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Direct Injection

It is already a lot of energy that the system of mixture formation provides. This is why the enormous injection pressures are also withdrawn in the operating conditions with little effect of that. The inlet air provides the necessary spin around the cylinder axis. Since the piston reaches TDC beforehand, a 'crushing' of the air and thus a further unresting heart is possible by coming very close towards the cylinder head.

Above is shown a large piston. The smaller it is, the more pronounced is usually its trough. If you look at the tip of a modern injector, the injection holes of just over 0.1 mm can barely be seen without magnifying glass. The density of the beam decreases with the distance from the nozzle, but not necessarily continuously. Cavitation within the jet can help to avoid a too much fuel at the same place and thus coking.

At the edges of the injection beam, the difference in velocity between the beam and the environment produces an even better atomization. Air from the environment is also sucked into the injection jet. Together with the absorption of heat, very favorable conditions arise for a combustion which has already begun at the edges of the injection jet a time ago.

A major drawback of the diesel process is the fact that injection and ignition must occur simultaneously. Therefore, there is less time compared to, for example, a direct injecting gasoline engine. By the excess of pressure and heat, the combustion takes place very quickly, without regard for what a local mixing ratio is present. This also has implications for engine-out emissions. 06/17