Although the design of turbochargers may differ the fundamental principles are the same for all models. 尽管各个增压器的设计不同，但是对于所有模式的基本原理都是相同的。It is the principles which will be considered here, together with the arrangements as they relate to medium speed engines. 下面将讨论增压器的工作原理，以及中速机增压器的安排布置。
A turbine consists of a single row of rotating blades mounted on a disc. 一个涡轮由一圈固定在涡轮盘上的旋转叶片所组成。Gas is directed onto the moving blades by an annular arrangement of nozzle blades. 通过喷嘴叶片的环形布置，废气直接喷到旋转叶片上。Moving blades fit axially into the disc using inverted fir-tree roots, or similar.旋转的叶片以反杉树根形或相似形状，轴向安装在涡轮盘上。 Blade design, both moving and fixed, is critical to performance and varies according to the type of turbine system. 无论是转动叶片还是固定叶片都要严格根据涡轮系统的类型来设计或做适当改变。Although the pulse system of turbocharging has been very popular for medium speed engines, and remains so, constant pressure systems are often employed where high powered engines are used for propulsion purposes. 尽管脉冲式涡轮增压器已经普遍用于中速柴油机，但即使如此，定压式增压系统也经常用在一些用于推进目的的大功率柴油机上。V type engines normally have separate turbochargers for each bank of cylinders.V型柴油机每一列汽缸单独使用一个增压器。 Turbocharger, Pulse System 脉冲增压系统
The pulse system makes use of the high pressure kinetic and thermal energy in the exhaust gas when the exhaust commences, and the timing of the exhaust is critical to turbocharger performance. 脉冲增压系统利用排气开始时废气中的高压动能和热能，排气开始的时间对增压器的性能有较大影响。Early opening of the exhaust was often employed as a means of obtaining sufficient exhaust gas energy. 经常利用排气阀提前开启的方法来获得足够的排气能量。This system has proved popular as it enables the turbocharger to supply sufficient air for good combustion at all loads. 这种系统很受欢迎，它在柴油机各种负荷下，都能提供足够的空气，保证燃烧良好。The pulse system employs relatively small bore pipes connecting the cylinders to the turbocharger, to avoid a loss of gas energy in the exhaust piping. 脉冲系统使用相对较细的管子连接汽缸和增压器，避免排气管中废气能量的损失。Exhaust gas flows from each cylinder for about 120°; to avoid interference between pulses, groups of three cylinders are generally connected to particular sections of turbocharger nozzle. 每个汽缸废气的排放大约持续120°曲轴转角，为了避免脉冲之间相互干扰，每三个汽缸分成一组连接到增压器喷嘴的一个特定区域。This implies a multiple inlet arrangement for the turbine. 这就意味着一台增压器有多个进气口。A six-cylinder engine would require two turbocharger entries and a nine-cylinder engine, three entries, or two turbochargers. 一台六缸柴油机将有两个增压器进气口，一台九缸柴油机将会有三个进气口或有两台增压器。Pulse systems are ideally suited to engines where frequent and large changes in load take place, such as those used for electrical generation, but their exhaust gas piping systems can become complex particularly for engines with a large number of cylinders. 脉冲式增压系统安装到负荷大小频繁变化的柴油机上比较理想，比如用在发电机上。但是它们的排气系统可能变得复杂，尤其是汽缸数目很多的柴油机。Turbine and nozzle blades must be designed to cope efficiently with the wide range of gas pressures which exist over a cycle, which implies relatively thick blade sections with well rounded entry noses涡轮和喷嘴的叶片必须设计能够有效地适应每个排气过程中排气压力的巨大变化，这就要求叶片的截面相对较厚并且要有较好的圆形的进气口。
Turbocharger, Constant Pressure System定压增压系统
The constant pressure turbocharging system has all cylinders supplying exhaust gas to a large
volume manifold, which then directs the gas to the turbocharger nozzle ring. 定压增压系统把各个缸的废气都排到一个大的废气总管中，然后直接把废气供到喷嘴环。Pulse or kinetic energy is not required, so exhaust can commence later in the piston stroke achieving a slight increase in cylinder power.不需要利用脉冲能和动能，所以活塞行程中排气可以稍晚一点开始，这样可以使每个汽缸的功率稍微有些提高。 Exhaust gas in the manifold is maintained at a relatively steady pressure, at any particular engine load, and so the turbine and nozzle blades can be designed to suit steady conditions. 在任何特殊的柴油机负荷下，排气总管中的废气维持在一个相对稳定的压力，所以涡轮和喷嘴的叶片可以设计成适合稳定工况的形状。Blade sections tend to be thinner and have sharper noses than for pulse blading. 相对于脉冲式系统，定压系统叶片的截面倾向于较薄且进气口比较尖一些。Constant pressure systems do not react as quickly to sudden load changes, but they are more efficient and have a relatively simple exhaust pipe arrangement.定压系统对于突变负荷的反应不快，但是它们效率高且排气管布置相对简单。 Turbocharger Compressor 涡轮增压器的压气机
The turbocharger turbine drives a rotary compressor which consists of an impeller and volute casing. 涡轮增压器的涡轮驱动一个由叶轮和蜗壳组成的压气机。Air enters the impeller at its centre or 'eye'; rotation of the impeller imparts a high velocity to the air which then moves outwards into the stationary diffuser and volute casing. 空气从中心的“眼”进入压气机叶轮，叶轮的旋转传递给空气一个很高的速度，然后空气流到外部一个静止的扩压器和蜗壳中。This casing has a steadily increasing cross sectional area and is like an inverted nozzle wrapped around the impeller. 蜗壳有一个不断增加的横截面积，像一个反向的喷嘴缠绕在叶轮的外部。The volute converts velocity energy into pressure energy, just as a nozzle converts pressure energy into velocity energy, and the air leaves the compressor casing at a relatively low velocity but at increased pressure. 蜗壳把速度能转化为压力能，就像一个喷嘴把压力能转化为速度能，空气以一个相对较低的速度但是较高的压力离开压气机壳体。The impeller is basically a disc with a number of radial vanes which reduce in depth from the eye to the periphery. 叶轮是一个带有一些径向叶片的圆盘，叶片的高度从中心向圆盘的边缘递减。The rotor assembly, comprising turbine, shaft and impeller, is a balanced set but the impeller can be removed from the rotor. 转子组件是由涡轮、轴和叶轮组成的一个平衡设备，叶轮可以从转子上拆卸下来。The impeller fits onto the rotor using a splined connection. 叶轮通过花键连接到转子上。In order to preserve balance the impeller is made so it will only fit onto the rotor in a particular position, usually by having one of the splines larger than the rest. 为了保证平衡，叶轮制作成只能安装在转子的特定位置上，通常是花键中的一个键比其它的大一些。A suction filter is provided before the eye of the impeller to remove dust and oil particles which could build up on the impeller, volute and cooler, reducing performance. 叶轮中心吸入孔之前安装一个吸入滤器，用来除去灰尘和油颗粒，灰尘和油颗粒会在叶轮、蜗壳和空气冷却器上聚集，降低增压器的性能。The filter acts as a silencer but insulating felt on the suction manifold also reduces noise.滤器可以作为一个消音器，但是吸气总管内部的绝缘毛毡也可以降低噪音。 Intercooling 中间冷却器
Air cooling is achieved by means of one or more intercoolers located between the impeller outlet and the air manifold, which runs the length of the engine. 空气冷却是通过一个或多个位于叶轮出口和空气主管之间的中冷器来实现，它和主机的长度一样。These coolers are comprised of a number of finned tubes through which cooling water flows, the air flowing over the fins. 冷却器是由一些带有翅片的管子组成，冷却水在管内流动，空气流过翅片。The use of fins increases the effective heat transfer surface area and allows a reduction in the physical
external dimensions of the cooler. 翅片的使用增加了有效传热面积，允许冷却器物理外形尺寸降低。Provision must be made for thermal expansion of the tubes, generally by employing U-tubes which have in-built compensation for thermal expansion. 必须提供管路的热膨胀空间，运用内置U形管补偿热膨胀。Water inlet and outlet headers are then provided on the same side of the cooler making for more accessible pipe connections. 冷却水的进出口端盖设计在冷却器的同一侧，使管路连接更容易。In some cases water separators are fitted in order to remove any water?drop which might form during cooling of the combustion air.一些情况下会安装除水器来除掉在空气冷却过程中产生的水滴。 Water entering the cylinder can remove the oil film from the cylinder liner but this is more of a problem with two stroke cycle engines, where the air enters through ports in the lower part of the liner rather than valves in the cylinder head.水进入汽缸会破坏汽缸套上的油膜，这个问题在二冲程柴油机中更为严重，二冲程机中，空气不是从汽缸盖上的进气阀进入汽缸，而是从汽缸下部的进气口进入汽缸。 Turbochargers Matching to Engine 涡轮增压器与柴油机的匹配
Highly rated high powered engines used for propulsion must be capable of meeting a wide range of loads. 额定功率高的柴油机用来作为推进主机必须能够满足负荷的大范围变化。However, cylinder conditions must be kept within certain limits in terms of maximum pressure and temperature. 然而，就最大压力和最高温度而言，汽缸的工作条件也必须保持在一定的限度内。In many cases turbochargers are matched to the engine so that they produce nominal full output at about 85 per cent of engine power. 在很多情况下，涡轮增压器与主机相匹配，发出名义全负荷输出，该负荷为柴油机功率的85%。At higher loads the engine produces too much exhaust gas energy for the turbine. 在高负荷下，柴油机为涡轮机提供了过多的废气能量。A waste gate is fitted in the exhaust manifold to the turbine so that some of the exhaust gas can be directed to the uptake rather than passing through the turbine. 在通往涡轮机的废气总管上安装多余废气旁通挡板，这样一些废气可以直接通往烟囱而不经过涡轮机。Similarly an air waste gate may be fitted to the air supply manifold to release excess combustion air pressure. 类似也可以在空气总管上安装多余空气挡板，用来释放过高的空气压力。Turbochargers fitted to engines have to deal with wide load ranges and they cannot be efficient at all loads. 柴油机的增压器必须能工作于各种负荷条件下，但是它们不能在全负荷条件下都有较高的效率。At high loads too much combustion air may be supplied, which can have an adverse effect on the engine. 在高负荷时，可能会向柴油机提供过多的空气，但是却会对柴油造成不利的影响。The use of exhaust gas and air waste gates enables the turbocharger(s) to provide high charge air pressures at low powers. 废气和空气旁通挡板的使用能够使增压器以较低的功率向柴油机提供较高的进气压力。This improves fuel consumption, produces a reduction in thermal loadings and allows for better response to load changes.这改善了燃油的燃烧，降低了热负荷，提高了负荷变化的响应。 Engines running at variable speed may be fitted with a charge air bypass which effectively puts some of the charge air into the exhaust gas trunk under certain operating conditions.变速工作的柴油机可能安装空气旁通装置，该装置在一定工作条件下有效地把一些空气通入排气总管。The use of the charge air bypass permits the matching of valve overlap and turbocharger for best specific fuel oil consumption (SFOC) when the by-pass is closed and avoids the risk of turbocharger surging at lower powers when the bypass is open. 使用新鲜空气旁通允许气阀重叠和涡轮增压相匹配，以保证当旁通关闭时，有最佳燃油消耗率；旁通阀打开时，防止增压器在低负荷喘振。Depending on the engine design and operating conditions a charge air waste gate, exhaust waste gate and charge air bypass may be fitted. All devices are operated automatically by the engine's control system.进气旁通挡板、废气旁通挡板和新鲜空气旁通门依
照设计和使用条件有可能安装，所有这些装置都是由柴油机控制系统来自动操作的。
LESSON 10
ENGINE GOVERNOR
柴油机调速器
A governor maintains the engine speed at the desired value no matter how much load is applied. 不管所用的负载如何变化，调速器能够保持柴油机的转速在一个期望值上。It achieves this by adjustment of the fuel pump racks. 可以通过燃油泵的齿条调整来实现。Any change in load will produce a change in engine speed, which will cause the governor to initiate a fuel change. 负载的任何变化将会产生一个柴油机转速的变化，从而引起调速器开始燃油调整。The governor is said to be speed sensing as a speed change has to take place before the governor can react to adjust the fuel setting. 调速器被认为是速度识别，因为速度变化发生在调速器对燃油设定做出反应之前。The simple mechanical governor employs rotating weights which move outward as the speed increases and inward as the speed reduces; this movement, acting through a system of linkages, can be used to regulate the fuel rack. 这种简单的机械式调速器采用飞重，当速度增加时，飞重向外移动，而当速度减少时，飞重向内移动；这种运动通过联动装置起作用，可以用于控制燃油齿条。Rather than having the rotating weights directly move the fuel linkage, hydraulic governors employ a servo system so the rotating weights only need to move a pilot valve in the hydraulic line.液压调速器采用伺服系统，所以飞重只需要移动液压管路的控制阀，而不是让飞重直接移动燃油联动装置。 This makes the governor more responsive. Governors of this type require a speed change to take place in order that they may initiate fuel rack adjustment. This is known as speed droop and there is a definite speed for each load therefore the governor cannot control to a single speed. 这样让调速器反应更加灵敏。为了实现对燃油齿条的调整，这种类型的调速器需要产生一个速度变化，这就是速度降。每个负载有一个确定的速度，因此调速器不能控制单一的速度。A modification to the governor hydraulic system introduces a facility known as compensation which allows for further fuel adjustment after the main adjustment has taken place due to speed droop. 调速器液压系统的改变是采用一个补偿装置，可以让由于速度降引起的主要调整发生之后，允许进一步的燃油调整。Compensation restores the speed to its original desired value so the engine can operate at the same speed under all loads. Such a governor is said to be isochronous as the engine operates at a single speed. However, the governor is still speed sensing and so is not ideal for all applications.补偿让速度恢复到原来的期望值，这样柴油机可以在所有负载下工作于同一速度。因为柴油机在单速下运转，所以这种调速器被认为是同步的。但是调速器始终进行速度监测，所以不是对于所有的应用都是理想的。
Speed Sensing Governor速度感应调速器
Where the engine drives an alternator any speed change results in a change in supply frequency. Large changes in electrical supply frequency can have an adverse effect on sensitive electronic equipment connected to that supply. 柴油机驱动的交流发电机的任何速度变化将导致供电频率的变化。供电频率大的变化对连接到电网上的敏感电子设备有一个有害的影响。Where electrical generation is involved it is possible to monitor the electrical load and use this as a means for actuating the governor response, rather than simply taking rotational speed as the
control signal.在需要电力供给的地方就可以监控电力负载，使之作为促使调速器响应的一个手段，而不是简单的把旋转速度作为控制信号。 Such governors are known as load sensing. It is extremely difficult to make a mechanical governor load sensing, even with a hydraulic system, but an electronic governor can take account of the electrical load applied to the engine and so can be considered 'speed sensing'.这种调速器被称为负载感应。机械调速器的负载感应是极为困难的，即使液压系统也是如此，但是电子调速器能够考虑应用到柴油机的电力负载，所以被认为是“速度感应”。
Electronic Governor电子调速器
Electronic governors essentially comprise two parts, the digital control unit and the hydraulic actuator, which are interlinked but it is useful to consider them separately.电子调速器有必不可少的两部分组成，电子控制单元和液压执行器，它们之间互相连接但是让两者分开是非常有帮助的。
Electronic Governor Controller电子调速器控制器
The digital control may be considered as a 'black box' in which signals are processed to produce a control signal which is sent to the actuator. 电子控制可以被认为是一个“黑箱”，在“黑箱”里信号经过处理产生一个控制信号被送到执行器。The controller may be programmed in order to set points and parameters. The controller is a sensitive piece of electronic equipment and should not be mounted on the engine or in areas where it will be exposed to vibration, humidity or high temperatures. 为了设定控制点和控制参数，可以对控制器编程。控制器是一个敏感的电子设备，不能安装在柴油机上或者暴露于振动，潮湿或者高温的区域中。It should be ventilated in order to keep it cool and should be shielded from high-voltage or high-current devices which will cause electromagnetic interference. 为了保证控制器冷却必须保持通风，并要屏蔽将会引起电磁干扰的高压或大电流装置。Similar restrictions apply to the location of signal cables. Speed signals are taken from two speed transducers, one on each side of the flexible coupling which attaches the engine to the load. 同样的限制适用于电缆的安放位置。速度信号通过两个速度传感器采集，安装在连接柴油机和负载之间的弹性联轴器两侧。Failure of one transducer produces a minor alarm but allows continued operation with an electronic over speed value may be programmed into the controller in which case detection of over speed will cause the engine to be shut off. 一个速度传感器失效会产生一个小的报警但是允许电子设备的继续运行。超速数值可以编程进入控制器内，一旦检测到超速信号就会引起柴油机停车。If the load is provided by an electrical machine the output from that machine provides a signal for load sharing. Should this transducer fail the load on the engine will be determined by the position of the governor actuator output. 假如负载由电器设备驱动，那么电器设备会提供一个输出信号用来负载分配。万一传感器失效，柴油机上的负载将由液压执行器额输出状态决定。The controller can also receive signals from other transducers including the engine's air inlet pressure, which allows the fuel to be limited when starting. After processing input signals in accordance with programmed requirements an output signal will be sent to the governor actuator.控制器也能从其它的传感器接受信号，包括柴油机的进气压力，当起动的时候来限制燃油的供油量。在对输入信号按照程序要求处理之后，输出信号被送到调速器执行器。 Electronic Governor Actuator电子调速器执行器
The actuator is a hydraulic device which moves the fuel linkage in response to a signal from the digital controller. The operating mechanism is contained within an oil filled casing. 执行器是一个液压装置，可以驱动燃油连杆，对来自于数字控制器的信号做出反应。这个工作机构放置在一个充满油液的箱子中。Oil pressure is provided by a servomotor pump driven by a shaft