汽车专业英语(幻灯片)Chapter 3 Engine(2.6).ppt

Gasoline: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 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。汽油泵的入口处承受着高温，就经常出现气阻。,Increasing 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 but 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功率。但随着压缩比的增加，爆震的可能性也会增加。,2)gasoline:,3)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 sample.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0和辛烷值为100，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，依照实验方法，如果匹配的混合物由15%的正庚烷和85%异辛烷组成，那么按照所用的实验方法，实验样本的辛烷值就被认为是85。,Basic words(1):,fuel tank油箱,fuel filter汽油滤清器,fuel pump汽油泵,Carburetor(mix)化油器,air filter空气滤清器,burn,Fuel tank,Fuel line,Fuel pump,Fuel filter,carburetor,air filter,4)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 block.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，汽油泵安装在油箱中，附带有油量传感器和燃油表油量传送装置。,diaphragm spring,Rocker arm,inlet port,outlet port,diaphragm,5)Fuel pump:The rotation of the lobe moves a rocker arm in the pump.Inside the pump,a flexible diaphragm connects to the rocker arm though a diaphragm spring,pull rod and link.,凸圆旋转带动油泵中的摇臂运动。油泵中可变形的泵膜通过膜片回位弹簧和膜片拉杆与摇臂相连。,As the lobe on the camshaft rotates,the diaphragm moves up and down inside the engine.The downward movement of the diaphragm sucks fuel from the tank into the pump.The upward movement of the diaphragm pushes the fuel from the pump to the carburetor.,当凸轮轴上的凸圆转动时，在发动机内的泵膜上下运动泵膜向下运动把油箱中的汽油吸入汽油泵中泵膜向上运动把汽油从油泵中推出到化油器中,Review 2:List the main function of the carburetor.,Meteringcorrect proportions of fuel and airAtomizationspray of fine particles to great airDistributionuniform mixture delivered to manifold,Operating conditions:,1)Cold start2)post-start phase3)warm-up4)Acceleration5)Part load6)Full load7)Idling8)Overrun9)engine-speed limiting10)High altitudes,1)冷启动2)后启动阶段3)暖机4)加速5)部分负荷6)全负荷7)怠速8)超速9)发动机限速10)高海拔,Review 3:List the main circuits of the carburetor.,Idle and Low-Speed CircuitMain Metering CircuitPower-Enrichment CircuitAccelerator(Pump)CircuitChoke Circuit,Basic words():,needle valve 针阀,float chamber 浮子室,float 浮子,venturi 喉管,discharge tube 喷管,throttle 节气门,jet量孔,6)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 factors: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，其上有很多内部通道和部件。,7)carburetor:An automobile carburetor is designed with a venturi chamber.The venturi is simply a narrowed portion 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 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。大气压力作用在化油器中储存汽油的浮子室上。燃油被迫通过伸向喉管低压区的有管。这样燃油从喷管末端喷射到气流中。,8)carburetor:The float chamber is a reservoir for 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 drops.When the float drops,a needle valve is opened.The open needle valve permits the flow of fuel from the fuel pump into the carburetors float chamber.When the chamber is full again,the needle valve is pushed upward and closes the fuel inlet.,浮子室是储存燃油以及向化油器提供燃油的储油室。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。针阀打开使燃油从汽油泵流到化油器的浮子室中当浮子室充满时，针阀被推上去关闭进油口,9)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 jet).This allows a precise amount of fuel to enter the air stream.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。,throttle mechanism:The throttle mechanism controls the flow of the air-fuel mixture.The throttle has several 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，包括节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流量。节气门开启，空气流量增加；节气门关闭，空气流量减少。,11)Gasoline direct injection（GDI）:,Conventional gasoline engines are designed to use an electronic fuel injection system,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 cylinder.,常规的汽油发动机用电控燃油喷射系统代替传统的机械化油作用系统。现在，通过每个进口喷射燃料的多点喷射（MPI）系统是现在最广泛使用的系统之一。尽管MPI系统在燃料反应及燃烧质量上有很大的改善，但是进入汽缸前的空燃气混合仍然限制了它的发展。,EFI=Electronic Fuel Injection 电控燃油喷射SPI=Single Point Injection 单点喷射MPI=Multi Point Injection 多点喷射GDI=Gasoline Direct Injection 汽油缸内直喷,