性能曲线使人困惑。如 果知道每条曲线代表的意思会非常有助于消除这种困惑。最大制动马力曲线(极限外特性曲 线)是表示一台发动机在允许的每分钟转速范围内发出的最高马力曲线。正常情况下，此曲 线用于发动机在短时间内或特殊用途中必须发出最高功率 Intermittent brake horsepower curve is normally about 90% of the maximum and is the horsepower curve recommended or satisfactory operations under certain conditions of load and speed, usually variable load and speed conditions where top load and speed are only needed for short periods. “Intermittent” curves are the ones most often used for vehicular applications. 间隙制动马力曲线(瞬时外特性曲线)通常大约是最大马力的90%，是在某负荷和速度条 件下进行良好运行而推荐的马力曲线，通常此条件是变化的负荷和速度条件，最大负荷和最 高速度只在很短的时间内需要，间隙曲线是汽车运用中最常用的曲线。 Continuous brake horsepower curves are about 80% of maximum and are the curves recommended for satisfactory continuous operation. A generator set is an example of an application in which the continuous brake horsepower curve might be used. Drawbar horsepower is a term commonly found in tractor engine ratings and is a measurement of the power developed at the tractor’s drawbar, Drawbar horsepower is found by measuring the horizontal drawbar pull and the exact tractor traveling speed. 持续制动马力曲线大约是最大马力的80%，是进行持续良好的运行而推荐的曲线，发电机 组是使用持续制动马力曲线的一个实例。牵引马力是一个拖拉机发动机额定功率值里都能找 到的一个专业术语，是拖拉机牵引所发出的的功率的功率单位。牵引马力是通过测量水平牵 引力和拖拉机实际行驶速度所求的。 4.Torque and Fuel Consumption 力矩和燃油消耗 We’ve already said that horsepower is a measure of an engine’s ability to produce power.There’s another term you should understand which influences an engine’s ability.Independent of horsepower, to do a specific job.This is torque. 我们曾说马力是一台发动机产生动力的能力的测量单位。你应该了解另一个影响发动机做具 体工作的能力、与马力无关的专业术语。这就是力矩。 Torque. When a force is applied at right angles to a radius of a wheel or to the end of a lever, it creates a twisting force called torque.Torque is measured in pound/in. or pound/ft. 力矩. 当一个作用力与轮子的半径或与杠杆的一端成直角时，他产生一个旋转力，被称为力 矩。力矩用磅/英寸或磅-英尺作为测量单位。 If a force of 50 1bs is applied to a 6-in crank, torque created in the crankshaft would be 50x6=300 1b-in.Or 50x0.5(6 in.=0.5ft)=25 1b/ft. If the crank is 12 inches long, torque would be doubled although the force remains the same.Torque is increased by an increase of either the force applied， Or its distance from the center of rotation. 假设一个50磅的力施加到一根6英寸的曲轴上，曲轴所产生的力矩应该为50x6=300磅-英 尺，或50x0.5(6 英寸=0.5英尺)=25 磅-英尺。假设曲轴长度是12英寸，虽然作用力保持不 变，力矩将会翻一倍。力矩或者随着作用力的增加而增加，或者随旋转中心的距离的增加而 增加。 Torque, any force in fact, can be applied without work being done.(Either time and/or motion is missing). Suppose that in our example above, the 50-1b force exerted at the crank at a 6-in . Radius was insufficient to turn the shaft when it has a heavy connected load.A higher torque is required to start the load. 力矩，实际上任何力，可能施加而不做功。(要么损失时间或/和要么损失运动)。假设在以 上的实例中，50磅的力施加到6英寸的曲轴上，当它连着一个重负荷时，半径不足以使曲 轴转动，那么，要求更高的力矩以启动负荷。 To illustrate the point, have you ever tried to open a jar of olives and failed? You turn the lid as hard as you can but it doesn’t open. You’re applying torque to the lid, but since it’s not turning(no motion), you’re not doing any work no matter how hard you’re trying to turn the thing. 为了说明这一点，你是否曾试图打开一罐橄榄但无法打开, 你使劲旋转罐盖，但打不开。 你正施加力矩到灌盖上，但是，因为罐盖没有转动(没有运动)，无论你怎样使力转动东西， 你却没有做功。 Now, you take a pair of pliers and turn the lid. It comes off easily , why? Extending the radius at which the force was appalled (the distance in this case from the center of the lid to the end of the pliers handle ) multiplies your torque and overcomes the resistance of the lid. Now, when the lid turns, work is being done. 现在，你拿起一副钳子，并转动罐盖。罐盖容易地取下来了，为什么,延长力的作用半径， (本实例从罐盖的中心到钳把一端的距离),成倍增加了你的力矩并克服了罐盖的阻力。现在, 当罐盖转动时，力就做了功。 So you see, the torque produced by an engine, independent of its horsepower, is an important characteristic by which to judge its ability to do a job.TORQUE RISE is the ability of an engine to produce additional torque at reduced rpm, partially compensating for the loss in speed. 所以你明白，发动机产生的力矩是判断其工作能力的一个重要特性，和马力无关。力矩上升 是发动机在降低转速的条件下，产生附加力矩来部分补偿速度损失的能力。 There are a few other terms you should remember before getting into the rating articles. After we’ve reviewed them, we’ll relate some of the terms to an actual engine in operation. 在进入标定功率章节前，有其他几个术语你应该记住。在我们看过这几个术语后，我们将把 其中的一些术语同实际运转的发动机联系起来。 PISTON SPEED in today’s high-speed engines, about 1700 to 2400 feet per minute is one way of determining whether an engine is really “high-speed” or not.Piston speed is determined by multiplying twice the stroke (in feet)by the engine’s rpm. Piston speeds beyond today’s state of the art may tend to increase cylinder wear. 活塞速度 在现代高速发动机中，用每分钟大约1700—2400英尺来确定一台发动机是否为 真正的高速发动机的一种方法。活塞速度用发动机每分钟转速乘以两倍的冲程(英尺)求得。 超出今天技术发展水平的活塞速度可能有增加汽缸磨损的趋向。 BRAKE SPECIFIC FUEL CONSUMPTION.This is an accurate guide by which to judge different engines in terms of fuel consumption.The BSFC is determined by measuring the number of POUNDS of fuel consumed per brake horsepower hour at a standard set of conditions.This offsets the influence of such variables as altitude, temperature, and also fuel weight per gallon.yes, this varies with the fuel’s specific gravity.The BSFC also allows a fair comparison of engines of different horsepower, in terms of fuel economy. 制动器(马力小时)比油耗(制动马力燃油消耗率,制动马力比油耗)。这是根据燃油消耗判 断不同发动机的一个准确的指标。制动马力比油耗是通过在一整套条件下测量每一制动 马力小时的耗油磅数而确定的。这样消除了像海拔高度，温度和也包括每加仑燃油重量的差 异的影响。是的，燃油重量会随燃油的比重而变化。制动马力比油耗，也允许根据燃油的经 济性，对不同马力的发动机进行公平的比较。 BRAKE MEAN EFFECTIVE PRESSURE is the theoretical average that must be exerted on the pistons during power stroke which would produce an output equal to the brake horsepower.In fact , it is calculated by working backward from the measured brake horsepower.BMEP is sometimes used as a measure of how efficiently an engine is utilizing its piston displacement to produce power. 制动平均有效压力 是做功冲程时作用在活塞上的理论平均压力，其所产生的输出功率等于 制动马力。实际上，它是从测得的制动马力通过反算法计算出来的。制动平均有效压力有时 可以作为衡量发动机是否有效利用活塞排量产生功率的一个指标。 Efficiency 效 率 That the Diesel engine is receiving much public attention is due mainly to its unusual thermal efficiency and to the fact that a Diesel of a given design will show almost identical efficiency whether it be a 25-hp or a 5000-hp unit. There may be variation in actual operation, but these variations are traceable to the character of the operation . 柴油发动机得到公众的注意主要是因为其不寻常的热效率和因为不管是25马力或500马力 的发动机，既定设计的发动机显示几乎相同的热效率的事实。在实际运行上可能有差异，但 是这些差异来自运行的特性。 It should be understood , in addition, that slow-speed and high-speed Diesel may not actually be followed the same cycle. The slow-speed air-injection Diesel followed the “Diesel ” or constant-pressure cycle, wherein the fuel was introduced and burned at a rate such that the cylinder pressure did not rise during the combustion period (about 10 percent of the power stroke)but remained constant, and equal to the final compression pressure。 另外，人们应该理解，低速和高速柴油机的工作循环实际上是不相同的。低速空气-喷射式 柴油机是柴油循环，或定压循环，在循环中燃油被导入，以一定比率进行燃烧，燃烧期间汽 缸压力不增加，(大约动力冲程的10%)，但是(汽缸压力)保持稳定，并等于最终压缩压 力。 High-speed solid-injection Diesels of modern design, burn the fuel charge while the piston is practically stationary. At the start of the power stroke, that is , there is no increase in the volume of the gases during combustion, but the pressure rises greatly.Combustion is then at constant volume, and consequently, the high-speed Diesel operates on the Otto cycle, The cycle, since it involves compression far above that of the standard，Spark-ignition gasoline engine, might well be termed the “Diesel-Otto Cycle.” 现代设计的高速无气喷射(机械喷射)式柴油机，实际上，是在活塞固定不动时燃烧供送的燃 料的。在动力冲程开始时，就是说，燃烧时气体的容量没有增加，但是压力增加很大。此时 燃烧的容积是固定的，因此，高速柴油机以奥托循环工作。因为它涉及的压缩力远高于火花 点燃的汽油机的标准的压缩力，此循环被称为“柴油机奥托循环”。 Compression-----This process is the cornerstone of the success of the modern internal-combustion engine , The need for it was supported on theoretical grounds by Beau de Rochas, in the face of opposition from “practical” men like Lenore who would not understand how an engine could be expected to give more power ，it had to absorb power in the compression process.Just as the higher, compression of the first thoroughly practical gas engines gave them a pronounced advantage over the Lenoir non-compressing machine. 压缩-----此过程是现代内燃机成功的首要因素。布地罗卡斯的理论支持需要压缩。持反论的 实践派人士，如李诺尔，不理解如何期待发动机发出更多的功率，压缩过程必须消耗功率。 随着使用更高的压力，首台完全实用的使用压缩的燃气机，同李诺尔无压缩的机器相比，具 有显著的优势。 So the modern Diesel engine, with a compression ratio two or four times that of the gas or gasoline engine, represents a notable technical advance over the latter. 所以，现代柴油发动机，压缩比是燃气发动机或汽油发动机的2或4倍，同后者相比，它代 表了技术显著的进步。 Every effort is made to raise the compression of gas engine for corresponding reasons, but it is impossible to go very far in this direction because the gas or vapor mixture pre-ignites as soon as a pressure of about 120 lb per sq. in is reached.No such limitation is placed on the Diesel engine, because it compresses fresh air, fuel being introduced only towards the end of compression process. 基于相应的原因，人们努力提高燃气发动机的压缩力，但是，因为只要每平方英寸的压力达 到120磅，混合气体或混合蒸汽就会预燃，所以，压缩不可能超出此限制太远(离此方向太 远)。柴油发动机没有此限制，因为柴油机压缩新鲜空气，燃油只在压缩过程结束前才被导 入。 Diesel compression can，therefore, be carried high enough not only to obtain the highest efficiency，but also to produce a temperature high enough to insure automatic ignition of the fuel as soon as it is introduced. 所以，柴油机的压缩力, 能达到很高，不仅可以获得最高的效率，而且产生足够高的温度， 保证燃料一导入就自燃。 The efficiency of any internal-combustion engine depends on the final compression pressure for a number of reasons. 任何内燃发动机的效率，因诸多原因，依赖最终的压缩压力而定。 If the charge in an internal-combustion engine is crowded into a small space (the clearance, or combustion chamber),with the piston at or near the dead center, the surface of the metal in contact with fire is greatly decreased, while the loss of heat is correspondingly curtailed . It is true, of course, that the ratio of surface to volume is greater in the case of the compressed charge, but as the total surface is less than it would be with combustion carried out in a large portion of the cylinder volume, the resulting opportunities for heat transmission are less. Moreover, the greatly increased density of the charge resulting from high compression increases the speed of combustion and shortens the time interval during which the high temperature of the flame is available for causing heat flow into the metal surfaces. High compression, therefore, makes it possible to obtain a high temperature of combustion with minimum transmission of heat to the cylinder walls and head, Much more mechanical work (power) is obtainable from a given quantity of high-temperature heat than from the same quantity of low-temperature heat. 如果充入内燃机内的燃料，在活塞处于或靠近上死点时，挤压在一个狭小的空间里，(间隙 或燃烧室)，那么，同火接触的金属表面就大大减少，这时，热损失相应减少。当然，表面 容量比在压缩燃料时比较大，但是，随着总表面比在大部分汽缸里进行燃烧时小，所以由此 引起的热传递的机会较少。可是，因为很高的压缩力致使充入的燃料的密度大大增加，燃烧 的速度也会大大提高，这样缩短了火焰高温引起的热流进入金属表面的时间间隔。所以，高 压缩力使柴油机可能获得很高的燃烧温度和到汽缸壁及缸盖的热传递最小。与同量的低温热 相比，高温热可以获得多得多的机械功(动力)。 The work necessary to compress the cylinder contents is not a complete drain on the power resources of an engine. Every foot-pound of work absorbed during the compression is returned, less small friction loss, during the expansion stroke, the latter, of course, producing an excess of work corresponding to the heat input due to the combustion of fuel. 压缩汽缸混合燃料所需要的功在发动机的动力资源里并没有完全消耗掉。压缩期间吸取的每 英尺-磅的功在膨胀冲程期间被送回来，摩擦损失较小，后者(在膨胀冲程期间)，当然，因 为燃料的燃烧，会产生与热输入相关的额外的功。 If no fuel is consumed, the expansion process theoretically, coincides with the compression process, and the engine has neither gained nor lost energy between the beginning of compression and the end of expansion. High temperature at the end of compression is paid for with only a small net less of work corresponding to friction. If the same temperature were to be attained by the combustion of fuel, the latter would be a total loss from the viewpoint of power production. Roughly speaking compression saves the same amount of fuel as would have to be burnt in order to elevate the air to that temperature which is imparted to it by compression. 如果没有燃料消耗，膨胀过程理论上同压缩过程是相同的，在压缩开始和膨胀结束之间发动 机既没有获得能量，也没有损失能量。在压缩结束时获得高温，只有与摩擦相关的一小部分 的净功受到损失。如果通过燃料的燃烧获得相同温度，那么，从产生动力的角度看，后者(燃 烧的燃料)将会完全损失掉。粗略地讲，因为压缩使空气温度升高，所以压缩节省了和将要 通过燃烧获得同样高温度的等量的燃料。 Engine Classification (1) 发动机分类 (上) Before you study the detailed construction of the engine parts, you should know something about the several classes into which diesel, dual-fuel and gas engines may be divided. We can classify the engines in several ways: (1)Operating cycle. (2)piston action. (3) piston connection. (4) cylinder arrangement. (5)method of fuel injection, and (6) speed. 在你研究发动机不见的详细结构前，你应该知道发动机的几个类别:柴油机，双燃料发动机， 和燃气发动机。我们可以用以下几种方式对发动机进行分类:(1) 工作循环 (2) 活塞作用 (3) 活塞连接 (4) 汽缸排列 (5) 燃料喷射方法和 (6) 转速 Operating Cycle. Diesel and gas-burning engines can be divided into two groups based on the number of piston strokes per cycle, either four or two. An engine which needs four strokes to complete one cycle is a four-stroke cycle engine or for short, a four-cycle engine. If it needs only two strokes to complete a cycle we call it a two-stroke cycle engine or, for short, a two-cycle engine. Thus, a two cycle engine fires twice as often as a four-cycle engine. 工作循环:根据每循环活塞冲程数，或2循环或4循环，可将发动机分为柴油机和燃气机两 类。需要4个冲程完成一次循环的发动机是4冲程循环发动机，或简称4冲程发动机。如果 发动机仅需要2冲程完成一次循环，我们把它成为2冲程循环发动机，或简称2冲程发动机。 因此，2冲程发动机点火次数是4冲程发动机的2倍。 Two-cycle engines are further classified according to the method used to supply the engine with fresh air. You learned that air at a pressure slightly above atmospheric must be forced into working cylinder to blow out the spent gases and to fill the cylinder with fresh air. His scavenging air is obtained, in some two cycle engines, by using the crankcase and underside of the piston as an air compressor . This is called crankcase scavenging. Scavenging air in other engines is supplied by blowers or pumps; this is called blower scavenging or pump scavenging, respectively. 2冲程发动机可根据通常为发动机供给新鲜空气的方法进一步分类。你知道，必须将略高于 大气压的空气压入工作汽缸，从而排除废气，充入新鲜空气。在某些2冲程发动机中，发动 机的排气(扫气)可以把曲轴箱和活塞以下部位用作空气压缩机来完成。这种情况被称为曲 轴箱扫气。其他发动机上的扫气通过鼓风机(气泵)来完成，这种情况分别称为鼓风机扫气 或气泵扫气。 Piston Action. An engine’s piston action may be classified as (a)single-action, (b)double-action or (c)opposed-piston. Single-acting engines use only one end of the cylinder and one face of the piston to develop power. This working space is at the end away from the crankshaft (that is, at the upper end of a vertical engine) . All of the engines shown so far in this book are single-acting engines , and develop power on the downstroke . 活塞作用 发动机的活塞作用分类为:(a)单作用 (b)双作用或 (c)对置活塞 单作用发动机仅使用汽缸的一端和活塞的一面产生动力。工作空间在远离曲轴的那一端。(就 是在立式发动机的上端)。到目前为止，本书所列举的所有发动机都是单作用发动机， 在下 行冲程中产生动力。 Double-acting engines use both ends of the cylinder and both faces of the piston to develop power on the upstroke as well as on the downstroke . The construction complicated, therefore double-acting engines are built only in large and comparatively low-speed units, generally to power motorships. 双作用发动机使用汽缸的两端和活塞的两面在上下冲程中都产生动力，其结构复杂，所以， 双作用发动机只用在大型且相对低速装置中，一般作为船舶动力。 An opposed-piston engine has cylinders in each of which two pistons travel in opposite directions. The combustion space is in the middle of the cylinder between pistons. There are two crankshafts: the upper pistons drive one, the lower pistons the other. Note that each piston is single-acting. That is it develops power with only one face of the piston. 对置活塞发动机的每一个汽缸有两个活塞，沿相反方向运动。燃烧空间位于两活塞之间的汽 缸的中部(汽缸的中部的活塞中)。有两根曲轴:上面的活塞驱动一根，下面的活塞驱动另 一根。注意每个活塞是单作用。也就是说，只用活塞的一面产生动力。 Piston Connection. The piston may be connected to the upper end of the connecting rod either directly (“trunk-piston” type) or indirectly (“crosshead”type). In trunk-piston engines, a horizontal pin within the piston is encircled by the upper end of the connecting rod . This is by far the most common construction. 活塞连接 活塞或直接(筒状活塞型)或间接(十字头式活塞型)地与连杆的上端连接。在筒状活塞的 发动机里，活塞里的一根水平销被连杆的上端所包住。这是目前位置最普通的结构。 In crosshead-type engines, the piston fastens to a vertical piston rod whose lowered is attached to a sliding member called a “crosshead”, which slides up and down in guides. The crosshead carries a crosshead pin which is encircled by the upper end of the connecting rod. This more complicate construction is required in double-acting engines. It is also used in some large, slow-speed, single-acting engines. 在十字头式活塞的发动机里，活塞连接在一根垂直的活塞杆中，活塞杆的下端又连接在一个 称为“十字头”的滑动构件上，十字头在导轨里上下滑动。十字头的上端有一个被连杆上端裹 住的十字销。在双作用的发动机上要求这种更复杂的结构。它也用在一些大型、低速、单作 用的发动机上。 Engine Classification(2) 发动机分类 Cylinder Arrangement. A diesel or gas-burning engine has its cylinders arranged in one of several ways. For basic cylinder arrangements are: (a) cylinders-in-line (b) V arrangement, (c) flat and (d)radial. 汽缸排列 柴油机或燃气机是若干方式之一排列的。其基本汽缸排列为:(a) 直列式 (b) V 型排列 (c) 平列式(d)星型。 A Cylinders-in-line Arrangement. This is the simple and most common arrangement, with all cylinders arranged vertically in line. This construction is used for engines having up to 12 cylinders. Engines are also built with horizontal cylinders, usually one or two , in a few cases with three cylinders. 直列式汽缸排列 这是简单且最普通的排列方式。所有汽缸垂直排列成行。此结构用于汽缸数达到12个的发 动机。(直列式)发动机的制造也用水平汽缸的排列方式，通常为单缸或双缸，少数情况下 为3缸。 If an engine has more than eight cylinders, it becomes difficult to make a sufficiently rigid frame and crankshaft with an in-line arrangement. Also the engine becomes quite long and takes up considerable space. The V-arrangement with two connecting rods attached to each crankpin, permits reducing the engine length by almost one-half, thus making it much more rigid, with a stiff crankshaft. It also costs less to manufacture and install. This is a common arrangement for engines with eight, twelve, and sixteen cylinders. Cylinders lying in one line are called a “bank”, and the angle A between the banks may vary, in manufacturing practice from 30? to 120?, the most common angles being between 40? and 75? (A complete circle is 360). 如果发动机汽缸多于8个，用直列式排列很难制造出钢性够强的机架和曲轴。发动机也变得 很长，体积大。(占用相当大的空间)V型排列因为每个连杆颈连2根连杆，可以使发动机 的长度几乎缩短一半，所以，使机架钢性更强，使用硬度高(坚固)的曲轴。也使制造和安 装成本更低。这是8缸，12缸和16缸发动机的普通的排列方式。排成一行的汽缸称作“列”。 列与列之间的角度A可以变动，实际制造中，从30?到120?之间变化，最普通的角度在40? 和75?(完整一圈是360?)。 A flat engine is a V-engine with the angle between the banks increased to 180? deg. This arrangement is used where there is little headroom as in trucks, buses and rail cars . flat engines are also called “opposed-cylinder” engines. Don’t confuse this with the “opposed-piston” engine previously described. 平列对称发动机是汽缸列与列之间的夹角增至180?的V型发动机。此排列在上部空间较小 的地方使用，如在汽车，班车，有轨汽车上使用。平列对称发动机也称为“对置汽缸”发动机。 (“一字开汽缸”发动机)。不要混淆“对置汽缸”和前面描述的“对置活塞”。 In a radial engine all the cylinders are set in a circle and all point(piston)toward the center of the circle. The connecting rods of all the pistons work on a single crankpin which rotates around the center of the circle. The name radial is given because each cylinder is set on a radius of the circle, that is , a line from the center of the circle to its circumference. Such a radial engine occupies little floor space. By attaching the connecting rods to a master disk surrounding the crankpin, as many as twelve cylinders have been made to work on a single crankpin. 在星型发动机里，所有的汽缸排列成一个环形，且所有的点(活塞)指向环形中心。所有活塞 的连杆连在围绕环形中心的旋转的曲柄销上工作。取名“星形”是因为每个汽缸都置于园的半 径上，即园心到园周的直线上。此种星型发动体积小(占用空间小)。通过把所有的连杆连 接到一个曲柄销套住的主盘上，一根曲柄销可使12个汽缸工作。(可使12个汽缸在一根曲 柄销上工作)。 Method of Fuel Injection. Diesel engines are divided into air-injection engines and solid or mechanical-injection engines. Air-injection engines use a blast of highly compressed air to blow the fuel into the cylinder. Air injection was commonly used on early diesel engines but with the development of solid-injection systems the air-injection engine is rapidly disappearing. 燃油喷射方法 柴油发动机被分为空气喷射发动机和无气喷射(液体式)或机械喷射式柴油机。空气喷射发 动机使用一股高压缩的空气气流把燃油送到汽缸。空气喷射一般使用在早期柴油机上，但是 随着无气喷射系统的开发，空气喷射发动机正在迅速淘汰。 Speed. All diesel and gas-burning engines may be divided into three classes according to speed; low-speed, medium-speed, and high-speed engines. Although no precise definitions of these terms have been agreed upon, this book refers to engines operating at speeds below about 350 rpm as low-speed, and those above 1,200 rpm as high-speed. Automotive diesel engines often run faster than 1,200 rpm, but the great majority of other engines run between 350 and 1,200 rpm and are termed medium-speed engines. 速度 根据发动机的转速，所有的柴油和燃气发动机可分成三类:低速，中速，和高速发动机。 虽然这些术语没有达成精确的定义，本书把转速低于350 rpm的发动机称为低速发动机，高 于1200 rpm的发动机称为高速发动机。汽车用柴油机的转速通常高于1200rpm，但是绝大 多数的其他发动机的转速在350到1200rpm之间，被称为中速发动机。 Engine parts 发动机零件 An understanding of the operation or purpose of the various parts is necessary for a complete understanding of the whole engine. Each part or unit has its special function to perform and in conjunction with other parts makes up a diesel engine. A person who wants to operate, repair, or otherwise service diesel engines must be able to recognize the different parts by sight and know what their particular functions are. A knowledge of the engine parts will be gradually acquired, first by reading attentively the following sections and later by looking up in them Glossary at the end of the book every term not sufficiently familiar from a reading of the corresponding chapters. 了解发动机各个部件的工作情况及其用途，对于全面理解整个发动机是必要的。每个零件或 总成都有其专门的功能，并与其它零件一起构成一台柴油发动机。一个想操作、维修发动机 或发动机其他方面服务的人必须通过外观就能认出不同的零件，且知道这些零件的具体功 能。发动机各部件零件的知识是逐步获得的首先，精读以下章节，然后，在本书后的术语表 里查找在阅读相关章节时(碰到的)每个不太熟悉的术语。 Diesel engines vary in outer appearance， size, number and arrangement of cylinders, and details of construction. However, they all have the same main parts which, though they may look different, all perform the same functions. Each diesel engine has only a few main working parts; the auxiliary parts are necessary to hold the working parts together or to assist the main working parts in their performance. The main working parts are (a)the cylinder; (b)the cylinder head, usually holding inlet and exhaust valves; (c) the piston; (d)the connecting rod; (e)the crankshaft; (f)the crankshaft or main and connecting-rod bearings; and (g) the fuel pump and fuel nozzle. 各种柴油机的外观，尺寸，汽缸数目和排列形式，及零件的结构细节是各不相同的。可是， 他们的主要部件是相同的，虽然外观各异，但功能却相同。每抬柴油机都只有几个主要工作 部件，为了使工作部件连成一体，或为了帮助主要工作部件的工作，需要一些附件。主要工 作部件为:(a)汽缸，(b)缸盖，通常带有进排气阀，(c)活塞，(d)连杆，(e)曲轴，(f) 曲轴轴承，或主轴瓦和连杆瓦，燃油泵和燃油喷嘴。 Cylinder. The heart of the engine is the cylinder, where the fuel is burned and the power developed. The inside of the cylinder is formed by the liner, or sleeve.The inside diameter of the cylinder is called the bore. 汽缸 汽缸是发动机的心脏，燃油在汽缸里燃烧，并产生动力。汽缸内壁装有缸套或套筒。汽缸的 内径称为缸径。 The cylinder head closes one end of the cylinder and often contains the valves through which air and fuel are admitted and the exhaust gases discharged. 汽缸盖封闭汽缸的一端，通常包括气阀，通过气阀吸入空气和燃油，排出废气。 Piston. The other end of the working space of the cylinder is closed by the piston that transmits to the crankshaft the power developed by the burning of the fuel. Piston rings lubricated with engine oil produce a gastight seal between the piston and the cylinder liner. The distance that the piston travels from one end of the cylinder to the other is called the stroke. 活塞 活塞封闭汽缸工作空间的另一端，并把燃料燃烧产生的动力传递给曲轴。用机油润滑的活塞 环在活塞和汽缸套之间形成不漏气的密封。活塞从汽缸的一端到汽缸的另一端所通过的距离 被称为冲程。 Connecting Rod. One end, called the small end of the connecting rod, is attached to the wrist pin or piston pin located in the piston. The other or big end has a bearing for the crankpin. The connecting rod changes and transmits the reciprocating motion of the piston to the continuously rotating crankpin during the working stroke and vice versa during the other strokes. 连杆 被称作连杆小头的一端，与位于活塞中的肘节销或活塞销相连。连杆的另一端或大头有一个 曲轴的轴瓦。在做功冲程时，连杆把活塞的往复运动转变成曲轴销的连续的旋转，在其他冲 程时，恰好相反。 Crankshaft. The crankshaft turns under the action of the piston through the connecting rod and crankpin located between crank webs, or cheeks, and transmits the work from the piston to the driven shaft. The parts of the crankshafts supported by and rotating in the main bearings are called the journals. 曲轴 曲轴通过连杆和位于曲柄或称为曲柄颊之间的曲轴销在活塞的作用下转动，并把活塞所做的 功传递给驱动轴。曲轴上主轴瓦支撑的和在其中旋转的部分被称为主轴颈。 A flywheel of sufficient weight is fastened to the crankshaft and stores kinetic energy during the power stroke and returns it during the other strokes. The flywheel helps to start the engine and also serves to make the rotation of the crankshaft more or less uniform.. 一个足够重的飞轮固定在曲轴上，在做功冲程时储存动能，在其他冲程中把动能偿还。飞轮 有助于发动机的起动，也使曲轴的旋转大致均匀。 A camshaft driven from the crankshaft by a chain drive or by timing gears operates the intake and exhaust valves through cams, cam followers, push rods, and rocker arms. Valve springs serve to close the valves. 凸轮轴通过凸轮，凸轮从动件，推杆和摇臂控制进气阀和排气阀，而凸轮轴是由与曲轴相连 的链条驱动或正时齿轮驱动的。气阀弹簧用于关闭气阀。 A crankcase serves to hold together the cylinder, piston, and crankshaft, to protect all moving parts and their bearings, and to provide a reservoir for lubricating oil. The lower part of the crankcase is called a bedplate. 曲轴箱把汽缸，活塞和曲轴连成一体，保护所有的运动零件及其轴瓦，并做润滑油箱。曲轴 箱的底部被称为底座。 Fuel is delivered into the combustion space by an injection system consisting of a pump, fuel line, and injector, also called fuel-injection nozzle or spray nozzle. 燃油通过油泵，燃油管和喷油器，也称为燃油喷射喷嘴或喷雾喷嘴组成的喷射系统喷入燃烧 空间。 Cylinder Block 缸体 The cylinder block, on liquid-cooled engines, forms the basic framework of the engine. (In air-cooled engines, the cylinders are often separate parts.)Other parts are attached to the cylinder block or assembled in it. The block is one piece from gray iron or iron alloyed with other metals, such as chromium. some blocks are cast from aluminum. The block contains not only the cylinders, but also the water jackets that surround them. In aluminum blocks, cast-iron cylinder sleeves (also called cylinder liners) are used. These metals have better wearing qualities than aluminum, so they can better withstand the wearing effects of the pistons and rings moving up and down in the cylinders. In some small engines, the cylinder walls are plated with chromium, a very hard metal, to reduce wall wear and lengthen service life. 在水冷发动机中，缸体构成发动机的基本框架。在空冷发动机中，缸体常常是单独的部件。 其他零部件连接到或装配在汽缸体上。缸体是用灰口铁或同其他金属(如铬)的铁合金铸成 的整体。有些缸体是用铝铸造的。缸体不仅包含汽缸，也包含器周围的水套。在一些铝制缸 体上使用铸铁的汽缸衬筒(也称为缸套)。铸铁之类的金属比铝更耐磨，所以，他们更能经 受活塞和活塞环在汽缸上上下移动的磨损。在一些小发动机中，汽缸壁镀铬，一种非常坚硬 的金属，减低缸壁磨损，延长使用寿命。 The casting for the engine block is normally rather intricate, since it contains not only the engine cylinders, but the water jackets that surround them. In addition, passageways are provided to accommodate the valve mechanisms and, on L-head engines, the openings for the intake and exhaust ports. In L-head engines the intake-valve seats are part of the cylinder block, but in many engines the exhaust valve seats are made of special metal rings inserted into recesses in the block. Such exhaust-valve-seat inserts are used because they can better withstand the high temperatures of the burning gases passing through the exhaust ports.The lower part of the cylinder block is the supporting bearings for the engine crankshaft (called the main bearings) so that the crankshaft, in effect, is suspended from the bottom of the block. 发动机缸体的铸件通常相当复杂，因为它不仅包含发动机的汽缸，也包含汽缸周围的水套。 另外，提供气道以安装气阀机构，在L型缸盖的发动机上，提供进气口和排气口的开口。 在L型的发动机上，进气阀座是汽缸体的部分。但是在许多发动机上， 排气阀座是插入缸 体凹槽的专用金属圈。使用这种排气阀座圈是因为这些座圈能更好地经受燃烧气体通过排气 口的高温。缸体的下部垫是发动机曲轴的支撑轴瓦(被成为主轴瓦)，因此，曲轴实际上是 悬在缸体底部上面的。 The upper halves of the crankshaft, or main bearings are assembled directly into half-round sections in the cylinder block; the lower halves of the main bearings are held in place by bearing caps that are attached to the cylinder block by bolts. 曲轴轴承或主轴承的上瓦是直接安装在缸体的半圆体内。主轴承的下瓦是用螺栓固定在缸体 上的轴瓦盖来固定在其相应的位置上。 On most engines, the camshaft is supported in the cylinder block by bushings that fit into machined holes in the block. On some engines, the camshaft is located on the cylinder head. 多数发动机的凸轮轴是由衬套支撑在缸体上。有些发动机的凸轮轴是装在汽缸盖上。 The intake and exhaust manifolds are attached to the side of the cylinder block on L-head, in-line engines.On L-head, V-8, engines, the intake manifold is located between the two banks of cylinders. In this engine, there are exhaust manifolds, one on the outside of each bank. On I-head engines, the manifolds are attached to the cylinder head. L型缸盖，直列式发动机的进气和排气歧管安装在缸体的旁边。L型缸盖，V-8，发动机的 进气歧管位于两排气缸之间。在这种发动机上，每列汽缸的外面都有一个排气管。I型发动 机的排气管连接在缸盖上。 Other parts attached to the block include the water pump (attached at the front),the timing-gear (at the front), the flywheel and clutch housing (at the rear),the ignition distributor, and the fuel pump. The cylinder head mounts on top of the block. 连接到缸体上的其他零件包括水泵(连接在前面)，正时齿轮(前面)，飞轮和离合器壳(在 后面)，火花分配器，和燃油泵。缸盖安装在缸体的上面。 The various parts are attached to the cylinder block with sealing gaskets.Each gasket is placed between the part and the block. Then, tightening the attaching bolts or nuts flattens the gasket to provide a good seal, which prevents leakage(of water, oil, or gas). 各种部件用密封垫连接到缸体上。在部件和缸体之间放上密封垫。然后，拧紧连接的螺栓或 螺帽紧固密封垫，提供更好的密封，防止泄露(水，既有或气)。 Some parts are attached with bolts; others, with nuts and studs. Studs are threaded at both ends; one end is tightened into a threaded hole in the block, the part to be attached is put into place, and a nut is tightened on the other end of the stud to hold the part in position. In some places, retaining or lock washers are put under the nuts or bolt heads. 有的零件用螺栓固定(连接)，有的零件用螺帽和双头螺栓固定(连接)。双头螺栓的两端都 有螺纹，一端紧固在缸体的螺纹孔上。把要连接的零件放进位置，在双头螺栓的另一端用螺 帽把零件固定到位置上。有些地方，在螺帽或螺栓头下面放上弹簧垫或锁紧垫片。 pistons 活塞 The piston with its rings, seals the cylinder and transmits the gas pressure to the connecting rod. It absorbs heat from the gas, and this heat must be carried away if the metal temperature is to be held within safe limits. The constant reversal of the piston travel sets up inertia forces, which increase both with the weight of the piston and with its speed. For this reason designers try to keep piston weight low, particularly in high-speed engines. 活塞，连同活塞环密封汽缸，并把气体的压力传递给连杆。活塞从气体吸收热量。假如要使 金属的温度保持在安全限度以内，就必须散热。活塞行程的不断往复产生惯性力，此力随活 塞的重量和及其速度而增大。为此，设计者设法使活塞造得轻些，特别是高速发动机。 In “uncooled” pistons, the heat absorbed by the piston top travels through the piston side-walls, then through the rings into the cylinder walls and finally to the jacket water surrounding the cylinder. In highly loaded engines, additional means of heat removal are necessary; this is accomplished by a liquid, generally oil. These are termed “cooled” pistons. 在无冷却的活塞中，活塞顶部吸收的热量通过活塞侧壁，再通过活塞环，传入汽缸壁，最后， 传向包在汽缸周围的水套中的水里。在那些高负荷的发动机中，散热的附加措施是必要的。 采用液体通常是油液进行冷却。这种活塞被称为“冷却”活塞。 The top section of a piston is called the crown and the lower section the skirt. . The shape of the top of the crown depends largely on the design of the combustion chamber. The crown section is usually thick, in order to withstand the gas pressure without distorting and to provide a good path for the heat flow from the upper surface of the crown to the rings. When running the piston diameter increases because of the increase in temperature. To take care of the greater expansion in the high-temperature zone, the crown is machined on a slight taper, the diameter being greatest where the crown meets the skirt and becoming less toward the top. 活塞的顶端部分称为活塞顶，下面部分称为活塞裙。顶部的形状主要取决于燃烧室的设计。 为了承受气体压力而不变形，并让热流从活塞顶表面传向活塞环提供良好通道，活塞顶部通 常很厚。在运行中，因为温度升高，活塞直径增大。考虑到高温区热膨胀较大，活塞顶部加 工成低小锥形，即活塞顶部和活塞裙部交接处直径最大，愈向顶部直径愈小。 The crown carries the upper set of rings, which are the “compression”, or “power rings”. In most uncooled pistons, a division plate above the wristpin prevents lubricating oil from splashing against the hot under-surface of the crown. The amount of splashed oil would be insufficient to cool the piston; consequently, the oil would overheat and carbon deposits would form. 活塞顶部装有一组上活塞环，是压缩环或动力环。在多数不冷却活塞中，活塞销上的隔板防 止机油飞溅到活塞顶下部的热表面。飞溅的机油量不足以冷却活塞，因此，机油就因过热而 形成积碳。 The skirt of a trunk piston takes the side-thrust of the connecting rod and prevents the piston from rocking from side to side; it also carries the lower set of rings, which are the “oil-control” rings. Below the upper ring band, where heavy wall thickness is needed to carry the heat flow, the piston skirt becomes much thinner. The running clearance between the skirt and the cylinder wall must be small; therefore, it is important that the thin skirt should stay truly round. For this reason, interior ribs are used to stiffen the skirts of cast pistons. 筒状活塞的裙部承受连杆的侧向推力，并防止活塞从一侧向另一侧摆动，裙部也装有一组下 活塞环， 为机油控制环(油环)。活塞的上环带的下面，必须有足够的壁厚，以防止传热(携 带热流)，而活塞的裙部可薄一些(变得更薄。)活塞的裙部和汽缸壁之间的运行间隙很小， 因此，活塞薄薄的裙部保持真正的圆形很重要。基于这种原因，使用内埋加强筋以增加铸件 活塞裙部的硬度。 The ideal piston material would be light and strong, conduct beat well, expand only slightly when heated, resist wear, and be low in cost. Formerly, all pistons were made of cast iron but today the alloy cast irons, which offer greater heat resistance and better wearing qualities, are widely used. These materials are not perfect as regards weight and heat transfer ability, but nevertheless are quite satisfactory in slow-speed engines, particularly where the piston is effectively cooled by a liquid. 理想的活塞材料应该重量轻，轻度高，导热性能好，热膨胀很小，耐磨，成本低。从前，所 有的活塞都用铸铁制造，但今天，广泛采用合金铸铁，它能提供更好的耐热耐磨性能。这些 材料在重量和传热能力方面不是很理想(完美)，但是，尽管如此，它对低速发动机，特别 是对那些用液体充分(有效地)冷却活塞的发动机是十分合适的。 Composite pistons. Forged steel crowns and cast-iron skirts have been combined in pistons for large engines, to obtain the strength and heat resistance of steel in the upper section, where these properties are important, and the good wearing properties of cast iron in the lower section, where the piston bears against the cylinder. 组合活塞(合成材料活塞) 锻件活塞顶和铸铁活塞裙部组合而成的活塞用于大型发动机中，以便在活塞的上部分获得刚 的强度和耐热这些重要的特性，而在紧靠汽缸的活塞下部获得铸铁的良好耐磨特性。 Many cast-iron pistons are electroplated with metals like cadmium and tin. The purpose is to permit closer clearances(giving a quieter engine), assure proper run-in (that is, the seating of a new piston), eliminate seizing and provide longer life. In some designs, wear is reduced by using inserts of antifriction metal in the piston walls. 许多铸铁活塞采用镉与锡之类的金属镀层。目的是获得更小的间隙(使发动机噪音小)，保 证良好的磨合(也就是，新活塞的磨合)避免卡死并延长使用寿命。在某些设计中，在活塞 壁上采用镶嵌耐磨金属材料以减少磨损。