汽车专业英语(幻灯片)Chapter 3 Engine(2.7).ppt

Differences between diesel and gasoline engines:Diesel engine gets this name from the pioneer work done by Dr Rudolf Diesel.The diesel is used for the majority of heavy vehicles and the excellent fuel economy makes it an attractive alternative to the petrol engine for light commercial vehicles,delivery vans and taxis.,柴油发动机的名称来源于Rudolf Diesel博士所完成的开拓性工作。大多数重型车辆使用柴油，优良的燃油经济性使得柴油机成为最有吸引力的替代品,来代替轻型商用车、厢式货车和出租车上汽油机。,Gasoline,kerosene and diesel oil are all produce from natural petroleum(crude oil),and are distinguished mainly by their volatility.Gasoline is quite volatile,that is,it evaporates or vaporizes at a low temperature.Kerosene needs more heat to make it vaporize,while diesel oil requires still more heat.Both types of engines are internal-combustion engines,that is,they burn the fuel inside their cylinders.,汽油、煤油和柴油全都是从天然石油（原油）中提取出来的，通过挥发性可以把他们区分开。汽油易挥发，也就是，它在低温下蒸发或变成蒸汽。煤油需要较多热量才能挥发，而柴油需要更多热量。这两种发动机都是内燃机，也就是，它们在汽缸内燃烧。,The diesel engine has no throttle plate or similar device to restrict airflow into the engine.Engine speed is controlled only by the amount of fuel put into the cylinders.For this reason,a diesel engine is an unthrottled engine.A gasoline engine has high vacuum when the throttle is closed,and low or no vacuum when the throttle is open.A diesel engine,because it has no throttle,has no intake manifold vacuum.,柴油机没有节气门或类似装置控制进入发动机的气流。发动机速度仅由进入汽缸中的燃油量控制。因此，柴油机是无节气门发动机。当关闭节气门时汽油机真空度升高，打开节气门时真空度降低或没有真空。由于柴油发动机没有节气门，因而没有进气管真空度。,The fuel injection system is the most important part of the diesel engine.Diesel injection must control the quantity of the fuel injected and determine when it is to be injected.The timing of the fuel injection is important,as is the spark timing of a gasoline engine.,燃油喷射系统是柴油机的最重要的部分。柴油喷射必须控制燃油喷射量和决定喷射时间。燃油喷射时间象汽油机点火时间一样重要。,Review 1:List the differences between Diesel and Gasoline engine?,Actual efficiency eff up to 45%,Actual efficiency eff up to 30%,Maximum combustion pressure 6 8 MPa,Maximum combustion pressure 35 MPa,Compression ratio 14 24,Compression ratio 8 11,always greater than 1,（excess-air factor)from 0.7 to 1.3,Engine speed 1500 to 5000 r/min,Engine speed 4000 to 10000 r/min,Irregular mixture in the combustion chamber,Regular mixture in the combustion chamber,Auto-ignition,Externally supplied ignition,Interior mixture formation,Exterior mixture formation,Diesel engine,Gasoline engine,combustion temperature approx.2500 C,Highest combustion temperature approx.2000 C,Basic words:,Feed pump:,Review 2:List the three precise couples of in-line pump diesel engine?,Plunger and barrel couple(plunger and pump barrel),Delivery valve couple(delivery valve and delivery valve seat),Needle valve couple(needle valve and needle valve body),in-line pump fuel-injector system:The fuel-injection system on a diesel engine must do a number of important things.First,it must meter the correct amount of fuel to run the engine at the speed and load demanded by the driver.Then it must deliver the metered fuel equally to all cylinders,at exactly the right time.Next,it must inject the fuel at the correct rate and spray pattern for the best burning in the combustion chamber.,柴油机的燃油喷射系统要完成许多重要的工作。首先，它必须定量供应精确数量的燃油，使发动机在驾驶员所要求的转速和负荷条件下运行。然后，它必须在合适的时刻把定量供应的燃油平均分配给每一个气缸。为使燃烧室里燃烧效果最好，它又必须以合适的速率和喷射方式喷油。,Suction Compression Injection Spill,Operation of In-line Fuel Pump,Operation of the pumping element:,With the injector pump on the low part(base circle)of the camshaft,the inlet and spill ports are open.This allows fuel to flow at 268 kPa into the venturi on top of the plunger.As the camshaft turns,the lobe moves the plunger upward.This raised the fuel pressure,forcing fuel through the delivery valve and on through the lines.The lobe continues to move the plunger upward to a point where the spiral groove in the plunger uncovers the spill port in the venturi.At this point,fuel above the plunger drains through the spill port.This is the end of injection.,当喷油泵处于凸轮轴基圆时，进油孔和回油孔都打开，柴油以268KPa的压力流入柱塞上方的柱塞腔。凸轮轴旋转时，凸圆使柱塞向上移动，油压增加，柴油从出油阀流出送入高压油管。凸圆继续推动柱塞向上移动，直到柱塞运动到螺旋槽打开柱塞腔上的回油孔时的位置，此时，柱塞上方的柴油从回油孔流出，喷油过程结束。,With the injector pump on the low part(base circle)of the camshaft,the inlet and spill ports are open.This allows fuel to flow at 268 kPa into the venturi on top of the plunger.As the camshaft turns,the lobe moves the plunger upward.This raised the fuel pressure,forcing fuel through the delivery valve and on through the lines.The lobe continues to move the plunger upward to a point where the spiral groove in the plunger uncovers the spill port in the venturi.At this point,fuel above the plunger drains through the spill port.This is the end of injection.,Review 3:List the main function of the governor in a diesel engine.,Limit the maximum speedKeep the idling speed,Variable-speed governor 全程式调速器,minimum-maximum-speed governor两极式调速器,Mechanical governor:,At equilibrium,the control rod assumes a position for a supply of fuel which corresponds to engine power at that operating point.If engine speed drops as a result of increased load,for example,the centrifugal force is also reduced and the governor springs move the flyweights,and thus the control rod,in the direction of increased fuel delivery until equilibrium is again established.(p52),平衡时，控制杆的供油位置由该工况点发动机功率决定例如，如果由于负载增加，发动机速度下降，飞块的离心力会随之下降此时，调速器弹簧压动飞块，带动控制杆向加油方向运动直至平衡从新建立,Fig.2-29 Diagram of RQ speed governor1-shut stop 2-accelerator lever 3-full-load stop 4-guide block 5-slide pivot 6-governor lever 7-rack 8-plunger 9-spring block to limit fuel 10-slide 11-guide pin 12-sliding bolt 13-bell crank 14-governor hub 15-adjust nut drive lever 16-governor spring 17-fly weight 18-camshaft,Common rail(共轨)injection system(CR system):All previous injection systems have one disadvantage in common Fig.2-30:the pressure generation and the supply of the injection quantity are not mutually independent.The result is that the injection pressure increases with the engine speed and also increases during injection(approximately linearly).Consequently,smaller injection quantities are injected with low pressure.The peak pressure is almost twice as high as the average injection pressure,which is responsible for the quality of the fuel swirl in the combustion chamber.,前述所有的喷射系统都有一个共同的缺点（图2-30）：油压的产生和喷射的油量不是相互独立的，这样喷油压力随转速而增加，在喷油期间几乎会呈线性增加。因此，少量柴油会以低压喷射。最高喷油压力几乎是平均喷油压力的两倍，这会影响燃烧室内柴油涡漩质量。,Common rail(共轨)injection system:A pressure accumulator is supplied with fuel by a high-pressure pump(Common Rail).The pressure in the common rail is measured with a pressure sensor and settled to a constant value by a pressure-control valve in the high-pressure pump.Depending on the requirements of combustion,the pressure in the rail can be maintained,largely independent of the engine speed,at a constant value in the range between 15 140MPa.,高压油泵（共轨管）向压力存储器供油。压力传感器测量共轨管的压力，高压油泵的油压控制阀将压力控制为一个常数。根据燃烧的要求，共轨管内的油压维持在15140MPa范围内的一个固定值，这基本上与发动机转速无关。,Layout of CRDI system,Review 4:Whats the purpose of the turbocharger and medialcooler in a diesel engine?,More fuel can be supplied to the larger air mass and the engine power is increased.,Diesel engines of Cummins,4CT6BT6BTA6BTAA,4缸C系列增压柴油机6缸B系列增压柴油机6缸B系列增压水对空中冷柴油机6缸B系列增压空对空中冷柴油机,turbo charger（涡轮增压器）system:At exhaust-gas turbo-charging,the exhaust-gas energy which would have been lost is used to drive a turbine.This turbine drives a compressor which aspirates the combustion air and supplies it pre-compressed to the engine.In this way,more fuel can be supplied to the larger air mass and the engine power is increased.A positive effect is also exerted on the combustion process.,在废气涡轮增压中，原本要丧失的废气能量用来驱动涡轮，涡轮驱动压缩机，压缩机吸入助燃空气，预压缩后送给发动机。这样，空气量多，供油也多，发动机功率就会增加，对燃烧过程也会带来积极影响。,turbocharge,SDI=Suction Direct Injection 自然吸气直接喷射TDI=Turbo Direct Injection 涡轮增压直接喷射CRDI=Common Rail Direct Injection 电控共轨直接喷射,