3.1 Fuel Injection Rate Control [1] Main Injection Same as conventional fuel injection. [2] Pilot Injection Pilot injection is the injection of a small amount of fuel prior to the main injection. While the adoption of higher pressure fuel injection is associated with an increase in the injection rate, the lag (injection lag) that occurs from the time fuel is in- jected until combustion starts cannot be reduced be- low a certain value. As a result, the quantity of fuel injected before ignition increases, resulting in explosive combustion together with ignition, and an increase in the amount of NOx and noise.
Therefore, by providing a pilot injection, the initial injection rate is kept to the minimum required level dampening, the explosive first-period com- bustion and reducing NOx emissions. Pilot injection Main injection Q000110E TDC Combustion process Delta injection Small injection amount prior to ignition High injection rate Pilot injection Injection rate Improvement Large pre-mixture combustion (NOx, noise) Small pre-mixture combustion Heat generation rate Ignition delay [3] Split Injection When the rotation is low at starting time, a small amount of fuel is injected several times prior to main injection. Q000111E Split injection 18 Q000112E