k It has been said that pilot injection can be used
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to reduce diesel knock. What pilot injection and how does it enable 'esel knock to be controlled? Is it fitted any diesel engines in production?
kDiesel knock results from combustion
lag at the start of injection. Heat is .tracted from the surrounding air by the ilid droplets of fuel during the first phase injection and initially there is insufficient rat to cause combustion, which is delayed MI a part of the injected charge has been iporized. By this time an appreciable nount of fuel has been injected and burning the fuel is uncontrolled. Combustion of e remainder of the fuel charge is con)1Ied, in that it burns as it leaves the lector nozzle.
Diesel knock is produced by the uncon)Iled burning of the first part of the charge. of which is ignited by the heat of comession, following partial or complete porization, to produce a pressure wave at impacts on the surface of the cornistion chamber.
A pilot injection system injects a minimal nount of fuel at the start of injection which adily vaporizes and burns immediately leaves the nozzle or after a very short :lay. The remainder of the fuel is injected tring the second phase after combustion Is started and there is an ample amount heat to ignite the fuel. When a diesel th a conventional injection system is ierating at higher speeds there is normally ough heat in the compressed air to burn e fuel as it is injected.
So far as is known, no diesel engine in