Chapter3Engine(2.6)

1、SEASpecial English for AutomobileChapter 2 internal combustion engineReview 1: Whats the meaning of the air/fuel ratio (A/F)? The proportion of air to fuel.*A/F is stated in term of weight, different fuel has different ratio.SEASpecial English for AutomobileChapter 2 internal combustion engine1)Gaso

2、line : Gasoline must vaporize easily. This characteristic, called volatility, is important. However, it must not vaporize too easily, or it will turn to vapor inside the fuel tank or fuel lines. Inside the fuel line, fuel vapor may block the flow of liquid gasoline. This is called vapor lock. Vapor

3、lock is common in fuel lines where the inlet side of the pump is exposed to high temperatures.汽油应易于蒸发，这个重要的特性称为挥发性。但是汽油也不汽油应易于蒸发，这个重要的特性称为挥发性。但是汽油也不能挥发得过快，不然它会在油箱或油管里转变为蒸气。在油管能挥发得过快，不然它会在油箱或油管里转变为蒸气。在油管中汽油蒸气会阻碍液态汽油的流动，这称为气阻。汽油泵的入中汽油蒸气会阻碍液态汽油的流动，这称为气阻。汽油泵的入口处承受着高温，就经常出现气阻。口处承受着高温，就经常出现气阻。SEASpecial E

4、nglish for AutomobileChapter 2 internal combustion engineIncreasing the pressure of the fuel mixture in the combustion chamber before ignition helps to increase the power of an engine. This is done by compressing the fuel mixture to a smaller volume. Higher compression ratios not only boost power bu

5、t also give more efficient power. But as the compression ratio goes up, knocking tendency increases. 在点火前增加燃烧室内可燃混合气的压力有助于提高发动机的在点火前增加燃烧室内可燃混合气的压力有助于提高发动机的功率，这是通过把可燃混合气压缩到一个极小的体积来实现的功率，这是通过把可燃混合气压缩到一个极小的体积来实现的。高的压缩比不仅增加发动机的功率，而且会带来更多的有效。高的压缩比不仅增加发动机的功率，而且会带来更多的有效功率。但随着压缩比的增加，爆震的可能性也会增加。功率。但随着压缩比的增加，

6、爆震的可能性也会增加。2) gasoline:SEASpecial English for AutomobileChapter 2 internal combustion engine3) gasoline: Two primary standard reference fuels, normal heptane and iso-octane arbitrarily assigned 0 and 100 octane number, respectively, are then blended to produce the same knock intensity as the test sa

7、mple. The percentage of isooctane in blend is considered the octane number of the test sample. Thus, if the matching reference blend is made up of 15% n-heptane and 85% isooctane, the test sample is rated 85 motor or research octane number, according to the test method used.两种基准参考燃料正庚烷和异辛烷分别被定义成辛烷值为

8、两种基准参考燃料正庚烷和异辛烷分别被定义成辛烷值为0 0和辛烷和辛烷值为值为100100，将它们混合产生与实验样本相等敲缸强度的爆震。混合，将它们混合产生与实验样本相等敲缸强度的爆震。混合物中异辛烷的百分比就认为是实验样本的辛烷值。这样，依照实物中异辛烷的百分比就认为是实验样本的辛烷值。这样，依照实验方法，如果匹配的混合物由验方法，如果匹配的混合物由15%15%的正庚烷和的正庚烷和85%85%异辛烷组成，那异辛烷组成，那么按照所用的实验方法，对比实验样本的辛烷值就是么按照所用的实验方法，对比实验样本的辛烷值就是8585。SEASpecial English for AutomobileChap

9、ter 2 internal combustion engineBasic words(1):fuel tankfuel tank油箱油箱fuel filterfuel filter汽油滤清器汽油滤清器fuel pumpfuel pump汽油泵汽油泵Carburetor (mix)Carburetor (mix)化油器化油器air air filterfilter空气空气滤清器滤清器burnSEASpecial English for AutomobileChapter 2 internal combustion engineFuel tankFuel linefuel pumpFuel fi

10、ltercarburetorair filterSEASpecial English for AutomobileChapter 2 internal combustion engine4) Fuel pump: Most cars today have a mechanical fuel pump. This pumps fuel out of the tank and through the fuel lines to the carburetor or injection system. In most cars, the pump is mounted on the engine bl

11、ock. Some cars have an electric fuel pump. This pump mounts in the fuel tank with the fuel pickup and the fuel-gauge-sending unit. 当前大多数汽车采用机械汽油泵，汽油泵从油箱抽出当前大多数汽车采用机械汽油泵，汽油泵从油箱抽出汽油，通过油管送到化油器或喷射系统。大部分汽车汽油，通过油管送到化油器或喷射系统。大部分汽车的汽油泵安装在缸体上。一些汽车采用电动汽油泵，的汽油泵安装在缸体上。一些汽车采用电动汽油泵，汽油泵安装在油箱上，附带有油量传感器和燃油表油汽油泵安装在油箱

12、上，附带有油量传感器和燃油表油量传送装置。量传送装置。SEASpecial English for AutomobileChapter 2 internal combustion enginediaphragm springdiaphragm springRocker armRocker arminlet portinlet portoutlet portoutlet portdiaphragmdiaphragm5) Fuel pump: The rotation of the lobe moves a rocker arm in the pump. Inside the pump, a fl

13、exible diaphragm connects to the rocker arm though a diaphragm spring, pull rod and link.凸圆旋转带动油泵凸圆旋转带动油泵中的摇臂运动。油中的摇臂运动。油泵中可变形的泵膜泵中可变形的泵膜通过膜片回位弹簧通过膜片回位弹簧和膜片拉杆机构与和膜片拉杆机构与摇臂相连。摇臂相连。SEASpecial English for AutomobileChapter 2 internal combustion engineSEASpecial English for AutomobileChapter 2 internal

14、combustion engineBasic words(2):Excess-air factor :Complete burnRich mixture Lean mixture浓混合气浓混合气 稀混合气稀混合气theoretical requirement(14.7:1) =air mass supplied/ theoretical requirement过量空气系数过量空气系数SEASpecial English for AutomobileChapter 2 internal combustion engineOperating conditions:1)Cold star2)post

15、-start phase3)warm-up4)Acceleration5)Part load6)Full load7)Idling8)Overrun9)engine-speed limiting10)High altitudes1)冷启动冷启动2)后启动阶段后启动阶段3)暖机暖机4)加速加速5)部分负荷部分负荷6)全负荷全负荷7)怠速怠速8)超速超速9)发动机限速发动机限速10)高海拔高海拔SEASpecial English for AutomobileChapter 2 internal combustion engineReview 2: List the main function o

16、f the carburetor. Meteringcorrect proportions of fuel and airAtomizationspray of fine particles to great airDistributionuniform mixture delivered to manifoldSEASpecial English for AutomobileChapter 2 internal combustion engineReview 3: List the main circuits of the carburetor. Idle and Low-Speed Cir

17、cuitMain Metering CircuitPower-Enrichment CircuitAccelerator (Pump) CircuitChoke CircuitSEASpecial English for AutomobileChapter 2 internal combustion engineSEASpecial English for AutomobileChapter 2 internal combustion engineBasic words():needle valve 针针阀阀float chamber 浮子室浮子室float 浮子浮子 venturi 喉管喉管

18、discharge tube 喷管喷管throttle 节气门节气门jet量量孔孔idling valve idling valve 怠速阀怠速阀nozzlenozzle 喷嘴喷嘴advance angleadvance angle提前角提前角dwell angledwell angle 持续角持续角PetroleumPetroleum 石油石油SEASpecial English for AutomobileChapter 2 internal combustion engineSEASpecial English for AutomobileChapter 2 internal combu

19、stion engine6) carburetor: A carburetor delivers fuel in proportion to the amount of air flowing through it. As you press on the accelerator pedal, the throttle valve opens wider to draw more air through the carburetor. The carburetor provides richer or leaner mixtures, depending on a number of fact

20、ors: engine speed, load, temperature, and throttle position. To meet complicated demands, a carburetor is a highly intricate device, with many internal passages and parts. 化油器输送的燃油与流经化油器的空气量成一定比例。踩下加速化油器输送的燃油与流经化油器的空气量成一定比例。踩下加速踏板，节气门开度变大，化油器吸入的空气增加。化油器可提供踏板，节气门开度变大，化油器吸入的空气增加。化油器可提供较浓或较稀的混合气，这取决于发动

21、机转速、负荷、温度和油门较浓或较稀的混合气，这取决于发动机转速、负荷、温度和油门开度等因素。为满足复杂的要求，化油器的结构也很复杂，其上开度等因素。为满足复杂的要求，化油器的结构也很复杂，其上有很多内部通道和部件。有很多内部通道和部件。SEASpecial English for AutomobileChapter 2 internal combustion engine7) carburetor: An automobile carburetor is designed with a venturi chamber. The venturi is simply a narrowed port

22、ion in the air passage. Air moving through the throat of the carburetor speeds up as it travels through this narrowed passageway. The increased air speed through the venturi creates a low-pressure area at the opening of the fuel nozzle. Atmospheric pressure pushes down on a fuel reservoir within the

23、 carburetor known as the float chamber. Fuel is forced through a tube that extends into the low-pressure area of the venturi. Thus, fuel sprays through the end of the tube into the air stream. 化油器设计成带有喉管的形式，喉管是空气通道中一化油器设计成带有喉管的形式，喉管是空气通道中一段狭窄的部分。空气流过化油器的喉管时速度增加，段狭窄的部分。空气流过化油器的喉管时速度增加，在喷嘴的开口处形成低压区。大气

24、压力作用在储存汽在喷嘴的开口处形成低压区。大气压力作用在储存汽油的浮子室上。燃油便被压入伸向喉管低压区的喷管油的浮子室上。燃油便被压入伸向喉管低压区的喷管里。这样燃油从喷管末端喷射到气流中。里。这样燃油从喷管末端喷射到气流中。SEASpecial English for AutomobileChapter 2 internal combustion engineSEASpecial English for AutomobileChapter 2 internal combustion engine8) carburetor: The float chamber is a reservoir f

25、or storing and supplying fuel to the carburetor. As the engine uses fuel, the float chamber replenishes it automatically. The float chamber works on the same basic principle as the holding tank in a flushing toilet. A float rests on top of the fuel in the reservoir. As fuel is used, the float level

26、drops. When the float drops, a needle valve is opened. 浮子室用于储存燃油以及向化油器提供燃油。发动机消浮子室用于储存燃油以及向化油器提供燃油。发动机消耗燃油时，浮子室会自动进行补充。浮子室和抽水马桶耗燃油时，浮子室会自动进行补充。浮子室和抽水马桶储水箱的工作原理是相同的。浮子停留在浮子室的油面储水箱的工作原理是相同的。浮子停留在浮子室的油面上。消耗燃油时，浮子下落。浮子下落时，针阀打开。上。消耗燃油时，浮子下落。浮子下落时，针阀打开。SEASpecial English for AutomobileChapter 2 internal c

27、ombustion engine9) carburetor: The pressure differential between the float chamber and the venturi causes fuel to flow. However, to maintain the proper air-fuel ratio, the carburetor must provide just the right amount of fuel. To do so, the main discharge tube has a small hole (called a jet or main

28、jet). This allows a precise amount of fuel to enter the airstream. In most cases, this small hole is in the float chamber at the end of the main discharge tube. There, its small size limits fuel flow.浮子室和喉管之间的压力差引起燃油的流动。然而，为维持合适浮子室和喉管之间的压力差引起燃油的流动。然而，为维持合适的空燃比，化油器必须提供适量的燃油。为此，在主喷管上有一的空燃比，化油器必须提供适量的燃

29、油。为此，在主喷管上有一个小孔，称作量孔或主量孔，它使得精确数量的燃油进入到气流个小孔，称作量孔或主量孔，它使得精确数量的燃油进入到气流中。量孔一般在主喷管末端的浮子室里，控制着燃油的流量。中。量孔一般在主喷管末端的浮子室里，控制着燃油的流量。SEASpecial English for AutomobileChapter 2 internal combustion engine10)throttle mechanism: The throttle mechanism controls the flow of the air-fuel mixture. The throttle has sev

30、eral parts, including the throttle shaft and the throttle plate. By opening and closing, the throttle plate controls the flow of the air-fuel mixture into the engine. More air flows in as the plate opens; less air flows in as the plate closes. 节气门机构控制着可燃混合气的流量，包节气门机构控制着可燃混合气的流量，包括节气门轴和节气门等部件。节气门的开括节

31、气门轴和节气门等部件。节气门的开启和关闭控制着可燃混合气进入发动机的启和关闭控制着可燃混合气进入发动机的流量。节气门开启，空气流量增加；节气流量。节气门开启，空气流量增加；节气门关闭，空气流量减少。门关闭，空气流量减少。SEASpecial English for AutomobileChapter 2 internal combustion engine11) Gasoline direct injection（GDI）: Conventional gasoline engines are designed to use an electronic fuel injection system

32、, replacing the traditional mechanical carburetion system. Multi-point injection (MPI), where the fuel is injected through each intake port, is currently one of the most wider used systems. Although MPI provides a drastic improvement in response and combustion quality, it is still limited due to fuel and air mixing prior to entering cyli