Diesel oil engine

Abstract

The diesel engine 1 is provided with a fuel injection device M to conduct main injection Js of high-pressure fuel into the combustion chamber 7 near a compression top dead center, and conduct the preliminary injection Js before the main injection, and a controller 27 to control the fuel injection device M corresponding to the operation condition. The controller 27 controls the injection so as to conduct the preliminary injection before the opening position tintop of a suction valve in a latter part of the exhaust stroke. In the diesel engine in which the preliminary injection is made in an exhaust stroke range without the immediate ignition by obtaining a sufficient premixed time so that premixed combustion is promoted, and main injection fuel is quickly vaporized and burned in a combustion chamber raised in temperature so as to enable both the reductions in a formation amount of NOx and discharge of a smoke (PM).

Description

technical field

[0001] The invention relates to a diesel engine with pre-injection before main injection, in particular to a diesel engine capable of reducing black smoke emission while suppressing NOx generation. Background technique

[0002] In a diesel engine, in order to reduce NOx contained in exhaust gas and noise during combustion, a conventional method is to delay fuel injection timing. However, if the timing of fuel injection is delayed in this way, the amount of black smoke emission will increase. Therefore, the emission of black smoke is reduced by adopting the method of improving fuel atomization after implementing high-pressure injection. However, in this case, as the combustion temperature rises, the NOx emissions will also increase.

[0003] As mentioned above, for diesel engines, the relationship between suppressing the production of NOx and reducing the emission of black smoke is a mutually restrictive relationship, and it is difficult to improve both at t...

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