发动机部分1.ppt

Plunger:柱塞，衔铁 喷嘴：spray tip, spray nozzle * 球阀式与轴针式喷油器的主要区别：在于阀针的结构。 球阀式喷油器的阀针是由钢球、导杆和衔铁用激光束焊接成整体制成的，其质量只有普通轴针式针阀的一半。为了保证燃油密封，轴针式针阀必须有较长的导向杆。 而球阀具有自动定心作用，无须较长的导向杆，因此，球阀式的阀针质量轻，且具有较高的燃油密封能力，明显优于针阀式。 片阀式喷油器的结构特点是具有质量轻的阀片和孔式阀座 一般对喷油器有如下要求： 1．有良好的流量特性，喷射范围要大既能满足发动机最大功率时的供油量需要，又能供给怠速时很小的油量； 2．具有良好的雾化和适当的喷雾形状，以利于怠速稳定性、冷起动性的提高和排气污染的降低； 3．具有良好的抗污物堵塞能力； 4．耐久性好。 6）冷启动喷油器 Synopsis * 火焰温度--Flame temperature. 输出功率—Output Power; 油耗率--Fuel consumption rate Air–fuel ratio (AFR) is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich. AFR is an important measure for anti-pollution and performance-tuning reasons. The lower the excess air, the richer the flame * A stoichiometric mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air–fuel mixture is approximately 13:1 but E.P.A. regulations raised the ratio to 14:1 to allow the use of catalytic converters i.e. for every one gram of fuel, 14.7 grams of air are required (the fuel oxydation reaction is: 25/2 O2 + C8H18 - 8 CO2 + 9 H2O). Any mixture less than 14.7 to 1 is considered to be a rich mixture; any more than 14.7 to 1 is a lean mixture– given perfect (ideal) test fuel (gasoline consisting of solely n-heptane and iso-octane). * 理论空燃比—Stoichiometric(Theoretical) Air-Fuel Ratio HC（Unburned Hydrocarbons): are particles, usually vapors, of gasoline that have not been burned during combustion. They are present in the exhaust and in crankcase vapors. Any raw gas that evaporates from the fuel system is classed as HC. CO（Carbon monoxide) is poisonous chemical compound of carbon and oxygen. It forms in the engine when there is not enough oxygen to combine with the carbon during combustion. When