Injectors — Diesel fuel atomization (Focus Turnier 1)

The injectors are the final link in the fuel injection system of a diesel engine. They spray the fuel under high pressure into the combustion chambers. In order to minimise combustion noise and to somewhat curb the explosion-like rise in cylinder pressure, the injectors in the Focus are equipped with two springs. Part of the first spring is designed so that the injector needle is slightly raised in its seat at around 1050 bar. As a result, a small amount of fuel enters the combustion chamber and ignites.

The pilot injection provides a gentle increase in combustion pressure, as it functions somewhat as a wick for the main injection, which occurs at approximately 1,100 bar. The injector needle is now fully lifted in its seat and forces the main quantity of fuel through the five nozzle holes from the injection system into the piston crown recess. The air vortex, intensified by the pilot combustion, entrains fresh fuel particles and forms an almost homogeneous and easily ignited diesel fuel-air mixture.



The high spring tension acting on the injector needles prevents combustion pressure from backfiring into the fuel system. Since not all the fuel is ever injected, excess fuel returns - as mentioned at the beginning - via the fuel return line to the fuel tank. The nominal time between the start of injection and the moment of ignition is 0.002 s. It is clear that even the slightest fault, such as a scored injector needle, throws the physically balanced combustion process out of balance. Unmistakable and audible signs of a diesel engine out of balance are loss of power, black smoke or a loud knocking noise (even with warm engines).

[The full article is on the online resource fordbook.ru]