燃油喷射系统的组成.PPTVIP

chapter 4 燃油喷射与燃烧 * 4-1 * 【 所有开式燃烧室柴油机均采用多孔喷油器。多孔喷油器有不同的形式，如冷却式、非冷却式，弹簧上置式、弹簧下置式等。当代船用二冲程柴油机使用了非冷却式喷油器。如MAN-BW MC型和Sulzer RTA型这两种机型柴油机使用的喷油器，在具体结构上有所不同，但共同的特点是：当该缸不喷射期间，使燃油系统中的燃油经喷油泵进入喷油器本体内循环冷却，最后〖排至日用油柜〗【流回加压回油柜】。当该缸喷射期间，高压的燃油 首先使燃油循环回路中断，然后高压燃油进入针阀的油腔内，待达到启阀压力时针阀开启进行喷油。喷油结束，油压降低针阀落座后，当油压降低至某规定值，上述燃油循环回路重新接通，喷油器本体的燃油循环重新恢复。由此，此种结构不但省略了单独的冷却系统，而且此种燃油循环在柴油机备车期间可对喷油器进行预热，在运转期间对喷油器冷却并兼有驱气作用。 补图5-7所示是MAN-BW柴油机使用的一种非冷却多孔式喷油器。 喷油器由喷油器体2和喷油器头10组成。针阀偶件3和压力弹簧4及止回阀6装在喷油器体内。各部件用锁紧螺母9紧固在一起，止回阀由阀体5、滑阀6、止推座7和滑阀弹簧8组成。燃油由喷油器顶部进入。当燃油压力小于2MPa时，止回阀关闭，即其滑阀6封闭燃油下行通道，滑阀顶部将止推座7的旁通孔开启，燃油经此旁通孔在喷油器体内循环后排出。当喷油期间油压大于2MPa时，止回阀开启，旁通孔关闭，燃油向下进入针阀3的油腔内。在燃油压力达到启阀压力时，针阀开启燃油喷入气缸。喷油器启阀压力由弹簧4预紧力即有关零件尺寸预先确定，使用中不能进行调节。】 chapter 4 燃油喷射与燃烧 * 4-1 * The split pump technology, firstly introduced on the W64, offers unique advantages in terms of operating flexibility, mechanical strength and cost effectiveness. Injection timing can be freely adjusted independently of the injected quantity. Tuning of the injection parameters according to the engine’s operational conditions improves engine performance and reduces exhaust emissions. Smaller closed-type pump elements reduce mechanical stresses and increase reliability. Reduced loads on rollers, tappets and cams improve pump driving reliability. The pump elements are adapted from high-volume production of smaller engines. The high-pressure system has been designed and endurance tested at 2000 bar. The injection pressure is around 1400 bar, which gives an outstanding safety margin. No lubricating oil is required for the pump element since the plunger has a wear- resistant, low-friction coating. Thanks to the profiled plunger geometry the clearance between the plunger and the barrel is kept small, thereby allowing only a minimum of oil to pass down the plunger. This small leakage is collected and returned to the fuel system. Any likelihood of the fuel mixing with the lube oil is eliminated. Both the nozzle and nozzle holders are made of high-grade hardened steel